The percentage of
slow-twitch fibers was positively correlated with grilling loss, whereas an inverse relation between percentage of fast-twitch fibers was observed.
On one hand, single-frequency vibration systems operating within the muscle slow-twitch frequency will deliver the mechanical energy content of the vibration input plus the contraction energy of
slow-twitch fibers. When the frequency is set within the muscle fiber fast-twitch frequency, the mechanical energy content of the vibration input plus the contraction energy of fast-twitch fibers will be exerted on the bone.
Fast-twitch fibers also retain their ability to produce power much longer, up to six months, during detraining than
slow-twitch fibers, which lose their functional aerobic endurance capacity within approximately two weeks of inactivity.
The muscle's
slow-twitch fibers are designed for endurance.
If, initially, the force requirements are low, the
slow-twitch fibers are capable of handling the load.
The size of both fast-twitch and
slow-twitch fibers also decreases with aging, especially the fast-twitch fibers in the muscles of the lower body.
Finally, they assumed that the fatigue fraction decreased exponentially with increases in the difference between the time t at which the force is measured and the endurance time [t.sub.e], where this difference was scaled by the fatigue rate [k.sub.1] for the fast-twitch fibers and the fatigue rate [k.sub.2] for the
slow-twitch fibers. Specifically, they constructed the following model to predict the force Fit) at time t that participants can generate:
The muscles of the older athletes also had larger
slow-twitch fibers, perhaps because of long years of training.
It has been suggested that
slow-twitch fibers present higher stiffness due to their slower cross-bridge formation (15).
(2003) showed that postnatal rat soleus muscles undergo a shift from fast-twitch to
slow-twitch fibers, a process that can be accelerated upon intramuscular injection of NT-4/5.
Mastication muscles contain mostly fast-twitch fibers, with a smaller proportion of
slow-twitch fibers, Stedman says.
Lean Christina Clark uses mostly
slow-twitch fibers to run the marathon, a 42,164 meter (26.2-mile) race.
