fast-twitch fibers

(redirected from Type II fibers)

fast-twitch fi·bers

(fast-twich fī'bĕrz)
Histologically distinct skeletal muscle fibers that generate energy rapidly and are active in quick, powerful actions; subclassified as types IIa and IIb.
Synonym(s): fast glycolytic (FG) fibers, fast-oxidative-glycolytic (FOG) fibers, Type II fibers.
References in periodicals archive ?
1987) reported that in lambs fed cimaterol the proportion of type I to type II fibers in the longissimus and semitendinosus muscle were unaffected.
In human, where the MyHC2b is hardly expressed in type II fibers, a long-term AAS administration (power lifters taking anabolic supplements for nearly 10 years) increased the CSA of type I and type II fibers both in m.
Type I fibers use aerobic metabolism, making type I fibers more important in endurance activities whereas type II fibers use anaerobic metabolism, making type II fibers more important for sprint and power athletes.
Histologically, sarcopenia appears as a decrease in muscle fiber size, with preferential loss of type II fibers (32).
Strength relies on the presence of larger, more numerous type II fibers.
People whose muscles were affected by polio use both type I and type II fibers for ordinary walking.
14) In individuals of all ages, type II fibers are able to generate significantly more force than type I fibers, (15) so not surprisingly, maximal strength is positively related to the percentage of type II fibers in older adults.
Type land type II fibers coexist in these muscles, but they are classified into distinct groups.
As the stimulus continues and strengthens, the stronger and larger Type II fibers are recruited.
Top-flight sprinters have up to 80% type II fibers while long-distance runners have up to 90% type I fibers.