Muscle fatigue during intermittent isokinetic shoulder abduction: Age effects and utility of electromyographic measures

Abstract

Most existing evidence regarding the effects of age on muscular fatigue has focused on prolonged isometric contractions, repeated maximum dynamic contractions and individuals beyond traditional retirement age (>65 years). In the present study, age-related differences in muscle fatigue during submaximal dynamic efforts were examined. There were 24 younger (18-25 years) and 24 older (55-65 years) participants, all of whom were healthy and active, with equal numbers of each gender within each age group. Participants performed repetitive, intermittent shoulder abductions until exhaustion, at peak moments of 30% and 40% of individual maximum voluntary isokinetic contraction (MVIC) and with cycle durations of 20 and 40 s. Fatigue development was determined based on changes in MVIC, electromyographic (EMG) signals and ratings of perceived discomfort (RPD). Following the exhaustive exercises, strength recovery was monitored using a series of MVICs over a 15-min period. Results indicated the existence of an age-related fatigue resistance, with the older group demonstrating significantly slower rates of MVIC decline and RPD increase and smaller modifications in EMG-based fatigue measures. These age effects were generally more pronounced at the higher effort level. Main effects of effort level and cycle duration were also significant, while gender effects appeared to be marginal. Rates of strength recovery were not significantly influenced by age. In addition, the utility of standard EMG-based fatigue measures was assessed. Findings indicated that time-dependent changes in static and dynamic EMG-based measures were roughly comparable in terms of sensitivity and variability, supporting the use of standard EMG analyses for fatigue monitoring during intermittent dynamic contractions.

Acute effects of localized muscle fatigue on postural control and patterns of recovery during upright stance: influence of fatigue location and age

“…An age-associated fatigue resistance has been shown repeatedly, with older adults demonstrating less rapid declines in maximum voluntary contractions (MVC) of the ankle dorsiXexors (Lanza et al 2004) and the shoulder abductors , smaller increases in electromyographic (EMG) amplitude of the elbow Xexors (Bilodeau et al 2001), and slower declines in EMG spectral measures of the ankle dorsiXexors (Yamada et al 2000) and elbow Xexors (Merletti et al 2002) during isometric contractions. Similar Wndings have also been reported for isokinetic fatiguing exercises involving the ankle dorsiXexors (Lanza et al 2004) and shoulder abductors (Yassierli and Nussbaum 2007). Based on this and other existing evidence, it can be expected that the eVects of LMF on postural control would diVer between age groups.…”

Exertion-Dependent Effects of Physical and Mental Workload on Physiological Outcomes and Task Performance

“…EMG signals were collected using 10-mm, rectangular Ag/AgCl pre-gelled bipolar electrodes from the middle deltoid, as it has been shown to play a predominant role in shoulder abduction (Yassierli & Nussbaum, 2007), and supporting co-contractors, such as the anterior and posterior deltoid, upper trapezius, and latissimus dorsi. Muscle sites on each subject were shaved and cleansed with alcohol to reduce skin resistance, and electrodes were placed on the muscle sites according to clinical procedures (Perotto, 1994).…”

An exploration of the association between frailty and muscle fatigue

“…For example, increased muscle fatigue may limit the time that a person can stand or the number of stairs that a person can descend or ascend, leading to reduced performance in ADL. An age-related decline in muscle strength is widely reported; however, age-associated effects on muscle fatigue remain unclear (Yassierli and Nussbaum 2007).…”