Running from Paris to Beijing: biomechanical and physiological consequences

Abstract The purpose of this study was to examine the physiological and biomechanical changes occurring in a subject after running 8,500 km in 161 days (i.e. 52.8 km daily). Three weeks before, 3 weeks after (POST) and 5 months after (POST?5) running from Paris to Beijing, energy cost of running (Cr), knee flexor and extensor isokinetic strength and biomechanical parameters (using a treadmill dynamometer) at different velocities were assessed in an experienced ultra-runner. At POST, there was a tendency toward a 'smoother' running pattern, as shown by (a) a higher stride frequency and duty factor, and a reduced aerial time without a change in contact time, (b) a lower maximal vertical force and loading rate at impact and (c) a decrease in both potential and kinetic energy changes at each step. This was associated with a detrimental effect on Cr (?6.2%) and a loss of strength at all angular velocities for both knee flexors and extensors. At POST?5, the subject returned to his original running patterns at low but not at high speeds and maximal strength remained reduced at low angular velocities (i.e. at high levels of force). It is suggested that the running pattern changes observed in the present study were a strategy adopted by the subject to reduce the deleterious effects of long distance running. However, the running pattern changes could partly be linked to the decrease in maximal strength

Lactate recovery kinetics in response to high-intensity exercises

International audienc

Place de l électrocardiogramme de repos lors d une consultation en cabinet de médecine générale en vue de la rédaction d un certificat de non contre-indication apparente à la pratique d un sport (opinion et pratique des médecins généralistes de la Loire)

En mars 2009, la Société Française de Cardiologie, en accord avec la recommandation européenne, préconisait par consensus formalisé la réalisation, au cours des visites de non contre-indication apparente à la pratique d une activité sportive, d un électrocardiogramme de repos douze dérivations. Celui-ci devrait être réalisé systématiquement lors de la toute première délivrance de licence quel que soit l âge puis tous les trois ans chez le sportif entre 12 et 20 ans et enfin tous les cinq ans entre 20 et 35 ans. Cet examen serait alors à la charge du patient ou de sa fédération sportive. En effet, en logique de prévention, cet électrocardiogramme ne devrait pas être pris en charge par les organismes sociaux, pas plus que ne peut l être l acte de consultation correspondant à l établissement d un certificat de non contre-indication à la pratique sportive. En janvier 2009, nous avons interrogé les médecins généralistes de la Loire à l aide d un questionnaire afin d évaluer leur pratique et leur opinion quant à cet examen. 74.5% d entre eux ne considèrent pas utile la réalisation systématique de cet ECG dans le cadre du suivi du sportif en médecine générale, le considérant comme une perte de temps et ne les rassurant pas d un point de vue médico-légal. 62.5 % des médecins interrogés jugent que cet examen de dépistage devrait être soumis à un remboursement par la sécurité sociale. Nous mettons ici en exergue la discordance entre les recommandations actuelles et les pratiques et opinions des médecins généralistes censés l appliquer dans la Loire.ST ETIENNE-BU Médecine (422182102) / SudocSudocFranceF

Running from Paris to Beijing: biomechanical and physiological consequences

International audienceThe purpose of this study was to examine the physiological and biomechanical changes occurring in a subject after running 8,500 km in 161 days (i.e. 52.8 km daily). Three weeks before, 3 weeks after (POST) and 5 months after (POST+5) running from Paris to Beijing, energy cost of running (Cr), knee flexor and extensor isokinetic strength and biomechanical parameters (using a treadmill dynamometer) at different velocities were assessed in an experienced ultra-runner. At POST, there was a tendency toward a 'smoother' running pattern, as shown by (a) a higher stride frequency and duty factor, and a reduced aerial time without a change in contact time, (b) a lower maximal vertical force and loading rate at impact and (c) a decrease in both potential and kinetic energy changes at each step. This was associated with a detrimental effect on Cr (+6.2%) and a loss of strength at all angular velocities for both knee flexors and extensors. At POST+5, the subject returned to his original running patterns at low but not at high speeds and maximal strength remained reduced at low angular velocities (i.e. at high levels of force). It is suggested that the running pattern changes observed in the present study were a strategy adopted by the subject to reduce the deleterious effects of long distance running. However, the running pattern changes could partly be linked to the decrease in maximal strength

Energy Cost and Mechanical Work of Walking during Load Carriage in Soldiers

International audienceIn the military context, soldiers carry equipments of total mass often exceeding 30%-40% of their body mass (BM) and complexly distributed around their body (backpack, weapons, electronics, protections, etc.), which represents severe load carrying conditions. Purpose: This study aimed to better understand the effects of load carriage on walking energetics and mechanics during military-type walking. Methods: Ten male infantrymen recently retired from the French Foreign Legion performed 3-min walking trials at a constant speed of 4 km[middle dot]h-1 on an instrumented treadmill, during which walking pattern spatiotemporal parameters, energy cost (CW), external mechanical work (Wext), and the work done by one leg against the other during the double-contact period (Wint,dc) were specifically assessed. Three conditions were tested: (i) light sportswear (SP, reference condition considered as unloaded), (ii) battle equipment (BT, ~22 kg, ~27% of subjects' BM, corresponding to a military intermediate load), and (iii) road march equipment (RM, ~38 kg, ~46% of subjects' BM, corresponding to a military high load). Results: Repeated-measures ANOVA showed that military equipment carriage significantly (i) altered the spatiotemporal pattern of walking (all P \textless 0.01), (ii) increased absolute gross and net CW (P \textless 0.0001), and (iii) increased both absolute and mass-relative Wext (P \textless 0.01) and Wint,dc (P \textless 0.0001) but did not alter the inverted pendulum recovery or locomotor efficiency. Conclusions: Military equipments carriage induced significant changes in walking mechanics and energetics, but these effects appeared not greater than those reported with loads carried around the waist and close to the center of mass. This result was not expected because the latter has been hypothesized to be the optimal method of load carriage from a metabolic standpoint

Bilan des connaissances en médecine du sport chez les internes en médecine générale

Introduction : Le sport connaît depuis quelques années un essor sans précédent dans la société. Toutefois, la pratique d une activité sportive peut-être le vecteur de nombreuses pathologies et d événements dramatiques. Les médecins sont-ils préparés à ce phénomène de société ? La formation théorique en médecine du sport chez les internes en médecine générale (IMG) est-elle adaptée et suffisante ? Objectif : Evaluer le pourcentage d IMG possédant une bonne formation en médecine du sport par l intermédiaire d un questionnaire téléphonique. Rechercher une amélioration du contenu de la formation entre les internes n étant pas titulaire d une licence de remplacement et les internes la possédant mais non thésés. Méthodologie : Un groupe de 908 internes composés de 500 IMG non remplaçants et 408 IMG remplaçants interrogés par téléphone. Ils ont répondu à 10 items chacun pour établir un score amenant à une moyenne de groupe. Résultats : L ensemble des internes ont un score moyen de 4.35 (+-2.3). La moyenne des notes des remplaçants est significativement plus élevée que celle des non-remplaçants : 5.09 + 2.00 vs 3.75 + 2.36, p<0.0001. Il n y a pas de différence de niveau significative entre les régions de France métropolitaine. Conclusion : L analyse des résultats montre que l enseignement en médecine du sport n est pas efficace. Il serait souhaitable de modifier le système en incitant aux Facultés de proposer des stages pratiques de médecine du sport et de l intégrer dans les cours fondamentaux.ST ETIENNE-BU Médecine (422182102) / SudocSudocFranceF

Effects of extreme-duration heavy load carriage on neuromuscular function and locomotion: a military-based study

International audienceTrekking and military missions generally consist of carrying heavy loads for extreme durations. These factors have been separately shown to be sources of neuromuscular (NM) fatigue and locomotor alterations. However, the question of their combined effects remains unresolved, and addressing this issue required a representative context. PURPOSE: The aim was to investigate the effects of extreme-duration heavy load carriage on NM function and walking characteristics.METHODS: Ten experienced infantrymen performed a 21-h simulated military mission (SMM) in a middle-mountain environment with equipment weighing ∼27 kg during battles and ∼43 kg during marches. NM function was evaluated for knee extensors (KE) and plantar flexors (PF) pre- and immediately post-SMM using isometric maximal voluntary contraction (MVC) measurement, neural electrical stimulation and surface EMG. The twitch-interpolation method was used to assess central fatigue. Peripheral changes were examined by stimulating the muscle in the relaxed state. The energy cost, mechanical work and spatio-temporal pattern of walking were also evaluated pre-/post-SMM on an instrumented treadmill in three equipment conditions: Sportswear, Battle and March.RESULTS: After the SMM, MVC declined by -10.2±3.6% for KE (P\textless0.01) and -10.7±16.1% for PF (P = 0.06). The origin of fatigue was essentially peripheral for both muscle groups. A trend toward low-frequency fatigue was detected for KE (5.5%, P = 0.08). These moderate NM alterations were concomitant with a large increase in perceived fatigue from pre- (rating of 8.3±2.2) to post-SMM (15.9±2.1, P\textless0.01). The SMM-related fatigue did not alter walking energetics or mechanics, and the different equipment carried on the treadmill did not interact with this fatigue either.CONCLUSION: this study reports the first data on physiological and biomechanical consequences of extreme-duration heavy load carriage. Unexpectedly, NM function alterations due to the 21-h SMM were moderate and did not alter walking characteristics.CLINICAL TRIAL REGISTRATION: Name: Effect of prolonged military exercises with high load carriage on neuromuscular fatigue and physiological/biomechanical responses. Number: NCT01127191

Potentiated peak twitch of knee extensors (KE) and plantar flexors (PF), and M-wave characteristics of <i>vastus lateralis</i> (<i>VL</i>) and <i>soleus</i> (<i>SOL</i>) muscles, before (PRE) and after (POST) the Simulated Military Mission.

<p>Data are presented as mean ± SD.</p

Energy cost of walking in Sport (SP), Battle (BT) and Road March (RM) conditions, before (PRE) and after (POST) the Simulated Military Mission.

<p>Values are presented as mean ± SD. ANOVA <i>P</i> values represent the main effects of time (T) and equipment (E), and the interaction effect (T×E). Post-hoc results are presented as:</p>£<p>SP< BT < RM;</p>#<p>SP< BT = RM;</p>$<p>SP> RM.</p><p><i>C</i>_W: energy cost of walking; <i>C</i>_W.TM: energy cost of walking normalized to the total mass (TM) moving on the treadmill, i.e. subject plus equipment.</p