The use of resistance sprinting, specifically weight sled training, is a valid tool for improving acceleration in sport. With most team sports benefiting from improving short acceleration, it is no mystery why so many coaches use weighted sled pulling to improve the ability to accelerate the body over short distances. Scientific literature and coaching experience with resistance sleds doesn’t address every detail in use, but enough experimentation and research does give us enough guidelines to make good decisions and workout planning. In the past, proper use of sled sprints were based on rough estimates or rules that were not complete, and this article series will cover best practices with sled use for speed, specifically acceleration.
Acceleration in track and field is up to 60 meters, but most of the action is within the 0-20m segments in all sports. Athletes usually sprint from a three-point start or crouch position with sprint sleds to overload the pattern with external load. With the golden rule that one should not exceed 10% body weight or 10% decrease in speed, there is much debate regarding the ideal way to prescribe external resistance. Most coaches have used external load and not time, since electronic timing has often been a burden to set-up or is not practical in group settings. Since Freelap Timing has increased in popularity over the last few years, so has the increase in experimenting with sled sprints, since timing is an easy option. In this article series, time as well as load will be used to improve the precision in designing sled workouts so one can achieve better results.
There are four true variables when working with sled sprinting. They are distance, mechanics, load, and speed. While load (resistance) can reflect different surfaces, sled designs, and the external load added, those factors usually don’t change. Most coaches will understand the need to compare the same set-ups each time they train, so different sleds on different surfaces having different friction levels is not a hard concept to understand. Here are the guidelines for the four variables mentioned above.
Distance: Sled pulling should be done over 25-30 meters only, as the literature shows very little transfer past 20 meters and none as one gets close to top speed. While improvements over 5-10m may benefit athletes, the longer sprints tend to develop better capacity to sprint over all short distances, not just the first few steps. Also general leg power will transfer over the first three steps, making sleds a good answer for steps two through ten or more.
Mechanics: Rehearsal of sprinting technique is important for sprinters, but even team sports having a solid running mechanics is a smart way to safely improve performance and decrease injury potential. One of the fears of having heavy loads on sleds is that they will degrade technique or fail to transfer to regular sprinting in games. While small mechanical changes will occur from loaded sled sprints, they are not significant if they are near the same speeds as unloaded sprints.
Load: Sleds overload the acceleration sprint by creating friction to the training surface via the sled design and additional weight. The sled design and surface choice is usually not going to change, so most loading adjustments are made by adding or subtracting weight. Loads have traditionally done by estimating a percentage of one’s body weight, but with body weights staying the same or changing, a combination of speed difference and external load is more useful. Two athletes being the same size but dramatically different in speed having the same external load doesn’t make sense, even if they are roughly the same in the weight room.
Speed: Acceleration by definition can occur at any distance, but the primary zone is the early phase of acceleration, or 0-30m. Research has shown that little influence from sleds can come from the 20-30m zone, but for practical purposes one should run through the line to ensure the first 20 meters is aggressive. The 20-30m zone may not have the same impact from sled sprints, but no research has shown that a combination of moderately loaded sleds and unloaded sprints impaired late acceleration. Exclusion of 20-30m sled sprints doesn’t seem warranted, and very light loads may help the later acceleration phase just as the heavier loads may help with early acceleration (5-15m).
Electronic Timing of Sled Training
The simple way to decide what load to use is to time the sprints and keep at a speed reduction that doesn’t eliminate the elastic qualities and unique motor skills of sprinting. With each step becoming increasingly faster, longer, and more elastic, the load must be light enough not to hinder any of the kinetic properties of acceleration. Visibly this is difficult to see, but the easiest starting point is to use 10% of body weight, provided the athlete is lean and has already started strength training at some level. After the athlete becomes comfortable sprinting with sleds, start actually timing the sprints to see change in practice.
A simple rationale for not comparing first movement times of normal sprinting is that sleds have some unique challenges when using equipment. Sleds themselves tend be jerky with the first couple of steps and first motions are usually sensed with the hand movements or foot pressure. Both sensors are left behind the athlete and are susceptible to being run over by the sled behind. Electronic timing gates don’t time first movement, they time when motion passes the line of sight. Thus, having the Freelap junior transmitter get the first meter (1.80 meters away from the line) and at 10, 20, 30m if possible. Simple timing set-ups with two transmitters can get the total time, but additional transmitters can get each segment for added analysis.
In summary, sled training has specific benefits only when they are tailored to the athlete in great detail. It would be convenient if a universal load could help everyone easily, but more benefit exists when the load is specialized, especially at higher levels. It is important to record both the load used and the progress being made by timing, even if one is not going for a specific goal time. In order to ensure the training program is creating improvement in performance, recording times can help shed light on what is happening in the training process.
Sprinting with sleds follow the same protocols as and basic sprinting, but some special options exist with some caveats to the normal rules of training. Acceleration can be enhanced with proper sled use in addition to some additional options that help break normal plateaus that coaches experience after a few years of use. In order to know if the athlete is responding to the sled training, timing is going to be essential, especially after the first year.
Advanced options such as mixed loading, contrast training, complex training, and general periodization factors can exploit the use of sleds. Any change to a program that is new will likely create an improvement from breaking boredom or training monotony, but after a few years weighted sleds themselves will start decreasing in interest with athletes. Advanced options are indeed advanced, not because they are more demanding, but they are especially effective for those that have been doing sleds for more than two years and need something more to challenge the body. After 1-2 years of solid training with sleds, athletes can start using additional methods to overload safely.
Mixed Loading
The first option athletes can do is to simply progressively overload the sled by adding incremental weight. Eventually most athletes will hit a plateau time wise and need loads that are lighter or heavier in the same workout to add variety. A simply option is to do 3 sets of 4-6 sprints with each set getting heavier or lighter. Another option is to use random patterns of medium, heavy, and light loads, all within reason to challenge the athlete. Following the range of 5-20% of speed reduction, a coach should try to keep the average closer to 10% or more, especially with sprints beyond 15m.
Coaching Point: Average the external weight of the sled and average the sled times as well.
Contrast Training
A popular and timeless option is to use heavy loads followed by free sprinting to take advantage of some sort of potentiation effect. With PAP, or Postactivation Potentiation, a stimulus or overload is expected to create some sort of window of greater or supra-maximal ability immediately later in the session. Many athletes find the sprints immediately after resisted sleds to be a positive effect, but no research validates this anecdotal experience yet. Regardless it’s easy to see if a potentiation effect exists if one times all the sprinting and examine if a rise in improvement is significant to defend the use of contrast training. Regardless if it’s just a placebo, variety in training is a valid option and contrast training can add that option to experienced athletes.
Coaching Point: Compare the sprints without resistance after contrast work with earlier performances within the training period. The sprints immediately after resisted sleds should show some noticeable improvement specifically from the use of the contrast method.
Complex Training
Similar to contrast training, complex training works by using paired exercises to create unique combinations. Unfortunately a practical limit usually reduces the use of complex training because it requires immediate grouping with another exercise, something that requires more space and getting the harness on and off. No research exists currently to identify the specific window duration between exercises, but athletes don’t need to be racing to the next movement to take advantage of the sensations. Sleds paired with horizontal bounds or throws (and even general max power exercises with weights) can produce a way to challenge advanced athletes.
Coaching Point: Compare the acceleration abilities of the athlete to see if they are generally faster (average times) or running the same speeds earlier in the season.
Periodization of Sled Use
Most programs use sleds in the fall or general preparation period, but sled use can be done in the early spring if one is doing additional work or doing additional specific preparation. While no definitive rules exist of frequency, volume, and sequence with sled use, a good idea is to spend no longer than two months in a specific sled phase. With the research showing that the kinetics and kinematics being different significantly with sleds versus sprinting without resistance, spending too much time at slower velocities could create adaptations that are not favorable to top performance. While no true “cap” exists on the length or even volume of sled use in a program, a balanced program seems to be prudent. The emphasis of sled use is highly dependent on other variables, such as other running volumes and speeds, as well as general themes of power (rate force development), energy systems, and technique. How deep one emphasizes acceleration beyond sled use, is influence by what other training options are complimenting it, such as starting strength and power training.
Coaching Point: Create a benchmark or goal time to hit with sled sprints, along with volumes that you feel create a training effect. Acceleration should show markedly better improvements in testing or in split analysis of races later.
Sled training is one fantastic tool that coaches can use to enhance the development of acceleration. Using the right loads and monitoring speed coaches can find unique and individualized programs for athletes looking to improve early acceleration, the most coveted quality in team sports. By using simple timing methods or getting additional splits with Freelap Timing, coaches can start making better training decisions by the use of meaningful data.