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FOURE Alexandre

Postdoctoral position
tel : +33 4 91 38 48 07
Key Words
- Skeletal muscle, magnetic resonance imaging (MRI), muscle volume, T2 mapping, diffusion tensor imaging (DTI), 31P magnetic resonance spectroscopy (MRS), muscle damage, soreness, branched chain amino acids (BCAA), quadriceps femoris, humans, tendon, stiffness, ankle joint range of motion, ultrasonography, muscle architecture, triceps surae.

Current Research Interest and projects

I currently developped protocols to assess musculo-articular alterations with a whole body 7T-MRI scanner. In order to assess early changes in tissue properties associated to pathologies such as muscular dystrophy, tendinopathies, ostraoarthritis and ostreoporosis, developpments of proton and sodium MRI sequences are currently in progress to explore muscle, tendon, cartilage and bone.

My recent project aimed at determining the effects of branched chain amino acids supplementation on neurmuscular, functional, anatomic and metabolic alterations induced by a single bout of electrically evoked isometric contractions of knee extensors. Using percutaneous electrical stimulation and magnetic resonance techniques (i.e., T2 mapping, diffusion tensor imaging and 31P-MRS), I assessed the central and peripheral contribution in decreased neuromuscular function efficiency, I determined the localization and the extent of muscle damage among and into the four muscles of the quadriceps femoris and I characterized changes in muscle metabolism at rest, during a submaximal voluntary exercise and recovery.

My previous researches focused on the characterization of specific muscle and tendon mechanical properties (i.e. stiffness, dissipative properties) non-invasively in vivo. Combined measurement techniques including dynamometry, surface electromyography and ultrasonographic imaging were used to determine triceps surae muscle and tendon behavior during isometric muscle contraction and passive motion of the ankle in dorsiflexion. In addition, the effects of plyometric and eccentric training on mechanical and geometrical properties of both muscular and tendinous structure in active and passive conditions were assessed.



Journal Article

  • Fouré, A, Ogier, AC, Le Troter, A, Vilmen, C, Feiweier, T, Guye, M, Gondin, J, Besson, P & Bendahan, D 2018, “Diffusion Properties and 3D Architecture of Human Lower Leg Muscles Assessed with Ultra-High-Field-Strength Diffusion-Tensor MR Imaging and Tractography: Reproducibility and Sensitivity to Sex Difference and Intramuscular Variability”, Radiology, vol. 287, no. 2, p. 592-607.
    Résumé : Purpose To demonstrate the reproducibility of the diffusion properties and three-dimensional structural organization measurements of the lower leg muscles by using diffusion-tensor imaging (DTI) assessed with ultra-high-field-strength (7.0-T) magnetic resonance (MR) imaging and tractography of skeletal muscle fibers. On the basis of robust statistical mapping analyses, this study also aimed at determining the sensitivity of the measurements to sex difference and intramuscular variability. Materials and Methods All examinations were performed with ethical review board approval; written informed consent was obtained from all volunteers. Reproducibility of diffusion tensor indexes assessment including eigenvalues, mean diffusivity, and fractional anisotropy (FA) as well as muscle volume and architecture (ie, fiber length and pennation angle) were characterized in lower leg muscles (n = 8). Intramuscular variability and sex differences were characterized in young healthy men and women (n = 10 in each group). Student t test, statistical parametric mapping, correlation coefficients (Spearman rho and Pearson product-moment) and coefficient of variation (CV) were used for statistical data analysis. Results High reproducibility of measurements (mean CV ± standard deviation, 4.6% ± 3.8) was determined in diffusion properties and architectural parameters. Significant sex differences were detected in FA (4.2% in women for the entire lower leg; P = .001) and muscle volume (21.7% in men for the entire lower leg; P = .008), whereas architecture parameters were almost identical across sex. Additional differences were found independently of sex in diffusion properties and architecture along several muscles of the lower leg. Conclusion The high-spatial-resolution DTI assessed with 7.0-T MR imaging allows a reproducible assessment of structural organization of superficial and deep muscles, giving indirect information on muscle function. ©RSNA, 2018 Online supplemental material is available for this article.
    Mots-clés : crmbm, msk.

  • Gineste, C & Fouré, A 2018, “Heterogeneity of energy metabolism within the tibialis anterior. Is it just an outcome of a specific muscle activation, architecture and composition?”, The Journal of Physiology.


Journal Article

  • Chatel, B, Hourdé, C, Gondin, J, Fouré, A, Le Fur, Y, Vilmen, C, Bernard, M, Messonnier, LA & Bendahan, D 2017, “Impaired muscle force production and higher fatigability in a mouse model of sickle cell disease”, Blood Cells, Molecules & Diseases, vol. 63, p. 37-44.
    Résumé : Skeletal muscle function has been scarcely investigated in sickle cell disease (SCD) so that the corresponding impact of sickle hemoglobin is still a matter of debate. The purpose of this study was to investigate muscle force production and fatigability in SCD and to identify whether exercise intensity could have a modulatory effect. Ten homozygous sickle cell (HbSS), ten control (HbAA) and ten heterozygous (HbAS) mice were submitted to two stimulation protocols (moderate and intense) to assess force production and fatigability. We showed that specific maximal tetanic force was lower in HbSS mice as compared to other groups. At the onset of the stimulation period, peak force was reduced in HbSS and HbAS mice as compared to HbAA mice. Contrary to the moderate protocol, the intense stimulation protocol was associated with a larger decrease in peak force and rate of force development in HbSS mice as compared to HbAA and HbAS mice. These findings provide in vivo evidence of impaired muscle force production and resistance to fatigue in SCD. These changes are independent of muscle mass. Moreover, SCD is associated with muscle fatigability when exercise intensity is high.
    Mots-clés : crmbm, Exercise intensity, msk, Muscle mass, Muscle volume, Rate of force development.

  • Fatehi, F, Salort-Campana, E, Le Troter, A, Lareau-Trudel, E, Bydder, M, Fouré, A, Guye, M, Bendahan, D & Attarian, S 2017, “Long-term follow-up of MRI changes in thigh muscles of patients with Facioscapulohumeral dystrophy: A quantitative study”, PloS One, vol. 12, no. 8, p. e0183825.
    Résumé : Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common hereditary muscular disorders. Currently FSHD has no known effective treatment and detailed data on the natural history are lacking. Determination of the efficacy of a given therapeutic approach might be difficult in FSHD given the slow and highly variable disease progression. Magnetic resonance imaging (MRI) has been widely used to qualitatively and quantitatively evaluate in vivo the muscle alterations in various neuromuscular disorders. The main aim of the present study was to investigate longitudinally the time-dependent changes occurring in thigh muscles of FSHD patients using quantitative MRI and to assess the potential relationships with the clinical findings. Thirty-five FSHD1 patients (17 females) were enrolled. Clinical assessment tools including manual muscle testing using medical research council score (MRC), and motor function measure (MFM) were recorded each year for a period ranging from 1 to 2 years. For the MRI measurements, we used a new quantitative index, i.e., the mean pixel intensity (MPI) calculated from the pixel-intensity distribution in T1 weighted images. The corresponding MPI scores were calculated for each thigh, for each compartment and for both thighs totally (MPItotal). The total mean pixel intensity (MPItotal) refers to the sum of each pixel signal intensity divided by the corresponding number of pixels. An increased MPItotal indicates both a raised fat infiltration together with a reduced muscle volume thereby illustrating disease progression. Clinical scores did not change significantly over time whereas MPItotal increased significantly from an initial averaged value of 39.6 to 41.1 with a corresponding rate of 0.62/year. While clinical scores and MPItotal measured at the start of the study were significantly related, no correlation was found between the rate of MPItotal and MRC sum score changes, MFMtotal and MFM subscores. The relative rate of MPItotal change was 2.3% (0.5-4.3)/year and was significantly higher than the corresponding rates measured for MRCS 0% (0-1.7) /year and MFMtotal 0% (0-2.0) /year (p = 0.000). On the basis of these results, we suggested that muscle MRI and more particularly the MPItotal index could be used as a reliable biomarker and outcome measure of disease progression. In slowly progressive myopathies such as FSHD, the MPItotal index might reveal subclinical changes, which could not be evidenced using clinical scales over a short period of time.
    Mots-clés : crmbm, Humans, Magnetic Resonance Imaging, msk, Muscle, Skeletal, Muscular Dystrophy, Facioscapulohumeral.

  • Fouré, A & Bendahan, D 2017, “Is Branched-Chain Amino Acids Supplementation an Efficient Nutritional Strategy to Alleviate Skeletal Muscle Damage? A Systematic Review”, Nutrients, vol. 9, no. 10.
    Résumé : Amino acids and more precisely, branched-chain amino acids (BCAAs), are usually consumed as nutritional supplements by many athletes and people involved in regular and moderate physical activities regardless of their practice level. BCAAs have been initially shown to increase muscle mass and have also been implicated in the limitation of structural and metabolic alterations associated with exercise damage. This systematic review provides a comprehensive analysis of the literature regarding the beneficial effects of BCAAs supplementation within the context of exercise-induced muscle damage or muscle injury. The potential benefit of a BCAAs supplementation was also analyzed according to the supplementation strategy-amount of BCAAs, frequency and duration of the supplementation-and the extent of muscle damage. The review protocol was registered prospectively with Prospective Register for Systematic Reviews (registration number CRD42017073006) and followed Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. Literature search was performed from the date of commencement until August 2017 using four online databases (Medline, Cochrane library, Web of science and ScienceDirect). Original research articles: (i) written in English; (ii) describing experiments performed in Humans who received at least one oral BCAAs supplementation composed of leucine, isoleucine and valine mixture only as a nutritional strategy and (iii) reporting a follow-up of at least one day after exercise-induced muscle damage, were included in the systematic review analysis. Quality assessment was undertaken independently using the Quality Criteria Checklist for Primary Research. Changes in indirect markers of muscle damage were considered as primary outcome measures. Secondary outcome measures were the extent of change in indirect markers of muscle damage. In total, 11 studies were included in the analysis. A high heterogeneity was found regarding the different outcomes of these studies. The risk of bias was moderate considering the quality ratings were positive for six and neutral for three. Although a small number of studies were included, BCAAs supplementation can be efficacious on outcomes of exercise-induced muscle damage, as long as the extent of muscle damage was low-to-moderate, the supplementation strategy combined a high daily BCAAs intake (>200 mg kg-1 day-1) for a long period of time (>10 days); it was especially effective if taken prior to the damaging exercise.
    Mots-clés : branched-chain amino acids (BCAAs), crmbm, exercise-induced muscle damage, msk, nutritional strategy, skeletal muscle.

  • Fouré, A, Duhamel, G, Vilmen, C, Bendahan, D, Jubeau, M & Gondin, J 2017, “Fast measurement of the quadriceps femoris muscle transverse relaxation time at high magnetic field using segmented echo-planar imaging”, Journal of magnetic resonance imaging: JMRI, vol. 45, no. 2, p. 356-368.
    Résumé : PURPOSE: To assess and validate a technique for transverse relaxation time (T2 ) measurements of resting and recovering skeletal muscle following exercise with a high temporal resolution and large volume coverage using segmented spin-echo echo-planar imaging (sSE-EPI). MATERIALS AND METHODS: Experiments were performed on a 3T magnetic resonance imaging (MRI) scanner using a multislice sSE-EPI technique applied at different echo times (TEs). T2 measurements were first validated in vitro in calibrated T2 phantoms (range: 25-152 ms) by comparing sSE-EPI, standard spin-echo (SE), and multislice multiecho (MSME) techniques (using a fitting procedure or a 2-TEs calculation). In vivo measurements of resting T2 quadriceps femoris (QF) muscle were performed with both sSE-EPI and MSME sequences. Finally, sSE-EPI was used to quantify T2 changes in recovering muscle after an exercise. RESULTS: T2 values measured in vitro with sSE-EPI were similar to those assessed with SE (P > 0.05). In vitro and in vivo T2 measurements obtained with sSE-EPI were independent of the T2 determination procedure (P > 0.05). In contrast, both in vitro and in vivo T2 values derived from MSME were significantly different when using 2-TEs calculation as compared to the fitting procedure (P < 0.05). sSE-EPI allowed the detection of increased T2 values in the QF muscle immediately after exercise (+14 ± 9%), while lower T2 values were recorded less than 2 min afterwards (P < 0.05). CONCLUSION: sSE-EPI sequence is a relevant method to monitor exercise-induced T2 changes of skeletal muscles over large volume coverage and to detect abnormal patterns of muscle activation. LEVEL OF EVIDENCE: 1 J. Magn. Reson. Imaging 2017;45:356-368.
    Mots-clés : crmbm, Exercise, MRI, msk, skeletal muscle, spin-echo sequence, T2.

  • Guenoun, D, Fouré, A, Pithioux, M, Guis, S, Le Corroller, T, Mattei, J-P, Pauly, V, Guye, M, Bernard, M, Chabrand, P, Champsaur, P & Bendahan, D 2017, “Correlative Analysis of Vertebral Trabecular Bone Microarchitecture and Mechanical Properties: A Combined Ultra-high Field (7 Tesla) MRI and Biomechanical Investigation”, Spine, vol. 42, no. 20, p. E1165-E1172.
    Résumé : STUDY DESIGN: High-resolution imaging and biomechanical investigation of ex-vivo vertebrae. OBJECTIVE: The aim of this study was to assess bone microarchitecture of cadaveric vertebrae using ultra-high field (UHF) 7 Tesla magnetic resonance imaging (MRI) and to determine whether the corresponding microarchitecture parameters were related to bone mineral density (BMD) and bone strength assessed by dual-energy x-ray absorptiometry (DXA) and mechanical compression tests. SUMMARY OF BACKGROUND DATA: Limitations of DXA for the assessment of bone fragility and osteoporosis have been recognized and criteria of microarchitecture alteration have been included in the definition of osteoporosis. Although vertebral fracture is the most common osteoporotic fracture, no study has assessed directly vertebral trabecular bone microarchitecture. METHODS: BMD of 24 vertebrae (L2, L3, L4) from eight cadavers was investigated using DXA. The bone volume fraction (BVF), trabecular thickness (Tb.Th), and trabecular spacing (Tb.Sp) of each vertebra were quantified using UHF MRI. Measurements were performed by two operators to characterize the inter-rater reliability. The whole set of specimens underwent mechanical compression tests to failure and the corresponding failure stress was calculated. RESULTS: The inter-rater reliability for bone microarchitecture parameters was good with intraclass correlation coefficients ranging from 0.82 to 0.94. Failure load and stress were significantly correlated with BVF, Tb.Sp, and BMD (P < 0.05). Tb.Th was only correlated with the failure stress (P < 0.05). Multiple regression analysis demonstrated that the combination of BVF and BMD improved the prediction of the failure stress from an adjusted R = 0.384 for BMD alone to an adjusted R = 0.414. CONCLUSION: We demonstrated for the first time that the vertebral bone microarchitecture assessed with UHF MRI was significantly correlated with biomechanical parameters. Our data suggest that the multimodal assessment of BMD and trabecular bone microarchitecture with UHF MRI provides additional information on the risk of vertebral bone fracture and might be of interest for the future investigation of selected osteoporotic patients. LEVEL OF EVIDENCE: N /A.
    Mots-clés : crmbm, msk.

  • Ogier, A, Sdika, M, Foure, A, Le Troter, A & Bendahan, D 2017, “Individual muscle segmentation in MR images: A 3D propagation through 2D non-linear registration approaches”, Conference proceedings: .. Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, vol. 2017, p. 317-320.
    Résumé : Manual and automated segmentation of individual muscles in magnetic resonance images have been recognized as challenging given the high variability of shapes between muscles and subjects and the discontinuity or lack of visible boundaries between muscles. In the present study, we proposed an original algorithm allowing a semi-automatic transversal propagation of manually-drawn masks. Our strategy was based on several ascending and descending non-linear registration approaches which is similar to the estimation of a Lagrangian trajectory applied to manual masks. Using several manually-segmented slices, we have evaluated our algorithm on the four muscles of the quadriceps femoris group. We mainly showed that our 3D propagated segmentation was very accurate with an averaged Dice similarity coefficient value higher than 0.91 for the minimal manual input of only two manually-segmented slices.
    Mots-clés : crmbm, msk.

  • Wegrzyk, J, Ranjeva, J-P, Fouré, A, Kavounoudias, A, Vilmen, C, Mattei, J-P, Guye, M, Maffiuletti, NA, Place, N, Bendahan, D & Gondin, J 2017, “Specific brain activation patterns associated with two neuromuscular electrical stimulation protocols”, Scientific Reports, vol. 7, no. 1, p. 2742.
    Résumé : The influence of neuromuscular electrical stimulation (NMES) parameters on brain activation has been scarcely investigated. We aimed at comparing two frequently used NMES protocols - designed to vary in the extent of sensory input. Whole-brain functional magnetic resonance imaging was performed in sixteen healthy subjects during wide-pulse high-frequency (WPHF, 100 Hz-1 ms) and conventional (CONV, 25 Hz-0.05 ms) NMES applied over the triceps surae. Each protocol included 20 isometric contractions performed at 10% of maximal force. Voluntary plantar flexions (VOL) were performed as control trial. Mean force was not different among the three protocols, however, total current charge was higher for WPHF than for CONV. All protocols elicited significant activations of the sensorimotor network, cerebellum and thalamus. WPHF resulted in lower deactivation in the secondary somatosensory cortex and precuneus. Bilateral thalami and caudate nuclei were hyperactivated for CONV. The modulation of the NMES parameters resulted in differently activated/deactivated regions related to total current charge of the stimulation but not to mean force. By targeting different cerebral brain regions, the two NMES protocols might allow for individually-designed rehabilitation training in patients who can no longer execute voluntary movements.
    Mots-clés : crmbm, msk.


Journal Article

  • Fouré, A 2016, “New Imaging Methods for Non-invasive Assessment of Mechanical, Structural, and Biochemical Properties of Human Achilles Tendon: A Mini Review”, Frontiers in Physiology, vol. 7, p. 324.
    Résumé : The mechanical properties of tendon play a fundamental role to passively transmit forces from muscle to bone, withstand sudden stretches, and act as a mechanical buffer allowing the muscle to work more efficiently. The use of non-invasive imaging methods for the assessment of human tendon's mechanical, structural, and biochemical properties in vivo is relatively young in sports medicine, clinical practice, and basic science. Non-invasive assessment of the tendon properties may enhance the diagnosis of tendon injury and the characterization of recovery treatments. While ultrasonographic imaging is the most popular tool to assess the tendon's structural and indirectly, mechanical properties, ultrasonographic elastography, and ultra-high field magnetic resonance imaging (UHF MRI) have recently emerged as potentially powerful techniques to explore tendon tissues. This paper highlights some methodological cautions associated with conventional ultrasonography and perspectives for in vivo human Achilles tendon assessment using ultrasonographic elastography and UHF MRI.
    Mots-clés : crmbm, elastography, Magnetic Resonance Imaging, msk, tendinopathy, tendon stiffness, Ultrasonography.

  • Fouré, A, Nosaka, K, Gastaldi, M, Mattei, J-P, Boudinet, H, Guye, M, Vilmen, C, Le Fur, Y, Bendahan, D & Gondin, J 2016, “Effects of branched-chain amino acids supplementation on both plasma amino acids concentration and muscle energetics changes resulting from muscle damage: A randomized placebo controlled trial”, Clinical Nutrition (Edinburgh, Scotland), vol. 35, no. 1, p. 83-94.
    Résumé : BACKGROUND & AIMS: Branched-chain amino acids promote muscle-protein synthesis, reduce protein oxidation and have positive effects on mitochondrial biogenesis and reactive oxygen species scavenging. The purpose of the study was to determine the potential benefits of branched-chain amino acids supplementation on changes in force capacities, plasma amino acids concentration and muscle metabolic alterations after exercise-induced muscle damage. METHODS: (31)P magnetic resonance spectroscopy and biochemical analyses were used to follow the changes after such damage. Twenty six young healthy men were randomly assigned to supplemented branched-chain amino acids or placebo group. Knee extensors maximal voluntary isometric force was assessed before and on four days following exercise-induced muscle damage. Concentrations in phosphocreatine [PCr], inorganic phosphate [Pi] and pH were measured during a standardized rest-exercise-recovery protocol before, two (D2) and four (D4) days after exercise-induced muscle damage. RESULTS: No significant difference between groups was found for changes in maximal voluntary isometric force (-24% at D2 and -21% at D4). Plasma alanine concentration significantly increased immediately after exercise-induced muscle damage (+25%) in both groups while concentrations in glycine, histidine, phenylalanine and tyrosine decreased. No difference between groups was found in the increased resting [Pi] (+42% at D2 and +34% at D4), decreased resting pH (-0.04 at D2 and -0.03 at D4) and the slower PCr recovery rate (-18% at D2 and -24% at D4). CONCLUSIONS: The damaged muscle was not able to get benefits out of the increased plasma branched-chain amino acids availability to attenuate changes in indirect markers of muscle damage and muscle metabolic alterations following exercise-induced muscle damage.
    Mots-clés : crmbm, Double blind randomized placebo controlled trial, Exercise induced-muscle damage, Magnetic Resonance Spectroscopy, msk.

  • Le Troter, A, Fouré, A, Guye, M, Confort-Gouny, S, Mattei, J-P, Gondin, J, Salort-Campana, E & Bendahan, D 2016, “Volume measurements of individual muscles in human quadriceps femoris using atlas-based segmentation approaches”, Magma (New York, N.Y.), vol. 29, no. 2, p. 245-257.
    Résumé : OBJECTIVES: Atlas-based segmentation is a powerful method for automatic structural segmentation of several sub-structures in many organs. However, such an approach has been very scarcely used in the context of muscle segmentation, and so far no study has assessed such a method for the automatic delineation of individual muscles of the quadriceps femoris (QF). In the present study, we have evaluated a fully automated multi-atlas method and a semi-automated single-atlas method for the segmentation and volume quantification of the four muscles of the QF and for the QF as a whole. SUBJECTS AND METHODS: The study was conducted in 32 young healthy males, using high-resolution magnetic resonance images (MRI) of the thigh. The multi-atlas-based segmentation method was conducted in 25 subjects. Different non-linear registration approaches based on free-form deformable (FFD) and symmetric diffeomorphic normalization algorithms (SyN) were assessed. Optimal parameters of two fusion methods, i.e., STAPLE and STEPS, were determined on the basis of the highest Dice similarity index (DSI) considering manual segmentation (MSeg) as the ground truth. Validation and reproducibility of this pipeline were determined using another MRI dataset recorded in seven healthy male subjects on the basis of additional metrics such as the muscle volume similarity values, intraclass coefficient, and coefficient of variation. Both non-linear registration methods (FFD and SyN) were also evaluated as part of a single-atlas strategy in order to assess longitudinal muscle volume measurements. The multi- and the single-atlas approaches were compared for the segmentation and the volume quantification of the four muscles of the QF and for the QF as a whole. RESULTS: Considering each muscle of the QF, the DSI of the multi-atlas-based approach was high 0.87 ± 0.11 and the best results were obtained with the combination of two deformation fields resulting from the SyN registration method and the STEPS fusion algorithm. The optimal variables for FFD and SyN registration methods were four templates and a kernel standard deviation ranging between 5 and 8. The segmentation process using a single-atlas-based method was more robust with DSI values higher than 0.9. From the vantage of muscle volume measurements, the multi-atlas-based strategy provided acceptable results regarding the QF muscle as a whole but highly variable results regarding individual muscle. On the contrary, the performance of the single-atlas-based pipeline for individual muscles was highly comparable to the MSeg, thereby indicating that this method would be adequate for longitudinal tracking of muscle volume changes in healthy subjects. CONCLUSION: In the present study, we demonstrated that both multi-atlas and single-atlas approaches were relevant for the segmentation of individual muscles of the QF in healthy subjects. Considering muscle volume measurements, the single-atlas method provided promising perspectives regarding longitudinal quantification of individual muscle volumes.
    Mots-clés : crmbm, Fusion, Individual muscle volume measurements, MRI, msk, Multi-atlas-based segmentation, Non-linear registration, Quadriceps femoris muscle.


Journal Article

  • Fouré, A, Duhamel, G, Wegrzyk, J, Boudinet, H, Mattei, J-P, Le Troter, A, Bendahan, D & Gondin, J 2015, “Heterogeneity of muscle damage induced by electrostimulation: a multimodal MRI study”, Medicine and Science in Sports and Exercise, vol. 47, no. 1, p. 166-175.
    Résumé : PURPOSE: Neuromuscular electrostimulation (NMES) leads to a spatially fixed, synchronous, and superficial motor unit recruitment, which could induce muscle damage. Therefore, the extent of muscle damage and its spatial occurrence were expected to be heterogeneous across and along the quadriceps femoris (QF) muscles. The aim of the present study was to characterize muscle spatial heterogeneity in QF damage after a single bout of isometric NMES using multimodal magnetic resonance imaging (MRI). METHODS: Twenty-five young healthy males participated in this study. MRI investigations consisted of the assessment of muscle volume, transverse relaxation time (T2), and diffusion tensor imaging (DTI) in muscles positioned near the stimulation electrodes (i.e., vastus lateralis (VL) and vastus medialis (VM)) and muscles located outside the stimulated regions (i.e., vastus intermedius and rectus femoris). These measurements were performed 6 d before, and 2 d and 4 d (D4) after the NMES session. RESULTS: For the muscles placed in direct contact with the stimulation electrodes, volume (VL, +8.5%; VM, +3.8%), T2 (VL, +19.5%; VM, +6.7%) and radial diffusivity (λ3) (VL, + 7.3%; VM, +3.7%) significantly increased at D4. Whereas MRI parameter changes were larger for VL as compared with those for other QF muscles at D4, homogeneous alterations were found along all QF muscles. CONCLUSIONS: Isometric NMES induced specific and localized alterations in VL and VM, with heterogeneous damage amplitude among them. Potential effects of unaccustomed intermuscle shear stress during electrically evoked isometric contractions could be a key factor in the spatial occurrence and the extent of damage among QF muscles (especially in VL). The kinetics and extent of MRI changes varied between T2 and diffusion tensor imaging metrics, suggesting the involvement of different physiological processes.
    Mots-clés : crmbm, msk.

  • Fouré, A, Le Troter, A, Guye, M, Mattei, J-P, Bendahan, D & Gondin, J 2015, “Localization and quantification of intramuscular damage using statistical parametric mapping and skeletal muscle parcellation”, Scientific Reports, vol. 5, p. 18580.
    Résumé : In the present study, we proposed an original and robust methodology which combines the spatial normalization of skeletal muscle images, the statistical parametric mapping (SPM) analysis and the use of a specific parcellation in order to accurately localize and quantify the extent of skeletal muscle damage within the four heads of the quadriceps femoris. T2 maps of thigh muscles were characterized before, two (D2) and four (D4) days after 40 maximal isometric electrically-evoked contractions in 25 healthy young males. On the basis of SPM analysis of coregistrated T2 maps, the alterations were similarly detected at D2 and D4 in the superficial and distal regions of the vastus medialis (VM) whereas the proportion of altered muscle was higher in deep muscle regions of the vastus lateralis at D4 (deep: 35 ± 25%, superficial: 23 ± 15%) as compared to D2 (deep: 18 ± 13%, superficial: 17 ± 13%). The present methodology used for the first time on skeletal muscle would be of utmost interest to detect subtle intramuscular alterations not only for the diagnosis of muscular diseases but also for assessing the efficacy of potential therapeutic interventions and clinical treatment strategies.
    Mots-clés : crmbm, msk.

  • Fouré, A, Wegrzyk, J, LE Fur, Y, Mattei, J-P, Boudinet, H, Vilmen, C, Bendahan, D & Gondin, J 2015, “Impaired mitochondrial function and reduced energy cost as a result of muscle damage”, Medicine and Science in Sports and Exercise, vol. 47, no. 6, p. 1135-1144.
    Résumé : PURPOSE: Although it has been largely acknowledged that isometric neuromuscular electrostimulation (NMES) exercise induces larger muscle damage than voluntary contractions, the corresponding effects on muscle energetics remain to be determined. Voluntary exercise-induced muscle damage (EIMD) has been reported to have minor slight effects on muscle metabolic response to subsequent dynamic exercise, but the magnitude of muscle energetics alterations for NMES EIMD has never been documented. METHODS: P magnetic resonance spectroscopy measurements were performed in 13 young healthy males during a standardized rest-exercise-recovery protocol before (D0) and 2 d (D2) and 4 d (D4) after NMES EIMD on knee extensor muscles. Changes in kinetics of phosphorylated metabolite concentrations (i.e., phosphocreatine [PCr], inorganic phosphate [Pi], and adenosine triphosphate [ATP]) and pH were assessed to investigate aerobic and anaerobic rates of ATP production and energy cost of contraction (Ec). RESULTS: Resting [Pi]/[PCr] ratio increased at D2 (+39%) and D4 (+29%), mainly owing to the increased [Pi] (+43% and +32%, respectively), whereas a significant decrease in resting pH was determined (-0.04 pH unit and -0.03 pH unit, respectively). PCr recovery rate decreased at D2 (-21%) and D4 (-23%) in conjunction with a significantly decreased total rate of ATP production at D4 (-18%) mainly owing to an altered aerobic ATP production (-19%). Paradoxically, Ec was decreased at D4 (-21%). CONCLUSION: Overall, NMES EIMD led to intramuscular acidosis in resting muscle and mitochondrial impairment in exercising muscle. Alterations of noncontractile processes and/or adaptive mechanisms to muscle damage might account for the decreased Ec during the dynamic exercise.
    Mots-clés : crmbm, msk.
  • Hauraix, H, Foure, A, Dorel, S, Cornu, C & Nordez, A 2015, “Muscle and tendon stiffness assessment using the alpha method and ultrafast ultrasound”, European Journal of Applied Physiology, vol. 115, no. 7, p. 1393-1400.
    Résumé : 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 +/- A 83 to 720 +/- A 265 N/mm with an increasing level of force (from
    Mots-clés : Ankle joint, Plantar flexors, Gastrocnemius, Fascicles, Tendon, msk, series elastic component, load-displacement properties, triceps surae aponeurosis, frame rate ultrasound, quick-release method, in-vivo, mechanical-properties, achilles-tendon, passive parts, electromechanical delay.

  • Wegrzyk, J, Fouré, A, Le Fur, Y, Maffiuletti, NA, Vilmen, C, Guye, M, Mattei, J-P, Place, N, Bendahan, D & Gondin, J 2015, “Responders to Wide-Pulse, High-Frequency Neuromuscular Electrical Stimulation Show Reduced Metabolic Demand: A 31P-MRS Study in Humans”, PloS One, vol. 10, no. 11, p. e0143972.
    Résumé : Conventional (CONV) neuromuscular electrical stimulation (NMES) (i.e., short pulse duration, low frequencies) induces a higher energetic response as compared to voluntary contractions (VOL). In contrast, wide-pulse, high-frequency (WPHF) NMES might elicit-at least in some subjects (i.e., responders)-a different motor unit recruitment compared to CONV that resembles the physiological muscle activation pattern of VOL. We therefore hypothesized that for these responder subjects, the metabolic demand of WPHF would be lower than CONV and comparable to VOL. 18 healthy subjects performed isometric plantar flexions at 10% of their maximal voluntary contraction force for CONV (25 Hz, 0.05 ms), WPHF (100 Hz, 1 ms) and VOL protocols. For each protocol, force time integral (FTI) was quantified and subjects were classified as responders and non-responders to WPHF based on k-means clustering analysis. Furthermore, a fatigue index based on FTI loss at the end of each protocol compared with the beginning of the protocol was calculated. Phosphocreatine depletion (ΔPCr) was assessed using 31P magnetic resonance spectroscopy. Responders developed four times higher FTI's during WPHF (99 ± 37 ×103 N.s) than non-responders (26 ± 12 ×103 N.s). For both responders and non-responders, CONV was metabolically more demanding than VOL when ΔPCr was expressed relative to the FTI. Only for the responder group, the ∆PCr/FTI ratio of WPHF (0.74 ± 0.19 M/N.s) was significantly lower compared to CONV (1.48 ± 0.46 M/N.s) but similar to VOL (0.65 ± 0.21 M/N.s). Moreover, the fatigue index was not different between WPHF (-16%) and CONV (-25%) for the responders. WPHF could therefore be considered as the less demanding NMES modality-at least in this subgroup of subjects-by possibly exhibiting a muscle activation pattern similar to VOL contractions.
    Mots-clés : crmbm, msk.
  • Wegrzyk, J, Foure, A, Vilmen, C, Ghattas, B, Maffiuletti, NA, Mattei, J-P, Place, N, Bendahan, D & Gondin, J 2015, “Extra Forces induced by wide-pulse, high-frequency electrical stimulation: Occurrence, magnitude, variability and underlying mechanisms”, Clinical Neurophysiology, vol. 126, no. 7, p. 1400-1412.
    Résumé : 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.
    Mots-clés : Adult, Cluster Analysis, crmbm, Electric Stimulation, Electromyography, EMG, Evoked Potentials, Extra Forces, Female, H-Reflex, Humans, Male, msk, Muscle Contraction, Muscle Strength, Muscle, Skeletal, NMES, NMES, Extra Forces, Triceps surae, Responder, EMG, plateau-like behavior, spinal-cord-injury, post-activation depression, human skeletal-muscle, catch-like property, soleus h-reflex, neuromuscular stimulation, triceps surae, m-waves, presynaptic inhibition, Responder, Single-Blind Method, Triceps surae.


Journal Article

  • Fouré, A, Nosaka, K, Wegrzyk, J, Duhamel, G, Le Troter, A, Boudinet, H, Mattei, J-P, Vilmen, C, Jubeau, M, Bendahan, D & Gondin, J 2014, “Time course of central and peripheral alterations after isometric neuromuscular electrical stimulation-induced muscle damage”, PloS One, vol. 9, no. 9, p. e107298.
    Résumé : Isometric contractions induced by neuromuscular electrostimulation (NMES) have been shown to result in a prolonged force decrease but the time course of the potential central and peripheral factors have never been investigated. This study examined the specific time course of central and peripheral factors after isometric NMES-induced muscle damage. Twenty-five young healthy men were subjected to an NMES exercise consisting of 40 contractions for both legs. Changes in maximal voluntary contraction force of the knee extensors (MVC), peak evoked force during double stimulations at 10 Hz (Db10) and 100 Hz (Db100), its ratio (10∶100), voluntary activation, muscle soreness and plasma creatine kinase activity were assessed before, immediately after and throughout four days after NMES session. Changes in knee extensors volume and T2 relaxation time were also assessed at two (D2) and four (D4) days post-exercise. MVC decreased by 29% immediately after NMES session and was still 19% lower than the baseline value at D4. The decrease in Db10 was higher than in Db100 immediately and one day post-exercise resulting in a decrease (-12%) in the 10∶100 ratio. On the contrary, voluntary activation significantly decreased at D2 (-5%) and was still depressed at D4 (-5%). Muscle soreness and plasma creatine kinase activity increased after NMES and peaked at D2 and D4, respectively. T2 was also increased at D2 (6%) and D4 (9%). Additionally, changes in MVC and peripheral factors (e.g., Db100) were correlated on the full recovery period, while a significant correlation was found between changes in MVC and VA only from D2 to D4. The decrease in MVC recorded immediately after the NMES session was mainly due to peripheral changes while both central and peripheral contributions were involved in the prolonged force reduction. Interestingly, the chronological events differ from what has been reported so far for voluntary exercise-induced muscle damage.
    Mots-clés : Adult, crmbm, Electric Stimulation, Electromyography, Exercise, Humans, Isometric Contraction, Knee, Male, Muscle Contraction, Muscle Fatigue, Neuromuscular Diseases.


Journal Article

  • Fouré, A, Nordez, A & Cornu, C 2013, “Effects of eccentric training on mechanical properties of the plantar flexor muscle-tendon complex”, Journal of Applied Physiology (Bethesda, Md.: 1985), vol. 114, no. 5, p. 523-537.
    Résumé : 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.
    Mots-clés : Achilles Tendon, Adult, Ankle Joint, Education, Elasticity, Electromyography, Humans, Isometric Contraction, Male, Mechanical Phenomena, Muscle, Skeletal, Musculoskeletal Physiological Phenomena, Range of Motion, Articular, Tendons, Torque, Young Adult.


Journal Article

  • Fouré, A, Cornu, C & Nordez, A 2012, “Is tendon stiffness correlated to the dissipation coefficient?”, Physiological Measurement, vol. 33, no. 1, p. N1-9.
    Résumé : The assessment of Achilles tendon mechanical properties in vivo has received much attention in the literature. Many studies investigated mechanical properties by assessing tendon stiffness. Despite tendon dissipative properties being representative of a storage-recoil process, its determination has received minimal attention in the literature. The aim of this study was to determine if Achilles tendon stiffness is associated with dissipative properties. The cross-sectional area, stiffness and dissipation coefficient of the Achilles tendon were measured in 35 subjects. No significant correlation was found between stiffness and the dissipation coefficient, irrespective of stiffness normalization with cross-sectional area (P > 0.05). Thus, it appears that both stiffness and dissipative properties must be assessed to determine the storage-recoil process capacities of the Achilles tendon in order to precisely characterize changes in the tendon mechanical properties after chronic interventions or rehabilitation programs.
    Mots-clés : Achilles Tendon, Adolescent, Biomechanical Phenomena, Elastic Modulus, Humans, Weight-Bearing, Young Adult.

  • Fouré, A, Cornu, C, McNair, PJ & Nordez, A 2012, “Gender differences in both active and passive parts of the plantar flexors series elastic component stiffness and geometrical parameters of the muscle-tendon complex”, Journal of Orthopaedic Research: Official Publication of the Orthopaedic Research Society, vol. 30, no. 5, p. 707-712.
    Résumé : Men are reportedly at higher risk of plantar flexor muscle injury and Achilles tendon ruptures than women. Biomechanical parameters are thought to play a role in the higher frequency of injury to males. One parameter is the stiffness of tissues; a stiff tissue cannot absorb sufficient energy with loading, and subsequently may be more likely to be injured. Thus, our purpose was to investigate the gender difference in the geometrical parameters of plantar flexor's muscle-tendon complex and the stiffness of both active and passive parts of the series elastic component (S(SEC1) and S(SEC2) , respectively). Using the alpha method on data obtained from quick stretches to the plantar flexors performed during isometric contractions, S(SEC1) and S(SEC2) were assessed. Plantar flexor muscles and Achilles tendon cross-sectional areas (CSA(TS) and CSA(AT) , respectively) were determined in young healthy men (n = 49) and women (n = 31). The findings showed that S(SEC2) was higher in men (p < 0.001), but this difference was not apparent when S(SEC2) was normalized to CSA(AT) (p > 0.05). In contrast, S(SEC1) was lower in men (p < 0.001) and remained so after normalization to CSA(TS) . Higher joint stiffness observed in men was notably influenced by lever arm length. Thus, the results of this study have implications for performance and injury.
    Mots-clés : Achilles Tendon, Elasticity, Female, Humans, Male, Muscle, Skeletal, Sex Characteristics.

  • Fouré, A, Nordez, A & Cornu, C 2012, “Effects of plyometric training on passive stiffness of gastrocnemii muscles and Achilles tendon”, European Journal of Applied Physiology, vol. 112, no. 8, p. 2849-2857.
    Résumé : Plyometric training is commonly used to improve athletic performance; however, it is unclear how each component of the muscle-tendon complex (MTC) is affected by this intervention. The effects of 14 weeks of plyometric training on the passive stiffness of the gastrocnemii muscles and Achilles tendon was determined simultaneously to assess possible local adaptations of elastic properties. The passive force-length relationship of the gastrocnemii MTC and elongation of the gastrocnemii muscles were determined using ultrasonography during passive cyclic stretching in 19 subjects divided into trained (n = 9) and control (n = 10) groups. An upward trend in stiffness of the gastrocnemii MTC (P = 0.09) and a significant increase in the intrinsic gastrocnemii muscle stiffness were found (P < 0.05). In contrast, no significant change in gastrocnemii tendon stiffness, or in muscle and tendon geometry, was determined (P > 0.05). Considering the lack of change in gastrocnemii muscle geometry, the change in the gastrocnemii muscle stiffness may be mainly due to a change in the intrinsic mechanical properties of the muscular tissues.
    Mots-clés : Achilles Tendon, Adaptation, Physiological, Adolescent, Analysis of Variance, Ankle Joint, Biomechanical Phenomena, Elasticity, Electromyography, France, Humans, Male, Models, Biological, Muscle Contraction, Muscle Strength, Muscle Strength Dynamometer, Muscle, Skeletal, Plyometric Exercise, Range of Motion, Articular, Time Factors, Torque, Young Adult.


Journal Article

  • Fouré, A, Nordez, A, McNair, P & Cornu, C 2011, “Effects of plyometric training on both active and passive parts of the plantarflexors series elastic component stiffness of muscle-tendon complex”, European Journal of Applied Physiology, vol. 111, no. 3, p. 539-548.
    Résumé : 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 (p < 0.05). In contrast, a significant decrease in the active part of the SEC stiffness was observed (p < 0.05). No significant changes in plantarflexor muscles CSA, architecture and Achilles tendon CSA were seen (p > 0.05). 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.
    Mots-clés : Achilles Tendon, Adolescent, Athletic Performance, Elasticity, Electromyography, Humans, Isometric Contraction, Male, Models, Biological, Muscles, Musculoskeletal Physiological Phenomena, Physical Fitness, Pliability, Running, Torque, Young Adult.


Journal Article

  • Fouré, A, Nordez, A & Cornu, C 2010, “In vivo assessment of both active and passive parts of the plantarflexors series elastic component stiffness using the alpha method: a reliability study”, International Journal of Sports Medicine, vol. 31, no. 1, p. 51-57.
    Résumé : The aim of this study was to investigate the reliability of an in vivo adaptation of the short range stiffness experiment associated with the application of a mathematical model to determine the stiffness of both torque dependent and independent components of the plantarflexors series elastic component. Fourteen subjects participated in this study. The experimental protocol consisted of quickly moving the ankle joint in dorsiflexion during constant voluntary isometric plantarflexion at 7 submaximal torque levels. Relationships between joint stiffness and torque were established and the stiffness of both torque dependent and independent components were determined using the alpha method. The day-to-day reliability was assessed for joint stiffness and stiffness of both torque dependent and independent components (ICC higher than 0.88 and CVs lower than 6.0%). This method could then be used to better understand adaptive subjacent mechanisms to assess the effects of training protocols, and the rehabilitation of neuromuscular pathologies or traumatisms.
    Mots-clés : Adult, Ankle Joint, Biomechanical Phenomena, Elasticity, Electromyography, Female, Humans, Isometric Contraction, Male, Models, Theoretical, Reproducibility of Results, Torque, Young Adult.

  • Fouré, A, Nordez, A & Cornu, C 2010, “Plyometric training effects on Achilles tendon stiffness and dissipative properties”, Journal of Applied Physiology (Bethesda, Md.: 1985), vol. 109, no. 3, p. 849-854.
    Résumé : The aim of this study was to determine the effects of 14 wk of plyometric training on mechanical properties of the Achilles tendon. Nineteen subjects were randomly assigned to trained or control group. Cross-sectional area (CSA), stiffness, and dissipation coefficient of the Achilles tendon were measured before and after the training period. In the trained group, a decrease in dissipation coefficient (-35.0%; P<0.05) and an upward trend in stiffness (+24.1%) of the Achilles tendon was found, without any changes in Achilles tendon CSA (P>0.05). Plyometric training enhances the muscular tension transmission mainly through a reduction in energy dissipated by the tendon. The lack of changes in the Achilles tendon CSA indicates that changes in mechanical properties would mainly result from a qualitative change in tendinous tissues rather than from changes in the geometry of the Achilles tendon.
    Mots-clés : Achilles Tendon, Adolescent, Biomechanical Phenomena, Elasticity, Exercise, Humans, Male, Time Factors, Torque, Young Adult.

  • Nordez, A, Fouré, A, Dombroski, EW, Mariot, J-P, Cornu, C & McNair, PJ 2010, “Improvements to Hoang et al.'s method for measuring passive length-tension properties of human gastrocnemius muscle in vivo”, Journal of Biomechanics, vol. 43, no. 2, p. 379-382.
    Résumé : While the passive mechanical properties of a musculo-articular complex can be determined using the relationship between the articular angle and the passive torque developed in resistance to motion, the properties of different structures of the musculo-articular complex cannot be easily assessed. Recently, an elegant method has been proposed to estimate the passive length-tension properties of gastrocnemius muscle-tendon unit (Hoang et al., 2005). In the present paper, two improvements of this method are proposed to decrease the number of parameters required to assess the passive length-tension relationship from 9 to 2. Furthermore, these two parameters have physical meaning as they represent a passive muscle-tendon stiffness index (alpha) and the muscle-tendon slack length (l(0)). alpha and l(0) are relevant clinical parameters to study the chronic effects of aging, training protocols or neuromuscular pathologies on the passive mechanical properties of the muscle-tendon unit. Eight healthy subjects performed passive loading/unloading cycles at 5 degrees /s with knee angle at 6 knee angles to assess the torque-angle relationships and to apply the modified method. Numerical optimization was used to minimize the squared error between the experimental and the modeled relationships. The experiment was performed twice to assess the reliability of alpha and l(0) across days. The results showed that the reliability of the two parameters was good (alpha: ICC=0.82, SEM=6.1m(-1), CV=6.3% and l(0): ICC=0.83, SEM=0.29 cm, CV=0.9%). Using a sensitivity analysis, it was shown that the numerical solution was unique. Overall, the findings may provide increased interest in the method proposed by Hoang et al. (2005).
    Mots-clés : Adult, Biomechanical Phenomena, Elasticity, Humans, Knee Joint, Male, Models, Biological, Muscle Contraction, Muscle, Skeletal, Tendons, Torque, Young Adult.


Journal Article

  • Fouré, A, Nordez, A, Guette, M & Cornu, C 2009, “Effects of plyometric training on passive stiffness of gastrocnemii and the musculo-articular complex of the ankle joint”, Scandinavian Journal of Medicine & Science in Sports, vol. 19, no. 6, p. 811-818.
    Résumé : This study aimed to determine simultaneously the effects of plyometric training on the passive stiffness of the ankle joint musculo-articular complex, the gastrocnemii muscle-tendon complex (MTC) and the Achilles tendon in order to assess possible local adaptations of elastic properties. Seventeen subjects were divided into a trained (TG) group and a control (CG) group. They were tested before and after 8 weeks of a plyometric training period. The ankle joint range of motion (RoM), the global musculo-articular passive stiffness of the ankle joint, the maximal passive stiffness of gastrocnemii and the stiffness of the Achilles tendon during isometric plantar flexion were determined. A significant increase in the jump performances of TG relative to CG was found (squat jumps: +17.6%, P=0.008; reactive jumps: +19.8%, P=0.001). No significant effect of plyometric training was observed in the ankle joint RoM, musculo-articular passive stiffness of the ankle joint or Achilles tendon stiffness (P>0.05). In contrast, the maximal passive stiffness of gastrocnemii of TG increased after plyometric training relative to CG (+33.3%, P=0.001). Thus, a specific adaptation of the gastrocnemii MTC occurred after plyometric training, without affecting the global passive musculo-articular stiffness of the ankle joint.
    Mots-clés : Ankle Joint, Biomechanical Phenomena, Humans, Isometric Contraction, Male, Muscle, Skeletal, Pilot Projects, Range of Motion, Articular, Treatment Outcome, Young Adult.
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