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This study investigated the effect of isometrically induced fatigue on Hill-type muscle model parameters and related task-dependent effects. Parameter identification methods were used to extract fatigue-related parameter trends from isometric and ballistic dynamic maximum voluntary knee extensions. Nine subjects, who completed ten fatiguing sets, each consisting of nine 3 s isometric maximum voluntary contractions with 3 s rest plus two ballistic contractions with different loads, were analyzed. Only at the isometric task, the identified optimized model parameter values of muscle activation rate and maximum force generating capacity of the contractile element decreased from $$20.8 \pm 8.4$$ to $$11.2 \pm 4.1$$ Hz and from $$18{,}137 \pm 150$$ to $$10{,}666 \pm 2139$$ N, respectively. For all tasks, the maximum efficiency of the contractile element, mathematically related to the curvature of the force–velocity relation, increased from $$0.35 \pm 0.04$$ to $$0.42 \pm 0.05$$ . The model parameter maximum contraction velocity decreased from $$0.93 \pm 0.1$$ to $$0.9 \pm 0.1$$ m/s and the stiffness of the serial elastic element from $$1936 \pm 227$$ to $$1432 \pm 245$$ N/mm. Thus, models of fatigue should consider fatigue dependencies in active as well as in passive elements, and muscle activation dynamics should account for the task dependency of fatigue.

Neural commands control skeletal muscles that act on passive structures and regulate voluntary movements. Mathematical models can simulate such movements and therefore require the knowledge of neuromuscular properties. In contrast to scaling these properties to the individual, we present a non-linear parameter identification method to determine them non-invasively and in vivo. The classic model A describes an excitable contractile element (CE) embedded in a geometrical representation of the leg. Its extension model B is used to study the effects of the force–length relationship and the serial elastic element (SEE). We show the validation of model B and discuss the quality of neuromuscular properties identified from simulations and experiments. The main finding is that identifications that consider CE–SEE dynamics result in increased and more realistic curvatures of the force–velocity relations. This shows that CE and SEE work interdependently and we recommend to co-ordinate the parameter values of...

Je nach Training, Tempo und individuellen Vorlieben gibt es drei Laufstile: Vor-, Mittel- und Ruckfuslaufstil. Der Vorfuslaufstil ist am schnellsten und erfordert am meisten Athletik. Auch die Schuhe haben Einfluss. Konventionelle Laufschuhe sind gut gedampft, vermitteln aber ein schlechteres Gefuhl fur den Bodenkontakt. Bei Barfuslaufschuhen ist es umgekehrt. Dafur treten bei diesen uberwiegend hohere Kraftspitzen an Fusen und Beinen auf. Mit dem Altern lasst die Dampfung und Elastizitat von Sportschuhen messbar nach.

Beim Bogenschiesen spielen mechanische Eigenschaften von Pfeil und Bogen wie Schwingungen, Energieubertragung und Widerstande eine grose Rolle. Zusatzlich sind aber auch neurologische und physiologische Eigenschaften des Schutzen von Bedeutung. Dazu zahlen Ansteuerung und Ermudung der Muskulatur beim Zielen und rechtzeitige Aktivierung der Muskulatur zum Stabilisieren des Bogens beim Abschuss.