Neuromuscular adaptations to concurrent training in the elderly: effects of intrasession exercise sequence

The aim of this study was investigate the effects of different intrasession exercise orders in the neuromuscular adaptations induced by concurrent training in elderly. Twenty-six healthy elderly men (64.7?±?4.1 years), were placed into two concurrent training groups: strength prior to (SE, n?=?13) or after (ES, n?=?13) endurance training. Subjects trained strength and endurance training during 12 weeks, three times per week performing both exercise types in the same training session. Upper and lower body one maximum repetition test (1RM) and lower-body isometric peak torque (PTiso) and rate of force development were evaluated as strength parameters. Upper and lower body muscle thickness (MT) was determined by ultrasonography. Lower-body maximal surface electromyographic activity of vastus lateralis and rectus femoris muscles (maximal electromyographic (EMG) amplitude) and neuromuscular economy (normalized EMG at 50 % of pretraining PTiso) were determined. Both SE and ES groups increased the upper- and lower-body 1RM, but the lower-body 1RM increases observed in the SE was higher than ES (35.1?±?12.8 vs. 21.9?±?10.6 %, respectively; P?<?0.01). Both SE and ES showed MT increases in all muscles evaluated, with no differences between groups. In addition, there were increases in the maximal EMG and neuromuscular economy of vastus lateralis in both SE and ES, but the neuromuscular economy of rectus femoris was improved only in SE (P?<?0.001). Performing strength prior to endurance exercise during concurrent training resulted in greater lower-body strength gains as well as greater changes in the neuromuscular economy (rectus femoris) in elderly.     

Echo intensity is associated with skeletal muscle power and cardiovascular performance in elderly men

The purpose of the present study was to investigate the relationship between echo intensity, neuromuscular and cardiorespiratory performances in the elderly. Thirty-one healthy elderly men (65.5±5.0) participated in this study. Echo intensity of rectus femoris and quadriceps femoris muscle thicknesses was determined by ultrasound images. Lower-body isometric and isokinetic peak torques (60, 180 and 360°(.s-1)), as well as rate of force development were evaluated as strength parameters. In addition, torque per unit of muscle mass was evaluated by the quotient between isometric peak torque of the knee extensors and the quadriceps femoris muscle thickness. The peak oxygen uptake (VO(2peak)), maximum aerobic workload (W(máx)), absolute (VT(1) and VT(2)) ventilatory thresholds, as well as workloads at VT(1) and VT(2) (W(VT1) and W(VT2)) were evaluated during a maximal incremental test on a cycle ergometer. There were significant negative correlations between the individual values of echo intensity with the corresponding individual values of isometric and isokinetic peak torques (60, 180 and 360°(.s-1)) (r=-0.48 to r=-0.64; P<0.05), as well as with W(VT1) (r=-0.46) and W(VT2) (r=-0.50) (P<0.05). In addition, significant positive correlations were observed between torque per unit of muscle mass and cardiovascular parameters (r=0.52 to r=0.60; P<0.001). The present results suggest that the echo intensity analysis using computer-aided gray-scale analysis is a low cost, easily accessible, and a safe method to evaluate the muscle quality, and may contribute to the research of neuromuscular and cardiovascular performances in the elderly.     

Efficiency of twice weekly concurrent training in trained elderly men

This study compared the effects of different weekly training frequencies on the cardiovascular and neuromuscular adaptations induced by concurrent training in previously trained elderly. After 20 weeks of combined strength and endurance training, twenty-four healthy elderly men (65 ± 4 years) were randomly placed into two frequency training groups: strength and endurance training performed twice a week (SE2, n = 12); or, strength and endurance training performed three times per week (SE3, n = 12). The interventions lasted 10 weeks and each group performed identical exercise intensity and volume per session. Before and after the exercise training, one maximum repetition test (1RM), isometric peak torque (PT), maximal surface electromyographic activity (EMG), as well as muscle thickness (MT) were examined. Additionally, peak oxygen uptake (VO_2peak), maximum aerobic workload (W_max), first and second ventilatory thresholds (VT₁ and VT₂) were evaluated. There were significant increases in upper and lower-body 1RM, MT, VO_2peak, VT₁ and VT₂, with no differences between groups. There were no changes after training in maximal EMG and isometric peak torque. W_max was improved only in SE3. After 10 weeks of training, twice weekly combined strength and endurance training leads to similar neuromuscular and cardiovascular adaptations as three times per week, demonstrating the efficiency of lower frequency of concurrent training in previously trained elderly men.     

Echocardiographic Doppler evaluation of left ventricular diastolic filling in older, highly trained male endurance athletes

Previously published data have suggested that endurance training does not retard the normative aging impairment of early left ventricular diastolic filling (LVDF). Those studies, suggesting no effect of exercise training, have not examined highly trained endurance athletes or their LVDF responses after exercise. We therefore compared LVDF characteristics in a group of older highly trained endurance athletes (n = 12, mean age 69 years, range 65-75) and a group of sedentary control subjects (n = 12, mean age 69 years, range 65-73) with no cardiovascular disease. For all subjects, M-mode and Doppler echocardiographic data were obtained at rest. After baseline studies, subjects underwent graded, maximal cardiopulmonary treadmill exercise testing using a modified Balke protocol. Breath-by-breath respiratory gas analysis and peak exercise oxygen consumption (VO(2)max) measurements were obtained. Immediately after exercise and at 3-6 minutes into recovery, repeat Doppler echocardiographic data were obtained for determination of LVDF parameters. VO(2)max (44 +/-6.3 vs 27+/-4.2 ml/kg/min, P<0.001), oxygen consumption at anaerobic threshold (35+/-5.4 vs 24+/-3.8 ml/kg/min, P<0.001), exercise duration (24+/-3 vs 12+/-6 minutes, P<0.001), and left ventricular mass index (61+/-13 vs 51+/-7.8 kg/m(2), P<0.05) were greater in endurance athletes than in sedentary control subjects, whereas body mass index was lower (22+/-1.7 vs 26+/-3.4 kg/m(2), P<0.001). No differences in any of the LVDF characteristics were observed between the groups with the exception of a trend toward a lower atrial filling fraction at rest in the endurance athlete group versus the control subjects (P = 0.07). High-intensity endurance exercise training promotes exceptional peak exercise oxygen consumption and cardiovascular stamina but does not appear to alter normative aging effects on left ventricular diastolic function.     

The effect of specific inspiratory muscle training on the sensation of dyspnea and exercise tolerance in patients with congestive heart failure.

BACKGROUND: It has been previously shown that the inspiratory muscles of patients with congestive heart failure (CHF) are weaker than those of normal persons. This weakness may contribute to the dyspnea and limit exercise capacity in these patients. The respiratory muscles can be trained for both strength and endurance. HYPOTHESIS: The present study was designed to evaluate the effect of specific inspiratory muscle training (SIMT) on inspiratory muscle performance, lung function, dyspnea, and exercise capacity in patients with moderate heart failure. METHODS: Twenty patients with CHF (NYHA functional class II-III) were recruited for the study. The subjects were randomized into two groups: 10 patients were included in the study group and received SIMT and 10 patients were assigned to the control group and received sham training. Subjects in both groups trained daily, 6 times/week, for one-half h, for 3 months. The subjects started breathing at a resistance equal to 15% of their PImax for 1 week and the resistance was then increased incrementally to 60%. Spirometry, inspiratory muscle strength (assessed by measuring the PImax at residual volume), and endurance (expressed by the relationship between PmPeak and PImax), the 12-min walk test, and peak VO2 were performed before the beginning and at the end of the training period. RESULTS: All patients in the training group showed an increase in the inspiratory muscle strength [mean (+/- standard error of the mean) PImax increased from 46.5 +/- 4.7 to 63.6 +/- 4.0 cm H2O, p < 0.005], and endurance (mean PmPeak/PImax from 47.8 +/- 3.6 to 67.7 +/- 1.7%, p < 0.05), while they remained unchanged in the control group. This was associated in the training group with a small but significant increase in forced vital capacity, a significant increase in the distance walked (458 +/- 29 to 562 +/- 32 m, p < 0.01), and an improvement in the dyspnea index score. No statistically significant change in the mean peak VO2 was noted in either group. CONCLUSIONS: Specific inspiratory muscle training resulted in increased inspiratory muscle strength and endurance. This increase was associated with decreased dyspnea, increase in submaximal exercise capacity, and no change in maximal exercise capacity. This training may probe to be a complementary therapy in patients with congestive heart failure.     

Resistance exercise dosage in older adults: single- versus multiset effects on physical performance and body composition

OBJECTIVES: To determine whether variation in resistance exercise volume affects muscle function and physical performance response in older adults. DESIGN: A randomized trial with subjects assigned to a single-set (1-SET) or three-set (3-SET) exercise group. SETTING: An exercise facility at the University of Queensland. PARTICIPANTS: Twenty-eight community-dwelling men and women aged 65 to 78. INTERVENTION: Progressive resistance training consisting of seven exercises targeting the major muscle groups of the upper and lower body performed on exercise machines twice weekly for 20 weeks at eight-repetition maximum (RM) intensity. MEASUREMENTS: Muscle function included isotonic muscle strength (1-RM) of the seven exercises, isokinetic and isometric knee extensor strength, and muscle endurance for the chest press and leg press exercises. Physical performance included timed chair rise, usual and fast 6-m walk, 6-m backwards walk, 400-m walk, floor rise to standing, and stair climbing ability. In addition, body composition was determined using dual energy x-ray absorptiometry. RESULTS: Isotonic muscle strength increased in both exercise groups for all seven exercises (P<.01), with the gain in the 3-SET group greater (P<.05) for the seated row, triceps extension, and knee extension (analysis of covariance). Similarly, muscle endurance gains were greater for the 3-SET than the 1-SET group (P<.01), with no significant difference between groups for isokinetic and isometric knee extensor strength. Both groups improved (P<.05) in the chair rise (1-SET, 10.1%; 3-SET, 13.6%), 6-m backwards walk (1-SET, 14.3%; 3-SET, 14.8%), 400-m walk (1-SET, 3.8%; 3-SET, 7.4%), and stair climbing test (1-SET, 7.7%; 3-SET, 6.4%), with the only difference between groups for the 400-m walk (P<.05). There was no difference between groups for change in body composition. CONCLUSION: Resistance training consisting of only single-set exercises is sufficient to significantly enhance muscle function and physical performance, although muscle strength and endurance gains are greater with higher-volume work. These findings have application in designing time-efficient exercise regimens to enhance neuromuscular function in older adults.     

Endurance and strength training in patients with COPD

STUDY OBJECTIVES: The purpose of this study was to compare the effects of endurance training only to endurance plus strength (combined) training in a randomized trial of patients with COPD. METHODS: Twenty-four patients completed the study: 11 patients in the combined training group (FEV(1) 45 +/- 5% predicted), and 13 patients in the endurance training group (FEV(1) 40 +/- 4% predicted) [mean +/- SE]. Muscle strength, quality of life, exercise performance, and quadriceps fatigability were measured before and after rehabilitation. RESULTS: Combined training led to significant improvements in quadriceps (23.6%), hamstring (26.7), pectoralis major (17.5%), and latissimus dorsi (20%) muscle strength. Endurance training alone did not produce significant improvements in muscle strength: quadriceps (1.1% decrease), hamstring (12.2% increase), pectoralis major (7.8% increase), and latissimus dorsi (2.8% decrease). The increase in strength after training was significantly greater in the combined group compared to the endurance group for the quadriceps and latissimus dorsi muscles but not for the hamstring and pectoralis major muscles. Six-minute walk distance, endurance exercise time, and quality of life (as measured by the Chronic Respiratory Questionnaire) significantly increased in both groups after rehabilitation with no significant differences in the extent of improvement between groups. The extent of improvement in quadriceps fatigability after training (assessed by quadriceps twitch force before and after exercise) was not significantly different between groups. CONCLUSION: Strength training can lead to significant improvement in muscle strength in elderly patients with COPD. However, this improvement in muscle strength does not translate into additional improvement in quality of life, exercise performance or quadriceps fatigability compared to that achieved by endurance exercise alone.     

Effects of high-intensity exercise training in a pulmonary rehabilitation programme for patients with chronic obstructive pulmonary disease

BACKGROUND AND OBJECTIVES: The benefits of pulmonary rehabilitation for patients with COPD depend on the intensity of training. Traditional pulmonary rehabilitation programmes (PRPs) do not consistently achieve high-intensity training and have variable training effects. This study examined the effects of high-intensity exercise training on cardiac and pulmonary function in COPD patients. METHODS: Patients with COPD participated in a 6-week, cardiopulmonary exercise test-based PRP. Spirometry, 6-min walking distance and cardiopulmonary exercise test were used to evaluate cardiopulmonary function, respiratory muscle strength and endurance at rest, during exercise and before and after the programme. Patients were encouraged to complete high-intensity exercise with a targeted training intensity of at least 75% maximum oxygen uptake (VO(2)). RESULTS: Thirty-four COPD patients were enrolled into the study; 16 completed the high-intensity training, 18 did not. At the end of the 12-session PRP, submaximal exercise capacity (6-min walking distance, 461.8 +/- 77.2-502.7 +/- 66.9 m, P < 0.001) improved in both the patients who completed high-intensity training and those who did not. Only the patients who completed high-intensity training had significant improvements in FVC (2.47 +/- 0.70-2.70 +/- 0.62 L, P = 0.024) at rest, maximal exercise capacity (peak VO(2), 1001.6 +/- 286.4-1116.1 +/- 320.4 mL/min, P = 0.020) and work efficiency (7.3 +/- 1.4-8.4 +/- 1.8 mL/min/watt, P = 0.026). There was no statistically significant difference between the two groups in the change in the physiological parameters before and after exercise. CONCLUSIONS: Exercise training in a PRP improved submaximal exercise capacity. Only patients who completed high-intensity exercise training showed improvements in maximal exercise capacity, FVC and work efficiency.     

Hydrotherapy--a new approach to improve function in the older patient with chronic heart failure

AIMS: Hydrotherapy, i.e. exercise in warm water, as a rehabilitation program has been considered potentially dangerous in patients with chronic heart failure (CHF) due to the increased venous return caused by the hydrostatic pressure. However, hydrotherapy has advantages compared to conventional training. We studied the applicability of an exercise programme in a temperature-controlled swimming pool, with specific reference to exercise capacity, muscle function, quality of life and safety. METHODS AND RESULTS: Twenty-five patients with CHF (NYHA II-III, age 72.1+/-6.1) were randomised into either 8 weeks of hydrotherapy (n=15), or into a control group (n=10). The training program was well tolerated with no adverse events. Patients in the hydrotherapy group improved their maximal exercise capacity (+6.5 vs.-5.9 W, P=0.001), isometric endurance in knee extension (+4 vs.-9 s, P=0.01) together with an improvement in the performance of heel-lift (+4 vs. -3 n.o., P=<0.01), shoulder abduction (+12 vs. -8 s, P=0.01) and shoulder flexion (+6 vs. +4, P=0.01) in comparison to patients in the control group. CONCLUSION: Physical training in warm water was well tolerated and seems to improve exercise capacity as well as muscle function in small muscle groups in patients with CHF. This new approach broadens the variety of training regimes for older patients with CHF.     

What limits endurance in normal children?

We have compared the results of a standard progressive maximal exercise test to those of an endurance exercise test in 22 healthy school children (13 girls, 9 boys, mean age 14.8 years) in order to examine whether it is possible to extrapolate results from a maximal test to predict their endurance capacity. All children performed a standard progressive maximal exercise test (15 W increments every minute until exhaustion) and an endurance test (individually calculated loads to mimic cycling at 20 km/h against a windforce 5 of Beaufort for 30 minutes) on 2 separate days. In both tests metabolic [oxygen uptake (Vo₂), CO₂ production, blood lactate accumulation], ventilatory [minute ventilation (V_E)], and circulatory variables were measured. From the maximal test the threshold of lactate accumulation (LT) was determined. Thirteen children were capable of enduring the 30 minute exercise (Group l), and 9 could not complete the endurance test (Group 2). These two groups were comparable with respect to age, height, and baseline lung function. Children in Group 2 had a higher mean weight (P < 0.005) than those in Group 1. Eight of the 9 children in Group 2 were girls, whereas Group 1 consisted of 5 girls and 8 boys. There was no significant difference between Group 1 and 2 in the mean values of Vo₂ max, maximal respiratory exchange ratio (R max), V_Emax, LT, oxygen pulse, and other variables obtained during the maximal exercise tests. Lactate accumulation during the endurance test in Group 2 was larger than in Group 1 (P < 0.005). This confirms that lactate metabolism is a key factor that determines endurance capacity. The endurance time also correlated significantly (P < 0.01) with the ratio between V_E and maximal voluntary ventilation (MVV). We conclude that exercise endurance in healthy children correlates with variables related to lactate metabolism. It appears that a load at or lower than the LT can be sustained for 30 minutes in the great majority of healthy children. © 1993 Wiley-Liss, Inc.     

Neuromuscular adaptations to water-based concurrent training in postmenopausal women: effects of intrasession exercise sequence

This study investigated the effects of different exercise sequences on the neuromuscular adaptations induced by water-based concurrent training in postmenopausal women. Twenty-one healthy postmenopausal women (57.14 ± 2.43 years) were randomly placed into two water-based concurrent training groups: resistance training prior to (RA, n = 10) or after (AR, n = 11) aerobic training. Subjects performed resistance and aerobic training twice a week over 12 weeks, performing both exercise types in the same training session. Upper (elbow flexors) and lower-body (knee extensors) one-repetition maximal test (1RM) and peak torque (PT) (knee extensors) were evaluated. The muscle thickness (MT) of upper (biceps brachii) and lower-body (vastus lateralis) was determined by ultrasonography. Moreover, the maximal and submaximal (neuromuscular economy) electromyographic activity (EMG) of lower-body (vastus lateralis and rectus femoris) was measured. Both RA and AR groups increased the upper- and lower-body 1RM and PT, while the lower-body 1RM increases observed in the RA was greater than AR (34.62 ± 13.51 vs. 14.16 ± 13.68 %). RA and AR showed similar MT increases in upper- and lower-body muscles evaluated. In addition, significant improvements in the maximal and submaximal EMG of lower-body muscles in both RA and AR were found, with no differences between groups. Both exercise sequences in water-based concurrent training presented relevant improvements to promote health and physical fitness in postmenopausal women. However, the exercise sequence resistance–aerobic optimizes the strength gains in lower limbs.     

Assessing the effect of exercise training in men with heart failure; comparison of maximal, submaximal and endurance exercise protocols.

AIMS: No consensus exists regarding the most appropriate exercise testing protocol for patients with congestive heart failure. This study describes the effect of exercise training on performance using three different protocols (maximal, submaximal and endurance testing) in patients with heart failure. METHODS AND RESULTS: Thirty men (mean age 67+/-8 years) with congestive heart failure in NYHA class III (mean ejection fraction 32+/-5%) were evaluated prior to and following exercise training. A maximal exercise cycle test with gas exchange measurements, a submaximal 6 min walk test and an endurance treadmill test with blood lactate sampling were used to evaluate exercise capacity after 12 weeks of exercise training. There was a 44.6% (P<0.001) increase in work performed during the maximal cycle test, with no significant increase in peak VO(2). The distance covered by the submaximal 6 min walk test increased by 8.1% (P<0.001). Lactate measured as area under the curve during the matched work intensity treadmill endurance test was reduced by 19.5% (P<0.005). CONCLUSION: We demonstrated a significant improvement in maximal, submaximal and endurance exercise capacity following 12 weeks of exercise training in patients with congestive heart failure. Endurance tests may be more sensitive and appropriate when assessing the efficacy of intervention in this population. Specifically, demonstration of reduced lactate production at matched work intensities suggests more efficient work and decreased dependence on anaerobic metabolism following training. Although maximal cycle tests are commonly used in clinical work, submaximal and endurance testing might be preferable for evaluating new treatment regimens in this population as they are easy to perform, are reproducible, and reflect daily tasks better than the maximal cycle test in this population.     

Moderate-intensity resistance exercise training in patients with chronic heart failure improves strength, endurance, heart rate variability, and forearm blood flow

BACKGROUND: Resistance exercise training was applied to patients with chronic heart failure (CHF) on the basis that it may partly reverse deficiencies in skeletal muscle strength and endurance, aerobic power (VO(2peak)), heart rate variability (HRV), and forearm blood flow (FBF) that are all putative factors in the syndrome. METHODS AND RESULTS: Thirty-nine CHF patients (New York Heart Association Functional Class=2.3+/-0.5; left ventricular ejection fraction 28%+/-7%; age 65+/-11 years; 33:6 male:female) underwent 2 identical series of tests, 1 week apart, for strength and endurance of the knee and elbow extensors and flexors, VO(2peak), HRV, FBF at rest, and FBF activated by forearm exercise or limb ischemia. Patients were then randomized to 3 months of resistance training (EX, n=19), consisting of mainly isokinetic (hydraulic) ergometry, interspersed with rest intervals, or continuance with usual care (CON, n=20), after which they underwent repeat endpoint testing. Combining all 4 movement patterns, strength increased for EX by 21+/-30% (mean+/-SD, P<.01) after training, whereas endurance improved 21+/-21% (P<.01). Corresponding data for CON remained almost unchanged (strength P<.005, endurance P<.003 EX versus CON). VO(2peak) improved in EX by 11+/-15% (P<.01), whereas it decreased by 10+/-18% (P<.05) in CON (P<.001 EX versus CON). The ratio of low-frequency to high-frequency spectral power fell after resistance training in EX by 44+/-53% (P<.01), but was unchanged in CON (P<.05 EX versus CON). FBF increased at rest by 20+/-32% (P<.01), and when stimulated by submaximal exercise (24+/-32%, P<.01) or limb ischemia (26+/-45%, P<.01) in EX, but not in CON (P<.01 EX versus CON). CONCLUSIONS: Moderate-intensity resistance exercise training in CHF patients produced favorable changes to skeletal muscle strength and endurance, VO(2peak), FBF, and HRV.     

Exercise training for heart failure patients improves respiratory muscle endurance,exercise tolerance,breathlessness, and quality of life

PURPOSE: Increased respiratory muscle endurance and peak oxygen consumption (VO(2peak)) induced by respiratory muscle training support the relationship between respiratory muscle function and exercise capacity in patients with heart failure. This raises the question whether exercise-training results in increased respiratory muscle function contributing to an increased exercise tolerance, a decreased perception of breathlessness, and an improved quality of life. METHODS: Prospective cohort analysis was completed on 24 patients with New York Heart Association (NYHA) Class III heart failure [18 men, 6 women; aged = 64 (SD 7.9) years; percent ejection fraction (%EF) = 24.0 (SD 7.8)]. Maximal sustainable ventilatory capacity (MSVC), submaximal and peak exercise responses, perception of breathlessness, and quality of life were measured before (baseline) and after (end of study) 12 weeks of exercise training. RESULTS: As a result of exercise training, VO(2peak) (P=.01) and MSVC (P<.001) increased, with MSVC contributing to a larger proportion of the variability for VO(2peak) at study completion (r=0.57 vs 0.42). Although stroke volume did not increase beyond exercise at 25 W and did not change with exercise training, ventilation decreased during exercise (P<.05), perception of breathing difficulty (P<.05) was reduced, and quality of life was enhanced (P=.008). CONCLUSIONS: Despite no increase in cardiac output and stroke volume, respiratory muscle endurance improved with exercise training, contributing to increased exercise capacity, decreased breathlessness, and decreased perception of breathlessness. Practical implications can include less frequent rest periods and fatigue, greater confidence, maintenance of independence, and enhanced quality of life.     

Markedly improved skeletal muscle function with local muscle training in patients with chronic heart failure

Background: Reduced heart pump function and skeletal muscle abnormalities are considered important determinants for the low physical exercise capacity in chronic heart failure. Because of reduced ventricular function, traditional physical rehabilitation may cause underperfusion and low local work intensity, thereby producing suboptimal conditions for skeletal muscle training. Hypothesis: The study was undertaken to determine the effects of local exercise training, designed as one- or two-legged knee extensor training, on exercise capacity in patients with moderate chronic heart failure. Because such exercise models use only about one quarter to half the muscle mass used in cycle ergometer training, the influence of a restricted circulatory capacity should therefore be limited. Further, we aimed to determine whether or not chronic heart failure skeletal musculature abnormalities are counteracted with such training. Methods: Fourteen patients with chronic heart failure [age 58 ± 3 years, ejection fraction (EF) 28 ±4%] were randomized to two different training protocols three times a week for 8 weeks and compared with a nontraining control group (n = 7, age 62 ± 3, EF 27 ± 3%). Group 2L (n = 7) underwent simultaneous two-legged knee extensor training (about 4 kg working muscle) for 15 min at 65–75% of VO₂ max of the two-legged kick. Group 1L (n = 7) trained each leg at a time for 15 min of continuous one-legged dynamic knee extensor work with the same training load per muscle mass, that is, at 35% of VO₂ max of the two-legged kick (about 2 kg working muscle). Peak VO₂ of two-legged knee extensor exercise (1/min), two-legged endurance (W), and strength (Nm) were determined before and after the training period. The activity of citrate syn-thase (CS) was estimated in tissue samples from the quadriceps femoris muscle. Results: Peak VO₂ did not change with training. Two-legged knee extensor endurance exercise capacity increased by an average of 40–50% (p<0.01) in all training patients in both the 2L and 1L groups, while no change was observed in the control group. Depressed skeletal muscle CS activity increased by 25–35% in both training groups (p<0.01). Strength increased by 16% in the 2L group after training (p<0.05), while no change was seen in the 1L and control groups. Conclusions: Skeletal muscle changes in stable moderate chronic heart failure are not entirely irreversible. A major factor contributing to these changes and to exercise limitation is deconditioning. Local muscle training is efficient and can at least partially improve skeletal muscle function in these patients. Different degrees of local activation, that is, one- or two-legged knee extensor exercise, do not seem to differ in terms of their effect on exercise capacity. Depressed skeletal muscle oxidative capacity adapts to such physical training with increased activity to an extent not different from that for healthy volunteers.     

Effect of respiratory muscle endurance training in patients with COPD undergoing pulmonary rehabilitation

BACKGROUND: Respiratory muscle endurance training (hyperpnea training) has been shown to have beneficial effects in patients with COPD. STUDY OBJECTIVES: The purpose of this study was to determine whether hyperpnea training, when added to an endurance exercise training program, would lead to additional benefits compared with endurance training alone in patients with COPD. SETTING AND PARTICIPANTS: Patients with COPD entering an 8-week outpatient pulmonary rehabilitation program. Fifteen patients (mean [+/- SE] FEV1, 45 +/- 6% predicted) were randomized to combined therapy, and 14 patients (mean FEV1, 44 +/- 4% predicted) were randomized to endurance training. METHODS: Peak exercise capacity, exercise endurance time during constant workload cycle exercise, 6-min walk distance, quality of life as measured by the chronic respiratory questionnaire, respiratory muscle strength and endurance, and quadriceps fatigability were measured before and after endurance or combined training. RESULTS: After rehabilitation, peak exercise capacity, exercise endurance time, 6-min walk distance, and quality of life all increased in both groups, but there was no significant difference in the extent of improvement between groups. Mean respiratory muscle endurance increased to a significantly greater extent in the combined therapy group (17.5 +/- 2.7 vs 8.5 +/- 2.5 min, respectively; p = 0.02). Respiratory muscle strength was significantly increased, and quadriceps fatigability was significantly reduced after rehabilitation in the combined therapy group but not in the endurance training group, but the difference between groups did not reach statistical significance. CONCLUSION: The endurance of the respiratory muscles can be improved by specific training beyond that achieved by endurance training alone in patients with COPD. However, this improvement did not translate into additional improvement in quality of life or exercise performance.     

Effects of a one-year exercise training program in adults over 70 years old: a study with a control group

BACKGROUND AND AIMS: Exercise training is known to improve exercise tolerance in elderly subjects. Therefore the present study aimed at investigating the effects of one year of combined endurance and resistance training in healthy older people. METHODS: After baseline evaluation, subjects were assigned to either the training group (n=24, age 77.2+/-3.6) or the control group (n=16, age 76.1+/-4.8). Subjects in the control group did not change anything in their everyday activities, whereas subjects in the training group underwent moderately intensive combined exercise training, 3 hours a week over the course of one year. Breath-by-breath oxygen uptake and heart rate were measured at each workload during the symptom-limited cardiopulmonary exercise test. Performance on the 6-minute (6-MWT) and 200-meter (200-MWT) walk tests was registered and maximal strength was measured on knee extensor and plantar flexor muscles. RESULTS: After training, oxygen uptake was significantly increased, both at the ventilatory threshold (+11.6%, p<0.01) and at the end of exercise (+14.8%, p<0.001). The distance walked in 6 min (+10%, p<0.001), the time required to cover 200 m (-7.3%, p<0.001) and the maximal muscle strength (+15.2% and +17.4% for knee extensors and plantar flexors respectively, p<0.05) also improved after training. All these parameters had not significantly changed in the control group after the one-year period. CONCLUSIONS: The results of the present study show that one year of combined exercise training is well-tolerated and improves aerobic capacity, performance on field tests and muscle strength in healthy subjects over 70 years old.     

Substrate oxidation during exercise at moderate and hard intensity in middle-aged and young athletes vs sedentary men

This study investigated the combined effects of endurance training and aging on substrate oxidation during exercise. Thirty-one healthy male subjects in 4 groups (8 middle-aged trained cyclists, 8 young trained cyclists, 7 middle-aged sedentary men, and 8 young sedentary men) performed 2 50-minute cycle ergometer exercise tests, below and above (+/-15%) their individual ventilatory threshold (VT). Substrate oxidation was evaluated by indirect calorimetry during the steady-state tests. Aging decreased carbohydrate (CHO) use (P<.05) in all subjects regardless of fitness status or exercise intensity. However, it declined 2-fold less in the trained men (P<.05) and was associated with a stronger epinephrine response (P<.05). During hard-intensity exercise, endurance training increased by 100% CHO use in the older men (P<.05). In the younger men, training increased fat oxidation but did not change CHO oxidation, resulting in a marked decrease in the ratio between CHO and fat used at high-intensity exercise (-93%; P<.05). These data suggest an age-related decline in the use of CHO as an energy source in exercising men, independent of intensity level. This decline, however, is attenuated in well-trained men for exercise intensities above the VT. In view of these findings, we hypothesize that cycling training performed at a specific exercise intensity (ie, 15% above VT) may improve CHO mobilization and use in middle-aged men.     

壳寡糖对运动大鼠心肌组织保护作用的研究

目的: 研究壳寡糖(COS)对大负荷运动大鼠心肌组织的保护作用。方法: 将36只3月龄SPF级SD雄性大鼠随机分为正常对照组、耐力运动组和壳寡糖组,每组12只。耐力运动组和COS治疗组进行6周的跑台训练。24 h后处死大鼠,迅速取出心脏,在光镜和透射电镜下分别观察大鼠心肌组织的形态结构。测定心肌组织和血清超氧化物歧化酶(SOD)和丙二醛(MDA)的水平,SOD活性采用黄嘌呤氧化酶法测定,MDA含量采用TBA缩合比色法测定。结果: COS组大鼠心肌SOD活性（246.38±0.79）较运动组（138.61±1.17）显著增高（P<0.05）,而血清SOD活性（67.92±18.47）较运动组（98.79±16.10）显著降低（P<0.05）;心肌和血清MDA含量（3.64±0.19和4.50±0.74）均较运动组（6.87±0.34和7.86±0.46）显著降低（P<0.05）。COS治疗组大鼠心肌组织和血清中SOD的活性及MDA的含量与正常对照组比较差异无显著性。光镜下观察,运动组大鼠心肌细胞出现不同程度的水肿、变性和坏死;电镜下观察,耐力运动组大鼠心肌细胞损伤明显,肌原纤维模糊、断裂甚至坏死,线粒体肿胀等有形态学改变。COS治疗组大鼠心肌损伤的程度与耐力运动组比较明显减轻,而与正常对照组比较心肌组织的形态结构无明显变化。结论: 大负荷运动可导致大鼠心肌组织、血清抗氧化功能指标改变,心肌组织损伤。COS可提高大负荷运动大鼠心肌组织的抗氧化功能,维持心肌组织的正常形态结构。     

耐力训练对兔心房肌细胞IKAch和心房颤动的影响

目的阐明持续训练相关性心房颤动(AF)的机制,可能为制定新的治疗方法和选择训练方法提供信息。本研究旨在评估兔动物模型中持续训练诱发房颤的机制。方法33只新西兰大耳兔随机分为三组(每组11只):对照组(Group C)、中强度耐力运动训练组(Group M)及高强度耐力运动训练组(Group H),于训练前、训练后8周、12周分别检测各组兔固有心率(IHR);全部训练结束后,各组随机各取6只,共18只兔采用离体心脏Langendorff系统进行1μm/L乙酰胆碱(Ach)+不同浓度阿托品溶液(0 mg/ml^0.002 mg/ml)灌注冠脉,在左心耳置入的电极分别记录相应的心房有效不应期(AERP)及90%动作电位时程(APD90);给予心房早搏程序刺激(S1S2)诱发房颤。灌流完后剪取兔左心房,经PT-PCR技术检测心房肌组织IKAch通道Kir3.1、Kir3.4的mRNA表达。取剩余各组5只实验兔,共15只运用全细胞膜片钳技术,记录心房肌细胞IKAch电流密度。结果长期高强度的耐力运动训练16周后,Group H兔IHR明显低于其他两组;1μm/L Ach背景下,相同剂量阿托品作用下,随着运动强度的增加APD90、AERP相应缩短有统计学差异(Group H vs.Group C and M,P<0.001);同一组内,随着阿托品剂量的增加APD90、AERP相应延长,房颤发生率降低有统计学差异(P<0.05);Group H心房肌细胞IKAch电流密度高于其他两组(Group H vs.Group C、M,P<0.05),Group H心房组织Kir3.1、Kir3.4的mRNA表达量高于其他两组(Group H vs.Group C、M,P<0.05)。结论长期的高强度耐力运动训练促进运动试验兔房颤发生。