I am always looking for new ideas on how to make training for road races more effective, dynamic, and lets face it more fun. One of the newer and more popular methods of increasing running speed has been the use of weighted sled towing or pulling. The idea behind the use of sled towing is that it requires the athlete pulling the sled to generate increased amounts of force to pull the sled which translates into increased explosive steps without the sled in competition. But training with added resistance can be tricky and might not work the way most coaches think that it does when it comes to generating faster speeds.
First off, running is a lot like golf with respects to the fact that both sports focus on generating a lot of power while maintaining control over the thousands of sequential movement patterns that have to happen. A good runner must not only focus on how hard he/she may be pushing through the legs but also how well they are moving through space. This is referred to as the skill of running and it is the skill of running that wins races, increases efficiency and enjoyment of running and most importantly prevents injury. This is why I say that training with added resistance can be tricky.
If a runner has not developed the required basic skills to effectively and efficiently control his/her body through the thousands of steps and reactive forces that the body encounters with running, then adding resistance will only multiply the bad habits the runner already has. Secondly, if the runner has developed the proper skills for running and begins using resistance sleds during their practices or training, and the resistance is too much then poor movement patterns may result as a substitution method to overcome the weight. Lastly, too great resistance may decrease the rate of force being developed through the low extremities.
So, is sled towing a bad idea for runners? The answer is no and that if used correctly it can be very useful. Technique must be the primary focus when advancing any training especially when it comes to running. The best rule of thumb is if the resistance you are using is causing a loss in form, then cut back on the resistance to the point where there is enough challenge for growth to be stimulated but not at the loss of skill.
In a fairly recent study of the effects of weighted sled training on athletes sprint performance the authors noted the interesting benefits and technique changes made by athletes that used heavier sleds or resistance that would slow their 10 meter time by 30% as opposed to sleds that slowed their 10 meter sprint time by 10%. They found that the athletes that used the heavier sleds increased their speed, increased their step frequency, but did not increase their step length. The lighter sled group conversely increased their step length but did not increase their step frequency. Also, at the end of the eight week study the heavier sled group increased their sprinting speed greater than the lighter sled group but not by increasing the ground reaction forces but by increasing the step frequency.
This finding was very interesting and shows the different neuromuscular adaptations the body develops to compensate for the difference in resistance. It must be noted that these were experienced athletes and skill is something that they struggle to maintain at all times while training and competing. These were also changes and adaptations that the researchers were not expecting to see. This study illustrates the ways the body will adapt to compensate for added resistance and that if an athlete is not careful the adaptations may not be what he or she was looking for. But if the you focus on skill the adaptations just might surprise you.