After good sound running mechanics are in place, loading sleds for resistance speed work is a good option. For those that don’t have hills, sleds are a must, and parachutes don’t work early acceleration enough for me to use them. Sled sprinting is not the same as sled pulling or pushing. Changes in kinematics often change the motor skill development and muscle recruitment. I have used wireless EMG and yes some differences exist, but only if one loads the sled near 50% of bodyweight. While very heavy sled use may help performance, only if the athlete rarely sprints fresh (team sports) or if they are not sufficiently trained in the weight room. Unfortunately I see athletes in HS that are a sloppy 230 thinking they can use sled loads and training programs of college D1 starts when they are suffering to break 5 seconds in the 40 while the freak in the SEC is running 4.3 with a body greek gods would envy.
While combine speed may not transfer to the game, one should at least preserve the speed one has or even improve those with little speed, even at later years. Often very good athletes are treated with kit gloves early and never train, just go through a magic show to keep the coaches feeling that they are addressing training. Without timing speed or even testing power, what is the coach doing? Keeping people healthy usually means babysitting with funky exercises that don’t have anything to compare to. If you do a vertical jump and it’s 24 inches, well we know some freaks jump 40 plus inches, hence why some coaches do box jumps as it’s more skill than absolute power. The same is when coaches do sled work and don’t time. While timing isn’t essential, it’s valuable since the purpose of sled sprinting is to help regular sprinting. With such little difference, why not time?
Timing and taping sprints allow coaches to see the mechanical problems, and addressing speed via speed training is the best option. I like teaching sled training for two weeks before any watch or camera comes out unless it’s for a special purpose. I like timing the second step because it takes a lot of skill to be perfect on the first steps because the slack of the harness creates some jerking motions. The last year I found that the times were not even close to the the 10% rule even with light weights. After time the athletes learned to sprint but were uniform in mechanics as the posture stayed the same versus gradually rising. This was good for some athletes who struggled to have the quad stiffness and ankle strength for the first ten meters. Soon the differential improved dramatically but then the gap continued as unweighted speed improved because of the sled, lifts, and general acceleration work.
Sled work is valuable and should be used as much as necessary. I think the unique demands of equipment and having a harness should make coaches aware that a major speed leak can happen if one is not coaching up the runs, especially managing tension on the sled harness ropes or straps. Doing so early will help sleds create overload on each stride so that athletes can really feel comfortable in leaning position, something wall drills and heavy work can’t provide.