Do neuromuscular adaptations occur in endurance-trained boys and men?

Abstract

Most research on the effects of endurance training has focused on endurance training's healthrelated benefits and metabolic effects in both children and adults. The purpose of this study was to examine the neuromuscular effects of endurance training and to investigate whether they differ in children (9.0-12.9 years) and adults (18.4-35.6 years). Maximal isometric torque, rate of torque development (RTD), rate of muscle activation (Q 30 ), electromechanical delay (EMD), and time to peak torque and peak RTD were determined by isokinetic dynamometry and surface electromyography (EMG) in elbow and knee flexion and extension. The subjects were 12 endurance-trained and 16 untrained boys, and 15 endurance-trained and 20 untrained men. The adults displayed consistently higher peak torque, RTD, and Q 30 , in both absolute and normalized values, whereas the boys had longer EMD (64.7 ± 17.1 vs. 56.6 ± 15.4 ms) and time to peak RTD (98.5 ± 32.1 vs. 80.4 ± 15.0 ms for boys and men, respectively). Q 30 , normalized for peak EMG amplitude, was the only observed training effect (1.95 ± 1.16 vs. 1.10 ± 0.67 ms for trained and untrained men, respectively). This effect could not be shown in the boys. The findings show normalized muscle strength and rate of activation to be lower in children compared with adults, regardless of training status. Because the observed higher Q 30 values were not matched by corresponding higher performance measures in the trained men, the functional and discriminatory significance of Q 30 remains unclear. Endurance training does not appear to affect muscle strength or rate of force development in either men or boys.

ACL injury risk in elite female youth soccer: Changes in neuromuscular control of the knee following soccer‐specific fatigue

“…() reported significantly longer EMD values in 8–12‐year‐old children than in adults, but no significant difference between EMD in the girls compared with the boys in the youngest age group (8–12‐year‐olds). Others have found significantly longer EMD values in young boys and prepubertal girls compared with adults (Cohen et al., ; Waugh et al., ). The EMD data reported in the current study, albeit on the hamstrings during eccentric muscle actions, support this previously identified age‐related EMD difference.…”

“…Research by Cohen et al. () identified that the level of training did not have any significant effect on EMD in 9–12‐year‐olds, when comparing EMD of endurance‐trained and untrained children. The findings of the current study may challenge this lack of training effect and suggest that the number of total hours of athlete exposure may influence EMD by reducing the detrimental effects of fatigue as shown in the U17 compared with the U13 age groups.…”

“…The limited studies reporting EMD data on children have been predominantly on boys, during isometric actions and in a non‐fatigued state (Zhou et al., ; Falk et al., ; Cohen et al., ). Zhou et al.…”

The Role of Mitochondria in Generating Different Submaximal Strength and Endurance Capabilities in Elderly People

“…[1] 1) Neurophysiological, based on maximal and submaximal isometric or isotonic voluntary force, motor unit thresholds, force kinetics and endurance. [2] 2) Biochemical, for example, young people have a more glycolytic metabolism and produce higher blood lactate after maximal isometric/ isotonic contraction, and demonstrate slower utilization of muscle glycogen and blood glucose. [3] 3) Biological, in terms of expression and activation of adult stem or satellite cells during normal growth, and 4) Morphological, muscle fiber composition differs between young and elderly people.…”

The effect of heavy resistance exercise on repeated sprint performance in youth athletes

“…These characteristics can be directly influenced by the age of the participant as children possess less voluntary muscle speed, strength, and power, even when corrected for age or maturation state (Van Praagh & Dore, 2002). Likewise, children and adolescents possess less quantity of type II muscle fibres in the vastus lateralis muscle compared to adults (Lexell, Sjöström, Nordlund, & Taylor, 1992;Sjöström, Lexell, & Downham, 1992) and have a reduced ability to utilise these higher-threshold motor units (Cohen et al, 2010;Dotan et al, 2012) which are more responsive to heavy resistance exercise (Hamada, Sale, MacDougall, & Tarnopolsky, 2000;Howarth & Kravitz, 2008). The combination of these factors may influence the ability of adolescent participants to derive benefits from heavy resistance exercise.…”