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Original articles  EXERCISE PHYSIOLOGY AND BIOMECHANICS


The Journal of Sports Medicine and Physical Fitness 2003 December;43(4):411-7

lingua: Inglese

Maximal but not submaximal performance is reduced by constant-speed 10-km run

Finni T., Kyröläinen H., Avela J., Komi P. V.

Neu­ro­mus­cular ­Research ­Center, Depart­ment of ­Biology of Phys­ical ­Activity, Uni­ver­sity of ­Jyväskylä, ­Jyväskylä, Fin­land


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Aim. ­Effects of endu­rance exer­cise on run­ning ­economy, ­mechanics, ­force gen­er­ating ­capacity and ­their inter­ac­tions ­were exam­ined. ­During the exer­cise, meta­bolic, ­kinetic and kin­e­matic var­i­ables ­were ­recorded to ­find out adap­tive mech­a­nisms in the ­course of the ­fatiguing run. In addi­tion, ­before and ­after it max­imal ­force and ­power pro­duc­tion was ­tested.
­Methods. Experi­mental ­design: com­par­a­tive. Set­ting: Uni­ver­sity. Par­tic­i­pants and inter­ven­tion: 7 men unac­cus­tomed to endu­rance ­training run 10 km at indi­vid­u­ally ­chosen con­stant ­speed (3.5±0.5 m·s-1) on an ­indoor ­track. Meas­ures: 3-D ­ground reac­tion ­forces, elec­tro­myo­graphic (EMG) activ­ities ­from 7 leg mus­cles, pul­mo­nary ven­ti­la­tion, gas ­exchange, ­heart ­rate and move­ment kin­e­matics ­were meas­ured ­during the run. ­Blood lac­tate and ­serum crea­tine ­kinase ­activity ­were deter­mined. Max­imal vol­un­tary con­trac­tion (MVC) ­with super­im­posed ­double ­twitch (DT), and pas­sive DT ­tests in plan­tar­flexor mus­cles ­were per­formed ­before and ­after the 10 km run. ­Changes in 20 m ­sprint per­for­mance ­were eval­u­ated in ­before-­after com­par­ison.
­Results. The 10 km run ­caused sig­nif­i­cant reduc­tions in max­imal run­ning ­speed (8.2 vs 7.6 m·s-1, p<0.05), in MVC (1216 vs. 984 N, p<0.05), and in pas­sive DT (271 vs 211 N, p<0.05). ­During the sub­max­imal run, how­ever, the sub­jects ­were ­able to main­tain rel­a­tively con­stant ­oxygen con­sump­tion and run­ning kin­e­matics. ­Greatest ­changes in EMG ­activity and ­kinetics ­were ­seen ­during the ­first 2 km.
Con­clu­sion. ­After ­initial adjust­ment, the run­ners are ­able to main­tain sub­max­imal run­ning ­speed ­with ­very ­little ­changes in run­ning ­economy, ­kinetics and kin­e­matics. How­ever, ­fatigue-­induced impair­ment in the ­force gen­er­ating ­capacity of the con­trac­tile com­po­nent can be ­revealed by ­tests meas­uring max­imum per­for­mance.

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