Effects of a Plyometrics Intervention Program on …

1 295 Journal of Strength andConditioning Research, 2000, 14(3), 295 301q2000 National Strength &Conditioning AssociationEffects of a Plyometrics Intervention Program onSprint PerformanceEDWIN RIMMERANDGORDON SLEIVERTS chool of Physical Education, University of Otago, PO Box 56, Dunedin, New determine the Effects of a sprint -specific Plyometrics pro-gram on sprint performance, an 8-week training study con-sisting of 15 training sessions was conducted. Twenty-sixmale subjects completed the training. A Plyometrics group(N510) performed sprint -specific plyometric exercises,while a sprint group (N57) performed sprints. A controlgroup (N59) was included. Subjects performed sprints over10- and 40-m distances before (Pre) and after (Post) the Plyometrics group, significant decreases in times oc-curred over the 0 10-m (Pre seconds, Post seconds, ) and 0 40-m ( , seconds, ) distances,but the improvements in the sprint group were not signifi-cant over either the 0 10-m (Pre seconds, seconds) or 0 40-m distance (Pre , Post seconds).

2 The magnitude of theimprovements in the Plyometrics group was, however, notsignificantly different from the sprint group. The controlgroup showed no changes in sprint times. There were nosignificant changes in stride length or frequency, but groundcontact time decreased at 37 m by in the plyometricsgroup only. It is concluded that a sprint -specific plyometricsprogram can improve 40-m sprint performance to the sameextent as standard sprint training, possibly by shorteningground contact Words:sprinting, stretch-shortening cycle, train-ingReference Data:Rimmer, E., and G. Sleivert. Effects ofa Plyometrics Intervention Program on sprint Strength Cond.

3 Res. 14(3):295 301. running contributes in varying degrees tosuccessful performance in many sports. A varietyof training regimes are commonly used to improvesprinting performance, including sprint drills, over-speed training, sprinting against resistance, weighttraining, and Plyometrics . While plyometric exercisehas been used for many years, there is little evidencethat this form of training improves sprint is a type of training that develops theability of muscles to produce force at high speeds (pro-duce power) in dynamic movements; these movementsinvolve a stretch of the muscle immediately followedby an explosive contraction of the muscle.

4 This patternof muscle contraction is known as the stretch-shortencycle (SSC) (12). Plyometric exercises include verticaljumps, during which the athlete jumps as high as pos-sible on the spot, and bounds, during which the ath-lete leaps as high and as far as possible, thus movingthe body in the horizontal and vertical planes. It isgenerally accepted that the more specific a training ex-ercise to a competitive movement, the greater thetransfer of the training effect to performance (6, 13).Athletes such as sprinters, who require power for mov-ing in the horizontal plane, engage in bounding ply-ometric exercises, whereas athletes such as high jump-ers and volleyball players, who require power to beexerted in the vertical direction,train using verticaljumping exercises (4, 15).

5 Although athletes and coach-es involved in sprint training continue to use plyomet-ric exercises (6, 11), there are few data describing thetransfer of the training Effects from plyometric train-ing in the horizontal plane to sprint performance inthe acceleration phases of a findings from the small number of studies inthe literature regarding the Effects of Plyometrics onsprinting are not consistent. Results showing no im-provements in sprint times as a result of a plyometricsintervention Program have been reported (7, 8, 16).The plyometric exercisesemployed in these studieswere not specific to sprinting, however, and the lackof specificity of the exercises to sprinting may havebeen responsible for the absence of improvements insprint times.

6 On the other hand, improvements in 10-and 100-m sprint times have been found after a train-ing Intervention that incorporated some sprint -specificplyometric exercises (6). It is unclear, however, wheth-er the reported improvement in sprinting from thisstudy was a result of the sprint training, the plyomet-rics, or a combination of both training types. Addi-tionally, no data were provided regarding the changesin stride length, stride frequency, or ground contacttime, which may have accounted for the changes in296 Rimmer and Sleivertsprint performance. Thus, there is a lack of evidencefor the Effects of a sprint -specific plyometric interven-tion Program on sprint performance.

7 Accordingly, thepurpose of the present investigation was to determinethe effect of a sprint -specific plyometric interventionprogram compared with a sprint -training interventionprogram on sprint performance. It was hypothesizedthat plyometric training would improve accelerationover the first 20 m of a 40-m sprint to a greater extentthan standard sprint training, due to a specificity oftraining response, because ground contact times dur-ing sprinting and Plyometrics would be most similarduring the early acceleration phase, but ground reac-tion forces would be higher in Plyometrics healthy males (mean6SD: age 2464years; height, m; and weight, 83610 kg)with no recent history of plyometric training gavetheir written informed consent to participate in thisstudy.

8 Ethical approval had first been obtained fromthe University s ethics committee. Of the 32 subjectsselected, 6 failed to complete thetraining Program ortesting procedures because of injuries sustained as aresult of participation in other activities. The 26 re-maining subjects were either rugby (n522) or touchrugby players (n54) who played at either the under-21 (n55) or senior (n521) levels. The rugby playersplayed in back line or loose forward positions. Subjectsperformed preliminary 40-m sprints and only thosewho achieved times of less than 6 seconds were per-mitted to participate in this sprinttime was selected to ensure subjects were at least av-erage DesignSubjects were randomly allocated to the Plyometrics , sprint , or control group and the number of subjects ineach of these groups at the conclusion of the study was10, 9, and 7 respectively.

9 Subjects in the plyometricsand sprint groups took part in 2 training sessions perweek during all weeks in the Intervention apart fromweek 4, during which only 1 session was conductedbecause of the unavailability of most subjects duringthis week. Testing procedures were conducted on 2occasions prior to commencingtraining, and on 2 oc-casions following the conclusion of the first of the pretraining testing sessions was a fa-miliarization session in which subjects performed thewarm-up procedures and sprint tests as detailed be-low. At the second testing session, pretraining datawere collected. The pretraining testing session, the fa-miliarization session, and the commencement oftrain-ing were separated by 3 days to ensure full participated in the testing procedures on 2occasions within a 2-week period following the finaltraining session.

10 Theresults used in the analysis werethose from the day in which the fastest average timeswere recorded. At least 2 days separated the last train-ing day and the first of the posttesting sessions, andat least 2 days separated the 2 posttraining testing subjects performed a standardized warm-up priorto performing the sprint tests. Subjects jogged for a10-minute period at a moderate pace. Subjects thenperformed stretches with which they were familiar forapproximately 5 minutes. The warm-up was conclud-ed by the performance of 2 40-m submaximal runs(approximately 80% of maximum perceived sprintspeed) along the running TestsSubjects performed 3 6 maximal effort sprints overdistances of 10 and 40 m.