Pacey Performance Podcast REVIEW- Episode 331 Danny Lum
This blog is a review of the Pacey Performance Podcast Episode 331 – Danny Lum
Danny Lum
Background:
Danny Lum
Danny is Head of Strength & Conditioning at the Singapore Sports Institute for seven years,and also currently doing a PhD with a research focus on Isometric Strength Training for Sports Performance. Prior to that he was the Strength & Conditioning Officer for the Singapore Armed Forces so was dealing with Military Training.
Danny completed his undergraduate degree at the University of Western Australia (UWA) prior to doing the role in the Military for two years.
Discussion topics:
What options have we got when it comes to Isometric testing?
”There are single joint testing options as well mainly using the biodex equipment for rotator cuff internal/external rotation of shoulder, knee flexion/extension. We also have multi-joint isometric testing such as isometric squat, isometric mid-thigh pul (IMTP), isometric bench press and isometric prone bench pull.”
Why would we go down that route in the first place with Isometric testing vs. something more dynamic?
”The information we can get from isometric testing includes not just the peak force, but also the rate of force development (RFD) and if we combine the data we get from the counter movement jump (CMJ), and IMTP for example, we can actually calculate the dynamic strength index, which I believe many coaches are using it as an indication of whether they should train their athlete more with plyometrics or with heavy strength training.
Some of the advantages of isometric training is that it is much safer because there is no movement involved you don’t get injured that easily, and it’s pretty quick, 5-seconds and you’re done. The disadvantage is you can’t really use it for exercise prescription, like a 1-RM strength test.
Quite a lot of studies have shown the peak force and the RFD are significantly correlated to activities like sprinting, jumping and change of direction. There are also studies that have looked at striking, throwing and recently we did a study with sprint Kayaking. I want to think that isometric strength assessment data will have a high correlation with activities that has mainly concentric contractions like cycling and sprint Kayaking, but the relationship with dynamic activity that requires the stretch-shortening cycle with the eccentric and concentric phase might not be as great.
If you look at the literature and take IMTP and isometric squat for example, the relationship you get from the peak force with CMJ range from R = 0.30-0.80 so the range is pretty huge. There could be a lot of reasons for this; it could be because of the familiarization, different athletes with different training experience and different strength levels and also the time of the year and the training phase they are in.
Another thing to look at is the joint position where the test is conducted. So for example, if you look at the literature you will see that the isometric squat when tested at a 90 degree knee angle vs. 120 degree knee angle; the relationship between the isometric peak force obtained and CMJ jump height will be higher when the peak force was obtained at a 90 degree knee angle, and same for sprint performance. What we can get from this, is that if you want to conduct the isometric strength test to see if there is any relationship with a certain activity, probably get the person to adopt a joint position whereby the concentric force is initiated at 90 degrees. This makes sense because the CMJ is usually initiated from a position where the knee is at an angle of about 90 degrees.
But there is something interesting- that works for squat, but IMTP doesn’t work that way! You can see that a IMTP is usually conducted at a knee angle of around 130-140 degrees, yet the magnitude of the correlation with the CMJ height is as high as that obtained for the isometric squat at 90 degrees! This is something I personally do not understand!!”
What is the dynamic strength index and why would coaches be interested in it/calculate it?
”First we collect the peak force from IMTP- theoretically that is the highest amount of force your lower limb can produce. You can also obtain the peak force of the CMJ. Then you can divide the peak force of the CMJ by the peak force of the IMTP
Dynamic Strength Index = Peak Force IMTP / Peak Force CMJ
The isometric peak force on an IMTP is the maximum amount of force you can produce and how much of this force can you translate into a dynamic movement. The Dynamic strength index provides you with an indication, so I think if it is below 0.65 this indicates that your athlete might need a little more ballistic training like plyometrics. But if the dynamic strength index is above 0.80 then the athlete probably needs more heavy strength training.”
Isometric training as a training tool- what benefits are people going to get from isometric training?
”First of all, similar to the isometric testing, it is simple, the risk of injury is very low. You can see that in most of the injury cases, injured athletes will start off with isometric training to get the muscles activated (even when they are in a cast). The exercise physiologist would advise the patient to perform some form of isometric contractions.
The disadvantage is that people believe that with isometric training you only gain strength in that specific joint angle that you train at, of course when you look at the literature, this is not true.
It really depends on the joint angle. If I position the knee angle at 90 degree vs. 150 degrees. At 90 degrees my quadriceps will be stretched more compared to at 150 degrees. So if I train my quadriceps at a knee angle at 90 degrees where it is stretched a little more then the strength gains will increase across a greater range of motion as compared to a quadriceps at a short length. So based on literature, if you train your muscles at a longer length using isometric strength training, then the strength gain might range up to about 40 degree from the angle you train at. But if say, you train at a short muscle length, which is about 150 degree knee angle, then the strength increment might range up to about 15 degree from the angle you train at.
The adaptations from strength training are similar to dynamic strength training. You still get increased neural firing, neural recruitment and hypertrophy of muscle. One of the adaptations from isometric training that is superior to dynamic strength training is the increase in tendon stiffness.
This has high implications on RFD, so with greater tendon stiffness the force transmission from the muscle can be more efficient and will improve force production and RFD.”
When creating isometric exercises in some very sport specific positions what kind of creative process are you going through when thinking about integrating some of that into these sports?
”Two things. First thing is I’m always looking where the concentric action is initiated, and second is the position which reflects the bio-mechanically most disadvantageous position, for example the sticking point of a squat.
With a group of Kayakers I replaced two sets of squats, two sets of bench press and two sets of bench pull with the isometric version of it, and the joint position they adopted was initiated from a similar place where the pull phase of the Kayak stroke was initiated. What we found was that by replacing two sets with isometric training as compared to a normal traditional strength training programme, the Kayaker’s strength actually increased and performance on the ergometer 200m time trial was improved more than the group that only did the traditional strength training.
What I believe is that by performing the isometric training at the position where the stroke was initiated this increased their ability to overcome the initial drag force they would face as they initiate the pull phase.
I just completed one study with recreational runners where we compared plyometric and isometric training for endurance running performance. For the isometric training they did a IMTP and an isometric plantar flexed ankle, so the ankle was in a neutral position when they did the plantar flexion. What we found was that running economy was actually improved with the isometric group as compared to the plyometric group. One possible reason is because recreational runners tend to avoid heavy strength training so with the isometric exercises as a stimulus that greatly improved their strength. In that sense, people might ask if that would work with elite runners, and that would need to be researched.”
When it comes to programming isometrics within the wider programme (annual plan) where does it fit?
”That is an interesting question, and honestly, I have no idea at this moment in time. Personally what I do with my athletes is slot in the isometric training somewhere in the middle of a strength phase, because we know that if you have been training with the same method for a long period of time you tend to plateau. So with the addition of the isometric training for a few weeks that might help to break the monotony and you might see some improvement.
We don’t know at this point in time that if we continue to get the athlete to perform isometric training, will there be a long term benefit (because all my studies have only been 6 weeks long)?
The next thing I do is as we get closer to important competitions I get my athletes to perform complex training, and I usually use the isometric exercise as the conditioning activity to induce the post activation potentiation (PAP) effect, before they move onto the ballistic exercise
One reason is because they get to perform maximal contractions so that helps to maintain their maximal strength and because it’s an isometric movement we are reducing the risk of injury close to competition.”
Is it possible to manipulate some of the variables within isometric training to target different physical qualities such as hypertrophy etc?
”When you look at the research you can categorize isometric training into two different methods- yielding and overcoming.
Overcoming
Overcoming- is the method I have been researching where you push maximally against something you can’t move.
Yielding
The yielding or ”holding” method where you lift a weight that you can actually lift around 60% of your 1-RM, get to your sticking point and hold it there for about 10-seconds before you push it concentrically.
When you look at the research on isometric strength training, in order to get maximal strength increases you want to be contracting as near to maximally voluntary contraction (MVC) as possible in a range of 80-100% MVC and each contraction you don’t want to be holding for too long, otherwise you might compromise the adaptation.
When it comes to hypertrophy you want to perform the contraction at a lower intensity and sustain the contraction for a longer period of time, as long as 10-30 seconds in one go. Recently, there is one study which showed that the inclusion of isometric training might be able to induce a stimulus similar to blood flow restriction training. So when you are sustaining the isometric contraction you are actually constricting the blood flow.
Another study by Brett Shaunfield showed that performing isometric contractions in between sets increased the hypertrophy training effect. So during the hypertrophy phase one of the things you could do is perform a lighter load in the final set and doing a long duration isometric contraction at the sticking point to increase the hypertrophy effect.
In terms of other variables, first we need to know what we want to achieve before we start talking manipulating the variables. Variables we can manipulate include the joint position. I mentioned earlier that if we train at a joint position that induces a longer muscle length your strength improvement will be greater throughout a greater range of motion.
At different joint positions you might induce hypertrophy at different parts of the muscle.
So for example, if I was sustaining isometric contraction at a long muscle length most of the hypertrophy training effect might take place at the middle of the muscle belly (midsection). If I perform it at a shorter muscle length, most of the hypertrophy might occur at the proximal or at the distal portion of the muscle, so these are things that people will need to consider.
To increase maximal strength you will need to contract at a high percentage of MVC, and to increase RFD you will need to contract at a high contraction speed, so in sports performance you should always try and contract explosively because we are not just talking about how strong you are but we must also ensure the athlete can produce the force as quickly as possible.”
Are there any gaps we are looking to plug in the research?
”Firstly there is training at long muscle length vs. multiple joint angles. I mentioned that if you train at long muscle length the strength gains will be higher through a greater range of motion but if we train at multiple angles it might actually be more beneficial. So if I compare 3 sets of bench press at 90 degrees vs. 1 set of 180 degree, one set at 90 degrees and one set at another angle we could compare multiple joint angles
The other limitation of what we know is how long this beneficial effect can last?
The other one is comparing the training effect of a yielding method (more similar to an eccentric method) to the overcoming method (more similar to a concentric method). So get someone to push against 80% MVC and the other guy resisting against 80% MVC and comparing the adaptation.
When doing this in training I would probably a certain number of sets so for example if I am going to get the person to do back squats 4 sets I might have them do two sets dynamic and two sets isometric. The isometric is better at improving the strength at a specific joint angle, but when it comes to a full range of motion, isometric effect is still not as good as dynamic strength training, so I wouldn’t use isometric training as the main bout of the training but I would recommend the isometric training as a supplement to improve the force production at the sticking point or at the bio-mechanically disadvantageous position.
In a complex setting, I would do the isometric exercise as the conditioning tool I would reduce the number of repetitions rather than trying to get them too fatigued. But at the moment I haven’t done a study to identify the ideal number of sets.”
Can you explain to us what we mean by quasi-isometrics (I know this is something Alex Natera has mentioned?
”Take the hamstring for example, which is a bi-articular muscle so when we are running and the hip is flexing the proximal portion of the hamstring is stretching but when the hip is flexing the knee will be flexing as well. So the distal portion of the hamstring will be shortening. So in that sense one portion is lengthening and the other portion is shortening, so that pretty much looks like an isometric contraction, and that is what is meant by a quasi isometric contraction.
So if you take the hip thrust but with the knee in a slightly more extended knee position (around 150 degrees) with the shoulder on the floor, with the hip in the air, the hamstring closer to the knee will be trying to produce a concentric contraction so you can stay up. But while the hip is heavy gravity will be pulling it down so the proximal portion will be in an eccentric contraction. So the distal portion will be in the Push isometric contraction while the proximal portion of the hamstring will be performing a yielding contraction.”
Top 5 Take Away Points:
- Isometric is a safe and effective way of performing strength testing and training.
- Dynamic strength index = Peak Force IMTP / Peak Force CMJ
- Importance of range of motion- strength gains will increase across a greater range of motion as compared to a quadriceps at a short length.
- Importance of tendon stiffness- one of the adaptations from isometric training that is superior to dynamic strength training is the increase in tendon stiffness.
- Considerations when choosing position- the place where the concentric action is initiated, and the position which reflects the bio-mechanically most disadvantageous position.
Want more info on the stuff we have spoken about? Be sure to visit:
Twitter:
@DannyLum82
You may also like from PPP:
Episode 372 Jeremy Sheppard & Dana Agar Newman
Episode 217, 51 Derek Evely
Episode 207, 3 Mike Young
Episode 192 Sprint Masterclass
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
