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International audience; Objectives: The aim of the present study was to investigate the level of cardiorespiratory fitness and neuromuscular function of ICU survivors after COVID-19 and to examine whether these outcomes are related to ICU stay/mechanical ventilation duration.Design: Prospective nonrandomized study.Setting: Patients hospitalized in ICU for COVID-19 infection.Patients: Sixty patients hospitalized in ICU (mean duration: 31.9 ± 18.2 d) were recruited 4-8 weeks post discharge from ICU.Interventions: None.Measurements and main results: Patients visited the laboratory on two separate occasions. The first visit was dedicated to quality of life questionnaire, cardiopulmonary exercise testing, whereas measurements of the knee extensors neuromuscular function were performed in the second visit. Maximal oxygen uptake (V o2 max) was 18.3 ± 4.5 mL·min -1 ·kg -1 , representing 49% ± 12% of predicted value, and was significantly correlated with ICU stay/mechanical ventilation (MV) duration ( R = -0.337 to -0.446; p < 0.01 to 0.001), as were maximal voluntary contraction and electrically evoked peak twitch. V o2 max (either predicted or in mL· min -1 ·kg -1 ) was also significantly correlated with key indices of pulmonary function such as predicted forced vital capacity or predicted forced expiratory volume in 1 second ( R = 0.430-0.465; p ≤ 0.001) and neuromuscular function. Both cardiorespiratory fitness and neuromuscular function were correlated with self-reported physical functioning and general health status.Conclusions: V o2 max was on average only slightly above the 18 mL·min -1 ·kg -1 , that is, the cut-off value known to induce difficulty in performing daily tasks. Overall, although low physical capacities at admission in ICU COVID-19 patients cannot be ruled out to explain the association between V o2 max or neuromuscular function and ICU stay/MV duration, altered cardiorespiratory fitness and neuromuscular function observed in the present study may not be specific to COVID-19 disease but seem applicable to all ICU/MV patients of similar duration.

Purpose: Fatigue has previously been investigated in trail running by comparing maximal isometric force before and after the race. Isometric contractions may not entirely reflect fatigue-induced changes, and therefore dynamic evaluation is warranted. The aim of the present study was to compare the magnitude of the decrement of maximal isometric force versus maximal power, force, and velocity after trail running races ranging from 40 to 170 km. Methods: Nineteen trail runners completed races shorter than 60 km, and 21 runners completed races longer than 100 km. Isometric maximal voluntary contractions (IMVCs) of knee extensors and plantar flexors and maximal 7-second sprints on a cycle ergometer were performed before and after the event. Results: Maximal power output (Pmax; −14% [11%], P F0; −11% [14%], P P = .037) decreased significantly after both races. All dynamic parameters but theoretical maximum velocity decreased more after races longer than 100 km than races shorter than 60 km (P P F0 and Pmax, reductions in IMVCs for knee extensors (−29% [16%], P P P Pmax and F0. Conclusions: After a trail running race, reductions in isometric versus dynamic forces were correlated, yet they are not interchangeable because the losses in isometric force were 2 to 3 times greater than the reductions in Pmax and F0. This study also shows that the effect of race distance on fatigue measured in isometric mode is true when measured in dynamic mode.

Sabater Pastor, FS, Besson, T, Berthet, M, Varesco, G, Kennouche, D, Dandrieux, P-E, Rossi, J, and Millet, GY. Elite road vs. trail runners: comparing economy, biomechanics, strength, and power. J Strength Cond Res 37(1): 181-186, 2023-The purpose of this study was to determine the differences between road (ROAD) vs. trail (TRAIL) elite runners in terms of force-velocity profile (FVP), running biomechanics, lower-limb maximal isometric strength, cost of running (Cr), and training. Seventeen male elite athletes (10 TRAIL and 7 ROAD) participated in this study. Force-velocity profile was measured using a 2-sprint test on a cycle ergometer. Strength was assessed with a dynamometer measuring isometric maximum voluntary torque of the knee extensors and knee flexors. Biomechanics parameters (running kinematics and stiffness) were measured, and Cr was calculated at 10 and 14 km·h-1 at 0% slope and at 10 km·h-1 on a 10% slope on a treadmill. Athletes also reported their training duration during the previous year. Theoretical maximal torque (F0) and maximal power (Pmax) in the FVP were higher for TRAIL vs. ROAD (122 ± 13 vs. 99 ± 7 N·m, p = 0.001; and 726 ± 89 vs. 626 ± 44 W; p = 0.016). Cost of running was higher for TRAIL compared with ROAD on flat at 14 km·h-1 (4.32 ± 0.22 vs. 4.06 ± 0.29 J·kg-1·m-1; p = 0.047) but similar at 10 km·h-1 and uphill. No differences were found in maximal isometric strength or running biomechanics. ROAD spent 81% more time training than TRAIL (p = 0.0003). The specific training (i.e., "natural" resistance training) performed during graded running in trail runners and training on level surface at high speed may explain our results. Alternatively, it is possible that trail running selects stronger athletes because of the greater strength requirements of graded running.

The present study aimed to directly compare the effects of 30 min muscle (VIBBefore (PRE) and immediately after (POST) LV applied to the quadriceps muscle or its tendon, we investigated MVIC and RTD (STUDY #1; n = 20) or vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) electromyography responses to thoracic electrical stimulation (TMEPs; motoneuron excitability) and transcranial magnetic stimulation (MEPs; corticospinal excitability) (STUDY #2; n = 17). MEP/TMEP ratios were further calculated to quantify changes in cortical excitability.MVIC decreased at POST (P = 0.017) without any difference between VIBThe present results suggest that prolonged muscle and tendon LV are similarly effective in modulating central nervous system excitability and decreasing maximal force. Yet, altered explosive performance after tendon but not muscle LV suggests greater neural alterations when tendons are vibrated.

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Fatigue-related mechanisms induced by low-intensity prolonged contraction in lower limb muscles are currently unknown. This study investigated central fatigue kinetics in the knee extensors during a low-intensity sustained isometric contraction. Eleven subjects sustained a 10% maximal voluntary contraction (MVC) until task failure (TF) with neuromuscular evaluation every 3 minutes. Testing encompassed transcranial magnetic stimulation to evaluate maximal voluntary activation (VATMS ), motor evoked potential (MEP), and silent period (SP), and peripheral nerve stimulation to assess M-wave. Rating of perceived exertion (RPE) was also recorded. MVC progressively decreased up to 50% of the time to TF (ie, 50%TTF ) and then plateaued, reaching ~50% at TF (P < .001). VATMS progressively decreased up to 90%TTF and then plateaued, the decrease reaching ~20% at TF (P < .001). SP was lengthened early (ie, from 20%TTF ) during the exercise and then plateaued (P < .01). No changes were reported for MEP evoked during MVC (P = .87), while MEP evoked during submaximal contractions decreased early (ie, from 20%TTF ) during the exercise and then plateaued (P < .01). RPE increased linearly during the exercise to be almost maximal at TF. M-waves were not altered (P = .88). These findings confirm that TF is due to the subjects reaching their maximal perceived effort rather than any particular central event or neuromuscular limitations since MVC at TF was far from 10% of its original value. It is suggested that strategies minimizing RPE (eg, motivational self-talk) should be employed to enhance endurance performance.