Papers by Stephane Dufour
Biology, 2021
Endurance profile assessment is of major interest to evaluate the cyclist’s performance potential... more Endurance profile assessment is of major interest to evaluate the cyclist’s performance potential. In this regard, maximal oxygen uptake and functional threshold power are useful functional parameters to determine metabolic training zones (ventilatory threshold). The aim of this study was to evaluate and compare the physiological profile of different road cyclist age categories (Youth, Junior, and Under-23) to obtain the performance requirements. Sixty-one competitive road cyclists (15–22 years) performed a maximal incremental test on a bike in order to determine functional parameters (maximal fat oxidation zone, ventilatory thresholds, maximal oxygen uptake, and functional threshold power) and metabolic training zones. The results suggest major differences, with the Youth group showing clear changes in all metabolic zones except in fat oxidation. The main differences between Under-23 vs. Junior groups were observed in maximal relative power output (Under-23: 6.70 W·Kg−1; Junior: 6....
Introduction: Understanding the impact of lockdown upon RT, and how people adapted their RT behav... more Introduction: Understanding the impact of lockdown upon RT, and how people adapted their RT behaviours, is expected to have implications for strategies to maintain engagement in positive health behaviours such as this during- restrictive pandemic-related public health measures. Further, doing so will provide a baseline for investigation of the long-term effects of these measures upon behaviours and perceptions and facilitate future follow-up study. Objectives: To determine how the onset of coronavirus (COVID-19), and the associated ‘lockdown’, affected resistance training (RT) behaviours, in addition to motivation, perceived effectiveness, enjoyment, and intent to continue, in those who regularly performed resistance training RT prior to the pandemic. Methods: We conducted an observational, cross-sectional study using online surveys in multiple languages (English, Danish, French, German, Italian, Portuguese, Slovakian, Swedish, and Japanese) distributed across social media platforms...
Frontiers in Oncology, 2020
Background: Cancer cachexia and exacerbated fatigue represent two hallmarks in cancer patients, n... more Background: Cancer cachexia and exacerbated fatigue represent two hallmarks in cancer patients, negatively impacting their exercise tolerance and ultimately their quality of life. However, the characterization of patients' physical status and exercise tolerance and, most importantly, their evolution throughout cancer treatment may represent the first step in efficiently counteracting their development with prescribed and tailored exercise training. In this context, the aim of the PROTECT-01 study will be to investigate the evolution of physical status, from diagnosis to the end of first-line treatment, of patients with one of the three most common cancers (i.e., lung, breast, and colorectal). The PROTECT-01 cohort study will include 300 patients equally divided between lung, breast and colorectal cancer. Patients will perform a series of assessments at three visits throughout the treatment: (1) between the date of diagnosis and the start of treatment, (2) 8 weeks after the start of treatment, and (3) after the completion of first-line treatment or at the 6-months mark, whichever occurs first. For each of the three visits, subjective and objective fatigue, maximal voluntary force, body composition, cachexia, physical activity level, quality of life, respiratory function, overall physical performance, and exercise tolerance will be assessed. Discussion: The present study is aimed at identifying the nature and severity of maladaptation related to exercise intolerance in the three most common cancers. Therefore, our results should contribute to the delineation of the needs of each group of patients and to the determination of the most valuable exercise interventions in order to counteract these maladaptations. This descriptive and comprehensive approach is a prerequisite in order to elaborate, through future interventional research projects, tailored exercise strategies to counteract specific symptoms that are potentially cancer type-dependent and, in fine, to improve the health and quality of life of cancer patients. Moreover, our concomitant focus on fatigue and cachexia will provide Mallard et al. The PROTECT-01 Cohort Study Protocol insightful information about two factors that may have substantial interaction but require further investigation. Trial registration: This prospective study has been registered at ClinicalTrials.gov (NCT03956641), May, 2019.
Frontiers in Physiology, 2017
Whether and how moderate exercise might allow for accelerated limb recovery in chronic critical l... more Whether and how moderate exercise might allow for accelerated limb recovery in chronic critical limb ischemia (CLI) remains to be determined. Chronic CLI was surgically induced in mice, and the effect of moderate exercise (training five times per week over a 3-week period) was investigated. Tissue damages and functional scores were assessed on the 4th, 6th, 10th, 20th, and 30th day after surgery. Mice were sacrificed 48 h after the last exercise session in order to assess muscle structure, mitochondrial respiration, calcium retention capacity, oxidative stress and transcript levels of genes encoding proteins controlling mitochondrial functions (PGC1α, PGC1β, NRF1) and anti-oxidant defenses markers (SOD1, SOD2, catalase). CLI resulted in tissue damages and impaired functional scores. Mitochondrial respiration and calcium retention capacity were decreased in the ischemic limb of the non-exercised group (V max = 7.11 ± 1.14 vs. 9.86 ± 0.86 mmol 02/min/g dw, p < 0.001; CRC = 7.01 ± 0.97 vs. 11.96 ± 0.92 microM/mg dw, p < 0.001, respectively). Moderate exercise reduced tissue damages, improved functional scores, and restored mitochondrial respiration and calcium retention capacity in the ischemic limb (V max = 9.75 ± 1.00 vs. 9.82 ± 0.68 mmol 02/min/g dw; CRC = 11.36 ± 1.33 vs. 12.01 ± 1.24 microM/mg dw, respectively). Exercise also enhanced the transcript levels of PGC1α, PGC1β, NRF1, as well as SOD1, SOD2, and catalase. Moderate exercise restores mitochondrial respiration and calcium retention capacity, and it has beneficial functional effects in chronic CLI, likely by stimulating reactive oxygen species-induced biogenesis and anti-oxidant defenses. These data support further development of exercise therapy even in advanced peripheral arterial disease.
Journal of Physical Therapy Science, 2016
To compare measurements of knee extensor and flexor muscle strength performed using a hand-held d... more To compare measurements of knee extensor and flexor muscle strength performed using a hand-held dynamometer and an isokinetic dynamometer in apparently healthy subjects. [Subjects and Methods] Thirty adult volunteers underwent knee muscle strength evaluation using an isokinetic or a hand-held dynamometer. [Results] Strong positive correlations were found between the 2 methods, with correlation coefficients r ranging from 0.72 (95% confidence interval [CI], 0.48-0.86) to 0.87 (95% CI, 0.75-0.94), depending on the muscle group and the isokinetic evaluation mode. The reproducibility of the hand-held dynamometer findings was good, judged by a coefficient of variation of 3.2-4.2%. However, the correlation between the 2 methods for the assessment of flexor/extensor ratios ranged from -0.04 to 0.46. [Conclusion] Knee extensor and flexor muscle strength recorded with a hand-held dynamometer is reproducible and significantly correlated with the isokinetic values, indicating that this method may in some cases be a useful replacement for isokinetic strength measurement. However, for strength ratio assessment, and when judged against the isokinetic standard, a hand-held dynamometer is not a valid option.
Annals of Physical and Rehabilitation Medicine, 2015
Patients and methods Prospective study including 80 obese patients randomized into two groups: a ... more Patients and methods Prospective study including 80 obese patients randomized into two groups: a group of aerobic training (AT) who underwent a training program on treadmill and a group of combined training (CT) who underwent treadmill exercises associated with program of isokinetic strength training of the extensor and flexor muscles of both lower limbs and spine. Evaluation was performed before, one week after, and one year after the end of the protocol. The evaluation comported anthropometric and cardiovascular parameters, muscle strength, dosage of biological parameters and an assessment of psychological status and quality of life. Results After rehabilitation, a significantly greater improvement of anthropometric parameters in the CT were noted compared to AT with an improvement of the weighting reduction of 23.82% in the CT versus 12.3% in the AT group (p < 0.001) and BMI decrease of 19.07% in the CT versus 11.11% in the AT (p < 0.001). The improvement of biological parameters and cardiovascular parameters were also statistically more significant in the RC (p < 0.001). In the two groups amelioration in the peak of torque of both knees and spine extensor and flexor muscles was noted in the three test speeds. This improvement was significantly more important in the RC (p < 0.001). Also, we found an improvement in psychological status and quality of life in the two groups, which was significantly more important in the RC (p < 0.001). The improvement of all parameters was maintained at the first year. Discussion-conclusion Several recent publications have recommended the association of aerobic exercises and muscle strengthening in the rehabilitation to effort of obese . However, no study has particularly used isokinetism as means of muscle strengthening. Our study confirmed the beneficial effect of the combination of isokinetic strength training to aerobic training on anthropometric, biological and cardiovascular parameters well as muscle strength in obese women.
Journal of Applied Physiology, 2019
TO THE EDITOR: We read with interest the Viewpoint of Franchi and Maffiuletti (1). We welcome the... more TO THE EDITOR: We read with interest the Viewpoint of Franchi and Maffiuletti (1). We welcome their call for a better classification of eccentric training modalities. In addition, we would
AJP: Heart and Circulatory Physiology, 2010
The erythrocyte is proposed to play a key role in the control of local tissue perfusion via three... more The erythrocyte is proposed to play a key role in the control of local tissue perfusion via three O2-dependent signaling mechanisms: 1) reduction of circulating nitrite to vasoactive NO, 2) S-nitrosohemoglobin (SNO-Hb)-dependent vasodilatation, and 3) release of the vasodilator and sympatholytic ATP; however, their relative roles in vivo remain unclear. Here we evaluated each mechanism to gain insight into their roles in the regulation of human skeletal muscle blood flow during hypoxia and hyperoxia at rest and during exercise. Arterial and femoral venous hemoglobin O2 saturation (O2Hb), plasma and erythrocyte NO and ATP metabolites, and leg and systemic hemodynamics were measured in 10 healthy males exposed to graded hypoxia, normoxia, and graded hyperoxia both at rest and during submaximal one-legged knee-extensor exercise. At rest, leg blood flow and NO and ATP metabolites in plasma and erythrocytes remained unchanged despite large alterations in O2Hb. During exercise, however, l...
Antioxidants
Currently, no studies have examined the differences in endogenous antioxidant enzymes in professi... more Currently, no studies have examined the differences in endogenous antioxidant enzymes in professional and amateur cyclists and how these can influence sports performance. The aim of this study was to identify differences in endogenous antioxidants enzymes and hemogram between competitive levels of cycling and to see if differences found in these parameters could explain differences in performance. A comparative trial was carried out with 11 professional (PRO) and 15 amateur (AMA) cyclists. All cyclists performed an endogenous antioxidants analysis in the fasted state (visit 1) and an incremental test until exhaustion (visit 2). Higher values in catalase (CAT), oxidized glutathione (GSSG) and GSSG/GSH ratio and lower values in superoxide dismutase (SOD) were found in PRO compared to AMA (p < 0.05). Furthermore, an inverse correlation was found between power produced at ventilation thresholds 1 and 2 and GSSG/GSH (r = −0.657 and r = −0.635; p < 0.05, respectively) in PRO. Theref...
Journal of Applied …, 2006
This study investigates whether adaptations of mitochondrial function accompany the improvement o... more This study investigates whether adaptations of mitochondrial function accompany the improvement of endurance performance capacity observed in well-trained athletes after an intermittent hypoxic training program. Fifteen endurance-trained athletes performed two weekly training ...
AJP: Regulatory, Integrative and Comparative Physiology, 2008
The goal of the study was to determine the effects of continuous (CT) vs. intermittent (IT) train... more The goal of the study was to determine the effects of continuous (CT) vs. intermittent (IT) training yielding identical mechanical work and training duration on skeletal muscle and cardiorespiratory adaptations in sedentary subjects. Eleven subjects (6 men and 5 women, 45 ± 3 years) were randomly assigned to either of the two 8-wk training programs in a cross-over design, separated by 12 wk of detraining. Maximal oxygen uptake (V̇o2max) increased after both trainings (9% with CT vs. 15% with IT), whereas only IT was associated with faster V̇o2 kinetics (τ: 68.0 ± 1.6 vs. 54.9 ± 0.7 s, P < 0.05) measured during a test to exhaustion (TTE) and with improvements in maximal cardiac output (Qmax, from 18.1 ± 1.1 to 20.1 ± 1.2 l/min; P < 0.01). Skeletal muscle mitochondrial oxidative capacities ( Vmax) were only increased after IT (3.3 ± 0.4 before and 4.5 ± 0.6 μmol O2·min−1·g dw−1 after training; P < 0.05), whereas capillary density increased after both trainings, with a two-fol...
Journal of applied physiology (Bethesda, Md. : 1985), 2018
mance has often been observed after resistance training (RT) (4). Based on the critical power (CP... more mance has often been observed after resistance training (RT) (4). Based on the critical power (CP) concept, Denadai and Greco (1) recently proposed an interesting model to explain this RT-induced improvement in endurance performance. According to these authors, the gains (35-60%) in the curvature constant of the power-duration hyperbola (W=) could explain the performance improvements during constant-workload exercises performed above the CP after a RT program. However, it is important to highlight that during most athletic events, the intensity of the exercise is not previously fixed, but self-selected by the athletes. The intensity distribution during middle-and long-distance running races has often been characterized by a U-shaped pacing profile, with start and finish intensities being higher than in the middle part of the race (5). This U-shaped pacing makes the W= use more complex, because athletes might switch from one exercise intensity domain to another throughout the race (3). This could indicate that the increase in W= with RT might be more relevant for some specific parts of the race, in which athletes perform at intensities above the CP, such as during the fast start and the final sprint. This suggestion is in agreement with previous findings showing that RT can counteract fatigue during the last part of a running race (2). Therefore, further research in this exciting area is necessary to elucidate the influence of RT on W= and its possible relationship with changes in specific parts of self-paced, real races.
Cardio-respiratory responses to hypoxia combined with CO2 inhalation during maximal exercise
Respiratory physiology & neurobiology, 2017
We measured the effects of adding CO2 to an inhaled hypoxic gas mixture on cardio-respiratory par... more We measured the effects of adding CO2 to an inhaled hypoxic gas mixture on cardio-respiratory parameters during maximal exercise. Eight young males performed four incremental maximal exercise tests on cycle under ambient air, hypoxia (FIO2 0.125), inhaled CO2 (FICO2 0.045), and combination of hypoxia and inhaled CO2. The highest ventilation (VE) and VE/CO2 output were recorded in CO2 inhalation and combined treatments. Arterial O2 partial pressure was higher in combined than in hypoxia treatment, but the difference between the treatments narrowed from rest to end-exercise, at least partly because the magnitude of the increase in VE (%) at exercise was smaller in combined treatment than in hypoxia. Arterial O2 content was higher in combined treatment than in hypoxia at rest, but no more at maximal exercise. Cardiac output was higher and O2 extraction lower when breathing O2-poor gas mixtures than under the two other treatments. For a given oxygen consumption, hypoxia and combined tre...
Biochemical responses and physical performance during high-intensity resistance circuit training in hypoxia and normoxia
European Journal of Applied Physiology, 2017
The aim of this study was to analyze the effect of hypoxia on metabolic and acid-base balance, bl... more The aim of this study was to analyze the effect of hypoxia on metabolic and acid-base balance, blood oxygenation, electrolyte, and half-squat performance variables during high-resistance circuit (HRC) training. Twelve resistance-trained subjects participated in this study. After a 6RM testing session, participants performed three randomized trials of HRC: normoxia (NORM: FiO2 = 0.21), moderate hypoxia (MH: FiO2 = 0.16), or high hypoxia (HH: FiO2 = 0.13), separated by 72 h of recovery in normoxic conditions. HRC consisted of two blocks of three exercises (Block 1: bench press, deadlift and elbow flexion; Block 2: half-squat, triceps extension, and ankle extension). Each exercise was performed at 6RM. Rest periods lasted for 35 s between exercises, 3 min between sets, and 5 min between blocks. Peak and mean force and power were determined during half-squat. Metabolic, acid-base balance, blood oxygenation and electrolyte variables, arterial oxygen saturation (SaO2), and rating of perceived exertion (RPE) were measured following each block. During the first set, peak force and power were significantly lower in HH than MH and NORM; whereas in the second set, mean and peak force and power were significantly lower in HH than NORM. At the end of the HRC training session, blood lactate and RPE in HH were significantly higher than in MH and NORM. SaO2, pH, HCO3(-), and pO2 values were significantly lower in all hypoxic conditions than in NORM. These results indicate that simulated hypoxia during HRC exercise reduce blood oxygenation, pH, and HCO3(-,) and increased blood lactate ultimately decreasing muscular performance.
High-Force Versus Low-Force Lumbar Traction in Acute Lumbar Sciatica Due to Disc Herniation: A Preliminary Randomized Trial
Journal of Manipulative and Physiological Therapeutics, 2016
This study compared the effects of high-force versus low-force lumbar traction in the treatment o... more This study compared the effects of high-force versus low-force lumbar traction in the treatment of acute lumbar sciatica secondary to disc herniation. A randomized double blind trial was performed, and 17 subjects with acute lumbar sciatica secondary to disc herniation were assigned to high-force traction at 50% body weight (BW; LT50, n = 8) or low force traction at 10% BW (LT10, n = 9) for 10 sessions in 2 weeks. Radicular pain (visual analogue scale [VAS]), lumbo-pelvic-hip complex motion (finger-to-toe test), lumbar-spine mobility (Schöber-Macrae test), nerve root compression (straight-leg-raising test), disability (EIFEL score), drug consumption, and overall evaluation of each patient were measured at days 0, 7, 1, 4, and 28. Significant (P &lt; .05) improvements were observed in the LT50 and LT10 groups, respectively, between day 0 and day 14 (end of treatment) for VAS (-44% and -36%), EIFEL score (-43% and -28%) and overall patient evaluation (+3.1 and +2.0 points). At that time, LT50 specifically improved in the finger-to-toe test (-42%), the straight-leg-raising test (+58), and drug consumption (-50%). No significant interaction effect (group-by-time) was revealed, and the effect of traction treatment was independent of the level of medication. During the 2-week follow-up at day 28, only the LT10 group improved (P &lt; .05) in VAS (-52%) and EIFEL scores (-46%). During this period, no interaction effect (group-by-time) was identified, and the observed responses were independent of the level of medication. For this preliminary study, patients with acute lumbar sciatica secondary to disc herniation who received 2 weeks of lumbar traction reported reduced radicular pain and functional impairment and improved well-being regardless of the traction force group to which they were assigned. The effects of the traction treatment were independent of the initial level of medication and appeared to be maintained at the 2-week follow-up.
Improvement of VO2 max, by cardiac output and oxygen extraction adaptation during intermittent versus continuous endurance training
European Journal of Applied Physiology, 2007
Improvement of exercise capacity by continuous (CT) versus interval training (IT) remains debated... more Improvement of exercise capacity by continuous (CT) versus interval training (IT) remains debated. We tested the hypothesis that CT and IT might improve peripheral and/or central adaptations, respectively, by randomly assigning 10 healthy subjects to two periods of 24 trainings sessions over 8 weeks in a cross-over design, separated by 12 weeks of detraining. Maximal oxygen uptake (VO2max), cardiac output (Qmax) and maximal arteriovenous oxygen difference (Da-vO2max) were obtained during an exhaustive incremental test before and after each training period. VO2max and Qmax increased only after IT (from 26.3 +/- 1.6 to 35.2 +/- 3.8 ml min(-1) kg(-1) and from 17.5 +/- 1.3 to 19.5 +/- 1.8 l min(-1), respectively; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). Da-vO2max increased after both protocols (from 11.0 +/- 0.8 to 12.7 +/- 1.0; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01 and from 11.0 +/- 0.8 to 12.1 +/- 1.0 ml 100 ml(-1), P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05 in CT and IT, respectively). At submaximal intensity a significant rightward shift of the Q/Da-vO2 relationship appeared only after CT. These results suggest that in isoenergetic training, central and peripheral adaptations in oxygen transport and utilization are training-modality dependant. IT improves both central and peripheral components of Da-vO2max whereas CT is mainly associated with greater oxygen extraction.
Errors in facts and logic: what else?
European Journal of Applied Physiology, 2009
Optimisation de la performance aérobie chez l'athlète : Hypoxie intermittente à l'exercice et ergocycle excentrique comme nouvelles approches de stimulations métaboliques et mécaniques
Http Www Theses Fr, 2005
Page 1. UNIVERSITE DE STRASBOURG I LOUIS PASTEUR Année universitaire 2004/2005 N° attribué par ... more Page 1. UNIVERSITE DE STRASBOURG I LOUIS PASTEUR Année universitaire 2004/2005 N° attribué par la bibliothèque : Thèse présentée pour obtenir le grade de Docteur de l&amp;#x27;Université Louis Pasteur Strasbourg I Discipline : Sciences du Vivant ...
Mitochondrial function following downhill and/or uphill exercise training in rats
Muscle & Nerve, 2016
The goal of this study was to compare the effects of downhill (DH), uphill (UH), and UH-DH exerci... more The goal of this study was to compare the effects of downhill (DH), uphill (UH), and UH-DH exercise training, at the same metabolic rate, on exercise capacity and skeletal muscle mitochondrial function. Thirty-two Wistar rats were separated into a control and 3 trained groups. The trained groups exercised for 4 weeks, 5 times per week at the same metabolic rate, either in UH, DH, or combined UH-DH. Twenty-four hours after the last training session, the soleus, gastrocnemius, and vastus intermedius muscles were removed for assessment of mitochondrial respiration. Exercise training, at the same metabolic rate, improved maximal running speed without specificity for exercise modalities. Maximal fiber respiration was enhanced in soleus and vastus intermedius in the UH group only. Exercise training, performed at the same metabolic rate, improved exercise capacity, but only UH-trained rats enhanced mitochondrial function in both soleus and vastus intermedius skeletal muscle. This article is protected by copyright. All rights reserved.
Comparative study on the assessment of the strength of the knee extensor and flexor muscles by hand-held dynamometer and isokinetic dynamometer
Annals of Physical and Rehabilitation Medicine, 2015
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Papers by Stephane Dufour