Voluntary strength and muscle characteristics in untrained men and women and male bodybuilders

Abstract

Eight untrained women (F), 13 untrained men (M), and 11 male bodybuilders (BB) did maximal elbow flexions on an isokinetic dynamometer at velocities of 30, 120, 180, 240, and 300 degrees/s, from which impact torque (IT), peak torque (PT), and work (W) were measured. Biceps and total flexor cross-sectional area (CSA) were measured by computerized tomographic scanning. Muscle fiber area, fiber composition, and collagen volume density were determined from single needle biopsies of biceps brachii. Biceps fiber number was estimated as the ratio of biceps CSA (corrected for connective tissue) to mean fiber area. PT and W decreased at higher velocities in M and BB but not in F; consequently, the correlation between CSA and PT and W was lower at 300 degrees/s (r = 0.58, 0.60) than 30 degrees/s (r = 0.80, 0.79). The ratio of PT to flexor CSA was similar in all groups at 30 degrees/s, whereas F had greater ratios than M and BB at the remaining velocities. F had greater W/CSA ratios than M and BB at all velocities. IT increased at higher velocities in all groups; the increase was greater in F and M than in BB. In contrast to PT and W, the correlation between IT and CSA was greater at 300 degrees/s (r = 0.67) than 30 degrees/s (r = 0.58), and there were no differences among groups in the IT/CSA ratios. Flexor CSA correlated negatively with the ratio of IT, PT, and W to CSA. Muscle fiber composition failed to correlate with any measure of strength. M and BB had greater biceps area, fiber number, and fiber area than F.(ABSTRACT TRUNCATED AT 250 WORDS)

Myocellular triacylglycerol breakdown in females but not in males during exercise

“…Other studies have found that in UT subjects (42), middle-distance runners (5), trained cyclists (11), and subjects representing a wide range of physical activity levels (33), females had a higher percentage of type I fibers than males. At all training levels in the present study, the area of all the fiber types was smaller in females than in males, especially for type II fibers, which is in accordance with previous observations (5,35,39,40,42). As a consequence, the calculated fiber composition expressed relative to fiber area revealed that type I fibers accounted for a relatively larger area in females than in males.…”

“…However, UT females had a higher percentage of type I fibers than UT males. Previously, a similar fiber type composition in females and males has been found in UT subjects (5,35,39) as well as in physical education students (40). Other studies have found that in UT subjects (42), middle-distance runners (5), trained cyclists (11), and subjects representing a wide range of physical activity levels (33), females had a higher percentage of type I fibers than males.…”

Positive adaptations to weight-lifting training in the elderly

“…It cannot be argued that hypertrophy in these older muscles was entirely the result of connective tissue proliferation, because the increase in fiber size was at least equivalent to that of the whole muscle. Furthermore the greatly hypertrophied muscles of bodybuilders show no evidence of connective tissue proliferation (32). In the previously cited study of rat soleus (16), hypertrophy after 30 days of overload was not associated with connective tissue proliferation, an increase in interstitial fluid volume, or a decrease in protein content.…”

The ACTN3 R577X nonsense allele is under-represented in elite-level strength athletes

“…7 -9 The strength athletes exhibit extreme muscle hypertrophy, 14,15 with performance measured either as physical appearance or single-repetition maximal force production (strength), rather than the multiple contraction events typical of sprint-related athletes. 7 -10 Because the a-actinin protein is important for maintaining the myofibrillar array within represent another mechanism explaining our findings.…”