Age-related changes in the rate of muscle activation and rapid force characteristics

Abstract

Declines in muscle size and strength are commonly reported as a consequence of aging; however, few studies have investigated the influence of aging on the rate of muscle activation and rapid force characteristics across the lifespan. This study aims to investigate the effects of aging on the rate of muscle activation and rapid force characteristics of the plantar flexors. Plantar flexion peak force (PF), absolute (peak, 50, and 100-200 ms), and relative (10 %, 30 %, and 50 %) rate of force development (RFD), the rapid to maximal force ratio (RFD/PF), and the rate of electromyography rise (RER) were examined during an isometric maximal voluntary contraction (MVC) in young (age = 22 ± 2 years), middle-aged (43± 2 years), and old (69± 5 years) men. The old men exhibited lower PF (30.7 % and 27.6 % lower, respectively) and absolute (24.4-55.1 %) and relative (16.4-28.9 %) RFD values compared to the young and middle-aged men (P≤0.03).RER values were similar between the young and old men (P≥0.30); however, RER values were greater for the middle-aged men when compared to the young and old men for the soleus (P<0.01) and the old men for the medial gastrocnemius (P≤0.02). Likewise, RFD/PF ratios were similar between young and old men (P≥0.26); however, these ratios were greater for the middle-aged men at early (P≤0.03), but not later (P≥0.10), time intervals. The lower PF and absolute and relative RFD values for the old men may contribute to the increased functional limitations often observed in older adults. Interestingly, higher rates of muscle activation and greater early RFD/PF ratios in middle-aged men may be a reflection of physiological alterations in the neuromuscular system occurring in the fifth decade.

Influence of age on passive stiffness and size, quality, and strength characteristics

“…Previous studies have demonstrated significant age-related decreases in maximal (PF or PT) and rapid (RFD or RTD) strength characteristics in older versus younger men for the leg flexors, 18 leg extensors, 18,43 plantar flexors, 44,45 and ankle dorsiflexors. 45 In this study, we also revealed lower PT and RTD in older compared with younger men for the posterior hip and thigh muscles.…”

Plantar flexor neuromuscular adjustments following match‐play football in hot and cool conditions

“…Although literature investigating the effect of fatigue on PF muscle activation capacity (and subsequent contractile RTD) is scarce (Buckthorpe et al., ; Girard et al., ), a high degree of adaptive plasticity exists for this muscle group (resistance training: Del Balso & Cafarelli, ; aging: Thompson et al., ). Given that accumulated playing time and match frequency vary during the football season, likely influencing neuromuscular fatigue characteristics of the players, whether enhancing and/or preserving maximal and explosive force production capacities through resistance training offer an advantage by improving fatigue resistance needs to be researched.…”

Dietary protein intake is associated with maximal and explosive strength of the leg flexors in young and older blue collar workers

“…RTD (Nm·s −1 ) was calculated from the linear slope of the torque – time curve at 0–50 ms (RTD50), similar to the procedures of previous studies [29,30]. This time interval was selected because it has been previously shown that the RTD within the first 50 ms may provide unique physiological information when compared to PT [8,30] or RTD at 200 ms [31,32]. The onset of contraction was determined as the point when the torque signal reached 4 Nm [29].…”