How Muscles REALLY Work: Sliding Filament Theory

How do muscles work? This video explains the sliding filament theory of muscle contraction, the force-length relationship, and the force-velocity relationship.

The cross-bridge cycle is explained in detail, in relation to calcium, actin, myosin, troponin, tropomysoin, and more. The underlying theory of muscle contraction mechanics is used to explain the causes of muscle's force-length and force-velocity relationships.

00:00 How do muscles work?
00:15 How is muscle structured?
00:31 The sarcomere
00:53 Cross-bridge cycles and the sliding filament theory
02:03 Muscle cross-bridge cycles in 3D
02:37 The force-length relationship in muscle
04:06 The force-velocity relationship in muscle
05:07 Power in muscle (force x velocity)
05:27 Muscle mechanics in detail

Source of GIFs/Videos used:

[ДимаМ-зж]

Why is it about the optimal length of the muscles, and not about the optimal length of sarcomeres? It seems to me that the optimal muscle length in which the muscle can generate its maximum active force and the optimal length of the fibers (sarcomeres) in which the muscle fibers can generate its maximum active force do not quite correlate with each other (due to the fact that the length-tension relationship for the entire muscle also takes into account the tendons, and not just the range of the working sarcomeres of the fibers), isn't that so?