Wrist flexors are steadier than extensors.

To examine torque variability in 2 antagonistic muscles 20 individuals performed maximal and submaximal (5, 10, 20, 50 and 75% of Maximal Voluntary Contraction, MVC) isometric wrist flexions and extensions (5 s) at 5 different angles (230, 210, 180, 150 and 130°). The EMG activity of Flexor Carpi Ulnaris (FCU) and Extensor Digitorum (ED) was recorded and quantified as the integral of EMG. Participants showed higher maximal isometric torque (32.43±11.17 vs. 17.41±3.84 Nm) and lower coefficient of variability during wrist flexion compared to extension. The normalized agonist EMG increased across higher levels of torque for both wrist muscles. Interestingly, the coactivation of ED during wrist flexion was greater compared to the coactivation of FCU during wrist extension at 50 and 75% of MVC, regardless of wrist angle (f.e.: at 180° and 75% of MVC the normalised EMG of ED as antagonist was 14.84±5.18% vs. 9.33±6.94 of the FCU). It is concluded that a stronger isometric wrist flexion is more steadily produced, with greater coactivation compared to a weaker wrist extension, independently from muscle length and torque level. Even if the relative contribution of antagonists to the resultant torque is to be considered, altered activation patterns responsible for differences in force fluctuations could be suggested.

Effect of plyometric training on chair-rise, jumping and sprinting performance in three age groups of women.

AIM: The main purpose of this study was to investigate the influence of 8-wk periodized plyometric training (PT) on chair-rise, jumping and sprinting performance in three groups of women of different age (40-50; 50-60; 60-70 years). METHODS: This study involved a group of 55 women between the ages of 40 and 70 with no PT experience participating in a gymnastic program and recreational activity that did not involve jumping and who had participated since five years. All tests to determine the values of strength endurance, vertical jumping performance (VJP) and velocity were carried out before (PRE), after (POST) and following 8 weeks of rest (DETRAINING) of the 8 weeks of PT. The performance tests were completed in 3 days. RESULTS: The primary finding of this investigation indicates that low impact PT using moderate volume of jumps produced similar enhancements in the three age groups of women in jumping and chair-rise performance (30 CST) (ranging 15-24 %). There were no enhancements in 10 m-sprint time in any of the age groups. In addition, 8 weeks of detraining following an 8 week PT program resulted in similar decreases in chair-rise and jumping performance in all training groups, whereas no further changes were observed in 10-m sprint time. CONCLUSION: The low impact PT proposed appears to be an optimal stimulus for improving VJP and 30 CST during short-term training periods in untrained middle-aged and elderly women.

Short duration exhaustive aerobic exercise induces oxidative stress: a novel play-oriented volitional fatigue test.

AIM: Exercise is associated with the generation of reactive oxygen and nitrogen species. This study examined the oxidative stress in response to a novel volitional fatigue test. METHODS: Eleven male college students performed a volitional fatigue test consisting of shuttle runs with a tennis racquet in the hand towards the left and right sidelines within the tennis singles court in an attempt to hit tennis balls until exhaustion. A tennis ball serving machine was adjusted to alternate feeds to the forehand and backhand sides of the subjects, standing at the baseline, at a frequency of 20 balls per minute. RESULTS: Mean time to volitional fatigue was 5.9+/-1.3 min and mean heart rate at volitional fatigue was 189+/-8.1 beats x min(-1). The volitional fatigue test resulted in significant increases in blood thiobarbituric acid-reactive substances (22%), protein carbonyls (58%), catalase activity (143%), total antioxidant capacity (34%) and oxidized glutathione (GSSG, 81%) concentration, as well as significant decreases in reduced glutathione (GSH, 15%) concentration and GSH/GSSG ratio (56%) immediately postexercise, as compared to the pre-exercise concentration. CONCLUSION: The data provide evidence that acute short duration exhaustive aerobic exercise in the form of a novel volitional fatigue test is capable of inducing oxidative stress. This novel test could serve as an alternative exercise modality to study oxidative stress.