l Exercise Training and Body Composition Training

Exercise and Body Comp l Adaptations to exercise training depend on many interrelated factors: l initial level of training, l gender, l body fat levels and distribution, l age, l genetic makeup.

Conundrum l Most research has been conducted over a short period of time (i.e., 8 to 20 weeks). l Most effects manifest themselves over an extended period of time.

Exercise and Body Comp l Using short term studies to predict long term results is problematic since the changes are likely to be exponential in nature and eventually plateau.

Exercise and Body Comp l Cross-sectional comparisons between habitual exercisers and sedentary individuals provide some insight as to how long-term exercise training may affect body composition, but these comparisons suffer from self-selection bias.

Exercise and Body Comp l Since exercise training-induced changes in body composition are dependent on various external factors (e.g., gender, age, genetic makeup), changes in body composition following an exercise training program vary greatly.

Exercise and Body Weight l In general, loss of body weight in an exercise program is more likely if the initial body weight in an exercise program is markedly greater than the desired level, the person is sedentary, and there is a high percentage of fat in the diet.

Exercise and Body Weight l In males, exercise-induced changes in body weight are more closely correlated with weekly exercise energy expenditure (r = -.61) than with either the number of exercise sessions per week (r = -.32) or minutes per session (r = -.37).

Exercise and Body Weight l For women, the correlations were much lower for all indices of energy expenditure (weekly exercise energy expenditure, r =.03; sessions per week, r = -.19; minutes per session, r = -.16) and were statistically nonsignificant (p >.05), suggesting that men and women respond differently to exercise training.

Exercise and Body Weight l Exercise intensity does not appear to affect the rate at which weight is lost.

Exercise and Body Weight l The loss of weight due to participation in an exercise training program is related to the degree to which one is overweight.

Exercise and Body Weight l Older women may be more likely to lose weight in response to an exercise training program than younger women.

Exercise and Body Weight l A lifetime of regular physical activity can minimize weight gain, or conversely, older adults who are overweight are likely to lose weight in response to exercise training.

Summary l The response of body weight to aerobic exercise training appears to be quite variable, with males more likely to lose weight in response to the initiation of an exercise training program than females.

Summary l A loss of body weight is also more likely for individuals who are overfat.

Summary l The loss of weight in response to an exercise training program appears to be more dependent on total energy expenditure than on the frequency, duration, and intensity of the exercise.

Exercise and Fat Mass l Most of the weight lost with aerobic training is fat. l In addition, most of the variability between subjects in exercise-induced changes in body weight are related to differences in the loss of fat.

Exercise and Fat Mass l This may be due in part to differences among individuals with respect to the number, type, and distribution of adipocytes.

Exercise and Fat Mass l The response of body fat to exercise training depends on adipocyte morphology and function.

Exercise and Fat Mass l Exercise training seems able to induce reductions in adipocyte volumes to some “floor” level, and therefore body weight commonly stabilizes at a lower value after an exercise training program. l Set Point Theory

Exercise and Fat Mass l An exercise training program will have only small effects on the total body fat of individuals in whom adipocyte volume is near the “floor” level at the initiation of the program.

Exercise and Fat Mass l Losses in body fat with exercise training may be proportional to the increase in exercise energy expenditure until adipocyte volumes are reduced to a threshold level.

Exercise and Fat Mass l At this point, dietary intake will increase to maintain a constant adipocyte volume and body weight.

Exercise and Fat Mass l Since the number of adipocytes varies among individuals, stabilization can occur at a variety of body weights and %BF levels.

Exercise and Fat Mass l These reductions in fat mass with continued exercise training seem to occur over extended periods of time.

Exercise and Fat Mass l Some research has shown that fat mass decreases more rapidly during the first seven months of training and then slows over time.

Body Composition Questions Why is exercise an essential part of fat-loss programs? l Increases E expenditure. l Creates a negative E balance. l Retains muscle tissue. l Increases use of fat as a fuel. l Hormone secretion.

Body Composition Questions How does improved CV fitness help control body composition? l Can accomplish more work. l Use fat as a primary fuel source.

Body Composition Questions What effect does exercise have on the resting metabolic rate? l Increases RMR. l Increases post-exercise MR.

Body Composition Questions Is aerobic exercise better than resistance exercise for fat loss? l Resistance training may be as effective as aerobic training in fat-loss programs. l Both should make-up a fat-loss program.

Body Composition Questions Is high-intensity exercise better than low- intensity exercise for fat loss? l The duration of the exercise and total distance is much more important than the speed (intensity) of exercise for maximizing the energy expenditure.

Body Composition Questions Are spot reduction exercises effective for decreasing body fat in localized regions of the body? l No. l The regional distribution and mobilization of adipose tissue appears to follow a biologically selective pattern regardless of type of exercise.

Summary l Aerobic exercise training induces reductions in total fat mass, and the size of the reduction is related to the total weekly energy expenditure via exercise.

Summary l Body fat is reduced with training until total energy expenditure and total energy intake are equal.

Summary l Body fat levels are much more likely to be reduced following exercise training for those individuals with large adipocytes.

Summary l Young men are more likely to lose fat mass with exercise training than are young women.

Summary l Older women may be more likely to lose body fat with exercise training than younger women. l Fat retention role of estrogen?

Summary l The age-related increase in body fat during adulthood seems to be strongly related to reductions in exercise training volume.

Summary l Older people are more likely to lose body fat with the onset of an exercise training program, mostly because they tend to have more body fat.

Exercise and FFM l Aerobic exercise training results in modest increases in FFM.

Exercise and FFM l Much larger increases are possible with weight training, but the time course of these changes has not been well studied.

Exercise and FFM l Neither age nor gender appears to differentially affect exercise training- induced changes in FFM, but the magnitude of the increases in FFM with training may be diminished with advancing age due to the concomitant reduction in the number of muscle fibers and levels of hormone secretion.

Exercise and Bone Mass l Bone mineral mass increases in response to specific stresses.

Exercise and Bone Mass l The greater the stresses on a given bone, the greater the likelihood of an increase in bone mineral mass.

Exercise and Bone Mass l Weight bearing and/or resistive training exercises are more likely to result in an increase in bone mineral mass since they induce greater stresses on bone than activities such as swimming or cycling.

Exercise and Bone Mass l A review of the literature suggests that while exercise training is commonly associated with an increase in bone mineral density, the adaptations are site-specific.

Exercise and Bone Mass l Long-term intervention studies, while few in number, suggest that exercise training can increase bone mineral mass and/or slow the rate of bone mineral loss associated with aging.