The influence of age on isometric endurance and fatigue is muscle dependent: a study of shoulder abduction and torso extension

Abstract

The present study examined differences in isometric muscle capacity between older (55-65 years) and younger (18 - 25 years) individuals. A total of 24 younger and 24 older participants (gender balanced within each group) performed sustained shoulder abductions and torso extensions to exhaustion at 30%, 50% and 70% of individual maximal voluntary contraction (MVC). Along with endurance time, manifestations of localized fatigue were determined based on changes in surface electromyographic signals obtained from the shoulder (middle deltoid) and the torso (multifidus and longissimus thoracis) muscles. Strength recovery was monitored using post-fatigue MVCs over a 15-min period. Compared to the younger group, older individuals exhibited lower muscular strength, longer endurance time and slower development of local fatigue. Age effects on fatigue were typically moderated by effort level, while effects of gender appeared to be marginal. Non-linear relationships between target joint torque and endurance time were observed, with effects of age differing between shoulder abduction and torso extension. Overall, the effects of age on endurance and fatigue were more substantial and more consistent for the shoulder muscle than for the torso muscles and were likely related to differences in muscle fibre type composition. For strength recovery rates, no significant age or gender effects were found in either experiment. In summary, this study suggests that differences in isometric work capacity do exist between older and younger individuals, but that this effect is influenced by effort level and the muscle tested.

Physical work capacity in older adults: Implications for the aging worker

“…Further declines of 1.0-1.5% per year generally begin in the sixth decade, and up to a 3% annual decline can occur after the age of 70 [Bellew et al, 2005;Spirduso, 2005]. There is, however, evidence that isometric endurance (at comparable levels of relative effort) is well maintained in certain muscles into the sixth decade possibly due to changes in the proportion of type I (oxidative fibers used predominantly in activities requiring endurance) and type II (glycolytic fibers used mostly in activities requiring power and speed) muscle fibers [Yassierli et al, 2007]. Decreases in isometric muscle strength will likely have the greatest impact on those working in manual labor professions, such as construction, mining or manufacturing, where heavy objects are repeatedly carried.…”

Influence of mental workload on muscle endurance, fatigue, and recovery during intermittent static work

“…After the intermittent static exertions were performed till exhaustion, participants performed a series of post-MVCs at 0, 1, 2, 5, 10, and 15 min during the recovery period. This protocol was adopted from Yassierli et al (2007) to track strength recovery trends that are generally exponential in nature.…”

“…The middle deltoid has been shown to play a dominant role during shoulder abduction at 90° ( Perotto 1994;Yassierli et al 2007) and was thus considered as the primary muscle from which EMG signals were obtained. To reduce skin resistance, the muscle sites were shaved and cleansed with alcohol, and electrodes were placed according to clinical procedures (Perotto 1994).…”

Effects of a Pilates exercise program on muscle strength, postural control and body composition: results from a pilot study in a group of post-menopausal women

“…These changes involve muscular strength (Yassierli et al 2007) and peak power output (Runge et al 2004), which appears to be related to loss of muscle mass due to an age-related factor as well as neuromuscular changes (Kim and Sapienza 2005). These contributors are all related with fall risk, that is one of the major public health issue associated with substantial healthcare costs and risk for disability, hospitalization, nursing home admission, and mortality among older adults (Patel et al 2014).…”