Sprint Acceleration Mechanical Outputs Derived from Position- or Velocity-Time Data: A Multi-System Comparison Study.

To directly compare five commonly used on-field systems (motorized linear encoder, laser, radar, global positioning system, and timing gates) during sprint acceleration to (i) measure velocity−time data, (ii) compute the main associated force−velocity variables, and (iii) assess their respective inter-trial reliability. Eighteen participants performed three 40 m sprints, during which five systems were used to simultaneously and separately record the body center of the mass horizontal position or velocity over time. Horizontal force−velocity mechanical outputs for the two best trials were computed following an inverse dynamic model and based on an exponential fitting of the position- or velocity-time data.

International matches elicit stable mechanical workload in high-level female ice hockey.

This study aimed to quantify in- and between-match characteristics and mechanical workload variations elicited by a congested schedule in high-level female ice hockey. Six players were monitored during four international pre-season exhibition matches against the same opponent. Two different methods (Player Load and Accel'Rate) were used to assess specific mechanical workload.

A Novel Accelerometry-Based Metric to Improve Estimation of Whole-Body Mechanical Load.

While the Player Load is a widely-used parameter for physical demand quantification using wearable accelerometers, its calculation is subjected to potential errors related to rotational changes of the reference frame. The aims of this study were (i) to assess the concurrent validity of accelerometry-based Player Load against force plates; (ii) to validate a novel metric, the Accel'Rate overcoming this theoretical issue. Twenty-one recreational athlete males instrumented with two triaxial accelerometers positioned at the upper and lower back performed running-based locomotor movements at low and high intensity over six in-series force plates.

Validity of an ultra-wideband local positioning system to assess specific movements in handball.

The aim of this study was to examine the concurrent validity of the Kinexon local positioning system (LPS) in comparison with the Vicon motion capture system used as the reference. Five recreationally active men performed ten repetitions of linear sprints, medio-lateral side-to-side and handball-specific movements both in the centre and on the side of an indoor field. Validity was assessed for peak speed, peak acceleration and peak deceleration using standardised biases, Pearson coefficient of correlation (r), and standardised typical error of the estimate.

The slack test does not assess maximal shortening velocity of muscle fascicles in humans.

The application of a series of extremely high accelerative motor-driven quick releases while muscles contract isometrically (i.e. slack test) has been proposed to assess unloaded velocity in human muscle.

Time-Course of Neuromuscular Changes during and after Maximal Eccentric Contractions.

This study tested the relationship between the magnitude of muscle damage and both central and peripheral modulations during and after eccentric contractions of plantar flexors. Eleven participants performed 10 sets of 30 maximal eccentric contractions of the plantar flexors at 45°·s(-1). Maximal voluntary torque, evoked torque (peripheral component) and voluntary activation (central component) were assessed before, during, immediately after (POST) and 48 h after (48 h) the eccentric exercise.

Acceleration capability in elite sprinters and ground impulse: Push more, brake less?

Overground sprint studies have shown the importance of net horizontal ground reaction force impulse (IMPH) for acceleration performance, but only investigated one or two steps over the acceleration phase, and not in elite sprinters. The main aim of this study was to distinguish between propulsive (IMPH+) and braking (IMPH-) components of the IMPH and seek whether, for an expected higher IMPH, faster elite sprinters produce greater IMPH+, smaller IMPH-, or both. Nine high-level sprinters (100-m best times range: 9.

Is muscle coordination affected by loading condition in ballistic movements?

This study aimed to investigate the effect of loading on lower limb muscle coordination involved during ballistic squat jumps. Twenty athletes performed ballistic squat jumps on a force platform. Vertical force, velocity, power and electromyographic (EMG) activity of lower limb muscles were recorded during the push-off phase and compared between seven loading conditions (0-60% of the concentric-only maximal repetition).

Validity of trunk extensor and flexor torque measurements using isokinetic dynamometry.

This study aimed to evaluate the validity and test-retest reliability of trunk muscle strength testing performed with a latest-generation isokinetic dynamometer. Eccentric, isometric, and concentric peak torque of the trunk flexor and extensor muscles was measured in 15 healthy subjects. Muscle cross sectional area (CSA) and surface electromyographic (EMG) activity were respectively correlated to peak torque and submaximal isometric torque for erector spinae and rectus abdominis muscles.

Mechanical and muscular coordination patterns during a high-level fencing assault.

Purpose: This study aimed to investigate the coordination of lower limb muscles during a specific fencing gesture in relation to its mechanical effectiveness.

Methods: Maximal isokinetic concentric and isometric plantarflexor, dorsiflexor, knee and hip extensor and flexor torques of 10 female elite saber fencers were assessed and compared between both legs. Sabers completed three trials of a specific fencing gesture (i.

Changes in spring-mass behavior and muscle activity during an exhaustive run at V̇O2max.

Purpose: The aim of this study was to evaluate concomitantly the changes in leg-spring behavior and the associated modifications in the lower limb muscular activity during a constant pace run to exhaustion at severe intensity.

Methods: Twelve trained runners performed a running test at the velocity associated with VO(2max) (5.1 ± 0.

Effects of air-pulsed cryotherapy on neuromuscular recovery subsequent to exercise-induced muscle damage.

Background: Localized cooling has been proposed as an effective strategy to limit the deleterious effects of exercise-induced muscle damage on neuromuscular function. However, the literature reports conflicting results.

Purpose: This randomized controlled trial aimed to determine the effects of a new treatment, localized air-pulsed cryotherapy (-30°C), on the recovery time-course of neuromuscular function following a strenuous eccentric exercise.

A multidisciplinary approach to overreaching detection in endurance trained athletes.

In sport, high training load required to reach peak performance pushes human adaptation to their limits. In that process, athletes may experience general fatigue, impaired performance, and may be identified as overreached (OR). When this state lasts for several months, an overtraining syndrome is diagnosed (OT).

Adjustment of muscle coordination during an all-out sprint cycling task.

Purpose: This study was designed to assess muscle coordination during a specific all-out sprint cycling task (Sprint). The aim was to estimate the EMG activity level of each muscle group by referring to the submaximal cycling condition (Sub150 W) and to test the hypothesis that a maximal activity is reached for all of the muscles during Sprint.

Methods: Fifteen well-trained cyclists were tested during submaximal and sprint cycling exercises and a series of maximal voluntary contractions (MVCs) in isometric and isokinetic modes (MVC at the three lower limb joints).

Consistency of muscle synergies during pedaling across different mechanical constraints.

The purpose of the present study was to determine whether muscle synergies are constrained by changes in the mechanics of pedaling. The decomposition algorithm used to identify muscle synergies was based on two components: "muscle synergy vectors," which represent the relative weighting of each muscle within each synergy, and "synergy activation coefficients," which represent the relative contribution of muscle synergy to the overall muscle activity pattern. We hypothesized that muscle synergy vectors would remain fixed but that synergy activation coefficients could vary, resulting in observed variations in individual electromyographic (EMG) patterns.

Simplified recording technique for the identification of inspiratory premotor potentials in humans.

Inspiratory premotor potentials reflect the involvement of premotor cortical networks in the compensation of mechanical respiratory loading. Electromagnetic pollution and movement artefacts make them difficult to record, particularly in clinical environment. In 7 healthy subjects, we tested a simplified recording setup (single vs.

Force-velocity relationship in cycling revisited: benefit of two-dimensional pedal forces analysis.

Purpose: Maximal cycling exercise has been widely used to describe the power-velocity characteristics of lower-limb extensor muscles. This study investigated the contribution of each functional sector (i.e.

Changes of pedaling technique and muscle coordination during an exhaustive exercise.

Purpose: Alterations of the mechanical patterns during an exhaustive pedaling exercise have been previously shown. We designed the present study to test the hypothesis that these alterations in the biomechanics of pedaling, which occur during exhaustive exercise, are linked to changes in the activity patterns of lower limb muscles.

Methods: Ten well-trained cyclists were tested during a limited time to exhaustion, performing 80% of maximal power tolerated.

Neuromuscular fatigue following high versus low-intensity eccentric exercise of biceps brachii muscle.

Purpose: This study investigated neuromuscular fatigue following high versus low-intensity eccentric exercise corresponding to the same amount of work.

Methods: Ten volunteers performed two eccentric exercises of the elbow flexors: a high-intensity versus a low-intensity exercise. Maximal voluntary contraction torque and surface electromyography of the biceps brachii muscle were recorded before, immediately and 48 h after exercises.

Interindividual variability of electromyographic patterns and pedal force profiles in trained cyclists.

The aim of this study was to determine whether high inter-individual variability of the electromyographic (EMG) patterns during pedaling is accompanied by variability in the pedal force application patterns. Eleven male experienced cyclists were tested at two submaximal power outputs (150 and 250 W). Pedal force components (effective and total forces) and index of mechanical effectiveness were measured continuously using instrumented pedals and were synchronized with surface electromyography signals measured in ten lower limb muscles.

Elite long sprint running: a comparison between incline and level training sessions.

Purpose: We compared incline and level training sessions as usually used in elite 400-m runners through stride kinematics and muscular activity measurements.

Methods: Nine highly trained 400-m runners (international and French national level) performed two maximal velocity sprints: 1) 300-m on level ground (LEV) and 2) 250-m on an incline ground (INC) characterized by a mean +/- SD grade of 5.4 +/- 0.

Influence of training background on the relationships between plantarflexor intrinsic stiffness and overall musculoskeletal stiffness during hopping.

The aim of this study was to characterize the influence of intrinsic musculotendinous and musculoarticular stiffness of plantarflexor muscles on (1) the overall musculoskeletal stiffness and (2) the performance during stretch-shortening cycles-type exercise. The influence of plyometric training background on these relationships was also analyzed. Musculotendinous (SIMT), passive (KP) and active (SIMA) musculoarticular stiffnesses were quantified, using quick-release and sinusoidal perturbation tests, on nine French elite long or triple jumpers (athlete group, AG) and nine control subjects (CG).

Intra-session repeatability of lower limb muscles activation pattern during pedaling.

Assessment of intra-session repeatability of muscle activation pattern is of considerable relevance for research settings, especially when used to determine changes over time. However, the repeatability of lower limb muscles activation pattern during pedaling is not fully established. Thus, we tested the intra-session repeatability of the activation pattern of 10 lower limb muscles during a sub-maximal cycling exercise.

Electroencephalographic evidence for pre-motor cortex activation during inspiratory loading in humans.

Faced with mechanical inspiratory loading, awake animals and anaesthetized humans develop alveolar hypoventilation, whereas awake humans do defend ventilation. This points to a suprapontine compensatory mechanism instead of or in addition to the 'traditional' brainstem respiratory regulation. This study assesses the role of the cortical pre-motor representation of inspiratory muscles in this behaviour.