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PubMed1985

Effect of exercise training on aortic collagen content in spontaneously hypertensive rats (SHR).

We investigated the effects of exercise training on the amount of aortic collagen and systolic blood pressure in spontaneously hypertensive rats (SHR). Ten-week old SHR were trained either by forced treadmill running (26.8 m X min-1 -1 h X day-1, five times a week, 0% incline) or by voluntary running in revolving wheels (7,800 m X day-1 at peak) for 8 weeks. Succinate dehydrogenase (SDH) activity measured as a marker of an endurance training effect was 13% higher (P less than 0.01) in the soleus of forced-exercised animals than in that of sedentary ones. (6.56 +/- 0.17 mumol X g-1 X min-1; mean +/- SEM), whereas SDH activity in that of voluntarily-exercised group was found to be at the same level as in sedentary animals. The systolic blood pressure after training increased by 26.4 in sedentary, 21.1 in voluntarily-exercised, and 33.9 mm Hg in forced-exercised rats, when compared with the value of each group at the beginning of the training program. A significant difference was observed in the increment of blood pressure only between the voluntarily- and forced-exercised groups (P less than 0.05). The amount of aortic collagen in voluntarily-trained rats (96.5 +/- 2.0 mg X g tissue-1, 39.8 +/- 0.7 mg X 100 mg protein-1) was significantly less than that in forced-trained rats (P less than 0.05). These results suggest that voluntary, mild exercise training may be more effective in the reduction of collagen accumulation in the aorta associated with the suppression of blood pressure increase than forced, vigorous exercise training in SHR.

Animals↗

PubMed1992

Effect of exercise training on intracellular free Ca2+ transients in ventricular myocytes of rats.

The purpose of this study was to test the hypothesis that exercise training induces enhanced intracellular free Ca2+ (Cai) availability to the contractile elements of cardiac cells. Cai transients were directly measured in single isolated contracting ventricular myocytes from exercise-trained (EX) and sedentary control (SED) rats. Male Sprague-Dawley rats underwent 16 wk of progressive treadmill exercise (32 m/min, 8% grade, 1.5 h/day) (EX) or were cage confined (SED). EX rats had lower resting heart rate and elevated skeletal muscle oxidative capacity. Cai was measured with the fluorescent Cai indicator fura-2. Simultaneous video monitoring indicated that myocytes suspended in physiological salt solution were quiescent until stimulated electrically at a frequency of 0.2 Hz (12-36 V, 2-ms duration). Stimulated Cai transients, measured from changes in fura-2 fluorescence, were similar in cells from EX and SED groups. Peak shortening, time to peak shortening, velocity of shortening, contraction duration, and time to half-relaxation were also similar in cells from EX and SED rats. Ryanodine (10 microM) was applied to eliminate the contribution of Ca2+ release from sarcoplasmic reticulum to the Cai transient. Verapamil was applied to eliminate the contribution of voltage-gated Ca2+ channels to Cai transients. Cai transients were also similar in cells from EX and SED groups after these pharmacological interventions. These results suggest that treadmill training of rats does not alter Cai availability to the contractile elements in isolated ventricular myocytes.

Animals↗

PubMed1996

Treadmill exercise training and estradiol increase plasma ACTH and prolactin after novel footshock.

We examined whether rats that were treadmill exercise trained (Tr) or chronically immobilized (CI) had similar responses by the hypothalamic-pituitary-adrenal (HPA) cortical axis to acute stress and whether the HPA responses interacted with the hypothalamic-pituitary-gonadal (HPG) axis. After 6 wk (1 h/day, 6 days/wk) of Tr or CI, plasma concentrations of adrenocorticotropic hormone ([ACTH]), [prolactin], and [corticosterone] were measured after familiar (treadmill running or immobilization) or novel (footshock) stress. Ovariectomized Sprague-Dawley females (n = 72) were implanted with capsules containing estradiol benzoate (E2) and randomly assigned in a 2-group (E2 vs. no E2) x 3 treatment (Tr vs. CI vs. sedentary) x 4 acute stressor [footshock vs. treadmill running (Run) vs. immobilization (Im) vs. no stress] x 3 recovery time (1 vs. 15 vs. 30 min) mixed-model analysis of variance. E2 capsules were removed from one-half of the animals 48 h before the first stressor session. After 10 min of acute stress, blood was drawn from a jugular catheter at 1, 15, and 30 min of recovery. [ACTH] and [prolactin] after footshock were higher in Tr rats with E2 compared with CI and sedentary rats without E2; recovery levels for sedentary animals were higher after Run compared with Im. The elevation in [corticosterone] from minute 1 to 15 of recovery was higher after the familiar Run and Im conditions. Our findings are consistent with an increased responsiveness of the HPA axis to novel footshock after treadmill exercise training that is additionally modulated by the HPG axis.

Adrenocorticotropic Hormone↗

PubMed2000

Major gene effect on subcutaneous fat distribution in a sedentary population and its response to exercise training: The HERITAGE Family Study.

Complex segregation analysis of baseline subcutaneous fat distribution and the change in response to exercise training (post-training minus baseline indices) was performed in a sample of 482 individuals from 99 Caucasian families who participated in the HERITAGE Family Study. The sum of skinfold (SF) thicknesses at eight sites, and the waist and hip circumferences were measured at baseline and after completing a 20-week exercise training program. The trunk-to-extremity ratio (TER) was calculated by dividing the sum of skinfold thicknesses at four trunk sites (subscapular + suprailiac + abdominal + midaxillary) by the sum of skinfold thicknesses at four extremity sites (triceps + biceps + medial calf + thigh). While SF was used to assess total subcutaneous adiposity, TER and the ratio of the waist-to-hip circumferences (WHR) were used to characterize subcutaneous fat distribution. Baseline TER and WHR were age-adjusted and age-SF-adjusted within four sex-by-generation groups. The changes of SF, TER, and WHR in response to training were adjusted for age effects alone and for the effects of age and baseline values. Baseline SF was influenced by a multifactorial component (30%) plus a major effect that may be environmental in origin accounting for 47% of the variance. Baseline TER was influenced by a multifactorial component (18%) and a major codominant gene (q(2) = 0.10), which accounted for 56% of the variance. The major gene effect was independent of total subcutaneous adiposity. Baseline WHR was regulated by a major codominant gene (q(2) = 0.15), which accounted for 48% of the variance. However, this major gene effect for baseline WHR should be interpreted with caution, given the estimates of the tau's under the general model. No familial effect was found for the changes in response to training for these subcutaneous adiposity and fat distribution phenotypes. Am. J. Hum. Biol. 12:600-609, 2000. Copyright 2000 Wiley-Liss, Inc.

Journal Article↗

PubMed2000

Fiber type-specific expression of GLUT4 in human skeletal muscle: influence of exercise training.

The fiber type-specific expression of skeletal muscle GLUT4 and the effect of 2 weeks of low-intensity training were investigated in 8 young untrained male subjects. Single muscle fibers were dissected from a vastus lateralis biopsy sample. Based on myosin heavy chain (MHC) expression, fibers were pooled into 3 groups (MHC I, MHC IIA, and MHC IIX), and the GLUT4 content of 15-40 pooled fibers was determined using SDS-PAGE and immunological detection. The GLUT4 content in pooled muscle fibers expressing MHC I was approximately 20% higher (P < 0.05) than that in muscle fibers expressing MHC IIA or MHC IIX. No difference in GLUT4 could be detected between fibers expressing MHC IIA or MHC IIX. Two weeks of exercise training increased (P < 0.05) the peak power output of the knee extensors by 13%, the maximal activities of citrate synthase and 3-hydroxyacyl-CoA dehydrogenase by 21 and 18%, respectively, and the GLUT4 protein content by 26% in a muscle homogenate. Furthermore, a 23% increase (P < 0.05) in GLUT4 was seen in fibers expressing the MHC I isoform after exercise training for 2 weeks. No change was seen in fibers expressing MHC IIA or MHC IIX. In conclusion, our data directly demonstrate that GLUT4 is expressed in a fiber type-specific manner in human skeletal muscle, although fiber type differences are relatively small. In addition, low-intensity exercise training recruiting primarily fibers expressing MHC I increased GLUT4 content in these fibers but not in fibers expressing MHC IIA or MHC IIX, indicating that GLUT4 protein content is related more to activity level of the fiber than to its fiber type, which is defined by expression of contractile protein.

Adult↗

PubMed2002

Fitness levels of firefighter recruits before and after a supervised exercise training program.

Federal law prohibits pre-employment physical examination of firefighter recruits, but these workers must perform intense exercise in arduous environments. Components of physical fitness of rookie firefighters (n = 115; 104 men, mean +/- SD: age = 28.3 +/- 4.3 years; height = 1.76 +/- 0.07 m; weight = 83.2 +/- 13.9 kg; percent body fat = 17 +/- 8%) were measured upon being hired and following a 16-week exercise training program (1 h.d(-1), 3 d.wk(-1)) designed to improve physical fitness. Maximum aerobic capacity (VO2max) was estimated from submaximal cycle ergometry, body composition from skinfold tests, flexibility from a sit and reach test, strength by hand grip dynamometry, and muscle endurance by a push-up test. The results are as follows (*, p <or= 0.007 vs. pretraining): VO2max increased by 28% (35 +/- 7 to 45 +/- 6* ml.kg(-1).min(-1), 88 +/- 20 to 113 +/- 17%* of predicted increase); muscle endurance increased (41 +/- 13 to 51 +/- 14* push-ups); flexibility increased (0.34 +/- 0.07 to 0.35 +/- 0.07* m); muscle strength tended to increase (102.9 +/- 18.7 to 105.4 +/- 18.7 kg, p = 0.06); body weight tended to decrease (83.2 +/- 13.9 to 82.7 +/- 13.2 kg, p = 0.06); lean tissue weight increased (68.8 +/- 9.9 to 69.9 +/- 9.5* kg); and fat weight decreased (14.6 +/- 8.0 to 13.0 +/- 7.1* kg). We concluded that aerobic capacity was 20% lower before training than that deemed sufficient for safe performance of fire suppression duties; that training improved aerobic capacity by 28%, decreased fat and increased lean tissue weight, and increased/tended to increase other components of physical fitness. Prior to initiation of this training program, aerobic capacity of these firefighters was below that deemed appropriate for performing fire suppression duties. Training resulted in a large increase in aerobic capacity, so that the trainees ended the program with an aerobic capacity considered appropriate for fighting fires. It is hoped that the results of this study will encourage those who oversee workers who are responsible for the public's safety to mandate assessment of physical fitness of new hires, with mandatory participation in exercise training for those new hires who are found to possess less than appropriate aerobic capacity.

Adaptation, Physiological↗

PubMed1988

Cardiovascular and respiratory responses to submaximal exercise training in the thoroughbred horse.

Cardiovascular and respiratory responses to submaximal exercise training were investigated in 6 thoroughbred racehorses. Oxygen uptake, heart rate (HR) and arteriovenous oxygen content difference were measured during incremental treadmill exercise tests, before and after 7 weeks of treadmill training. Cardiac output during exercise was calculated by the direct Fick technique. Maximal oxygen uptake (VO2max) was increased by 23% after training, from 129.7 ml/kg/min to 160.0 ml/kg/min. The treadmill speed at which VO2max was attained increased by 19%. The increased aerobic power after training was associated with an increase in maximal cardiac output and stroke volume, a decrease in arteriovenous oxygen difference and no change in HR. There was no change in pulmonary ventilation during exercise at VO2max. Mean mixed venous oxygen content (CvO2) at VO2max before training was 2.8 +/- 1.0 ml/100 ml blood (mean +/- SE). After training the value was 8.6 +/- 1.4 ml/100 ml blood. It is concluded that the increase in VO2max after training in the horse is dependant on augmented blood flow, and is not dependant on either increased arterial oxygen content or arteriovenous oxygen content difference. Cardiac capacity to pump blood is therefore of primary importance as a determinant of increases in VO2max due to training in the horse.

Animals↗

PubMed1992

Effects of a 1-year exercise training program on myocardial ischemia in patients after myocardial infarction.

To determine the effects of exercise training on exercise-induced ischemia in patients following myocardial infarction, the experience of 13 patients with exercise-induced ST depression, who were moderate-to-high intensity trained for 1 year, has evaluated. After training, the maximum ST depression was significantly less (1.9 +/- 0.8 vs. 1.1 +/- 0.8 mm; p < 0.01), despite an increased maximal rate-pressure product (RPP; heart rate x blood pressure/100; 241.3 +/- 44 vs. 262.0 +/- 58; p < 0.01). For the onset of 0.1 mV of ST depression, we found a significant increase in RPP from 204.1 +/- 34.7 to 234.1 +/- 49.4 (p < 0.01) and also in heart rate (117.1 +/- 15.1 vs. 125.1 +/- 21.7 b.p.m.; p < 0.05), blood pressure (167.6 +/- 18 vs. 180.3 +/- 18 mm Hg; p < 0.01) and workload (93.8 +/- 17.4 vs. 121.1 +/- 23.2 W; p < 0.01). The relationship between ST depression and RPP (RPP/STmax) was favorably modified after training. The ratio RPP/STmax improved significantly from 143.6 +/- 49.4 to 209.1 +/- 69.5 (p < 0.0001). These findings support the hypothesis that a 1-year moderate-to-high training program in some patients following myocardial infarction can elicit adaptations that may well be attributed, at least in part, to an improvement in coronary blood flow.

Adult↗

PubMed2002

A comparative analysis of the effects of exercise training on contractile responses in fast- and slow-twitch rat skeletal muscles.

The effects of 5 weeks treadmill-exercise training on isometric tension and contractile proteins were studied in intact and skinned isolated small bundles of rat skeletal soleus and extensor digitorum longus (edl) fibers. In soleus and edl muscles, 5 weeks exercise training: (i) increased twitch amplitude by 25% and 8%, respectively, without modification in the time-to-peak tension and the time constant of relaxation, (ii) increased the amplitude of K(+) contracture by 93% and 88%, respectively, and accelerated its relaxation by 17% and 43%, respectively, and (iii) increased the amplitude of caffeine contractures (soleus: 0.5 mM: 86%, 10 mM: 77%; edl: 0.5 mM: 89%, 10 mM: 87%). In conclusion, changes in contractile responses were associated with shifts in the steady state inactivation curves and in the voltage-dependent activation curve to a more negative potential, with increases in soleus and edl caffeine sensitivity, without changes in the Ca(2+) sensitivity of contractile proteins and myosin heavy chain isoforms.

Animals↗

PubMed1988

Depressed in vivo myocardial reactivity to dobutamine in streptozotocin diabetic rats: influence of exercise training.

To assess the effects of chronic diabetes on in vivo myocardial reactivity to beta 1 adrenergic receptor stimulation and to evaluate the therapeutic effect of exercise training in preventing the cardiac abnormalities induced by diabetes four groups of rats were studied: sedentary control, trained control, sedentary diabetic, and trained diabetic. Trained rats were adapted to treadmill running before the induction of diabetes with streptozotocin 55 mg.kg-1 iv. The duration, speed, and grade of exercise were then progressively increased during eight weeks of training until the rats could run for 90 min at 18 m/min, 5% grade. A training effect was confirmed by an increase in plantaris muscle cytochrome oxidase activity. In vivo cardiac contractile performance was assessed by intracardiac catheterisation. Heart rate, left intraventricular peak systolic pressure, and positive and negative dP/dt were measured under basal conditions and after the intravenous administration of dobutamine 10(-10) to 5 x 10(-7) mol.kg-1 body weight. Under basal conditions, there were no differences among the four groups in left intraventricular peak systolic pressure, positive dP/dt, and heart rate, but negative dP/dt was lower in both diabetic groups. The response to dobutamine of the sedentary diabetic group, as reflected in the measured cardiodynamic variables, was significantly attenuated compared with that of the sedentary control group. Exercise training tended to improve cardiac function towards the level detected in the sedentary controls; however, the differences between sedentary and trained diabetic groups were not statistically significant. Exercise training also did not significantly alter the response of the control group to dobutamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Exercise training produces nonuniform increases in arteriolar density of rat soleus and gastrocnemius muscle.

OBJECTIVE: Exercise training has been shown to increase regional blood flow capacity to muscle tissue containing fibers that experience increased activity during exercise. The purpose of this study was to test the hypothesis that the increased blood flow capacity is partially the result of increases in arteriolar density (number of arterioles/mm2 of tissue), specifically in skeletal muscle tissue, with the largest relative increase in muscle fiber activity during training bouts. METHODS: This hypothesis was tested by comparing and contrasting the effects of endurance exercise training (ET) and interval sprint training (IST) on arteriolar density in soleus muscle (S) red (Gr) and white (Gw) portions of gastrocnemius muscle of male Sprague Dawley rats. ET rats completed 10 weeks of treadmill training 30 m/min, 15% grade, 60 min/day, 5 days/week, while IST rats completed 10 weeks of IST consisting of six 2.5-min exercise bouts, with 4.5-min rest between bouts (60 m/min, 15% incline), 5 days/week. The hypothesis would be supported if ET increased arteriolar density in S and Gr and if IST increased arteriolar density in Gw. RESULTS: ET increased arteriolar density above values of sedentary rats (SED) in both the Gw (ET = 0.93 +/- 0.19 arterioles/microm2; SED = 0.44 +/- 0.09 arterioles/microm2) and Gr (ET = 0.97 +/- 0.1 arterioles/microm2; SED = 0.51 +/- 0.06 arterioles/microm2) muscles, but not in S (ET = 1.69 +/- 0.45 arterioles/microm2; SED = 1.51 +/- 0.34 arterioles/microm2) muscle. In contrast, IST did not alter arteriolar density in Gw or Gr muscle tissue. Although arterial wall thickness was greater in S (3.95 +/- 0.40 microm) and Gr (6.24 +/- 0.59 microm) than Gw (2.76 +/- 0.18 microm), neither ET or IST altered mean wall thickness in either muscle. CONCLUSION: Increases in blood flow capacity produced in Gr and Gw by ET appear to be due in part to increased arteriolar density. In contrast, increased arteriolar density does not contribute to increased blood flow capacity of Gw in IST rats.

Adaptation, Physiological↗

PubMed1991

The effects of moderate exercise training on immune response.

The relationship between moderate exercise training (ET) (five 45-min sessions per week, brisk walking at 60 heart rate reserve for 15 wk) and changes in immune system variables and function was investigated in a group of 36 sedentary, mildly obese women. The study was conducted using a two (exercise (EX) and nonexercise (NEX) groups) by three (baseline, 6 wk, and 15 wk testing sessions) factorial design, with data analyzed using repeated measures ANOVA. The pattern of change over time between groups for number of peripheral blood lymphocytes (total), T cells (CD5), B cells (CD20), and serum IgG, IgA, and IgM levels was significantly different. This was not the case for spontaneous blastogenesis or number of T helper/inducer cells (CD4) or T cytotoxic/suppressor cells (CD8). Within-EX-group changes were characterized by significant decreases in percentage and number of total lymphocytes, and in T cell number after 6 wk, and significant increases in each of the serum immunoglobulins after both 6 and 15 wk of training. B cell number increased significantly in NEX subjects relative to baseline values at both 6 and 15 wk, with no significant changes experienced in EX subjects. In summary, these data suggest that moderate ET is not associated with an improvement in lymphocyte function but is associated with a 20% increase in serum immunoglobulins and several small changes in circulating numbers of immune system variables, highlighted by significant decreases in circulating numbers of lymphocytes, particularly the T cell subpopulation. These changes were especially apparent after 6 wk of training, with some attenuation by 15 wk.

Adult↗

PubMed1992

Exercise training improves cardiac function after ischemia in the isolated, working rat heart.

The aim of this study was to determine whether exercise training produces a myocardium intrinsically more tolerant to ischemic-reperfusion injury. Male Fischer 344 rats were treadmill trained for 11-16 wk at one of the following intensities: LOW (20 m/min, 0% grade, 60 min/day), moderate (MOD; 30 m/min, 5% grade, 60 min/day) or intensive (INT; 10 bouts of alternating 2-min runs at 16 and 60 m/min, 5% grade). Cardiac function was evaluated both before and after 25 min of global, zero-flow ischemia in the isolated, working heart model. Compared to hearts from sedentary (SED) rats, postischemic cardiac output (CO) and work were significantly higher in all trained groups. Percent recovery of CO (relative to preischemia) was 36.0 +/- 7.1 in SED and 61.2 +/- 6.5, 68.1 +/- 9.3, and 73.2 +/- 5.0 in LOW, MOD, and INT, respectively. Postischemic increases in stroke volume with increased preload and cardiac work at high work load were significantly higher in INT compared with SED. Coronary flow during initial retrograde reperfusion was significantly enhanced with training and correlated with subsequent recovery of CO (R2 = 0.613). Furthermore, trained hearts had higher phosphocreatine (P less than 0.05) and ATP (P less than 0.01) contents after 45 min reperfusion. It is concluded that exercise training results in an intrinsic myocardial adaptation, allowing greater recovery of cardiac pump function after global ischemia in the isolated rat heart.

Adenosine Triphosphate↗

PubMed2004

The effects of aging and exercise training on endothelin-1 vasoconstrictor responses in rat skeletal muscle arterioles.

OBJECTIVES: The incidence of cardiovascular disease increases with advancing age. Vascular dysfunction has been linked to cardiovascular disease and aging, although most research has focused on endothelium-dependent vasodilator dysfunction. Another possible mechanism for this vascular dysfunction with aging is enhanced vasoconstrictor responsiveness of the resistance vasculature, and in particular, reactivity of arterioles to endothelin-1 (ET-1). We hypothesized that vasoreactivity to ET-1 would be greater in skeletal muscle arterioles from old rats, and that endurance exercise training would abolish differences in ET-1 responsiveness between young and old animals. METHODS: Young sedentary (YS; 4 months; n=18), old sedentary (OS; 24 months; n=17), young trained (YT; n=9) and old trained (OT; n=7) male Fischer 344 rats were used. Training modality was treadmill exercise at 15 m/min up a 15 degrees incline, 1 h/day, 5 days/week, for 12 weeks. Soleus and white gastrocnemius muscle first-order arterioles were isolated for in vitro experimentation. Intraluminal diameter was measured in response to increasing concentrations of ET-1 (10(-11) to 10(-8) M) or KCl (10-100 mM) in arterioles with an intact or denuded endothelium and with and without an ETA (BQ-123 [10(-6) M]) or ETB (BQ-788 [10(-8) M]) receptor antagonist present. RESULTS: There was an age-associated increase in gastrocnemius vasoconstrictor responsiveness and sensitivity to ET-1 in arterioles with intact endothelium (ET-1 EC50: YS, 5.2 E(-9)+/-1.1 E(-9) M; OS, 2.0 E(-9)+/-0.8 E(-9) M); neither removal of the endothelium nor ETB blockade abolished this difference in arteriolar sensitivity to ET-1 between old and young rats. In contrast, ETA inhibition abolished the greater sensitivity (EC50) of arterioles from old animals (ET-1 EC50: YS, 10 E(-9)+/-0.7 E(-9) M; OS, 10 E(-9)+/-1.5 E(-9) M). Gastrocnemius muscle arterioles exhibited an age-related reduction in KCl-induced vasoconstriction which was abolished with the removal of the endothelium. Soleus muscle arteriolar responses to ET-1 and KCl were unaffected by aging. Additionally, exercise training had no effect on ET-1 vasoconstriction of soleus or gastrocnemius muscle arterioles. CONCLUSIONS: Aging results in an augmented gastrocnemius muscle arteriolar vasoconstriction to ET-1 which is mediated through an enhanced ETA receptor signaling pathway and not through an ETB receptor mechanism associated with either the endothelium or vascular smooth muscle. These findings suggest that enhanced vascular ET-1 sensitivity in fast-twitch skeletal muscles may play a role in the vascular dysfunction that is often associated with old age.

Aging↗

PubMed1988

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.

Animals↗

PubMed1992

Functional electrical stimulation leg cycle ergometer exercise: training effects on cardiorespiratory responses of spinal cord injured subjects at rest and during submaximal exercise.

This study investigated the cardiorespiratory (CR) responses at rest and during submaximal (0-W) functional electrical stimulation (FES)-induced leg cycle ergometer (LCE) exercise prior to and following a progressive intensity FES-LCEa exercise training program in spinal cord injured (SCI) subjects. Seven quadriplegics and six paraplegics participated in FES-LCE training three sessions per week for approximately 12 weeks (36 sessions). Monitored CR responses, including oxygen uptake (VO2), pulmonary ventilation (VE), respiratory exchange ratio (RER), arteriovenous O2 difference (a-vO2), blood pressure (BP), heart rate (HR), stroke volume (SV), total peripheral resistance (TPR), and cardiac output (Q), were determined before and after training. Power output (PO) increased significantly (p < .05) over the duration of the training program, indicating increased in strength and endurance of the paralyzed muscles used. Respiratory responses were not significantly altered by training in both groups. FES-LCE training significantly increased resting HR and SBP in quadriplegics and lowered SBP, DBP, and MAP in paraplegics. In both groups, HR and BP during submaximal exercise significantly decreased and SV and Q significantly increased after completion of the training program. These results suggest that FES-LCE training improves peripheral muscular and central cardiovascular fitness in SCI subjects. Posttraining HR and BP may also be more stable in quadriplegics and alleviate hypotension. This therapeutic exercise may ultimately lead to improved rehabilitation outcome and reduced stress during activities of daily living, and possibly reduce the risks for secondary CR disabilities.

Adult↗

PubMed1994

Exercise training improves metabolic response after ischemia in isolated working rat heart.

Hearts from treadmill-trained and sedentary rats were perfused in the working heart mode. Mechanical and metabolite status was evaluated before ischemia, after 25 min of global ischemia, and after 30 min of retrograde reperfusion. After reperfusion, hearts from trained rats were found to have better recovery of contractile function, lower diastolic stiffness, greater efficiency of work, and greater extracellular calcium responsiveness than hearts from sedentary rats. Training had no significant impact on bioenergetic status before or at the end of ischemia. However, after reperfusion, both phosphocreatine and ATP were significantly higher in hearts from trained rats than from sedentary control rats. Mitochondrial function in both subsarcolemmal and intermyofibrillar subpopulations was unaffected by ischemia-reperfusion. 45Ca2+ uptake during reperfusion was significantly higher in hearts from sedentary rats than from exercise-trained rats. No differences were found in free radical production or tolerance due to training. Therefore, hearts from exercise-trained rats demonstrated an increased metabolic tolerance to ischemic-reperfusion damage, which may contribute to the improved postischemic functional recovery.

Animals↗

PubMed2005

Exercise training to improve motor performance in chronic stroke: effects of a community-based exercise program.

The purpose of this study was to investigate the feasibility and efficacy of an exercise program offered by a community organization on motor performance in individuals with chronic stroke. Twenty hemiparetic individuals at least 6 months after a stroke and discharged from all rehabilitation services enrolled in the study. They took part in an 8-week group program (two times per week) aimed at improving balance, mobility, coordination, walking endurance and strength on the hemiparetic side through various functional exercises. Pre- and post-exercise assessments included the stroke impairment assessment set, the Berg balance scale, the step test, the timed-up-and-go and the 6 min walk. Results showed significant improvements (P<0.008) in all of the above tests, excluding the 6 min walk, after completion of the exercise training. Correlation analyses revealed that the individuals' age and time since injury were poorly related to the improvement in performance. It is concluded that an exercise program offered by a community organization can lead to improvement in motor performance of individuals with chronic stroke. To prevent decline in motor performance, community-based exercise programs should thus be made available for stroke patients discharged from rehabilitation services.

Age Factors↗