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Biomedical subjects

K B Pandolf

Publications and source records attributed to K B Pandolf.

At least 109 records · Page 6Linked to original sources
PubMed1982

Effects of training with eccentric muscle contractions on exercise performance, energy expenditure, and body temperature.

To study the effects of exercise training with eccentric muscle contractions on body temperatures, energy cost, and performance capacity, six human subjects were tested before and after a 5-week training program of eccentric exercise. Exercise was performed as leg cycling on a motor-driven ergometer at power levels ranging 252-316 W. Training consisted of three sessions/week for 1 h/session. As a result of the training, VO2, fH, and mean skin temperature were lowered for each subject at the same absolute exercise intensities. Ability to continue exercise as indicated by endurance time improved with training. Before training, four subjects terminated exercise after 30 min because of localized leg exhaustion and one subject could not continue longer than 45 min. After training, all six subjects completed 45 min of the exercise test without difficulty. Esophageal and muscle temperatures evidenced no changes as a result of training. It was concluded that the inability of subjects to perform eccentric exercise in the untrained state was not related to muscle temperature.

Adult↗
PubMed1982

Sparing effect of chronic high-altitude exposure on muscle glycogen utilization.

Substrate utilization during heavy [approximately 85% maximum O2 consumption (VO2max)] bicycle exercise was examined in eight low-altitude residents at sea level (SL) and after acute (2 h) and chronic (18 days) high-altitude (HA) exposure at 4,300 m. Mean VO2max was approximately 27% lower at acute HA than at SL and did not change significantly with continued HA exposure. Biopsies from the vastus lateralis muscle and venous blood samples were obtained before and after 30 min of exercise, whereas determinations of the respiratory exchange ratio (R) were made at 10-min intervals during each of the submaximal bouts. Resting levels of serum-free fatty acids at acute and chronic HA were, respectively, two and three times higher than SL but were unchanged with exercise. Exercise did not alter resting serum glycerol levels at SL or during acute HA, but during chronic HA resting glycerol levels were increased 11-fold. Although mean blood lactate concentrations following exercise at SL and acute HA were not significantly different, postexercise lactate concentrations were 87% lower after chronic HA. During exercise at SL and acute HA, muscle glycogen utilization and R were not different. At chronic HA, muscle glycogen utilization and R were 41 and 15% lower, respectively. These data suggest that after chronic HA exposure, increased mobilization and use of free fatty acids during exercise resulted in sparing of muscle glycogen.

Adaptation, Physiological↗
PubMed1982

Effects on heat tolerance of physical training in water and on land.

A 4-wk training program was undertaken by 15 untrained non-heat-acclimated males who were divided into three groups matched on maximal aerobic capacity (VO2max) and trained either in water or on land to determine how physical training (PT) in these different media affects heat tolerance. Subjects trained on a cycle ergometer for 1 h/day, 5 days/wk at 75% VO2max, with the exercise intensity progressively increased to maintain a constant training stimulus. Group I exercised on land, whereas groups II and III exercised while immersed to the neck in water of either 32 degrees C (II) or 20 degrees C (III). Daily exercise increased core temperature (Tc) in groups I and II but not in group III. Training elicited similar increases (approximately 15%) in VO2max in the three groups. Before and after PT, all subjects exercised at approximately 30% VO2max for 3 h at 49 degrees C, 20% rh. Compared with before training, groups I and II showed a decrease in final Tc and heart rate (HR) in the posttraining heat exposure. Sweat rate increased 25% in group II but remained the same in group I. Group III demonstrated a decrease in final HR, but final Tc was higher than before training. Sweat rate did not increase in group III and was lower than the other groups. It was concluded that PT can improve the cardiovascular response to dry heat without affecting thermoregulatory capacity. PT appears to enhance heat tolerance only if Tc is permitted to rise during exercise, thus stimulating the temperature-regulating center for heat dissipation.

Adaptation, Physiological↗
PubMed1982

Cardiovascular and perceptual responses to isometric exercise.

The purpose of this study was to investigate the effects of 3 intensities of isometric handgrip contractions on selected cardiovascular parameters and perception of effort, and to determine the relationship of these cardiovascular parameters to perception of effort. Seven healthy subjects were instructed to maintain 3-minute contractions in a randomized sequence, at 15, 25, and 35% of their maximal voluntary contractions (% MVC) while heart rate, systolic blood pressure, diastolic blood pressure and perception of effort were measured at 1-minute intervals. All 4 parameters were found to significantly increase (p less than 0.05) both as a function of contraction intensity (% MVC) and time. Correlation coefficients relating perception of effort to systolic blood pressure, diastolic blood pressure, and heart rate were 0.76, 0.64, and 0.63, respectively, suggested that perception of effort was a better predictor of systolic blood pressure than of diastolic blood pressure or heart rate. A 3-step multiple regression resulted in a cumulative r value of 0.82. Recommendations were made that perception of effort be further explored for clinical use during exercise prescription as an indicator of cardiovascular stress. By using a technique of perception of effort, patients could be taught to restrict activity to within a safe range of cardiovascular variability, rather than totally refrain from all forms of isometric activity.

Adult↗
PubMed1982

Differentiated ratings of perceived exertion are influenced by high altitude exposure.

Differentiated ratings of perceived exertion (RPE) were obtained from eight low-altitude residents during cycle exercise at sea level (SL) and after acute (less than 2 h) and chronic (18 d) exposure to high altitude (4,300 m; HA). Mean VO2max was 27% lower with acute HA exposure. Subjects cycled for 30 min at an exercise intensity requiring 85% of VO2max. Respiratory exchange measurements and differentiated RPE were obtained at minutes 5, 15 and 25 of exercise, and pre- and post-exercise blood samples were collected. Differentiated RPE included a local muscular rating, a central or cardiopulmonary ratings, and an overall rating. Despite reduced absolute exercise intensity during acute HA exercise, local RPE were unchanged from SL values. Chronic HA exercise, however, was associated with a significant reduction in local RPE. Blood lactate accumulation during SL exercise was not significantly greater than central ratings, while neither differed significantly from the overall ratings. None of the differentiated ratings differed significantly during acute and chronic HA exercise; central RPE were highest of the ratings during chronic HA exercise. The ventilatory equivalent for oxygen during HA exercise (both acute and chronic) was significantly higher than at SL. This apparent rearrangement in the relative order of magnitude of these three differentiated ratings suggests an alteration in the relationship between perceptual cues sensed as effort.

Adult↗
PubMed1982

Differentiated ratings of perceived exertion during physical exercise.

The typical overall (undifferentiated) rating of perceived exertion (RPE) appears to represent an individual's integration of various physiological sensations that have different subjective weightings. Two categories of physiological factors have been suggested as major determinants of RPE during physical exercise. These two factors are a local factor that relates to sensations or feelings of strain from the exercising muscles and/or joints and a central factor relating primarily to cardiopulmonary sensations. This paper attempts to characterize the relative importance of the various physiological cues in the exertional rating pertinent to these local and central factors. The majority of the related literature suggests that local factors are usually perceived as dominant; however, recent findings that evaluate differentiated RPE during exercise at high altitude imply a greater importance for central factors. When a particular physiological cue is markedly altered over others during exercise, it appears that the resultant sensation can easily dominate the overall RPE. In contrast, when this particular cue is not changed during exercise, as the result of some experimental manipulation or intervention, then another cue can become pronounced. Finally, an experimental model for evaluating differentiated RPE that allows comparisons between local and central exertion and further comparison to the general or overall exertion is discussed.

Altitude↗
PubMed1982

Auxiliary cooling: comparison of air-cooled vs. water-cooled vests in hot-dry and hot-wet environments.

Water-cooled, air-cooled, and ambient air-ventilated auxiliary cooling vests were evaluated in a hot-wet climate (HW) (35 degrees C, 75% R.H.) and a hot-dry environment (HD) with additional infrared radiation (Ta = 49 degrees C, 20% R.H., 68 degrees C black globe temperature). Twelve subjects dressed in full chemical warfare combat uniforms underwent 120 min of heat exposure in each combination of climate and cooling vest, except for the hot-dry environment and ambient-air vest. During each exposure, total exercise time was 20 min and rest time 100 min. This resulted in a mean time weighted metabolic rate of 180 W. Both water-cooled and air-cooled vests were sufficient for cooling in the HW climate: heat storage (delta S) was 13 and 7 W, final rectal temperature (Tre) 37.4 and 37.3 degrees C, and heart rate (HR) 124 and 112 b . min-1, respectively. While using the ambient-air vest, all variables were significantly (p less than 0.05) higher (delta S, 25 W; Tre, 37.7 degrees C; HR, 139 b . min-1; respectively). In the HD climate, both water and air-cooled vests were insufficient with a delta S of 46 and 48 W, final Tre of 38.4 and 38.3 degrees C, and final HR of 151 and 147 b . min-1. However, both cooling vests improved the subjects' physiological status compared to these predicted variables without auxiliary cooling. No significant differences were found between the air or the water-cooled vests in either the HD or HW climates. It was concluded that an air-cooled vest can be used with the same efficiency as a water-cooled vest. In contrast, the ambient-air vest was shown to have a low effectiveness in HW and to be dangerous in a HD climate.

Body Temperature Regulation↗
PubMed1981

Modification of the Monark bicycle ergometer for underwater exercise.

A standard Monark bicycle ergometer was modified for underwater exercise by removal of the friction belt and attachment of one to six metal fins to the flywheel. Three fins could be fastened to either side of the flywheel. The fins used on the left side of the wheel were made of standard perforated angle iron with the perpendicular side measuring 38 mm; those on the right side were made from the same length of nonperforated angle iron but with a perpendicular side of only 26 mm. Net surface area of the two types of fins (excluding area of perforation) was the same. Oxygen uptake (VO2) was found to be: VO2 = a(rpm)b + 0.25, 1.min-1, with a = 0.00164 -- 0.00104n + 0.000266n2 -- 0.00002n3; b = 1.64 + 0.506n -- 0.104n2 + 0.00667n3, when n is the number of fins. The correlation coefficient (r) between measured and predicted VO2 was r = 0.98. The preferable range of pedaling speeds was 29-40 rpm to maintain a constant speed for up to 1 h. Major advantages of this modified ergometer for underwater exercise are 1) the modification is simple and the same ergometer can be used for land exercise, 2) the ergometer can be biologically calibrated and used for a wide range of exercise oxygen uptakes, and 3) subjects can perform for a proportionally longer time period than other modifications of the same ergometer.

Adult↗
PubMed1981

Physiological and hematologic responses to summer and winter dry-heat acclimation.

Differences between acclimation to heat at the end of winter (W) and at the end of summer (S) were studied on the same eight male volunteers. Subjects were exposed to 40 degrees C, 30% rh for 10 consecutive days on two separate occasions approximately 5 mo apart (S and W). Daily exposures lasted 120 min: 10 min rest, 50 min walking 1.34 m . s-1 on the level, 10 min rest, 50 min walking. During W acclimation, rectal temperature (Tre) and heart rate (HR) decreased, sweat rate (msw) remained unchanged, and plasma and red cell volume of the blood expanded. During S acclimation, HR decreased while Tre and msw remained unchanged, and plasma volume increased. The Tre of the acclimated subjects remained higher in W, and the msw lower, than in S. It was concluded that acclimation does not totally eliminate the seasonal differences in thermoregulatory set point and sweating sensitivity. Further, acclimation to a more severe heat did not lower the thermoregulatory set point that was achieved by natural acclimatization to a milder heat but affected the cardiovascular adjustment and caused greater plasma volume expansion. W acclimation caused both plasma and blood cell volume expansion, whereas S acclimation affected only plasma volume.

Acclimatization↗
PubMed1981

Energy expenditure during load carriage at high altitude.

To determine the applicability of a prediction equation for energy expenditure during load carriage at high altitude that was previously validated at sea level, oxygen uptake (Vo2) was determined in five young men at 4,300 m while they walked with backpack loads of 0, 15, and 30 kg at treadmill grades of 0,8, and 16% at 1.12 m.s-1 for 10 min. Mean +/- SE maximal Vo2, determined on the cycle ergometer, was 42.2 +/- 2.3 at sea level and 35.6 +/- 1.7 ml.kg-1 .min-1 at altitude. There were no significant differences in daily Vo2 at any specific exercise intensity on days 1, 5, and 9 of exposure, nor were there any differences in endurance times at the two most difficult exercise intensities. Endurance times for 15- and 30-kg loads at 16% grade were 7.3 and 4.2 min, respectively. Measured energy expenditure was compared with that predicted by the formula of Pandolf et al. (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 43: 577-581, 1977) and found to be significantly different. The differences could be attributed to measurements at metabolic rates exceeding 730 W or 2.1 1.min-1 Vo2. These data indicate that the prediction equation can be used at altitude for exercise intensities not exceeding this upper limit. The observed deviations from predicted values at the high exercise intensities could possibly be attributed to the occurrence of appreciable oxygen deficits and the inability to achieve steady-state conditions.

Adolescent↗
PubMed1980

Persistence of impaired heat tolerance from artificially induced miliaria rubra.

Ten volunteers were heat acclimatized to 48.9 degrees C (Ta), 20% rh for 7 days to complete a 100-min walk on a level treadmill (1.56 m x s-1). Subjects were then divided into experimental (n = 6) and control (n = 4) groups. Miliaria rubra (heat rash) was then induced on the experimental subjects by wrapping them for 3 days in polyethylene plastic. All six developed marked miliaria with involvement of 40-70% of the total body surface area. All subjects were reexposed to walking in the heat on the 7th day after unwrapping, by which time rash was clinically indetectable, and again 14 days after unwrapping. On the first test (day 7) only one of the rashed group, and on the second test (day 14) only two could complete the 100-min walk; the control group finished without difficulty on both days. Body heat storage for the rash group was 2.5 times that of the control group on day 7 and 1.5 as great on day 14; measurements of mean body temperature (Tb) on the rash group indicated a much greater heat stress when compared to their own prerash-acclimatized values or those of the control group. These data demonstrate the potential of "healed" miliaria in the etiology of clinical heat illness.

Acclimatization↗
PubMed1980

Heat intolerance as a function of percent of body surface involved with miliaria rubra.

Twenty-four heat-acclimatized male volunteers were wrapped as previously described (Am. J. Physiol. 239 (Regulatory Integrative Comp. Physiol. 8): R226-R232, 1980) but to produce miliaria rubra (heat rash) in specific regions of the body. Three experimental rash groups were involved: 1) the torso (17% total skin surface rashed, n = 6), 2) torso and arms (38%, n = 8), or 3) legs (41%, n = 6), while four subjects served as controls. All subjects were reexposed to walking in the heat on the 7th day after unwrapping, and again 14, 21, and 28 days after unwrapping. When compared to responses for the last heat acclimatization day, tolerance time and sweat rate were lower and mean body temperature and delta heat storage significantly higher for experimental rash subjects contrasted to the controls for up to 21 days; however, no significant differences between the three rashed groups were found. The critical amount of surface area for heat intolerance from heat rash appears to be related to the specific region of the body and associated sweating responses; smaller rashed areas of the trunk, because they have greater potential for abundant sweating, may produce similar responses to heat stress as larger rashed areas of the limbs. Heat intolerance due to rash was not resolved until after 21 days.

Acclimatization↗