Exerting force at the maximal speed drives the increase in power output in elite athletes after 4 weeks of resistance training.

Purpose: In the present study, we examined how a 4-week intervention of maximal intended velocity (MIVRT) and controlled velocity resistance training (CRT)-induced task-specific responses in expert individuals.

Methods: Twenty elite athletes were randomly assigned to either a MIVRT (n = 10) or CRT (n = 10) group, both following the same volume-load training based on the back-squat three times a week but with different intentions in moving load (force-exertion speed). We assessed one-repetition maximum (1RM), mean propulsive velocity (MPV), and mean propulsive power (MPP) using a progressive-loading test before and after the intervention.

Characterising sex-related differences in lower- and higher-threshold motor unit behaviour through high-density surface electromyography.

Emerging questions in neuromuscular physiology revolve around whether males and females share similar neural control in diverse tasks across a broad range of intensities. In order to explore these features, high-density electromyography was used to record the myoelectrical activity of biceps brachii during trapezoidal isometric contractions at 35% and 70% of maximal voluntary force (MVF) on 11 male and 13 female participants. Identified motor units were then classified as lower-threshold (recruited at ≤30%MVF) and higher-threshold (recruited at >30%MVF).

Ventilation and perceived exertion are sensitive to changes in exercise tolerance: arm+leg cycling vs. leg cycling.

Growing evidence suggests that respiratory frequency ( ) is a marker of physical effort and a variable sensitive to changes in exercise tolerance. The comparison between arm+leg cycling (Arm+leg) and leg cycling (Leg) has the potential to further test this notion because a greater exercise tolerance is expected in the Arm+leg modality. We systematically compared Arm+leg vs.

Adjustments in the motor unit discharge behavior following neuromuscular electrical stimulation compared to voluntary contractions.

The application of neuromuscular electrical stimulation superimposed on voluntary muscle contractions (NMES+) has demonstrated a considerable potential to enhance or restore muscle function in both healthy and individuals with neurological or orthopedic disorders. Improvements in muscle strength and power have been commonly associated with specific neural adaptations. In this study, we investigated changes in the discharge characteristics of the tibialis anterior motor units, following three acute exercises consisting of NMES+, passive NMES and voluntary isometric contractions alone.

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.

The fiscal response to the Italian COVID-19 crisis: A counterfactual analysis.

The COVID-19 pandemic is an unprecedented worldwide event with a massive impact on the economic system. The first Western country that had to face the COVID-19 crisis was Italy, which therefore represents a natural "case study." By using the microdata and granular policy information available at the Italian Ministry of Economy and Finance, this paper provides a macroeconomic quantitative assessment of the initial emergency fiscal measures introduced in 2020 and an analysis of the impact of the COVID-19 shock during the lockdown.

Quercetin Modulates IGF-I and IGF-II Levels After Eccentric Exercise-Induced Muscle-Damage: A Placebo-Controlled Study.

Background: Prolonged or unaccustomed eccentric exercise may cause muscle damage and depending from its extent, this event negatively affects physical performance.

Objectives: The aim of the present investigation was to evaluate, in humans, the effect of the flavonoid quercetin on circulating levels of the anabolic insulin-like growth factor 1 (IGF-I) and insulin-like growth factor 2 (IGF-II), produced during the recovery period after an eccentric-induced muscle damage (EIMD).

Methods: A randomized, double-blind, crossover study has been performed; twelve young men ingested quercetin (1 g/day) or placebo for 14 days and then underwent an eccentric-induced muscle damaging protocol.

Lack of increased rate of force development after strength training is explained by specific neural, not muscular, motor unit adaptations.

Although maximal force increases following short-term isometric strength training, the rate of force development (RFD) may remain relatively unaffected. The underlying neural and muscular mechanisms during rapid contractions after strength training are largely unknown. Since strength training increases the neural drive to muscles, it may be hypothesized that there are distinct neural or muscular adaptations determining the change in RFD independently of an increase in maximal force.

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.

Deficit in knee extension strength following anterior cruciate ligament reconstruction is explained by a reduced neural drive to the vasti muscles.

The persistence of quadriceps weakness represents a major concern following anterior cruciate ligament reconstruction (ACLR). The underlying adaptations occurring in the activity of spinal motoneurons are still unexplored. This study examined the discharge patterns of large populations of motor units (MUs) in the vastus lateralis (VL) and vastus medialis muscles following ACLR.

Surface Electromyography: What Limits Its Use in Exercise and Sport Physiology?

The aim of the present paper is to examine to what extent the application of surface electromyography (sEMG) in the field of exercise and, more in general, of human movement, is adopted by professionals on a regular basis. For this purpose, a brief history of the recent developments of modern sEMG techniques will be assessed and evaluated for a potential use in exercise physiology and clinical biomechanics. The idea is to understand what are the limitations that impede the translation of sEMG to applied fields such as exercise physiology.

The effect of pedalling cadence on respiratory frequency: passive vs. active exercise of different intensities.

Purpose: Pedalling cadence influences respiratory frequency (f) during exercise, with group III/IV muscle afferents possibly mediating its effect. However, it is unclear how exercise intensity affects the link between cadence and f. We aimed to test the hypothesis that the effect of cadence on f is moderated by exercise intensity, with interest in the underlying mechanisms.

Reproducibility of muscle fibre conduction velocity during linearly increasing force contractions.

Muscle fibre conduction velocity (MFCV) is a basic physiological parameter biophysically related to the diameter of muscle fibres and properties of the sarcolemma. The aim of this study was to assess the intersession reproducibility of the relation between voluntary force and estimates of average muscle fibre conduction velocity (MFCV) from multichannel high-density surface electromyographic recordings (HDsEMG). Ten healthy men performed six linearly increasing isometric ankle dorsiflexions on two separate experimental sessions, 4 weeks apart.

Muscle fiber conduction velocity in the vastus lateralis and medialis muscles of soccer players after ACL reconstruction.

The neural factors underlying the persistency of quadriceps weakness after anterior cruciate ligament reconstruction (ACLR) have been only partially explained. This study examined muscle fiber conduction velocity (MFCV) as an indirect parameter of motor unit recruitment strategies in the vastus lateralis (VL) and medialis (VM) muscles of soccer players with ACLR. High-density surface electromyography (HDsEMG) was acquired from VL and VM in nine soccer players (22.

Strength Training Increases Conduction Velocity of High-Threshold Motor Units.

Purpose: Motor unit conduction velocity (MUCV) represents the propagation velocity of action potentials along the muscle fibers innervated by individual motor neurons and indirectly reflects the electrophysiological properties of the sarcolemma. In this study, we investigated the effect of a 4-wk strength training intervention on the peripheral properties (MUCV and motor unit action potential amplitude, RMSMU) of populations of longitudinally tracked motor units (MU).

Methods: The adjustments exhibited by 12 individuals who participated in the training (INT) were compared with 12 controls (CON).

The relative strength of common synaptic input to motor neurons is not a determinant of the maximal rate of force development in humans.

Correlation between motor unit discharge times, often referred to as motor unit synchronization, is determined by common synaptic input to motor neurons. Although it has been largely speculated that synchronization should influence the rate of force development, the association between the degree of motor unit synchronization and rapid force generation has not been determined. In this study, we examined this association with both simulations and experimental motor unit recordings.

Respiratory Frequency as a Marker of Physical Effort During High-Intensity Interval Training in Soccer Players.

Purpose: Variables currently used in soccer training monitoring fail to represent the physiological demand of the player during movements like accelerations, decelerations, and directional changes performed at high intensity. We tested the hypothesis that respiratory frequency (fR) is a marker of physical effort during soccer-related high-intensity exercise.

Methods: A total of 12 male soccer players performed a preliminary intermittent incremental test and 2 shuttle-run high-intensity interval training (HIIT) protocols, in separate visits.

You are as fast as your motor neurons: speed of recruitment and maximal discharge of motor neurons determine the maximal rate of force development in humans.

Key Points: We propose and validate a method for accurately identifying the activity of populations of motor neurons during contractions at maximal rate of force development in humans. The behaviour of the motor neuron pool during rapid voluntary contractions in humans is presented. We show with this approach that the motor neuron recruitment speed and maximal motor unit discharge rate largely explains the individual ability in generating rapid force contractions.

The increase in muscle force after 4 weeks of strength training is mediated by adaptations in motor unit recruitment and rate coding.

Key Points: Previous studies have indicated that several weeks of strength training is sufficient to elicit significant adaptations in the neural drive sent to the muscles. There are few data, however, on the changes elicited by strength training in the recruitment and rate coding of motor units during voluntary contractions. We show for the first time that the discharge characteristics of motor units in the tibialis anterior muscle tracked across the intervention are changed by 4 weeks of strength training with isometric voluntary contractions.

Respiratory frequency and tidal volume during exercise: differential control and unbalanced interdependence.

Differentiating between respiratory frequency (f ) and tidal volume (V ) may improve our understanding of exercise hyperpnoea because f and V seem to be regulated by different inputs. We designed a series of exercise manipulations to improve our understanding of how f and V are regulated during exercise. Twelve cyclists performed an incremental test and three randomized experimental sessions in separate visits.

Variability of estimates of muscle fiber conduction velocity and surface EMG amplitude across subjects and processing intervals.

The force developed by the human neuromuscular system can change very rapidly (15-50 ms). When processing EMG signals for inferring neural control strategies, it is therefore necessary to extract estimates from short time intervals. In this study, we investigate the relation between joint torque and estimates of average muscle fibre conduction velocity (MFCV) and amplitude (RMS) from surface EMG signals, when varying the duration of the processing interval.

Higher torque and muscle fibre conduction velocity of the Biceps Brachii in karate practitioners during isokinetic contractions.

Purpose: Although upper limb techniques are largely utilized during karate combat competitions scarce information regarding their NM control is available. This study aims at investigating the effect of karate practice on the NM control of Biceps and Triceps Brachii during isokinetic contractions to enhance current knowledge on neuromuscular control adaptations and training methodologies in combat sports.

Methods: Torque and surface electromyograms (sEMG) of Biceps Brachii Caput Longum (BB) and Triceps Brachii Lateral Head (TB) were recorded in eight karate practitioners (KA) and eight age-matched sedentary individuals (CO) during isokinetic elbow flexion-extensions (0-240°/s).