The increase of duration of isometric contraction may not relate to change of relative oxygenation of forearm muscle.

The aim of this study is to ascertain, how an increase in duration of isometric contraction influences tissue oxygenation of forearm muscles, undergoing physical training. Four subjects underwent 6 weeks of training of the left forearm muscles by performing isometric contractions. Subjects repeated 10 s contractions, 10-15 times in the first, and 20 s contractions in the second 3 week period. Relative oxygenation of forearm muscles was measured by using. Near Infrared Spectroscopy (CWS2000, NIM Incorporated, Philadelphia). The training increased the duration of isometric contraction at 20 kp of experimental forearm muscles by 41 +/- 25 s, which was more (P < 0.05) than in control forearm (8 +/- 4 s). This increase was not reflected in changes of maximum relative deoxygenation of experimental muscles, which decreased by only -6.9 +/- 14.4%. The results show that an increase in duration of isometric contraction may not depend on the oxygenation of muscle tissue at fixed force of 20 kp.