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International audience; ObjectiveThe aim of this study was to develop specific prediction equations based on acceleration data measured at three body sites for estimating energy expenditure (EE) during static and active conditions in middle-aged and older adults with and without type 2 diabetes (T2D).Research methodsForty patients with T2D (age: 40–74 yr, body mass index (BMI): 21–29.4 kg·m−2) and healthy participants (age: 47–79 yr, BMI: 20.2–29.8 kg·m−2) completed trials in both static conditions and treadmill walking. For all trials, gas exchange was monitored using indirect calorimetry and vector magnitude was calculated from acceleration data measured using inertial measurement units placed to the participant's center of mass (CM), hip and ankle. Stepwise multiple regression analyses were conducted to select relevant variables to include in the three EE prediction equations, and three Monte Carlo cross-validation procedures were used to evaluate each separate equation.ResultsVector magnitude (p < 0.0001) and personal data (gender, diabetes status and BMI; p < 0.0001) were used to develop three linear prediction equations to estimate EE during static conditions and walking. Cross-validation revealed similar robust coefficients of determination (R2: 0.81 to 0.85) and small bias (mean bias: 0.008 to −0.005 kcal·min−1) for all three equations. However, the equation based on CM acceleration exhibited the lowest root mean square error (0.60 kcal·min−1 vs. 0.65 and 0.69 kcal·min−1 for the hip and ankle equations, respectively; p < 0.001).ConclusionThe three equations based on acceleration data and participant characteristics accurately estimated EE during sedentary conditions and walking in middle-aged and older adults, with or without diabetes.

IntroductionDepression is among the most widespread psychiatric disorders in France. Psychiatric disorders are associated with considerable social costs, amounting to €22.6 billion for treatment and psychotropic medication in 2011. Treatment as usual (TAU), mainly consisting of pharmacotherapy and psychotherapy, is effective for only a third of patients and in most cases fails to prevent treatment resistance and chronicity. Transcranial direct current stimulation (tDCS) consists in a non-invasive and painless application of low-intensity electric current to the cerebral cortex through the scalp. Having proved effective in depressed patients, it could be used in combination with TAU to great advantage. The objective is to compare, for the first time ever, the cost-utility of tDCS-TAU and of TAU alone for the treatment of a depressive episode that has been refractory to one or two drug treatments.Methods and analysisThis paper, based on the DISCO study protocol, focuses on the design of a prospective, randomised, controlled, open-label multicentre economic study to be conducted in France. It will include 214 patients with unipolar or bipolar depression, assigning them to two parallel arms: group A (tDCS-TAU) and group B (TAU alone). The primary outcome is the incremental cost-effectiveness ratio, that is, the ratio of the difference in cost between each strategy to the difference in their effects. Their effects will be expressed as numbers of quality-adjusted life-years, determined through administration of the EuroQol Five-Dimension questionnaire over a 12-month period to patients (EQ-5D-5L). Expected benefits are the reduction of treatment resistance and suicidal ideation as well as social and professional costs of depression. Should depression-related costs fall significantly, tDCS might be considered an efficient treatment for depression.Ethics and disseminationThis protocol has been approved by a French ethics committee, the CPP-–Est IV (Comité de Protection des Personnes–Strasbourg). Data are to be published in peer-reviewed medical journals.Trial registration numberRCB 2018-A00474-51;NCT03758105

Purpose The purpose of this study was to investigate bone microarchitecture of cadaveric proximal femurs using ultra-high field (UHF) 7-Tesla magnetic resonance imaging (MRI) and to compare the corresponding metrics with failure load assessed during mechanical compression test and areal bone mineral density (ABMD) measured using dual-energy X-ray absorptiometry. Materials and methods ABMD of ten proximal femurs from five cadavers (5 women; mean age = 86.2 ± 3.8 (SD) years; range: 82.5–90 years) were investigated using dual-energy X-ray absorptiometry and the bone volume fraction, trabecular thickness, trabecular spacing, fractal dimension, Euler characteristics, connectivity density and degree of anisotropy of each femur was quantified using UHF MRI. The whole set of specimens underwent mechanical compression tests to failure. The inter-rater reliability of microarchitecture characterization was assessed with the intraclass correlation coefficient (ICC). Associations were searched using correlation tests and multiple regression analysis. Results The inter-rater reliability for bone microarchitecture parameters measurement was good with ICC ranging from 0.80 and 0.91. ABMD and the whole set of microarchitecture metrics but connectivity density significantly correlated with failure load. Microarchitecture metrics correlated to each other but did not correlate with ABMD. Multiple regression analysis disclosed that the combination of microarchitecture metrics and ABMD improved the association with failure load. Conclusion Femur bone microarchitecture metrics quantified using UHF MRI significantly correlated with biomechanical parameters. The multimodal assessment of ABMD and trabecular bone microarchitecture using UHF MRI provides more information about fracture risk of femoral bone and might be of interest for future investigations of patients with undetected osteoporosis.

Although it is known that the muscle activation patterns used to produce even simple movements can vary between individuals, these differences have not been considered to prove the existence of individual muscle activation strategies (or signatures). We used a machine learning approach (support vector machine) to test the hypothesis that each individual has unique muscle activation signatures. Eighty participants performed a series of pedaling and gait tasks, and 53 of these participants performed a second experimental session on a subsequent day. Myoelectrical activity was measured from eight muscles: vastus lateralis and medialis, rectus femoris, gastrocnemius lateralis and medialis, soleus, tibialis anterior, and biceps femoris -long head. The classification task involved separating data into training and testing sets. For the within-day classification, each pedaling/gait cycle was tested using the classifier, which had been trained on the remaining cycles. For the between-day classification, each cycle from day 2 was tested using the classifier, which had been trained on the cycles from day 1. When considering all eight muscles, the activation profiles were assigned to the corresponding individuals with a classification rate of up to 99.28% (2,353/2,370 cycles) and 91.22% (1,341/1,470 cycles) for the within-day and between-day classification, respectively. When considering the within-day classification, a combination of two muscles was sufficient to obtain a classification rate >80% for both pedaling and gait. When considering between-day classification, a combination of four to five muscles was sufficient to obtain a classification rate >80% for pedaling and gait. These results demonstrate that strategies not only vary between individuals, as is often assumed, but are unique to each individual. NEW & NOTEWORTHY We used a machine learning approach to test the uniqueness and robustness of muscle activation patterns. We considered that, if an algorithm can accurately identify participants, one can conclude that these participants exhibit discernible differences and thus have unique muscle activation signatures. Our results show that activation patterns not only vary between individuals, but are unique to each individual. Individual differences should, therefore, be considered relevant information for addressing fundamental questions about the control of movement.

We hypothesized that shear wave elastography (SWE) technology might be useful for assessing the elastic properties of the pelvic floor in women. Our primary objective was to evaluate the feasibility of assessing the levator ani muscles using SWE in women. Our secondary aim was to investigate the changes in their elastic properties from rest to Valsalva maneuver. During this prospective feasibility study in nonpregnant female volunteers, we collected data on participant age, body mass index (BMI), parity, and time since the delivery. The levator ani muscles of each participant were assessed using SWE technology at rest and during a Valsalva maneuver by measuring the shear modulus (in kilopascals). We then assessed the changes in the shear modulus at rest and during the Valsalva maneuver using a Wilcoxon test. Twelve parous women participated in this study. The mean time since the last delivery was 14 months, the mean age was 31 years, and mean BMI was 28 kg.m−2. All the assessments performed at rest were successfully completed, but we encountered two failures during the Valsalva maneuver. The mean shear modulus increased by a factor of more than 2 from rest to the Valsalva maneuver for both the right (16.0 vs 35.4 kPa) and left side (17.1 vs 37.6 kPa). An assessment of the elastic properties of the levator ani muscles is feasible for nonpregnant women. The reproducibility of the technique and its application in pregnant women and women with pelvic floor disorders must be investigated.

Objective: This paper describes a sequential decomposition algorithm for single-channel intramuscular electromyography (iEMG) generated by a varying number of active motor neurons. Methods: As in previous work, we establish a hidden Markov model of iEMG, in which each motor neuron spike train is modeled as a renewal process with inter-spike intervals following a discrete Weibull law and motor unit action potentials are modeled as impulse responses of linear time-invariant systems with known prior. We then expand this model by introducing an activation vector associated with the state vector of the hidden Markov model. This activation vector represents recruitment/derecruitment of motor units and is estimated together with the state vector using Bayesian filtering. Non-stationarity of the model parameters is addressed by means of a sliding window approach, thus making the algorithm adaptive to variations in contraction force and motor unit action potential waveforms. Results: The algorithm was validated using simulated and experimental iEMG signals with varying number of active motor units. The experimental signals were acquired from the tibialis anterior and abductor digiti minimi muscles by fine wire and needle electrodes. The decomposition accuracy in both simulated and experimental signals exceeded 90%. Conclusion: The recruitment/derecruitment was successfully tracked by the algorithm. Because of its parallel structure, this algorithm can be efficiently accelerated, which lays the basis for its real-time applications in human–machine interfaces. Significance: The proposed method substantially broadens the domains of applicability of the algorithm.

Standard outcomes of traditional isokinetic testing do not detect differences between various muscle mechanical properties. This study i) explored a novel analysis throughout the range of motion based on statistical parametric mapping and ii) examined the impact of sex and discipline on hamstrings/quadriceps torque in elite alpine skiers. Twenty-eight national team skiers (14 females, 14 males; 14 technical, 14 speed) undertook an isokinetic evaluation of the knee flexors/extensors (range 30–90°, 0° representing full extension). There was no effect of sex (p=0.864, d=0.03) and discipline (p=0.360, d=0.17) on maximal hamstrings-to-quadriceps ratio and no effect of discipline on maximal torque (p>0.156, d≤0.25). Hamstrings torque and hamstrings-to-quadriceps ratio were lower in females than males toward knee extension only (p

Background The individual effects of fatigue and age on postural control have been extensively studied. However, there is a lack of knowledge about the combined effects of fatigue and age on postural control and posture. Research question The purpose of this study was to investigate the influence of age and muscle fatigue on bipedal stance postural control and posture. Methods Twenty-three participants, fourteen young adults and nine older adults performed 30-s bipedal postural trials before and after fatigue. The fatigue protocol consisted in repeating heel raises until exhaustion. Back, hip, knee and ankle joint angles and centre of pressure (COP) displacements were recorded with a 3D motion capture system and a force plate. Results Fatigue induced similar increases in sway area and COP velocity for both populations. This was associated with a forward displacement of the COP position for both populations but with different postural adaptations. Similar increased flexions (+1.7 to 1.8°) for all joint angles (ankle, knee, hip and back) joints were observed after fatigue for older adults, whereas young adults mainly showed increased flexion for the ankle joint (+3.1°) and decreased flexion at the hip (−1.2°). Significance It can be argued that older adults act on all joints because they are too weak to sufficiently modify any joint individually, contrary to young adults. These posture adaptations may be strategies to cope with fatigue by limiting the reliance on fatigued plantarflexors, increasing ankle stiffness, increasing the sensitivity of muscle spindles, increasing the number of degrees of freedom of the task.

Purpose:The aim of the current study was to determine whether the anaerobic performance assessed by a modified Wingate test could account for the 1,500-m rowing ergometer performance in young competitive rowers.Methods:Fourteen national-level adolescent rowers performed on a rowing ergometer i) a 30-s allout exercise (i.e., modified Wingate test) and ii) a 1,500-m all-out exercise (i.e., rowing performance). For each of these two exercises, the mean power output was considered as the main performance criterion (PWIN and P1500, respectively).Results:PWIN was correlated to P1500 (r2 = .83, p < .0001, β = 100%). Furthermore, the estimated total muscle mass was correlated to PWIN and P1500 (r2 = .72 and r2 = .83, p < .0001, β = 100%, respectively). The allometric scaling also indicated that total muscle mass accounts 62% for the relationship between PWIN and P1500.Conclusion:Our results highlight the importance of considering the contribution of total muscle mass and anaerobic energy pathways to 1,500-m rowing performance in competitive adolescent rowers. Therefore, the modified Wingate test could be used by rowing coaches to potentially identify talented young rowers.

International audience; Purpose As a subjective symptom, cancer-related fatigue is assessed via patient-reported outcomes. Due to the inherent bias of such evaluation, screening and treatment for cancer-related fatigue remains suboptimal. The purpose is to evaluate whether objective cancer patients' hand muscle mechanical parameters (maximal force, critical force, force variability) extracted from a fatiguing handgrip exercise may be correlated to the different dimensions (physical, emotional, and cognitive) of cancer-related fatigue. Methods Fourteen women with advanced breast cancer, still under or having previously received chemotherapy within the preceding 3 months, and 11 healthy women participated to the present study. Cancer-related fatigue was first assessed through the EORTC QLQ-30 and its fatigue module. Fatigability was then measured during 60 maximal repeated handgrip contractions. The maximum force, critical force (asymptote of the force-time evolution), and force variability (root mean square of the successive differences) were extracted. Multiple regression models were performed to investigate the influence of the force parameters on cancer-related fatigue's dimensions. Results The multiple linear regression analysis evidenced that physical fatigue was best explained by maximum force and critical force (r = 0.81; p = 0.029). The emotional fatigue was best explained by maximum force, critical force, and force variability (r = 0.83; p = 0.008). The cognitive fatigue was best explained by critical force and force variability (r = 0.62; p = 0.035). Conclusion The handgrip maximal force, critical force, and force variability may offer objective measures of the different dimensions of cancer-related fatigue and could provide a complementary approach to the patient reported outcomes.

International audience; Aim: Defining the origins of muscle injury has important rehabilitation and exercise applications. However, current knowledge of muscle damage mechanics in human remains unclear in vivo. This study aimed to determine the relationships between muscle–tendon unit mechanics during maximal eccentric contractions and the extent of subsequent functional impairments induced by muscle damage.Methods: The length of the muscle–tendon unit, fascicles and tendinous tissues was continuously measured on the gastrocnemius medialis using ultrasonography, in time with torque, during 10 sets of 30 maximal eccentric contractions of plantar flexors at 45°s -1, in seventeen participants.Results: Muscle–tendon unit, fascicles and tendinous tissues were stretched up to 4.44 ± 0.33 cm, 2.31 ± 0.64 cm and 1.92 ± 0.61 cm respectively. Fascicle stretch length, lengthening amplitude and negative fascicle work beyond slack length were significantly correlated with the force decrease 48 h post-exercise (r=0.51, 0.47 and 0.68, respectively; P

Summary Objectives Due to its ease of use, tolerance, and cost of acquisition, transcranial direct current stimulation (tDCS) could constitute a credible therapeutic option for non-resistant depression in primary care, when combined with drug management. This indication has yet to receive official recognition in France. The objective of this study is to evaluate the production cost of tDCS for the treatment of depression in hospitals, under realistic conditions. Methods The methodology adopted is based on cost accounting and was validated by a multidisciplinary working group. It includes equipment, staff, and structural costs to obtain the most realistic estimate possible. We first estimated the cost of producing a tDCS session, based on our annual activity objective, and then estimated the cost of a 15-session treatment program. This was followed up with a sensitivity analysis applying appropriate parameters. Results The hospital production cost of a tDCS depression treatment program for a single patient was estimated at €1555.60 euros: €99 in equipment costs, €1076.95 in staff costs, and €379.65 in structural costs. Conclusion This cost analysis should make it possible to draw up pricing proposals in compliance with regulations and health policy choices and to develop health-economic studies. This would ultimately lead to official recognition of tDCS treatment for depression in France and pave the way for studying various scenarios of coverage by the French national health insurance system.

Objective The aim of the study was to investigate the influence of age and/or obesity on postural control, ankle muscle activities during balance testing and force production capacities. Materials and methods 4 groups; control group (CG; n = 25; age = 31.8 ± 7.5 years; BMI = 21.4 ± 2.5 kg/m2), obese group (OG; n = 25; age = 34.4 ± 9.5 years; BMI = 39.6 ± 5.4 kg/m2), elderly group (EG; n = 15; age = 77.1 ± 8.4 years; BMI = 24.4 ± 1.3 kg/m2) and obese elderly group (ObEG; n = 12; age = 78.6 ± 6.6 years; BMI = 34.5 ± 3.1 kg/m2) performed maximal voluntary contraction (MVC) before testing to calculate the maximal relative force of ankle plantar flexor (PF) and dorsal flexor (DF) muscles. Center of pressure (CoP) parameters and the electromyography (EMG) activity of PF and DF muscles were collected during MVC, quiet standing and limit of stability (LoS) testing along antero-posterior and medio-lateral axes. Results Maximal relative force was higher in EG and ObEG than CG and OG, respectively (p 0.6; p −0.6; p Conclusion Obesity-related postural control alteration is associated with increased activity of PF. This neuromuscular adaptation may reflect deteriorations of the proprioceptive system and is likely additional to age-related muscular impairments. This may be a mechanism by which obesity increases postural control alterations in elderly.

Summary Aims The aim of the study was to assess mechanical muscle capacities and profiles of well-trained soccer goalkeepers playing at a national amateur level. Methods Eleven goalkeepers (from 4th French division) performed vertical jump tests and series of loaded half squat and bench throw tests to assess lower and upper limbs force-velocity profiles, respectively. Force, velocity and power produced during each exercise were determined using a guided barbell. Maximal theoretical velocity and maximal theoretical force were determined from the force-velocity profiles. Slopes of those profiles were also calculated. Results Vertical jump performances were 38.5 ± 4.5 cm for the squat jump and 41.6 ± 5.5 cm for the countermovement jump. Lower limbs stiffness was 304.2 ± 55.1 N.m−1.kg−1. Lower limbs force-velocity profile was described by a slope of −11.5 ± 4.0 N.s.m−1.kg−1, with maximal theoretical force and velocity reaching 34.3 ± 5.9 N.kg−1 and 3.2 ± 0.2 m.s−1, respectively. Upper limbs muscular profile was described by a slope of −3.7 ± 1.1 N.s.m−1.kg−1, with maximal theoretical force and velocity of 13.6 ± 3.7 N.kg−1 and 3.7 ± 0.6 m.s−1, respectively. These values reveal that goalkeepers’ muscles profiles are oriented towards velocity. Conclusion This suggests that whatever the goalkeepers’ level, specific and conditioning trainings should mainly focus on velocity to optimize the performance of this specific soccer player.

This study aimed to assess the influence of an adapted physical activity program on self-esteem and quality of life in breast cancer patients. Twenty-three women diagnosed with breast cancer and treated by mastectomy formed 2 groups. The experimental group practiced adapted physical activity for 12 weeks, while the control group did not. All participants answered questionnaires regarding their self-esteem and quality of life at the beginning of the program and 6 and 12 weeks after that. Self-esteem, physical self-perception, quality of life, global health status, pain, and breast symptoms were improved only in the group which practiced adapted physical activity.

International audience

Upper limb abilities can be assessed from different kinds of exercises (e.g., cranking, push-up, and medicine ball put test). Since the bench press is a very common exercise used in training routines by most athletes in many sports, its interest in the scientific literature raised in the past two decades. As presented in previous chapters during jumping or cycling, from several bench presses performed against different loads, coaches and athletes can simply and accurately define their upper limb force-velocity (F-v) profile. They can estimate their theoretical maximal force (F 0), velocity (V 0) and power (P max ). The aim of this chapter is to present the important points that must be taken into account to optimize the use of the bench press as a routine testing. In a first part, this chapter will focus on the importance of taking into consideration all the mechanical inertia involved in the bench press exercise. Not considering the upper limb mass in the calculation of the force produced during the exercise implies an underestimation in the F-v profile that can reach 30% for P max . This could conduct to incorrect choices in the optimal load during training and thus limit the performance improvement. In the second part of this chapter, we present a simple mechanical model of the bench press to study the importance of the upper limb acceleration in the estimation of the force produced. The moving system (i.e., lifted mass and upper limbs) is modeled from rigid segments and the force can be determined thanks to four simple measurements: the vertical displacement of the lifted load, the elbow angle measured using a goniometer, the arm and forearm lengths and the constant horizontal position of the hand on the barbell. The validity of this model has been confirmed through experimental data obtained from a force platform. An important point is that the kinematics and kinetics of this model allow demonstrating that the acceleration of the moving system is similar to the one of the barbell. Finally, based on the previous statement, the last part of this chapter presents a simple method for assessing force, velocity and power during a ballistic bench press performed on a traditional guided barbell, based on the Newtonian laws and only three simple parameters: (i) upper limb mass estimated as 10% of the body mass; (ii) barbell flight height recorded with a nylon cable tie and (iii) push-off distance measured with a measuring tape. Consequently, coaches and athletes could accurately determine their F-v profile and extrapolate reliable mechanical parameters (F 0 , v 0, Sfv and P max ) in order to maximize upper limbs performance and manage training programs in field conditions.

International audience; This study introduces local pattern texture anisotropy as a novel parameter to differentiate healthy and disordered muscle and to gauge the severity of muscle impairments based on B-mode ultrasound images. Preliminary human results are also presented. A local pattern texture anisotropy index (TAI) was computed in one region of interest in the short head of the biceps brachii. The effects of gain settings and box sizes required for TAI computation were investigated. Between-day reliability was studied in patients with sporadic inclusion body myositis (n = 26). The ability of the TAI to discriminate dystrophic from healthy muscle was evaluated in patients with Duchenne muscular dystrophy and healthy controls (n = 16). TAI values were compared with a gray-scale index (GSI). TAI values were less influenced by gain settings than were GSI values. TAI had lower between-day variability (typical error = 2.3%) compared with GSI (typical error = 2.3% vs. 8.3%, respectively). Patients with Duchenne muscular dystrophy had lower TAIs than controls (0.76 ± 0.06 vs. 0.87 ± 0.03, respectively, p

Maciejewski, H, Rahmani, A, Chorin, F, Lardy, J, Samozino, P, and Ratel, S. Methodological considerations on the relationship between the 1,500-m rowing ergometer performance and vertical jump in national-level adolescent rowers. J Strength Cond Res 33(11): 3000-3007, 2019-The purpose of this study was to investigate whether 3 different approaches for evaluating squat jump performance were correlated with rowing ergometer performance in elite adolescent rowers. Fourteen young male competitive rowers (15.3 ± 0.6 years), who took part in the French rowing national championships, performed a 1,500-m all-out rowing ergometer performance (P1500) and a squat jump (SJ) test. The performance in SJ was determined by calculating the jump height (HSJ in cm), a jump index (ISJ = HSJ·body mass·gravity, in J), and the mean power output (PSJ in W) from the Samozino et al.'s method. Furthermore, allometric modeling procedures were used to consider the importance of body mass (BM) in the relationships between P1500 and jump scores. P1500 was significantly correlated with HSJ (r = 0.29, p ≤ 0.05), ISJ (r = 0.72, p < 0.0001), and PSJ (r = 0.86, p < 0.0001). Furthermore, BM explained at least 96% of the relationships between SJ and rowing performances. However, the similarity between both allometric exponents for PSJ and P1500 (1.15 and 1.04, respectively) indicates that BM could influence jump and rowing ergometer performances at the same rate, and that PSJ could be the best correlate of P1500. Therefore, the calculation of power seems to be more relevant than HSJ and ISJ to (a) evaluate jump performance and (b) infer the capacity of adolescent rowers to perform 1,500-m all-out rowing ergometer performance, irrespective of their body mass. This could help coaches to improve their training program and potentially identify talented young rowers.

International audience; This study aimed at evaluating the effects of mental and muscle fatigue on table tennis performance. Mental fatigue (MF) was induced by completion of 90minutes of the AX-CPT; muscle fatigue was induced by completion of an eccentric exercise performed with the elbow flexors (biceps fatigue, BF) or the knee extensors (quadriceps fatigue, QF). The control condition consisted of watching a movie. Stroke parameters (speed and accuracy of the ball), as well as feelings of fatigue and force production capacity of the elbow flexors (BF, MF and control conditions) and knee extensors (QF condition), were assessed pre and post fatigue protocols. Feelings of fatigue increased post fatigue protocols. Force production capacity decreased only in the BF and QF conditions. BF and MF induced a decrease in accuracy. This decrease in accuracy was associated with an increased ball speed in the BF condition, and a decreased ball speed in the MF condition. QF had a negligible effect on stroke performance. Our results suggest that both mental fatigue, and muscle fatigue, significantly impair table tennis performance and therefore coaches should take into account both the physical and mental state of table tennis players to optimize performance.

International audience; Introduction Because the hand joints possess a broad range of motion, the muscle length can vary importantly which might result in significant variations of the muscle force-generating capacities. However, facing the complexity of this musculoskeletal system, no study has examined the effect of hand muscle length change on muscle force. This study aimed to characterize the force-length relationship of muscles involved in wrist and metacarpophalangeal flexion.Methods Eleven participants performed two sessions: (i) one for the wrist flexor muscles and (ii) one for the finger flexor muscles. For each session, the participants performed two maximal voluntary contractions and then two progressive isometric ramps from 0% to 100% of their maximal force capacity at five different wrist/metacarpophalangeal angles. Torque, kinematic, and electromyographic data were recorded. An ultrasound scanner was used to measure the myotendinous junction displacement of flexor carpi radialis (FCR) and flexor digitorum superficialis (FDS) during isometric contractions. A three-dimensional relationship between muscle length, force, and activation level was modeled using optimization procedure.Results Globally, the FCR was stronger and shorter compared with FDS. The results showed that the three-dimensional relationships fitted well the experimental data (mean R-2 = 0.92 0.07 and 0.87 +/- 0.11 for FCR and FDS, respectively). Using joint angle and EMG data, this approach allows to estimate the muscle force with low estimation errors (9% of F-max).Conclusions This study proposes a new method to investigate the force-length relationship by combining ultrasound measurement, musculoskeletal modeling and optimization procedures. The data and relationships provide a new insight into hand biomechanics and muscle function that could be useful for designing hand tools or surgical operations.

Rowing races require developing high level of force and power output at high contraction velocity. This study determined the force-velocity and power-velocity (F-P-V) profiles of lower and upper limbs of adolescent rowers and their relationships with a 1,500-m rowing ergometer performance. The power developed during the 1,500-m (P1500) was evaluated in fourteen national-level male rowers (age: 15.3±0.6 yrs). F-P-V profiles were assessed during bench pull (BP) and squat jump (SJ) exercises. The theoretical maximal values of force (F0), velocity (V0), power output (Pmax) and the F-V relationship slope (S FV ) were determined. The body mass (BM) influence on these relationships was considered using an allometric approach. F0 was 720±144 and 2146±405 N, V0 was 1.8±0.1 and 1.8±0.3 m·s−1, Pmax was 333±83 and 968±204 W and SFV was −391±54 and −1,200±260 N·s·m−1 for BP and SJ, respectively. Upper and lower limb F0 and Pmax were significantly related. P1500 was significantly (P

This study aimed to evaluate the within- and between-session reliability of force, velocity and power performances and to assess the force-velocity relationship during the deadlift high pull (DHP). Nine participants performed two identical sessions of DHP with loads ranging from 30 to 70% of body mass. The force was measured by a force plate under the participants' feet. The velocity of the 'body + lifted mass' system was calculated by integrating the acceleration and the power was calculated as the product of force and velocity. The force-velocity relationships were obtained from linear regression of both mean and peak values of force and velocity. The within- and between-session reliability was evaluated by using coefficients of variation (CV) and intraclass correlation coefficients (ICC). Results showed that DHP force-velocity relationships were significantly linear (

Muscle fascicles–tendon interactions are the main determinant in production of high joint velocity. Currently, no study has investigated the muscle fascicles behaviour of knee extensor muscles until the highest reachable velocity (e.g., unloaded knee extension). We aimed to track the changes in vastus lateralis fascicles length during knee extensions to quantify muscle fascicles and tendinous tissues contributions to muscle–tendon unit shortening and to determine maximal muscle fascicles shortening velocity. Fifteen participants performed isokinetic and isoinertial knee extensions, and ultrafast ultrasound imaging was used to observe the vastus lateralis fascicles from low to very high joint velocity. The muscle fascicles shortening velocity increased linearly with the increase in knee joint velocity up to the maximal joint velocity (mean R 2 = 0.93 ± 0.08). Muscle fascicles contribution to muscle–tendon unit shortening velocity was almost constant regardless of the condition (83 ± 23%). Using Hill’s equation, the maximal velocity of knee joint and muscle fascicles was determined at 1000 ± 489°s−1 and 5.1 ± 2.0 L0 s−1 (47.4 ± 18.7 cm s−1), respectively. Contribution of muscle fascicles to the muscle–tendon unit shortening velocity was much higher for the vastus lateralis in this study compared to the gastrocnemius medialis in two previous studies. Moreover, this contribution of muscle fascicles shortening velocity was constant whatever the velocity condition, even at the highest reachable velocity. Thus, the vastus lateralis fascicles shortening velocity increases linearly with the knee joint velocity until high velocities and its behaviour strongly accorded with the classical Hill’s force–velocity relationship.

International audience; This study investigated the effects of active and/or passive warm-up tasks on the hamstring muscles stiffness through elastography and passive torque measurements. On separate occasions, fourteen males randomly completed four warm-up protocols comprising Control, Cycling, Foam rolling, or Cycling plus Foam rolling (Mixed). The stiffness of the hamstring muscles was assessed through shear wave elastography, along with the passive torque-angle relationship and maximal range of motion (ROM) before, 5, and 30 minutes after each experimental condition. At 5 minutes, Cycling and Mixed decreased shear modulus (−10.3% ± 5.9% and −7.7% ± 8.4%, respectively; P≤.0003, effect size [ES]≥0.24) and passive torque (−7.17% ± 8.6% and −6.2% ± 7.5%, respectively; P≤.051, ES≥0.28), and increased ROM (+2.9% ± 2.9% and +3.2% ± 3.5%, respectively; P≤.001, ES≥0.30); 30 minutes following Mixed, shear modulus (P=.001, ES=0.21) and passive torque (P≤.068, ES≥0.2) were still slightly decreased, while ROM increased (P=.046, ES=0.24). Foam rolling induced “small” immediate short-term decreases in shear modulus (−5.4% ± 5.7% at 5 minutes; P=.05, ES=0.21), without meaningful changes in passive torque or ROM at any time point (P≥.12, ES≤0.23). These results suggest that the combined warm-up elicited no acute superior effects on muscle stiffness compared with cycling, providing evidence for the key role of active warm-up to reduce muscle stiffness. The time between warm-up and competition should be considered when optimizing the effects on muscle stiffness.

Eccentric training is a mechanical loading classically used in clinical environment to rehabilitate patients with tendinopathies. In this context, eccentric training is supposed to alter tendon mechanical properties but interaction with the other components of the muscle-tendon complex remains unclear. The aim of this study was to determine the specific effects of 14 wk of eccentric training on muscle and tendon mechanical properties assessed in active and passive conditions in vivo. Twenty-four subjects were randomly divided into a trained group ( n = 11) and a control group ( n = 13). Stiffness of the active and passive parts of the series elastic component of plantar flexors were determined using a fast stretch during submaximal isometric contraction, Achilles tendon stiffness and dissipative properties were assessed during isometric plantar flexion, and passive stiffness of gastrocnemii muscles and Achilles tendon were determined using ultrasonography while ankle joint was passively moved. A significant decrease in the active part of the series elastic component stiffness was found ( P < 0.05). In contrast, a significant increase in Achilles tendon stiffness determined under passive conditions was observed ( P < 0.05). No significant change in triceps surae muscles and Achilles tendon geometrical parameters was shown ( P > 0.05). Specific changes in muscle and tendon involved in plantar flexion are mainly due to changes in intrinsic mechanical properties of muscle and tendon tissues. Specific assessment of both Achilles tendon and plantar flexor muscles allowed a better understanding of the functional behavior of the muscle-tendon complex and its adaptation to eccentric training.

International audience; BackgroundThe sit-to-stand movement requires balance control and coordination between the trunk and lower limbs. For these reasons, it is commonly used in clinics for evaluating lower limb muscle function in the elderly. The aim of the present study was to point out re levant biomechanical and neurophysiological sit-to-stand parameters allowing comparison between elderly fallers and non-fallers.MethodsTen elderly fallers and thirty non-fallers performed sit-to-stand movements. Sit-to-stand mechanical (maximal and mean force, impulse) and temporal parameters were measured in the vertical and anteroposterior axes using force platforms. Activity of rectus femoris, vastus lateralis, and gastrocnemius lateralis muscles was bilaterally recorded by surface electromyography.ResultsTime to realize sit-to-stand movements was significantly longer in elderly fallers compared to non-fallers (p < 0.05). In the same way, maximal vertical force and mean posterior force applied on force platform were significantly lower (p < 0.05) in fallers than in non-fallers individual. At muscular activity level, results showed a main statistical difference in gastrocnemius lateralis muscle activity patterns between faller and non-faller groups.ConclusionVertical and anteroposterior data from force platform, and gastrocnemius lateralis muscle activity determined during sit-to-stand movement are the most relevant parameters to differentiate fallers and non-fallers. Moreover, these factors highlight different strategies to rise from a chair between faller and non-faller group, suggesting that fallers would constantly adjust their control balance during the sit-to-stand movement.

International audience; Background: some centenarians are engaged in regular physical activity and sometimes in sporting events.Objective: we aimed to identify world records of centenarian athletes in several sports and determine which represented the best performance when compared to all-age world records, all disciplines taken together.Methods: all of the best performances achieved by centenarians were identified and compared in three disciplines: athletics, swimming and cycling. The performances were considered as an average of the respective speeds, except for jumping and throwing events for which the maximum distances performed were considered. Within each discipline, the decline in performance of centenarian athletes was expressed as a percentage of the world record for that discipline. In total, 60 performances of centenarian athletes were found. These performances belong to 19 individuals: 10 in athletics, 8 in swimming and 1 in cycling.Results: the centenarian world record performed by Robert Marchand in one hour track cycling appears to be the best performance (-50.6% compared with the all-age world record in this discipline) achieved by a centenarian.Conclusions: although the physiological characteristics of Robert Marchand are certainly exceptional, his remarkable performance could also be due to the lower age-related decline for cycling performances compared with running and swimming. Our observations offer new perspectives on how the human body can resist the deleterious effects of ageing.

International audience; 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. Voluntary eccentric torque progressively decreased (up to −36%) concomitantly to a significant alteration of evoked torque (up to −34%) and voluntary activation (up to −13%) during the exercise. Voluntary isometric torque (−48 ± 7%), evoked torque (−41 ± 14%) and voluntary activation (−13 ± 11%) decreased at POST, but only voluntary isometric torque (−19 ± 6%) and evoked torque (−10 ± 18%) remained depressed at 48 h. Neither changes in voluntary activation nor evoked torque during the exercise were related to the magnitude of muscle damage markers, but the evoked torque decrement at 48 h was significantly correlated with the changes in voluntary activation (r = −0.71) and evoked torque (r = 0.77) at POST. Our findings show that neuromuscular responses observed during eccentric contractions were not associated with muscle damage. Conversely, central and peripheral impairments observed immediately after the exercise reflect the long-lasting reduction in force-generating capacity.

International audience; It is known that anxiety (ANX) impairs action–perception coupling. This study tests whether this impairment could be associated with an alteration of the sensorimotor function. To this aim, the cortical activities underlying the sensorimotor function were recorded in twelve volunteers in a reach-to-grasp paradigm, in which the level of ANX and the position of a glass were manipulated. The experimental manipulation of the ANX-related somatosensory state was expected to prompt participants to underestimate their reaching-to-grasp capabilities while the sensorimotor-related oscillatory brain activities around the 6-Hz (θ) frequency over motor-related and parietal regions were expected to be modulated. We also investigated the oscillatory brain dynamics around the 11.5-Hz (fast-α) frequency as a neural hallmark of ANX manipulation induced by the breath-restriction. Results indeed showed that participants underestimated their reaching-to-grasp maximal performance. Concomittantly, θ-EEG synchronization over the motor cortex contralateral to the dominant hand was higher during glass presentation under breath-restriction condition (+20.1%; p < 0.05), and when the glass was perceived as non-reachable (+20.0%; p < 0.05). Fast-α-EEG desynchronization was reduced under breath-restriction (−37.7%; p < 0.05). The results confirm that ANX-related impairment of action–perception coupling co-modulates with theta-sensorimotor rhythm. This finding is discussed as an altered “readiness state” in the reaching-related cortical network, while individuals are anxious.

International audience; Aging is frequently associated with a decreased postural stability, essentially after 60 years, leading to an increased risk of falling. In this article we propose to highlight the influence of the aging of the neuromuscular system on postural stability when standing upright. To maintain balance while standing upright, human needs to control the activity of ankle muscles and particularly the plantar flexors. During the aging process, the performance of these muscles are strongly altered. It is commonly observed large deficits in elderly people with history of falls. Some authors reported an inverse correlation between the amplitude of postural sway and the capacity of force production of ankle muscles suggesting that the assessment of neuromuscular function could be an index of postural stability or even of the falling risk. Finally, enhance the strength of ankle muscles in elderly through physical exercise could be an adequate intervention to improve postural stability and reduce the incidence of falls.

The aim of the present study was to compare the effects of ankle muscle fatigue on postural control when plantarflexors (PFs) and dorsiflexors (DFs) are fatigued simultaneously compared with separately. This study also investigated the recovery of postural control after fatigue. Sixteen adults (eight women and eight men) performed postural trials before and after an isokinetic fatigue task involving either (i) only PFs (308 s 1 ), (ii) only DFs (1208 s 1 ), or (iii) both PFs and DFs simultaneously. The fatigue task involved maximal contractions repeated until the torque produced decreased below 50% of the maximal torque. Postural trials lasted 30 s and were performed on one leg with eyes open (EO) or eyes closed (EC). Sway area, medio-lateral (ML) and antero-posterior (AP) positions and velocities were calculated from the center of pressure displacements. With EO, no effect of fatigue was found on postural variables. With EC, sway area and AP velocity increased only when both PFs and DFs were fatigued simultaneously. An effect of fatigue present only when both muscle groups are fatigued simultaneously could be due to impairment in the compensatory activity between agonist and antagonist muscles and/or a greater decrease in proprioception due to a greater number of fatigued muscles. In addition, when PFs and DFs were fatigued simultaneously, sway area and AP velocity returned to pre-fatigue values within 2 min, whereas a posterior shift in AP position persisted for 10 min. This last result may suggest a longer-lasting change in postural strategy needed for optimal postural control.

The aims of this study were to determine the effects of plyometric training on both active and passive parts of the series elastic component (SEC) stiffness, and on geometrical parameters [i.e., muscle architecture, muscle and tendon cross-sectional area (CSA)] of the plantarflexors muscle-tendon complex to assess possible specific adaptations of the elastic properties. Nineteen subjects were randomly divided into a trained group and a control group. Active and passive components of the SEC stiffness were determined using a fast stretch during submaximal voluntary isometric plantarflexor activity. Geometrical parameters of the triceps surae muscles and the Achilles tendon were determined using ultrasonography. A significant increase in the passive component of the SEC stiffness was found (p0.05). In contrast, a significant decrease in the active part of the SEC stiffness was observed (p0.05). No significant changes in plantarflexor muscles CSA, architecture and Achilles tendon CSA were seen (p0.05). Thus, plyometric training led to specific adaptations within each part of the SEC. Theses adaptations could increase both the efficiency of the energy storage-recoil process and muscular tension transmission leading to an increase in jump performances.

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. The intersubject variability of EMG and mechanical patterns was assessed using standard deviation, mean deviation, variance ratio and coefficient of cross-correlation (\( \overline {R_{0} } , \) with lag time = 0). The results demonstrated a high intersubject variability of EMG patterns at both exercise intensities for biarticular muscles as a whole (and especially for Gastrocnemius lateralis and Rectus femoris) and for one monoarticular muscle (Tibialis anterior). However, this heterogeneity of EMG patterns is not accompanied by a so high intersubject variability in pedal force application patterns. A very low variability in the three mechanical profiles (effective force, total force and index of mechanical effectiveness) was obtained in the propulsive downstroke phase, although a greater variability in these mechanical patterns was found during upstroke and around the top dead center, and at 250 W when compared to 150 W. Overall, these results provide additional evidence for redundancy in the neuromuscular system.

Sit-to-stand (STS) movement is useful for evaluating lower limb muscle function, especially from force platforms. Nevertheless, due to a lack of standardization of the STS movement (e.g., position, subject’s instructions, etc.), it is difficult to compare results obtained in previous studies. The aim of the present study was to determine the most relevant condition, parameters, and number of trial to perform STS movements. In this study, STS mechanical (maximal and mean force, impulse) and temporal parameters were measured in the vertical, medio-lateral and antero-posterior axes using a force platform. Five STS conditions (i.e., with or without armrests, variation of the height of the chair and the movement speed) were analyzed to evaluate repeatability of different standardized procedures. Most of the mechanical and temporal parameters were influenced by the STS condition (p

The alpha method enables the dissociation of the passive (i.e., tendinous tissues) and active (i.e., fascicles) part of muscle–tendon stiffness. It is based on two main assumptions (i.e., a constant tendon stiffness and a muscle stiffness proportional to the torque produced), which have not been approved in vivo. The purpose of this study was to validate these two assumptions using ultrafast ultrasound, and to compare fascicle and tendon stiffness as determined by both methods. Ten healthy males performed a fast-stretch experiment on the ankle plantar flexors. The mathematical model of the alpha method allowed to estimate the stiffness of muscle and tendinous tissues on the basis of the assumptions associated to the behaviors of muscle fascicles and tendinous tissues. Muscle and tendon stiffness of the gastrocnemius medialis were also calculated from ultrafast ultrasound measurements. Muscle stiffness measured by the ultrasound method increased from 217 ± 83 to 720 ± 265 N/mm with an increasing level of force (from 30 to 90 % MVC). Tendinous stiffness measured by the ultrasound method remained constant across the force level (P

International audience; Durand, S, Ripamonti, M, Rahmani, A, and Beaune, B. Bioenergetical and cardiac adaptations of pilots to a 24-hour team kart race. J Strength Cond Res 29(11): 3234-3239, 2015-This study aimed to evaluate energy expenditure (EE) and heart rate (HR) response in kart pilots to successive driving bouts during a 24-hour team race. Eight adult male pilots (22.8 6 4.1 years) participated to a team 24-hour speedway kart race in Le Mans (France). They alternatively piloted a 390 cm 3 kart. Each relay was 45 minutes long and each pilot performed 4 relays. For each pilot, mean speeds were calculated from lap-to-lap duration recordings using a telemetric infrared timing device. Heart rate values were recorded continuously on 5-second intervals using a portable cardiometric device. Total energy expenditure (EET) and physical activity ratio (PAR) were determined by accelerometry. To pilot a kart during 45 minutes at a mean speed around 62 km$h 21 induces a 300-kcal EET, corresponding to a 5.6-Mets PAR. This effort is responsive for a 73 b$min 21 increase in HR, from 84.1 6 7.6 to 157.4 6 11.0 b$min 21 (82% maximal heart rate intensity). However, during this relay period, HR values seemed independent to mean speed performance and bioenergetical values. Thus, in the context of the 24-hour team race, the variability in effort made during each relay and relay succession did not alter bioener-getical adaptation of pilots to kart driving. The high EE and HR values would be better explained by both emotional stress and environmental constraints such as speedway configuration and vibrations. The way how these factors specifically influence bioenergetical demand, and their relative importance, has to be specified to optimize training procedure and recommendations .

Interindividual variability in performance of fast movements is commonly explained by a difference in maximal muscle-shortening velocity due to differences in the proportion of fast-twitch fibers. To provide a better understanding of the capacity to generate fast motion, this study aimed to 1) measure for the first time in vivo the maximal fascicle-shortening velocity of human muscle; 2) evaluate the relationship between angular velocity and fascicle-shortening velocity from low to maximal angular velocities; and 3) investigate the influence of musculo-articular features (moment arm, tendinous tissues stiffness, and muscle architecture) on maximal angular velocity. Ultrafast ultrasound images of the gastrocnemius medialis were obtained from 31 participants during maximal isokinetic and light-loaded plantar flexions. A strong linear relationship between fascicle-shortening velocity and angular velocity was reported for all subjects (mean R2 = 0.97). The maximal shortening velocity (VFmax) obtained during the no-load condition (NLc) ranged between 18.8 and 43.3 cm/s. VFmax values were very close to those of the maximal shortening velocity (Vmax), which was extrapolated from the F-V curve (the Hill model). Angular velocity reached during the NLc was significantly correlated with this VFmax ( r = 0.57; P < 0.001). This finding was in agreement with assumptions about the role of muscle fiber type, whereas interindividual comparisons clearly support the fact that other parameters may also contribute to performance during fast movements. Nevertheless, none of the biomechanical features considered in the present study were found to be directly related to the highest angular velocity, highlighting the complexity of the upstream mechanics that lead to maximal-velocity muscle contraction.

International audience; Motor learning studies have for a long time focused on performance variables (in terms of speed or accuracy) in assessing learning, transfer and retention of motor skills. We argue, however, that learning essentially resides in changes in coordination variables (in terms of qualitative organization of behavior) and that relevant tests for assessing the effectiveness of learning and retention should consider these variables. The aim of this experiment was to test the retention of a complex motor skill, after a long-term delay. Ten years ago, five participants were involved in an experiment during which they practiced for 39 sessions of ten 1-min trials on a ski-simulator. All participants volunteered for a retention test, ten years after, for one session of ten 1-min trials. Analyses focused on the oscillations of the platform of the simulator. Performance was assessed in terms of amplitude and frequency. Coordination was accounted for by an analysis of dynamical properties of the motion of the platform, and especially the nature of the damping function that was exploited for sustaining the limit cycle dynamics. Results showed a significant decrement in performance variables. In contrast, all participants adopted from the first trialonwards the coordination mode they learned 10 years ago. These results confirm the strong persistence of coordination modes, once acquired and stabilized in the behavioral repertoire. They also support the importance of coordination variables for a valid assessment of learning and retention.

CCC:000355836600018; International audience; Objective: In contrast to conventional (CONV) neuromuscular electrical stimulation (NMES), the use of "wide-pulse, high-frequencies" (WPHF) can generate higher forces than expected by the direct activation of motor axons alone. We aimed at investigating the occurrence, magnitude, variability and underlying neuromuscular mechanisms of these "Extra Forces" (EF). Methods: Electrically-evoked isometric plantar flexion force was recorded in 42 healthy subjects. Additionally, twitch potentiation, H-reflex and M-wave responses were assessed in 13 participants. CONV (25 Hz, 0.05 ms) and WPHF (100 Hz, 1 ms) NMES consisted of five stimulation trains (20 s on-90 s off). Results: K-means clustering analysis disclosed a responder rate of almost 60%. Within this group of responders, force significantly increased from 4% to 16% of the maximal voluntary contraction force and H-reflexes were depressed after WPHF NMES. In contrast, non-responders showed neither EF nor H-reflex depression. Twitch potentiation and resting EMG data were similar between groups. Interestingly, a large inter-and intrasubject variability of EF was observed. Conclusion: The responder percentage was overestimated in previous studies. Significance: This study proposes a novel methodological framework for unraveling the neurophysiological mechanisms involved in EF and provides further evidence for a central contribution to EF in responders. (C) 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

The study examined the fatigue effect on tennis performance and upper limb muscle activity. Ten players were tested before and after a strenuous tennis exercise. Velocity and accuracy of serve and forehand drives, as well as corresponding surface electromyographic (EMG) activity of eight upper limb muscles were measured. EMG and force were also evaluated during isometric maximal voluntary contractions (IMVC). Significant decreases were observed after exercise in serve accuracy (-11.7%) and velocity (-4.5%), forehand accuracy (-25.6%) and consistency (-15.6%), as well as pectoralis major (PM) and flexor carpi radialis (FCR) IMVC strength (-13.0% and -8.2%, respectively). EMG amplitude decreased for PM and FCR in serve, forehand and IMVC, and for extensor carpi radialis in forehand. No modification was observed in EMG activation timing during strokes or in EMG frequency content during IMVC. Several hypotheses can be put forward to explain these results. First, muscle fatigue may induce a reduction in activation level of PM and forearm muscles, which could decrease performance. Second, conscious or subconscious strategies could lead to a redistribution of muscle activity to non-fatigued muscles in order to protect the organism and/or limit performance losses. Otherwise, the modifications of EMG activity could also illustrate the strategies adopted to manage the speed-accuracy trade-off in such a complex task.

International audience; OBJECTIVES: Endothelial function can be assessed by acetylcholine (ACh) iontophoresis with single current application. The effect of inter-electrode distance as well as electrical cutaneous resistance (ECR) on ACh dependent vasodilation has never been studied using single current application. The aims of this study are (i) to compare ACh-peak and ECR measured at different inter-electrode distances, (ii) to assess the relationship between ACh-peak and ECR, (iii) and to study the reproducibility of the ECR values. METHODS: Fourteen healthy subjects were included. Using laser speckle contrast imaging, ACh-iontophoreses (0.1 mA, 30s) were performed on the forearm at a 7-day interval with an inter-electrode distance set at 5 cm. Two other inter-electrode distances were also evaluated: 10 cm and 15 cm. ECR was measured during each ACh-iontophoresis as well as the ACh-peak. RESULTS: No statistical difference was found between the ACh-peak values obtained at 5 cm, 10 cm and 15 cm. ECRs were also not statistically different. An inverse relationship (r=-0.60) was found between the ACh-peak and ECR (p\textless0.05). The coefficient of variation of the inter-day reproducibility of the ECR values was 9.1% [6.5%-15.1%] with an intra-class-correlation coefficient of 0.93 [0.81-0.98]. CONCLUSION: Inter-electrode distance ranging from 5 cm to 15 cm changes neither the ACh-peak value nor the ECR value. ECR impacts ACh-peak values.

International audience; Aim: Changes in muscle stiffness after exercise-induced muscle damage have been classically inferred from passive torque–angle curves. Elasto-graphic techniques can be used to estimate the shear modulus of a localized muscular area. This study aimed to quantify the changes in shear elastic modulus in different regions of the elbow flexors after eccentric exercise and their relation to muscle length. Methods: Shear elastic modulus and transverse relaxation time (T 2) were measured in the biceps brachii and brachialis muscles of sixteen participants , before, 1 h, 48 h and 21 days after three sets of ten maximal isoki-netic eccentric contractions performed at 120° s À1. Results: The shear elastic modulus of the elbow flexors significantly increased 1 h (+46%; P = 0.005), with no significant change at 48 h and 21D, post-exercise. In contrast, T 2 was not modified at 1 h but significantly increased at 48 h (+15%; P < 0.05). The increase in shear elastic modulus was more pronounced at long muscle lengths and reached a similar extent in the different regions of the elbow flexors. The normalized hysteresis area of shear elastic modulus–length relationship for the biceps brachii increased 1 h post-exercise (31%) in comparison with the pre-exercise value (18%), but was not significantly altered after five stretching cycles (P = 0.63). Conclusion: Our results show homogeneous changes in muscle shear elastic modulus within and between elbow flexors. The greater increase in shear elastic modulus observed at long muscle lengths suggests the putative involvement of both cross-bridges number and titin in the modifications of muscle shear elastic modulus after damaging exercise.

The dual-task paradigm has previously been used to investigate the attentional demands associated with postural control. Previous studies have identified both the focus of attention and the difficulty of a postural task as potential factors influencing dual-task performance. The aim of this study was to examine how the instructed focus of attention influences dual-task performance during quiet standing tasks of various levels of difficulty. Thirteen young adults participated in two testing sessions consisting of standing as still as possible on a force platform in different postural conditions, while simultaneously performing a simple reaction time (RT) task. Postural task difficulty was manipulated by various combinations of three bases of support (feet together, tandem and single leg) and two visual conditions (eyes opened and closed). Participants were instructed to focus on either their balance or their RT performance, depending on the testing session. When comparing postural control with respect to session focus, anterior-posterior sway velocity decreased with the addition of the simple RT task when the focus was on balance, but only during the more difficult dual-task conditions. In contrast, sway area and medial-lateral sway velocity did not change between the two instructed focus sessions. Participants responded faster in all dual-task conditions when focusing on RT performance than on balance. The modified attention allocation index indicated that participants' ability to modulate their allocation of attentional resources to respond positively to instruction was more pronounced in the most challenging postural condition. The present findings could have important implications for the interpretation of dual-task performance in both clinical and research settings.

The aim of the present study was to investigate changes in joint angles and limb positions accompanying postural control impairments induced by fatigue of the ankle plantarflexor muscles and vision removal. Thirteen subjects performed unipedal standing tasks with and without vision before and after isometric fatigue of the plantarflexor muscles. Results indicated that to compensate for the negative effects of fatigue and vision removal on postural control, participants increased flexion at the ankle, knee and back while the free lower limb and the pelvis moved backward and the upper limbs forward. These strategies could be performed to increase the role of non-fatigued muscles and optimize the use of all the joints implicated in unipedal standing.

The purpose of this study was to investigate the changes in postural control and in posture induced by ankle plantarflexor fatigue during a unipedal stance task. We also studied the postural strategies in the antero-posterior and medio-lateral planes used by participants to maintain balance. Thirteen young adults were asked to stand barefoot on their preferred leg as still as possible for 30s with vision or without vision. Participants performed postural trials before and after a fatigue protocol that consisted of standing on toes until exhaustion. Centre of pressure (COP) displacements were measured with a force platform and electrogoniometers were placed at the ankle, knee and hip joints of the support leg to monitor articular angles. Relationships between changes in articular angles and displacements of the COP in the antero-posterior and medio-lateral planes were tested using cross-correlations. Sway area and velocity increased with fatigue, but only without vision. A posterior shift of the mean COP position was also observed after fatigue. Ankle and hip joints were more flexed after fatigue. Moderate to good relationships between COP displacements and ankle angles were observed before and after fatigue in both planes whereas these relationships were low for hip and knee joints. Ankle plantarflexors fatigue induced impairment in postural control and changes in posture. To compensate for the effects of fatigue, participants increased the flexion of the ankle and/or the hip joints but conserved the ankle strategy as the dominant postural strategy in both planes.

Cardiovascular diseases are often revealed during exercise and are associated with cutaneous blood flow (CBF) dysfunction. Studies of CBF during exercise are consequently of interest. Laser speckle contrast imaging (LSCI) allows for non-contact and real-time recording of CBF at rest. We tested whether LSCI could allow the study of CBF during a cycling exercise using a specific signal treatment procedure that removes movement-induced arte- facts from the LSCI raw signal. We recorded the baseline CBF and peak post-occlusive reactive hyperaemia (PORH) from the cutaneous forearm using LSCI and the mean blood pressure before and during cycling (80 Wat 70 rpm) in nine healthy subjects. We determined the cross-correlation coef- ficient r between LSCI traces obtained before and during cycling and before and after a specifically designed signal processing technique. The results are presented as the me- dian (25th-75th centile) and expressed as the cutaneous vascular conductance (laser speckle perfusion units (LSPU) per millimetre of mercury). Cross-correlation r in- creased from 0.226±0.140 before to 0.683±0.170 after post-processing. After signal processing, the peak PORH during exercise was reduced (0.38 (0.30-0.52) LSPU/mmHg) compared with the peak PORH during the non-exercise phase (0.69 (0.63-0.74) LSPU/mmHg, p

The purpose of this study was to investigate the influence of fatiguing exercise intensity on the nature and extent of fatigue-induced changes in neuromuscular function and postural stability in quiet standing. We also explored the contribution of selected neuromuscular mechanisms involved in force production to postural stability impairment observed following fatigue using an approach based on multivariate regressions. Eighteen young subjects performed 30-s postural trials on one leg with their eyes closed. Postural trials were performed before and after fatiguing exercises of different intensities: 25, 50 and 75% of maximal isometric plantarflexor torque. Fatiguing exercises consisted of sustaining a plantarflexor isometric contraction at the target intensity until task failure. Maximal isometric plantarflexor torque, electromyographic activity of plantarflexor and dorsiflexor muscles, activation level (twitch interpolation technique) and twitch contractile properties of plantarflexors were used to characterize neuromuscular function. The 25% exercise was associated with greater central fatigue whereas the 50 and 75% exercises involved mostly peripheral fatigue. However, all fatiguing exercises induced similar alterations in postural stability, which was unexpected considering previous literature. Stepwise multiple regression analyses showed that fatigue-related changes in selected parameters related to neuromuscular function could explain more than half (0.51≤R(2)≤0.82) of the changes in postural variables for the 25% exercise. On the other hand, regression models were less predictive (0.17≤R(2)≤0.73) for the 50 and 75% exercises. This study suggests that fatiguing exercise intensity does not influence the extent of postural stability impairment, but does influence the type of fatigue induced and the neuromuscular function predictors explaining changes in postural variables.

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. Study Design: Controlled laboratory study. Methods: A total of 24 participants were included in either a control group (CONT) or a cryotherapy group (CRYO). Immediately after 3 sets of 20 maximal isokinetic eccentric contractions of elbow flexors, and then 1, 2, and 3 days after exercise, the CRYO group received a cryotherapy treatment (3 × 4 minutes at −30°C separated by 1 minute). The day before and 1, 2, 3, 7, and 14 days after exercise, several parameters were quantified: maximal isometric torque and its associated maximal electromyographic activity recorded by a 64-channel electrode, delayed-onset muscle soreness (DOMS), biceps brachii transverse relaxation time (T2) measured using magnetic resonance imaging, creatine kinase activity, interleukin-6, and C-reactive protein. Results: Maximal isometric torque decreased similarly for the CONT (–33% ± 4%) and CRYO groups (−31% ± 6%). No intergroup differences were found for DOMS, electromyographic activity, creatine kinase activity, and T2 level averaged across the whole biceps brachii. C-reactive protein significantly increased for CONT (+93% at 72 hours, P < .05) but not for CRYO. Spatial analysis showed that cryotherapy delayed the significant increase of T2 and the decrease of electromyographic activity level for CRYO compared with CONT (between day 1 and day 3) in the medio-distal part of the biceps brachii. Conclusion: Although some indicators of muscle damage after severe eccentric exercise were delayed (ie, local formation of edema and decrease of muscle activity) by repeated air-pulsed cryotherapy, we provide evidence that this cooling procedure failed to improve long-term recovery of muscle performance. Clinical Relevance: Four applications of air-pulsed cryotherapy in the 3 days after a strenuous eccentric exercise are ineffective overall in promoting long-term muscle recovery. Further studies taking into account the amount of exercise-induced muscle damage would allow investigators to make stronger conclusions regarding the inefficiency of this recovery modality.

International audience; PURPOSE: To evaluate spring-mass (SM) behavior and associated electromyographic (EMG) activity during a run to exhaustion following a cycle exercise in trained triathletes. METHODS: Ten triathletes completed four tests: a cycling test to determine V˙O(2max); a running test to determine the lactate threshold (LT); a 5 min control run at LT (C-Run) followed after a total recovery period by a cycle-to-run session to exhaustion [30 min of cycling at ∼80% V˙O(2max) followed by a run until exhaustion at LT (T-Run)]. SM behavior and EMG signals in nine lower limb muscles were recorded throughout the running sessions. RESULTS: Immediately after cycling, leg stiffness was 12.1% higher than its C-Run value and a concomitant increase of EMG activity of knee extensors was observed during pre-contact. Throughout T-Run, leg stiffness decreased by 7.3%, while knee extensors and ankle flexors activities decreased during pre-contact and braking phases. No significant variations in SM parameters and no significant increase of muscle activity were reported between C-Run and the end of T-Run. CONCLUSION: SM behavior during the cycle-run test was consistent with EMG activity changes. Cessation of exercise was not associated with significant alterations of stiffness values and EMG activity.