Exercise-related Effects Research Articles

Does walking exercise improve bone mineral density of young obese and thin women?

The purpose of the present study was to examine the effect of walking program on BMD in order to prevent bone loss among sedentary obese and thin young women. Forty untrained obese (n=20) and thin (n=20) women, 20-25 years, volunteered to participate in this study, then participants were pairwise BMI-matched and randomly assigned to two exercise (obese=10, thin=10) and two control (obese=10, thin=10) groups. Before and after the training program both groups had anthropometric measurements and blood analysis. Bone mass density also was evaluated by using dual-energy X-ray absorptiometry (DXA) .Each walking session was 30 min walking between 50-75% of maximal age adjusted heart rate, 3 days per week for 2 months. After 2 months, exercise groups had no significant effect on BMD at weight-bearing sites in the spine (L2-L4) and hip(p>0.05). However exercise groups experienced slightly increased in BMD at both region, while the control groups did not. Also no significant change was observed in blood samples in either group (p>0.05). Percent body fat, fat mass and lean mass were affected positively by the exercise program compared with control groups (all p = 0.000). This study demonstrated that walking exercise reduce the risk of bone loss in young women. However further studies are needed to evaluate the efficacy of walking exercise on bone quality and the risk of bone loss as an exercise-related effect in different obese and thin groups of women. Keywords: Bone Mass Density, Bone Loss, Walking Exercise, Obese and Thin Women.

On the emerging role of body culture and individualised exercise training for PPPM

On the emerging role of body culture and individualised exercise training for PPPM

The relative importance of genetics and phenotypic plasticity in dictating bone morphology and mechanics in aged mice: Evidence from an artificial selection experiment

Both genetic and environmental factors are known to influence the structure of bone, contributing to its mechanical behavior during, and adaptive response to, loading. We introduce a novel approach to simultaneously address the genetically mediated, exercise-related effects on bone morphometrics and strength, using mice that had been selectively bred for high levels of voluntary wheel running (16 generations). Female mice from high running and control lines were either allowed ( n=12, 12, respectively) or denied ( n=11, 12, respectively) access to wheels for 20 months. Femoral shaft, neck, and head were measured with calipers and via micro-computed tomography. Fracture characteristics of the femoral head were assessed in cantilever bending. After adjusting for variation in body mass by two-way analysis of covariance, distal width of the femur increased as a result of selective breeding, and mediolateral femoral diameter was reduced by wheel access. Cross-sectional area of the femoral mid-shaft showed a significant linetype × activity effect, increasing with wheel access in high-running lines but decreasing in control lines. Body mass was significantly positively correlated with many of the morphometric traits studied. Fracture load of the femoral neck was strongly positively predicted by morphometric traits of the femoral neck ( r 2>0.30), but no significant effects of selective breeding or wheel access were found. The significant correlations of body mass with femoral morphometric traits underscore the importance of controlling for body size when analyzing the response of bone size and shape to experimental treatments. After controlling for body mass, measures of the femoral neck remain significant predictors of femoral neck strength.

AMP activated protein kinase: a next generation target for total metabolic control

Metabolic syndrome is characterized by a cluster of metabolic disorders, such as reduced glucose tolerance, hyperinsulinemia, hypertension, visceral obesity and lipid disorders. The benefit of exercise in maintaining total metabolic control is well known and recent research indicates that AMP-activated protein kinase (AMPK) may play an important role in exercise-related effects. AMPK is considered as a master switch in regulating glucose and lipid metabolism. AMPK is an enzyme that works as a fuel gauge, being activated in conditions of high phosphate depletion. In the liver, activation of AMPK results in decreased production of plasma glucose, cholesterol, triglyceride and enhanced fatty acid oxidation. AMPK is also robustly activated by skeletal muscle contraction and myocardial ischemia, and is involved in the stimulation of glucose transport and fatty acid oxidation by these stimuli. In adipose tissue, activated AMPK inhibits deposition of fat, but enhances breakdown and burning of stored fat, resulting in reduction of body weight. The two leading diabetic drugs, namely metformin and rosiglitazone, and adipokines, such as adiponectin and leptin, show their metabolic effects partially through AMPK. These data suggest that AMPK may be a key player in the development of new treatments for obesity, Type 2 diabetes and the metabolic syndrome. In this review, the author provide insight into the role of AMPK as a probable target for treatment of metabolic syndrome.

Aerobic and Lung Performance in Premature Children With and Without Chronic Lung Disease of Prematurity

This study intended to identify pulmonary and exercise-related effects of chronic lung disease of infancy (CLD) versus prematurity (PRE) without CLD in children 5 to 7 years old who were born prematurely (24-30 weeks of gestation) with very low and extremely low birthweight of 500 to 1500 g (VLBW, ELBW). Seventeen CLD and 14 PRE were compared with 24 term controls (CON). The premature children had no overt manifestations of a neuromuscular disease. Pulmonary function at rest and following exercise, and aerobic exercise performance were measured. Peak [latin capital V with dot above]O2 and maximal aerobic power were not different among the groups, but O2 uptake at a given mechanical power was higher in the CLD than in PRE and in CON (P < 0.05). At rest, forced vital capacity was significantly lower in CLD than in PRE (P < 0.05) and CON (P < 0.0005), and FEV1 and FEF25-75 were lower in CLD than CON (P < 0.0005 and P < 0.005, respectively). Exercise-induced bronchoconstriction (EIB) was more prevalent among the 2 premature groups (P < 0.05). Our children 5 to 7 years old born at VLBW or ELBW, with or without CLD, have some degree of pulmonary dysfunction at rest and following exercise and a higher prevalence of EIB with no reduction in maximal aerobic exercise performance. The findings suggest that the pulmonary limitations are associated with low birthweight even in the absence of CLD. The higher O2 uptake at a given mechanical power in the CLD group may cause early fatigability during prolonged exercise, even when aerobic performance is normal.

The effects of physical exercise on plasma prebeta-1 high-density lipoprotein

The impact of physical exercise on high-density lipoprotein (HDL) metabolism is recognized as a major mechanism of coronary artery disease (CAD) risk reduction. Prebeta-1 HDL subparticle species play a pivotal role in initiating reverse cholesterol transport (RCT). We examined the effect of acute physical exercise on plasma prebeta-1 HDL levels. Nineteen nonsmoking, healthy men (n = 11) and women (n = 8) not receiving lipid-altering medications completed dietary surveys, and had percent body fat determinations, and fasting blood drawn for measurements of plasma lipids, lipoproteins, apolipoprotein A-I (Apo A-I), and absolute and percent prebeta-1 HDL. Each subject completed cardiopulmonary exercise stress testing to Vo2max followed by a 4-km course of run-jogging. Laboratory measurements were repeated from blood drawn immediately after exercise. Mean ± SD values were determined for age, percent body fat, dietary calories, dietary cholesterol, dietary fat, and plasma lipids, lipoproteins, Apo A-I, and absolute and percent prebeta-1 HDL using 1-way analysis of variance (ANOVA). One-way ANOVA comparisons were made for measurements of plasma lipids, lipoproteins, Apo A-I, and absolute and percent prebeta HDL measurements taken before and after exercise for all subjects combined. Entry characteristics showed the following (mean ±SD): age, 24 ± 5.8 years; body mass index (BMI), 22.4 ± 2.6; percent body fat, 13 ± 5.7; and Vo2max, 49.1 ± 7.9 mL O2/kg/min. Exercise significantly increased absolute plasma prebeta HDL (0.10 ± 0.05 to 0.130 ± 0.07 μg/mL, P =.039) and decreased plasma HDL-triglycerides (23.3 ± 10.8 to 12.5 ± 5.6 mg/dL, P =.012). Our findings indicate that prebeta-1 HDL and HDL-triglyceride metabolism are significant components of the effect of acute exercise on RCT. These findings have important relevance for studies pertaining to exercise-related effects on HDL metabolism as pertains to CAD risk reduction. Copyright 2003 Elsevier, Inc. All rights reserved.

Nutrition and sport

Nutrition and sport

Running and ovulation positively change cancellous bone in premenopausal women.

Exercise is understood to exert positive effects on bone. However cancellous bone has not been shown to increase with exercise. Previous results of our 1-yr observational prospective study in ovulatory women related 20% of the change in cancellous spinal bone mineral density (BMD), measured by quantitative computed tomography (QCT), to luteal phase length (the time from ovulation to menstruation, LL). The 66 women who documented exercise daily included normally active women (N = 23) and those who ran consistently or were increasing running in preparation for a marathon (N = 43). Exercise did not affect BMD change in the women as a whole. We re-evaluated those data to determine whether exercise-related effects on spinal cancellous BMD change in regularly cycling premenopausal women were related to ovulatory characteristics. The potential relationship of exercise to BMD change was reanalyzed by stratifying women into tertiles according to average LL documented by quantitative basal temperature analysis. Repeated-measures ANOVA indicated independent positive effects of both luteal length (P = 0.001) and activity (P = 0.041). The 11 runners with LL > 10.9 d had a nonsignificant 0.5% increase in lumbar BMD while the 15 who averaged short LL (<9.9 d) experienced a significant 3.6% loss. In the runners as a group, however, kilometers run per week was negatively related to BMD change throughout (r = -0.347, P = 0.024). These data are the first to indicate that, in women with regular cycles, luteal length and exercise independently and positively affect change in spinal cancellous BMD.

Changes in VO2max, physical activity, and body fat with chronic exercise: effects on plasma lipids.

The effect of changes in physical activity levels during chronic exercise on plasma lipids and lipoproteins has not been reported. We examine the relationships between changes in VO2max, leisure time physical activity (LTPA), and percent body fat on changes in plasma lipids and lipoproteins in 137 men without coronary artery disease (CAD) and/or dyslipidemia, hypertension, or diabetes mellitus who participated in an employee exercise program. Measurements obtained at entry and 1- and 4-yr follow-up include VO2max, LTPA in kcal.wk-1, percent body fat, and plasma lipids and lipoproteins. The relationship between changes in the measurements between 1 and 4 yr of follow-up (N = 34) revealed the following significant (P < 0.05) correlations: i) changes in VO2max with changes in percent body fat (r = -0.289) and changes in plasma triglycerides (r = -0.354), ii) changes in LTPA with changes in percent body fat (-0.361), and iii) changes in percent body fat with changes in the total/high density lipoprotein (HDL)-cholesterol ratio (0.358), HDL-cholesterol (-0.212), and triglycerides (0.289). Multiple regression analysis revealed that changes in percent body fat affected changes in plasma triglycerides (P < 0.05). The effects of chronic physical activity on plasma triglycerides appear to result from exercise-related effects on body adiposity. These findings support the role of regular physical activity as mandated by Healthy People 2000 for CAD risk reduction.

Myotrophic effects of anabolic steroids.

An anabolic steroid, nandrolone decanoate, was shown to produce increases in the weight, cross-sectional area, tension-generating capacity and mean fibre diameter of a limb muscle, tibialis anterior (TA), in female rabbits. Despite suggestions in the literature of an exerciserelated effect of such drugs, hypertrophy was not observed in TA muscles subjected to chronic electrical stimulation, but was seen in the contralateral control muscles and in the muscles of both hind limbs in unoperated sedentary animals. The effect was confirmed in the TA of female guinea pigs, rats and mice, and could not be explained in terms of an increase in body weight. Compared to TA some other muscles, like EDL, plantaris and soleus in the rabbit, were less sensitive to treatment; others, like pubocaudalis in the rat and mouse, and temporalis in the guinea pig, were more responsive. The myotrophic effects were undiminished in adrenalectomised female rats, and could not therefore have been mediated by interference with the catabolic actions of circulating glucocorticoids, as had been proposed in an earlier hypothesis.