HOW EFFECTIVE IS SPRINT-RESISTED TRAINING
Resistance during the sprinting action in the form of weighted body suits (pants, shirts), sleds, parachutes, stretch cords, head winds, and staircase sprinting is commonly used in team sports. Studies examining the effects of such training on speed have revealed conflicting results and a number of concerns remain unanswered and are in need of attention by researchers.
The suitability of sprint-resisted training for young athletes has not been determined. Shepherd (2004) concluded that the technique be limited to physically mature athletes who exhibit sound sprinting technique. His conclusions were based on concerns for the biomechanical changes that resistance imposes on the athlete (Knicker 1994), and the possibility of reduced performance from these changes carrying over to the sprint biomechanics used during competition.
The exact percent of a total sprint workout that should be devoted to sprintresisted training is unknown. A low number of repetitions is recommended with adequate rest between each to avoid the possibility of producing technique errors that may become permanent.
The fundamental philosophy behind resisted sprinting needs to be reexamined. Since the resistance load increases ground contact time, increases knee flexion during the foot-strike, and increases forward lean, the specificity of the resisted load may be negated.
The following considerations have been proposed by Shepherd:
• Resisted sprinting should be used sparingly to avoid permanent changes in sprint mechanics; coaches should monitor sprint kinematics to avoid imposing unwanted changes on sprint running technique during team sport play.
• Resisted sprinting should not be used with prepubescent athletes since sound sprinting form may not been mastered at this stage. Training to increase ground contact force can occur from general strength training methods.
• Coaches may choose to experiment with different methods of resisted sprinting such as using a slight headwind as resistance which allows athletes to train with more appropriate technique since resistance is imposed across the entire frontal surface area rather than as an attachment that loads a specific point of the body.
• Sports that require sprinting against external forces such as football, rugby, bobsledding, and others can devise sport specific movements to replicate the situation. For example, a bobsled athlete, rugby forward, and interior linemen in football could push an automobile or specific apparatus rather than towing a sled.
The NASE uses sprint-resisted training to accomplish two objectives:
1. to improve late acceleration and maximum sprinting speed. This requires light resistance that does not alter sprinting mechanics or increase ground contract time. One variation involves the use of flying starts with no resistance before light resistance is applied for 10-20 yards when an athlete reaches near maximum speed.
2. to improve the start and early acceleration by increasing ground contact force in the muscles involved in these two phases of sprinting. During these phases, ground contact time is higher than at any other time during an all-out sprint. The use of the heavy resistance needed to increase ground contact force will also increase ground contact time each repetition. The key is to find the heaviest weight an athlete can handle that produces the least reduction in ground contact time. The most important role for sprint-resisted training may lie in this area. The early Virginia Commonwealth University (VCU) studies support the findings of Vick (1995) who tested 18 high school males on a FORCE treadmill (non motorized with athlete propelling the belt while tethered from behind). The treadmill allowed a constant resistance force of 1 to 150 lb. in 1 lb. increments to be applied through a braking mechanism. Each 35 minute training session consisted of a standard dynamic warmup, build-up sprints, in-and-outs, resisted acceleration sprints, and a stretching cooldown.
A battery of standard field tests were used to measure performance in control and experimental subjects: vertical jump, 10-yd, 40-yd, and 100-yd sprints, and the Pro Agility Test. Subjects in both groups used the same 20-minute warm-up (dynamic plus specific warm-up of progressive squats and sprints).
The experimental group made significant improvement in all performance areas following a 4-week training period whereas the control group showed no improvement. As in the VCU studies, the greatest improvement occurred in the shorter distances (start and acceleration phase).
Knicker, A. J. 1994, Untersuchungen zur ubereinstimmung von zugwiderstandslaufen und sprintbewegungen, paper presented at the Widerstandbelastungen im Schneligkeitstraining, Koln,
Shepherd, J 2004, ‘The use of resisted and assisted training methods for speed development: coaching considerations, Modern Athlete and Coach, 42(4), pp. 9–13.
Vick, K. 1995. Relationship between strength qualities and sprinting performance. J Sports Med. Phys. Fit. 35:13-9.
SOURCE: National Association of Speed and Explosion, Sports Speed News Bulletin Volume 5, Issue 23 (July, 2009) Exerpts from: The Encyclopedia of Sports Speed: Improving Playing Speed for Sports Competition, by George B. Diintiman and Robert Ward, ©2011