Affiliations: [a] Human Performance Laboratory, UNESP, Rio Claro, S.P., Brazil
Note: [] Address for correspondence: B.S. Denadai, Laboratório de
Avaliação da Performance Humana, UNESP, Av. 24 A, 1515, Bela Vista,
Rio Claro, SP, Brasil CEP – 13506-900. Tel.: +55 19 352 643 25; Fax: +55 19
352 643 21; E-mail: [email protected]
Abstract: The objective of this study was to compare the effects of high
intensity running exercise on the strength of the knee extensors at concentric
and eccentric conditions in individuals with different training background.
Sixteen physically active (SED), 11 endurance-trained (ET) and 7
strength-trained (ST) subjects volunteered to participate in the study.
Initially each subject performed, on different days, one familiarization
session on an isokinetic dynamometer and an incremental treadmill test to
volitional exhaustion to determine the velocity at the onset of blood lactate
accumulation (OBLA). The subjects then returned to the laboratory on two
experimental sessions, separated by at least five days, to perform maximal
isokinetic eccentric (E) and concentric (C) contractions of the quadriceps at
180°/s. One session was performed after a standardized
warm-up period (5 min at 50%V VO_{2}max) and the other session was performed
after a continuous running at 95% OBLA. The duration of this session was
estimated to a caloric expenditure around 500 Kcal. Following this high
intensity exercise there was a significant reduction in the peak torque in E in
all groups. The percent strength loss in E following the running exercise was
statistically higher in ST (16.5%) when compared to SED (6.5%) and ET
(7.2%). We thus conclude that the reduction in isokinetic peak torque of the
knee extensors after a session of high intensity running exercise at 95% OBLA
depends on the contraction type and training background.
