Answer Happy

The amount of passive tension that a muscle fiber can produce during a stretch depends on the length that titin reaches during the stretch. Titin length during a stretch is determined by the number of sarcomeres in series in the muscle fiber. When a muscle fiber has a lot of sarcomeres in series, each sarcomere (and therefore each titin molecule) does not stretch very far. Conversely, when a muscle fiber has few sarcomeres in series, each sarcomere (and therefore each titin molecule) stretches a long way. Titin typically only starts to produce passive force during a passive muscle stretch when the sarcomere reaches a point called the "descending limb" of the length- tension relationship. Researchers have shown that the sarcomeres of the triceps brachii tend not to reach this point during a normal strength training exercise.