INFLUENCE OF REST PERIOD ON ELECTRICAL STIMULATION EFFICIENCY

INTRODUCTION: Electrical stimulation (ES) is now widely used as a modality of strengthening in healthy subjects and highly trained athletes. Most of the previous studies have reported that training by ES induces strength gains (Portmann, 1991; Fredon & Poumarat, 1995). Pulse parameters and stimulus regimens are well documented, especially for frequency of stimulation and electrode localization (Ferry & Poumarat, 1994; Ferry et al., 1994). There is a lack of information on training protocols. These should include periodic rest periods to minimize muscle fatigue and maintain an adequate level of contraction during the training session. The aim of this paper is to clarify the effect of rest periods on muscular performance

MECHANICAL STRESS ON KNEES DURING HALF-SQUAT EXERCISES

INTRODUCTION Articular forces and moments have been found to be affected by the lifting technique in ergonomics (Trafirnow et al., 1993) and in weight-training (Poumarat et al.,1989).While these researchers have improved our understanding of biomechanical aspects of lifting as related to the spine and the lower extremities, most of them remain related to either static orquasi-static conditions. The purpose of this study was to determine the mechanical stress on the knee joint using a 3-D dynamic model. MATERIALS AND METHODS Three male volunteer students participated in the study. They were asked to perform three different sets of 10 half-squat exercises: no load, 100% and 120% of total body mass of the subject additional weight. To determine kinematic data, the movement of the half-squat exercises was recorded using the Mac Reflex optoelectronic system (4 cameras) with markers on the left lower extremity at the fust metatarsal, the external rnalleolus, the external lateral femoral condyle and the greater trochanter. A six components force-plate (AMTI) provided kinetic data. Compressive and the shear forces acting on the thigh at the knee joint were calculated where; Fx represents the compressive force; Mx, the external rotatory moment of the thigh; Fy, the medio-lateral shear force; My, the extension moment of the thigh; Fz, the antero-posterior shear force; and Mz, the abductor moment of the thigh. The resultant knee force, in all subjects, increases when lifted load increases. A similar increase in the resultant moment at the knee joint was found. These pic values were calculated for a knee angle of 108. The medio-lateral shear force (Fy) was not affected by the load. However, during the middle phase of the exercise, the mtero-posterior shear force increased from 0.72 to 0. 88 times body weight when lifted mass increased from 1 to 1.20 times body weight. For the compressive component (Fx), no clear variation as a function of load was found in this study in all subjects. Even for the heaviest load (120% body weight), no increase in forces and moments was recorded from the first to the last repetition of one set. CONCLUSION The results of this study demonstrated that mechanical stress acting on knee joint in half-squat exercise increased with lifted barbell. For knee force components, load was found to affect only the antero-posterior shear force. The medio-lateral shear force was independent of this variable. Force and moment values were affected by REFERENCES Poumarat, G., Dabonneville, M., Chandezon, R., & Roddier, P. (1989). Les squats: Forces induites sur I'articulation du genou et sur L5 S 1 en fonction des postures adoptCes. CinCsiologie, 69-74. Trafimow, J.H., Schipplein, O.D., Novak, G.H.,& Andersson, G.B.J. (1993). The effects ofquadriceps fatigue on the technique of lifting. Spine, 18,364-367

Contamination by metallic elements released from joint prostheses

When a metallic implant is in contact with human tissues, the organism reacts and a corrosion process starts. Consequently, we might observe liberation of metallic debris and wear. Our purpose is to measure the contamination and the migration of these metallic elements in the surrounding tissues of the implant. Two types of samples have been studied. First type is sample taken on post-mortem tissues around prostheses to study contamination gradients. Second type is sample taken on pathologic joints on periprosthetic capsular tissues in surgical conditions. These allow estimating contamination degree. The experiments were made on a Van de Graaff accelerator located at CERI (Centre d'Etude et de Recherche par Irradiation, Orl\'{e}ans, France). We measure elemental concentrations resulting from the contamination of the surface of each sample. Results are analysed in function of the pathology and the type of implants. According to the pathology and the location of the sampling, these measurements show a very heterogeneous contamination by metallic elements under particles and/or ionic species which can migrate through soft tissues by various mechanism

Association between adolescent idiopathic scoliosis prevalence and age at menarche in different geographic latitudes

BACKGROUND: Age at menarche is considered a reliable prognostic factor for idiopathic scoliosis and varies in different geographic latitudes. Adolescent idiopathic scoliosis prevalence has also been reported to be different in various latitudes and demonstrates higher values in northern countries. A study on epidemiological reports from the literature was conducted to investigate a possible association between prevalence of adolescent idiopathic scoliosis and age at menarche among normal girls in various geographic latitudes. An attempt is also made to implicate a possible role of melatonin in the above association. MATERIAL-METHODS: 20 peer-reviewed published papers reporting adolescent idiopathic scoliosis prevalence and 33 peer-reviewed papers reporting age at menarche in normal girls from most geographic areas of the northern hemisphere were retrieved from the literature. The geographic latitude of each centre where a particular study was originated was documented. The statistical analysis included regression of the adolescent idiopathic scoliosis prevalence and age at menarche by latitude. RESULTS: The regression of prevalence of adolescent idiopathic scoliosis and age at menarche by latitude is statistically significant (p < 0.001) and are following a parallel declining course of their regression curves, especially in latitudes northern than 25 degrees. CONCLUSION: Late age at menarche is parallel with higher prevalence of adolescent idiopathic scoliosis. Pubarche appears later in girls that live in northern latitudes and thus prolongs the period of spine vulnerability while other pre-existing or aetiological factors are contributing to the development of adolescent idiopathic scoliosis. A possible role of geography in the pathogenesis of idiopathic scoliosis is discussed, as it appears that latitude which differentiates the sunlight influences melatonin secretion and modifies age at menarche, which is associated to the prevalence of idiopathic scoliosis

Secondary displacement of distal radius fractures treated by bridging external fixation.

Loss of reduction remains an important problem after treatment of distal radius fractures, whatever the type of bone fixation. We assessed retrospectively the rate of secondary displacement after external fixation of distal radius fractures in order to identify possible risk factors for instability. We reviewed the pre-operative and serial post-operative radiographs of a retrospective series of 35 distal radius fractures treated by bridging external fixation. When classified according to the Société Française d'Orthopédie et Traumatologie (SOFCOT) criteria, the rate of secondary displacement was 48.5%. At final follow up, the reduction was anatomical in 12% and acceptable in 83%. There was malunion in 5%. The loss of reduction concerned primarily the distal radius palmar tilt and was moderate. No correlation was found with age, gender, type of fracture, degree of initial displacement, associated ulnar fracture, or seniority of the treating surgeon.JOURNAL ARTICLESCOPUS: ar.jinfo:eu-repo/semantics/publishe