Tendon

The tendon is the part that joins muscle to bone, and it is aptly called a mechanical bridge. It is a tough, fibrous structure whose job is to carry the force the muscle generates to the bones and joints, so that movement can happen.

That job calls for some very specific properties. A tendon is stiffer than muscle and holds up better to tension, that is, to pulling. And it withstands very large loads while barely deforming. That last point matters more than it seems: if the tendon stretched a lot, much of the muscle's effort would go into stretching it instead of moving the bone. Because it deforms so little, almost all of the force reaches its destination.

There is a second advantage, more a matter of design. Thanks to the tendon, the muscle can stay at the optimal distance from the joint it moves. Without the tendon, the muscle would have to be excessively long between where it originates and where it inserts, that is, the fleshy part would have to be much longer.