Research on resistance options (such as sleds) says that 12 percent of bodyweight is best practices. I don’t agree with the researchers because athletes in similar sports that care about power to weight ratio always want to shift those numbers. One question would be is the horizontal resistance of sprinting with restaince at max speed going to help more developing top end velocity than vertical (weight vest) options? Shouldn’t we see 12.5 splits soon? The equipment and facility options of sleds, hills, and vests have been around forever, but I believe that best practices with such equipment remain a mystery. I have some guidelines based on the success of many programs I have witnessed first hand and of course experimenting with the coaches that have preceded my career.
The 10% BW (I prefer timing splits) rule is not specific enough to prescribe sled training. Bodyweight is not appropriate as you don’t see numbers prescribed based on bodyweight alone, you prescribe loads from a combination of ability (best numbers) and relation to BW. 10% speed is a great number, but is it convenient and the same for all distances? Charlie focuses on 30m resistance work and much attention was focused on 30-60m to refine that zone, but as we get to top speed elastic forces (vertically) become more important. I don’t know exact rules as some athletes benefit differently, but here are some guidelines to find out what can be tailored to athletes.
Weight- The easiest variable to change is sled load. Intensity of effort is subjective unless you have a Redbull like sensor project with GSR and EMG and other measurements. Weight is absolute and very simple to record. Assuming all being equal, coaches will likely focus on load the most during training.
Distance– Most coaches work on 10-30m as the acceleration is higher during the early phase of sprinting. Later distances interrupt mechanics significantly according to research but it’s unclear if the loss of mechanics is being offset by the improvements in gross power.
Surface– Grass, turf, or track? Short grass, wet grass, incline or flat? Many coaches don’t write down those details as I have seen 2-3% differences in surfaces and that completely ruins data sets if this information isn’t used.
Sled Set-up- Just using the same sled is not enough. Often changing belts to body harnesses or lengths of the rope can change the performances.
Acceleration Pattern- Athletes tend to hold the same posture throughout the entire run because they are towing something, thus being able to hold a posture. In sprinting this doesn’t happen obviously but the improvements in specific running power will offset the possible mechanical disruption. Athletes can manipulate the distance and starting posture to work on specific specifics of the acceleration.
In summary coaches can go shorter and heavier, longer and higher in postures, so far as it actually does what they think they are doing. For example 20 kilos with advanced athletes is up to 25% of BW load, but could be 15% of acceleration speed if done right (the right conditions). An athlete can increase their load used while staying at the same 10% of PR, but if they are improving this target will move up and be more static, unless the coach is able to manipulate the variables really well. If athletes with a specific sled protocol are dominating the first 30m phase, then it’s possible the protocol is working. We have race splits to show if athletes are evolving from the protocols. I think the real evolution is coming from more winter training and less indoor competition, but a triple periodization rebirth could happen if done right (training camps in Europe, charter flights). Coaches love doing contrast work, but PAP can be tested to see if the splits are actually faster than normal runs without the overload. Supramaximal means better than PRs or closer to PRs, not just not sprinting with a lighter or lower load. Athletes love feeling faster, but are we getting better acceleration times rather just higher loads on the sleds? If so practice data, not story or verbal summary will provide the right evidence.
In Part 2 I will share protocols such as contrast work, loading patterns, weight room and planning that we felt help this past season.