Greater motor unit discharge rate during rapid contractions in chronically strength-trained individuals.

Though similar motor unit (MU) discharge properties have been observed during slow sustained contractions between chronically strength-trained (ST) and untrained (UT) individuals, it is currently unknown whether differences between these groups exist for when maximal in vivo MU discharge rate is assessed during rapid, maximal rate of force development (RFD) contractions. Therefore, we compared MU discharge characteristics and RFD during rapid contractions in chronic ST and UT individuals. The investigations were performed in two independent cohorts of chronically ST men, with trained elbow flexors (, = 13, 6 ± 4 yr of training experience) or knee extensors (, = 11, 9 ± 4 yr of experience), and compared with those of UT ( = 12 and = 10, respectively).

Contextualised physical metrics: The physical demands vary with phase of play during elite soccer match play.

The physical demands of elite soccer match play have traditionally been measured using aggregated whole-match metrics. However, match play is increasingly considered as distinct phases of play, although the influence of phase of play on match physical demands remains largely unknown. This study compared physical intensity, acceleration and deceleration demands, between phases of play and according to playing position.

Muscle and tendon morphology of a world strongman and deadlift champion.

This study compared the muscle and tendon morphology of an extraordinarily strong individual, a World's Strongest Man and deadlift champion (WSM), with that of various other athletic, trained, and untrained populations. The WSM completed the following: ) 3.0-T MRI scans, to determine the volume of 22 individual lower limb muscles, 5 functional muscle groups, patellar tendon (PT) cross-sectional area (CSA), and PT moment arm; and ) countermovement jumps (CMJ) and isometric midthigh pull (IMTP) contractions.

How Humans Run Faster: The Neuromechanical Contributions of Functional Muscle Groups to Running at Different Speeds.

How the neuromechanics of the lower limb functional muscle groups change with running speed remains to be fully elucidated, with implications for our understanding of human locomotion, conditioning, and injury prevention. This study compared the neuromechanics (ground reaction and joint kinetics, kinematics and muscle activity) of middle-distance athletes running on an instrumented treadmill at six wide-ranging speeds (2.78-8.

Smaller Biceps Femoris Aponeurosis Size in Legs with a History of Hamstring Strain Injury.

Biceps femoris long head (BF) aponeurosis size was compared between legs with and without prior hamstring strain injury (HSI) using two approaches: within-group (injured vs. uninjured legs of previous unilateral HSI athletes) and between-group (previously injured legs of HSI athletes vs. legs of No Prior HSI athletes).

Long-Term Resistance Trained Human Muscles Have More Fibers, More Myofibrils, and Tighter Myofilament Packing Than Untrained.

Introduction: Increases in skeletal muscle size occur in response to prolonged exposure to resistance training that is typically ascribed to increased muscle fiber size. Whether muscle fiber number also changes remains controversial, and a paucity of data exists about myofibrillar structure. This cross-sectional study compared muscle fiber and myofibril characteristics in long-term resistance-trained (LRT) versus untrained (UNT) individuals.

Durability of Running Economy: Differences between Quantification Methods and Performance Status in Male Runners.

Introduction: Running economy (RE) deteriorates during prolonged running, although the effect of measuring energy cost (EC) or oxygen cost (OC) on the magnitude of these changes has not been investigated. Similarly, it is unknown if runners' performance level may influence the deterioration of RE during prolonged running. The aims of this study were to compare changes in EC and OC measurements of RE during a prolonged run in a large cohort of well-trained male runners, and to compare changes between runners of high- and low-performance standard.

Sex differences in muscle morphology between male and female sprinters.

There is a marked difference between males and females in sprint running performance, yet a comprehensive investigation of sex differences in the muscle morphology of sprinters, which could explain the performance differences, remains to be completed. This study compared muscle volumes of 23 individual leg muscles and 5 functional muscle groups, assessed with 3 T magnetic resonance imaging, between male ( = 31) and female ( = 22) sprinters, as well as subgroups of elite males (EM, = 5), elite females (EF, = 5), and performance-matched (to elite females) males (PMM, = 6). Differences in muscle volume distribution between EM, EF, and unathletic male (UM) controls were also assessed.

Evidence for a new model of the complex interrelationship of ball possession, physical intensity and performance in elite soccer.

Background: How the physical metrics, especially physical intensity, and possession interact with each other, and subsequently combine to influence performance remains opaque. Therefore, we investigated the interrelationship of possession, physical metrics, and team performance in elite soccer.

Methods: Four seasons of a top European league were used to derive 80 team league performances (points), together with possession and physical data.

The Effect of Specific Bioactive Collagen Peptides on Tendon Remodeling during 15 wk of Lower Body Resistance Training.

Purpose: Collagen peptide supplementation has been reported to enhance synthesis rates or growth in a range of musculoskeletal tissues and could enhance tendinous tissue adaptations to resistance training (RT). This double-blind placebo-controlled study aimed to determine if tendinous tissue adaptations, size (patellar tendon cross-sectional area (CSA) and vastus lateralis (VL) aponeurosis area), and mechanical properties (patellar tendon), after 15 wk of RT, could be augmented with collagen peptide (CP) versus placebo (PLA) supplementation.

Methods: Young healthy recreationally active men were randomized to consume either 15 g of CP ( n = 19) or PLA ( n = 20) once every day during a standardized program of lower-body RT (3 times a week).

The effect of a prior eccentric lowering phase on concentric neuromechanics during multiple joint resistance exercise in older adults.

Aging involves a marked decline in physical function and especially muscle power. Thus, optimal resistance exercise (RE) to improve muscle power is required for exercise prescription. An eccentric lowering phase immediately before a concentric lift (ECC-CON) may augment concentric power production, due to various proposed mechanisms (e.

The influence of ball in/out of play and possession in elite soccer: Towards a more valid measure of physical intensity during competitive match-play.

The physical demands of soccer match-play have typically been assessed using a low-resolution whole match approach ignoring whether the ball is in or out of play (BIP/BOP) and during these periods which team has possession. This study investigated the effect of fundamental match structure variables (BIP/BOP, in/out of possession) on the physical demands, and especially intensity, of elite match-play. For 1083 matches from a major European league, whole match duration, and player physical tracking data, were divided into BIP/BOP, and in/out of possession periods throughout the match, using on-ball event data.

Non-invasive estimation of muscle fibre size from high-density electromyography.

Because of the biophysical relation between muscle fibre diameter and the propagation velocity of action potentials along the muscle fibres, motor unit conduction velocity could be a non-invasive index of muscle fibre size in humans. However, the relation between motor unit conduction velocity and fibre size has been only assessed indirectly in animal models and in human patients with invasive intramuscular EMG recordings, or it has been mathematically derived from computer simulations. By combining advanced non-invasive techniques to record motor unit activity in vivo, i.

Motor Unit Discharge Characteristics and Conduction Velocity of the Vastii Muscles in Long-Term Resistance-Trained Men.

Purpose: Adjustments in motor unit (MU) discharge properties have been shown after short-term resistance training; however, MU adaptations in long-term resistance-trained (RT) individuals are less clear. Here, we concurrently assessed MU discharge characteristics and MU conduction velocity in long-term RT and untrained (UT) men.

Methods: Motor unit discharge characteristics (discharge rate, recruitment, and derecruitment threshold) and MU conduction velocity were assessed after the decomposition of high-density electromyograms recorded from vastus lateralis (VL) and vastus medialis (VM) of RT (>3 yr; n = 14) and UT ( n = 13) during submaximal and maximal isometric knee extension.

The effect of specific bioactive collagen peptides on function and muscle remodeling during human resistance training.

Aim: Bioactive collagen peptides (CP) have been suggested to augment the functional, structural (size and architecture), and contractile adaptations of skeletal muscle to resistance training (RT), but with limited evidence. This study aimed to determine if CP vs. placebo (PLA) supplementation enhanced the functional and underpinning structural, and contractile adaptations after 15 weeks of lower body RT.

The Muscle Morphology of Elite Female Sprint Running.

Introduction: A paucity of research exists examining the importance of muscle morphological and functional characteristics for elite female sprint performance.

Purpose: This study aimed to compare lower body muscle volumes and vertical jumping power between elite and subelite female sprinters and assess the relationships of these characteristics with sprint race and acceleration performance.

Methods: Five elite (100 m seasons best [SBE 100 ], 11.

Neural decoding from surface high-density EMG signals: influence of anatomy and synchronization on the number of identified motor units.

High-density surface electromyography (HD-sEMG) allows the reliable identification of individual motor unit (MU) action potentials. Despite the accuracy in decomposition, there is a large variability in the number of identified MUs across individuals and exerted forces. Here we present a systematic investigation of the anatomical and neural factors that determine this variability.

Startling stimuli increase maximal motor unit discharge rate and rate of force development in humans.

Maximal rate of force development in adult humans is determined by the maximal motor unit discharge rate, however, the origin of the underlying synaptic inputs remains unclear. Here, we tested a hypothesis that the maximal motor unit discharge rate will increase in response to a startling cue, a stimulus that purportedly activates the pontomedullary reticular formation neurons that make mono- and disynaptic connections to motoneurons via fast-conducting axons. Twenty-two men were required to produce isometric knee extensor forces "as fast and as hard" as possible from rest to 75% of maximal voluntary force, in response to visual (VC), visual-auditory (VAC; 80 dB), or visual-startling cue (VSC; 110 dB).

Fast and ballistic contractions involve greater neuromuscular power production in older adults during resistance exercise.

Purpose: Neuromuscular power is critical for healthy ageing. Conventional older adult resistance training (RT) guidelines typically recommend lifting slowly (2-s; CONV), whereas fast/explosive contractions performed either non-ballistically (FAST-NB) or ballistically (FAST-B, attempting to throw the load) may involve greater acute power production, and could ultimately provide a greater chronic power adaptation stimulus. To compare the neuromechanics (power, force, velocity, and muscle activation) of different types of concentric isoinertial RT contractions in older adults.

The Influence of a Competitive Field Hockey Match on Cognitive Function.

Despite the known positive effects of acute exercise on cognition, the effects of a competitive team sport match are unknown. In a randomized crossover design, 20 female and 17 male field hockey players (19.7 ± 1.

Effect of long-term maximum strength training on explosive strength, neural, and contractile properties.

The purpose of this cross-sectional study was to compare explosive strength and underpinning contractile, hypertrophic, and neuromuscular activation characteristics of long-term maximum strength-trained (LT-MST; ie, ≥3 years of consistent, regular knee extensor training) and untrained individuals. Sixty-three healthy young men (untrained [UNT] n = 49, and LT-MST n = 14) performed isometric maximum and explosive voluntary, as well as evoked octet knee extension contractions. Torque, quadriceps, and hamstring surface EMG were recorded during all tasks.

Behavior of motor units during submaximal isometric contractions in chronically strength-trained individuals.

Neural and morphological adaptations combine to underpin the enhanced muscle strength following prolonged exposure to strength training, although their relative importance remains unclear. We investigated the contribution of motor unit (MU) behavior and muscle size to submaximal force production in chronically strength-trained athletes (ST) versus untrained controls (UT). Sixteen ST (age: 22.