Skeletal muscle fibre characteristics in young women

Abstract

Muscle samples were obtained by needle biopsy from the lateral vastus muscle of 54 healthy female subjects, 18 to 40 years of age. 25 subjects were classified as sedentary, 20 as active, and 9 as endurance trained. In 33 of the subjects, the deltoid muscle was biopsied as well. The lateral vastus muscle of runners and the deltoid muscle of swimmers contained 60% slow twitch fibres (ST) an none or few fast twitch b fibres (FTb). Otherwise the percentage of fibre types was 50% ST fibres, 30% to 35% FTa fibres, and 15% to 20% FTb fibres. In the lateral vastus muscle ST fibres wee larger than FT fibres, whereas in male skeletal muscles FT fibres tend to be larger than ST fibres. The capillarization was linearly related to maximal oxygen uptake, as is also the case in male subjects. The activity of biochemically determined phosphofructokinase (PFK) was the same in both muscles and in all groups; succinate dehydrogenase activity (SDH) was closely related to maximal oxygen uptake. Th activities of PFK and SDH were lower than in male subjects the ratio between the activities indicated that the relative contribution of oxidative metabolism was higher than in males. The morphological and biochemical differences between female and male skeletal muscle are found in sedentary and trained subjects, and may be due both to the influence of sex hormones, and to differences in the daily activity pattern.

Skeletal muscle morphology and exercise response in congenital generalized lipodystrophy.

“…Using Cybex 340, peak torque assessment of the right and left quadriceps was 99 ± 41 and 96 ± 23 Nиm (normal value 200 Nиm); total work was 1,120 ± 281 and 977 ± 377 J, respectively (normal value 2,000 J), and the endurane ratio was 133 ± 36 and 110 ± 3, respectively (normal value 75). VO 2max of patients with CGL was 23-32 ml и kg Ϫ1 и min Ϫ1 , which is also below the mean values of 34-41 ml и kg Ϫ1 и min Ϫ1 reported in the healthy young sedentary women (17,19,20). 31 P NMR spectroscopy of the forearm muscles, however, revealed a normal pH and metabolic response to both static and dynamic exercise (Fig.…”

“…1). The mean cross-sectional areas of both type I (1,262-2,685 µm 2 ) and type II (2,304-3,594 µm 2 ) skeletal muscle fibers were also much below the mean values reported for the sedentary young women (3,811-4,310 and 3,115-4,193 µm 2 , respectively [15][16][17][18][19]) ( Table 1). The skeletal muscle capillary-to-fiber ratio in patients with CGL ranged from 2.7 to 2.95 compared with the value of 3.0 in the elite cross-country skiers from the laboratory (14) ( Table 1 and Fig.…”

“…Specific findings on quadriceps femoris biopsy included an increase in type II muscle fibers (75-77%) and a relative reduction in type I muscle fibers (22-25%). For comparison, mean values of 43-52% type I muscle fibers have been reported in vastus lateralis muscle of sedentary young women (16)(17)(18)(19)(20). Even after considering a wide range in muscle fiber composition in healthy women, our patients with CGL had a strikingly low proportion of type I muscle fibers.…”

“…1). The proportion of type I skeletal muscle fibers, therefore, was much reduced (22-25 vs. 43-52%, respectively [16][17][18][19][20]) (Table 1 and Fig. 1).…”

Selective long-term electrical stimulation of fast glycolytic fibres increases capillary supply but not oxidative enzyme activity in rat skeletal muscles

“…Thus endurance training led to an increase in oxidative enzymes prior to the increase in capillary supply (Andersen & Henriksson, 1977), while a parallel increase in the capillary to fibre ratio and proportion of oxidative fibres (Nygaard, 1982) or volume density of mitochondria (Zumstein et al 1983) has been described in different types of training. Similarly, high-intensity endurance training in animals resulted in increased capillary supply accompanied by increased oxidative capacity (Gute et al 1996).…”