Theta Burst Stimulation Modulates Exercise Performance by Influencing Central Fatigue and Corticospinal Excitability.

Purpose: Theta-burst stimulation (TBS) over the primary motor cortex modulates activity of the underlying neural tissue, but little is known about its consequence on neuromuscular fatigue (NMF) and its neural correlates. This study aimed to compare the effects of facilitatory versus inhibitory TBS on the NMF and excitability/inhibition of the corticospinal pathway in an unfatigued/fatigued muscle.

Methods: The effects of three TBS protocols (facilitatory/intermittent: iTBS; inhibitory/continuous: cTBS, and sham: sTBS) were tested on exercise performance, neuromuscular function, corticospinal excitability and inhibition in twenty young healthy participants.

Effects of Foot-Strike Pattern on Neuromuscular Function During a Prolonged Graded Run.

Purpose: To study whether, during typical-level running, non-rear-foot strikers (non-RFS) or rear-foot strikers (RFS) presented a similar or different extent of neuromuscular fatigue after a prolonged graded run.

Methods: Sixteen experienced male trail runners (8 non-RFS and 8 RFS) performed a 2.5-hour treadmill graded running exercise.

Skeletal muscle fiber type and TMS-induced muscle relaxation in unfatigued and fatigued knee-extensor muscles.

The force drop after transcranial magnetic stimulation (TMS) delivered to the motor cortex during voluntary muscle contractions could inform about muscle relaxation properties. Because of the physiological relation between skeletal muscle fiber-type distribution and size and muscle relaxation, TMS could be a noninvasive index of muscle relaxation in humans. By combining a noninvasive technique to record muscle relaxation in vivo (TMS) with the gold standard technique for muscle tissue sampling (muscle biopsy), we investigated the relation between TMS-induced muscle relaxation in unfatigued and fatigued states, and muscle fiber-type distribution and size.

Sex differences in neuromuscular and biological determinants of isometric maximal force.

Aim: Force expression is characterized by an interplay of biological and molecular determinants that are expected to differentiate males and females in terms of maximal performance. These include muscle characteristics (muscle size, fiber type, contractility), neuromuscular regulation (central and peripheral factors of force expression), and individual genetic factors (miRNAs and gene/protein expression). This research aims to comprehensively assess these physiological variables and their role as determinants of maximal force difference between sexes.

Downhill running increases markers of muscle damage and impairs the maximal voluntary force production as well as the late phase of the rate of voluntary force development.

Purpose: To examined the time-course of the early and late phase of the rate of voluntary force development (RVFD) and muscle damage markers after downhill running.

Methods: Ten recreational runners performed a 30-min downhill run at 10 km h and -20% (-11.3°) on a motorized treadmill.

Comparison between conventional and neuronavigated strategies to assess corticospinal responsiveness in unfatigued and fatigued knee-extensor muscles.

In studying neuromuscular fatigability, researchers commonly use functional criteria to position and hold the transcranial magnetic stimulation (TMS) coil during testing sessions. This could influence the magnitude of corticospinal excitability and inhibition responses due to imprecise and unsteady positions of the coil. To reduce coil position and orientation variability, neuronavigated TMS (nTMS) could be used.

Hypoxia Does Not Change Performance and Psychophysiological Responses During Repeated Cycling Sprints to Exhaustion With Short Exercise-to-Rest Ratio.

Purpose: To compare the acute performance and psychophysiological responses of repeated cycling sprints to exhaustion with a short exercise-to-rest ratio (1:6), between different effort durations and inspired oxygen fractions.

Methods: On separate visits, 10 active participants completed 6 repeated cycling sprint exercises to exhaustion with 3 different effort durations (5, 10, and 20 s) and 2 conditions of inspired oxygen (20.9% and 13.

The Oxidative-Glycolytic Balance Influenced by Sprint Duration Is Key during Repeated Sprint in Hypoxia.

Purpose: This study investigates the effects of normobaric hypoxia on repeated sprint exercise (RSE) with different balance between oxidative (phosphocreatine and oxidative pathway) and glycolytic contributions. Therefore, performance and psychophysiological responses were compared during RSE to exhaustion with the same exercise-to-rest ratio (1:2) but different sprint durations (5, 10, or 20 s) either in normoxic (RSN) or hypoxic (RSH; F io2 = 0.13) conditions.

Downhill running affects the late but not the early phase of the rate of force development.

Purpose: This study aimed to evaluate the acute changes in the knee extensors maximum voluntary isometric contraction force (MVIC), rate of force development (RFD), and rate of EMG rise (RER) following a bout of downhill running.

Methods: MVIC and RFD at 0-50, 50-100, 100-200, and 0-200 ms were determined in thirteen men (22 ± 2 yr) before and after 30 min of downhill running (speed: 10 km h; slope: - 20%). Vastus lateralis maximum EMG (EMG) and RER at 0-30, 0-50, and 0-75 ms were also recorded.

Performance fatigability and recovery after dynamic multi-joint maximal exercise in elbow flexors versus knee extensors.

Elbow flexors (EFs) and knee extensors (KEs) have shown differences in performance fatigability and recovery of neuromuscular function after isometric and isotonic single-joint fatiguing contractions. However, dynamic multi-joint movements are more representative of real-world activities. The aim of the study was to assess central and peripheral mechanisms of fatigability after either arm-cranking or cycling.

Internal Tibial Forces and Moments During Graded Running.

The stress experienced by the tibia has contributions from the forces and moments acting on the tibia. We sought to quantify the influence of running grade on internal tibial forces and moments. Seventeen participants ran at 3.

Neuromuscular, biomechanical, and energetic adjustments following repeated bouts of downhill running.

Purpose: This study used downhill running as a model to investigate the repeated bout effect (RBE) on neuromuscular performance, running biomechanics, and metabolic cost of running.

Methods: Ten healthy recreational male runners performed two 30-min bouts of downhill running (DR1 and DR2) at a -20% slope and 2.8 m/s 3 weeks apart.

Use of transcranial magnetic stimulation to assess relaxation rates in unfatigued and fatigued knee-extensor muscles.

We examined whether transcranial magnetic stimulation (TMS) delivered to the motor cortex allows assessment of muscle relaxation rates in unfatigued and fatigued knee extensors (KE). We assessed the ability of this technique to measure time course of fatigue-induced changes in muscle relaxation rate and compared relaxation rate from resting twitches evoked by femoral nerve stimulation. Twelve healthy men performed maximal voluntary isometric contractions (MVC) twice before (PRE) and once at the end of a 2-min KE MVC and five more times within 8 min during recovery.

Effect of a Fatiguing Ultratrail on the Graded Energetically Optimal Stride Frequency.

Purpose: To study the consequences of a fatiguing ultratrail run of 6 hours on self-optimizing capability during uphill and downhill (DR) running.

Methods: The authors collected temporal stride kinematics and metabolic data in 8 (experimental group) male runners before and after the ultratrail run and in 6 (control group) male ultramarathon runners who did not run but stayed awake and performed normal, daily physical activities avoiding strenuous exercises over the 6-hour period. For each subject, preferred and optimal stride frequencies were measured, where stride frequency was systematically varied above and below the preferred one (±4% and ±8%) while running 3 conditions on level, 5% uphill, or 5% DR in a randomized order.

Spinal contribution to neuromuscular recovery differs between elbow-flexor and knee-extensor muscles after a maximal sustained fatiguing task.

Data from studies of elbow-flexor (EF) or knee-extensor (KE) muscles suggest that a fatigue-related decrease in motoneuron excitability only occurs in EF. It is unknown how motoneuron excitability changes after sustained fatiguing maximal voluntary isometric contractions (MVICs) in EF and KE in the same participants. In two sessions, eight healthy men performed a 2-min MVIC of EF or KE to induce fatigue with brief MVICs before and six times after the 2-min MVIC.

Biomechanics of graded running: Part II-Joint kinematics and kinetics.

Compared to level running (LR), different strategies might be implemented by runners to cope with specific challenges of graded running at different speeds. The changes in joint kinetics and kinematics associated with graded running have been investigated, but their interactions with speed are unknown. Nineteen participants ran on an instrumented treadmill at five grades (0°, ±5° and ± 10°) and three speeds (2.

Biomechanics of graded running: Part I - Stride parameters, external forces, muscle activations.

Biomechanical alterations with graded running have only been partially quantified, and the potential interactions with running speed remain unclear. We measured spatiotemporal parameters, ground reaction forces, and leg muscle activations (EMG) in nineteen adults (10F/9M) running on an instrumented treadmills at 2.50, 3.

Defining Off-road Running: A Position Statement from the Ultra Sports Science Foundation.

Off-road running continues to grow in popularity, with differing event categories existing, and terminologies are often used interchangeably and without precision. Trail running, mountain running, skyrunning, fell running, orienteering, obstacle course racing and cross-country running all take place predominantly in off-road terrain. Ultramarathon running refers to any running event over marathon distance conducted in any terrain and surface.

Changes in spatio-temporal gait parameters and vertical speed during an extreme mountain ultra-marathon.

The aim of the present study was to investigate the effects of altitude and distance on uphill vertical speed (VS) and the main spatio-temporal gait parameters during an extreme mountain ultra-marathon. The VS, stride height (SH) and stride frequency (SF) of 27 runners were measured with an inertial sensor at the shank for two different altitude ranges (low 1300-2000 m vs high 2400-3200 m) of 10 mountains passes distributed over a 220 km course. There was a significant interaction ((4,52) = 4.

Sustained Maximal Voluntary Contractions Elicit Different Neurophysiological Responses in Upper- and Lower-Limb Muscles in Men.

This study compared the effects of fatigue on corticospinal responsiveness in the upper- and lower-limb muscles of the same participants. Seven healthy males performed a 2-min maximal voluntary isometric contraction of the elbow flexors or knee extensors on four separate days. Electromyographic responses were elicited by nerve stimulation (maximal M-wave) in all sessions and by transcranial magnetic stimulation (motor-evoked potential; silent period) and spinal tract stimulation (cervicomedullary or thoracic motor-evoked potentials; silent period) in one session each per limb.

Step length and grade effects on energy absorption and impact attenuation in running.

We sought to examine the effect of step length manipulation on energy absorption and impact attenuation during graded running. Nineteen runners (10F, 9M) ran on an instrumented treadmill at three step lengths (preferred and ±10% preferred) at each of five grades (0°, ±5°, and ±10°) while 3D motion data were captured. Speed was held constant at 3.