This week I delivered a presentation to my team of coaches on a case study of the work I am currently doing with a 14 year old female Tennis player. One of the physical goals of the programme is to improve acceleration technique over short distances. The athlete in question ‘pops up’ very early in her acceleration creating braking forces in front of her rather than pushing back under her centre of mass.
I thought that resisted sled sprints might be a good way to improve this.
This blog is a short review of some of the blog posts and journal articles I reviewed to help me develop a programme for improving acceleration performance. I also talk about this in the latest episode of Daz Dee TV
To develop speed, most power athletes lift weighted loads, sprint and do some jumps. This kind of training allows you to work speed and force from both ends by driving maximal power and strength in the weight room and doing long accelerations with light load. The light load accelerations help to improve efficiency of the physical output using a very specific method.
Typical resisted sprinting programmes advocate use of loads equating to 5-10% body mass, and typically we then observe that the time taken is within 10% of the unresisted performance of the athlete. I call this the 10% rule.
Indeed a recent study showed that a resisted sprint with a load equating to 5% of body mass prior to a short sprint (20 metres) does not appear to affect sprint times or kinetics. However, it does appear to enhance the rate of force production.
More recent advances in this area have lead to the term ”Maximal resisted sled load, or MRSL”, which is the maximal load at which the athlete remains in sprint acceleration from 10 to 20m in a 0-20m resisted sled sprint.
I learnt today that it is also fairly common to use very heavy sled training protocols to improve the initial acceleration over the first 5m. This makes sense because initial acceleration is all about overcoming your inertia in the first few steps. Beyond 5m maximal forces don’t matter as much as how athletes create body speed. A study by Morin et al in the Journal of Sports Physiology and Performance showed very heavy sled training (at 80% body mass) increased maximal horizontal force capabilities, resulting in moderate and small improvements in 5m and 20m respectively.
Why does Heavy Sled sprinting help acceleration?
It gets them comfortable with very aggressive angles so they get greater exposure than just a few steps like in falling sprints for example.
Falling starts are useful but you don’t get to feel the forward lean posture for very long. The efficiency of the physical output following heavy sled sprinting involves a foot strike more under the centre of gravity and thus increasing the time for propulsive force production. This doesn’t mean longer ground contact times. It means it teaches the athlete to use more of the ground contact time to produce propulsive force. This all amounts to more practice of horizontal force application.
=> Trunk lean
=> Horizontal application of Force
=> Rate of Force Development
2 blocks of 5x 20-metre sprints (2-minutes recovery between the five sprints and 5-minutes recovery between the two blocks).
There is a great article on programming for resisted sled sprint training on simplifaster.com
Read the whole article here
I hope this has been of interest to you.
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