Differential effects of high-frequency versus low-frequency exercise training in rehabilitation of patients with coronary artery disease.
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OBJECTIVES: We sought to study the influence of frequency of exercise training during cardiac rehabilitation on functional capacity (i.e., peak oxygen consumption [VO2] and ventilatory anaerobic threshold [VAT]) and quality of life (QoL). BACKGROUND: Although the value of cardiac rehabilitation is now well established, the influence of the different program characteristics on outcome has received little attention, and the effect of frequency of exercise training is unclear. Functional capacity is regularly evaluated by peak VO2 but parameters of submaximal exercise capacity such as VAT should also be considered because submaximal exercise capacity is especially important in daily living. METHODS: Patients with coronary artery disease (n = 130, 114 men; mean age 52 +/- 9 years) were randomized to either a high- or low-frequency program of six weeks (10 or 2 exercise sessions per week of 2 h, respectively). Functional capacity and QoL were assessed before and after cardiac rehabilitation. Global costs were also compared. RESULTS: Compared with baseline, mean exercise capacity increased in both programs: for high- and low-frequency, respectively: peak VO2 = 15% and 12%, Wmax = 18% and 12%, VAT = 35% and 12% (all p < 0.001). However, when the programs were compared, only VAT increased significantly more during the high-frequency program (p = 0.002). During the high-frequency program, QoL increased slightly more, and more individuals improved in subjective physical functioning (p = 0.014). We observed superiority of the high-frequency program, especially in younger patients. Mean costs were estimated at 4,455 and 2,273 Euro, respectively, for the high- and low-frequency programs. CONCLUSIONS: High-frequency exercise training is more effective in terms of VAT and QoL, but peak VO2 improves equally in both programs. Younger patients seem to benefit more from the high-frequency training. (+info)
End-tidal CO2 pressure decreases during exercise in cardiac patients: association with severity of heart failure and cardiac output reserve.
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OBJECTIVES: We measured end-tidal CO2 pressure (PETCO2) during exercise and investigated the relationship between PETCO2 and exercise capacity, ventilatory parameters and cardiac output to determine the mechanism(s) of changes in this parameter. BACKGROUND: It is unclear whether PETCO2 is abnormal at rest and during exercise in cardiac patients. METHODS: Cardiac patients (n = 112) and normal individuals (n = 29) performed exercise tests with breath-by-breath gas analysis, and measurement of cardiac output and arterial blood gases. RESULTS: PETCO2 was lower in patients than in normal subjects at rest and decreased as the New York Heart Association class increased, whereas the partial pressure of arterial CO2 did not differ among groups. Although PETCO2 increased during exercise in patients, it remained lower than in normal subjects. PETCO2 in relation to cardiac output was similar in patients and normal subjects. PETCO2 at the respiratory compensation point was positively correlated with the O2 uptake (r = 0.583, p < 0.0001) and the cardiac index at peak exercise (r = 0.582, p < 0.0001), and was negatively correlated with the ratio of physiological dead space to the tidal volume. The sensitivity and specificity of PETCO2 to predict an inadequate cardiac output were 76.6% and 75%, respectively, when PETCO2 at respiratory compensation point and a cardiac index at peak exercise that were less than the respective control mean-2 SD values were considered to be abnormal. CONCLUSIONS: PETCO2 was below normal in cardiac patients at rest and during exercise. PETCO2 was correlated with exercise capacity and cardiac output during exercise, and the sensitivity and specificity of PETCO2 regarding decreased cardiac output were good. PETCO2 may be a new ventilatory abnormality marker that reflects impaired cardiac output response to exercise in cardiac patients diagnosed with heart failure. (+info)
Increased thermogenic response to food and fat oxidation in female athletes: relationship with VO(2 max).
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The thermogenic response to food (TRF) and substrate oxidation were studied in 12 endurance-trained and 13 untrained female subjects. Energy expenditure and substrate oxidation were calculated by indirect calorimetry before and for 6 h after an oral test meal and after the same meal given intragastrically on a separate occasion. The TRF was calculated after the oral meal, the obligatory component after the intragastric meal (OTRF), and the facultative component from the difference between the two. VO(2 max) was measured on a treadmill and body composition by underwater weighing. The TRF and OTRF were significantly higher in trained than in untrained subjects: 223 +/- 63 vs. 185 +/- 50 kJ/6 h (P < 0.03) and 174 +/- 38 vs. 131 +/- 37 kJ/6 h (P < 0.01) for the TRF and OTRF in trained vs. untrained subjects, respectively. Multiple regression analysis showed that maximum O(2) consumption (VO(2 max)), but not percentage of body fat, was significantly related to OTRF (r =0.68, P < 0.01). Trained subjects had higher fatty acid oxidation than untrained subjects before (0.6 vs. 0.4 mg. kg(-1). min(-1), P < 0.05) and after the oral meal (13 +/- 6 vs. 8 +/- 4 g/6 h P < 0.05). These results demonstrate that 1) TRF is higher in trained than in untrained women; 2) this is due to a higher cost of nutrient digestion, absorption and storage; 3) the difference is related to higher VO(2 max); and 4) fatty acid oxidation is greater in trained women in both the postabsorptive and postprandial states. These observations suggest that endurance training induces metabolic changes that favor leanness. (+info)
Utility of metabolic exercise testing in distinguishing hypertrophic cardiomyopathy from physiologic left ventricular hypertrophy in athletes.
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OBJECTIVES: This study evaluated the role of metabolic (cardiopulmonary gas exchange) exercise testing in differentiating physiologic LVH in athletes from HCM. BACKGROUND: Regular intensive training may cause mild increases in left ventricular wall thickness (LVWT). Although the degree of left ventricular hypertrophy (LVH) is typically less than that seen in hypertrophic cardiomyopathy (HCM), genetic studies have shown that a substantial minority of patients with HCM have an LVWT in the same range. The differentiation of physiologic and pathologic LVH in this "gray zone" can be problematic using echocardiography and electrocardiography alone. METHODS: Eight athletic men with genetically proven HCM and mild LVH (13.9 +/- 1.1 mm) and eight elite male athletes matched for age, size and LVWT (13.4 +/- 0.9 mm) underwent symptom limited metabolic exercise stress testing. Peak oxygen consumption (pVO2), anaerobic threshold, oxygen pulse and respiratory exchange ratios were measured in both groups and compared with those observed in 12 elite and 12 recreational age- and size-matched athletes without LVH. RESULTS: Elite athletes with LVH had significantly greater pVO2 (66.2 +/- 4.1 ml/kg/min vs. 34.3 +/- 4.1 ml/kg/min; p < 0.0001), anaerobic threshold (61.6 +/- 1.8% of the predicted maximum VO2 vs. 41.4 +/- 4.9% of the predicted maximum VO2; p < 0.001) and oxygen pulse (27.1 +/- 3.2 ml/beat vs. 14.3 +/- 1.8 ml/beat; p < 0.0001) than individuals with HCM. A pVO2 >50 ml/kg/min or >20% above the predicted maximum VO2 differentiated athlete's heart from HCM. CONCLUSIONS: Metabolic exercise testing facilitates the differentiation between physiologic LVH and HCM in individuals in the "gray zone." (+info)
Left ventricular diastolic filling and cardiovascular functional capacity in older men.
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We investigated anaerobic threshold (< theta(L)) gas exchange kinetics and maximal oxygen uptake (VO2,max) among older men with reduced left ventricular end-diastolic filling (LVDF). Ten men (mean age, 73 years) with LVDF impairment and low fitness, but without other cardiovascular dysfunction were studied. Treatments compared to control included: 5 days, high intensity exercise training protocol; 5 days, calcium channel blockade (240 mg verapamil); 21 days, detraining/washout; and 5 days, combined treatments. Results indicated no changes in resting left ventricular systolic function with any treatment. Significant resting diastolic function changes included increased early:late flow velocity (control, 0.87; training, 1.28; verapamil, 1.32), and a decreased isovolumic relaxation time (control, 0.10 s; training, 0.08 s; verapamil, 0.08 s). The combined treatments were not additive. Sub-threshold oxygen uptake kinetics (tauVO2, s) were significantly faster following either training or verapamil (tauVO2,control, 62+/-12; tauVO2,training, 44+/-9; tauVO2,verapamil, 48+/-10) and combined treatments (tauVO2, 41+/- 8). V O2,max (ml kg(-1) min(-1)) was significantly increased (control, 21.8+/-2.2; training, 27.3+/-2.2; verapamil, 25.2+/-3.4; combined treatments, 26.9+/-2.3). Increasing ventricular preload with either exercise training or calcium channel blockade was coincident with faster tauVO2 and increased VO2,max. (+info)
Skeletal muscle metabolic and ionic adaptations during intense exercise following sprint training in humans.
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The effects of sprint training on muscle metabolism and ion regulation during intense exercise remain controversial. We employed a rigorous methodological approach, contrasting these responses during exercise to exhaustion and during identical work before and after training. Seven untrained men undertook 7 wk of sprint training. Subjects cycled to exhaustion at 130% pretraining peak oxygen uptake before (PreExh) and after training (PostExh), as well as performing another posttraining test identical to PreExh (PostMatch). Biopsies were taken at rest and immediately postexercise. After training in PostMatch, muscle and plasma lactate (Lac(-)) and H(+) concentrations, anaerobic ATP production rate, glycogen and ATP degradation, IMP accumulation, and peak plasma K(+) and norepinephrine concentrations were reduced (P<0.05). In PostExh, time to exhaustion was 21% greater than PreExh (P<0.001); however, muscle Lac(-) accumulation was unchanged; muscle H(+) concentration, ATP degradation, IMP accumulation, and anaerobic ATP production rate were reduced; and plasma Lac(-), norepinephrine, and H(+) concentrations were higher (P<0.05). Sprint training resulted in reduced anaerobic ATP generation during intense exercise, suggesting that aerobic metabolism was enhanced, which may allow increased time to fatigue. (+info)
Effect of long-term exercise training on blood viscosity during endurance exercise at an anaerobic threshold intensity.
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Blood viscosity (etaB) is low in athletes, but the effect of exercise training on etaB during endurance exercise at an anaerobic threshold (AT) intensity in non-athletes is not well known, although it is known that exercise training sometimes induces the hyperviscosity syndrome. Fourteen subjects were recruited and divided into 2 groups: those who trained at an AT intensity for 30 min/day, 3 times weekly for 1 year (Group T, n=8), and sedentary subjects (Group C, n=6). The test protocol consisted of a single 30-min treadmill exercise at each individual's AT intensity, which was determined in advance. The etaB, plasma viscosity (etaP), and hematocrit were measured just before and at the end of the treadmill exercise. The subjects were not allowed to drink any water before exercise. In the Group C subjects, the hematocrit and etaP increased significantly and the etaB tended to increase. However, in the Group T subjects, the hematocrit and etaP did not increase and the etaB decreased significantly. These data indicate that long-term exercise training attenuates the increase in blood viscosity during exercise. (+info)
Impaired heart rate response during incremental exercise in patients with acute myocardial infarction and after coronary artery bypass grafting: evaluation of coefficients with Karvonen's formula.
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Heart rate (HR) response during exercise in patients with ischemic heart disease was evaluated, and the appropriateness of Karvonen's method for determining rehabilitation exercise target HR was investigated. The study group comprised 24 patients with acute myocardial infarction (AMI) and 37 patients who had undergone coronary artery bypass grafting (CABG). Cardiopulmonary exercise testing (CPX) was performed with a cycle ergometer and changes in HR (deltaHR)/changes in work rate (deltaWR) and interval changes of the coefficient of Karvonen's formula were evaluated. In the AMI group and the CABG group, deltaHR/deltaWR were significantly lower than those of age-matched control subjects (p<0.01). Karvonen's coefficients ranged from 0.37 to 0.54 when calculated from actual peak HR and 0.21 to 0.32 calculated from the predicted peak HR. An impaired HR response was found in patients with AMI and those who had had CABG up to 6 months previously. Because the Karvonen's coefficient values, which ranged from 0.6 to 0.8, were elevated for these patients, and considering the data from the CPX, increased exercise is recommended for such cases. (+info)