Age differences in dynamic fatigability and variability of arm and leg muscles: Associations with physical function

Abstract

Introduction It is not known whether the age-related increase in fatigability of fast dynamic contractions in lower limb muscles also occurs in upper limb muscles. We compared age-related fatigability and variability of maximal-effort repeated dynamic contractions in the knee extensor and elbow flexor muscles; and determined associations between fatigability, variability of velocity between contractions and functional performance. Methods 35 young (16 males; 21.0±2.6 years) and 32 old (18 males; 71.3±6.2 years) adults performed a dynamic fatiguing task involving 90 maximal-effort, fast, concentric, isotonic contractions (1 contraction/3 s) with a load equivalent to 20% maximal voluntary isometric contraction (MVIC) torque with the elbow flexor and knee extensor muscles on separate days. Old adults also performed tests of balance and walking endurance. Results Old adults had greater fatigue-related reductions in peak velocity compared with young adults for both the elbow flexor and knee extensor muscles (P<0.05) with no sex differences (P>0.05). Old adults had greater variability of peak velocity during the knee extensor, but not during the elbow flexor fatiguing task. The age difference in fatigability was greater for the knee extensor muscles (35.9%) compared with elbow flexor muscles (9.7%, P<0.05). Less fatigability of the knee extensor muscles was associated with greater walking endurance (r=−0.34, P=0.048) and balance (r=−0.41, P=0.014) among old adults. Conclusions An age-related increase in fatigability of a dynamic fatiguing task was greater for the knee extensor compared with the elbow flexor muscles in males and females, and greater fatigability was associated with lesser walking endurance and balance.

Influence of sex on performance fatigability of the plantar flexors following repeated maximal dynamic shortening contractions

“…Although females were weaker, slower and exhibited lower rates of neuromuscular activation for the plantar flexors than males (Table 1), females were less fatigable, which is a different outcome than the limited number of reports on sex-related fatigue differences for maximal effort unconstrained shortening velocity tasks in other muscle groups (Senefeld et al 2013(Senefeld et al , 2016. The differences may be owing to muscle fibre composition or activity patterns.…”

“…Studies focusing on the elbow flexors and knee extensors suggest that both sexes demonstrate similar decrements in peak power (Senefeld et al 2013(Senefeld et al , 2016. Yoon et al (2015) reported that females were less fatigable than males during slow-velocity (~60º/s), low-resistance (20% MVC) elbow flexions until task failure.…”

“…Yoon et al (2015) reported that females were less fatigable than males during slow-velocity (~60º/s), low-resistance (20% MVC) elbow flexions until task failure. Besides differences in angular velocity, the latter study (Yoon et al 2015) used a larger work-to-rest ratio (lifting and lowering resistance over every 3 s) than Senefeld et al (2013Senefeld et al ( , 2016, where subjects performed 90 maximal effort shortening contractions (1 contraction every 3 s). For our study, participants performed a total of 200 D r a f t shortening contractions every ~1.5 s. Thus, the differences in the present study and that of Senefeld et al (2013Senefeld et al ( , 2016 may be explained by the muscle tested, number of contractions, or the work-to-rest ratio of the respective tasks.…”

“…Maximal unconstrained velocity during isotonic contractions has become an informative parameter for characterization of the fatigue-related decrements in peak power for both young (Cheng and Rice 2005, Senefeld et al 2013) and older , Senefeld et al 2016 adults. Time-dependent performance D r a f t 4 measures (i.e., rate of neuromuscular activation, rate of torque development (RTD), and rate of velocity development (RVD)) may provide key factors that fundamentally determine peak velocity and dynamic contraction performance (i.e., peak power) Aagaard 2006, Wallace et al 2016).…”

Voluntary activation and variability during maximal dynamic contractions with aging

“…Thus, our findings confirm that maximal force capacity is more preserved with advanced age in healthy adults during maximal eccentric contractions than during isometric and concentric contractions at a relatively slow-to-moderate velocity of 60°/s in the upper limb. This velocity corresponds to ~15–20% of maximal elbow flexion velocity for the young adults (~380°/s with a 20% MVIC load) and old adults (~320°/s with a 20% MVIC load) (Yoon et al 2013; Senefeld et al 2017). Furthermore, and as discussed below, because voluntary activation did not differ between contraction types, the relative preservation of the torque during eccentric contractions compared with the other contraction types with aging is likely due to muscular mechanisms.…”