Jan Pieter Clarys

Anthropometric estimation of muscle mass in men.

Twelve male cadavers (aged 50-94 yr) were subjected to comprehensive anthropometry, dissection, and weighing of all skeletal muscle. Correlation coefficients of limb girths with total skeletal muscle mass (MM) were high: forearm r = 0.96, mid-thigh r = 0.94, calf r = 0.84, and midarm r = 0.82. These increased when limb girths were corrected (by subtracting pi times the skinfold thickness) to estimate muscle girth. For dimensional consistency, variables in the regression analyses included the product of stature and the square of each corrected girth. For the six unembalmed cadavers, this yielded a three-girth equation for MM (r2 = 0.93; SEE = 1.56 kg), which was then validated using data from the embalmed cadavers. It predicted MM with an SEE of 1.58 kg and r2 = 0.93. Because the values of these SEEs were similar, we pooled the subjects from the two groups to generate the final estimation equation: MM = STAT (0.0553CTG2 + 0.0987FG2 + 0.0331CCG2) - 2445 (SEE = 1.53 kg, r2 = 0.97), where STAT is stature (cm), CTG is thigh circumference corrected for the front thigh skinfold thickness (cm), FG is the uncorrected forearm circumference (cm), and CCG is the calf circumference corrected for the medial calf skinfold thickness (cm). Despite the limitations of the cadaver sample, the proposed equation appears to provide the best estimate of skeletal muscle mass to date, in that it is the only cadaver-validated equation and it gives values that are consistent with all known dissection data.

Science and Football II

Spend your time even for only few minutes to read a book. Reading a book will never reduce and waste your time to be useless. Reading, for some people become a need that is to do every day such as spending time for eating. Now, what about you? Do you like to read a book? Now, we will show you a new book enPDFd science and football vii that can be a new way to explore the knowledge. When reading this book, you can get one thing to always remember in every reading time, even step by step.

Electromyography and the study of sports movements: A review

Within electromyography (EMG), a particular specialty has been developed wherein the aim is to use EMG for the study of muscular function and co-ordination. This area of research is usually called kinesiological EMG. The general aims of kinesiological EMG are to analyse the function and co-ordination of muscles in different movements and postures, in healthy subjects as well as in the disabled, in skilled actions as well as during training, in humans as well as in animals, under laboratory conditions as well as during daily or vocational activities. This is often done by a combination of electromyographical and kinesiological or biomechanical measurement techniques. Because there are over 400 skeletal muscles in the human body and both irregular and complex involvement of the muscles may occur in neuromuscular diseases and in voluntary occupational or sports movements, it is impossible to sample all of the muscles of the entire body during the performance of complex motor skills. In addition, the measurement of kinesiological EMG in sport and specific field circumstances, such as the track and/or soccer field, the alpine ski slope, the swimming pool and the ice rink, demands a specific technological and methodological approach, adaptable to both the field and the sport circumstances. Sport movement techniques and skills, training approaches and methods, ergonomic verification of the human-machine interaction have, amongst others, a highly specialized muscular activity in common. The knowledge of such muscular action in all its aspects, its evaluation and its feedback should allow for the optimization of movement, of sports materials, of training possibilities and, in the end, of sports performance. Drawing conclusions from a review of the EMG research of 32 sports, covering over 100 different complex skills, including methodological approaches, is an impossible task. We have attempted to set standards concerning the EMG methodology at the beginning of this review. Electromyography and sports is a vast area and a complete review is impossible, as information will be found scattered in many different journals, including those on the sports sciences, ergonomics, biomechanics, applied physiology, in different congress proceedings, and so on. Consequently, many important aspects and possibly important publications may have been omitted from this review.

Human body composition: A review of adult dissection data

Although body composition analysis is popular, dissection data are sparse and sometimes difficult to access. Published data that include the weights of skin, adipose tissue, muscle, and bone, along with body weight, are reviewed. The 31 men and 20 women include 34 cadavers from three separate dissection studies in Brussels, 12 from 19th century reports, and 5 from the United States. The age range was 16–94y. Men differed from women in that they had less adipose tissue and more muscle in both absolute and relative terms. The body mass index (BMI) did not differ between the sexes, because lower weights of muscle and bone compensated for the greater adiposity in women. The relationship between the BMI and relative adiposity was significant, but the BMI explained only about one‐third of the variance in adiposity, indicating that in this sample it is a poor predictor of fatness. The composition of the fat‐free weight (FFW) and adipose tissue free weight (ATFW), though less variable than body weight, showed enough variability that the assumption of constancy of the fat‐free body required for densitometry and other indirect methods of fat estimation, could not be supported. In the few dissections that did fat extraction, essential on non‐adipose fat, varied from 4–14% of the FFW, thus undermining the concept of lean body weight. More dissection data are needed, especially in children and adolescents, and especially in conjunction with in vivo body composition methods to help in their validation. Am. J. Hum. Biol. 11:167–174, 1999.

Electromyography in sports and occupational settings: an update of its limits and possibilities

The detection of the electrical signal from human and animal muscle dates from long before L. Galvani who took credit for it. J. Swammerdam had already shown the Duke of Tuscany in 1658 the mechanics of muscular contraction. Even if ‘electrology or localised electrisation’—the original terminology for electromyography (EMG)—contained the oldest biological scientific detection and measuring techniques, EMG remained a ‘supporting’ measurement with limited discriminating use, except in conjunction with other methods. All this changed when EMG became a diagnostic tool for studies of muscle weakness, fatigue, pareses, paralysis, and nerve conduction velocities, lesions of the motor unit or for neurogenic and myogenic problems. In addition to the measurement qualities, the electrical signal could be induced as functional electrical stimulation (FES), which developed as a specific rehabilitation tool. Almost in parallel and within the expanding area of EMG, a speciality developed wherein the aim was to use EMG for the study of muscular function and coordination of muscles in different movements and postures. Kinesiological EMG and therewith surface EMG can be applied in studies of normal muscle function during selected movements and postures; muscle activity in complex sports; occupational and rehabilitation movements; isometric contraction with increasing tension up to the maximal voluntary contraction, evaluation of functional anatomical muscle activity (validation of classical anatomical functions); coordination and synchronization studies (kinematic chain); specificity and efficiency of training methods; fatigue; the relationship between EMG and force; the human-machine interaction; the influence of material on muscle activity, occupational loading in relation to lower back pain and joint kinematics. Within these various applications the recording system (e.g. the signal detection, the volume conduction, signal amplification, impedance and frequency responses, the signal characteristics) and the dataprocessing system (e.g. rectification, linear envelope and normalization methods) go hand in hand with a critical appraisal of choices, limits and possibilities.

Implications of an adjustable bed height during standard nursing tasks on spinal motion, perceived exertion and muscular activity

Manual handling is a source of occupational stress, particularly for nursing personnel. High levels of biomechanical strain are associated with lifting and transferring patients, especially when the tasks are performed in flexed and twisted positions that induce an increased risk of functional and musculoskeletal problems. The use of adjustable beds in nursing practice has been suggested as a means of influencing working postures and reducing the muscular demands on nurses. The purpose of this study was to investigate the effects on spinal motion, muscular activity and perceived exertion when nurses had the opportunity to adjust bed height. The measures recorded during the conduct of standardized patient handling tasks were the changes in posture (inclination) and in shape (sagittal bending, side bending, axial rotation). Muscular activity was measured using surface electromyography. Perceived exertion was rated using the 15-graded Borg scale. The range of motion was not influenced by the adjustment of bed height, but rather a shift of the time duration histogram was noticed in the direction of the erect, safer position. The time spent in the safe zone of spinal motion near the erect position was significantly increased and was significantly decreased in the potential health-hazardous zones of spinal motion in the extreme positions. No differences in muscular activity or in perceived exertion were found between the two bed height conditions for any of the muscle groups. It was concluded that the quality of spinal motion is enhanced when the opportunity of adjusting the bed height is offered.

Muscular activity of different shooting distances, different release techniques, and different performance levels, with and without stabilizers, in target archery

The quadruple approach in the title refers to four different studies over a period of 3 years. The common factor in these studies is the methodology of the (Brussels) Electromyographic Signal Processing and Analysis System (ESPAS), a hardware and software EMG data acquisition system that has constantly been improved. Therefore, the ESPAS methodology is described extensively (i.e. the electrodes, amplifier, tape-recorder and processing hardware). Experiment 1 investigated muscular behaviour in target shooting, both indoors (18 and 25 m) and outdoors (50, 70 and 90 m). It was found (via iEMG) that a significant increase in activity only exists between 25 and 50 m, and that there is no linear increase of activity with increased distance. No differences in muscular pattern (IDANCO system: Clarys and Cabri, 1988) or activity between the indoor distances and between the outdoor distances were found. Experiment 2 investigated the muscular economy of four string grips: the three-finger grip, two-finger grip, thumb grip and reversed grip. The largest variations in activity were found for the two most unfamiliar grips, i.e. the thumb and reversed grips; however, low iEMG and the rapid precision improvement (over a limited number of shots) suggest that the thumb grip, if practised long enough, might be the most economical technique. Experiment 3 attempted to differentiate muscular activity and a number of performance variables in three different populations of archers--Olympic athletes, National competitors and beginners--in order to obtain feedback regarding improved performance. Apparently, overall muscle pattern, intensities and arrow speed were not discriminatory. The differences found between the groups (or levels of skill) were affected by the ability to reproduce identical patterns and arrow velocities in consecutive shots and by the constancy of neuromuscular control of the M. trapezius, M. biceps brachii and M. extensor digitorum. Finally, Experiment 4 investigated the muscular activity of elite archers shooting at distances of 70 and 90 m with and without stabilizers. Differences in iEMG were not supported by differences in precision. Over time, the low iEMG in shooting without stabilizers increases precision and delays fatigue.

Variations of anatomical elements contributing to subtalar joint stability: intrinsic risk factors for post-traumatic lateral instability of the ankle?

Ankle sprains are frequently followed by chronic lateral instability, often with talar hypermobility. This might be due to subtalar instability. Among intrinsic risk factors, anatomical variants are generally overlooked. In the subtalar region, anatomical variation is particularly frequent. On the talus as well as on the calcaneus, the anterior articular facets may be missing or fused with the medial facets, giving rise to three subtalar joint configurations: a three-joint configuration, a fused configuration with a relatively large anteromedial joint, and a twojoint configuration without anterior joint. Osteometry was performed on these joint facets (134 calcanei, 122 tali), demonstrating significant differences in the surface of these configurations and the existence of a supplementary supporting surface with grossly transverse orientation in the three-joint configuration. There are also several variants of stabilizing ligaments within the sinus tarsi. Some of these configurations might expose to increased risk of associated subtalar lesions, resulting in subtalar instability. A systematic look for these variants is recommended in order to evaluate the associated risk factors, eventually resulting in a better understanding, prevention and cure of sequellae.

The influence of geographic variations on the muscular activity in selected sports movements.

Surface EMG (SEMG) has been used frequently to study motion techniques or skills, body positions, material or equipment used, training-methodology and learning processes in sports and ergonomics. Little if any information is available on the effect of the geographical environment on the neuromuscular control of an athlete or workman during his/her performance or effort. Motions were chosen in Alpine skiing and cycling. Thirty-one certified ski instructors and twelve professional road cyclists participated in the study of geographical variance and its impact on muscle activity. SEMG was measured from the agonists and antagonists of the upper- and lower limb. Skiers were measured on downhill slopes ranging from 19 to 51% while the cyclists performed with different saddle positions on 2, 7 and 12% slope inclinations, respectively. Verification of the variation of muscular intensity (IEMG) over the slope inclination during a simulated giant slalom indicated that the muscular activity increased with increasing slope angle and decreased with decreasing slope angle, while heart rate measured with short-range radio telemetry increased at a constant rate between start and finish independent of the geographical variations. In a direct descent on different slopes % levels the integrated EMG is well related to the inclination (r=0.82) confirming the findings of the giant slalom. In cycling we found that, regardless of the pelvis position, the muscular intensity of lower limb muscles increased with increasing slope inclination, while the muscular intensity of the arms decreased with the same increasing slope inclination. In addition the decreased intensity of the arm muscles remained significantly higher with the pelvis (saddle) fully forward. The geography of the terrain did influence the neuromuscular work and therewith probably the performance also. The influence however, varies with specific circumstances and is coupled with items of variability of the equipment used and the body regions involved.

Effects of skin thickness and skinfold compressibility on skinfold thickness measurement

Variability in both skin thickness and skinfold compressibility affects the relationship between the skinfold caliper reading at a particular site on the body and the actual adipose thickness at that site, thus inducing error in the estimation of body fatness. To investigate this variability, skinfold thickness by caliper and incised depth of subcutaneous adipose tissue were measured at 13 skinfold sites in 6 male and 7 female unembalmed cadavers aged 55 to 94 years. All skin was then removed and its thickness measured at the exact sites of skinfold measurement. The regional patterns for skin thickness were similar in men and women, though women had significantly (P < .05) thinner skin than men at the biceps, chest, supraspinale, and abdominal sites. Mean (SD) skin thickness for each cadaver over all sites ranged from 0.76 mm (0.28 mm) to 1.47 mm (0.43 mm), with an overall mean for men of 1.22 mm (0.36 mm) and for women of 0.98 mm (0.36 mm). The thickness of a double layer of skin expressed as a percentage of skinfold thickness for all cadavers over all 13 sites ranged from 7.1% to 33.4%. Because of their leanness and thicker skin, the mean for men, 22.7% (10.1%), was significantly greater than that for women, 10.8% (6.2%) (P < .0001). Mean skinfold compressibility over all sites was 53.5% (16.4%) in men adn 51.9% (16.5%) in women (not significant). Such marked variability in skinfold compressibility and in the relative contribution of skin thickness to skinfold thickness suggests the need for caution in comparing estimates of fatness by skinfold caliper between different subjects.