S. G. DaSilva

Metabolic efficiency during arm and leg exercise at the same relative intensities.

This study was conducted to compare gross efficiency (GE), net efficiency (NE), work efficiency (WE), and delta efficiency (DE) between arm crank and cycle exercise at the same relative intensities. Eight college-aged males underwent two experimental trials presented in a randomized counterbalanced order. During each trial subjects performed three intermittent 7-min exercise bouts separated by 10-min rest intervals on an arm or semirecumbent leg ergometer. The power outputs for the three bouts of arm crank or cycle exercise corresponded to 50, 60, and 70% of the mode-specific VO2peak. GE, NE, and WE were determined as the ratio of Kcal.min-1 equivalent of power output to Kcal.min-1 of total energy expended, energy expended above rest and energy expended above unloaded exercise, respectively. DE was determined as the ratio of the increment of Kcal.min-1 of power output above the previous lower intensity to the increment of kcal.min-1 of total energy expended above the previous lower intensity. GE and NE did not differ between arm crank and cycle exercises. However, WE was lower (P < 0.05) during arm crank than cycle exercise at 50, 60, and 70% VO2peak. DE was also lower (P < 0.05) during arm crank than cycle exercise at delta 50-60 and at delta 60-70% VO2peak. It is concluded metabolic efficiency as determined by work and delta efficiency indices was lower during arm crank compared with cycle exercise at the same relative intensities. These findings add to the understanding of the difference in metabolic efficiency between upper and lower body exercise.

Substrate utilization and glucose turnover during exercise of varying intensities in individuals with NIDDM.

PURPOSE This investigation was undertaken to examine substrate utilization and glucose turnover during exercise of varying intensities in NIDDM patients. METHODS Six male NIDDM patients (N) and six male controls (C) of similar age, body weight, % body fat, and VO2peak were studied in two experimental sessions administered in a randomized counterbalanced order. During each session the subjects cycled at a power output corresponding to 50% of VO2peak or 70% of VO2peak. Duration of exercise was adjusted so that energy expenditure (EE) was equal in both the 50% and 70% trials. Isotope infusion technique and indirect calorimetry were used to assess substrate utilization and glucose turnover during exercise. RESULTS Rates of carbohydrate (CHO) and lipid oxidation increased (P < 0.05) during both the 50% and 70% trials. Rates of CHO oxidation were greater (P < 0.05) during the 70% than during the 50% trial. However, rates of lipid oxidation were similar in the two trials. No differences in rates of CHO and lipid oxidation were observed in N and C. Rates of hepatic glucose production (Ra) and plasma glucose utilization (Rd) increased (P < 0.05) during exercise, and the increases were similar in the 50% and 70% trials. Ra did not differ between N and C. However, Rd was greater (P < 0.05) in N than in C. Plasma glucose concentration decreased (P < 0.05) in N, with the decrease being similar in the 50% and 70% trials. In contrast, plasma glucose concentration remained unchanged during both the 50% and 70% trials in C. CONCLUSIONS Exercise results in a greater increase in plasma glucose utilization in patients with NIDDM compared with that in normal individuals, and this increase mediates the decline in plasma glucose concentrations in patients with NIDDM. Under isocaloric conditions, the changes in plasma glucose utilization and plasma glucose concentrations are similar during exercise of varying intensities. Despite a greater glucose utilization, carbohydrate and fat oxidation are similar in the two groups and their relations to exercise intensity are not altered by NIDDM.

Psychophysiological Responses to Self-Paced Treadmill and Overground Exercise

UNLABELLED Speculation exists that a positive affective response experienced during exercise may play an important role in predicting exercise adherence. Previous studies using self-paced exercise protocols have been associated with health benefits and pleasant experiences. However, all of these studies were conducted in laboratories, and consequently, the external validity of the findings may be questionable. PURPOSE To determine whether environmental settings (treadmill vs overground) differentially influence physiological, perceptual, and affective responses to exercise at a self-selected pace. METHODS Thirty-four individuals (17 men and 17 women) between 18 and 30 yr volunteered to participate in this study. During the orientation session, individuals underwent an initial screening, anthropometric measurements, and familiarization with the experimental procedures. Next, subjects underwent a maximal treadmill test. In the two experimental trials, participants performed 20-min bouts of treadmill and overground walking at a self-selected pace, which were completed in a counterbalanced order. At least 48 h separated experimental trials. RESULTS Using repeated-measures ANOVA, overground walking speed was significantly faster than treadmill walking speed (P < 0.01) during the 20-min bout of self-paced exercise. However, exercise intensity (%VO2R and %HRR) and perceived exertion during the session of overground walking were significantly lower (P < 0.05) when compared with those during the treadmill session. In addition, affective valence was more positive during the session of overground walking than during the treadmill session (P < 0.01). CONCLUSIONS These data extend previous findings by showing that environmental setting influences physiological, perceptual, and affective responses during exercise at a self-selected pace. Self-paced exercise performed over ground resulted in lower perceptual and more positive affective responses.

Effect of Carbohydrate Substrate Availability on Ratings of Perceived Exertion during Prolonged Exercise of Moderate Intensity

This investigation examined the effect of carbohydrate substrate availability on ratings of perceived exertion (RPE) during cycling at moderate intensity to exhaustion and the relation between submaximal endurance performance and RPE obtained following 2 hr. of cycling at moderate intensity. Seven male cyclists performed two exercise trials at power output corresponding to 70% of their peak oxygen uptake until exhaustion. Subjects ingested either a 6% glucose/sucrose solution at the rate of 0.6 g · kg−1 (Body Weight) · hr.−1 or an equal volume of artificially flavored placebo every 20 min. throughout the exercise trials. RPE for the legs, chest, and over-all body, and oxygen consumption, expired ventilation, carbohydrate oxidation rate, and blood concentrations of glucose, glycerol, and lactate were measured every 20 min. throughout exercise and at exercise termination. Statistical analysis of these dependent variables indicates that (1) an exercise-induced decrease in blood-borne carbohydrate substrate intensifies leg and over-all perceptions of exertion during the later stages of prolonged cycling at 70% VO2peak. (2) Factors other than availability of blood-borne carbohydrate substrate may influence perceptual intensity at exhaustion. (3) Ratings of perceived exertion for the legs and over-all body obtained after 2 hr. of cycling at moderate intensity may be useful in predicting submaximal endurance performance.

Endogenous opioids may modulate catecholamine secretion during high intensity exercise

AbstractTo determine the effect of endogenous opioids on catecholamine response during intense exercise [80% maximal oxygen uptake (

The influence of adiposity on physiological, perceptual, and affective responses during walking at a self-selected pace.

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RATINGS OF PERCEIVED EXERTION AND ENERGY EXPENDITURE DURING LIGHT TO MODERATE ACTIVITY

O2max)], nine fit men [mean (SE) (