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Biomedical subjects

D R Seals

Publications and source records attributed to D R Seals.

156 records · Page 9Linked to original sources
PubMed1984

Effect of training on blood lactate levels during submaximal exercise.

Eight men were studied before and after a 12-wk exercise program to determine the effect of training on blood lactate levels during submaximal exercise. The training elicited a 26% increase in maximum O2 uptake (VO2max). Lactate concentrations at the same relative exercise intensities in the 55-75% of VO2max range were significantly lower after training. A significantly higher relative exercise intensity was needed to elicit a given lactate level in the 1.5- to 3.0-mM range after training. O2 uptake at the work rate required to raise blood lactate to 2.5 mM was 39% higher after training. A blood lactate of 2.5 mM was attained at 68 +/- 4% VO2max before and 75 +/- 3% of VO2max after training. Eight competitive runners required an even higher relative work rate (83 +/- 2% of VO2max) to attain a blood lactate of 2.5 mM. These data provide evidence that the adaptations to training that result in an increase in VO2max are, to some degree, independent of those responsible for the lower blood lactate levels during submaximal exercise.

Adult↗
PubMed1984

Glucose tolerance in young and older athletes and sedentary men.

Groups of endurance-trained masters athletes (60 +/- 2 yr), older untrained men (62 +/- 1 yr), lean older untrained men (61 +/- 2 yr), endurance-trained young athletes (26 +/- 1 yr), and young untrained men (28 +/- 1 yr) were studied to obtain information on the separate effects of age, physical activity, and body fatness on glucose tolerance and insulin sensitivity. Each subject underwent an oral 100-g glucose tolerance test. Skinfold thickness was determined at six sites. The trained groups had a higher maximum O2 uptake capacity and lower sum of skinfolds than their sedentary peers. The lean older untrained group had a sum of skinfolds similar to that of the young untrained group. The masters athletes, young athletes, and young untrained men exhibited similar glucose tolerance whereas the two older untrained groups had an almost twofold greater total area under the glucose curve (P less than 0.05). The masters and young athletes had significantly blunted plasma insulin responses compared with the other three groups (P less than 0.05). The young and the lean older untrained groups had similar plasma insulin responses with significantly lower insulin levels than the older untrained group (P less than 0.05). These results provide evidence that regularly performed vigorous exercise can, in some individuals, prevent the deterioration of glucose tolerance and insulin sensitivity with age.

Adult↗
PubMed1984

Endurance training in older men and women. I. Cardiovascular responses to exercise.

The effects of prolonged endurance training on maximal O2 uptake capacity (VO2max) and its determinants were studied in 11 older individuals (63 +/- 2 yr). The subjects were evaluated before training, after 6 mo of low-intensity (LI) training, and after an additional 6 mo of higher intensity (HI) training. VO2max was 25.4 +/- 4.6 ml X kg-1 X min-1 before training, 28.2 +/- 5.2 ml X kg-1 X min-1 after LI training (P less than 0.05), and 32.9 +/- 7.6 ml X kg-1 X min-1 after HI training (P less than 0.01), with an overall increase of 30%. The increase in VO2max in response to training appeared to be mediated primarily through an increase in maximal arteriovenous O2 difference (P less than 0.01), with little augmentation of maximal cardiac output (Q) (P greater than 0.05). At the same absolute work rates, stroke volume was higher (P less than 0.05); heart rate (HR), blood pressure (BP), and systemic vascular resistance were lower (P less than 0.05); and Q and arteriovenous O2 difference were unchanged after training. At the same relative work rates, arteriovenous O2 difference was higher (P less than 0.01); BP and systemic vascular resistance were lower (P less than 0.05); and HR, Q, and stroke volume did not change significantly. These findings show that older individuals can adapt to prolonged endurance training with a large increase in aerobic power.

Aged↗
PubMed1984

Endurance training in older men and women II. Blood lactate response to submaximal exercise.

Seven men and four women (age 63 +/- 2 yr, mean +/- SD, range 61-67 yr) participated in a 12-mo endurance training program to determine the effects of low-intensity (LI) and high-intensity (HI) training on the blood lactate response to submaximal exercise in older individuals. Maximal oxygen uptake (VO2max), blood lactate, O2 uptake (VO2), heart rate (HR), ventilation (VE), and respiratory exchange ratio (R) during three submaximal exercise bouts (65-90% VO2max) were determined before training, after 6 mo of LI training, and after an additional 6 mo of HI training. VO2max (ml X kg-1 X min-1) was increased 12% after LI training (P less than 0.05), while HI training induced a further increase of 18% (P less than 0.01). Lactate, HR, VE, and R were significantly lower (P less than 0.05) at the same absolute work rates after LI training, while HI training induced further but smaller reductions in these parameters (P greater than 0.05). In general, at the same relative work rates (ie., % of VO2max) after training, lactate was lower or unchanged, HR and R were unchanged, and VO2 and VE were higher. These findings indicate that LI training in older individuals results in adaptations in the response to submaximal exercise that are similar to those observed in younger populations and that additional higher intensity training results in further but less-marked changes.

Aged↗
PubMed1984

The effect of left ventricular systolic function on maximal aerobic exercise capacity in asymptomatic patients with coronary artery disease.

The purpose of this study was to examine the relationship between maximal O2 uptake (VO2max) and left ventricular systolic function in patients with coronary artery disease. We studied 27 patients, age 50 +/- 10 years (mean +/- SD), who were asymptomatic and able to attain true VO2max. VO2max was defined by the leveling-off criterion and/or a respiratory exchange ratio of 1.15 or greater. Left ventricular ejection fraction was determined by gated cardiac blood pool imaging. In patients whose ejection fraction decreased with exercise, VO2max was 21 +/- 4 vs 27 +/- 4 ml/kg/min in those whose ejection fraction increased (p less than .001). Systolic blood pressure/end-systolic volume relation was shifted upward and to the right in the former group in response to peak exercise. In contrast, the pressure-volume relation was shifted upward and to the left in patients whose ejection fraction increased with exercise. Ejection fraction at rest did not correlate with VO2max. There was a significant but weak correlation between peak exercise ejection fraction and VO2max (r = .43, p less than .025). Left ventricular exercise reserve, i.e., the change in ejection fraction from rest to exercise, correlated with VO2max (r = .77, p less than .0002), maximal O2 pulse (r = .50, p less than .005), and maximal heart rate during treadmill exercise (r = .61, p less than .001). Maximal heart rate during treadmill exercise correlated with VO2max (r = .70, p less than .0002).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Effects of high-intensity strength training on cardiovascular function.

Thirteen healthy, untrained males (age 44 +/- 1 yr, range 40-55 yr) were studied to determine the effects of 16 wk of high-intensity, variable-resistance, Nautilus strength training on cardiovascular function. A control group consisting of 10 untrained males (age 52 +/- 2 yr, range 40-64 yr) underwent the same evaluation procedures as the training group. Maximal oxygen uptake (VO2max), cardiac output during submaximal exercise, and body composition were determined before and after training. In addition, the physiological responses to an acute training session were evaluated. Muscular strength increased markedly, as evidenced by a 44% average increase in the "one-repetition maximum" in the various exercises. Body weight and percent body fat did not change with training, though fat-free weight did increase (66.9 +/- 2.6 vs 68.8 +/- 2.7 kg, P less than 0.05) significantly. Maximal oxygen uptake did not change significantly in either the training or the control group, and there were no changes in the hemodynamic responses to submaximal exercise after training. These findings indicate, therefore, that high-intensity, variable-resistance strength training produces no adaptative improvement in cardiovascular function. The physiological responses measured during a training session provide evidence that this lack of cardiovascular adaptation may be due to the low percentage of VO2max elicited by this form of exercise.

Adult↗
PubMed1984

The effect of exercise training on human hypertension: a review.

Numerous sources of information in both the medical and exercise physiology areas state that exercise training lowers blood pressure at rest and during submaximal exercise in normotensive and hypertensive individuals. Based on these statements, the medical community is currently recommending regular exercise as a non-pharmacological therapy for reducing blood pressure in hypertensive patients. The purpose of this review was to assess the existing literature in this area to determine whether a basis exists for this recommendation. Our findings indicate that most of the studies reviewed reported modest reductions in blood pressure (means less than or equal to 10 mmHg) at rest and during submaximal exercise after training. However, even the modest reductions in blood pressure reported in these studies must be interpreted with caution because of numerous methodological shortcomings and inadequate study design, most notably the omission of non-exercising hypertensive control groups. Therefore, the evidence available at the present time is inadequate to recommend exercise training as a non-pharmacological therapy in hypertension.

Adolescent↗
PubMed1983

Comparison of peak oxygen uptake in arm cranking.

Twenty male subjects, age (+/- SD) 31.1 +/- 5.6 years and weight 74.3 +/- 12.7 kg participated in this study to compare the VO2 peak values in arm cranking obtained using continuous (C) and discontinuous (D) protocols. Each subject performed a continuous (C) and discontinuous (D) protocol in random order on two separate days. Cranking was performed at 60 rev X min-1 with tests terminated when this fell below 50. Peak values for oxygen uptake ventilation and heart rate were determined during each test. The C protocol involved increasing power output each minute, while in the D protocol 2 min work bouts were separated by 1 min rest intervals. No significant differences (p greater than 0.05) between the C and D protocols were shown on any measured variable. It was concluded that the use of C or D protocols for determining VO2 peak in arm cranking provide comparable results with the C protocol being advantageous in terms of administration time.

Adult↗
PubMed1983

Similarity of cardiovascular response to upper and lower body static contraction in endurance-trained and untrained males.

The purpose of this study was to investigate the cardiovascular response to upper and lower body static contraction in endurance-trained (ET) and untrained (UT) males (both groups N = 6). The groups were similar in age, height, and weight. However, the ET group exhibited a markedly higher (P less than 0.01) VO2 max during treadmill running than the UT group (65.4 +/- 4.8 vs 49.9 +/- 2.8 ml X kg-1 X min-1, mean +/- SD). Both groups performed static handgrip and leg extension in a randomly assigned order at 30% of maximal voluntary contraction for 3 min. Heart rate and mean intra-arterial blood pressure (MABP) were measured at rest and throughout contraction. At rest, differences between the two groups were not significant for heart rate (54 +/- 10 vs 66 +/- 8 beats X min-1) or MABP (93 +/- 4 vs 91 +/- 5 mm Hg). During handgrip, the increases in heart rate (24 +/- 12 vs 15 +/- 6) and MABP (24 +/- 10 vs 27 +/- 12) were not significantly different between the two groups. During leg extension, the magnitude of the increases in heart rate (44 +/- 21 vs 46 +/- 27) and MABP (37 +/- 11 vs 41 +/- 10) were again not different for the two groups. These results suggest that cardiovascular regulation during static contraction is similar in endurance-trained and untrained individuals, even during contraction involving the trained musculature.

Adult↗
PubMed1983

Failure of endurance training to alter the cardiovascular response to static contraction.

The purpose of this study was to determine whether endurance training alters the cardiovascular response to static contractions of the trained, but not untrained, musculature. Six healthy, untrained males (aged 23-36 years) underwent 10-12 weeks of intensive training involving both cycling and running. Peak VO2 on the bicycle ergometer, VO2max during graded treadmill running and concentrations of citrate synthase (CS) and malate dehydrogenase (MDH) in the vastus lateralis muscle were measured before and after training. Subjects performed static leg extension and forearm extension at 30% of maximal voluntary contraction until exhaustion before and after training. Heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressure were measured at rest, and in addition to perceived exertion (PE), every 30 s during contraction. Endurance training elicited significant increases in peak VO2 (36%), VO2max (32%), CS (25%) and MDH (42%) (all P less than 0.05). HR at rest was significantly lower (P less than 0.05) after training, while SBP and DBP were unchanged. HR, SBP, DBP and PE increased throughout both types of static contractions. However, the magnitude of the increases were unaffected by training. In contrast to recent findings, these results suggest that the increases in heart rate and blood pressure in response to static contraction are not altered after endurance training in either the trained or the untrained muscle groups.

Adult↗
PubMed1983

Increased cardiovascular response to static contraction of larger muscle groups.

The purpose of this study was to investigate the influence of the size of the active muscle mass on the cardiovascular response to static contraction. Twelve male subjects performed one-arm handgrip (HG), two-leg extension (LE), and a "dead-lift" maneuver (DL) in a randomly assigned order for 3 min at 30% of maximal voluntary contraction. O2 uptake (VO2), heart rate (HR), and mean intra-arterial blood pressure (MABP) were measured at rest and, in addition to absolute tension exerted, throughout contraction. There was a direct relationship between the size of the active muscle mass and the magnitude of the increases in VO2, HR, and MABP, even though all contractions were performed at the same relative intensity. Tension, VO2, HR, and MABP increased progressively from HG to LE to DL. It was concluded that at the same percentage of maximal voluntary contraction, the magnitude of the cardiovascular response to isometric exercise is directly influenced by the size of the contracting muscle mass.

Adult↗