Michael Newton

Eccentric utilization ratio: effect of sport and phase of training.

The eccentric utilization ratio (EUR), which is the ratio of countermovement jump (CMJ) to static jump (SJ) performance, has been suggested as a useful indicator of power performance in athletes. The purpose of the study was to compare the EUR of athletes from a variety of different sports and during different phases of training. A total of 142 athletes from rugby union, Australian Rules Football, soccer, softball, and field hockey were tested. Subjects performed both CMJ and SJ on a force plate integrated with a position transducer. The EUR was measured as the ratio of CMJ to SJ for jump height and peak power. The rugby union, Australian Rules Football, and hockey athletes were tested during off-season and preseason to provide EUR data during different phases of training. For men, EUR for soccer, Australian Rules Football, and rugby was greater than softball (effect size range, 0.83–0.92). For women, EUR for soccer was greater than field hockey and softball (0.86–1.0). There was a significant difference between the jump height and peak power method for the Australian Rules Football, rugby, and field hockey tests conducted preseason (p < 0.05). For field hockey, there was a significant increase in EUR from offseason to preseason. Athletes in sports such as soccer, rugby union, and Australian Rules Football appear to have higher EUR values, which reflects the greater reliance on stretch shortening activities in these sports. It does appear that EUR can be used to track changes in training with the values significantly increasing from off-season to preseason. The EUR provides the practitioner with information about the performance of athletes and appears to be sensitive to changes in the type of training being undertaken.

Work and peak torque during eccentric exercise do not predict changes in markers of muscle damage

Objectives: Large inter-subject variability in responses to eccentric exercise has been reported. This study investigated the hypothesis that the variability of changes in indirect markers of exercise-induced muscle damage (EIMD) would be explained by work performed and/or torque generated during eccentric exercise. Methods: Subjects (nu200a=u200a53) performed 60 maximal eccentric actions of the elbow flexors on an isokinetic dynamometer that forcibly extended the elbow joint from 60° to 180° at a constant velocity (90° s−1). Markers of EIMD included maximal voluntary isometric contraction torque at 90° elbow flexion (MVC), range of motion, plasma creatine kinase activity and muscle soreness. Measurements were taken 2 days before, immediately after and 1–4 days post-exercise. Pearson’s correlation coefficient was used to examine relationships between exercise parameters (total work, change in total work, torque produced during exercise, change in peak torque) and markers of EIMD. Results: Large inter-subject variability was evident for both work and torque during exercise, and changes in all markers of EIMD. Contrary to the hypothesis, total work (normalised for individual pre-exercise MVC) did not correlate significantly with any markers of EIMD, with the exception of MVC (ru200a=u200a0.3). Total work performed and changes in total work showed higher correlations with some markers, but no r-values exceeded 0.4. Normalised exercise torque and the changes in peak torque during exercise were not correlated with changes in MVC, or other markers. Conclusion: These results suggest the large inter-subject variability in responses to eccentric exercise is not associated with work performed or torque generated during eccentric exercise.

Comparison between old and young men for responses to fast velocity maximal lengthening contractions of the elbow flexors.

Controversy exists concerning the susceptibility of elderly individuals to eccentric exercise-induced muscle damage. This study investigated the hypothesis that muscle damage induced by fast maximal lengthening contractions would be greater for old than young men. Ten old (64xa0±xa04xa0years) and young (25xa0±xa06xa0years) men performed 30 maximal voluntary lengthening contractions of the elbow flexors at an angular velocity of 210°xa0s−1. Prior to exercise, no significant differences were evident between groups for criterion measures. A significant (Pxa0<xa00.05) groupxa0×xa0time interaction was found only for isometric strength and muscle soreness with the old group showing significantly slower recovery of strength and less development of soreness compared with the young group. These results did not support the hypothesis that old men would be more susceptible to muscle damage, but confirmed a previous study reporting that recovery of muscle strength was slower for old than young individuals.

Effects of set-repetition configuration in eccentric exercise on muscle damage and the repeated bout effect

The number of eccentric contractions is a factor affecting the magnitude of muscle damage; however, it is unknown whether set-repetition configurations for the same total number of eccentric contractions affect the muscle damage. The present study investigated whether different set-repetition configurations would result in different force output during eccentric exercise and different magnitude of muscle damage following the first and second exercise bouts. Ten non-resistance-trained men (26.1xa0±xa04.1xa0years) performed two bouts of eccentric exercise of the elbow flexors of each arm (4 bouts in total). One arm performed 3 sets of 10 maximal eccentric contractions (3xa0×xa010) and the contralateral arm performed 10 sets of 3 maximal eccentric contractions (10xa0×xa03), and each arm performed 20 sets of 3 maximal eccentric contractions (20xa0×xa03) 4xa0weeks after the first bout. The order of the exercise (3xa0×xa010, 10xa0×xa03) and the use of arm (dominant, non-dominant) were counterbalanced amongst subjects. The torque produced over 30 eccentric contractions was similar between 3xa0×xa010 and 10xa0×xa03, and the changes in torque during 20xa0×xa03 were similar between arms. Maximal voluntary contraction strength, range of motion, biceps brachii cross-sectional area and muscle soreness changed significantly (Pxa0<xa00.05) following the exercise without significant differences between 3xa0×xa010 and 10xa0×xa03, and changes in the measures following 20xa0×xa03 were similar between arms, except for range of motion (ROM). No significant difference in the changes in any measures except ROM was evident when compared between the first and second bouts. These results showed that changing the set-repetition configuration had little effect on muscle damage.

The reliability of linear position transducer, force plate and combined measurement of explosive power-time variables during a loaded jump squat in elite athletes

The purpose of this study was to determine the between day reliability of power-time measures calculated with data collected using the linear position transducer or the force plate independently, or a combination of the two technologies. Twenty-five male rugby union players performed three jump squats on two occasions one week apart. Ground reaction forces were measured via a force plate and position data were collected using a linear position transducer. From these data, a number of power-time variables were calculated for each method. The force plate, linear position transducer and a combined method were all found to be a reliable means of measuring peak power (ICC = 0.87‐0.95, CV = 3.4%‐8.0%). The absolute consistency of power-time measures varied between methods (CV = 8.0%‐53.4%). Relative consistency of power-time measures was generally comparable between methods and measures, and for many variables was at an acceptable level (ICC = 0.77‐0.94). Although a number of time-dependent power variables can be reliably calculated from data acquired from the three methods investigated, the reliability of a number of these measures is below that which is acceptable for use in research and for practical applications.