Muscle fiber number in the biceps brachii muscle of young and old men

Abstract

We have compared the number of muscle fibers in the biceps brachii muscle (BB) of six old men (82.3 +/- 4.3 years) and six young men (21.2 +/- 1.9 years). Muscle fiber number was estimated by dividing the maximal area of the BB, determined with magnetic resonance imaging, by the mean fiber area of the BB determined in a muscle biopsy. The percentage of type II fibers in the BB ( approximately 60%) and the type I fiber area were not different between the groups. The BB area (-26%), type II fiber area (-24%), mean fiber area (-20%), and maximal voluntary contraction strength (MVC) of the elbow flexor muscles (-27%) were lower in the old than young group. However, the estimated number of muscle fibers was not significantly different between the young (253000) and old (234000) men. Consequently, the smaller BB area of the old men could be explained primarily by a smaller type II fiber size. These findings suggest that old age is not associated with a reduced number of muscle fibers in the BB. The relative contribution of a reduction in fiber number to age-related muscle atrophy may be muscle-dependent.

Effects of Aging on Type II Muscle Fibers: A Systematic Review of the Literature

“…Whereas some studies found no significant difference (Aniansson et al, 1992(Aniansson et al, , 1986Coggan et al, 1992;Grimby, Danneskiold-Samsoe, Hvid, & Saltin, 1982;Klein, Marsh, Petrella, & Rice, 2003;Lexell, Henriksson-Larsen, Winblad, & Sjostrom, 1983), others showed a decrease in Type II fiber proportion (Aniansson et al, 1992;Fayet, Rouche, Hogrel, Tome, & Fardeau, 2001;Larsson et al, 1979;Larsson, Sjodin, & Karlsson, 1978;Lexell, Downham, & Sjostrom, 1986;Monemi, Eriksson, Eriksson, & Thornell, 1998;Poggi et al, 1987). This decrease seems to appear between the ages of 76 and 80 years, whereas there was no change of proportion between 69 and 76 years (Aniansson et al, 1992).…”

“…One study reported that this loss of fibers mainly affected Type II fibers (Lexell et al, 1983). One study investigating the biceps brachii, however, revealed no loss of fibers (Klein et al, 2003).…”

Effect of Age and Gender on Muscle Function-Analysis by Muscle Fiber Conduction Velocity-

“…Most papers have reported that differences by gender are observed in diameter of muscle fibers. However, regarding the ratio of Type I and II fibers in quadriceps femoris, one report indicated that females display a higher ratio of Type I fibers 27) , another showed that males display a higher ratio of Type I fibers 30) , and a third report found no gender differences 3) . This may indicate that no clear differences by gender exist.…”

Optimal health and function among the elderly: lessening severity of ADL disability

“…Mitochondrial density has been found to be lower in their skeletal muscle of older individuals, which could further diminish capacity for endurance work. Thus, it may be that aging-related atrophy of skeletal muscle plays some role in the aging-related decline in work endurance [34] and strength [58].…”