Answer
Causes of Muscle Fatigue
Definition: The loss of contractility resulting from prolonged use of muscle
The following are some of the causes for this condition:
1. The accumulation of K+ ions at the generation of each action potential. The accumulation of K+ ions hyperpolarizes the cell. This makes muscle fibers less excitable. Aso K+ion in T-tubes inhibits the release of Ca++ from sarcoplasmic reticulum.
2. As more ATPs are hydrolyzed ADP+Pi accumulate in the sarcoplasm. This slows the cross-bridge
cycling mechanism of contraction.. Free pi inhibits Ca++release from SR ; this decreases the calcium sensitivity of the contractile mechanism and lowers the force production by the myofibrils.
Work Step by Step
3. Another factor is fuel depletion; glycogen levels fall; glucose levels fall. Therefore there is less fuel for ATP synthesis. When this happens in athletes they call it hitting the wall-- they are out of CHO fuel.
4. Electrolyte loss by perspiration is another reason. This alters the ionic balance in the ECF and this results in a decrease i excitability of muscle cells.
Finally there is the factor of central (CNS) fatigue . Ammonia produced during exercise is absorbed by the brain; this inhibits the motor neurons of the cerebellum and fewer signals will go out to the skeletal muscle.
