Abstract: CONTEXT: There is limited information about the effects of increasing load while squatting. OBJECTIVE: To quantify tibiofemoral joint kinetics during squatting with variable loads. SETTING: Research laboratory. PARTICIPANTS: 20 male students. INTERVENTION: Tibiofemoral joint kinetics and electromyographic (EMG) activity of four involved muscles were determined by recording the half squat with variable external loads. MAIN OUTCOME MEASURES: Tibiofemoral joint force and external moment components and EMG activity of four involved muscles. RESULTS: Throughout the exercise, a posterior direction for the antero-posterior shear force and a net extension for the external moment were observed. They increased with knee flexion reaching peak force of 29% of the subject body weight (BW) and moment of 88Nm (without external load). All force and moment components and muscle activities increased as the external load increased. CONCLUSION: These findings suggest that half squat may be safe to use for quadriceps strengthening with very low potential loading on the anterior cruciate ligament (ACL). Our data can help clinicians choose the appropriate external load.

Abstract: PURPOSE: To investigate the gross anatomy of the distal portion of the quadriceps, and to compare the relative contributions of the vastus medialis oblique (VMO) and vastus lateralis (VL) during dynamic weight-bearing conditions. METHODS: Dissection was carried out on 10 cadavers by a longitudinal incision from the anterior superior iliac spine to the patella and completed with upper and lower transverse cuts to reinvestigate the gross anatomy and innervation patterns of the quadriceps femoris. A biomechanical test of knee kinematics was conducted on 10 healthy male volunteers. Maximal isometric force, squat jump, and drop movement jump exercises were performed on a force plate and filmed using a Saga-3 3D system, and surface EMG activity was recorded for the VMO and the VL. RESULTS: The oblique fibers of the vastus medialis (VM) are not only attached to the medial border of the patella, but they also have a small region of direct continuity with the patellar tendon. Furthermore, VMO fibers in the middle and proximal thirds of the thigh attached to vastus intermedius, whereas distally, the fibers were independent. Both parts of the VM (proximal and distal) had independent motor points. During jumping exercises, the VMO and VL were activated in a coordinated manner in a squat jump using both legs. However, in a single-leg squat jump (which challenged the stability of the knee joint more acutely), VMO activation was higher during landing. CONCLUSION: VMO activity was pronounced during the weight-bearing conditions, with increased medial and lateral knee movements. This suggests that the VM should not be considered simply as a knee extensor or as a muscle whose main role is to maintain normal patellar tracking.

Abstract: OBJECTIVE: To provide an electrophysiological and functional description of the vastus medialis (VM) and contrast it to an anatomical description. METHODS: Motor points of all superficial portions of the quadriceps were identified on the dominant side of 8 human subjects and electrically stimulated to achieve a light contraction to trace and measure the orientation of the fibers. Electromyography of the VM was then recorded over 2 motor points during isometric and isokinetic maximum knee extensions. An independent laboratory dissected 39 cadaveric specimens focusing on fiber orientations and distal insertions of the VM. RESULTS: Results revealed 5 motor points for the quadriceps: 1 point for the vastus lateralis, 1 point for the rectus femoris (RF), and 3 points for the VM. The 3 VM motor points suggest 3 separate groups of fibers: proximal (pf), median (mf), distal (df). Fiber orientations ranged from 45 degrees for VMpfs to 55 degrees for VMdfs. Motor point stimulation and anatomical dissection clearly showed that the VMpfs and VMmfs were inserted on a tendon common to the RF, whereas VMdfs were attached directly to the medial aspect of the patella. Furthermore, the VMpfs were more active (P < .05) than VMdfs during maximum knee extensions. CONCLUSION: The anatomy, motor points, and electromyography clearly support an important distinction between the VMpfs and VMdfs. The role of the VMpfs would be one of assisting the RF in knee extension, whereas the VMdfs would track the patella medially without participating in knee extension. Because of these anatomical and functional differences, the VMpfs and VMdfs should be addressed very differently during quadriceps rehabilitation in patellofemoral dysfunctions.

Abstract: The purpose of the present study was to compare vertical jump performance after 2 different fatigue protocols. In the first protocol, subjects performed consecutive sets of 10 repetitions of stretch-shortening cycle (SSC) contractions. In the second protocol, successive sets of 10 repetitions of isometric contractions were performed for 10 s with the knee at 90 degrees of flexion. The exercises were stopped when the subjects failed to reach 50% of their maximum voluntary isometric contractions. Maximal isometric force and maximal concentric power were assessed by performing supine leg presses, squat jumps, and drop jumps. Surface EMG was used to determine changes in muscle activation before and after fatigue. In both groups, the fatigue exercises reduced voluntary isometric force, maximal concentric power, and drop jump performance. Kinematic data showed a decrease in knee muscle-tendon stiffness accompanied by a lengthened ground contact time. EMG analysis showed that the squat and drop jumps were performed similarly before and after the fatigue exercise for both groups. Although it was expected that the stiffness would decrease more after SSC than after isometric fatigue (as a result of a greater alteration of the reflex sensitivity SSC), our results showed that both protocols had a similar effect on knee muscle stiffness during jumping exercises. Both fatigue protocols induced muscle fatigue, and the decrease in jump performance was linked to a decrease in the strength and stiffness of the knee extensor muscles.

Abstract: PURPOSE: The purpose of this study was to compare the effects of jump training as a complement to weight training on jump performance and muscle strategy during the squat and countermovement jump. METHOD: Twenty-two male handball players, between the ages of 17 and 24, and in good health, were randomly divided into three groups. Two were trained groups, weight training (WTG) and jump training combined with weight training (CTG), and one was a control group (CG). Maximal isometric force and maximal concentric power were assessed by a supine leg press, squat jump (SJ), counter movement jump (CMJ), and surface EMG was used to determine changes in muscle adaptation before and after the training period. RESULTS: After 6-wk training programs, the two training groups increased maximal isometric force, maximal concentric power, and squat jump performance. However, only combined training presented a significant increase in height jump performance during the countermovement jump (P < 0.05). EMG analysis (as interpreted through the root mean square values) showed that the SJ was performed similarly before and after the training period for the two training groups. However, during the CMJ, only the CTG group adopted a new technique manifested by a short transition phase together with an increase in knee joint stiffness and knee extensor muscle activation and rectus femoris ratio. CONCLUSION: It was suggested that the central activities in knee joint during the transition phase, in conjunction with intrinsic muscle contractile properties, play a major role in the regulation of performance during a CMJ. Furthermore, our study suggests that a change in maximal strength and/or explosive strength does not necessarily cause changes in combined movement such as the stretch shortening cycle.

Abstract: The aim of this study was to compare the effects of plyometric training performed with rapid or slow stretch contraction on jump performance and muscle properties. Thirty males between the ages of 19 and 22 volunteered for the 8-week experiment. Subjects were divided into the following three groups: training group 1 (TG1), training group 2 (TG2), and control group (CG). Each of the two experimental groups underwent a unique training regimen. For the first group (TG1, n = 12): from a standing position the subject flexed his knees to a 90 degrees angle with velocity standardized and controlled at 0.4 m/s and immediately performed a leg extension as quickly as possible. For the second group (TG2, n = 12): from a standing position, the subject flexed his knees to a 90 degrees angle with velocity standardized at 0.2 m/s and then performed a leg extension as quickly as possible. Each exercise consisted of six sets of ten repetitions with a barbell on the shoulders at 70 % of the maximal isometric force (1 RM). The 70 % load was modified at two-week intervals by evaluating a new 1 RM. Exercises were performed four times a week over the eight-week period. The third group (CG, n = 6), served as the control group. Maximal isometric force (MVC), maximal concentric force, squat jump (SJ) and counter movement jump (CMJ) exercises were performed before and after the training program. Subjects were filmed (100 Hz) and each jump was divided into three phases: eccentric phase (ECC), transition phase (TR) and concentric phase (CON). Surface EMG was used to determine the changes in the electromyographic (EMG) activity before and after the training program. There was an increase in leg extension force, velocity and electrical activity for SJ and CMJ for the two training groups (p < 0.05). However, TG1 showed a significant advantage in CMJ performance as well as a significant decrease in TR compared to the TG2 (p < 0.05). The results of this study show that when plyometric training is performed with rapid stretch contraction the CMJ jump height increases and the TR decreases.

Abstract: PURPOSE OF THE STUDY: Bone grafts and bone substitutes must be biocompatible osteoconductors with satisfactory mechanical properties similar to native bone. When the bone treatment is conducted under specific conditions, the elasticity module under infra-maximal loading can be optimized to achieve reproducible values. The purpose of this work was to determine the effect of the cleaning and sterilization process using Osteopure on the biomechanical properties of trabecular bone harvested from human femoral heads. MATERIAL AND METHOD: Seventy trabecular bone samples were tested: group 1F (fresh samples); group 1N (after application of Osteopure cleaning); group 1S (after Osteopure cleaning and sterilization). Non-destructive and destructive tests (group 1D) were performed. Two fresh femoral heads were used as controls for the destructive test (group 2). The first non-destructive test was applied directly after section (group 1F). Other samples were then purified with Osteopure treatment and a second non-destructive test was conducted (group 1N). A third non-destructive test was conducted after sterilization with 25 kgray radiation (group 1S). Treatments 1 and 2 were performed by OST Developpement SA (Clermont-Ferrand). Finally a destruction test was applied along the directional axis (group 1D). For the 31 samples in group 2 (control) the destructive test was applied along the directional axis immediately after section. Compression tests were performed at a deformation speed of 3 mm/min for 0.3% deformation. RESULTS: The Young module did not exhibit any significant difference between the three steps of the testing in the three orthogonal directions. The Young module was not significantly different between group 1F and group 2 (controls). Maximal force of compression was significantly different (P<0.01). There was a linear relationship between maximal force at rupture and the Young module obtained during destructive tests, for groups 1D and 2 respectively. The compression curves obtained from sterilized samples (group 1D) were not significantly different from those observed for fresh trabecular bone in group 2 (controls). DISCUSSION: The Young module values measured from 70-673 MPa. For non-destructive tests, the module values were to the order of 64% of those obtained for destructive tests. Decreased maximal force of rupture observed for treated samples in comparison with fresh samples can be explained by the extraction of most of the lipids. CONCLUSION: The Osteopure method does not alter stiffness of bone allografts. The elasticity module observed in treated bones is close to that observed in fresh bones. Mechanical resistance to compression is however only half the force of compression observed in the hip joint for daily activities. The linear relationship between the elasticity mode and loading required for rupture is not affected by treatment with Osteopure. The advantages related to elimination of prions or viral contamination appear by far to be more important than the minor changes observed in the mechanical characteristics of allografts.

Abstract: INTRODUCTION: Pelvic laparoscopic surgery offers multiple advantages for patients, but requires uncomfortable, non-ergonomic positions for the surgeon. Only a remote operator (Robot "slave" reproducing the surgeon's movements performed on a "master" console situated away from the patient), like Da-Vinci or Zeus (Intuitive Surgical) can improve the laparoscopic surgeon's working conditions. The objective of this study, based on an ergonomic analysis and recording of a laparoscopic surgeon's movements, was to define the specifications for the manufacture of an operating seat with armrests, based on the surgeon's position using a remote operator. MATERIAL AND METHODS: Movements of the centre of pressure and upper limbs of 12 urologists and gynaecologists with various levels of experience, were recorded using a force platform and a SAGA 3 RT movement analysis system (Biogesta), during 4 exercises performed on a pelvi-trainer, with the surgeon positioned to the left (introduction of a needle, unravelling of a cord, dissection, suture). Ergonomic analysis of the laparoscopic surgeon's movements was based on video recordings of a surgeon under real operating conditions. The specifications were defined from all of these data. RESULTS AND DISCUSSION: The small amplitude of movements of the surgeon 's centre of pressure (< 45 cm2) confirmed that surgeons can be seated during laparoscopy. Recordings of the upper defined the elbow working zones and the need for 3D mobile armrests. Ergonomic analysis of posture defined the characteristics of the prototype. On the basis of these specifications, a prototype operating seat was developed. This prototype now needs to be validated or invalidated clinically.

Abstract: Antenatal gymnastics is a form of non-pharmacological childbirth preparation methods. It helps maintain rachidian statics and to relieve painful syndromes (joints, lumbar pains) during pregnancy. It also helps correct gravidic problems (leg cramps, back ache, weight increase, etc.). It is both a physical and psychological training method in accordance with the natural mechanisms of childbirth, implying personal involvement on the part of the parturient. Fifty (50) pregnant women of Benin (apart from pathological pregnancies) divided into two groups of 25 subjects (experimental group) and 25 subjects (control group) voluntarily took part in the study after having given their written assent. Each involved subject is paired with a counterpart of control following the same criteria: age of the gestante, parity, characteristic of the pelvis. Subjects aged from 17 to 42 trained twice a week with a minimum of 24 hours rest between two sessions; the training period intensity of exercise is limited to 60% of the maximum heart frequency and each training session lasts 45 min. The results show a lower number of caesareans and a significant lower number of untorn perineas in the experimental group. Apgar scores are also statistically higher in the children of trained women. This study confirms that sedentary pregnant women without any medical counter-indications (repetitive miscarriages, premature births, placenta praevia, cervical gaping, cardiac diseases, hypertension, narrow pelvis) can participate in antenatal gymnastics at a moderated rhythm, for their own benefit and that of their babies. Muscular force improvement (quality of the abdominal pushing), psychological control (absence of stress and panic), and good body form, can be noticed in trained mothers. However, abnormal presentation of baby, fetal suffering and the inherent characteristics of the pelvis (narrow) are factors requiring a caesarean. On the whole, antenatal gymnastics is an effective non-pharmacological means to avoid complications in childbirth. This method might be one of the solutions which could benefit pregnant women in Africa, considering its low cost compared to the exorbitant cost of medicines and hospitalisation.

Abstract: The motion of thoracic and lumbar spine segments has been analysed by mean of the skin landmarks method on 14 volunteers (7 males, 7 females). Results demonstrate that: There is no significant difference between male and female. There is either facilitation, or limitation of the motion of the characteristic landmarks of the spinal segments during trunk motion in perpendicular planes. The mobility of the spinal segments is associated with pelvic girdle motion in order to obtain the planed amplitude, and varies with hips abduction. The analysis of the precise mechanisms of relaxing or stretching of the pelvi-spinal musculo-ligamentous structures constitutes a large field of investigation that necessitates the study of other pelvic limbs postures and needs the use of robotic techniques.

Abstract: The purpose of this study was to compare the effects of two protocols of electrical stimulation combined with voluntary contractions on the recovery of thigh muscles after anterior cruciate ligament (ACL) surgery. Ten sportsmen with a mean age of 26 yrs were randomly assigned into two groups: a 80 Hz stimulated group (5 patients) and a 20 Hz stimulated group (5 patients). All patients received electrical stimulation of the quadriceps femoris, five days a week, for 12 weeks, and had a standard program of voluntary contractions. Muscle and fat volumes of the thigh were assessed using MRI before surgery and after 12 weeks of rehabilitation. Quadriceps and hamstring muscle strength were evaluated by isokinetic measurements. Twelve weeks after surgery, the quadriceps peak torque deficit in the operated limb with respect to the non operated limb at 180 degrees /s and 240 degrees /s was significantly (p < 0.05) less in the 20 Hz group than in the 80 Hz group. This difference was not confirmed when comparing the pre-surgery quadriceps peak torque of the operated limb with the post-surgery one. Subcutaneous fat volume was increased for the two groups at the post-surgery test. This increase was significantly (p < 0.05) greater for the 80 Hz group. Thigh muscle volume deficit was not significantly different between the two groups.

Abstract: INTRODUCTION: The evaluation of the bite forces coupled with EMG activity of masseter muscles allows to point out temporo-mandibular joint disorders. The intense practice of sports induces stress which may affect the mandibular statics, due to an hyperfunction of the elevator masticatory muscles, especially the masseter muscles. This concept has led us to compare the maximum isometric bite forces of sedentary and physically trained subjects. MATERIAL AND METHODS: The aim of this experimentation is to study the maximum isometric bite forces of the premolars, with a force transducer, for two groups of physically trained and sedentary volunteers (25 subjects), with distinction between male and female subjects. Subjects with normal denture and no temporo-mandibular joint disorder were retained. EMG and force recording were synchronized and recorded during 10 seconds of maximal contraction. RESULTS: The male subjects developed a maximal bite-force significantly higher (p < 0.05) compared to the female subjects. There is no significant difference between subjects practising a sport (at least 6 hours a week) and sedentary ones. The evolution of force during the contraction is different between sexes. EMG activity allowed to control that subjects developed a maximal force and an increase in muscular fatigability of physically active females compared to sedentary ones was noticed. DISCUSSION: The difference of maximal force between men and women is similar to the one found for the locomotor muscles. The analysis of the evolution of the force according to the contraction duration, might be linked to a different distribution of muscular fibers according to the sex. The practice of a sport might increase the fatigability of the masseter muscles and might be a factor inducing a muscular imbalance of the mandibular posture. But the relatively low number of subjects and the absence of well defined distinctions between different kinds of sport limit our conclusions.

Abstract: The influence of various modes of carrying a load of 16 kg (15.69 DaN) on the static positioning of the pelvic girdle and the thoracic and lumbar segments of the spine was examined in seven male subjects. The displacement of cutaneous markers attached to easily palpable skeletal landmarks was recorded using 4 CCD cameras; the data acquired were analysed using an optoelectronic technique (SAGA3). The subjects stood upright on an AMTI biomechanical force platform, from which the ground reaction forces enabled displacements of the centre of gravity axis and thus the moment of the mass carried to be determined. The modes of load carriage examined were: 1) in a case in the left hand; 2) in a case in the right hand; 3) equally in two cases; 4) on the head; 5) in a rucksack; and 6) in an anterior bag. The results showed displacements of the pelvic girdle, the caudal and cranial lumbar segments, and the caudal and cranial thoracic segments in the three orthogonal planes (sagittal, frontal and transverse). The influence of the moment created by the load was seen in the statokinesigrams. The use of external markers using an optoelectronic technique, in association with the ground reaction forces, enables the mode of load carriage to be determined. The results show that the influence of the moment exerted by the mode of load carriage on the gravity axis has important ergonomic consequences.

Abstract: The purpose of this study was to find if the performance of the vertical jump is improved by the result of increasing the force, velocity, and muscle adaptation(s). For the experiment, there were four groups (Gr): three groups did the training programs and the fourth group was the control group (CG). In order to establish improvements in force and velocity, the groups performed three variations using eccentric (Ecc) and concentric (Con) movement. Finally, the leg presses, squat jumps (SJ) and countermovement jumps (CJ) were used to determine the changes in the muscle adaptations before and after the training program. For measuring the force, four force transducers were used. In determining the velocity, a displacement transducer was used. A surface EMG was used to measure the muscle activations during all of the tests that were performed. After eight weeks of training, Gr 1 and Gr 2 improved the isometric force and the power during the Con. movement for the leg press. For the SJ, Gr. 1 and 2 increased their height, muscle activity, force, and power, but only group one improved the velocity. However, group three improved the isometric force and power for the leg presses, the squat jump and the countermovement jump. For both of the jumps, they also increased velocity, muscle activity and height. There were no changes observed for group four. Although the three combinations of Ecc/Con movements existed during the training program, the force, velocity and muscle adaptations increased, but not all of the improvements were of the same degree.

Abstract: This work describes a way of measuring the forces acting on the shoulders when subjects carry a backpack. A frame pack was carried by 12 male subjects: 4 hikers, 4 occasional hikers, and 4 novices. They walked for 30 minutes on a 5% inclined treadmill at 3.6 km/h to simulate moderate hiking. The load was carried at T9 and was increased (10, 15, and 20 kg) after 1, 20, and 25 minutes. The data from force transducers placed on the shoulder straps were collected for 30 seconds at 100 Hz. Shoulder strain appeared to be the limiting factor in load carriage. The optimal carrying method depends on the person, but it has been shown that decreasing stride length and wearing appropriate footwear reduces the strain on the shoulders.

Abstract: In order to assess the effect of recovery on power and blood lactate, 10 males performed 10 sets (S1 to S10) of 6 repetitions of bench press at 70% of their maximal strength, with 1 (Prot1), 3 (Prot3) or 5 (Prot5) min rest between sets. From the measurements of force and displacement of the bar, mean power during each repetition (MPR) and set (MPS), were calculated. Blood lactate was evaluated before and immediately after each set. No significant variations in power or blood lactate occurred during prot3 and prot5. From S4 to S10, significantly lower MPS (27% decrease) and higher blood lactate (7.6 +/- 2.0 mmol/l) were demonstrated in prot1 vs prot3 or prot5. In spite of this, MPR in protl were significantly lower for repetitions 4, 5 and 6 only: MPR of repetitions 1, 2 and 3 were similar in the 3 protocols. During prot1 only, power decrease was related to lactate accumulation for all subjects (0.64 < or = r < or = 0.99, p < or = 0.05). These results indicate that although muscular power and blood lactate were both affected by the recovery interval, acidosis was not the direct cause of fatigue during the 1 min rest condition. The concomitant effects of lactate accumulation and insufficient time for a complete resynthesis may have resulted in a diminution of PCr stores, leading to power decrements.

Abstract: The development of new leisure activities such as walking has spread the use of the backpack as a means of carrying loads. The aim of this work was to present a way of defining the movements imposed on the trunk by this type of load carrying. A 20 kg load situated at the thoracic level (T9) of the trunk, was placed in a backpack (2.5 kg). The 12 subjects were average mountain guides of Auvergne region, intermediate level and complete beginners. External markers were glued to the projecting contours of the spinous processes of the C7, T7, T12, L3 and S1 vertebrae, the shin and the external occipital tuberosity (EOT). Using a Vicon 140 3-D system we measured the effective mobility of the different spinal segments in the sagittal plane during one step. For every subject, we noticed a significant decrease of the effective inter-segmental mobility (EISM) between S1-L3-T12 (p < .01) while backpacking a 22.5 kg load. A decrease of EISM also appeared at the next level between L3-T12-T7 (p < .05). An increase of the EISM between T7-C7-EOT was noted (p < .05). We supposed that strength loss of the back muscles and/or angular oscillations of the trunk could be a common cause of symptoms during backpacking. The subjects using this type of load carrying have to adopt an adequate position of the lumbar, dorsal and cervical vertebrae.

Abstract: The analysis of the displacement of the pelvic girdle, during movements of the trunk in the anatomical orthogonal plans, was carried out by the technique of the cutaneous markers on two series of 7 male subjects and 7 female. The photographs made it possible to objectify angular displacements of reliable singular points and to observe that the abduction of hips determines, according to movements carried out, either a facilitation, or a limitation of displacements observed similar in the two series. The precise mechanism of these variations will have to be analyzed by later studies.

Abstract: The motion of the thoracic and lumbar spine segments was analysed by mean of the skin landmarks method in 14 volunteers (7 males, 7 females). The results demonstrated that there was no significant difference between men and women and there was either facilitation or limitation of the motion of the characteristic landmarks of spinal segments during trunk motion in perpendicular planes. The mobility of spinal segments was associated with pelvic girdle motion in order to obtain the planned amplitude, and varied with hip joint abduction. The analysis of the precise mechanisms of relaxing or stretching of the pelvivertebral musculo-ligamentous structures constitutes a large field of investigation that necessitates the study of other lower limb postures and the use of robotic techniques.

Abstract: It has been experimentally proven many times that the mental rehearsal of an activity not only improves motor performance but also has vegetative effects whose magnitude is correlated with the amount of imagined effort. These beneficial effects of mental imagery have been explained in terms of central programming structures capable of anticipating the metabolic demands of the task. Twenty-four subjects were asked to actually perform and also imagine an isometric contraction of the forearm under various goal conditions: a task-involving goal (8 subjects), an ego-involving goal (8 subjects), and no goal (8 subjects). During the contractions, electromyographic potential and heart rate were measured. Afterwards, the subjects were asked to indicate the amount of effort expended under different feedback conditions. The results showed no trace of electromyographic activity during the imagined contractions when the lack of movement was controlled using a force sensor. On the other hand, a significantly faster in heart rate was observed with a task- or ego-involving goal than with no goal, during both actual and imagined contraction. Similarly, as predicted, subjects said they applied less effort in the positive feedback condition, and more effort in the negative feedback condition with an ego-involving goal. The results are discussed in the light of goal theories, while regarding goals not only as serving to anticipate metabolic expenditures but also as promoting a self-image of competence, particularly in threatening, ego-involving situations.

Abstract: The overall movement of the trunk is made up of two components, namely the movements of the pelvic girdle and the vertebrae. In the frontal plane, the amplitude of the pelvic movements appears to be relatively limited compared to the vertebral column whereas the pelvis makes the major contribution to the total rotational movement in the axial plane.

Abstract: Physiological displacements of the trunk are the addition of these of the pelvic girdle and thoracic and lumbar spine segments. For a long time (3), this conjunction had been noticed but without numbered precisions. The purpose of this communication is to appreciate quantitatively, from a series of 16 subjects, the respective share of each components during lateral bending movements in the frontal plan and movements of rotation in the transverse plan. It results from this work that the pelvic girdle presents as reduced amplitude (4 degrees) in lateral bending on the other hand, displacement predominate to the level of thoracic spine (50 degrees). In rotation pelvic displacements are very important (30 degrees), while the spine so thoracic that lumbar has a weak participation (inferior to 5 degrees). Moderated abduction of hips increases by significant manner the motility of the pelvic girdle.

Abstract: OBJECTIVE: Patellofemoral dysfunctions are associated with problems in the knee extensor mechanism, including specific atrophy of the distal fibers of the vastus medialis, also known as the vastus medialis oblique. Rehabilitation of the vastus medialis in patellofemoral dysfunctions has been shown to be ineffective. This limitation had stemmed from the lack of understanding of the vastus medialis' specific functions. The purpose of this project was to investigate the role of four portions of the quadriceps femoris using surface electrical stimulation. DESIGN AND SETTING: Single-group and single-test (repeated measures on muscle portions) design. All tests were performed in a university laboratory. SUBJECTS: Eight healthy university students received electrical stimulation. MEASUREMENTS: Subjects were seated with the knee at 90 degrees of flexion and the leg pushing against a strain gauge that measured the force exerted. Electrical stimulation was administered on the vastus lateralis, rectus femoris, and proximal and distal fibers of the vastus medialis to quantify the torque produced by the knee extensors. The electrical stimulation maximum intensity was adjusted to achieve specific fiber recruitment and the highest isolated contraction. Force was measured with a strain gauge placed on the anterior aspect of the distal end of the tibia. Force was recorded in two levels: force applied before the onset of electrical stimulation and force produced by the stimulation. Subjects also performed two maximum isometric knee extensions before and after electrical stimulation for normalization. RESULTS: Electrical stimulation elicited mean torques of 6.31 per thousand, 14.0 per thousand, 20.2 per thousand, and 28.0 per thousand of maximum isometric voluntary contractions of the distal and proximal fibers of the vastus medialis, the vastus lateralis, and rectus femoris, respectively. CONCLUSIONS: The distal fibers of the vastus medialis do not contribute significantly to knee extension.

Abstract: The global amplitude of the movements of the trunk is the resultant of the sum of two components: the movements of the pelvic girdle and those of the vertebral segments. In order to assess the precise position of the pelvis in kinetics, we endeavored by the use of skin markers to determine whether reliable measurement points existed. The experiment showed that a line drawn from the median sacral crest at the level of S1 to the highest point of the iliac crest appeared relevant and practical for assessment of the position of the pelvic girdle in the sagittal plane.

Abstract: Comparative study of static curves of the thoracic and lumbar spine in men and women has been realized under constraints of compression by weightlifting and elongation by exercise to parallel bars. In two athletic practices, curves decrease their arrow, ending to a straighter and more rigid column. This behavior expresses muscular actions. The greatest amplitude of displacement, observed in female series, shows lesser muscular forces in connection with a poor practice of exercises of body building.

Abstract: Trained users of Rhythmic and Athletic Gymnastic, present kinetic spinal vast extents. Analysis, with pasted cutaneous markers, shows that, according to the codified movement, various segments of the vertebral column are requested and realized important displacements. Nevertheless, to have an homogeneous attitude, some subjects request more either lumbar or thoracic segments, of both. To prevent frequent spinal pain, it is important to realize a preliminary subject selection using their total spine and to improve protection by adapted gymnastic.

Abstract: Optical techniques using single wavelength lasers allow precise study of the superficial displacements of deeper anatomical structures through direct mechanical pull. Two techniques have been used in this study: 1. Double exposure speckle photography. Since 1980 the relationship between the surface displacements and minimal traction applied to the transverse processes of the spine, either unilateral or bilateral, was studied in an attempt to simulate muscular action exerted at this level. 2. Computerised speckle interferometry. This allowed analysis of the deformations between the lumbar vertebrae under vertical compression, shear or torsion outside the usual anatomical planes. This preliminary study outlines the mechanical behaviour and the plasticity of the vertebral structures but has been performed on only a few anatomical specimens thus not allowing statistical analysis. This would require a larger series.

Abstract: Finite element modelling of the human lumbar vertebral column employs data-processing procedures for study of the linear and nonlinear elasticity of materials such as are currently used in mechanics or in civil engineering. Thanks to developments in computer science, requiring a close collaboration between doctors and engineers, we put forward in this preliminary study a linear computerised model of the lumbar column comprising 4824 meshes and 6813 nodes. By reducing the simplificatory hypotheses and integrating new parameters, this model as developed is capable of important clinical applications in surgery and ergonomics.

Abstract: The aim of this work is to determine the effect of low frequency current (L) versus medium frequency current (M) in order to generate a different force level on soleus and gastrocnemius muscles. The experiment was conducted on 10 healthy, male volunteer subjects aged from 19 to 21 who provided informed consent to participate in the experiment. None of the subjects had experienced electrostimulation (ES) procedures before. The subjects were seated with vertical legs and horizontal thighs. Isometric force of the gastrocnemius and soleus muscles was measured using a strain gage dynamometer (100 daN). The transducer was adjusted on the knee, along the vertical axis of the leg. For the conditions of ES, a bi-phasic, symmetrical square wave signal was applied at each of five low frequencies: 20, 40, 60, 80 and 100 Hz and at each of six medium frequencies (2222 Hz) modulated or not, to yield 20, 40, 60, 80, 100 bursts of pulses. Maximum voluntary contraction (MVC) was also recorded. The phase duration was constant throughout 180 microseconds. The current level was set individually for each subject at the maximum that could be tolerated and applied during 10 s. Each contractile condition was randomly chosen. The forces produced by the different regimen of ES used are significantly different (P < 0.001). For each type of stimulation we got tetanic contractions. After an initial ramp, a nearly flat curve corresponding to tetanus was reached. For a 60 hz low frequency current, the force production reached 76% of MVC for a mean intensity of 58 mA, corresponding to a charge of 1253 microC.(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract: Opto-electronic systems utilising measurement of displacement of skin markers allows study of movement in the living subject. The authors have used this method in a kinematic study of the thoracic and lumbar spine measuring the displacement of skin markers placed over the spinous processes. It was possible to approach the physiological state of these complex movements once the apparatus had been calibrated to the correct level, and the error margins minimised. Repeated measurements confirmed the reliability of this method even if movement of the skin with respect to the bony reference points introduced some margin of error. Three dimensional displacement of the vertebrae were measured during voluntary movements of the spine demonstrating the complex geometry. Since opto-electronics are non-invasive they constitute an important advance in the study of the kinematics of the spine.

Abstract: The use of cutaneous markers as an accurate method of measuring spine motion was studied in five cadaveric spine samples and two live subjects. The markers were placed on the skin over the spinous processes, a particularly suitable site in thin subjects for determining the displacement of the underlying skeletal segments because the deep layer of the skin is in adherence with their fibrous surrounding sheath. Fairly close correlations were obtained in the sagittal and frontal planes between the two sets of measurements. However in the transversal plane the technique is unreliable because of tightening of the skin.

Abstract: OBJECTIVE: The aim of this article is to review the basic research concerned with force and fatigue induced by electrical stimulation. Specific reports on human and animal models are covered. Articles dealing with specific afflictions of the neuromuscular system are also reviewed. DATA SOURCES: The main sources for article retrieval were the classic bibliographic data bases in the exercise, rehabilitation and physiological science fields such as Index Medicus and Medline. Indexing terms used included human and animal in conjunction with electrical stimulation, force and fatigue. Language and time constraints limited the search to French and English texts of this century. Proceedings of different electrical stimulation conferences were also covered. STUDY SELECTION: All authors had to approve the selection of the articles to be included in this review. The narrow scope of the review made it possible to include most of the articles investigated. Redundancy of information was the only rejection criterion. DATA EXTRACTION: Initially, the first author collated the articles and extracted the relevant data. This collation was then verified with respect to the original information and approved by all authors. DATA SYNTHESIS: Possible sites of the fatigue mechanisms may include the central nervous system, the peripheral nervous system, the neuromuscular junction, and the muscle excitation-contraction coupling. Even though not unanimous, data gathered from normal muscles seem to support that the major contributor to fatigue is the muscle fiber and not the nervous system or the neuromuscular junction. Other work involving paralyzed muscles suggest that electrically induced exercise alters the contractile properties of the muscle more specifically. CONCLUSIONS: It appears that muscle intracellular processes dominate the force decrease associated with muscular fatigue. Accordingly, when dealing with a problem involving loss of force and hyperfatigability, the metabolic aspects and muscle physiology should be prime considerations in choosing a therapeutic approach. The nervous and/or neuromuscular implications are, however, not to be discarded.

Abstract: The study compared the mechanical properties of human bone, fresh bovine bone and a new highly purified bone xenograft: T650 (Lubboc-Laddec). Destructive, compressive tests were performed to determine Young's modulus and ultimate strength, with a constant deformation rate of 0.025 mm min-1. The stress-strain curves obtained from all the non-human specimens especially the T650, did not differ significantly from those observed with human bone. Human and fresh bovine samples presented a significantly different Young's modulus. The T650 samples, depending upon their trabecular texture (dense or medium) also differed significantly from each other (132.9 +/- 52.3 versus 80.0 +/- 37.3 MPa, P < 0.05). Their moduli were similar to those of bovine and human cancellous bone, respectively (117.49 +/- 61.53 versus 77.36 +/- 54.96. P < 0.05). The ultimate strength of T650 dense (9.6 +/- 3.7 MPa) was similar to bovine (8.5 +/- 4.2 MPa) and human bone (8.78 +/- 5.2 MPa): the T650 medium (5.9 +/- 2.8 MPa) was significantly different from the other specimens.

Abstract: The study on motion of human thoracic and lumbar spine is difficult. To examine this point, technology will be divided in six class and each of them being benefits and disadvantages. Owing to ethics, authors agree with skin tapes allowing to know imperfectly freeness of motion without risks.

Abstract: Previous studies have considered the effects of the superimposition of electrical stimulation (ES) upon maximal voluntary contraction (MVC) under isometric conditions. This investigation considered these effects using isokinetic muscle action. Eleven males, non athletes, volunteered for the experiment. Isokinetic torque for extension of the right knee was measured by means of a Cybex 340 using two speeds of movement, 12 degrees/s and 30 degrees/s. Torque was measured at 5 degrees increments (from 100 degrees flexion to full extension) under conditions of MVC alone and MVC+ES. Stimulation was provided by means of a bi-phasic, symmetrical, square wave with a pulse width of 600 mu. Frequency of stimulation was either 30 Hz or 80 Hz. It was found that the pattern of torque production was unaffected by the application of ES. Peak torque values at both speeds were significantly lower when ES was applied at both frequencies compared to MVC alone. This inhibitory effect was found to extend throughout the middle range of movement. This tended to be more pronounced with the 80 Hz frequency. In general these findings were in agreement with those reported previously for isometric conditions. Possible explanations for these results include the inability of ES to recruit more motor units than MVC alone; the limitations of the subjects to tolerate a current of a sufficiently high intensity to elicit a stronger contraction, possibly due to lack of familiarization with these forms of muscle action; and the characteristics, especially pulse width, of the stimulating current.

Abstract: Under static loading during weight-lifting, the lumbosacral spine essentially exhibits horizontalisation of the base of the sacrum (superior plateau of S1). We have attempted to elicit the mechanism of this horizontalisation by means of radiographs. These do not demonstrate any movements of the sacroiliac joints or plasticity of the hip bones. However, a symmetrical rotation of the hip joints conditions a retroversion of the pelvic girdle which explains the horizontalisation of the upper sacral plateau. This fixation of the block of the pelvic girdle is under muscular control, so that this mechanism can be improved by appropriate training.

Abstract: Radiographies of lumbar spine at rest in standing position and upon a force of 100kg were undertaken in 19 young sportsmen. If comparison between two pictures demonstrated important modification in few subjects, statistical study shown only little variations. Clinical studies in weight lifters demonstrated effectively few lesions with a good training, it's possible to modifiate pelvic orientation and this pelvic support permits a optimal posture for the lumbar spine.