Sled Sprint Training
Resisted Sled Sprint Training to Improve Sprint Performance: A Systematic Review; Petrakos G, Morin J, Egan B. Sports Med. 2016;46:381-400
There are few worthwhile sports that do not involve some form of sprinting. Our bodies were made to run and sprinting is a VERY effective form of exercise to challenge your body’s aerobic and anaerobic engines. And if you are a tactical athlete, no physical activity is going to keep you alive better than sprinting under load.
Most coaches focus on two different programming modalities to improve sprint performance. Programs are designed to increase an athlete’s force/power output, or improve the efficiency at which an athlete utilizes the body at a given physical output (sprint technique drills such as ankling, heel kicks, and high knee drills).
To increase force or power, several methods have a positive transference of training to sprint performance. These methods improve strength, power, and reactive strength. Power lifts (squats and deadlifts) enhance production of force, Olympic lifts enhance force velocity, and plyometrics (such as drop jumps) enhance reactive strength. However, it is important to note that these methods only focus the force generation in the vertical phase. The problem is that sprinting is primarily a horizontal movement as opposed to jumping.
A recent meta-analysis reported a transfer of training between improvements in squat strength (vertical force production) and sprint performance. However, a greater transfer of resistance training to sport performance may be achieved if the conditioning program emphasizes a similar motor pattern and contraction type (i.e. comparable mechanical properties) to the performance movement.[i]
Rabita et al. summarised that elite sprinters are able to produce greater horizontal force per unit body mass at any given velocity than sub-elite sprinters, and that production of greater horizontal force is due to a more horizontal orientation of GRF (i.e. technical ability). Additionally, non elite sprinters produce equal, if not more, resultant force per unit body mass than elite sprinters. Therefore, resultant and vertical force production are not the key variables for differentiation of sprint acceleration ability.[ii]
There are two key physical determinants of sprint performance: acceleration and maximum velocity (top speed). To improve your sprinting you need to advance your performance in each. Resisted sled sprint training (RSS) appears to be an effective tool for improving both sprint acceleration and maximal velocity (top speed). However, the volume and intensity to be applied in RSS training has yet to be adequately defined. We thank the authors of this review for doing a deep dive on the science currently available.
RSS training involves a set number of maximal straight-line sprint efforts whilst towing a sled device. The sled is attached to the athlete by a chest or waist harness and cord. External load is a direct function of the sled mass and the amount of friction between the sled and the ground surface. My own summary of what RSS offers is that, for the horizontal performance in sprinting, heavy loads are the powerlifts and lighter loads are the Olympic lifts of horizontal ground reactive force. That’s kinda cool.
The authors found 11 studies that utilized sled towing devices. Sled loads were described as a percent of body mass (%BM), a targeted reduction in velocity compared to unresisted sprint velocity, or as an absolute load.
These were the key points:
- RSS training improves performance at 10-40 % of BM. Lighter loads show no improvement over regular sprinting and are therefore worthless.
- Combining RSS with plyometrics and unresisted sprint training is likely to give the highest performance gains.
- Light loads (10-20% BM) improve maximum velocity, whereas heavy loads (20-40%) improve acceleration
But what about really heavy sled pulls and pushes? Is there some value there? Maybe as a lineman in football or the scrum in Rugby. There is a legitimate concern that sprint kinematics associated with RSS training may result in a negative mechanical transfer from ‘heavy’ RSS training to sprint acceleration. The old adage of “train slow, move slow – train fast, move fast” holds true here. If the resistance is such that you cannot move your legs quickly over a full range of motion then your training will likely not result in significant improvements in performance.
The easiest method of calculating load is the %BM method perviously mentioned. But this method does not consider differences in strength, power, and or sprint velocity characteristics. An RSS load prescribed as %Vdec (% decrease in your normal sprint velocity) considers these differences but is more difficult to calculate. Practical equations are available to calculate percentage reductions in velocity without the need for rigorous testing and should be used by coaches with elite athletes. For the nonprofessional athlete wanting to utilize RSS in his or her programming the % BM seems to be nearly as effective and is what I use.
As far as harness attachment and cord length go, a belt attachment will challenge hip extension more and a chest attachment will challenge knee extension more. You should train with both but focus on that area of your movement pattern that needs the most work. I have personally had problems with being more quad dominant in the squat – thus I need to work more with the belt attachment. However, this is based on studies from heavy sled walking and may have limited application for sprint training. Stay balanced is good advice
The authors state that “Optimal training volumes in an overall training programm are therefore a function of sled load, concurrent URS training and training experience. However, as a general recommendation based on current evidence, effective sled sprint training blocks will last for 6 weeks and include two to three sessions per week of 5–35 m sprints, totalling 60–340 m per session.”
[i] Seitz LB, Reyes A, Tran TT, et al. Increases in lower-body strength transfer positively to sprint performance: a systematic review with meta-analysis. Sports Med. 2014;44(12):1693-702
[ii] Rabita G, Dorel S, Slawinski J, et al. Sprint mechanics in world- class athletes: a new insight into the limits of human locomotion. Scand J Med Sci Sports. 2015;. doi:10.1111/sms.12389.