High intensity exercise during pregnancy of rats. Effects on mother and offspring

We see in this study the effect of high intensity exercise (90% VO₂ max) in pregnant rats and their offspring depending on the length of pregnancy. The findings were compared with those obtained for sedentary pregnant rats and non-pregnant rats for similar exercise. This allowed for analysing the isolated effects of exercise (against the sedentary non-pregnant rat control group), of pregnancy and of the interaction between the two factors. For checking the effect of the length of pregnancy, each group of rats was subdivided into those with pregnancy terminated or sacrificed on the seventh, fourteenth or twentieth day of the experiment. VO₂ max, post-exertion blood lactic acid level, body weight gain, food intake, feed efficiency, glucose, triglyceride, total cholesterol, total protein and albumin plasmatic concentrations in adult rats, and weight and number of offspring of pregnant rats were determined. Pregnancy increased weight gain and feed efficiency from the first week of the study, accompanied by a greater food intake (from the twelfth day). In the group of pregnant rats subjected to exercise, there was a reduction in weight gain percentage and feed efficiency in the first and third weeks, staying the same in the second week. A greater food intake during the period accompanied this recovery in the second week. In the group of non-pregnant rats subjected to exercise, food intake did not vary. As the weight gain percentage was less in relation to the non-pregnant control group, feed efficiency decreased. Pregnancy induced a drop in blood sugar level starting in the second week, and the exercise performed during pregnancy did not change this behavior. Pregnancy produced, however, an increase in plasmatic concentration of triglycerides and total cholesterol during the third week of pregnancy. Exercise performed by pregnant rats also did not change this behavior, but the increase observed in the third week was less. Exercise performed by non-pregnant rats did not change the blood sugar level and plasmatic concentration of triglycerides and total cholesterol during the entire experiment. Plasmatic concentration of total proteins and albumin showed a drop in the third week of pregnancy, probably due to high fetal use of proteins in this stage. Exercise performed by the pregnant group caused a lower protein drop in the third week, and in the non-pregnant group, determined an increase in plasmatic protein concentrations. The weight of the offspring of mother rats exercised until the end of the second and third weeks of pregnancy was found to be reduced in relation to the sedentary pregnant group. The group exercised until the third week showed a reduction in the number of offspring, indicating a possible fetal reabsorption. These findings confirmed that high intensity exercise can produce deleterious effects on the mother and fetus, especially when applied up to the last stage of pregnancy.     

强度不同的间歇跑台训练对生长期大鼠骨代谢及相关激素的影响

目的:探讨强度不同的间歇跑台训练对生长期大鼠骨代谢的影响,以期为青少年训练强度的制定提供理论支持。方法:选取4周龄雄性wistar大鼠70只,根据体重随机搭配分成7组(n=10):即对照组和运动组。运动组按照大鼠摄氧量分为:65%组,70%组,75%组,80%组,85%组和90%组。跑台训练9周,每周训练6 d,每组训练分3次,每次不低于10 min,中间间隔30 min。最后一次运动后24 h,取股骨和血进行骨密度(BMD)、骨量(BMC)和血清中的碱性磷酸酶(AKP),抗酒石酸酸性磷酸酶(Str-ACP)的测定。结果:①70%组股骨的BMD(0.1393±0.0031)、BMC(0.4525±0.0335)显著高于对照组(BMD:0.1200±0.0095,BMC:0.3238±0.0485)和其他各运动组(65%组BMD:0.1339±0.0062、BMC:0.4058±0.0492,75%组BMD:0.1296±0.0015、BMC:0.3869±0.0254,80%组BMD:0.1223±0.0082、BMC:0.3454±0.0483,85%组BMD:0.1250±0.0044、BMC:0.3731±0.0381,90%组BMD:0.1171±0.0047、BMC:0.3051±0.0286)(P<0.05),90%组的BMD、BMC低于对照组但未达到显著水平,其他各运动组均高于对照组;②各运动组血清AKP均显著高于对照组,其中65%组(41.015±2.114)、70%组(46.035±2.611)、75%组(43.834±3.155)、80%组(38.043±4.073)血清AKP非常显著高于对照组(26.875±1.188)(P<0.01),70%组和75%组血清AKP显著高于80%组、85%组、90%组(P<0.05),同时70%组血清AKP显著高于65%组(P<0.05),这说明70%VO2max的训练强度成骨细胞最活跃。各运动组血清StrACP均显著高于对照组,随着训练强度的增加,血清StrACP水平呈上升趋势,80%组(22.430±1.591)、85%组(23.990±1.870)、90%组(28.009±1.839)血清StrACP显著高于65%组(18.503±2.429)、70%组(16.447±2.120)和75%组(17.769±1.642)(P<0.05),90%组血清StrACP均显著高于80%组和85%组(P<0.05)。结论:70%VO2max的中等强度间歇跑台训练使生长期大鼠骨量、骨密度增加最明显。     

Effect of work load on cutaneous vascular response to exercise.

The purpose of the present study was to examine whether intensity of exercise affects skin blood flow response to exercise. For this purpose, six healthy men cycled, in a random order on different days, for 15 min at 50, 60, 70, 80, and 90% of their maximum oxygen consumption (VO2max) at a room temperature of 25 degrees C. At the end of exercise, esophageal temperature (Tes) averaged 37.4 +/- 0.2, 37.7 +/- 0.2, 37.9 +/- 0.2, 38.6 +/- 0.3, and 38.9 +/- 0.4 degrees C (SE) at the 50, 60, 70, 80, and 90% work loads, respectively. At the two highest work loads, no steady state was observed in Tes. Skin blood flow was estimated by measuring forearm blood flow (FBF) with strain-gauge plethysmography and by laser-Doppler flowmetry on the upper back. Both techniques showed that skin blood flow response to rising Tes was markedly reduced at the 90% work load compared with other work loads. At the end of exercise, FBF averaged 7.5 +/- 1.7, 10.7 +/- 3.1, 9.6 +/- 2.1, 11.3 +/- 2.6, and 5.4 +/- 1.3 (SE) ml.min-1.100 ml-1 (P less than 0.01) at the 50, 60, 70, 80, and 90% VO2max work loads, respectively. The corresponding values for Tes threshold for cutaneous vasodilation (FBF) were 37.42 +/- 0.16, 37.48 +/- 0.13, 37.59 +/- 0.13, 37.79 +/- 0.19, and 38.20 +/- 0.22 degrees C (P less than 0.05) at 50, 60, 70, 80, and 90% VO2max, respectively. In two subjects, no cutaneous vasodilation was observed at the 90% work load.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of maternal weight gain during pregnancy on exercise performance

We examined the effect of maternal weight gain during pregnancy on exercise performance. Ten women performed submaximal cycle (up to 60 W) and treadmill (4 km/h, up to 10% grade) exercise tests at 34 +/- 1.5 (SD) wk gestation and 7.6 +/- 1.7 wk postpartum. Postpartum subjects wearing weighted belts designed to equal their body weight during the antepartum tests performed two additional treadmill tests. Absolute O2 uptake (VO2) at the same work load was higher during pregnancy than postpartum during cycle (1.04 +/- 0.08 vs. 0.95 +/- 0.09 l/min, P = 0.014), treadmill (1.45 +/- 0.19 vs. 1.27 +/- 0.20 l/min, P = 0.0002), and weighted treadmill (1.45 +/ 0.19 vs. 1.36 +/- 0.20 l/min, P = 0.04) exercise. None of these differences remained, however, when VO2 was expressed per kilogram of body weight. Maximal VO2 (VO2max) estimated from the individual heart rate-VO2 curves was the same during and after pregnancy during cycling (1.96 +/- 0.37 to 1.98 +/- 0.39 l/min), whereas estimated VO2max increased postpartum during treadmill (2.04 +/- 0.38 to 2.21 +/- 0.36 l/min, P = 0.03) and weighted treadmill (2.04 +/- 0.38 to 2.19 +/- 0.38 l/min, P = 0.03) exercise. We conclude that increased body weight during pregnancy compared with the postpartum period accounts for 75% of the increased VO2 during submaximal weight-bearing exertion in pregnancy and contributes to reduced exercise capacity. The postpartum increase in estimated VO2max during weight-bearing exercise is the result of consistently higher antepartum heart rates during all submaximal work loads.     

Sex differences in endurance capacity and metabolic response to prolonged, heavy exercise

In order to test for possible sex differences in endurance capacity, groups of young, physically active women (n = 6) and men (n = 7) performed bicycle ergometer exercise at 80% and 90% of their maximal oxygen uptakes (VO2 max). The groups were matched for age and physical activity habits. At 80% VO2 max the women performed significantly longer (P less than 0.05), 53.8 +/- 12.7 min vs 36.8 +/- 12.2 min, respectively (means +/- SD). Mid-exercise and terminal respiratory exchange ratio (R) values were significantly lower in women, suggesting a later occurrence of muscle glycogen depletion as a factor in their enhanced endurance. At 90% VO2 max the endurance times were similar for men and women, 21.2 +/- 10.3 min and 22.0 +/- 5.0 min, respectively. The blood lactate levels reached in these experiments were only marginally lower (mean differences 1.5 to 2 mmol X l-1) than those obtained at VO2 max, suggesting high lactate levels as a factor in exhaustion. The changes in body weight during the 80% experiments and the degree of hemoconcentration were not significantly different between men and women.     

Lower extremity muscle size and strength and aerobic capacity decrease with caloric restriction but not with exercise-induced weight loss.

Caloric restriction (CR) results in fat loss; however, it may also result in loss of muscle and thereby reduce strength and aerobic capacity (VO2 max). These effects may not occur with exercise-induced weight loss (EX) because of the anabolic effects of exercise on heart and skeletal muscle. We tested the hypothesis that CR reduces muscle size and strength and VO2 max, whereas EX preserves or improves these parameters. Healthy 50- to 60-yr-old men and women (body mass index of 23.5-29.9 kg/m2) were studied before and after 12 mo of weight loss by CR (n = 18) or EX (n = 16). Lean mass was assessed by dual-energy X-ray absorptiometry, thigh muscle volume by MRI, isometric and isokinetic knee flexor strength by dynamometry, and treadmill VO2 max by indirect calorimetry. Both interventions caused significant decreases in body weight (CR: -10.7 +/- 1.4%, EX: -9.5 +/- 1.5%) and lean mass (CR: -3.5 +/- 0.7%, EX: -2.2 +/- 0.8%), with no significant differences between groups. Significant decreases in thigh muscle volume (-6.9 +/- 0.8%) and composite knee flexion strength (-7.2 +/- 3%) occurred in the CR group only. Absolute VO2 max decreased significantly in the CR group (-6.8 +/- 2.3%), whereas the EX group had significant increases in both absolute (+15.5 +/- 2.4%) and relative (+28.3 +/- 3.0%) VO2 max. These data provide evidence that muscle mass and absolute physical work capacity decrease in response to 12 mo of CR but not in response to a similar weight loss induced by exercise. These findings suggest that, during EX, the body adapts to maintain or even enhance physical performance capacity.     

Characterization of exercise-induced hyperketonemia in streptozotocin-diabetic rats and the effects on it of prolonged training

Exercise-induced hyperketonemia was investigated using streptozotocin (STZ)-diabetic rats subjected to running exercise on a treadmill. The degrees of hyperketonemia after 50, 55 and 60% VO2max of exercises were similar in mild diabetic rats (fasting plasma glucose; FPG less than 11 mM). The degree of hyperketonemia (especially an increase in acetoacetate; AcAc) after 60% VO2max of exercise was correlated with FPG (P less than 0.01) and basal plasma ketone bodies (P less than 0.01). Prolonged training with 60% VO2max of exercise for 30 min 3 times per week for 6 wks reduced the increase in plasma ketone bodies induced by the exercise in both mild (FPG less than 11 mM) and severe (FPG greater than 22 mM) diabetic rats. The exercise-induced increase in plasma glucagon in mild diabetic rats and free fatty acids (FFA) in severe diabetic rats are also reduced by the training. These results demonstrate that exercise-induced hyper-AcAc-emia correlated with the FPG level is reduced by prolonged training in diabetic rats, and might suggest that exercise-induced hyperketonemia is reduced by long-term exercise training also in diabetic patients.     

A program of moderate physical training for Wistar rats based on maximal oxygen consumption

Moderate physical training is often associated with improved cardiorespiratory fitness in athletes and the general population. In animals, studies are designed to investigate basic physiology that could be invasive and uncomfortable for humans. The standardization of an exercise training protocol for rats based on maximal consumption of oxygen (VO(2)max) is needed. This study validated a program of moderate physical training for Wistar rats based on VO(2)max determined once a week. A 10-stage treadmill running test was developed to measure VO(2)max through an indirect, open circuit calorimeter. Thirty male Wistar rats (210-226 g) were randomly assigned to either a nontrained group or a trained group. The animals were evaluated weekly to follow their VO(2)max during 8 weeks of moderate training and to adjust the intensity of the protocol of training. The soleus muscle was removed for determination of citrate synthase activity. Trained animals maintained their values of VO(2)max during a moderate running training and showed a significant less body weight gain. An increase of 42% in citrate synthase activity of the soleus muscle from trained rats was found after the training program. Our study presents a protocol of moderate physical training for Wistar rats based on VO(2)max. Peripheral adaptations such as the values of citrate synthase activity also responded to the moderate training program imposed as observed for VO(2)max. Other studies can use our protocol of moderate training to study the physiologic adaptations underlying this specific intensity of training. It will provide support for study with humans.     

Response of ventilatory and lactate thresholds to continuous and interval training

The purpose of this study was to evaluate the effects of continuous and interval training on changes in lactate and ventilatory thresholds during incremental exercise. Seventeen males were assigned to one of three training groups: group 1:55 min continuous exercise at approximately 50% maximum O2 consumption (VO2max); group 2: 35 min continuous exercise at approximately 70% VO2max; and group 3: 10 X 2-min intervals at approximately 105% VO2max interspersed with rest intervals of 2 min. All of the subjects were tested and trained on a cycle ergometer 3 day/wk for 8 wk. Lactate threshold (LT) and ventilatory threshold (VT) (in addition to maximal exercise measures) were determined using a standard incremental exercise test before and after 4 and 8 wk of training. VO2max increased significantly in all groups with no statistically significant differences between the groups. Increases (+/- SE) in LT (ml O2 X min-1) for group 1 (569 +/- 158), group 2 (584 +/- 125), and group 3 (533 +/- 88) were significant (P less than 0.05) and of the same magnitude. VT also increased significantly (P less than 0.05) in each group. However, the increase in VT (ml O2 X min-1) for group 3 (699 +/- 85) was significantly greater (P less than 0.05) than the increases in VT for group 1 (224 +/- 52) and group 2 (404 +/- 85). For group 1, the posttraining increase in LT was significantly greater than the increase in VT (P less than 0.05). We conclude that both continuous and interval training were equally effective in augmenting LT, but interval training was more effective in elevating VT.(ABSTRACT TRUNCATED AT 250 WORDS)     

Angiotensin-converting enzyme ID polymorphism and fitness phenotype in the HERITAGE Family Study.

It has been suggested that genetic variation in the angiotensin-converting enzyme (ACE) gene is associated with physical performance. We studied the association between the ACE insertion (I)/deletion (D) polymorphism and several fitness phenotypes measured before and after 20 wk of a standardized endurance training program in sedentary Caucasian (n = 476) and black (n = 248) subjects. Phenotypes measured were oxygen uptake (VO(2)), work rate, heart rate, minute ventilation, tidal volume, and blood lactate levels during maximal and submaximal [50 W and at 60 and 80% of maximal VO(2) (VO(2 max))] exercise and stroke volume and cardiac output during submaximal exercise (50 W and at 60% VO(2 max)). The ACE ID polymorphism was typed with the three-primer PCR method. Out of 216 association tests performed on 54 phenotypes in 4 groups of participants, only 11 showed significant (P values from 0.042 to 0. 0001) associations with the ACE ID polymorphism. In contrast to previous claims, in Caucasian offspring, the DD homozygotes showed a 14-38% greater increase with training in VO(2 max), VO(2) at 80% of VO(2 max), and all work rate phenotypes and a 36% greater decrease in heart rate at 50 W than did the II homozygotes. No associations were evident in Caucasian parents or black parents or offspring. Thus these data do not support the hypothesis that the ACE ID polymorphism plays a major role in cardiorespiratory endurance.     

The effect of exercise intensity and duration on the oxygen deficit and excess post-exercise oxygen consumption

Nine males with mean maximal oxygen consumption (VO2max) = 63.0 ml.kg-1.min-1, SD 5.7 and mean body fat = 10.6%, SD 3.1 each completed nine counterbalanced treatments comprising 20, 50 and 80 min of treadmill exercise at 30, 50 and 70% VO2max. The O2 deficit, 8 h excess post-exercise oxygen consumption (EPOC) and EPOC:O2 deficit ratio were calculated for all subjects relative to mean values obtained from 2 control days each lasting 9.3 h. The O2 deficit, which was essentially independent of exercise duration, increased significantly (P less than 0.05) with intensity such that the overall mean values for the three 30%, 50% and 70% VO2max workloads were 0.83, 1.89 and 3.09 l, respectively. While there were no significant differences (P greater than 0.05) between the three EPOCs after walking at 30% VO2max for 20 (1.01 l), 50 (1.43 l) and 80 min (1.04 l), respectively, the EPOC thereafter increased (P less than 0.05) with both intensity and duration such that the increments were much greater for the three 70% VO2max workloads (EPOC: 20 min = 5.68 l; 50 min = 10.04 l; 80 min = 14.59 l) than for the three 50% VO2max workloads (EPOC: 20 min = 3.14 l; 50 min = 5.19 l; 80 min = 6.10 l). An analysis of variance indicated that exercise intensity was the major determinant of the EPOC since it explained five times more of the EPOC variance than either exercise duration or the intensity times duration interaction. The mean EPOC:O2 deficit ratio ranged from 0.8 to 4.5 and generally increased with both exercise intensity and duration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma free and sulfoconjugated catecholamine responses to varying exercise intensity

Plasma free catecholamines rise during exercise, but sulfoconjugated catecholamines reportedly fall. This study examined the relationship between exercise intensity and circulating levels of sulfoconjugated norepinephrine, epinephrine, and dopamine. Seven exercise-trained men biked at approximately 30, 60, and 90% of their individual maximal oxygen consumption (VO2max) for 8 min. The 90% VO2max period resulted in significantly increased plasma free norepinephrine (rest, 219 +/- 85; exercise, 2,738 +/- 1,149 pg/ml; P less than or equal to 0.01) and epinephrine (rest, 49 +/- 49; exercise, 555 +/- 516 pg/ml; P less than or equal to 0.05). These changes were accompanied by consistent increases in sulfoconjugated norepinephrine at both the 60% (rest, 852 +/- 292; exercise, 1,431 +/- 639; P less than or equal to 0.05) and 90% (rest, 859 +/- 311; exercise, 2,223 +/- 1,015; P less than or equal to 0.05) VO2max periods. Plasma sulfoconjugated epinephrine and dopamine displayed erratic changes at the three exercise intensities. These findings suggest that sulfoconjugated norepinephrine rises during high-intensity exercise.     

Impact of exercise training on insulin sensitivity, physical fitness, and muscle oxidative capacity in first-degree relatives of type 2 diabetic patients

First-degree relatives of type 2 diabetic patients (offspring) are often characterized by insulin resistance and reduced physical fitness (VO2 max). We determined the response of healthy first-degree relatives to a standardized 10-wk exercise program compared with an age-, sex-, and body mass index-matched control group. Improvements in VO2 max (14.1 +/- 11.3 and 16.1 +/- 14.2%; both P < 0.001) and insulin sensitivity (0.6 +/- 1.4 and 1.0 +/- 2.1 mg x kg(-1) x min(-1); both P < 0.05) were comparable in offspring and control subjects. However, VO2 max and insulin sensitivity in offspring were not related at baseline as in the controls (r = 0.009, P = 0.96 vs. r = 0.67, P = 0.002). Likewise, in offspring, exercise-induced changes in VO2 max did not correlate with changes in insulin sensitivity as opposed to controls (r = 0.06, P = 0.76 vs. r = 0.57, P = 0.01). Skeletal muscle oxidative capacity tended to be lower in offspring at baseline but improved equally in both offspring and controls in response to exercise training (delta citrate synthase enzyme activity 26 vs. 20%, and delta cyclooxygenase enzyme activity 25 vs. 23%. Skeletal muscle fiber morphology and capillary density were comparable between groups at baseline and did not change significantly with exercise training. In conclusion, this study shows that first-degree relatives of type 2 diabetic patients respond normally to endurance exercise in terms of changes in VO2 max and insulin sensitivity. However, the lack of a correlation between the VO2 max and insulin sensitivity in the first-degree relatives of type 2 diabetic patients indicates that skeletal muscle adaptations are dissociated from the improvement in VO2 max. This could indicate that, in first-degree relatives, improvement of insulin sensitivity is dissociated from muscle mitochondrial functions.     

Intensity-controlled treadmill running in rats: VO(2 max) and cardiac hypertrophy

Physiological studies of long-term cardiovascular adaptation to exercise require training regimens that give robust conditioning effects and adequate testing procedures to quantify the outcome. We developed a valid and reproducible protocol for measuring maximal oxygen uptake (VO(2 max)), which was reached at a 25 degrees inclination with a respiratory exchange ratio > 1.05 and blood lactate > 6 mmol/l. The effect of intensity-controlled aerobic endurance training was studied in adult female and male rats that ran 2 h/day, 5 days/wk, in intervals of 8 min at 85-90% of VO(2 max) and 2 min at 50-60% of VO(2 max), with adjustment of exercise level according to VO(2 max) every week. After 7 wk, the increase in VO(2 max) plateaued at 60-70% above sedentary controls. Ventricular weights and myocyte length were up 25-30% and 6-12%, respectively. Work economy, oxygen pulse, and heart rate were sufficiently changed to indicate substantial cardiovascular adaptation. The model mimics important human responses to training and could be used in future studies on cellular, molecular, and integrative mechanisms of improved cardiovascular function.     

Exercise training and its effects with renal hypertensive rats

The influence of endurance training on functional capacity [maximal O2 consumption (VO2 max)], caudal arterial blood pressure, and myocardial capillary density were investigated in normotensive rats and rats made hypertensive using the two-kidney one-clip approach (Goldblatt's hypertension). Male Sprague-Dawley rats were assigned to sham (N: 120-140 mmHg), moderately hypertensive (MH = 0.30-mm clips, 150-170 mmHg), or severely hypertensive (SH = 0.25-mm clips, 190-230 mmHg) groups. Rats designated to be runners (T) were exercised on a motor-driven treadmill equal to 50-70% of their VO2 max values for 8-12 wk. Compared with their nontrained (NT) controls, training was associated with significantly higher VO2 max values (12-15%) and muscle cytochrome-c oxidase activities (33-78%). Resting systolic blood pressure was not significantly changed in the N-and MH-T subgroups; however, it was 20-30 mmHg higher in the SH-T subgroup. Mean absolute heart weight for only the N-T group was significantly heavier than their NT controls. However, the mean predicted heart weights (heart wt = 0.639 X body wt of N-NT + 0.001 g) of the two SH groups were significantly higher than expected. The SH-T group had a lower (11%) subepicardial capillary density mean than its NT control and significantly fewer capillaries in the subendocardial region than the other five subgroups. It was concluded that moderate exercise training appeared to be detrimental to rats with severe hypertension because it increased resting blood pressure and decreased myocardial capillary density, even though it improved their functioning capacity.     

Sweat lactate secretion during exercise in relation to women's aerobic capacity

The purpose of this investigation was to determine whether sweat lactate secretion during exercise [approximately 70% maximum O2 consumption (VO2max), 60 min] differed in active vs. sedentary female subjects. Sweat rate, total sweat lactate secretion, and sweat lactate concentration were monitored in a group of sedentary (VO2max = 41.0 +/- 1.62 ml X kg-1 X min-1) and active (VO2max = 51.2 +/- 3.20 ml X kg-1 X min-1) women. Sweat rate was significantly (P less than 0.05) greater in the active subjects. There was a significant difference between groups in total amount of sweat lactate secreted (P less than 0.05), with the active group secreting less lactate (29.8 +/- 5.03 mmol, mean +/- SE) than the sedentary group (50.2 +/- 6.61 mmol). Concomitant with the lower total sweat lactate secretion in the active subjects was a significantly (P less than 0.05) more dilute sweat lactate concentration (42.6 +/- 14.08 vs. 100.4 +/- 32.37 mM). In these female subjects, sweat lactate concentration was inversely correlated (r = -0.79, P less than 0.01, n = 10) to sweat rate. It is concluded that total sweat lactate loss is significantly less in active than in sedentary women and that the active subjects secrete a greater quantity of lactate dilute sweat.     

Cellular accumulation of heat shock protein (Hsp) 72i in fetuses of trained rats

Forty-five Sprague-Dawley rats (60-80 days old) were randomly placed into one of three groups: sedentary pregnant control (PC); prepregnancy trained animals that exercised throughout pregnancy (PR); and nonpregnant trained animals (NPR). Each exercising animal ran at approximately 60-70% aerobic capacity (VO2max) for 1 hour/day up to and including day 18 of gestation (term = 21 days). On day 20 of gestation, fetuses were excised from each pregnant animal and scrutinized for gross abnormalities. In 3 randomly chosen fetuses from each litter, brain, heart, kidney, hind limb, and placental tissues were removed to assess the accumulation of the inducible isoform of the 70-kilodalton heat shock protein (Hsp 72i). No significant differences were detected between fetal hearts, hind limbs, or placental tissues of PC or PR groups. No Hsp 72i signal could be detected in fetal kidney or brain tissues from either pregnant group. Results indicate that maternal core temperature did not reach the threshold that would induce either gross fetal abnormalities or a fetal heat shock protein response. However, fetal and placental growth was reduced by the exercise protocol.     

Comparison in men of physiological responses to exercise of increasing intensity at low and moderate ambient temperatures

In six male subjects the sweating thresholds, heart rate (fc), as well as the metabolic responses to exercise of different intensities [40%, 60% and 80% maximal oxygen uptake (VO2max)], were compared at ambient temperatures (Ta) of 5 degrees C (LT) and 24 degrees C (MT). Each period of exercise was preceded by a rest period at the same temperature. In LT experiments, the subjects rested until shivering occurred and in MT experiments the rest period was made to be of exactly equivalent length. Oxygen uptake (VO2) at the end of each rest period was higher in LT than MT (P less than 0.05). During 20-min exercise at 40% VO2max performed in the cold no sweating was recorded, while at higher exercise intensities sweating occurred at similar rectal temperatures (Tre) but at lower mean skin (Tsk) and mean body temperatures (Tb) in LT than MT experiments (P less than 0.001). The exercise induced VO2 increase was greater only at the end of the light (40% VO2max) exercise in the cold in comparison with MT (P less than 0.001). Both fc and blood lactate concentration [1a]b were lower at the end of LT than MT for moderate (60% VO2max) and heavy (80% VO2max) exercises. It was concluded that the sweating threshold during exercise in the cold environment had shifted towards lower Tb and Tsk. It was also found that subjects exposed to cold possessed a potentially greater ability to exercise at moderate and high intensities than those at 24 degrees C since the increases in Tre, fc and [1a]b were lower at the lower Ta.     

Effect of exercise intensity and duration on postexercise metabolism

Data are reported on the net recovery O2 consumption (VO2) for nine male subjects (mean age 21.9 yr, VO2max 63.0 ml.kg-1.min-1, body fat 10.6%) used in a 3 (independent variables: intensities of 30, 50, and 70% VO2max) x 3 (independent variables: durations of 20, 50, and 80 min) repeated measures design (P less than or equal to 0.05). The 8-h mean excess postexercise O2 consumptions (EPOCs) for the 20-, 50-, and 80-min bouts, respectively, were 1.01, 1.43, and 1.04 liters at 30% VO2max (6.8 km/h); 3.14, 5.19, and 6.10 liters at 50% VO2max (9.5 km/h); and 5.68, 10.04, and 14.59 liters at 70% VO2max (13.4 km/h). The mean net total O2 costs (NTOC = net exercise VO2 + EPOC) for the 20-, 50-, and 80-min bouts, respectively, were 20.48, 53.20, and 84.23 liters at 30% VO2max; 38.95, 100.46, and 160.59 liters at 50% VO2max; and 58.30, 147.48, and 237.17 liters at 70% VO2max. The nine EPOCs ranged only from 1.0 to 8.9% of the NTOC (mean 4.8%) of the exercise. These data, therefore, indicate that in well-trained subjects the 8-h EPOC per se comprises a very small percentage of the NTOC of exercise.     

Voluntary exercise in pregnant rats positively influences fetal growth without initiating a maternal physiological stress response

The effects of increased physical activity during pregnancy on the health of the offspring in later life are unknown. Research in this field requires an animal model of exercise during pregnancy that is sufficiently strenuous to cause an effect but does not elicit a stress response. Previously, we demonstrated that two models of voluntary exercise in the nonpregnant rat, tower climbing and rising to an erect bipedal stance (squat), cause bone modeling without elevating the stress hormone corticosterone. In this study, these same models were applied to pregnant rats. Gravid Wistar rats were randomly divided into three groups: control, tower climbing, and squat exercise. The rats exercised throughout pregnancy and were killed at day 19. Maternal stress was assessed by fecal corticosterone measurement. Maternal bone and soft tissue responses to exercise were assessed by peripheral quantitative computed tomography and dual-energy X-ray absorptiometry. Maternal weight gain during the first 19 days of pregnancy was less in exercised than in nonexercised pregnant control rats. Fecal corticosterone levels did not differ between the three maternal groups. The fetuses responded to maternal exercise in a uterine position-dependent manner. Mid-uterine horn fetuses from the squat exercise group were heavier (P < 0.0001) and longer (P < 0.0001) and had a greater placental weight (P = 0.001) than those from control rats. Fetuses from tower-climbing dams were longer (P < 0.0001) and had heavier placentas (P = 0.01) than those from control rats, but fetal weight did not differ from controls. These models of voluntary exercise in the rat may be useful for future studies of the effects of exercise during pregnancy on the developmental origins of health and disease.