Bedeutung des Zusammenspiels und der Wechselwirkung von Biomechanik und muskulärer Koordination für die muskuloskelettale Modellbildung

Based on synergies and redundancies in the human musculoskeletal system and the resulting degrees of freedom problem there are several muscular coordination strategies leading to the same movement. For a proper interpretation of the underlying muscular activation and the performed movement all based relationships and interactions, inner and outer, have to be considered with their influence and relevance for the interaction of biomechanics and muscular coordination. To reveal the interaction between biomechanics and muscular coordination during movement an integrated analysis of both is necessary, whereas additionally the kinematical context must also be considered to implement a valid musculoskeletal model.The presented publications show a significant influence of the joint position of proximal and distal joints on muscular coordination pattern in upper extremities. During elbow flexion the position of the wrist has a significant impact on the muscular coordination between M. biceps brachii and M. brachioradialis. Additionally pathological joint reaction forces are presented as the result from joint malposition during movement induced by muscular dysbalance. Taking to example inner shoulder rotation in children suffering from obstetric brachial plexus palsy, increased joint reaction forces in the shoulder joint have been shown.Both publications show the relevance of the consideration of the impact of biomechanics and muscular coordination on specific movement and vice versa. These results elucidate the necessity of a consequent validation and consideration of all possible influences on the performed movement for a proper musculoskeletal modeling approach

Energy requirements and metabolism of the Phillip's dikdik (Madoqua saltiana phillipsi)

Basal metabolic rates in mammals are mainly determined by body mass, but also by ecological factors. Some mammalian species inhabiting hot, dry environments were found to have lower metabolic rates compared to temperate species. We studied energy metabolism in Phillip’s dikdik (Madoqua saltiana phillipsi), a small antelope inhabiting xeric shrubland habitats in the Eastern 'horn' of Africa, and compared results to literature data. We measured body mass (BM) changes and digestibility in 12 adults kept on different food intake levels to determine, by extrapolation to zero BM change, maintenance energy requirements (MEm) for metabolizable energy (ME). The MEm averaged at 404 ± 20 kJ ME kg BM -0.75 d-1. In addition we conducted 24 h-chamber respirometry with seven fed (non-fasted) individuals. Their mean metabolic rate as calculated from oxygen consumption was 403 ± 51 kJ kg BM-0.75 d-1, corroborating the results of the feeding trials. Selecting the 20 lowest values of the respiration measurement period to estimate resting metabolic rate (RMR) resulted in a mean RMR of 244 ± 39 kJ kg BM-0.75 d-1, which was numerically (but not significantly) lower than the expected basal metabolic rate of 293 kJ kg BM-0.75 d-1. Therefore, resting metabolism was similar to the expected average basal metabolism of a mammal of this size, which suggests a comparatively low metabolic rate in dikdiks. Compared to literature data Phillip’s dikdiks have a MEm similar to measurements reported for small domestic ruminants, but considerably lower than those reported for other wild ruminant species inhabiting temperate and cold climates

Feeding microstructure in diet-induced obesity susceptible versus resistant rats: central effects of urocortin 2

With one billion people overweight worldwide, the need to identify risk factors and treatments for obesity is urgent. The present study determined whether rats genetically prone to diet-induced obesity (DIO) show preexisting differences in meal microstructure and are sensitive to central anorectic effects of corticotropin-releasing factor type 2 (CRF2) receptor stimulation. Male, selectively bred DIO rats and their diet resistant (DR) counterparts (n = 9/genotype) were weaned onto low-fat chow and compared as young adults for spontaneous or intracerebroventricular urocortin 2 administration-induced (0, 0.3, 1, 3 μg) differences in ingestion. DIO rats were hyperphagic selectively at the dark cycle onset, showing shorter latencies to initiate feeding, faster returns to eating following meal completion, and a lower satiety ratio than DR rats. At other times, DIO rats had briefer postmeal intervals, but ate smaller and briefer meals, resulting in normal intake. DIO rats also ate faster than DR rats. Urocortin 2 was less potent in DIO rats, ineffective at the 0.3 μg dose, but produced CRF2 antagonist-reversible anorexia at higher doses. Though heavier, chow-maintained DIO rats were proportionately as or more lean than DR rats. Thus, DIO rats showed signs of a preexisting, heritable deficit in the maintenance of postmeal satiety and a reduced sensitivity to anorectic CRF2 agonist stimulation. The meal patterns of DIO rats temporally resemble human ‘snacking’ behaviour, which predicts adult obesity. Because central CRF2 stimulation retains full anorectic efficacy at higher doses in the DIO model, manipulating this neuropeptidergic system might yield new therapeutic approaches for diet-induced obesity