Moderator: Megan Lieff
J Appl Physiol 89: 81-88, 2000;
Vol. 89, Issue 1, 81-88, July 2000
Skeletal muscle mass and distribution in 468 men and women aged 18-88 yr
Ian Janssen1, Steven B. Heymsfield2, ZiMian Wang2, and Robert Ross
1 School of Physical and Health Education, Queen's University, Kingston, Ontario, Canada K7L 3N6; and 2 Obesity Research Center, St. Luke's/Roosevelt Hospital, Columbia University, College of Physicians and Surgeons, New York, New York 10025
We employed a whole body magnetic resonance imaging protocol to examine the influence of age, gender, body weight, and height on skeletal muscle (SM) mass and distribution in a large and heterogeneous sample of 468 men and women. Men had significantly (P < 0.001) more SM in comparison to women in both absolute terms (33.0 vs. 21.0 kg) and relative to body mass (38.4 vs. 30.6%). The gender differences were greater in the upper (40%) than lower (33%) body (P < 0.01). We observed a reduction in relative SM mass starting in the third decade; however, a noticeable decrease in absolute SM mass was not observed until the end of the fifth decade. This decrease was primarily attributed to a decrease in lower body SM. Weight and height explained ~50% of the variance in SM mass in men and women. Although a linear relationship existed between SM and height, the relationship between SM and body weight was curvilinear because the contribution of SM to weight gain decreased with increasing body weight. These findings indicate that men have more SM than women and that these gender differences are greater in the upper body. Independent of gender, aging is associated with a decrease in SM mass that is explained, in large measure, by a decrease in lower body SM occurring after the fifth decade.
J Appl Physiol 71: 644-650, 1991;
Journal of Applied Physiology, Vol 71, Issue 2 644-650, Copyright © 1991 by American Physiological Society
A cross-sectional study of muscle strength and mass in 45- to 78-yr-old men and women
W. R. Frontera, V. A. Hughes, K. J. Lutz and W. J. Evans
Human Physiology Laboratory, Tufts University, Boston, Massachusetts 02111.
The isokinetic strength of the elbow and knee extensors and flexors was measured in 200 healthy 45- to 78-yr-old men and women to examine the relationship between muscle strength, age, and body composition. Peak torque was measured at 60 and 240 degrees/s in the knee and at 60 and 180 degrees/s in the elbow by use of a Cybex II isokinetic dynamometer. Fat-free mass (FFM) was estimated by hydrostatic weighing in all subjects, and muscle mass (MM) was determined in 141 subjects from urinary creatinine excretion. FFM and MM were significantly lower (P less than 0.001) in the oldest group. Strength of all muscle groups at both testing speeds was significantly (P less than 0.006) lower (range 15.5-26.7%) in the 65- to 78- than in the 45- to 54-yr-old men and women. When strength was adjusted for FFM or MM, the age-related differences were not significant in all muscle groups except the knee extensors tested at 240 degrees/s. Absolute strength of the women ranged from 42.2 to 62.8% that of men. When strength was expressed per kilogram of MM, these gender differences were smaller and/or not present. These data suggest that MM is a major determinant of the age- and gender-related differences in skeletal muscle strength. Furthermore, this finding is, to a large extent, independent of muscle location (upper vs. lower extremities) and function (extension vs. flexion).
Eur J Appl Physiol Occup Physiol. 1993;66(3):254-62.
Gender differences in strength and muscle fiber characteristics.
Miller AE, MacDougall JD, Tarnopolsky MA, Sale DG.
Department of Physical Education, McMaster University, Hamilton, Ontario, Canada.
Strength and muscle characteristics were examined in biceps brachii and vastus lateralis of eight men and eight women. Measurements included motor unit number, size and activation and voluntary strength of the elbow flexors and knee extensors. Fiber areas and type were determined from needle biopsies and muscle areas by computerized tomographical scanning. The women were approximately 52% and 66% as strong as the men in the upper and lower body respectively. The men were also stronger relative to lean body mass. A significant correlation was found between strength and muscle cross-sectional area (CSA; P < or = 0.05). The women had 45, 41, 30 and 25% smaller muscle CSAs for the biceps brachii, total elbow flexors, vastus lateralis and total knee extensors respectively. The men had significantly larger type I fiber areas (4597 vs 3483 microns2) and mean fiber areas (6632 vs 3963 microns2) than the women in biceps brachii and significantly larger type II fiber areas (7700 vs 4040 microns2) and mean fiber areas (7070 vs 4290 microns2) in vastus lateralis. No significant gender difference was found in the strength to CSA ratio for elbow flexion or knee extension, in biceps fiber number (180,620 in men vs 156,872 in women), muscle area to fiber area ratio in the vastus lateralis 451,468 vs 465,007) or any motor unit characteristics. Data suggest that the greater strength of the men was due primarily to larger fibers. The greater gender difference in upper body strength can probably be attributed to the fact that women tend to have a lower proportion of their lean tissue distributed in the upper body.(ABSTRACT TRUNCATED AT 250 WORDS)
Shana Moore wrote:of course the "but" to that train of thought is to be aware of your weaknesses and train to offset them as muuch as possible
Largely out of necessity, I have reinforced and learned this strength-technique difference , which is somewhat optional in the strong adolescent and adult males--who seem to exert their force with just the use of their arm/shoulder/upper back.
I find no drop out rate difference between men and women..
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