Modelling force-length-activation relationships of wrist and finger extensor muscles

Hill-type computational models of muscle-tendon actuators: a systematic review

“…The FLA property is phenomenologically captured in three eligible models (Winters, J. M., 1995; Lloyd & Besier, 2003; Blümel et al, 2012) with an activation-dependency of the CE optimal length , which improves the accuracy of the model predictions (Sun et al, 2018). However, it is believed that the FLA approach phenomenologically encapsulates in these studies some ADL properties at the NE level (Rassier et al, 1999), that are responsible for the length-dependencies of the experimental frequency-force (Rack & Westbury, 1969; Brown et al, 1999), EMG-force (Goislard de Monsabert et al, 2020) and pCA-force (Stephenson & Williams, 1982) relationships. It is proven that the calcium transients are length-dependent (Blinks et al, 1978; Baylor, S. M. et al, 1983; Close & Lännergren, 1984; Konishi et al, 1991) as the muscle geometry affects the dynamics of calcium release from the sarcoplasmic reticulum and calcium diffusion in the sarcoplasm.…”

“…The FL relationship is empirically observed Stephenson & Wendt, 1984;Guimaraes et al, 1994;Huijing, 1996;Balnave & Allen, 1996;Rockenfeller & Günther, 2018;Goislard de Monsabert et al, 2020) to distort for submaximal contractions towards peak forces occurring at longer CE lengths. It is explained, at the CE level, by changes in the force transmission pathways between the multiscale layer of the muscle (Huijing, 1999) to minimize the muscle internal work and optimize force production (Holt & Azizi, 2014).…”

Influence of Force–Length Relationship and Task-Specific Constraints on Finger Force-Generating Capacities

“…The same musculoskeletal model as the study focusing on power grip 3 was used to estimate the force (𝐹 𝑚 ) and length (𝐿 𝑚 ) of FDS, EDC, FCR and ECR from measured anthropometrics (𝐿 𝑟 𝑚𝑡𝑢 , 𝐿 ℎ𝑎𝑛𝑑 ), joint angles (𝜃 𝑗 ) and muscle activation (𝑎 𝑚 ). This model is mainly based on experimentally-derived Force-Length-Activation relationship obtained from previous studies 8,12 and is presented in detail in Electronic Supplementary Materials (ESM2). Those relationships consider the activation-dependency of the muscle contraction, especially the shift in optimal length at low activation.…”

“…The lack of proof of regarding the role of force-length relationships in grip force loss in deviated wrist positions is due to a lack of in vivo data of finger muscle mechanics, since most studies focused on the larger muscles, from the upper 16 and lower 2,27 limbs. Thanks to recent studies on hand muscle force-length relationships 8,12 , new data were provided and showed that during a power grip task the capacities of finger flexors remained close to optimal despite changes of wrist postures 3 , while the wrist extensor capacities decreased importantly for flexed and extended wrist. Those results suggest that wrist extensors could thus be seen as the muscle group inducing a large part of grip strength variations, contrary to previous hypothesis attributing it to the finger flexors.…”

“…Because prehensile task involves higher co-contraction of extensors 22 and thus more muscles, the first hypothesis is that maximal finger force will vary more with wrist posture during Pinch compared to Press. Since flexor muscle capacities are less impacted by wrist posture 3,8 , our second hypothesis was that finger and wrist extensor capacities are importantly correlated with the grip modulation. Finally, as observed in our previous study on power grip 3 , the third hypothesis was that the length configuration of all muscles must be considered to explain the wrist posture that maximises finger force.…”