Resisted Sprint Training (RST) is the addition of some form of external resistance during performance of a sprint workout. RST can take on many forms. Running into the wind, uphill running, and towing (sleds or parachutes) are the most common methods. While each of these methods brings something a little different to the table and each athlete/coach probably has developed a favorite, there are certain commonalities that must be considered whenever programming this type of training.
The addition of any type of resistance will almost certainly alter the mechanics of the athletes sprint stride, even if only slightly. Specifically, the extra load will undoubtedly lead to lengthened ground contact time and overall slower locomotion. Because of this fact, I view Resisted Sprint Training as a specific strength developer as opposed to a sprint exercise. These tools can be used to overload the muscles directly involved with sprinting in the exact manner that they will be used during sprinting, at a speed approaching that which will be used during sprinting. RST will develop the athletes max force production capabilities as well as local muscular endurance of all the muscles involved in sprinting. While these same muscles can be developed in the weight-room it is almost impossible to duplicate the rhythm and synergy of all the musculature involved in sprinting. While force production during RST is slower than during sprinting, it is significantly faster than during traditional strength exercises performed in the weight-room. The use of RST allows for a transitioning and transfer of the strength developed in the weight-room to the power and speed required to improve running velocity.
To effectively use RST as a strength developer, it must be coached that way. The focus needs to be on full and explosive triple extension of the support leg, straight line forward (not upward) knee drive of the swing leg and strong postural alignment and control. Since ground contact will be altered, the athlete must use this extended time on the ground to truly drive and generate as much force as possible. This requires great discipline as most athletes will attempt to create the same sensation of speed they experience during free sprinting. In an attempt to do so, they will often cut their stride short in order to increase stride frequency. Stride frequency should not be of concern during RST. Only full, powerful leg drive and the achievement of optimal stride length are important for this specific strengthening to be effective.
Because top end speed is impacted so greatly by stride frequency and because stride frequency is altered during RST, it is ineffective for the development of max velocity. Acceleration on the other hand, is greatly influenced by pure strength. The need to overcome inertia during the start, drive and acceleration phases of sprinting allows an athletes strength capabilities to have their greatest impact on speed at the very beginning of a run. Short distances of 10-20 yards allow for RST to be used most relevantly, with proper technique and a fairly significant load. The mechanics used during the drive phase are most effective for force production. If the distance increases (beyond 10-20 yards), the drive mechanics will begin to switch to top end running mechanics, reducing the capabilities of the athlete to handle a heavy load, and lessening the desired effect of the exercise.
RST drills can be programmed alone or in combination with “free” sprints. At the beginning of the off season, I prefer to focus solely on RST drills so as to get the coaching points across to the athletes and to accumulate significant volume and a strong strength base. As we get closer to competition (and speed becomes more important), I combine resisted and free sprints in the same workout. I have found that this accomplishes a couple of my goals. It allows the athlete to immediately get back to natural (faster) sprint mechanics, hopefully with the advantage of truly feeling the "drive". Often time this may even lead to an over-speed effect or sensation as the athlete will feel ultra-fast when running free immediately after removing the resistance. Any residual potentiation effect is also a benefit as the neurological excitement elicited by the resisted sprint will hopefully lead to a subsequently improved free sprint performance.