Differences in strength and surface electromyogram characteristics between pre-pubertal gymnasts and untrained boys during brief and maintained maximal isometric voluntary contractions (original) (raw)
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Rate of muscle activation in power- and endurance-trained boys
International journal of sports physiology and performance, 2011
Previous studies in adults have demonstrated power athletes as having greater muscle force and muscle activation than nonathletes. Findings on endurance athletes are scarce and inconsistent. No comparable data on child athletes exist. This study compared peak torque (Tq), peak rate of torque development (RTD), and rate of muscle activation (EMG rise, Q30), in isometric knee extension (KE) and flexion (KF), in pre- and early-pubertal power- and endurance-trained boys vs minimally active nonathletes. Nine gymnasts, 12 swimmers, and 18 nonathletes (7-12 y), performed fast, maximal isometric KE and KF. Values for Tq, RTD, electromechanical delay (EMD), and Q30 were calculated from averaged torque and surface EMG traces. No group differences were observed in Tq, normalized for muscle cross-sectional area. The Tq-normalized KE RTD was highest in power athletes (6.2 ± 1.9, 4.7 ± 1.2, 5.0 ± 1.5 N·m·s-1, for power, endurance, and nonathletes, respectively), whereas no group differences were ...
Explosive sport training and torque kinetics in children
Applied Physiology, Nutrition, and Metabolism, 2013
A high rate of force development (RFD) is often more important than maximal force in daily and sports activities. In children, resistance training has been shown to increase maximal force. It is unclear whether, or to what extent, can children improve RFD and force kinetics. For this study, we compared strength and force kinetics of boy gymnasts with those of untrained boys and untrained men. Eight boy gymnasts (age, 9.5 ± 1.2 y), 20 untrained boys (age, 10.1 ± 1.3 y), and 20 untrained men (age, 22.9 ± 4.4 y) performed maximal, explosive, isometric elbow flexions (EF) and knee flexions (KF). Peak torque (maximal voluntary contraction (MVC)), elapsed times to 10%-100% MVC, peak rate of torque development (RTD pk ), and other kinetics parameters were determined. When gymnasts were compared with untrained boys, size-normalized EF MVC was 11%-20% higher, RTD pk was 32% higher, and times to 30% and 80% MVC were 16% and 55% shorter, respectively (p < 0.05). No corresponding differences were observed in KF. Furthermore, although the normalized EF MVC was 28% lower in gymnasts than in men (p < 0.001), their torque kinetics parameters were similar. These findings highlight the specificity of gymnastics training, which markedly elevated the torque kinetics of young, prepubertal boys to adult levels, but only moderately affected peak torque. It is suggested that neurologic adaptations, such as enhanced firing and activation rates or increased type II motor-unit recruitment, as well as changes in musculotendinous stiffness, could explain these findings.
Pediatric exercise science, 2014
In a previously published review article, Dotan et al , proposed the hypothesis of a differential motor-unit (MU) activation in children to account for many observed childadult differences (ie, maximal strength, rate of force development, fatigue resistance, metabolic profile, and responses to training). Specifically, these authors pointed to Type II MU utilization as "being the compromised portion of children's muscle function." This review was previously commented on by Bassa et al and O'Brien et al (25). In this comment, we propose to contribute to the ongoing debate on this topic. In particular, we will approach the question of MU recruitment from a methodological point of view to sum up our current knowledge and to identify the methodological steps that must be done to move forward on this topic.
Applied Physiology, Nutrition, and Metabolism, 2009
Muscle strength and activation were compared in boys and men during maximal voluntary elbow flexion and extension contractions. Peak torque, peak rate of torque development (dτ/dτmax), rate of muscle activation, and electromechanical delay (EMD) were measured in 15 boys (aged 9.7 ± 1.6 years) and 16 men (aged 22.1 ± 2.8 years). During flexion, peak torque was significantly lower in boys than in men (19.5 ± 5.8 vs. 68.5 ± 11.0 Nm, respectively; p < 0.05), even when controlling for upper-arm cross-sectional area (CSA), and peak electromyography activity. Boys also exhibited a lower normalized dτ/dτmax (7.2 ± 1.7 vs. 9.5 ± 1.6 (Nm·s–1)·(Nm–1), respectively; p < 0.05) and a significantly longer EMD (75.5 ± 28.4 vs. 47.6 ± 17.5 ms, respectively). The pattern was similar for extension, except that group differences in peak torque were no longer significant when normalized for CSA. These results suggest that children may be less able to recruit or fully utilize their higher-threshold...
Sport Sciences for Health, 2022
We have previously demonstrated the relation between the biological maturation (BM) and the power of both upper (ULP) and lower limbs (LLP) in young athletes. We have also observed that the BM has a higher influence on the ULP, and the LLP is more prone to changes in hormonal and morphological factors. However, we have not yet compared the power of upper limbs and lower limbs in relation to the BM stage to verify whether the BM exerts more relation on the muscle power of a segment of the body. To attend this question, in this transverse study we have analyzed the relative muscle power from 241 young athletes (male: 57%, female: 43%, 12.3 ± 1.7 years) in relation to the BM stages of-delayed, synchronized and advanced. The ULP was verified by the medicine ball test and the LLP was verified by jump test in strength platform. Measures were standardized in Watts. The ULP was superior than LLP when individuals were at the late (male: p < 0.0001, female: p < 0.0001), or synchronized (male: p < 0.000, female: p = 0.0003) stages of BM, whereas no differences were found when the individuals were at the advanced stage of BM (male: p = 0.3, female: p = 0.3). Athletes at the late or synchronized stages of BM display of a higher power of superior compared inferior limbs. It is concluded that biological maturation has a greater relationship with the power of the upper limbs when compared to the lower limbs.
Force-velocity relationship profile of elbow flexors in male gymnasts
PeerJ
Background The theoretical maximum force (F0), velocity (V0), and power (Pmax) of athletes calculated from the relationship between force and velocity (F-V relationship) and the slope of the F-V relationship, reflect their competitive and training activity profiles. Evaluating the F-V relationship of athletes facilitates categorizing the profiles of dynamic muscle functions in relation to long-term sport-specific training. For gymnastics, however, no studies have tried to examine the profiles of F-V relation and power output for upper limb muscles in relation to the muscularity, while the use of the upper extremities in this sport is very unique as described earlier. Purpose It was hypothesized that the F-V relationship of the elbow flexion in gymnasts might be characterized by low capacity for generating explosive force, notably in terms of the force normalized to muscle size. Methods The F0, V0, and Pmax derived from the force-velocity relationship during explosive elbow flexion a...
Relationship between maximal rate of force development and maximal voluntary contraction
The aim of this research was to examine relationships between the maximal rate of force development (MRFD) expressed in absolute and relative values and the maximal voluntary contraction (MVC) in the knee and elbow flexors and extensors. The sample consisted of thirty male PE students. Eight measuring sessions were performed using the BIODYNA dynamometer. During maximal isometric contraction of the knee and elbow flexors and extensors MVC and MRFD were recorded. The results showed that the relationship between MVC and MRFD is dependent on the expression of the MRFD. Regardless of the studied muscle group, there were significant correlations between MVC and MRFD [Nm/s]. When MRFD was expressed in relative values [%MVC/s] the relationships between its parameters were not significant. Due to the significant influence of the MVC level on MRFD expressed in absolute values, it may be more appropriate to use MRFD expressed in relative values for the assessment of muscle contractile propert...
Muscle activation of a sportsman and an untrained man
Journal of Human Sport and Exercise, 2016
The research was focused to analyse the muscle activation using sEMG during repeated physical activity. The purpose of this study was to find out differences between a sportsman and an untrained man in the timing of muscle activation during increasing load. Two men took part in the research. The untrained man (MN) 20 years old, 180 cm, 74 kg, sportsman (MS) 22 years old, 177 cm, 87 kg. Participants performed repeated flexion and extension in the elbow joint. Muscle activation has been tested using sEMG on the selected muscles: biceps brachii (BB), brachioradialis (B), trapezius p. descendez (TD), deltoideus p. acromialis (DA). Both participants performed test for 5, 8 and 12 kg load. Number of repetition was 10. In flexion, the time of muscle activations were the same or very similar for BB for both participants and longer in MN for B and DA, for TD were longer in MS for all loads. Differences were caused firstly by a different finishing time. In extension DA and B in MN, partly also TD were activated for a longer time. The time for activation of BB was mostly the same. Differences were caused mainly by the later start of the activation in MS. Also tendencies in prolonging and shortening the time of activation in relation to increasing load in both participants demonstrated different characteristics. Significantly longer time of muscle activation of MN has been proved only for B and DA for both kinds of movements. Differences between participants in the total time of activation at absolutely same load were expected especially because of the better movement efficiency, adaptation to the power load and movement technique in MS.
The research has been carried out in order to measure the variability of the development of muscle force control achieved by the arms extensor muscle within the task requirements. The experiment involved testing the arm extensor muscle by using the isometric Flat Bench Press Test. The sample consisted of 28 subjects who were students of the College of Internal Affairs in Zemun-Belgrade. The subjects had underwent five individual test trials, within which the first trial measured the maximum isometric muscle force (F max izo) and in the other four cases depended on the acquired percentage of F max izo at the levels of 30%, 50%, 70% and 90%. The testing was developed by using a hardware-software system applied in the Special Physical Education Laboratory at the College of Internal Affairs. The variability differences among the observed variables were measured by implementing the ANOVA variance analysis, Kandall′s and Wilcoxon′s Test. In order to establish the differences among individual variables, the Student′s t-test of equal samples was used. The ANOVA results showed a statistically significant difference between the mean values and variability among all of the observed variables at the F = 6.065, p = 0.001 level, in relation to the absolute values and F = 9.956, p = 0.000 and in relation to relative force values. The results of the Student′s t-test showed a statistically significant difference among the mean value of errors in the developed force between the level of 30 percent (as the smallest force of the level tested) and all the other levels of 50%, 70% and 90% (as the middle, large and submaximum level of force). Kandall′s test showed that the error distribution, that is, the level of force deviation from the force level required by the task, differs from the aspect of absolute and the aspect of relative values (values in percents) at the p = 0.000 level. According to the results, it can be concluded that in regards to the control of muscle force distribution as part of the task, a healthy and untrained male population mostly makes errors in the sense of a low level of force (at
Rapid Force Production in Children and Adults
Medicine & Science in Sports & Exercise, 2013
Purpose: Children demonstrate lower force production capacities compared with adults, which has often been attributed to ''neuromuscular immaturity.'' However, tendon stiffness, which influences both the electromechanical delay (EMD) and rate of force development (RFD) in adults, is lower in children and may influence rapid force production. The aims of this study were 1) to document EMD and RFD variation as a function of age, 2) to determine the relationships between tendon stiffness and parameters relating to rapid force production in children and adults, and 3) to estimate the relative neural and mechanical contributions to age-related changes in force production by examining the effects of tendon stiffness and muscle activation rate (rate of EMG increase [REI]) on RFD. Methods: Achilles tendon stiffness, EMD, RFD, and REI were measured during plantarflexion contractions in 47 prepubertal children (5-12 yr) and 19 adults. Relationships were determined between 1) stiffness and EMD, 2) stiffness and RFD, and 3) REI and RFD. The relative contributions of age, stiffness, and REI on RFD were determined using a multiple regression analysis. Age-related differences in tendon stiffness, EMD, RFD, and REI were also examined according to chronological age (5-6, 7-8, and 9-10 yr) and compared with adults. Results: Increases in tendon stiffness with age were correlated with decreases in EMD (r G j0.83). Stiffness and REI could account for up to 35% and 30% of RFD variability in children, respectively, which increased to 58% when these variables were combined. Conclusions: Both neural and mechanical factors influence rapid force production in prepubertal children. Children's longer EMD and slower RFD indicate a less effective development and transfer of muscular forces, which may have implications for complex movement performance.