Effect of exercise intensity on bone density, strength, and calcium turnover in older women

PURPOSE: This study examined the effects of 24 wk of high intensity strength training or low intensity walking on lumbar bone mineral density (BMD), muscular strength, and calcium turnover in Australian women either taking hormone replacement therapy (HRT) or not taking HRT. METHODS: A subject pool of 64 women between 45-65 yr and randomly allocated into weights (N = 21), walking (N = 20), weightsHRT (N = 14), and walkingHRT (N = 9) groups completed this study. All subjects trained twice weekly in either a 50-min walking or weight-training program (60-90% IRM). Measurements included maximal isometric knee strength, IRM bench press, IRM squat, isokinetic back strength, lumbar (L2-L4) BMD, serum osteocalcin, and urinary deoxypyridinoline crosslinks (Dpd). RESULTS: No significant group differences in BMD were evident at the completion of training. However, a significant (P < 0.05) within group change was apparent for the walking group since BMD decreased 1.3% below baseline testing. Osteocalcin levels increased significantly (P < 0.05) in the walking (22%) group. Maximal bench press and squat strength improved significantly (P < 0.05) in the weights (25.8% and 37.7%) and weightsHRT (25.4% and 35.7%) groups. The weights group also increased significantly (P < 0.05) in isokinetic back strength (22.2%). CONCLUSION: It was concluded that short-term high intensity resistance training provides an effective means for increasing muscular strength in women between 45 and 65 yr. The training effects on lumbar BMD were not apparent in the present study.     

雌激素对骨钙、磷、羟脯氨酸含量和碱性磷酸酶活性的影响

 目的 研究雌激素在体外对骨形成的影响.方法 采用胚胎小鼠长骨培养模型,测定不同浓度雌酚酮对长骨钙、磷、羟脯氨酸含量和碱性磷酸酶活性的影响.结果 当培养介质中雌酚酮浓度为10-7 mol/L时,培养48 h后,长骨钙、磷、羟脯氨酸含量和碱性磷酸酶活性与对照组相比显著升高.结论 提示一定浓度的雌激素在体外可促进骨形成.     

Effect of short‐term heat acclimation with permissive dehydration on thermoregulation and temperate exercise performance

We examined the effect of short‐term heat acclimation with permissive dehydration (STHADe) on heat acclimation (HA) and cycling performance in a temperate environment. Ten trained male cyclists [mean (SD) maximal oxygen uptake: 63.3(4.0) mL/kg/min; peak power output (PPO): 385(40) W; training: 10 (3) h/week] underwent a STHADe program consisting of 5 days of exercise (maximum 90 min/day) in a hot environment (40 °C, 50% RH) to elicit isothermic heat strain [rectal temperature 38.64(0.27) °C]. Participants abstained from fluids during, and 30 min after, HA sessions. Pre‐ and post‐STHADe HA was evaluated during euhydrated fixed‐intensity exercise (60 min) in hot conditions; the effect of STHADe on thermoregulation was also examined under temperate conditions (20 min fixed‐intensity exercise; 22 °C, 60% RH). Temperate cycling performance was assessed by a graded exercise test (GXT) and 20‐km time trial (TT). STHADe reduced thermal and cardiovascular strain in hot and temperate environments. Lactate threshold [Δ = 16 (17) W] and GXT PPO [Δ = 6 (7) W] were improved following STHADe (P < 0.05), but TT performance was not affected (P > 0.05), although there was a trend for a higher mean power (P = 0.06). In conclusion, STHADE can reduce thermal and cardiovascular strain under hot and temperate conditions and there is some evidence of ergogenic potential for temperate exercise, but longer HA regimens may be necessary for this to meaningfully influence performance.     

Effects of voluntary exercise on bone growth and calcium metabolism in spontaneously hypertensive rats.

The effects of voluntary exercise on bone length and calcium metabolism were investigated in spontaneously hypertensive rats (SHR) and Wistar rats. They were classified into voluntary exercise or sedentary group. Systolic blood pressure (SBP), bone length, urinary calcium excretion, plasma calcium and parathyroid hormone levels (PTH) were measured for analysis. SBP of the trained SHR (T-SHR) was significantly lower than that of the nontrained SHR (NT-SHR) at 10 and 11 weeks of age, but the trained Wistar rats (T-WR) and the nontrained Wistar rats (NT-WR) had similar SBP throughout the experimental period. The T-SHR had significantly longer bones in the extremities and the trunk than the NT-SHR, whereas the T-WR had similar or shorter bones than the NT-WR. The PTH level at 12 weeks of age was significantly lower in the T-SHR than in the NT-SHR. The urinary calcium excretion of the T-SHR was greater than that of the NT-SHR, but the food intake (calcium intake) of the T-SHR was also greater. The urinary calcium excretion and food intake of the T-WR and NT-WR were similar. No noticeable differences were observed in the plasma calcium level between the T-SHR and NT-SHR, the T-WR and NT-WR. From these results it is suggested that the abnormal calcium metabolism in the SHR is improved in some degree by voluntary exercise.     

Effects of inactivity and exercise on bone

Bone mass and muscular mass show a parallel evolution during growth, and parallel involution with age. However, the bone loss related to the withdrawal of oestrogens is independent of muscular waste. The extensive study of disuse osteoporosis shows that exercise without weightbearing cannot counteract the loss of bone mass provoked by bed rest or weightlessness. Physical training, even at low frequency (30 to 60 min/day, 2 or 3 days/week), can increase bone mass or reduce bone loss associated with age. This effect is even present when exercise is practised by very old people at a seemingly low level of muscular tension on bone. It is not known whether muscular exercise could be helpful in pathological osteopenia. Experiments in animals indicate a short-lived benefit of exercise practised during a definite growth period; the long term effect of physical training in humans, after cessation of such activity, has not been studied extensively. Equal distribution of tension on all parts of the skeleton is probably not mandatory to obtain a general effect of exercise on bone mass. It is assumed that muscular exercise acts through tension exerted on bone, but the exact mechanism is unknown, as are the specifications of effective exercise in terms of site of application, intensity, frequency and duration. Moreover, little is known about the expected synergy between exercise and occupational activity.     

Effect of acute calcium slow-channel antagonism on the cardiorespiratory response to graded exercise testing

The effect of acute calcium slow-channel antagonism on the cardiorespiratory responses of 12 healthy males was studied during multistage maximal exercise testing. Oral diltiazem (60 mg), nifedipine (10 mg), verapamil (80 mg), and placebo were administered in a randomized double-blind crossover fashion 1.5 h before an intermittent multistage cycle ergometer exercise test. At peak effort, heart rate, pulmonary ventilation, CO2 production, and respiratory exchange ratio were not significantly modified by drug ingestion. In contrast, maximal O2 consumption (2.6% reduction, P less than 0.02) and performance time (6.4% reduction, P less than 0.02) were reduced by nifedipine. During submaximal exercise, the chronotropic response was accentuated by nifedipine but not by diltiazem or verapamil. Furthermore, nifedipine altered the relationship of percentage of maximal O2 consumption to percentage of maximal heart rate, and both the relative and absolute O2 consumption corresponding to 70% and 85% of the maximal heart rate were significantly reduced after nifedipine ingestion. The results indicated that in persons without symptomatic coronary artery disease exercise performed at a given percentage of the maximal heart rate will yield a lower than expected relative and absolute intensity in the presence of acute nifedipine-induced calcium slow-channel antagonism.     

Age does not influence the bone response to treadmill exercise in female rats

PURPOSE: Because it is believed that bone may respond to exercise differently at different ages, we compared bone responses in immature and mature rats after 12 wk of treadmill running. METHODS: Twenty-two immature (5-wk-old) and 21 mature (17-wk-old) female Sprague Dawley rats were randomized into a running (trained, P = 10 immature, 9 mature) or a control group (controls, P = 12 immature, 12 mature) before sacrifice 12 wk later. Rats ran on a treadmill five times per week for 60-70 min at speeds up to 26 m.min. Both at baseline and after intervention, we measured total body, lumbar spine, and proximal femoral bone mineral, as well as total body soft tissue composition using dual-energy x-ray absorptiometry (DXA). After sacrificing the animals, we measured dynamic and static histomorphometry and three-point bending strength of the tibia. RESULTS: Running training was associated with greater differences in tibial subperiosteal area, cortical cross-sectional area, peak load, stiffness, and moment of inertia in immature and mature rats (P < 0.05). The trained rats had greater periosteal bone formation rates (P < 0.01) than controls, but there was no difference in tibial trabecular bone histomorphometry. Similar running-related gains were seen in DXA lumbar spine area (P = 0.04) and bone mineral content (BMC; P = 0.03) at both ages. For total body bone area and BMC, the immature trained group increased significantly compared with controls (P < 0.05), whereas the mature trained group gained less than did controls (P < 0.01). CONCLUSION: In this model, where a similar physical training program was performed by immature and mature female rats, we demonstrated that both age groups were sensitive to loading and that bone strength gains appeared to result more from changes in bone geometry than from improved material properties.     

Effect of edetate calcium disodium on yttrium-90 activity in bone of mice

The kinetics of Yttrium-90 (Y-90) in bone of mice was investigated in combination with edetate calcium disodium (CaNa2EDTA). One group of mice were intraperitoneally administered 37.5 mg/kg CaNa2EDTA or 0.9% NaCl as a control at 1, 22, 34, 46, 58, 70, 82, 94, 154 and 166 h after injection of Y-90 acetate (post-administration), and the biodistribution was studied at 3, 24, 72, 120 and 168 h postinjection of Y-90 acetate. No difference between the post-CaNa2EDTA-treated mice and the control was demonstrated in the radioactivity in the bone. A decrease in radioactivity in the liver and kidneys was accelerated, and the radioactivity was lower than the control at 120 h postinjection. The other group of mice were also given the same dose of chelator at 12 h and 1 h preinjection of Y-90 acetate and at 1, 22, 34, 46, 58, 70, 82, 94, 154 and 166 h after injection of Y-90 acetate (pre- and post-administration), the radioactivity in bone at 3 h postinjection was significantly lower than in the control (24.4 +/- 3.92% ID/g vs. 31.7 +/- 2.26% ID/g, p < 0.05), but the decrease was not sequential. A significant reduction in radioactivity in the blood, kidneys and liver was demonstrated at 3 h, 72 h and 72 h postinjection. In conclusion, the CaNa2EDTA with the administration schedule employed here cannot chelate the Y-90 from bone but the free Y-90 before deposition into bone.     

Menopause, estrogen, and training effects on exercise hemodynamics: the HERITAGE study.

PURPOSE: To investigate the influences of menopause, hormone replacement, and endurance exercise training on cardiovascular hemodynamics and oxygen uptake parameters during exercise in women. METHODS: Subjects were 338 premenopausal women, 29 postmenopausal women taking hormone replacement, and 28 postmenopausal women not taking hormone replacement, all enrolled in the HERITAGE Family Study. Hemodynamic and oxygen uptake data were gathered on a cycle ergometer at 50 watts (W), 60% peak oxygen uptake, and at peak exercise, both before and after a 20-wk regimen of endurance exercise training on a cycle ergometer. RESULTS: Systolic blood pressure (SBP) during peak exercise was found to be an average of 14 mm Hg less in postmenopausal women receiving hormones than in those not receiving hormones. Furthermore, menopause was associated with a 26.2 mm Hg higher SBP at 50 W power output, which remained physiologically significant after adjustment for age. At 50 W, postmenopausal women not taking hormones showed a 13.8 mm Hg greater training-induced reduction in SBP than those taking hormones. CONCLUSION: It was concluded that hormone replacement may be associated with a vasodilatory reserve at high exercise intensities and that endurance exercise training elicits favorable hemodynamic and oxygen uptake adaptations during exercise that are, in most instances, independent of menstrual status or hormone replacement.     

Effect of Yi Jin Jing exercise plus Elastic Band Resistance exercise on overall bone mineral density in postmenopausal women

ObjectivesThis work aimed to study the effects of Yi Jin Jing plus Elastic Band Resistance exercise on bone mineral density at all parts of the body and bone metabolism index levels in postmenopausal women.DesignRandomized controlled trial.MethodsForty postmenopausal women were randomly assigned equally to the exercise or to the control group. The control group maintained their lifestyle behaviors unaltered, whereas the exercise group received Yi Jin Jing plus Elastic Band Resistance exercise. The primary outcome was overall bone mineral density at each part, and the secondary one was bone metabolism indicator levels and bone mineral density on both sides.ResultsThe results after six months showed increased bone mineral density at all parts of the body in the exercise group (spine, P = 0.002; thighs, lumbar, and whole body, P < 0.05) and decreased bone mineral density in the control group (trunk, pelvis, and spine, P < 0.01). In particular, the decrease and increase were greater on the non-preferred (left) side than on the right side. As for bone metabolism indexes, β-Crosslaps levels reduced (P = 0.016) and a significant increase in 1,25-(OH)2-D3 (P < 0.001) can be observed in the exercise group.ConclusionsThe results suggested that Yi Jin Jing plus Elastic Band Resistance exercise could delay the overall decrease of bone mineral density in postmenopausal women, especially on the non-preferred side. It also increased bone formation metabolite levels and inhibited bone resorption metabolite levels.     

Gastric emptying: influence of prolonged exercise and carbohydrate concentration

Gastric emptying: influence of prolonged exercise and carbohydrate concentration, Med. Sci. Sports Exerc., Vol. 21, No. 3, pp. 269-274, 1989. The purpose of this study was to examine the effects of serial feedings of different concentrations of carbohydrate (CHO) on gastric emptying and to compare the rates of gastric emptying at rest and during prolonged exercise. Solutions of 0, 6, 12, and 18 g. 100 ml-1 (WP, CHO-6, CHO-12, and CHO-18, respectively) were tested. Ten trained male cyclists performed five trials involving 120 min of cycling. The first 105 min were at 70% of VO2max, and the final 15 min were an all-out self-paced performance ride. In one of the five trials, the subjects rode intermittently, completing seven 15-min rides at 70% of VO2max, with 3 min of rest between each ride. Every 15 min, approximately 150 ml (8.5 ml.kg-1.h-1) of one of the four test solutions were consumed. (In the intermittent trial, the CHO-12 solution was used.) Subjects were also tested during 120 min of seated rest using the above feeding schedule (6% solution). Gastric residue was determined by stomach aspiration following the performance ride. The volumes emptied during the CHO-12 and CHO-18 trials (1,049.8 and 889.2 ml) were significantly different from each other and were less than during the WP and CHO-6 trials (1,210.3 and 1,185.6 ml) (P less than 0.05). CHO delivery was significantly higher in the CHO-12 and CHO-18 trials (126 and 160 g) compared to the CHO-6 trial (71.1 g).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of exercise training programme on bone mineral density in novice college rowers.

Exercise has important effects on skeletal mineralization. Changes in bone mineral density (BMD) and bone mineral content (BMC) as measured by dual energy X-ray absorptiometry were investigated in a group of 17 male novice college oarsmen over a 7-month period and were compared with eight age-matched controls. The rowing training programme consisted of approximately 8 h rowing, 1 h weight training, and 1 h running per week. After 7 months training the mean BMD of the lumbar spine (L1-L4) had increased significantly by 2.9% (P < 0.001) and the mean BMC had increased by 4.2% (P < 0.001). There was no significant change in the control group. Neither group showed a significant change in BMD or BMC in the femoral neck, greater trochanter or Ward's triangle. This study provides further evidence that exercise plays an important role in bone mineral formation.     

Effect of calcium channel blockers on vertebral bone marrow perfusion of the lumbar spine

PURPOSE: To investigate the effect of calcium channel blockers on blood perfusion of vertebral bone marrow in the lumbar spine. MATERIALS AND METHODS: Sixteen healthy volunteers (eight men and eight women) underwent dynamic contrast material-enhanced magnetic resonance (MR) imaging of the lumbar spine. One hundred twenty minutes after the first MR examination, each subject ingested 10 mg sublingual nifedipine before undergoing a second MR examination 20-25 minutes later. Semiquantitative (peak enhancement ratio and enhancement slope) and quantitative (amplitude and rate constant of the exchange [K(out)]) parameters were analyzed with the time-intensity curve. Data obtained before and after administration of nifedipine were compared. The Wilcoxon signed rank test and Spearman rank correlation test were used. RESULTS: Median peak enhancement ratio of vertebral bodies decreased from 0.60 (mean +/- SD, 0.68 +/- 0.29) to 0.51 (mean, 0.56 +/- 0.24) after administration of nifedipine. Median and mean decreases were 0.11 and 0.12 +/- 0.15, respectively, and the percentage difference was 17% (P =.005). A P value of less than.05 was considered to indicate a statistically significant difference. Median enhancement slope changed from 0.45 (mean, 0.45 +/- 0.13) to 0.41 (mean, 0.40 +/- 0.24). Median and mean changes were 0.05 and 0.04 +/- 0.23, respectively, and the percentage difference was 9% (P =.334). Median amplitude changed from 0.059 (mean, 0.059 +/- 0.028) to 0.045 (mean, 0.048 +/- 0.023). Median and mean changes were 0.008 and 0.011 +/- 0.025, respectively, and the percentage difference was 18% (P =.072). Median K(out) changed from 0.068 (mean, 0.063 +/- 0.018) to 0.067 (mean, 0.066 +/- 0.028). Median and mean changes were 0.011 and 0.004 +/- 0.028, respectively (P =.404). Nifedipine affected peak enhancement ratio significantly but did not affect enhancement slope, amplitude, or K(out). Data before and after administration of nifedipine showed no differences between men and women. Spearman rank correlation coefficients suggest no significance between the differences in heart rate and blood pressure and the differences in peak enhancement ratio, enhancement slope, amplitude, or K(out). CONCLUSION: After sublingual administration of nifedipine, the peak enhancement ratio of vertebral bone marrow decreased.     

Renal responses to bicycle exercise in trained athletes: influence of exercise intensity

The effects of exercise on renal function were studied in 11 male bicyclists, using a bicycle ergometer. At a work intensity of 100/150 W, bicycle exercise for 1 h was associated with a significant increase in urine volume, endogenous creatinine clearance, and renal sodium and potassium excretion. In contrast, exercise of the same duration at a work intensity of 150/200 W produced no significant changes in the above variables. Exercise intensity seems to influence renal responses, presumably through a differential effect on renal blood flow.     

Effect of simulated weightlessness on calcium metabolism and the condition of bone tissue in experimental animals

Male rats of the Wistar strain were for 40 days exposed to hypokinesia and hypodynamia. After exposure bone biochemical, physical, chemical, morphological and strength parameters were investigated. Both simulation studies led to changes in calcium and phosphorus metabolism but the nature of bone changes was different. It is concluded that the efficacy of drugs used as countermeasures in animal simulation experiments should be assessed by both exposures, viz. small size cages and suspension, because they reproduce different mechanisms of potential bone lesions in microgravity. It is also inferred that various countermeasures should be used in combination to yield the best results.