Gastrointestinal function during exercise: comparison of water, sports drink, and sports drink with caffeine.
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Caffeine is suspected to affect gastrointestinal function. We therefore investigated whether supplementation of a carbohydrate-electrolyte solution (CES) sports drink with 150 mg/l caffeine leads to alterations in gastrointestinal variables compared with a normal CES and water using a standardized rest-exercise-rest protocol. Ten well-trained subjects underwent a rest-cycling-rest protocol three times. Esophageal motility, gastroesophageal reflux, and intragastric pH were measured by use of a transnasal catheter. Orocecal transit time was measured using breath-H(2) measurements. A sugar absorption test was applied to determine intestinal permeability and glucose absorption. Gastric emptying was measured via the (13)C-acetate breath test. In the postexercise episode, midesophageal pressure was significantly lower in the CES + caffeine trial compared with the water trial (P = 0.017). There were no significant differences between the three drinks for gastric pH and reflux during the preexercise, the cycling, and the postexercise episode, respectively. Gastric emptying, orocecal transit time, and intestinal permeability showed no significant differences between the three trials. However, glucose absorption was significantly increased in the CES + caffeine trial compared with the CES trial (P = 0.017). No significant differences in gastroesophageal reflux, gastric pH, or gastrointestinal transit could be observed between the CES, the CES + caffeine, and the water trials. However, intestinal glucose uptake was increased in the CES + caffeine trial. (+info)
Physical activity and coronary heart disease in men: The Harvard Alumni Health Study.
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BACKGROUND: The quantity and intensity of physical activity required for the primary prevention of coronary heart disease (CHD) remain unclear. Therefore, we examined the association of the quantity and intensity of physical activity with CHD risk and the impact of other coronary risk factors. METHODS AND RESULTS: We followed 12 516 middle-aged and older men (mean age 57.7 years, range 39 to 88 years) from 1977 through 1993. Physical activity was assessed at baseline in kilojoules per week (4.2 kJ=1 kcal) from blocks walked, flights climbed, and participation in sports or recreational activities. During follow-up, 2,135 cases of incident CHD, including myocardial infarction, angina pectoris, revascularization, and coronary death, occurred. Compared with men expending <2,100 kJ/wk, men expending 2,100 to 4,199, 4,200 to 8,399, 8,400 to 12,599, and >/=12,600 kJ/wk had multivariate relative risks of 0.90, 0.81, 0.80, and 0.81, respectively (P: for trend=0.003). When we considered the independent effects of specific physical activity components, only total sports or recreational activities (P: for trend=0.042) and vigorous activities (P: for trend=0.02) were inversely associated with the risk of CHD. These associations did not differ within subgroups of men defined by coronary risk factors. Finally, among men with multiple coronary risk factors, those expending >/=4,200 kJ/wk had reduced CHD risk compared with men expending <4,200 kJ/wk. CONCLUSIONS: Total physical activity and vigorous activities showed the strongest reductions in CHD risk. Moderate and light activities, which may be less precisely measured, showed nonsignificant inverse associations. The association between physical activity and a reduced risk of CHD also extends to men with multiple coronary risk factors. (+info)
Physical activity and coronary heart disease risk in men: does the duration of exercise episodes predict risk?
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BACKGROUND: Physical activity is associated with a decreased risk of coronary heart disease (CHD). However, it is unclear whether the duration of exercise episodes is important: Are accumulated shorter sessions as predictive of decreased risk as longer sessions if the same amount of energy is expended? METHODS AND RESULTS: In the Harvard Alumni Health Study, we prospectively followed 7307 Harvard University alumni (mean age 66.1 years) from 1988 through 1993. At baseline, men reported their walking, stair climbing, and participation in sports or recreational activities. For each of the latter activities, they also reported the frequency and average duration per episode. During follow-up, 482 men developed CHD. In age-adjusted analysis, a longer duration of exercise episodes predicted lower CHD risk (P: trend=0.04). However, after total energy expended on physical activity and potential confounders was accounted for, duration no longer had an independent effect on CHD risk (P: trend=0.25); that is, longer sessions of exercise did not have a different effect on risk compared with shorter sessions, as long as the total energy expended was similar. In contrast, higher levels of total energy expenditure significantly predicted decreased CHD risk in both age-adjusted (P: trend=0.009) and multivariate (P: trend=0.046) analyses. CONCLUSIONS: These data clearly indicate that physical activity is associated with decreased CHD risk. Furthermore, they lend some support to recent recommendations that allow for the accumulation of shorter sessions of physical activity, as opposed to requiring 1 longer, continuous session of exercise. This may provide some impetus for those sedentary to become more active. (+info)
Cardiovascular screening of student athletes.
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Each year, a number of children and adolescents die suddenly from cardiac problems that are associated with a small subgroup of disorders and high-risk behaviors. While sudden cardiac death in any child or adolescent is distressing, it can be particularly devastating when it occurs in a seemingly healthy young athlete. Although uncommon in competitive sports, sudden death is a catastrophe that physicians who care for athletes should attempt to prevent. To prevent the occurrence of sudden death or cardiovascular disease progression in young athletes, the American Academy of Family Physicians, American Academy of Pediatrics, American College of Cardiology, American College of Sports Medicine, American Heart Association, American Medical Society for Sports Medicine, American Orthopaedic Society for Sports Medicine and American Osteopathic Academy of Sports Medicine have developed or endorsed recommendations for cardiovascular screening of student athletes as part of a comprehensive sports preparticipation physical evaluation (PPE). Knowledge and understanding of these recommendations can help physicians make informed decisions about the eligibility of an athlete to participate in a particular sport and encourage development of a more uniform PPE screening process. (+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)
Coronary vasodilator capacity and epicardial vessel remodeling in physiological and hypertensive hypertrophy.
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The aim of this study was to compare resting coronary flow velocity, determinants of myocardial oxygen demand, and coronary vasodilator capacity in subjects with physiological, exercise-induced, and hypertensive left ventricular hypertrophy. Sixteen healthy sedentary men, 16 endurance athletes, and 16 hypertensive subjects (mean+/-SEM for left ventricular mass index: 94.9+/-5.5, 184.6+/-8.4, 154.4+/-9.5 g/m(2), respectively) were studied by transesophageal and transthoracic Doppler echocardiography. Coronary flow velocity in left anterior descending artery and cross-sectional area of left main artery were assessed at rest and during dipyridamole-induced vasodilation. Myocardial oxygen demand was estimated through rate-pressure product, left ventricular wall stress, and inotropic function. Coronary flow reserve and minimum coronary resistance were comparable to those of sedentary men in athletes (mean+/-SEM: 3. 23+/-0.16 versus 3.60+/-0.18 and 0.96+/-0.06 versus 1.04+/-0.04 mm Hg. s. cm(-1)), while in hypertensive subjects they were decreased and increased, respectively (mean+/-SEM: 2.31+/-0.08 and 1.21+/-0.10 mm Hg. s. cm(-1); P:<0.05 for both). Resting flow velocity was directly related to rate-pressure product in sedentary men and athletes and also to wall stress in athletes, while these correlations were absent in hypertensives. Dilation of left main artery after dipyridamole was significantly higher in athletes than in sedentary men and hypertensive subjects (mean+/-SEM for area change: 32.9+/-3.7% versus 12.8+/-2.5% and 6.4+/-3.3%; P:<0.05 and 0.01). These data indicate that vasodilator capacity of coronary microcirculation is not impaired in athletes with physiological hypertrophy, in contrast to hypertensive patients. The relationship between resting flow velocity and determinants of oxygen demand is preserved in physiological hypertrophy but missing in hypertensive hypertrophy. Furthermore, the vasodilator capacity of coronary macrocirculation is also enhanced in exercise-trained subjects. (+info)
Physical activity and mortality in older men with diagnosed coronary heart disease.
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BACKGROUND: We have studied the relations between physical activity, types of physical activity, and changes in physical activity and all-cause mortality in men with established coronary heart disease (CHD). METHODS AND RESULTS: In 1992, 12 to 14 years after the initial screening (Q1) of 7735 men 40 to 59 years of age from general practices in 24 British towns, 5934 (91% of available survivors, mean age 63 years) provided further information on physical activity (Q92) and were followed up for 5 years; 963 had a physician's diagnosis of CHD (myocardial infarction or angina). After exclusions, there were 772 men with established CHD, 131 of whom died of all causes. The lowest risks for all-cause and cardiovascular mortality were seen in light and moderate activity groups (adjusted relative risk compared with inactive/occasionally active: light, 0.42 (0.25, 0.71); moderate, 0.47 (0.24, 0.92); and moderately vigorous/vigorous, 0.63 (0.39, 1.03). Recreational activity of >/=4 hours per weekend, moderate or heavy gardening, and regular walking (>40 min/d) were all associated with a significant reduction in all-cause mortality. Nonsporting activity was more beneficial than sporting activities. Men sedentary at Q1 who began at least light activity by Q92 showed lower mortality rates on follow-up than those who remained sedentary (relative risk 0.58, 95% CI 0.33 to 1.03; P:=0.06). CONCLUSIONS: Light or moderate activity in men with established CHD is associated with a significantly lower risk of all-cause mortality. Regular walking and moderate or heavy gardening were sufficient to achieve this benefit. (+info)
Coronary flow reserve is supranormal in endurance athletes: an adenosine transthoracic echocardiographic study.
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OBJECTIVE: To compare coronary flow reserve in endurance athletes and healthy sedentary controls, using adenosine transthoracic echocardiography. METHODS: 29 male endurance athletes (mean (SD) age 27.3 (6.6) years, body mass index (BMI) 22.1 (1.9) kg/m(2)) and 23 male controls (age 27.2 (6.1) years, BMI 23.9 (2.6) kg/m(2)) with no coronary risk factors underwent transthoracic echocardiographic assessment of distal left anterior descending coronary artery (LAD) diameter and flow, both at rest and during intravenous adenosine infusion (140 microg/kg/min). RESULTS: Distal LAD diameter and flow were adequately assessed in 19 controls (83%) and 26 athletes (90%). Distal LAD diameter in athletes (2.04 (0.25) mm) was not significantly greater than in sedentary controls (1.97 (0.27) mm). Per cent increase in LAD diameter following 400 microg sublingual nitrate was greater in the athletes than in the controls, at 14.1 (7. 2)% v 8.8 (5.7)% (p < 0.01). Left ventricular mass index in athletes exceeded that of controls, at 130 (19) v 98 (14) g/m(2) (p < 0.01). Resting flow among the athletes (10.6 (3.1) ml/min; 4.4 (1.2) ml/min/100 g left ventricular mass) was less than in the controls (14.3 (3.6) ml/min; 8.2 (2.2) ml/min/100 g left ventricular mass) (both p < 0.01). Hyperaemic flow among the athletes (61.9 (17.8) ml/min) exceeded that of the controls (51.1 (14.6) ml/min; p = 0.02), but not when corrected for left ventricular mass (25.9 (5.6) v 28.5 (7.4) ml/min/100 g left ventricular mass; NS). Coronary flow reserve was therefore substantially greater in the athletes than in the controls, at 5.9 (1.0) v 3.7 (0.7) (p < 0.01). CONCLUSIONS: Coronary flow reserve in endurance athletes is supranormal and endothelium independent vasodilatation is enhanced. Myocardial hypertrophy per se does not necessarily impair coronary flow reserve. Adenosine transthoracic echocardiography is a promising technique for the investigation of coronary flow reserve. (+info)