What is maximal tetanic tension?

Answer 1

When a muscle is applying a little bit of force, action potentials are triggering twitches in the muscle fibers. A skeletal muscle has many many muscle fibers, and a single fiber (cell) is either contracted or relaxed, it cannot get stronger or apply a fraction of its force. A muscle fiber and its connected neuron are called a motor unit

When a muscle is applying a lot of force it is sending many action potentials at once, such that most of the fibers in a muscle are contracting at once. This effect is called motor unit recruitment

When a muscle is "maxing out," it is sending waves of many action potentials in rapid succession, such that the whole muscle is stimulated again while the stimulated cells are still in the relaxing phase. This has the effect of not only reactivating the fibers in the relaxing phase, but also engaging more of the few cells that were left so that more total fibers contract.

When the signals are received in rapid enough succession the total force of the muscle will eventually plateau. This is called unfused tetanus. If applied at an even greater frequency the fibers that are activated will stay activated so that no lag is seen between single fiber twitches. It is at this point that the fibers are all fused and the muscle has reached maximum tetanic tension (This can occur as an effect in patients with tetanus, hence the name)