Isolated heart responsiveness to beta-simulation after exercise training in obesity

PURPOSE: Exercise training results in many health benefits, but few studies have focused on whether exercise training might attenuate the adverse effects of obesity on heart function. Therefore, the purpose of this study was to determine whether exercise training attenuated obesity-related decreases in systolic contractile function in response to beta-adrenergic stimulation, using the rabbit model of obesity. METHODS: Female New Zealand white rabbits were divided into four groups: lean sedentary, lean exercise-trained, obese sedentary, and obese exercise-trained. Obese rabbits were fed an ad libitum high-fat diet. Exercise-trained rabbits underwent a 12-wk progressive treadmill exercise training protocol. After 12 wk, the Langendorff isolated heart method was used to study developed pressure, +dP/dt, and -dP/dt responses to increasing concentrations of isoproterenol (10(-9)--3 x 10(-7) M). Log concentration-response data were fit to a sigmoidal function, using a four-parameter (minimum, maximum, EC(50), slope) logistic equation. Groups were compared using a 2 x 2 analysis of variance. RESULTS: Although obesity shifted the concentration-response curves for developed pressure, +dP/dt, and -dP/dt to the right as indicated by an increase in the EC(50) (P < or = 0.05), there was no effect of exercise training on any of the logistic regression parameters. EC(50) (log M) values for combined lean versus combined obese were -8.50 +/- 0.7 vs -8.20 +/- 0.09 (developed pressure), -8.04 +/- 0.06 vs -7.68 +/- 0.07 (+dP/dt), and -8.17 +/- 0.07 vs -7.91 +/- 0.09 (-dP/dt). CONCLUSION: These results confirm the negative effect of obesity on responsiveness of the isolated heart to beta-adrenergic stimulation but indicate that exercise training does not significantly attenuate obesity-related changes.     

Low-intensity exercise training improves survival in Dahl salt hypertension

PURPOSE: The present study examined whether exercise training could increase survival in a rodent model of salt-sensitive hypertension. METHODS: Male, inbred Dahl salt-sensitive rats arriving at 8 wk of age were randomly divided into a sedentary control group (N = 5) or an exercise-trained group (N = 8). Exercise training consisted of running 20 m.min(-1), 0% incline, 60 min.d(-1), 5 d.wk(-1) on a motorized driven treadmill. On arrival, animals were fed a low-salt diet (0.12% NaCl) during a 1-wk acclimatization period. At the end of this period, all rats were then fed a high-salt diet (7.8% NaCl) for the remainder of the study. Arterial systolic blood pressure (SBP) was measured via the tail-cuff method. RESULTS: Systolic blood pressure (SBP) measured on the low salt diet was similar between groups. After 2 wk of a high-salt diet, SBP was similarly significantly elevated in both control and exercise groups relative to the low salt diet. Kaplan-Meier analysis showed that exercise training increased survival (P < 0.02) with an approximate 30% increase in the mean days survived with exercise training (P < 0.02). CONCLUSION: These data suggest that exercise training is an important intervention for salt-sensitive hypertension and that the enhanced survival observed with exercise training appears to be independent of training-induced SBP lowering effects.     

Meal-induced thermogenesis following exercise training in the rat

The effects of treadmill exercise on the thermic effect of a meal were studied in male Sprague-Dawley rats (370 to 400 g, 4 to 5 months of age). Rats were exercised for 60 min, 5 d.wk-1 for 8 to 10 wk, at a speed of 27 m.min-1 and with a grade of 8%. Sedentary (N = 9) and exercised (N = 8) rats were given food and water ad libitum. Oxygen consumption was measured at rest and following the ingestion of a meal consisting of 81% carbohydrate, 9% protein, and 10% fat (by calories). In those animals that were exercised, oxygen consumption measurements were performed 24 h after the completion of an exercise bout. Although all animals gained weight during the experimental period, the exercised group gained significantly less than did the sedentary rats. Resting oxygen consumption [ml/(min X g body mass.67)] was not significantly different between the exercised and sedentary rats. The ingestion of the high carbohydrate meal significantly increased mass-independent oxygen consumption above resting values in both groups; the values for the exercised rats were greater than those for the sedentary rats. However, there were no differences between the exercised and sedentary rats in meal-induced oxygen consumption when the data were expressed as a function of lean body mass [ml/(min X g lean body mass)] or as mass-independent lean body mass [ml/(min X g lean body mass.67)]. These data suggest that exercise-trained rats have increased diet-induced thermogenesis and may be one factor in the loss of weight sometimes found in response to exercise.     

Exercise training attenuates septic responses in conscious rats

PURPOSE: To evaluate the effects of exercise training on the changes induced by endotoxin in arterial pressure, heart rate (HR), blood cells, biochemical factors, plasma nitrite/nitrate, methyl guanidine (MG), proinflammatory cytokines, and pathology of the heart, liver, and lung. METHODS: Twenty-four 10-wk-old male Wistar-Kyoto rats weighing 320-350 g were randomly assigned into two groups. The exercise-trained group (Tr; N = 12) received exercise training for 4 wk. The control (Con) group was placed on the treadmill and remained sedentary for the same time period. Endotoxemia was induced by intravenous (i.v.) infusion of lipopolysaccharide (LPS; 10 mg.kg(-1)) for 20 min, after which the animals were observed for 72 h. The femoral artery was cannulated to monitor arterial pressure and HR. Blood samples were collected 1 h before and at various times after LPS infusion. We determined plasma nitrite/nitrate, MG, white blood cells, neutrophils, lymphocytes, red blood cells, blood urea nitrogen, creatinine (Cr), aspartate aminotransferase, alanine aminotransferase, lactic acid dehydrogenase, creatine phosphokinase, amylase, lipase, tumor necrosis factor(alpha), and interleukin-1(beta). The heart, liver, and lung were taken for pathological examination and assessment after the experiment. RESULTS: The Tr group had lower basal levels of arterial pressure, HR, MG, neutrophils, and Cr than the Con group. Exercise training attenuated the LPS-induced decreases in blood cells. After LPS administration, plasma levels of nitrate/nitrite, MG, biochemical factors, and proinflammatory cytokines in the Con group were higher than in the Tr group. Pathological examination and assessment revealed that cardiac, hepatic, and pulmonary injury were more severe in the Con group than in the Tr group. CONCLUSIONS: Exercise training attenuates septic responses and protects organs from damage in sepsis.     

Training responses of plasma beta-endorphin, adrenocorticotropin, and cortisol

The purpose of this study was to examine the effects of three different run training programs on plasma responses of beta-endorphin (beta-EP), adrenocorticotropin (ACTH), and cortisol to maximal treadmill exercise. Subjects were randomly assigned to one of three training groups: sprint intervals (SI) (N = 8), endurance (E) (N = 10), or combination (C) (N = 7). Training was monitored for 10 wk, and maximal treadmill exercise tests were administered pre-training and after 2, 4, 6, 8, and 10 wk of training. Blood samples were obtained (pre-training and after 10 wk) before, immediately after, and 5 and 15 min following the maximal exercise tests. All groups significantly (P less than 0.05) increased maximal oxygen consumption values at 8 and 10 wk of the training period. Significant exercise-induced increase in plasma beta-EP, ACTH, cortisol, and blood lactate were observed for both pre- and post-training tests in all training groups. The SI group demonstrated significant post-training increases in beta-EP, ACTH, cortisol, and 5 min post-exercise blood lactate concentrations in response to maximal exercise. No training-induced hormonal changes were observed for the E group. While exercise-induced increases were observed, the C group exhibited significant post-training reductions in plasma responses of beta-EP, ACTH, and blood lactate concentrations in response to maximal exercise. Still, resting and post-exercise increases in plasma cortisol concentrations were significantly higher in magnitude in the post-training test. Lactate was significantly correlated with beta-EP (r = 0.72), ACTH (r = 0.70), and cortisol (r = 0.64).(ABSTRACT TRUNCATED AT 250 WORDS)     

Exercise training and autonomic nervous system activity in obese individuals

PURPOSE: This study was designed to investigate the effects of 12 wk of exercise training on autonomic nervous system (ANS) in 18 obese middle-aged men (N = 9) and women (N = 9) (age: 41.6 +/- 1.2 yr; BMI: 27.3 +/- 0.4 kg x m(-2); %fat: 29.6 +/- 1.3%, mean +/- SE). METHODS: Each subject participated in an aerobic exercise training at anaerobic threshold (AT), consisting of 30 min/session, 3 times/wk, for 12 consecutive weeks. The ANS activities were assessed by means of power spectral analysis of heart rate variability (HRV) at resting condition before, at 5 wk, and after the exercise program. RESULTS: The exercise training resulted in a significant decrease in body mass, BMI, and % fat (P < 0.01) but not in lean body mass (P > 0.05) together with a significant increase in the AT VO2 (P < 0.01). Our power spectral data indicated that there were significant increases in the low-frequency component associated with the sympathovagal activity (0.03--0.15 Hz, 348.5 +/- 66.8 vs 694.7 +/- 91.5 ms(2), P < 0.01), the high-frequency vagal component (0.15--0.4 Hz, 146.3 +/- 30.4 vs 347.7 +/- 96.5 ms(2), P < 0.05), and the overall autonomic activity as evaluated by total power (0.03--0.4 Hz, 494.8 +/- 88.5 vs 1042.4 +/- 180.9 ms(2), P < 0.01) of HRV after the training. CONCLUSIONS: Twelve weeks of exercise training has significantly improved both the sympathetic and parasympathetic nervous activities of the obese individuals with markedly reduced ANS activity, suggesting a possible reversal effect of human ANS functions. These favorable changes may also have an influence on the thermoregulatory control over the obesity.     

Exercise training improves left ventricular isovolumic relaxation

PURPOSE: Left ventricular (LV) diastolic function is an important determinant of aerobic fitness. The purpose of this paper was to investigate the relationship between aerobic fitness and the rate and extent of isovolumic LV relaxation. METHODS: Two series of experiments were performed utilizing both human and animal models. In the first series of experiments, the relationship between LV diastolic time intervals and exercise capacity was assessed in two groups of collegiate men (N = 18) with variable peak run times (Bruce protocol). In the second series of experiments, the extent of LV relaxation was examined in sedentary and exercise-trained rats (treadmill running), using an isolated, isovolumic heart preparation. Subsequent morphological assessment was also performed in rats. RESULTS: At rest, men with greater peak treadmill time had a shorter resting LV isovolumic relaxation time (R-R interval adjusted 1000 ms) (long duration runners, 84+/-5 ms vs short duration runners, 105+/-7 ms, P < 0.05) despite a similar LV diastolic interval. Peak treadmill time was inversely correlated to LV isovolumic relaxation time (R-R interval adjusted 1000 ms) (r = -0.55; P < 0.02). In animal studies (N = 26), the LV pressure-volume relationship was shifted rightward in exercise-trained rats (P = 0.003). Exercise-trained rats had an increased LV inner diameter (sedentary, 5.1+/-0.35 mm vs exercise-trained, 6.1+/-0.28 mm, P < 0.05) and a thicker interventricular septum (sedentary, 1.52+/-0.06 mm vs exercise-trained, 1.72+/-0.09 mm, P < 0.05). CONCLUSION: This study suggests that both the rate and extent of LV isovolumic relaxation is enhanced with exercise training. Further study is required to understand the interrelationship between exercise and diastolic function.     

Normalization of the metabolic profile in obese women by exercise and a low fat diet.

This study was performed to evaluate the additive effect of exercise and a low fat diet on body weight, body composition, and the metabolic profile in four obese women who were previously exercise-trained for 15 months. This study therefore included regular aerobic exercise for 15 months and a low fat diet plus exercise for an additional period of 14 months. After 15 months, mean body weight and fat losses corresponded to 6.4 and 8.4 kg, respectively. Significant reductions (P less than 0.05) in plasma insulin, cholesterol, apo B, and LDL-C were also observed. Following the second part of the study, mean cumulative body weight and fat losses were 11.0 and 11.3 kg, respectively. At this time, the subjects were still overweight, but their plasma glucose and insulin during an oral glucose tolerance test were essentially similar to values obtained in a sample of 22 nonobese women. With the exception of plasma apo B and HDL-C levels, plasma lipid and lipoprotein levels were also comparable to those observed in nonobese controls. These results thus indicate that aerobic exercise-training and a low fat diet can normalize the metabolic profile of obese women, even if their adiposity remains higher than that of lean women.     

Decreases in resting plasma beta-endorphin/-lipotropin after endurance training

The purpose of the present study was to investigate changes in the resting plasma beta-endorphin/-lipotropin (beta E/beta-LPH) concentration that may occur with exercise training. A treatment group (N = 10) of previously sedentary, psychologically normal, and medically healthy middle-aged men trained for 4 months in a structured fitness program. The treatment group was compared with two age-matched groups: a jogger group (N = 10) and a sedentary group (N = 10). Venous blood was collected in the early morning after the subjects had been fasting for at least 12 h. The subjects were also resting at the time of blood collection. Resting plasma beta E/beta-LPH (measured by radioimmunoassay) decreased (P less than 0.05) following the 4 months of exercise training in the treatment group, from 11.01 +/- 1.62 (SE) to 7.22 +/- 0.99 pmol.1-1. The jogger and sedentary groups demonstrated no changes in the resting plasma beta E/beta-LPH concentration following the 4 months. Aerobic fitness, measured by the maximal oxygen uptake (VO2max), increased (P less than 0.01) from 36.56 +/- 2.58 (SE) to 44.85 +/- 1.34 ml.kg-1.min-1 in the treatment group after the 4 months of training. There were no changes in VO2max for either the jogger group or the sedentary group following the 4 months. In conclusion, beta E/beta-LPH in the plasma of resting middle-aged men appeared to be decreased after 4 months of aerobic training.     

Physiological responses to weight-loss intervention in inactive obese African-American and Caucasian women

BACKGROUND: The physiological responses of inactive obese premenopausal African-American and Caucasian women to the identical exercise training and behavior modification program were compared. METHODS: Inactive obese (96.1+/- 2.9 kg, BMI=34.8 +/- 0.7 kg/m2, % body fat=46.0 +/- 0.8; mean +/- SEM) premenopausal (36 +/- 2 yrs) African-American (n=10) and Caucasian (n=19) women were included. Resting metabolic rate (RMR), respiratory exchange ratio (RER), and maximal aerobic power (VO2max) were measured by indirect calorimetry, and body composition by plethysmography. Resting and maximal heart rates, blood glucose and lipids, and blood pressure were also measured. Treatment consisted of a 13-week diet and exercise behavior modification program. Group mean comparisons were made with a Student's "t"-test or an ANCOVA, which controlled for individual differences in body mass and lean body mass (LBM). Significance was set at p<0.05. RESULTS: Initially, the groups were not significantly different in height, mass, BMI, age, % body fat, fat mass, LBM, girth measurements, RMR, RER, VO2max, blood pressure, or cholesterol profile. The number of weeks completed, number of exercise sessions completed, total minutes of exercise for the entire intervention, average minutes of daily exercise, and total estimated exercise energy expenditure were all similar between groups. Furthermore, both groups reported similar dietary compliance. Both groups reduced body mass, BMI, LBM, girth measurements, and increased VO2max (mlO2 x kg-1 x min-1) significantly and similarly. CONCLUSIONS: African-American and Caucasian women respond the same physiologically to weight loss intervention. The higher prevalence in obesity for African-American women is not due to a different physiological response to diet and exercise.     

NMR spectroscopy study of heart phospholipids. An exercise and anabolic steroids effect.

Because 31P NMR spectral analysis of phospholipid (PL) is an accurate and rapid technique for resolving the quantity of PL resonances and involving minimum chemical manipulations that may affect the integrity of the tissue (24-26), we studied the effect of anabolic steroid injection, exercise training, or a combination of both treatments on whole heart phospholipids using 31P NMR spectral analysis. Male Sprague-Dawley rats were randomly assigned to 4 groups of 11 each: sedentary control (C), steroid-treated (ST), exercise-trained (E), and exercise plus steroid-treated (ES). The ST and ES rats were administered nandrolone decanoate by i.m. injection every 7-9 d during the 10 wk study, while the C and E rats were injected with glycerol. The exercise rats ran on a treadmill, wearing a collar weight for 50 min/day, 5 days/wk. There was a significant difference in body wt among the four groups at the conclusion of the study; however, no significant differences in heart wt or in the ratio of heart wt:body wt were observed among the four groups. Myocardial phospholipid profiles of the exercise-trained rats were significantly (p less than 0.05) different from those of the untrained rats. The changes were enhanced somewhat by the steroid treatment. The profiles differed in the relative amounts of four of the nine myocardial phospholipids detected: phosphatidylcholine, phosphatidylethanolamine (PE), PE plasmalogen, and phosphatidylserine. We conclude that the observed changes in whole heart phospholipid compositions are due to experimental treatment specifically from exhaustive exercise and not from anabolic steroids or cardiac hypertrophy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Resting heart rate changes after endurance training in older adults: a meta-analysis

PURPOSE: Question remains regarding endurance training and changes in resting heart rate (HR) among older individuals. The objective of this meta-analysis was to determine the effects of controlled aerobic training on resting HR among sedentary older adults. METHODS: Studies were identified by a systematic computer database search, hand article search, and cross-reference. The inclusion criteria were (i) controlled clinical trials, (ii) endurance exercise as the only intervention, (iii) a nonexercise control group, (iv) within-group mean ages of subjects > or = 60 yr, (v) a measure of changes in resting HR, (vi) studies published in English journals. RESULTS: Outcome was derived from 13 studies with a total of 651 individuals in 14 control (N = 241) and 16 exercise groups (N = 410). The pooled standardized effect size by a fixed-effect model showed an upper moderate effect of -0.58 +/- 0.08 (mean +/- SEM, 95% CI = -0.74 to -0.42). This homogeneity effect was statistically significant (P = 0.001). The magnitude of net change averaged -6 bpm (-2 to -12 bpm), representing an 8.4% reduction. Greater and statistically significant decrease of resting HR among the elderly was found in the studies with training length more than 30 wk. CONCLUSIONS: This meta-analytic investigation supports the efficacy of endurance exercise training in decreasing HR at rest in older adults. This training induced adaptation may have protective benefits for cardiovascular aging. A longer exercise training length, probably more than 30 wk, may be needed for older individuals to be more effective in terms of resting HR reduction.     

Exercise training-induced changes in coagulation factors in older adults

The coagulation cascade plays a critical role in the development of cardiovascular disease (CVD). Elevated plasma prothrombin fragment 1 + 2 (F1 + 2) and factor VIII antigen (FVIII:Ag) levels have been associated with a hypercoagulable state, enhancing the risk for vascular thrombotic events. Aerobic training is known to reduce CVD risk, and an improved coagulation profile may contribute to this reduction. PURPOSE: To analyze the effect of 6 months of standardized aerobic exercise training on resting F1 + 2 and FVIII:Ag levels in men and postmenopausal women aged 50-75 while accounting for several possibly confounding factors. MATERIALS AND METHODS: Sedentary men (N=16) and women (N=31) underwent supervised aerobic training 3 d x wk(-1) for 6 months while maintaining the American Heart Association step 1 diet. Baseline and final testing included measurement of F1 + 2, FVIII:Ag, plasma lipoprotein-lipid levels, body composition, and VO2max. RESULTS: When adjusted for baseline values and changes in diastolic blood pressure with training, F1 + 2 was found to decrease significantly with exercise training from 1.493 +/- 0.058 to 1.422 +/- 0.059 nM (P=0.014). FVIII:Ag levels were found to increase significantly with training when adjusted for baseline values, from 152.5 +/- 6.7% of standard at baseline to 156.0 +/- 6.1% of standard at final testing (P=0.005). Training-induced changes in coagulation markers were independent of changes in blood lipids, aerobic capacity, and body composition. CONCLUSIONS:: These results indicate that endurance training has a significant impact on the coagulation cascade, reducing coagulation activity in the common pathway and thrombin formation at rest while increasing the activation potential of the intrinsic pathway.     

Training in hypoxia: modulation of metabolic and cardiovascular risk factors in men

PURPOSE: This study was designed to determine changes in metabolic and cardiovascular risk factors following normobaric hypoxic exercise training in healthy men. METHODS: Following a randomized baseline maximal exercise test in hypoxia and/or normoxia, 34 physically active subjects were randomly assigned to either a normoxic (N = 14) or a hypoxic (N = 18) training group. Training involved 4 wk of cycling exercise inspiring either a normobaric normoxic (F(IO2) = approximately 20.9%) or a normobaric hypoxic (F(IO2) = approximately 16.0%) gas, respectively, in a double-blind manner. Cycling exercise was performed three times per week for 20-30 min at 70-85% of maximum heart rate determined either in normoxia or hypoxia. Resting plasma concentrations of blood lipids, lipoproteins, total homocysteine, and auscultatory arterial blood pressure responses at rest and in response to submaximal and maximal exercise were measured before and 4 d after physical training. RESULTS: Total power output during the training period was identical in both normoxic and hypoxic groups. Lean body mass increased by 1.4 +/- 1.5 kg following hypoxic training only (P < 0.001). While dietary composition and nutrient intake did not change during the study, both normoxic and hypoxic training decreased resting plasma concentrations of nonesterified fatty acids, total cholesterol, high density lipoprotein (HDL), and low density lipoprotein (LDL) (P < 0.05 - < 0.001). Apolipoproteins AI and B decreased following normoxic training only (P < or = 0.001). Plasma concentrations of resting total homocysteine decreased by 11% following hypoxic training (P < or = 0.05) and increased by 10% (P < 0.05) following normoxic training. These changes were independent of changes in serum vitamin B12 and red cell folate which remained stable throughout. A decreased lactate concentration during submaximal exercise was observed in response to both normoxic and hypoxic training. Hypoxic training decreased maximal systolic blood pressure by 10 +/- 9 mm Hg (P < 0.001) and the rate pressure product by 14 +/- 23 mm Hg x beats x min(-1)/100 (P < or = 0.001) and increased maximal oxygen uptake by 0.47 +/- 0.77 L x min(-1) (P < 0.05). CONCLUSION: Normoxic and hypoxic training was associated with significant improvements in selected risk factors and exercise capacity. The stimulus of intermittent normobaric hypoxia invoked an additive cardioprotective effect which may have important clinical implications.     

运动对衰老大鼠心血管功能和肠系膜动脉反应性的影响

目的:研究有氧运动对衰老大鼠心血管功能和肠系膜动脉反应性的影响。方法:健康雄性Wistar大鼠,19月龄,24只,随机分为老年安静组(O-SED)和老年有氧运动组(O-EX)两组,每组12只。O-EX组进行12周15 m/min、60 min/d、5 d/w的跑台运动。另2月龄大鼠12只作为青年对照组(Young)。O-EX组运动12周后,每组选取6只大鼠行股动、静脉插管手术。24 h后,清醒状态下测试、记录大鼠基础血压和心率,然后股静脉注射去甲肾上腺素(NE),观察大鼠血压变化。其余6只进行肠系膜动脉血管环张力测定,检测血管收缩特性。结果:1)老年有氧运动组大鼠基础心率显著低于老年安静组;两组老年大鼠收缩压(SBP)和脉压(PP)均显著高于青年对照组,老年有氧运动组SBP和PP均显著低于老年安静组,但仍高于青年对照组。2)静脉注射NE引起两组老年大鼠的升压反应显著低于青年对照组,老年有氧运动组升压反应大于老年安静组,但仍低于青年对照组;3)各组大鼠肠系膜动脉血管环对NE有浓度依赖性收缩,各组老年大鼠血管对NE的最大收缩反应显著下降,且老年有氧运动组对NE的敏感性高于老年安静组;4)非特异性钾通道阻断剂TEA可使血管收缩,收缩幅度Young组>O-EX组>O-SED组。结论:有氧运动改善衰老大鼠心血管反应性以及肠系膜动脉舒缩功能,其中平滑肌钾通道可能是其重要机制之一。     

Plasma organochlorine concentrations in endurance athletes and obese individuals

PURPOSE: Organochlorines are lipophilic compounds that are ingested with food and that accumulate in adipose tissue. Their plasma concentrations were compared in three groups of individuals with different body fatness characteristics: endurance athletes, lean sedentary subjects, and obese individuals. METHODS: The relationship between body fat mass and total plasma organochlorine concentration adjusted for age was analyzed by pooling data of sedentary lean and obese subjects. The regression equation derived from this analysis was also used to predict residual scores of total organochlorine concentrations in trained individuals, which were compared to measured values in these subjects. RESULTS: Plasma organochlorine concentrations tended to be lower in athletes in comparison with values measured among lean sedentary individuals. Their concentrations were higher in obese individuals than in lean sedentary subjects and athletes. Total plasma organochlorine concentration was positively associated to body fat mass in the sedentary group (lean and obese combined, reference population). CONCLUSION: Large adipose tissue compartment such as observed in obese individuals is associated with increased levels of circulating organochlorines, whereas leaner sedentary and trained persons have a lower plasma concentration of these compounds.     

Exercise training produces changes in free and conjugated catecholamines

In dogs the concentrations of conjugated dopamine in plasma have previously been shown to increase after exercise training. This study was done to determine whether conjugated norepinephrine and epinephrine also increase. Fifteen dogs were randomly divided into training (N = 8) or sedentary (N = 7) groups. All dogs were exercised acutely for 5 min at 4 mph with a 12% grade, following a 3-min warm-up, before and after either a 12-wk training or a 12-wk sedentary period. Free and conjugated catecholamines were determined in blood drawn at rest and during acute exercise using high-performance liquid chromatography (HPLC) with electrochemical detection. Before training, free norepinephrine, epinephrine, dopamine, and conjugated norepinephrine increased in plasma during acute exercise. Following the 12-wk training period, there were significant increases in free and conjugated dopamine and in conjugated norepinephrine in plasma taken at rest. There were no such increases in resting catecholamines after a 12-wk sedentary period. After either training or sedentary periods, dogs responded to acute exercise with an increase in free norepinephrine and a decrease in conjugated norepinephrine. Thus, after training both conjugated norepinephrine and dopamine, but not conjugated epinephrine, increased in plasma. The data suggest that sulfation of catecholamines increases as a result of exercise training.     

Exercise attenuates the weight-loss-induced reduction in muscle mass in frail obese older adults

PURPOSE: To evaluate the effect of adding exercise to a hypocaloric diet on changes in appendicular lean mass and strength in frail obese older adults undergoing voluntary weight loss. METHODS: Thirty frail older (age, 70 +/- 5 yr) obese (body mass index, 37 +/- 5 kg.m) adults were randomly assigned to 6 months of diet/behavioral therapy (diet group, n = 15) or diet or behavioral therapy plus exercise that incorporated progressive resistance training (PRT; diet + exercise group; n = 15). Body composition was assessed using dual-energy x-ray absorptiometry, and muscle strength was assessed using one-repetition maximum. The volume of upper extremity (UE) and lower extremity (LE) exercise training was determined by multiplying the average number of repetitions performed by the average weight lifted during the first three exercise sessions and during the last three exercise sessions of the study. RESULTS: The diet and the diet + exercise groups had similar (P > 0.05) decreases in weight (10.7 +/- 4.5 vs 9.7 +/- 4.0 kg) and fat mass (6.8 +/- 3.7 vs 7.7 +/- 2.9 kg). However, the diet + exercise group lost less fat-free mass (FFM; 1.8 +/- 1.5 vs 3.5 +/- 2.1 kg), LE lean mass (0.9 +/- 0.8 vs 2.0 +/- 0.9 kg), and UE lean mass (0.1 +/- 0.2 vs 0.2 +/- 0.2 kg) than the diet group (P < 0.05). The diet + exercise group had greater increases in percent of weight as FFM (FFM / weight x 100) than the diet group (7.9 +/- 3.3 vs 5.4 +/- 3.7%; P < 0.05). Despite lean mass losses, the diet + exercise group increased UE and LE strength in response to exercise (17-43%), whereas the diet group maintained strength. The volume of UE and LE exercises correlated with the amount of UE and LE lean mass (r = 0.64-0.84; P < 0.05). CONCLUSION: Exercise added to diet reduces muscle mass loss during voluntary weight loss and increases muscle strength in frail obese older adults. Regular exercise that incorporates PRT should be used to attenuate muscle mass loss in frail obese older adults on weight-loss therapy.     

Influence of caffeine on the resting metabolic rate of exercise-trained and inactive subjects

The effect of caffeine on the resting metabolic rate (RMR) was investigated in endurance exercise-trained (N = 14) and inactive (N = 10) male individuals. Subjects were also classified into regular and non-regular consumers of caffeine. After an overnight fast, RMR was measured using an indirect calorimetry open circuit system. Thereafter, subjects orally consumed 300 mg of caffeine, after which RMR was measured for 90 min. Five of the exercise-trained subjects were also studied after the administration of a placebo. Plasma concentrations of glycerol and free fatty acid and respiratory exchange ratio (R) were measured at each 15-min interval. Before caffeine ingestion, no significant differences were observed in RMR, R, glycerol, free fatty acid and blood pressure levels between exercise-trained and inactive groups. Following caffeine consumption, a three-way analysis of variance revealed that inactive subjects exhibited a greater increase (P less than 0.05) in RMR than did exercise-trained subjects. No significant differences were observed in RMR response between regular or nonregular consumers of caffeine. Moreover, no differences were observed in glycerol, free fatty acid, heart rate, and blood pressure response between exercise-trained and inactive subjects and between regular and non-regular consumers of caffeine. These results suggest that endurance training results in a reduced thermogenic response to a caffeine challenge.