Biomedical subjects
Publications and source records attributed to W Haskell.
In a middle-aged patient population, age was associated with stiffer vessels and high-density lipoprotein cholesterol with more elastic vessels. High-density lipoprotein cholesterol may be an indirect indicator of aerobic capacity or of less atherosclerosis, suggesting mechanisms for preserving vascular integrity.
Fifty-one healthy, moderately hypercholesterolemic men and women consuming their usual fat-modified diets completed a 6-month, randomized, double-blind, placebo-controlled, parallel comparison of 15 g/day supplemental water-soluble dietary fiber (WSDF; a mixture of psyllium, pectin, guar gum, and locust bean gum) and an inactive WSDF control (acacia gum). Compliance with the treatments was > 95%, adverse effects were minimal, and body weights remained constant. The WSDF mixture yielded 6.4% and 10.5% reductions in mean plasma total and low-density lipoprotein cholesterol concentrations, respectively, after 8 weeks, which were sustained at 16 and 24 weeks. Mean plasma high-density lipoprotein cholesterol and triglyceride concentrations were unchanged. No significant changes in mean plasma lipid or lipoprotein concentrations were observed in the control group. These data demonstrate that a WSDF approach to cholesterol management is effective as an adjunct to a fat-modified diet in healthy, moderately hypercholesterolemic men and women.
OBJECTIVES: This study attempted to determine whether an intensive multifactor risk reduction program conducted over 4 years would reduce the rate of development of new coronary artery lesions. BACKGROUND: Recent angiographic trials have generally demonstrated that normalization of plasma lipoprotein profiles reduces the rate of progression of established coronary lesions, but limited data exist on how these treatments influence the development of new lesions. METHODS: Three hundred men and women with coronary artery disease were randomized to multifactor risk reduction or usual care. Highly significant improvements in risk factors were achieved by the risk reduction group compared with minimal changes by the usual care group. Quantitative coronary angiography was performed on entry and after 4 years under identical conditions. A decrement in the minimal diameter of visually normal segments > 0.2 mm was considered to indicate new lesion formation. RESULTS: A total of 1,605 segments, representing 257 patients, were considered normal at baseline, with 804 and 801 disease-free segments in the usual care and risk reduction groups, respectively. Ninety-nine segments (6.1%) were identified by follow-up quantitative angiography and two angiographic observers as having new lesion formation (usual care 7.6%, risk reduction 4.7%, p = 0.05). New lesion formation was observed in 41 (31%) of 131 patients in the usual care group and in 29 (23%) of 126 patients in the risk reduction group (p = 0.16), with a mean number of new lesions/patient of 0.47 in the usual care group and 0.30 in the risk reduction group (p = 0.06). Multiple regression analysis identified on-study dietary fat intake as the best correlate with new lesion formation. CONCLUSIONS: These data indicate that intensive multifactor risk reduction tends to diminish the frequency of new coronary lesion formation.
Maximal dynamic exercise results in a postexercise hyperglycemia in healthy young subjects. We investigated the influence of maximal exercise on glucoregulation in non-insulin-dependent diabetic subjects (NIDDM). Seven NIDDM and seven healthy control males bicycled 7 min at 60% of their maximal O2 consumption (VO2max), 3 min at 100% VO2max, and 2 min at 110% VO2max. In both groups, glucose production (Ra) increased more with exercise than did glucose uptake (Rd) and, accordingly, plasma glucose increased. However, in NIDDM subjects the increase in Ra was hastened and Rd inhibited compared with controls, so the increase in glucose occurred earlier and was greater [147 +/- 21 to 169 +/- 19 (30 min postexercise) vs. 90 +/- 4 to 100 +/- 5 (SE) mg/dl (10 min postexercise), P less than 0.05]. Glucose levels remained elevated for greater than 60 min postexercise in both groups. Glucose clearance increased during exercise but decreased postexercise to or below (NIDDM, P less than 0.05) basal levels, despite increased insulin levels (P less than 0.05). Plasma epinephrine and glucagon responses to exercise were higher in NIDDM than in control subjects (P less than 0.05). By use of the insulin clamp technique at 40 microU.m-2.min-1 of insulin with plasma glucose maintained at basal levels, glucose disposal in NIDDM subjects, but not in controls, was enhanced 24 h after exercise. It is concluded that, because of exaggerated counter-regulatory hormonal responses, maximal dynamic exercise results in a 60-min period of postexercise hyperglycemia and hyperinsulinemia in NIDDM. However, this event is followed by a period of increased insulin effect on Rd that is present 24 h after exercise.(ABSTRACT TRUNCATED AT 250 WORDS)
To determine the effects of exercise training programs on psychosocial improvement in uncomplicated postmyocardial infarction patients, 210 male patients hospitalized for an acute myocardial infarction (MI) were randomized to three week symptom limited treadmill (TM) plus home exercise training, TM plus medically supervised gym training, TM without formal exercise program or control, where patients were seen only at six months post MI. Patients in this sample were at low risk for psychosocial disturbance (13% were moderate to severely depressed, 23% reported marital disturbance and 3% were extremely anxious). Patients in the training groups improved from 3 to 26 weeks post MI on all depression and anxiety measures. The gym training group showed a significant reduction on one depression measure compared to no training and on one anxiety measure compared to controls.
The goal of this study was to evaluate the effect of differences in habitual level of physical activity on insulin action in healthy males between 60 and 75 years of age. The study population consisted of 20 non-obese individuals with normal glucose tolerance: 13 older subjects (68 +/- 4 years) not exercising regularly and 7 older subjects (66 +/- 3 years) who exercised regularly. Measurements were made of body mass index (BMI), percentage body fat by underwater weighing, maximal O2 consumption by bicycle ergometry (VO2max), and insulin-stimulated glucose disposal by the insulin clamp technique. The results demonstrated that insulin-stimulated glucose disposal was significantly increased (P less than 0.001) in the normal older subjects who exercised regularly. Furthermore, a direct relationship (r = 0.74, P less than 0.001) existed between maximal aerobic capacity and in vivo insulin action, which was independent of either BMI or percentage body fat. These data are consistent with the view that the extensive variation previously noted in in vivo insulin-stimulated glucose disposal of older subjects is related to differences in habitual physical activity.
Bone mass and metabolic features were studied in 17 women distance runners. Eleven of the women had secondary amenorrhea for 1 to 7 years. Six women have maintained regular menses since menarche. Both groups were matched for aerobic capacity, body fat, exercise intensity, and age of menarche. Mineral density of lumbar spine in the amenorrheic runners was lower than that in the cyclic women and age-matched controls, but higher than that in runners with secondary amenorrhea who are less physically active. Mineral density of the radius was normal in both groups. Running-related fractures were more frequent in amenorrheic women. Metabolic assessment showed no differences between groups, except that serum triiodothyronine was lower in the amenorrheic group, perhaps reflecting low calorie intake. Intense exercise may reduce the impact of amenorrhea on bone mass; however, amenorrheic runners remain at high risk for exercise-related fractures.
The cardiovascular responses to combined static-dynamic effort, postprandial dynamic effort and dynamic effort alone were evaluated by upright bicycle ergometry during equilibrium-gated blood pool scintigraphy in 24 men, mean age 59 +/- 8 years, with chronic ischemic heart disease. Combined static-dynamic effort and the postprandial state elicited a peak cardiovascular response similar to that of dynamic effort alone; work load 643 +/- 156 and 638 +/- 161 vs 650 +/- 153 kg-m/min, respectively; heart rate 147 +/- 14 and 145 +/- 14 vs 143 +/- 17 beats/min; systolic pressure 195 +/- 26 and 200 +/- 25 vs 197 +/- 25 mm Hg; and rate-pressure product 286 +/- 48 and 292 +/- 55 vs 282 +/- 52. Heart rate, intraarterial systolic and diastolic pressures, rate-pressure product and ejection fraction were similar for the three test conditions at the onset of ischemia and at peak effort. The prevalence and extent of exercise-induced ischemic left ventricular dysfunction, ST-segment depression, angina pectoris and ventricular ectopic activity were also similar during the three test conditions. Direct and indirect measurements of systolic and diastolic blood pressure were highly correlated. The onset of ischemic ST-segment depression and angina pectoris correlated as strongly with heart rate alone as with the rate-pressure product during all three test conditions. The cardiovascular response to combined static-dynamic effort and to postprandial dynamic effort becomes more similar to that of dynamic effort alone as dynamic effort reaches a symptom limit. If significant ischemic and arrhythmic abnormalities are absent during symptom-limited dynamic exercise testing, they are unlikely to appear during combined static-dynamic or postprandial dynamic effort. This simplifies, the task of formulating guidelines for physical effort in patients with chronic ischemic heart disease, especially in providing "clearance" to perform avocational and vocational tasks involving combined static-dynamic and postprandial dynamic effort.
We have recently reported improved exercise performance with untrained limbs in 10 men after 11 wk of either arm (N = 5) or leg (N = 5) endurance training. To examine the changes in cardiac function produced by short-term training, we used echocardiography to measure cardiac function at rest, and systolic time intervals (STIs) to measure cardiac function during trained and untrained limb exercise. We repeated all studies after autonomic blockade with atropine and propranolol in order to observe non-autonomic changes in cardiac function. Training had little effect on cardiac size or performance at rest, although with autonomic blockade, cardiac mass increased in the leg-training group and resting left ventricular ejection time (LVET) was prolonged when the two training groups were combined. During submaximal exercise with both trained and undrained limbs and at similar heart rates before and after training, LVET for the combined groups was increased with and without autonomic blockade. This increase in LVET is most consistent with an increased cardiac stroke volume. Short-term endurance training appears to result in improved exercise cardiac function that is in part independent of altered autonomic control or adaptations in trained skeletal muscle.
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To develop guidelines for exercise testing soon after uncomplicated myocardial infarction, 93 men completed a heart-rate-limited (HRL) protocol and 107 completed a symptom-limited (SXL) protocol 3 weeks after the acute event. In the HRL protocol, effort terminated at a heart rate of 130 beats/min in the absence of a limiting symptom, exertional hypotension or ventricular tachycardia. Peak heart rate was not an end point in the SXL protocol. Despite a higher peak heart rate and work load in patients who completed the SXL protocol, the prevalence of exercise-induced ischemic ST-segment depression and ventricular ectopic activity was similar in the two groups. No complications occurred with either protocol. Twelve patients (6%) had cardiac events within the next 2 months. Regardless of the test protocol used, early events were more common in patients with ischemic ST-segment responses (15%) than in patients without ischemic responses (3%) (p less than 0.01). In contrast, exercise-induced ventricular arrhythmias were not predictive of early events. Eleven weeks after infarction, when all tests were SXL, the prevalence of exercise-induced ischemic ST-segment depression and premature ventricular complexes was similar to that at 3 weeks. We conclude that SXL and HRL exercise test protocols reveal a similar prevalence of ischemic ST-segment depression and ventricular ectopic activity soon after uncomplicated myocardial infarction.
The relationship between high-density lipoprotein (HDL) cholesterol and educational level was examined in 2182 white females and 2368 white males ages 20-59 years in nine North American populations surveyed by the Lipid Research Clinics Program. Mean HDL cholesterol values were positively associated with reported educational achievement. Among females of all ages and males ages 20-39 years, a gradient of HDL cholesterol levels from lowest to highest educational stratum was found. A similar trend of lower magnitude was noted among older males. The positive association between educational and HDL cholesterol levels was statistically significant in both sexes (p < 0.002) and was consistent for each of the study populations. Differences in mean HDL cholesterol between educational strata were in part explained statistically by education-related differences in body mass, alcohol consumption, cigarette smoking, age and, in women, gonadal hormone use. These findings indicate that socioeconomic status and lifestyle, as measured by level of educational achievement, are associated with HDL cholesterol concentrations in adult populations.
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Thirty men, mean age 55 years, known to have treadmill-induced ischemic ST-segment depression, performed static and dynamic effort, i.e., forearm lifting and treadmill exercise, separately and combined. Static effort was sustained at 20%, 25% or 30% of maximal forearm lifting capacity. Two symptom-limited treadmill tests, one with and one without added static effort, were performed on each of two visits. Compared with dynamic effort alone, combined static-dynamic effort decreased treadmill work load and increased heart rate, systolic blood pressure and rate-pressure product at the onset of ischemic ST-segment depression or angina pectoris: 7.1 +/- 0.4 vs 8.0 +/- 0.5 (SEM) multiples of resting oxygen consumption (mets), estimated; 141 +/- 3 vs 134 +/- 3 beats/min; 170 +/- 4 vs. 162 +/- 4 mm Hg and 239 +/- 8 vs 218 +/- 9 (p less than 0.001). The prevalence of angina pectoris was significantly less with combined static-dynamic effort than with dynamic effort alone. Static effort causes a resetting of the threshold at which ischemic abnormalities appear during dynamic effort.
Static and dynamic work involving the arms and the legs was performed by 40 men seven weeks after myocardial infarction. Leg ergometry produced a significantly higher peak work load, systolic blood pressure (BPs), heart rate (HR), and HR X BPs X 10(-2) product (DP) than did arm ergometry: 842 +/- 178 vs 546 +/- 135 kg-m/min, 176 +/- 24 vs 154 +/- 19 mm Hg and 256 +/- 54 vs 219 +/- 48 (SD). Peak heart rates were 145 and 142. Endpoints were primarily muscular and generalized fatigue and dyspnea. Ischemic abnormalities and ventricular ectopy were more frequent with leg ergometry. Sustained forearm lifting elicited higher HR, PBs and DP responses than sustained handgrip contraction: 95 +/- 16 vs 91 +/- 16 beats/min, 162 +/- 18 vs 152 +/- 17 mm Hg and 154 +/- 33 vs 139 +/- 33 (SD). Ischemic ST segment depression and significant ventricuar arrhythmias were infrequent with static effort. Dynamic leg testing is superior to dynamic or static arm testing in assessing the capacity of patients to perform physical work tasks after myocardial infarction.
Seventy-six thallium-201 myocardial perfusion studies were performed on twenty-five patients to assess their reproducibility and the effect ofvarying the level of exercise on the results of imaging. Each patient had a thallium-201 study at rest. Fourteen patients had studies on two occasions at maximum exercise, and twelve patients had studies both at light and at maximum exercise. Of 70 segments in the 14 patients assessed on each of two maximum exercise tests, 64 (91%) were reproducible. Only 53% (16/30) of the ischemic defects present at maximum exercise were seen in the light exercise study in the 12 patients assessed at two levels of exercise. Correlation of perfusion defects with arteriographically proven significant coronary stenosis was good for the left anterior descending and right coronary arteries, but not as good for circumflex artery disease. Thallium-201 myocardial imaging at maximum exercise is reproducible within acceptable limits, but careful attention to exercise technique is essential for valid comparative studies.
Stimulated by increasing evidence of an inverse relationship between plasma high-density lipoprotein cholesterol level and frequency of coronary heart disease, we determined concentrations of fasting plasma cholesterol, triglyceride, and lipoproteins in 41 very active men (running greater than 15 miles/wk for the previous year) 35-59 years of age (mean age, 47) and in a comparison group of men of similar age, randomly selected from three northern California communities. The runners had significantly (p less than 0.05) decreased mean plasma triglyceride (70 versus 146 mg/100 ml), total plasma cholesterol (200 versus 210 mg/100 ml), and low-density lipoprotein (LDL) cholesterol (125 versus 139 mg/100 ml) concentrations, and a higher mean level of high-density lipoprotein (HDL) cholesterol (64 versus 43 mg/100 ml) than the comparison group (n equals 147 for HDL and LDL; n equals 743 for total cholesterol and triglycerides). These very active men exhibited a plasma lipoprotein profile resembling that of younger women rather tan of sedentary, middle-aged men. This characteristic, and apparently advantageous, pattern could be only partially accounted for by differences in adiposity between runners and control subjects.
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