Abstract
The purpose of this study was to further develop the constant power model of a previous study and to provide the final solution of Hill’s force-velocity equation. Forearm and whole arm rotations of three different subjects were performed downwards (elbow and shoulder extension) and upwards (elbow and shoulder flexion) with maximum velocity. These arm rotations were recorded with a special camera system and the theoretically derived model of constant maximum power was fitted to the experimentally measured data. The moment of inertia of the arm sectors was calculated using immersion technique for determining accurate values of friction coefficients of elbow and whole arm rotations. The experiments of the present study verified the conclusions of a previous study in which theoretically derived equation with constant maximum power was in agreement with experimentally measured results. The results of the present study were compared with the mechanics of Hill’s model and a further development of Hill’s force-velocity relationship was derived: Hill’s model was transformed into a constant maximum power model consisting of three different components of power. It was concluded that there are three different states of motion: 1) the state of low speed, maximal acceleration without external load which applies to the hypothesis of constant moment; 2) the state of high speed, maximal power without external load which applies to the hypothesis of constant power and 3) the state of maximal power with external load which applies to Hill’s equation. This is a new approach to Hill’s equation.
Highlights
Hill’s force-velocity relationship of skeletal muscle (Figure 1) [1] [2] is one of the most essential equations ofHow to cite this paper: Rahikainen, A. and Virmavirta, M. (2014) Constant Power Model in Arm Rotation—A New Approach to Hill’s Equation
The theoretical and measured angular velocity curves coincided within the distances of 35 - 70 mm, which was enough for the verification of the constant power model in the arm rotation experiments
The present study confirmed the existence of constant power model in arm rotations with maximum velocity
Summary
Hill’s force-velocity relationship of skeletal muscle (Figure 1) [1] [2] is one of the most essential equations ofHow to cite this paper: Rahikainen, A. and Virmavirta, M. (2014) Constant Power Model in Arm Rotation—A New Approach to Hill’s Equation. Muscle mechanics and it has been an object of biomechanical studies for years (e.g., [3]-[6]) In muscle mechanics, this relationship is often presented by Hill’s equation ( F + a)(v + b)= b ( F0 + a) , where F is current muscle force at current shortening velocity of contraction, a is constant force and b is constant velocity, F0 is the maximum isometric muscle force, i.e., the maximum force that muscle can develop at a given constant length, and v is velocity [1] [2]. The length of the muscle’s moment arm (r) changes as the rotational movement proceeds about the joint axis This rotation movement is the combined effect of the forces of several different muscles. In this paper [12] the process of learning fast elbow flexion in the horizontal plane was simulated and the result was compared with experimentally measured data
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