Hugo A. Kerherve

Purpose Low-load blood-flow resistance training (LLBFRT) is increasingly used as an alternative to high-load resistance training (HLRT) to improve muscle strength and endurance while reducing mechanical stress on tissues. However, the acute responses associated with LLBFRT during sport climbing-specific exercises remain unknown. The aims of the study were to describe muscle oxygenation, fatigue and perceptual responses to climbing-specific finger flexors exercise in LLBFRT and compare such responses to HLRT. Methods Fifteen advanced to elite climbers took part in three visits: a familiarization session and two randomized finger-flexors training sessions in either HLRT (3 sets of 10–12 repetitions, ~70% maximal voluntary contraction, MVC) or LLBFRT (3 sets of 14–20 repetitions, ~40%MVC with cuff set at 60% of limb occlusion pressure). Finger flexors muscle oxygenation was assessed using near-infrared spectroscopy. Force–time integral (FTI) quantified mechanical load under both modalities. Muscle fatigue was quantified as force loss from pre- to 1-min, 5-min and 15-min post-exercise. Perceived discomfort, effort, and finger pain were assessed after each set. Results LLBFRT led to greater muscle deoxyhemoglobin values (+20 ± 25%, p = 0.005, d = 0.9) during exercise. Despite lower FTI (−7 ± 10%, p = 0.028), muscle fatigue was greater in LLBFRT than HLRT 1-min post-exercise (−24.8 ± 7.9 vs −18.6 ± 7.4%MVC, p = 0.016) but not 5-min and 15-min post-exercise. LLBFRT caused greater discomfort during inter-set recovery but lower finger pain during exercise. Conclusion Climbing-specific LLBFRT induced a transient increase in finger flexors muscle deoxygenation and fatigue likely due to elevated metabolic stress and venous blood pooling, while reducing mechanical load and thus potentially lowering injury risk.

Purpose: Carbon plates have been used to increase running shoes’ longitudinal bending stiffness (LBS), leading to reductions in the energy cost of level running (Cr). However, whether or not this is true during uphill (UH) running remains unknown. The aim of our study was to identify the effect of LBS on Cr during UH running. Methods: Twenty well-trained male runners participated in this study. Cr was determined using gas exchange during nine 4-minute bouts performed using 3 different LBS shoe conditions at 2.22 and 4.44 m/s on level and 2.22 m/s UH (gradient: + 15%) running. All variables were compared using 2-way analyses of variance (LBS × speed/grade effects). Results: There was no significant effect of LBS (F = 2.04; P = .14, ) and no significant LBS × grade interaction (F = 0.31; P = .87, ). Results were characterized by a very large interindividual variability in response to LBS changes. Conclusions: The current study contributes to a growing body of literature reporting no effect of LBS on Cr during level and UH running. Yet, the very large interindividual differences in response to changes in LBS suggest that increasing shoe LBS may be beneficial for some runners.

Background: Moderate intensity exercise ranging 40–60% of maximum oxygen uptake is advised to promote energy expenditure and fat oxidation in overweight and obese people. Although fat oxidation has been shown to be highly variable among individual, there is still a relative uncertainty regarding exercise prescription for women specifically. This article aimed to determine whether indicators of body composition can be used to narrow the exercise intensity range for exercise prescription in women.Methods: A total of 35 healthy women (age 30.8±9.5 yr) classified according to their BMI in normal weight (NOR; ≤24.9 kg·m²), overweight (OVW; 25–29.9 kg·m²) and obese groups (OBE; ≥30 kg·m²) completed a submaximal graded test (intensities eliciting ~30%, 40%, 50% and 60% of maximum oxygen uptake). Blood lactate, perceived exertion and absolute and relative substrate oxidation for fat (OX_FAT) and carbohydrates (OX_CHO) were measured at each stage.Results: Perceived exertion and blood lactate increased as a function of exercise but did not differ across groups. There were no significant changes in absolute and relative OX_FATacross groups, or as a function of exercise intensity. Peak OX_FAToccurred at the 40%, 50% and 40% stages for NOR, OVW and OBE groups, respectively, with no significant differences across groups.Conclusion: We measured no differences, but considerable inter-individual variation, in fat oxidation in women of different body composition. This result is in agreement with previous research based on exercise performed at constant rate and in independent participant groups. Our findings do not support the fat oxidation hypothesis, and further emphasise the perspective that exercise prescription should be individualised and likely be based on considerations other than substrate oxidation.

Evaluating and minimising the risk of hamstring injury remains complex as it lacks reliable field-testing. Kinematic analysis provides global external insights but fails to apprehend musculoskeletal loading. This study aimed to evaluate the association between hamstring function and prior injury using a novel functional test combined with a musculoskeletal approach. Twelve professional footballers, distributed in two groups (control or previously injured), performed a reactive functional test to one of four targets from a standing start and performed a knee and plantar extension on target. Joint kinematics served as input data of a musculoskeletal model, and joint angles and hamstring muscle lengths were calculated. Results showed that biceps femoris long head (BFlh) was stretched to 150 ± 2% of initial length during the two conditions. Maximal BFlh length and time to stretch were significantly higher in the control group. Kinematics and musculoskeletal parameters revealed that participants of the control group had higher maximal hip flexion, pelvis anterior tilt, and hip internal rotation than previously-injured players. The combined approach of a hamstring functional test and musculoskeletal modelling gives new preliminary insights on the effect of previous history of hamstring injury on lower limb kinematics and BFlh muscle length.

This study aimed to compare the time course of measures of performance, fatigue, and perceived exertion during repeated-sprint ability (RSA) testing performed on a non-motorized treadmill (NMT) and cycling ergometer (CE). Fourteen physically active participants performed two 10 ×6 s⁻¹ RSA tests with a 1:4 work-to-rest ratio (24 s recovery) on NMT and CE. Measures of performance [peak and mean power output (PPO and MPO), cadence, and the time to reach PPO (TTP)] and of fatigue (fatigue index and decrement score) and ratings of perceived exertion (RPE) were collected during each session. The level of significance was set at p < 0.05. Participants completed the RSA test at a MPO of 1,041 ± 141 W on CE and 431 ± 48 W on NMT, achieving PPO of 2,310 ± 339 W on CE and 1,763 ± 289 W on NMT. Participants' weight was significantly correlated with PPO and MPO on CE (p < 0.001) and with MPO on NMT (p < 0.001). PPO on CE and NMT was significantly correlated only for absolute measures of power (p < 0.01). Cadence was higher and decreased throughout the RSA on NMT compared to CE, where it decreased only at the seventh bout. TTP was significantly shorter and more affected by fatigue on NMT than on CE. Fatigue indices were significantly greater on NMT compared to CE, with significant correlations between the decrement score and absolute and relative PPO on CE and NMT, between the fatigue index and absolute and relative PPO only on NMT, and no significant correlations with MPO. During RSA, RPE increased more on NMT compared to CE from bouts 3 to 7. During recovery, RPE was consistently higher on NMT at 1, 3, and 5 min post exercise compared to CE. These findings indicate that RSA performed on NMT induces greater fatigue and physiological load than CE, which originated in the lower resistive torque typically used on NMT compared to CE, resulting in a front loaded power output profile from the greater acceleration and cadence. From these results, we discuss that despite providing highly correlated measures of power output, NMT and CE should not be used interchangeably to assess RSA as they elicit markedly different responses. We also discuss these results from the fundamental differences in active muscle mass and power application patterns between running and cycling, which could form the basis of future studies.

Virtual reality using head-mounted displays (HMD) could provide enhanced physical load during active gaming (AG) compared to traditional displays. We aimed to compare the physical load elicited by conventional exercise and AG with an HMD. We measured energy expenditure (EE) and heart rate (HR) in nine healthy men (age: 27 ± 5 years) performing three testing components in a randomised order: walking at 6 km/h (W6), AG, and AG with an additional constraint (AG^W; wrist-worn weights). Although we found that HR was not significantly different between W6 and the two modes of AG, actual energy expenditure was consistently lower in AG and AG^W compared to W6. We observed that playing AG with wrist-worn weights could be used as a means of increasing energy expenditure only at maximum game level, but ineffective otherwise. Our findings indicate that AG in an HMD may not provide a sufficient stimulus to meet recommended physical activity levels despite increased psychophysiological load. The differential outcomes of measures of HR and EE indicates that HR should not be used as an indicator of EE in AG. Yet, adding a simple constraint (wrist-worn weights) proved to be a simple and effective measure to increase EE during AG.