Read of the WEEK!!!
“The Longitudinal Effects of Resisted Sprint Training Using Weighted Sleds vs. Weighted Vests.” Kenneth P. Clark, David J. Stearne, Cory T. Walts and Anthony D. Miller. Journal of Strength and Conditioning Research. 2010 Dec; 24(12):3287-3295.
This study investigated the effects of three different training protocols: unresisted running, running while pulling a weighted sled, and running while wearing a weighted vest. The distances measured were 18.3 meters and 54.9 meters, which are approximately 20 and 60 yards.
Short sprints are key tests that sport and strength coaches use to evaluate athletic ability. The 40-yard dash (36.6 meters) is the most popular distance in testing football players, although with the availability of more versatile and economical electronic systems, distances of 10 and 20 yards are also often tested. At football combines, the timing systems are set up so that rather than running three races at different distances, an athlete runs only a 40, and then the computer can determine his 10- and 20-yard splits.
Many track coaches and strength coaches believe that basic exercises such as squats and power cleans are not specific enough to the sprinting motion to increase running speed, especially with higher-level athletes. Therefore, many believe that the way to increase sport-specific strength for sprinting is to sprint using some sort of resistance.
In the ’60s one method tried was to wear ankle and wrist weights while running, but this negatively affected running mechanics and also placed excessive stress on the joints from having to overcome the high levels of inertia on the limbs caused by these weights. Running up hills and stadium steps was also popular, but this also was considered as having detrimental effects on running mechanics.
Efficient running mechanics takes considerable time to perfect, and this may be one reason that many sprinters don’t reach their peak performances until they are in their late 20s and early 30s. For example, Carl Lewis broke the world record in the 100 meters in 1991 at age 30 and three years later was on a team that broke the world record in the 4x200 meter relay team.
In today’s strength and conditioning environment, among the most popular methods of sport-specific strength training for improving sprint performances include running while pulling or pushing weighted sleds, wearing a weighted vest, and also towing parachutes.
The study by Clark, Stearne, Walts and Miller involved 20 male collegiate lacrosse players who were assigned to three groups: two groups of seven and one group of six. One group trained without resistance (UR), one while wearing weighted vests (WV) and one towing a weighted sled (WS). The group towing the sleds used a weight that represented 10 percent of bodyweight, and the weighted-vest group used a vest weighing 18.5 percent of bodyweight. The subjects ran twice a week and completed 13 training sessions, along with three weight training sessions per week. Pre- and post-test times were recorded in the 18.3-meter and 54.9-meter distances.
The training sessions used three primary sprint distances (18.3 meters, 36.6 meters and 54.9 meters). The following are training sessions performed during the first workout of weeks 1, 4 and 7:
Week 1 Reps x distance (rest between reps)
3 x 18.3 m (3.0 min)
2 x 36.6 m (3.5 min)
2 x 54.9 m (4.0 min)
Week 4 Reps x distance (rest between reps)
2 x 18.3 m (3.0 min)
4 x 36.6 m (3.5 min)
3 x 54.9 m (4.0 min)
Week 7 Reps x distance (rest between reps)
3 x 18.3 m (3.0 min)
3 x 36.6 m (3.5 min)
3 x 54.9 m (4.0 min)
Note the researchers, “Each training session began with a 20-minute warm-up where all subjects performed dynamic stretches, neuromuscular coordination exercises specific to sprinting, and various footwork and agility drills….The WS and WV groups completed all sprints while resisted except for the last 2 sprints of each training session (to reinforce proper sprinting technique when not resisted), whereas the UR completed all sprints without resistance.”
The authors concluded that the weighted training (WS and WV) “had no beneficial effect” compared to unresisted (UR) training. They even took this a step further by stating that for the resistances used in this study, unresisted running “may actually be superior for improving sprint performance in the 18.3- to 54.9-m interval.”
Two basic ways to increase running speed are to improve stride length and to decrease ground contact time. Both the resisted training groups showed decreases in stride length and increases in ground contact time. In contrast, the non-resisted group showed increases in stride length and decreases in ground contact time.
When looking at the results of this study, it’s important to consider that it may not be that resisted running has no value but that perhaps this specific training protocol was not the most appropriate for improving sprint performance. Here are a few problems with the workouts:
Resisted running is meant to be used to improve the drive phase of sprinting, which is usually about 20 yards, not beyond that distance (that is often regarded as the reactive phase, and which involves the athlete running with a more upright stance). The training sessions in these workouts involved distances of 20, 40 and 60 yards. Using resistance training with these distances, especially with the loads used in this study, could negatively affect optimal running mechanics.
Often resistance training is used at the beginning of a workout to create a post-tetanic training effect that stimulates the activation of the higher-threshold motor units, or at the end of a workout for a strength training effect. When you look at the concept of sport specificity, consider that with resisted running methods you will never approximate the top speeds that occur in a race. Further, the workouts for this study did not use any overspeed methods.
The resistance training sessions included two sprints without resistance at the end of every workout “to reinforce proper sprinting technique.” However, it might have been best to perform these sprints at the beginning of the workouts, because by the end of the workout the athlete is in a fatigued state so that running mechanics may not be optimal and the athlete cannot achieve top speeds.
The length of workout protocols was seven weeks with relatively the same protocols every training session. It might have been better to alternate between shorter periods of resistance and non-resistance training, such as I do in my weight training programs by alternating periods of accumulation (high volume) with periods of intensification (high intensity). It also may have been more appropriate to limit the distances with resistive training methods to no more than 20 yards.