INTERNAL LOAD ESTIMATION FOR CLINICAL PROGNOSIS

Introduction: In therapy and rehabilitation it is important to know the ranges of the expected loads in the human body resulting from different movements. Because of the difficulty of measuring experimental dynamic loads (hip loads, Bergmann, Taylor), the loads created under these dynamic conditions are estimated by theoretical models and computer simulation. The method will be presented considering a squat jump. Methods: A squat jump performed with both legs, maximum strength and without counter-movement was modeled by a two-dimensional multi-body system with four segments. The movement-generating muscles were implemented taking into account the muscle insertions and paths, as well as Hill’s force-velocity-relation. The data were extracted from MR images and the literature. The muscles were excited by Hatze’s stimulation model. To obtain maximal jump height, the muscles were excited coordinately by optimization algorithms. Results: In the case of a vertical jump, the loads reached maximum values of 4250 N, 4750 N and 4800 N in hip, knee and ankle joints, respectively. The mean values of the hip, knee and ankle joint loads were 3100 N, 3650 N and 2600 N, respectively. Comparing the calculated values with those of Bassey et al. (1997), who measured the hip load during a fast jump, a good agreement of the load values was found. Conclusion: With this vertical jump it was proved that an estimation of joint loads is possible. A multitude of movements can be examined with this model in order to compile data for a joint load database which can be used for clinical prognosis. References: Bassey, E.J., Littlewood, J.J., Taylor, S.J.G. (1997). Relations Between Compressive Axial Forces in an Instrumented Massive Femoral Implant, Ground Reaction Forces, and Integrated Electromyographs From Vastus Lateralis During Various Ostogenic Exercies. J. Biomechanics 30, 213-223. Bergmann, G., Graichen, F., Rohlmann, A. (1993). Hip Joint Loading During Walking and Running, Measured in Two Patients. J. Biomechanics 26, 969-990

MUSCLE ACTIVITY OF THREE SUBJECTS DIFFERING IN WEIGHT AND HEIGHT DURING A VERTICAL JUMP

Introduction: The first measurement was done to evaluate changes of potentials of surface electromyography with different locations of electrode sites and different resistors between the electrodes. The objective of the second was to investigate the activity of muscles in their stimulation sequence, the quantitative participation of the single muscle and cinematic study of vertical jumps. This work is part of a project to determine the internal forces of the human motional apparatus with an anatomical model of muscles. Methods: For each measurement we chose a Noraxon EMG, ECG electrodes from Medicotest, and the electrodes were placed following the description of D.A. Winter. At first we chose the M. gastro. med., M. gastro. lat., and M. soleus of male subject and did a measurement while the subject moved ten times from a ‘standing at attention’ posture to standing on the tips of his toes with a resistor between the electrodes higher than 60 Ohm and one with a resistor lower than 5 Ohm. Then we moved the electrodes 2 cm and 4 cm in the vertical and horizontal directions (resistor of lower than 5 Ohm). Secondly, we chose eight muscles (M. glut. max., M. semitend., M. biceps femoris, M. rectus femoris, M. vastus lat., M. vastus med., M. gastro. med., M. soleus) of three male subjects differing in weight and height and did the measurements while the subjects jumped ten times from a squatting position on a force plate, filmed by a high-speed camera. Results: The measurements with a 60 Ohm resistor and a 5 Ohm resistor differed, as well as the measurements with different locations of electrode sites. The second measurements showed that the M. gas. med. seemed to be the muscle with the highest response, followed by the M. sol. The M. vast. med., M. vast. lat., M. bic. fem. and M. rec. fem. had the same type of reaction. In one case the M. glut. max. seemed to be important while jumping. In an second case the M. semit. showed a high response. The muscles of the tallest subject had the longest activity, and the muscles of the shortest one had the shortest activity. The timedependent angles of knee, hip and foot joints of every subject were nearly identical. Like the EMG, the acceleration phases of the tallest subject took the longest time, while the acceleration phase of the shortest subject took the least time. Conclusions: Firstly, it is possible to see how important the placement and resistor of the electrodes is. Secondly, there is a possible relationship between the beginning of the activity of the muscles and the size of the subjects, as well as a correlation of the angles and the size of the subjects. This effect should be considered in using such calculations of the internal forces of the human motional apparatus in the development of protheses and in sports science

Unusual cause of exercise-induced ventricular fibrillation in a well-trained adult endurance athlete: a case report

<p>Abstract</p> <p>Introduction</p> <p>The diseases responsible for sudden deaths in athletes differ considerably with regard to age. In young athletes, congenital malformations of the heart and/or vascular system cause the majority of deaths and can only be detected noninvasively by complex diagnostics. In contrast, in older athletes who die suddenly, atherosclerotic disease of the coronary arteries is mostly found. Reports of congenital coronary anomalies as a cause of sudden death in older athletes are rare.</p> <p>Case presentation</p> <p>A 48-year-old man who was a well-trained, long-distance runner collapsed at the finish of a half marathon because of a myocardial infarction with ventricular fibrillation. Coronary angiography showed an anomalous origin of the right coronary artery from the left sinus of Valsalva with minimal wall alterations. Multislice computed tomography of the coronary arteries confirmed these findings. Cardiomagnetic resonance imaging demonstrated a mild hypokinesia of the basal right- and left-ventricular posterior wall. An electrophysiological study showed an inducible temporary polymorphic ventricular tachycardia and an inducible ventricular fibrillation. The athlete was subsequently treated by acetylsalicylic acid 100 mg (0-1-0), bisoprolol 2.5 mg (1-0-0) and atorvastatin 10 mg (0-0-1) and was instructed to keep his training intensity under the 'individual anaerobic threshold'. Intense and long-lasting exercise under extreme environmental conditions, particularly heat, should also be avoided.</p> <p>Conclusion</p> <p>This case report presents a coronary anomaly as the most likely reason for an exercise-induced myocardial infarction with ventricular fibrillation in a well-trained 48-year-old endurance athlete. Therefore, coronary anomalies have also to be considered as a possible cause of cardiac problems in older athletes.</p

Effect of a supplement rich in alkaline minerals on acid-base balance in humans

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Answer to D. Böning's and J. M. Steinacker's Letter to the Editor “Problems with Doping in Scientific Articles?”

Letters to the Edito

Heart-rate recommendations: transfer between running and cycling exercise ?

La fréquence cardiaque est utilisée comme référence pour adapter l'intensité de l'entraînement. Mais les mesures de la fréquence cardiaque sont-elles transposables d'un type d'ergométrie à l'autre (tapis-roulant/bicyclette-ergométrique)