Estimating in vivo passive forces of the index finger muscles: Exploring model parameters

Muscle-tendon units provide limited contributions to the passive stiffness of the index finger metacarpophalangeal joint

“…For the sake of comparison, we adopted the values of the maximal MTU excursion (Dlmt ) from the ten subjects as inputs to the passive forcelength equation given in Ranney et al (1987): Fp ¼ b 1 e b 2 ÁDlmt , and the values for the two parameters b 1 and b 2 were adopted from Ranney et al (1987). MCP joint stiffness is the result of only the muscle passive forces (Qin et al, 2010). Based on the results of our study showing that the CLC provides dominant stiffness contribution, the results from this study may have to be updated.…”

“…For the sake of comparison, we used the same MTU stretch values in our model and in the models developed in a previous study (Keir et al, 1996). The higher force value may have resulted due to the overestimation of the in-vivo passive force values using the in-vitro muscle models (Qin et al, 2010).…”

“…Because of its prominent role in many hand functions, a number of studies have focused on investigating the joint stiffness of the index finger metacarpophalangeal (MCP) joint (Minami et al, 1985;Esteki and Mansour, 1996;Knutson et al, 2000;Kamper et al, 2002;Qin et al, 2010). The muscle-tendon units (MTUs) contribute to the passive MCP joint stiffness by generating resistive forces when stretched (Qin et al, 2010;Dennerlein, 2005). In addition to the MTUs, the capsule-ligament complex (CLC) at the joint provides resistance, especially to prevent joint instability (Minami et al, 1985;Tamai et al, 1988).…”

“…A number of previous studies assume, either explicitly or implicitly, that this joint stiffness is strictly due to the passive forces from the stretching of muscles and tendons, and that the effect of CLC can be ignored (Qin et al, 2010;Dennerlein, 2005). However, this assumption is not substantiated by a quantitative analysis of passive moment generation.…”

Contribution of passive properties of muscle-tendon units to the metacarpophalangeal joint torque of the index finger

“…The studies based on the experiments with human subjects in which passive joint torques and joint angles were measured estimated that the net passive joint torque is mainly composed of the passive torque due to MTU elasticity [16], [8]. However, another study demonstrated that the model parameters derived from the exponential relationship may overestimate the actual contributions of the MTU passive torques [21]. To understand the passive joint behavior there is a need to quantify the contributions of the MTUs and joint tissues to the net passive torques.…”