James B. Brown

Gender differences in FFM accumulation and architectural characteristics of muscle

PURPOSE The purpose of this study was to gain insight into the skeletal muscle development potential in women and to evaluate the contribution of muscle pennation angle (PANG) and fascicle length to gender differences in muscle size or FFM accumulation. METHODS Skeletal muscle architectural characteristics and FFM were studied in 29 strength-trained female and 22 age- and height-matched male college athletes. Muscle thickness (MTH) was measured by B-mode ultrasound at 13 anatomical sites. Isolated MTH and PANG of the triceps long head (TL), vastus lateralis (VL), and gastrocnemius medialis (MG) muscles were measured in vivo, and fascicle length was estimated. RESULTS Six female athletes had more than 60 kg of FFM, with the largest being 82.1 kg. In general, male athletes had a significantly greater FFM and MTH at all sites except for the anterior thigh. Isolated MTH and PANG of the TL, VL, and MG were greater in males. There were no gender differences in limb length or fascicle length of the three isolated muscles. A significant correlation was observed between MTH and PANG for TL (r = 0.84) and MG (r = 0.41), but not for VL. CONCLUSIONS In contrast to previous estimates, we conclude that the theoretical upper limit of FFM accumulation and FFM-to-height ratio in women is greater than 80 kg and 0.44 kg.cm-1, respectively. Gender differences in PANG appear to be related to differences in muscle size (MTH) and do not appear to contribute independently to the gender difference in FFM.

Architectural characteristics of muscle in black and white college football players

PURPOSE The purpose of this study was to determine whether architectural characteristics of skeletal muscle differ by race. METHODS Skeletal muscle architectural characteristics and body composition were studied in 13 black and 31 white male college football players. Fat-free mass (FFM) and percentage body fat (% fat) were determined by hydrostatic weighing technique. Muscle thickness (MTH) was measured by B-mode ultrasound at 13 anatomical sites. Isolated MTH and muscle pennation angle (PANG) of the triceps long head, vastus lateralis, and gastrocnemius medialis muscles were measured by ultrasound, and fascicle length was estimated. RESULTS There were no significant differences between blacks and whites in isolated MTH, PANG, and fascicle length in the triceps long head, vastus lateralis, and gastrocnemius medialis muscles. On average, % fat and FFM of black and white football players were 18.8 +/- 4.6% and 17.2 +/- 5.6% for % fat, and 89.9 +/- 15.6 kg and 89.1 +/- 10.4 kg for FFM, respectively. Blacks had a significantly greater, 30%-quadriceps (P < 0.05), 50%-hamstrings (P < 0.05), biceps (P < 0.01), and abdomen (P < 0.01) MTH than those of whites. Standing height and body weight were similar between blacks and whites, but the ratio of leg length to standing height was significantly greater in blacks compared with whites. CONCLUSIONS It appears that although there may be race differences in anatomical stature, muscle architecture is likely independent of race.

CHRONIC CLENBUTEROL ADMINISTRATION ALTERS MYOSIN HEAVY CHAIN COMPOSITION IN STANDARDBRED MARES

The purpose of this study was to examine changes in myosin heavy chain (MHC) composition due to chronic clenbuterol administration with or without exercise in mares. Unfit Standardbred mares (aged 10+/-3 years) were divided into four groups: clenbuterol (2.4 micro/kg BW twice daily) plus exercise (3 days/week for 20 min at 50% VO(2max); CLENEX; n=6), clenbuterol only (CLEN; n=6), exercise only (EX; n=5), and control (CON; n=6). Muscle biopsies were obtained from gluteus medius muscle before and after the eight-week training/administration period. MHC composition was determined via SDS gel electrophoresis and quantified using a scanning and densometric system. CLENEX and CLEN exhibited significant (P<0.05) MHC changes while EX and CON did not. MHC type IIA decreased (29.8+/-6.1 to 19.3+/-4.0%, CLENEX; and 36.8+/-12.4 to 26.4+/-7.9%, CLEN) and MHC type IIX increased (59.4+/-7.2 to 71.8+/-5.8%, CLENEX; and 50.5+/-12.5 to 62.0+/-9.3%, CLEN). Chronic clenbuterol administration with and without exercise resulted in a significant shift in MHC profile in Standardbred mares.