The velocity of motor reaction in humans or reaction time is an important physical capacity to judo competitors. During a high intensity fight, there is a considerable increase in serum lactate (SL), which is closely related to muscle fatigue. This fact may interfere in the capacity of the athlete in reacting to stressful situations during the combat. The main objective of this work is to study the role of serum lactate increases after a 1'30", 3' and 5' combat situations (Randori) in the velocity of motor reaction in high level judo competitors. Methods: For this purpose 11 healthy male competitors, 23.4 ± 2 years old, were evaluated. To record the simple reaction time, initially, immediately after combat and at the three minutes to rest, the Cybex Reactor System was employed. Serum lactate concentrations were measured by a portable lactate analyzer (Accusport). Variance analysis (Kruskal-Wallis) showed significant differences between serum lactate before, immediately after combat and at the three minutes to rest (p < 0.05) and in the velocity of motor reaction (Cybex Reactor), between the number of errors to execute the tests before and after combats (p < 0.05). A high correlation between the number of errors to execute the tests at Cybex Reactor and the lactate concentration (r = 0.9341) was observed. However, no significant differences between the motor reaction time before and after combats (p > 0.05) were found. The results demonstrate that the high serum lactate concentration does not affect the motor reaction time in high level judo competitors, indeed it suggests that there is a decrease in the reaction efficiency. This fact was demonstrated by the high correlation found between the lactate concentrations and the number of errors in the reaction tests, probably due to decreases in concentration in judo competitors to stressful situations.
BackgroundWe aimed to investigate the effect of rest interval, between successive contractions, on muscular fatigue.MethodsEighteen subjects performed elbow flexion and extension (30 repetitions) on an isokinetic dynamometer with 80º of range of motion. The flexion velocity was 120º/s, while for elbow extension we used 5 different velocities (30, 75, 120, 240, 360º/s), producing 5 different rest intervals (2.89, 1.28, 0.85, 0.57 and 0.54 s).ResultsWe observed that when the rest interval was 2.89 s there was a reduction in fatigue. On the other hand, when the rest interval was 0.54 s the fatigue was increased.ConclusionsWhen the resting time was lower (0.54 s) the decline of work in the flexor muscle group was higher compared with different rest interval duration.
A number of studies have analyzed various indices of the final position variability in order to provide insight into different levels of neuromotor processing during reaching movements. Yet the possible effects of movement kinematics on variability have often been neglected. The present study was designed to test the effects of movement direction and curvature on the pattern of movement variable errors. Subjects performed series of reaching movements over the same distance and into the same target. However, due either to changes in starting position or to applied obstacles, the movements were performed in different directions or along the trajectories of different curvatures. The pattern of movement variable errors was assessed by means of the principal component analysis applied on the 2-D scatter of movement final positions. The orientation of these ellipses demonstrated changes associated with changes in both movement direction and curvature. However, neither movement direction nor movement curvature affected movement variable errors assessed by area of the ellipses. Therefore it was concluded that the end-point variability depends partly, but not exclusively, on movement kinematics.
The design of the present study enabled the authors to distinguish between the possible effects of movement displacement and trajectory length on the pattern of final positions of planar reaching movements. With their eyes closed, 9 subjects performed series of fast and accurate movements from different initial positions to the same target. For some series, the movements were unconstrained and were therefore performed along an approximately straight vertical line. For other series, an obstacle was positioned so that trajectory length was increased because of an increase in movement curvature. Ellipses of variability obtained by means of principal component analysis applied to the scatter of movement final positions enabled the authors to assess the pattern of movement variable errors. The results showed that the orientation of the ellipses was not affected by movement displacement or by trajectory length, whereas variable errors increased with movement displacement. An increase in trajectory length as a consequence of increased curvature caused no change in variable error. From the perspective of current motor control theory, that finding was quite unexpected. Further studies are required so that one can distinguish among the possible effects of various kinematics, kinetics, and other variables that could affect the pattern of variable errors of reaching movements.
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