Bouncing tendons keep you running well

摘要

How can the hrain ensure that muscles are working efficiently? During running, for example, it seems that it would require exquisitely precise tuning of contraction timing, strength and duration to coordinate all the leg muscles. Does the brain orchestrate the split second coordination or is some other intrinsic property of the leg responsible for our sprinting performance? In his Journal of Riomechanics paper A. L. Hof suggests a simple way to ensure efficiency. Hof knew that two muscles in the human calf, the soleus and gastrocncmius, shorten very little during running, even though the ankle moves a lot. This is intriguing, because these muscles arc most efficient when they shorten slowly and not very far. He describes his new theoretical model of the lower leg, which indicates that the spring-like Achilles tendon, to which both muscles attach, determines almost all ankle movement. Over a range of running speeds, the muscles can operate near maximum efficiency simply by turning on at the right time as the tendon stretches. So the intrinsic properties of muscles and tendons keep them working efficiently, almost independently of the brain's commands during fast activities, which means that the brain docs not need to he very precise at all.