Pacey Performance Podcast REVIEW- Episode 380 Alistair & Tom Part 2

This blog is a review of the Pacey Performance Podcast Episode 380 – Alistair McBurnie & Tom Dos’Santos

 

Alistair McBurnie

 

Alistair is a sports science analyst for Manchester United’s first team, having worked his way up from coaching at academy level.

 

Twitter

 

Tom Dos’Santo

 

Tom is a lecturer at Manchester Metropolitan University, where he teaches strength conditioning and sports biomechanics. Previously, he’s worked at the University of Salford, and England Northwest and Manchester Thunder netball squads.

 

Twitter

 

? Listen to the full episode here

 

Discussion topics:

 

Do we think the boot worn sensors are going to be the next thing to integrate within performance departments?

 

”@Alastair: I think so. I think it’s just the next level really, isn’t it? We talk about whole body loading and evaluating the key performance metrics we currently have which might include total distance, high speed running, sprinting distance, accelerations, and decelerations. I’m not telling you things that are reinventing the wheel there. I think everyone are using them as the key monitoring metrics, in particular in football.

 

 

Individualising Training

 

We want to make athletes better at performing these high intensity actions and to just have an insight into the volume. This player performs, you know, 200 metres of sprinting distance in a game. That’s great from a volume perspective and programming of weekly and monthly training volumes.

 

But in terms of how are we actually programming how are they achieving that movement (volume) and information about the movement strategies and the special temporal variables that you get from these kind of technologies I think will give us more insights into the specific drills that can target them because if we’re looking at horizontal deceleration and we uncover that a player’s ground contact time may be a bit too elongated, we’re then stripping that back and going, right, what can we do in the gym to make sure that we’re actually increasing elements that are going to improve ground contact time or stiffness if you’ll like?

 

 

So I think when we get to a point where we can move a lot of the stuff that is typically done in a lab and moving it to the field and almost ”testing without testing” players within their athletic development training programs these technologies are able to pick up every single action that they’re doing. So it becomes a point where we don’t have to worry about getting athletes in for a testing battery. It can almost be done as part of the day-to-day practices, as part of the warm-ups, etc.”

 

In terms of developing the qualities needed for good deceleration ability in the gym, when people look towards that, what should people be focusing on based on what we’ve just spoken about for the last 45 minutes?

 

”@Tom: So I think it’ll be very similar to change of direction, especially when we think about that angle-velocity trade off again. So we think the shallow change of directions, being more velocity dominant, more concentric and reactive strength dominant, whereas particularly anything 60 degrees, 90 degrees and above are probably a bit more of eccentric strength training focused.

 

So in terms of physically preparing athletes, we like to think about specific musculature and segments that we want to target. And then maybe think about the underlying physical qualities and strength qualities. Let’s discuss the musculature first, and then some particular physical qualities and training methods.  It should be a mixed multi-component and a multi-segmental model and It’s not just one specific area, or one training modality that is going to bulletproof our athletes.

 

Trunk Control

 

And I think the kind of the training recommendations that myself and Alistair will go through are probably applicable not only for deceleration, but change of direction, curvi-linear speeds, accelerations and high speed running. So trunk control, if we work our way down, trunk control is going to be a massive. Trunk contains approximately half of the body’s mass and that needs to be supported typically on one limb where we’re doing these deceleration and change of direction actions. And we need good control in the frontal plane and the sagittal plane.

 

So there’s a lot of evidence showing that from a change of direction perspective anyway, lateral trunk flexion is going to increase our knee valgus moments because we get laterally directed ground reaction force vector that increases the moment arm and subsequently increases loading.  So frontal plane trunk control is going to be massive.

 

Technique modification training so basically good cuing and good coaches are telling athletes to adopt a bit more of a neutral trunk posture, and make sure they are in their correct alignment. I know some people have used medicine balls to try and reinforce optimal trunk alignment. I think Enda King and the Sport Surgery Clinic have shown it to be quite effective.

 

Our dynamic trunk stability exercises and balance training has also been shown to be quite effective at improving frontal plane and transverse plane trunk control. In terms of correcting sagittal plane and avoiding anterior trunk displacement, probably in the opposing muscle groups and the posterior aspect especially erector spinae and glute max exercises target that trunk control and reinforce that bracing and again, instructing our athletes to try and avoid excessive forward trunk lean when we’re decelerating and performing these change of direction actions.

 

And there’s also evidence showing these deficits in trunk control can increase ACL injury risk and have been prospectively shown to increase ACL injury risk. So with that multi segmental model focusing on correcting that anterior pelvic tilt, getting that dynamic trunk stability in the sagittal and frontal plane seems to be key.

 

Hip Complex

 

Then, because from the biomechanical aspect during these decels and change of directions we create these large hip flexor moments and more externally applied knee flexor and hip flexor moments. So they need to be supported and counteracted with an internal hip extensor and knee extensor. So again, the musculature around the glutes, and external hip rotator strengthening is going to be key to tolerate those large hip flexor moments, trying to resist that change in hip flexion essentially. But also it’s going to be key in terms of frontal plane control particularly the femur. So again, there’s evidence showing that a knee valgus can increase knee valgus loading, like a two degree difference can increase the torque by around about 40 Newton metres.

 

 

And by having high levels of glute activation it can resist and oppose and support that potential knee valgus loading and preventing that knee valgus position. So that would be key from that perspective, but it’s also key for facilitating braking.

 

Anterior Aspect

 

If we start going onto the anterior aspect, so the quadricep strengthening is going to be key, particularly for those eccentric muscle actions and to support those large external knee flexor moments. So we’re getting internal knee extensor moment. So we have high levels of quadricep activation, but we have this kind of performance-injury trade-off. So we need the quadriceps for the braking aspect and we need them for the propulsive aspect if we want to go and re-accelerate and perform a change the direction.

 

However, if we don’t have high levels of co-activation of the hamstrings, this can increase our anterior tibial shear. So again, I’m going to focus on ACL injuries because I love ACL injuries, but it’s kind of like a multi-planar mechanism. So we get our anterior tibial shear, which can result in this anterior tibial translation of the tibia relative to the femur. That seems to be one of the primary contributors of ACL loading.

 

If we get these aggressive quadricep activation at these extended knee postures, typically within 0-40 degrees where the quadriceps insert, we can get this anterior tibial translation. So although we do need, I’m not saying we avoid high levels of quadricep activation, we do need it, but we need to make sure we get high levels of co-activation of the hamstrings as well. Hamstrings are bi-articular, originating in the pelvis and insert into aspects of the tibia and the fibular, but their role is to prevent that anterior tibial translation to try and oppose and create a posterior shear force. And again, there’s lots of evidence showing that having weaker hamstrings and fatigued hamstrings can increase ACL loading, and there are some musculoskeletal modeling showing that.

 

So although we do need high levels of quadricep activation, we need to make sure we get the high levels of co-activation of the hamstrings as well. And that could be a whole range of different fast eccentric velocity exercises, slow velocity exercises, isometric, eccentric, and even potentially some concentric strengthening exercises as well.

 

Lower Limb

 

If we move down the limbs, we’ve focused on the knee and the hip there and the trunk. There is a whole debate around the gastrocnemius, but the gastrocnemius is a kind of antagonist to the ACL and can increase ACL loading. There’s some evidence showing that we need to increase soleus activation, particularly around the ankle, the ankle acts like a kind of dampener and a shock absorber for deceleration and our change directions. So although we need that quadriceps, some people argue that soleus activation is key.

 

How you go about isolating soleus without getting gastrocnemius would be quite difficult. I probably don’t have the answers there. Probably some more intelligent people might be able to answer that. And then we also have a kind of like our intrinsic foot stabilizer muscles and that kind of perennial muscles as well to try and prevent those excessive inversion angle of velocities because lateral ankle sprains are a common injury mechanism during these decel and change direction actions. So specific exercises to target ankle stability and foot stability.

 

So they’re the key muscles and musculature that we want to target. I’m not saying that this is the right or only way to go about it. It’s a whole different range of methods. My whole philosophy about transfer of training is focused on the adaptation that we’re trying to elicit. I’m not going to say we must do Olympic lifts or must do this as long as you’ve got a rationale behind your exercise and we’re trying to elicit some sort of musculoskeletal or mechanical biological adaptation, that’s key.

 

Physical Robustness

 

So in terms of reducing risk, we’re trying to reduce those high risk deficits that are linked to the potential to generate multiple planer knee joint loads. So any frontal plane deficits, such as knee valgus, tibia rotation, lateral and frontal plane trunk control. So again, this is quite a performance-injury trade off. We need athletes to generate high impact ground reaction forces, but they need to be able to tolerate them. So having athletes physically robust enough, there seems to be this emphasis now and shifting away from kind of injury prevention, but more focus on physical robustness to tolerate these loads.

 

So again, to tolerate these potentially hazardous knee joint loads in particular, is increase muscular support round about the knee span and non knee spanning muscles around glutes, around about the hip, around the knee as well, the quadriceps and the hamstrings and the lower limb as well and they can support in some of that loading. By mechanically loading these structures, we are stimulating some musculoskeletal adaptations to hopefully strengthen those tissues, so they’re more robust to tolerate them.

 

And what Alistair alluded to before in terms of reducing injury risk, is that careful monitoring and sequencing in periodisation of these high impact activities. So getting into these advancements in technology, we’re monitoring a number of accels and high speed running. There seems to be this sweet spot, not too much, not too little in terms of high speed running, I think was it Malone who identified maybe six to seven sprints of 95% and above. We just don’t know from a change of direction and deceleration perspective, but we encourage practitioners to monitor hopefully these proxies of ACL and lower limb loading, and probably try to avoid these rapid spikes, maybe 10 to 20% on a week to week.

 

And then you’ve got the development of the kind of perceptual cognitive abilities as well. So if we can start identifying some of these cues a bit earlier, so we can make some anticipatory posture adjustments and get these high levels of pre-activation. This again should hopefully dissipate some of the loads. Probably a debatable area, whether it’s in strength and conditioning coaches’ job to work on perceptual cognitive speed, I would encourage people to work with a motor skill expert, but I suppose it comes down to working with a skills coach, motor skills experts to try and identify working on perceptual cognitive speed. So we can identify these cues earlier, put us in a position to make these anticipatory posture adjustments earlier. Give us the physical affordances to hopefully adopt these safer, and more mechanically robust strategies to reduce loading and optimize performance.

 

Multi-Component Training Model

 

Damien Harper’s has been calling it the dynamic braking performance framework we are a big believer of a multi-component model. So not a one size fits all, but including some trunk stabilization, balance, plyometric training is a very good transferable exercise for not only for improving performance, but improving lower limb control and neuromuscular activity patterns, but also get some eccentric strength development in the weight room. I encourage a multitude of different exercises that focus on all aspects of the force velocity curve. So having some fast eccentric velocity exercises, whether that’s through plyometric training, maybe some ISO inertial training or some kind of more coordination overload. Some more slower eccentric velocity exercises, whether that’s more AEL, (accentuated eccentrics loading), or I don’t know, maybe some Nordic curls, for example, or just increasing time under a tension and tempo training.

 

I probably encourage people to read the work of Tim Sycamore, he did a two part review. Not my area of expertise, but I know you’ve interviewed Alex Natera and Daniel Lum, big emphasis on isometric training at the moment, particularly if we could try and mimic some of the postures and deceleration and change of direction. However, we probably do need to target particularly that kind of triple flexion position in a range of different postures, because the greater the angle of change direction, you typically go to greater range of hip and knee flexion as well. So you probably need maybe a 140 degree angle, maybe a 120 degree and a, maybe an 90 degree angle with different postures. And I know there are advocates of yielding and pushing isometrics. I don’t know too much about that.

 

 

I think you can elicit some very good tendon adaptations and get something hopefully quite non-fatiguing positive tissue adaptations as well as those sports specific postures, whether it’s unilateral or split position. And then the reactive strength qualities that we could target in the weight room, our typical ballistic training, our Olympic lifts, not only during the propulsive phase, but whenever we decelerate the barbell, not getting into a debate whether we need to catch or just do the pull of variations. However, if you just do the pull of variations, arguably you get a nice fast eccentric loading, when we decelerate the bar, so that could be a really good method as well. And just your generic tissue conditioning and your general resistance training your back squats, deadlifts targeting those key segments that are target before.

 

And there’s finally, and I’ve talked for ages about this focus on movement quality. Essentially movement is a skill. These injuries occur due to some sort of biomechanical limitation that’s increased load into that specific joint or structure. So trying to optimize the technical characteristics and maximize performance, but also potentially mitigate injury risk. There is a performance-injury trade-off associated with some of the techniques, but we’ve shown that in as little as six weeks, we can modify athlete’s technique during cutting and turning by giving some externally directed verbal cues and introducing these in the field, as part of a field based warm-up.  I don’t buy that athletes and coach said they haven’t got time to throw this type of training into their training programs  before every technical tactical session.

 

From a deceleration training perspective, I do think we do need some interventions looking at enforced stopping as a fast eccentric velocity training method, but also as a strategy to reinforce these optimal mechanics. If we want our athletes to move well, we need to practice the skill of decelerating and change of direction in pre-planned environments, but we can get onto later if you want.”

 

”@Alastair:  I think you emphasized a great deal that we really believe that the fast eccentric loading component of specific horizontal decelerations in the field is a really key and potentially potent stimulus. And I think we can talk about the, the gym based strategies, which obviously should work in harmony with the field based athletic development strategies.

 

So I think you can’t just decide, right, I’m going to focus on all these eccentric training methods in the gym, and that will create super robust resilient athletes. I think you also need to make sure that they are specifically applying all these elements in field based drills. We’ve got a library of different drill examples that we can provide obviously targeting in multiple planes as well, because we’re not just decelerating in the sagittal plane, change of direction maneuvers occur in the sagittal plane, the frontal plane and the transverse plane.

 

You’ve got this point where it’s almost a harmony of the gym based programming and the field based programming to get the adaptations that you want. Chris Bellon talks about using the short to long approach of acceleration development with the pioneer of that is being Charlie Francis, but talking about seamless sequential integration, whereby we are developing shorter acceleration distances first and foremost in the training cycle, and working a lot alongside that or the gym based methods that actually provide the foundation for the subsequent phase.

 

So as an athlete is then starting to be exposed to greater acceleration distances, they have the prerequisite physical strength and power qualities to almost harness that to optimum effect. And I think you can see how that would theoretically apply to horizontal deceleration training. So if we were to develop the foundational eccentric strength qualities alongside the pitch based stuff which might be at this point a bit more of a technical focus, making sure that we’re getting the right positions in both the sagittal and frontal plane. So we start with methods such as flywheel training or tempo eccentric training, but then developing those foundational eccentric strength qualities for the subsequent phase to which then you might actually open up the distances.

 

We use deceleration runways a lot, which is where you can almost increase the drill distance or the approach velocity before actually making a more intense, horizontal deceleration. And by having the prerequisite eccentric strength qualities that you’ve developed in the previous phase, you should be in a better position to tolerate the deceleration demands there. So I think it’s always about using both gym-based and field-based athletic development exercises to create these athletes or to promote these characteristics that we want to see from both performance and injury risk perspective.”

 

”@Tom: Sorry Alistair, just one point. I suppose it comes down to your point about the monitoring. Like we said before, we can easily integrate these kind of field-based runways and decelerations into our field-based training. We don’t know too much about the optimal dosages. So we encourage a conservative approach, with careful periodisation. I probably would say maybe only theoretically maybe 100 to 200 metres of enforced stopping probably only that’s needed because we need to be monitoring the technical tactical base sessions as well. We don’t want to overexpose athletes, but I think we certainly need more research in that area about the optimal dosages and whether that differentiates between athletes, whether they’ve got high levels of physical capacity. I’d imagine athletes with great physical capacities are able to tolerate greater dosages of this enforced deceleration training, but a kind of a careful conservative approach is what we’d recommend.

 

But if you’re not monitoring, you’re just guessing, so that’s why we would come back to if you’re at least getting some monitoring of the frequency and potential deceleration distances, in addition to whether you are prescribing five or 10 metre decelerations, I think that’s a really big thing to think about.

 

I would also just say going back onto what we know about horizontal decelerations and the unique, physiological and biomechanical characteristics that might separate them from other potential multidirectional speed elements that you’ll be exposing your athletes to. So almost looking at it from a macroscopic perspective and going right, what training sessions are we carrying out this week, the next week, over six weeks and going, right?

 

Can we sequence these in different ways? Because we know that the recovery timelines of these more biomechanically focused elements with eccentric loading might be quite different to what an acceleration focused session might be.  So almost looking at it over a six week cycle and actually sequencing your accelerations, your high speed running, which are maybe more of a concentric focus with less muscle damage than a horizontal deceleration would impart. And actually making sure that you’re sequencing them differently rather than just going right, I’m going to deload on week five.  You actually might want to look into it and go, I’m going to deload these accelerations and high speed running in week four, and then pick it back up in week six, and actually you might want to give a bit more time for that adaptation to happen with the horizontal decelerations. In that way we can actually harmonise and sequence different variables at different times.  You might be deloading and not targeting a specific multi-directional speed quality in one week but it doesn’t mean that you can’t target another element.”

 

 

Top 5 Take Away Points:

 

  1. Boot worn sensors – might be the next development to measure inter-limb differences
  2. There are a number of muscles that need to be conditioning for deceleration including trunk, hip complex, quadriceps and hamstrings and calves.
  3.  Training for deceleration needs to be a multi-factorial approach including an emphasis on eccentric training, as well as isometric, reactive strength and technique/movement quality.
  4.  Integration – the gym based strategies, should work in harmony with the field based athletic development strategies.
  5.  More research is required – we don’t know the optimal dose of enforced stopping but conservatively we suggest no more than 100-200m and this work should be considered to have different timelines of adaptation and recoverability due to more biomechanical loading (than acceleration).

 

Want more info on the stuff we have spoken about?

 

Science of Multi-Directional Speed

 

You may also like from PPP:

 

Episode 372 Jeremy Sheppard & Dana Agar Newman

Episode 367 Gareth Sandford

Episode 362 Matt Van Dyke

Episode 361 John Wagle

Episode 359 Damien Harper

Episode 348 Keith Barr

Episode 331 Danny Lum

Episode 298 PJ Vazel

Episode 297 Cam Jose

Episode 295 Jonas Dodoo

Episode 292 Loren Landow

Episode 286 Stu McMillan

Episode 272 Hakan Anderrson

Episode 227, 55 JB Morin

Episode 217, 51 Derek Evely

Episode 212 Boo Schexnayder

Episode 207, 3 Mike Young

Episode 204, 64 James Wild

Episode 192 Sprint Masterclass

Episode 183 Derek Hansen

Episode 175 Jason Hettler

Episode 87 Dan Pfaff

Episode 55 Jonas Dodoo

Episode 15 Carl Valle

 

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Pacey Performance Podcast REVIEW- Episode 380 Alistair McBurnie & Tom Dos’Santos

This blog is a review of the Pacey Performance Podcast Episode 380 – Alistair McBurnie & Tom Dos’Santos

 

Alistair McBurnie

 

Alistair is a sports science analyst for Manchester United’s first team, having worked his way up from coaching at academy level.

 

Twitter

 

Tom Dos’Santo

 

Tom is a lecturer at Manchester Metropolitan University, where he teaches strength conditioning and sports biomechanics. Previously, he’s worked at the University of Salford, and England Northwest and Manchester Thunder netball squads.

 

Twitter

 

? Listen to the full episode here

 

Discussion topics:

 

Why is it so important that we do focus on both performance and injury risk and what’s your thoughts on the importance of training deceleration for both of those aspects?

 

”@Alastair: I think when we talk about deceleration we’re either referring to it as an action immediately preceding a sprint or the penultimate steps before a change of direction maneuver. So it’s almost like a prerequisite for a lot of actions or high intensity actions that are going on in match play across all team sports.

 

Performance Perspective

 

And I think from a performance perspective, a lot of Tom’s works looked into the penultimate steps preceding a change of direction maneuver. And we know that within that effective deceleration underpins effective change of direction performance. And that is simply because in order to reduce horizontal momentum and reduce the  requirements of the final change of direction foot plant, as a braking requirement, we almost want that final change of direction foot plant to be more of a propulsive element to which that deceleration and application of high deceleration braking force underpins that.

 

So from a performance perspective, I think being able to slam on the brakes both quickly and effectively will be conducive to change of direction performance, but also being able to react to situations in game play.  When players are trying to evade opponents, being able to create that separation from the opponent and exploiting the space is really important.

 

Injury Risk

 

From a more injury risk side of things, there’s a lot of things going on in terms of what are the implications from both a biomechanical and physiological perspective. We touched on this a lot in our recent review that was published in Sports Medicine. But essentially what we’re trying to discuss with respect to horizontal deceleration is that they are unique actions in comparison to other high intensity key performance indicators. We talk about acceleration and high speed running, being a very important thing to both expose athletes to, and prepare them for and monitor during the weekly training cycle.

 

But I think deceleration needs to have the same focus. And from a biomechanical perspective, you’ll see that, and this is the work done by Damian Harper. He likes to see a higher impact peak and loading rate from a deceleration, so that higher spike in ground reaction force you’ll typically see versus an acceleration which can be down to the rapidly imposed nature of horizontal decelerations, but also the movement strategy performed as well. So that heel foot contact and that stiffness in comparison to a more mid to forefoot striking strategy for your acceleration.

 

 

Then from a more physiological perspective, horizontal deceleration obviously have that really strong eccentric element to them which can impart muscle damage. And this is going to have acute implications as well as chronic implications because we also know that the high eccentric force requirements of horizontal decelerations can  disrupt the structural integrity of the muscle cells.  Over the course of a long competitive season, under fatigue conditions, that may actually exceed the muscles’ capacity to tolerate those high eccentric loads. And it could cause these acute muscle strain injuries we see.

 

But then probably from more a chronic perspective, we’re again talking about these team sport athletes who are required to repeat these high intensity performance over multiple matches, high fixture densities and repeating these high intensity actions may cause a sub maximal repetitive loading consequence, which may surpass the remodeling rate of the biological tissue because of the limited recovery timelines.

 

So in essence, we’ve got this athlete who if they aren’t physically prepared enough or don’t have the physical capacity to tolerate the high braking demands, as well as the technical proficiency to dissipate or attenuate the braking loads, coupled with the fact that they are required to repeat these high intensity actions multiple times within a training week or within a cycle, they may be susceptible to injury due to the elements that we’ve just discussed in terms of the biomechanics and physiology of decelerations.

 

So we want to understand that horizontal decelerations have these unique elements, which if we can understand and highlight, we can sequence them appropriately within a training cycle and hopefully reduce the relative risk of injury that athletes may be susceptible to, but also improve the performance as well, which I’m sure Tom can talk about a little bit more with his work.”

 

”@Tom:  As Alistair was stating before we can treat deceleration from a performance aspect from two perspectives; treating it as an isolated agility action. So if we consider Warren Young or Shepherd Young’s definition from 2006, a rapid whole body movement with a change of direction or velocity in response to stimulus. So deceleration in its own right is its own unique agility action, as Alistair was saying before.

 

Performance Perspective

 

We typically see it with our wingers potentially in rugby, American football, even soccer, doing those enforced decelerations from an attacking perspective to try and create that separation in order to maybe re-accelerate again or catch a ball or receive a pass.

 

Then from a change direction perspective, we’ve discussed something known as the kind of angle-velocity trade off. So typically as the angle increases, we need to reduce our horizontal momentum in order to perform that intended angle or change of direction. And typically, as angle increases our momentum muscle reduce and normally the ground contact time will increase in proportion to that angle.

 

Based on the biomechanical literature, it seems to be that in terms of the preliminary deceleration, there’s probably a minimal requirement to decelerate prior to, or for change of directions around about 45 degrees and below from a pre-planned perspective. Obviously there’ll be scenarios in multi-directional speed sports, where if you are having to perform a shallow change of direction where we only need to slam on the brake slightly for an acute angle change of direction, but typically in terms of the foot contact the second to last foot contact that we’re interested in (penultimate step), it seems to be 60 degrees and above, and we’ve even shown some evidence that even the anti-penultimate foot contact has a significant role in deceleration.

 

Figure- example of 180 degree cut

 

And again, some of the evidence seems to show that deceleration distances for these sharper change of directions can range from anywhere from about four to seven metres. So it highlights a multi-step nature of change of direction to reduce that momentum in order to deflect our center of mass.

 

So that’s key for performance. You’ve probably seen yourself as a practitioner athletes run too quickly and they can’t perform that intended angle of directional change, which probably affects their ability to deflect the centre of mass and makes them more susceptible to being tackled if it’s a invasion sport where we’re trying to evade our opponents. So it’s kind of like a speed accuracy trade off.

 

Injury Risk

 

Then from the injury risk perspective, deceleration actions are associated with injury inciting events. As Alistair has said before, we can get round about six times body weight of impact ground reaction forces within 50 milliseconds. So my background is ACL injuries. That seems to be the kind of window when these ACL injuries occur, these ACL injuries and other tissue injuries occur when we experience a mechanical load that exceeds its ultimate tensile strength.

 

So that could just be one single catastrophic load, the body’s load, and we can be referring to torques or knee moments in particular, which is just ground action force multiplied by the moment arm. So if you are landing stiffly and have a high impact ground reaction force, we’re potentially going to increase our knee joint loads and that could potentially increase load into the ACL and the other tissues and structures in the knee in particular. And over time if that single loads is high enough, that could result in a rupture, but as Alistair described really well before, potentially there’s this mechanism of a fatigue failure.

 

So we see athletes performing hundreds of decelerations, hundreds of change of directions without getting injured. So why is it that one time they do get injured? Is it because of a fatigue failure mechanism where we gradually get this reduction in structural integrity and the low tolerance of that tissue? If we experience chronic exposure to these sub maximal loads, which gradually weaken the knee ligament or the other tissues and without adequate rest and preparation, that sub maximal load now becomes a load that it can no longer tolerate, which therefore results potentially in a rupture or strain or whatever, the injury mechanism there is potentially there.

 

So they are associated with ACL injuries, other soft tissue injuries, ankle injuries in particular, if we experience some high inversion angular velocities, during decelerations. Jordan Mendiguchia, has been discussing this and another is JB Morin, if you’re talking about anterior pelvic tilt, and although knee injuries seem to be the predominant injuries associated with decels and change of directions, there’s also the potential to generate potentially some hamstring strain injuries as well. Particularly if we get rapid trunk flexion with an extended knee posture which we need when we’re decelerating.

 

And I think they’ve described it really well, particularly with an anterior pelvic tilt with this rapid trunk flexion, we’re going to get a lot of extreme lengthening and loading at the proximal portion of the hamstring. So in addition to knee injury risk from a knee ligament and a quadricep tendon and patellar tendon perspective, we’ve also got to be thinking on the posterior aspect and the proximal portion of our hamstrings as well.”

 

So with the importance of this based on what you’ve both said, let’s talk about monitoring and testing, so maybe come to you Tom, on testing, and then the monitoring side of thing day-to-day, come to you Alistair on that. Is that alright, Tom?

 

Testing

 

”@Tom: Yeah. So I suppose we’ll go from like bronze standard completely field based to the gold standard methods in terms of testing deceleration. So from a basic perspective, I think coaches need to start appreciating, maybe just using the coach’s eye and start evaluating the technical aspect in terms of deceleration and potentially using high speed cameras. We’ve all got smartphones. Generally, they all can record 120 frames per second or above. So there’s nothing to prevent us now from doing some enforced deceleration with athletes filming predominantly from the sagittal plane from the side and observing some of the technical characteristics.

 

Bronze Standard ?

 

If you have got the ability to observe in a frontal plane, we’ve experienced it before at Salford City, some of our players during just a simple linear deceleration task, will display high levels of knee valgus. So from a movement and quality perspective for every task, I know Kinogram is a very popular for acceleration. I think we should be doing the same deceleration from a movement quality perspective.

 

With the simple way of measuring deceleration, we need to be thinking about what the KPIs are, what are our key metrics that indicate an athlete who’s very successful and very competent at deceleration. So probably the key thing that we’re after is time to stop a deceleration or distance to stop. We want athletes to be able to brake very quickly over a short amount of time and over a short distance.

 

So one crude way of doing it is just simply with a tape measure. There have been some research studies that have used a tape measure. Now one way is to run and once they get to the cone and the tape measures, they slam on the brakes. Not the best way of doing it. A lot of athletes will probably adopt a kind of pace strategy or start decelerating prior.

 

The next step I’ll probably recommend is probably again using high speed cameras.  There’s probably two ways of assessing deceleration, which Damien Harper speaks about and I think Phil Graham Smith has done before.  We have decelerating to a predefined point. So maybe that’s 15 or 20 metres, or you sprint to a certain distance and once you reach that marker, then you slam on the brakes. So Damien Harper’s a big advocate for that one. Phil Graham Smith has done the former where you actually decelerate to a predetermined point.

 

So what we could do with our cameras, we could position the camera probably about five to 10 metres away in the sagittal plane from the marker. And what Damien Harper did is he examined the approach velocity from 19 to 20 metres just before they had to slam on the brakes and then using your cameras, you can identify a tracking marker potentially on the pelvis or use the whole body if you wanted to. And then you would measure the distance it’s taken them to decelerate from that marker, past that point. And you could work out the time to stop. So we get a distance to stop and a time to stop.

 

But what we need to factor in is the athlete’s approach velocity as well, because it’s going to be bias towards lower momentum athletes. If you are a larger momentum athlete so heavier and faster, you’re at a disadvantage, because you’re going to require greater braking or net, horizontal braking impulse to decelerate and reduce your momentum.

 

The issue with those tasks is that it does require 2D analysis. So it can be a bit more time consuming and based on some of Damien Harper’s or Phil and Paul Jones’s research, athletes tend to start decelerating before that 20 metre mark. So they were reporting deceleration distances of three to four meters, when in fact they actually started decelerating potentially one to three metres before that point. So that’s something that we need to bear in mind if you are just measuring distance to stop from that predefined point.

 

Silver Standard ?

 

Probably the next step or the best way to go is potentially using like a radar or a laser device. So we have Stalker speed guns. So that’s what Damien Harper’s used. That samples at 47 Hertz, so we get an instantaneous velocity profile for our athletes. I know Paul Jones or Phil Graham Smith have used LabX which I think sample at 100 Hertz, so we get a bit more data. With deceleration we’re interested in meters per second squared and some people are interested in peak deceleration values. However, that only represents one data point and that could just be a freak or random part of data.

 

 

So I know Damien’s a big advocate of measuring average deceleration drawing the deceleration task and he started breaking it down into early and late deceleration. And the beauty with that device is we’re able to identify when they’ve started decelerating. So even if you are putting that 20 metre checkpoint, you can identify if they’re decelerating, maybe two to three metres earlier. And that’s what Damien Harper seems to be finding. Maybe around about the 17 and a half metre marker point, they seem to be putting on the brakes, which is fine as long as you are monitoring. He identifies deceleration distance as the distance from when they’ve achieved peak velocity to going towards that back pedal. So zero meters per second, and then in a negative direction.

 

So we can get those metrics from that. And in terms of the potential metrics that we want to examine, we can get our deceleration distance.  They seem to be our two KPIs that we’re interested in. So getting the distance to stop and time to stop with appreciation of that athlete’s entry velocity. So I don’t think it’s one single metric, we have discussed a possibility of maybe creating a ratio. So take the athlete’s initial entry velocity, and then maybe looking at the ratio of that entry velocity or peak speed and their distance and time to stop.

 

I believe the Ergo Test is another device that’s around about 5,000-10,000 Euros. Stalker speed gun is a bit more affordable, about $2,500 and LabX, I think a bit more difficult to hold of. I believe companies such as Playermaker, which is wearable for the foot, are working on the device potentially to start monitoring it in the field. And then the unique aspect of that is we’ll start to be able to monitor foot to foot and load distribution between left and right limbs to see if there’s any asymmetries.

 

LED React, another company are using radar and they’re creating kind of like a 25 metre radius dome, and they’re potentially working on a deceleration test using that same similar bit of technology.

 

Gold Standard ?

 

Probably the gold standard, but probably very difficult to implement in a field would be 3D motion analysis where we can get that instantaneous assessment of centre of mass velocity, but that requires Qualisys or Vicon, very difficult to implement in the field. Although there are now the advancements in marker-less technology as well and I know Jonas Dodoo has started using Binary sports app where identify the marker, and then they automatically track them. Not too sure on the validity of that approach.

 

But again, a bit more insight into not only just a kind of the instantaneous velocity, but we’ll get a bit more insight into how they’re performing the deceleration, so you can get some insights into some of the spatial temporal characteristics, limb velocities, step length, step frequencies, etc. So that’s a really good, I think there’s a lot of potential there. And I think over the next three to five years, I think marker-less technology will be amazing and probably bridging the gap, getting more insights to practitioners in the field.”

 

From a day-to-day monitoring point of view, Alistair, when it comes to deceleration, what kind of things are you doing? Is it like deceleration count? Is it deceleration intensity using player tracking etc?

 

Monitoring

 

”@Alistair: I think Tom’s alluded to a lot of potential technologies down the line are going to be very useful and give us a lot more insights to assessing and monitoring these actions. But I think based on current technologies (and I think pretty much every top club are using them now) is usually through GPS tracking. It is obviously very useful and it tells you a lot of information in relation to  the volume and also the intensity of whole body movements.

 

I’d like to underline that it is just whole body movement and for us to really understand what’s going on in terms of what is the actual movement strategy of the athlete, we currently won’t get that. We’re able to more deeply analyze supposed centre of mass velocity with these units. But I think even that will take a lot of extra work within the day-to-day practices. So like you said, we’re using count currently. I think it’s over three meters per second squared where we are classifying them as high intensity actions. And that’s the same for accelerations as well.

 

I’d like to highlight that there are differences between the demands of a high intensity acceleration versus a high intensity deceleration, which currently just use the same arbitrary cut off value, whether it’s three metres per second or 2.5 metres per second or whatever. But in actual fact the actual maximum rates of deceleration are much higher than acceleration. We also know about the biomechanical requirements of decelerations versus accelerations being very different. There may be a bit more of a metabolic cost to accelerations versus greater biomechanical loading of decelerations.

 

So I think we probably need to look into it a little bit more to see how we’re actually evaluating the different actions instead of using these arbitrary thresholds. I know that there’s been recent work, I think Damien was involved again to do with individualizing a high intensity locomotive profile using both acceleration and deceleration, but also your max aerobic speed and max velocity. And I think they’re the key things really going forwards because if we move away from horizontal decelerations just for a second, high speed running at the moment, we’re all using this arbitrary cut off, whether it’s 19.8 kilometres an hour or 20 kilometres per hour to assign the absolute volume of running that they’re doing at that intensity.

 

I think if we really want to individualize it, you want to be using that max aerobic speed versus the maximum sprint speed and getting that anaerobic speed reserve. And I think the same can be said for horizontal decelerations as well. So unfortunately I don’t have the answers to what potentially can be the next movement for the centre of mass velocity elements but I think realistically, we want to be getting the inter-limb differences, which these more foot based accelerometer technologies are going to be offering just to get a bit more insight into what are the asymmetrical loading patterns between limbs.

 

And obviously there’s going to be position elements to that position specific elements to that and just more simply individual elements to that. You know, some players might prefer to use or have a dominant leg to turn off or to decelerate off. And if we’re able to monitor that at both the acute chronic level, we will be able to uncover the trends in relation to if one specific limb is getting overloaded versus another one potentially getting under-loaded? So is there going to be spikes in workload between the limbs in that sense?

 

So I think until we have these technologies validated and more use in research going forwards, we’re at a point where we’re going to have to make do with what we’ve got currently. And I mean, there’s still valuable insights to be made from GPS.

 

And I think if we’re to focus on horizontal deceleration as a key performance indicator within a weekly micro cycle, we’re looking at it from these two acquisition days. So on a day-to-day; we’re looking at two acquisition days, maybe potentially being a G -4 and a G -3, that being the days before a game, as these are windows of opportunity to  train horizontal decelerations.  From a monitoring perspective, you might get that using just simply counts of horizontal decelerations, you can get an indication as to the volume that has been carried out in a training session, whether that is through athletic development training or the sport specific practice through manipulation of drill parameters.

 

You could maybe see typically on an intensive day where the pitch areas are a bit smaller and you’ll see a larger volume of accelerations and deceleration and change of directions being performed. And then that will give us an indication of the volume of deceleration work that these players have been exposed to during training day or this intensive theme day. And I think that is more your volume element and I think Damien Harper discusses this kind of deceleration endurance aspect if we’re looking at it from a more physical rationale.

 

However, then I’d also highlight that in a typically more, what we call extensive training theme where you open up the pitch areas and typically, this is where you get the exposures to maximum velocity, and there’s higher volumes of high speed running, which is obviously a key training theme within the week. If you’ve got one match at the end of the weekend and on these extensive training days, we’re going for that high intensity movement speed. But you’d probably also see these high intensity decelerations be performed there. So with the greater distances that you typically get in from opening up the pitch areas, this enables higher movement speeds, which require more intense braking to slow the athletes down.

 

So I think if we’re looking at volume on an intensive training day and looking at the volume of high intensity deceleration actions on a more of a extensive training focus day, you might want to look at the intensity of the high intensity deceleration. And I know Tom’s criticized that potentially maximal deceleration doesn’t tell you a great deal because it can actually be just an erroneous movement action. And obviously the kind of unit error involved in that as well from a technology sampling rate perspective, it’s difficult to uncover. But maybe it’s just a way of informing are we actually exposing our athletes to high intensity or very high intensity deceleration actions that potentially offers a bit of insight, and opportunity to track that over time to see when our athletes, when our players have been exposed to above 90 to 95% of their maximum sprinting speed. And if they’ve not done that in the last few weeks, that’s something that we need to sit down and go, right, we need these players to be exposed to that stimulus.

 

And I think the same can be true for horizontal decelerations. I think if a player’s not being exposed to maximal intensity decelerations, it’s something that we need to sit down and go, right, well, we need to make sure that we’re preparing these athletes because this is going to be happening in competition.

 

I think currently based on the technologies that we have available to us at the moment, talking more about these whole body measures of exercise volume and intensity with GPS tracking, I think they’re probably our best bets to give us insights into the volume and intensity of actions. And there’s obviously frequency and density and all that kind of thing that needs to go on as well. But I think moving forwards, we really want to have a bit more insight into the interim differences between what potential deceleration loading is occurring which these kind of accelerometers like Playmaker or the IMUs and maybe give us a bit more insights into all the spatial temporal factors, such as ground contact times, stride rate, stride frequency.

 

We don’t actually know what athletes are exposed to during competition and training. Hopefully we can end up using these technologies in a bit more of our day to day practice to actually uncover the trends on an individual basis to see what is normal for an athlete and go, right, okay. So this player performs a significant amount of turns or deceleration on their left limb. Why is that? Is that a positional requirement? But then to go, is that normal for them? And actually, you know, they might turn a lot more off their left limb and they might actually have a lot more loading going on through their left limb. Just trying to find a bandwidth of what is normal, what is a spike, what is an under-loading to inform more individualized training strategies or interventions as a consequence of that monitoring.”

 

 

Top 5 Take Away Points:

 

  1. Horizontal decelerations are unique actions in comparison to other high intensity key performance indicators
  2. There are several testing options ranging from smart phone recordings, to radar guns to motion tracking.
  3. Currently GPS tracking is the main way of monitoring decelerations in professional sport
  4. There are key differences between the demands of a high intensity acceleration versus a high intensity deceleration with more of a metabolic cost to accelerations versus greater biomechanical loading of decelerations.
  5.  Future research – measurement of inter-limb differences using foot based accelerometer technologies

 

Want more info on the stuff we have spoken about?

 

Science of Multi-Directional Speed

 

You may also like from PPP:

 

Episode 372 Jeremy Sheppard & Dana Agar Newman

Episode 367 Gareth Sandford

Episode 362 Matt Van Dyke

Episode 361 John Wagle

Episode 359 Damien Harper

Episode 348 Keith Barr

Episode 331 Danny Lum

Episode 298 PJ Vazel

Episode 297 Cam Jose

Episode 295 Jonas Dodoo

Episode 292 Loren Landow

Episode 286 Stu McMillan

Episode 272 Hakan Anderrson

Episode 227, 55 JB Morin

Episode 217, 51 Derek Evely

Episode 212 Boo Schexnayder

Episode 207, 3 Mike Young

Episode 204, 64 James Wild

Episode 192 Sprint Masterclass

Episode 183 Derek Hansen

Episode 175 Jason Hettler

Episode 87 Dan Pfaff

Episode 55 Jonas Dodoo

Episode 15 Carl Valle

 

Hope you have found this article useful.

 

Remember:

 

  • If you’re not subscribed yet, click here to get free email updates, so we can stay in touch.
  • Share this post using the buttons on the top and bottom of the post. As one of this blog’s first readers, I’m not just hoping you’ll tell your friends about it. I’m counting on it.
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Since you’re here…

 

…we have a small favor to ask.  APA aim to bring you compelling content from the world of sports science and coaching.  We are devoted to making athletes fitter, faster and stronger so they can excel in sport. Please take a moment to share the articles on social media, engage the authors with questions and comments below, and link to articles when appropriate if you have a blog or participate on forums of related topics. — APA TEAM

 

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Pacey Performance Podcast REVIEW- Episode 379 Jose Fernandez

This blog is a review of the Pacey Performance Podcast Episode 379 – Jose Fernandez

 

Jose Fernandez

 

Jose is the leader of Sports Science at the Mahd Academy in Saudi Arabia, and was Head of Sports Science at Major League Baseball’s Houston Astros for five years prior to that.

 

Twitter

 

? Listen to the full episode with Jose here

 

Discussion topics:

 

What kind of things were you most proud of in the five years in your previous role with the Houston Astros? 

 

”Creating an infrastructure able to support some of the decision making, which is not just the decision making with regard to strength & conditioning which is what we usually think of.  When it comes to sport science we think of collecting data in the weight room, collecting external load and internal load data.  I think my work reached a little bit beyond just the traditional understanding of sport science to influence the way we were recruiting players for example, and how we help our scouting department with some of the decision making because at the end of the day we are using very similar technology and collecting very similar data, and we can help them go through those processes in a little more objective way and support those decisions.

 

It starts from taking it slowly and going step by step and showing value in any way you can.  At the end of the day there are two things you need to achieve; one is to influence in your work performance and the other is injuries and try to keep the players healthy and try to win more games or perform better.  The other part is make the life of the coaches that are working with you easier.  You are helping them save time, make better decisions and things like that.

 

 

Once you are able to help them at the early stages and they feel like you are not just there to say- this is what we are doing now, we are collecting this data and now you have to change your training because this technology is now saying this number is red instead of green.”

 

Can you give an example of how you made it easier for the coaching team?

 

”When I first arrived there wasn’t much in the way of objective data to help describe training or help evaluate where the players were getting better or maintaining certain adaptations during the season or not.  So my first goal was to profile the players in very simple ways.  The way I look at athlete profiling I try to think of it in terms of three different buckets.

 

  1. Aerobic fitness
  2. Force (max force) but also force x time (Power related capabilities)
  3. Speed (change of direction and acceleration)

 

I think those three buckets are not just important for my sport but probably universal for most sports and then you can customise a little bit based on your environment and where you are actually working.  When I think about those three buckets I feel that in most sports we are going to be able to prescribe training programmes with that information.  I think that in most sports Aerobic fitness and especially force and power are going to be in some way related to performance on the field or court.  I’m not saying that if you are stronger you are going to score more but when you look at the sport from certain actions there are certain things that start to correlate – ability to change direction, ability to be explosive in certain actions -throwing a ball at 100 mph, swinging the bat with certain power.


The second part is that, especially if you are working in North American sports where the schedules are very dense and heavy, usually the players that are stronger and aerobically fitter are the ones that are going to cope better with that stress; the ability to recover faster between high intensity efforts, and even from game to game.

 

So let’s go into how I collect the data.  For aerobic fitness I usually look at an intermittent field assessment- usually a 30-15 or a yo-yo IRT and usually I like to do that at least once per quarter so somewhere between 8 and 12 weeks get an update on that.

 

For strength and power this is interesting because a lot of people say, the schedule is so heavy, you play 162 games I am not going to bring the players up to anywhere near maximal loads.  From a philosophy point of view I actually like to bring them up to near max load load every 4-6 weeks because when you actually break down the schedule there are plenty of opportunities to load the players- the schedule and the games are not the same.  In a week we are going to be bringing the players up to anywhere between 2 and 4 reps with a barbell speed of somewhere between 0.1 and 0.3 m/s.  Right there you are automatically going to have a repetition maximum estimation.  This is part of training, this is not an actual assessment.

 

I am more interested in the training adaptations from one training cycle to the next training cycle, rather than going day by day or even week by week because at the end of the day I’m not thinking about fatigue changes, I’m thinking about adaptations to training.

 

With force plates you can also look at more specific force profiling based on specific positions that the players are actually doing on the field.  So for example, you can do an isometric squat assessment on the force plates at specific knee angles that are somewhat specific to what the baseball player is doing on the field, and understand what forces they are producing in terms of peak force and RFD.  Then you can compare that with two things; with what they are doing in a dynamic movement in a jump type assessment, a power related assessment.  The other thing you can do is collect very granular data on players performing sporting actions at a very high intensity level, with force plates on the mound.

 

 

So immediately you can compare whether a player is able to express certain levels of force physically in an isolated movement which has nothing to do with their sport and then you bring that player into a specific motion at a high intensity and you are able to compare if there are any deficiencies there as that will give you a clue if there is a technical fault or whether the player is not physically ready to create certain levels of force.  So now you can start giving advice on whether to work from a technique correction point of view or whether this is purely an output problem that we have to develop in the weight room, for example.

 

Most people are doing very similar assessments but it is that research that you do in the background to try to filter a little bit the noise within the force plates and try to understand what are the metric that are more important for your specific environment.  For a point guard in basketball it might be this and this metric because this is important for what they have to do on the court and for a baseball player it might be two or three other metrics.

 

For speed, in baseball we used to use a 30 Yard dash as that is specific to first base distance, and use speed gates to get the splits for acceleration and top speed.  You can elaborate more on top with video analysis and more specific technique type assessments with 1080 and computer vision etc.

 

I want to be very clear that it is not so much about testing; it’s that as part of training we are sprinting, as part of training we are doing max strength, as part of training we are doing aerobic fitness type of sessions – well let’s find opportunities to measure that objectively and update our database with the information so that if a player gets hurt we have specific benchmarks and if we have to make specific adjustments we can go back and see what the player has been doing.”

 

With the stress that is on the upper specifically in baseball was there any sort of profiling that would happen in that area?

 

”Yes there is.  The three buckets that I mentioned are more performance based.  When it comes to prevention we can be a little more granular.  So for us in baseball it’s shoulders, elbows and hamstrings.  We were looking at a couple of isometric strength assessments with a couple of options- shoulder external and internal rotation strength balance and maximal outputs and then we have the ASH test with force plates to look at RFD for the shoulder.

 

 

It’s a lot more important for pitchers because of what they have to do in every single game so then we will try to pair that data collection with when they have to pitch and get an idea of how they are recovering from games and if there is anything we can do to adjust and prepare for the next outing.”

 

What do think about wearable technology and some of the trends now to monitor things outside of your training sessions?

 

”If you work in a very complex environment when you have one or two coaches for 30 or 35 players, how much can you use 24 hours of information from many of those players and make changes on a daily basis?  So that’s why I am going for very basic buckets for athlete profiling and just focus on simple things that can guide your training process and help you understand if your athletes are getting better from training cycle to the next one.; rather than trying to optimise 99% your recoverability from one day to the next, as that is something that is going to be really hard to do in professional sport environments.”

 

 

Top 5 Take Away Points:

  1. Show value to coaches in any way you can – make the life of the coaches that are working with you easier
  2. Keep your athletic profiling simple – three buckets – aerobic fitness, force and speed
  3. Use specific tests to answer specific questions – is it technical fault or the player is not physically ready to create certain levels of force?
  4. When it comes to prevention we can be a little more granular.  So for us in baseball it’s shoulders, elbows and hamstrings.
  5.  Keep it simple – just focus on simple things that can guide your training process and help you understand if your athletes are getting better from training cycle to the next one.

 

Want more info on the stuff we have spoken about?

 

You may also like from PPP:

 

Episode 372 Jeremy Sheppard & Dana Agar Newman

Episode 367 Gareth Sandford

Episode 362 Matt Van Dyke

Episode 361 John Wagle

Episode 359 Damien Harper

Episode 348 Keith Barr

Episode 331 Danny Lum

Episode 298 PJ Vazel

Episode 297 Cam Jose

Episode 295 Jonas Dodoo

Episode 292 Loren Landow

Episode 286 Stu McMillan

Episode 272 Hakan Anderrson

Episode 227, 55 JB Morin

Episode 217, 51 Derek Evely

Episode 212 Boo Schexnayder

Episode 207, 3 Mike Young

Episode 204, 64 James Wild

Episode 192 Sprint Masterclass

Episode 183 Derek Hansen

Episode 175 Jason Hettler

Episode 87 Dan Pfaff

Episode 55 Jonas Dodoo

Episode 15 Carl Valle

 

Hope you have found this article useful.

 

Remember:

 

  • If you’re not subscribed yet, click here to get free email updates, so we can stay in touch.
  • Share this post using the buttons on the top and bottom of the post. As one of this blog’s first readers, I’m not just hoping you’ll tell your friends about it. I’m counting on it.
  • Leave a comment, telling me where you’re struggling and how I can help

 

Since you’re here…

…we have a small favor to ask.  APA aim to bring you compelling content from the world of sports science and coaching.  We are devoted to making athletes fitter, faster and stronger so they can excel in sport. Please take a moment to share the articles on social media, engage the authors with questions and comments below, and link to articles when appropriate if you have a blog or participate on forums of related topics. — APA TEAM

 

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