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Biomedical subjects

K B Pandolf

Publications and source records attributed to K B Pandolf.

At least 91 records · Page 5Linked to original sources
PubMed1984

Effect of atropine on the exercise-heat performance of man.

This paper summarizes the findings from two recent studies involving the physiological effects of atropine (0 to 4 mg, im) on soldiers performing physical exercise in hot-dry environments. Study I determined the threshold of physiological effects and the gradation of these effects with increasing dosage of atropine. Study II examined the effects of exercise-heat acclimation on the reduced physical exercise performance that occurs following atropine administration. The following new observations were made: (1) a 0.5-mg dose of atropine elevates heart rate, rectal temperature, and mean skin temperature; (2) atropine exerts its peak physiological effects approximately 70 min after intramuscular injection; (3) within the dosage levels tested, the magnitude of the elevated heart rate response is curvilinearly related to atropine dosage, whereas, the magnitude of the elevated rectal temperature response is linearly related to atropine dosage; (4) repeated administration of atropine over a number of days does not alter thermo-regulatory responses; (5) heat acclimation improves exercise-heat performance of individuals under the influence of atropine by enabling a reduced rectal temperature; and (6) heat acclimation increases the sweat output of individuals under the influence of atropine; however, the absolute reduction in sweat output from atropine is the same pre-and post-heat acclimation.

Acclimatization↗
PubMed1984

Effects of sleep deprivation on thermoregulation during exercise.

Five fit men completed a practice, control, and sleep deprivation exercise test. Two nights of normal sleep preceded the control test, and 33 h of wakefulness preceded the sleep deprivation test. These tests consisted of 20 min of rest followed by 40 min of cycle-ergometer exercise (50% of peak O2 uptake, VO2) in a temperate (ambient temperature, 28 degrees C; relative humidity, 30%)-environment. Esophageal temperature (Tes), local sweat rate (mds), and chest thermal conductance (kch) were continuously measured. During exercise a 0.7 and 0.5 degrees C rise in Tes was found for the sleep deprivation and control tests, respectively. This increase in Tes values from rest to the end of exercise was greater (P = 0.08) for the sleep deprivation than control test. Total body sweat rate, calculated from Potter balance measurements, was 27% less (P less than 0.01) for the sleep deprivation than the control test. Both mds and kch values were lower (P less than 0.05) during the final 20 min of exercise for the sleep deprivation than control test. Final exercise mds values were 19% lower (P less than 0.05) for the sleep deprivation than control test. An asynchronous rather than a normal synchronous mds pattern was frequently observed during the sleep deprivation test. During the sleep deprivation test, the mds sensitivity (delta mds X delta Tes-1) was 38% lower (P less than 0.01) and kch sensitivity (delta kch X delta Tes-1) was 42% lower (P less than 0.05) than during the control test. These data indicate that sleep deprivation decreases evaporative and dry heat loss during moderate-intensity exercise.

Adolescent↗
PubMed1984

Hydration and vascular fluid shifts during exercise in the heat.

This study examined the effects of hypohydration on plasma volume and red cell volume during rest in a comfortable (20 degrees C, 40% relative humidity) and exercise in a hot-dry (49 degrees C, 20% relative humidity) environment. A group of six male and six female volunteers [matched for maximal O2 uptake (VO2 max)] completed two test sessions following a 10-day heat acclimation program. One test session was completed when subjects were euhydrated and the other when subjects were hypohydrated (-5% from base-line body wt). The test sessions consisted of rest for 30 min in a 20 degrees C antechamber, followed by two 25-min bouts of treadmill walking (approximately 30% of VO2 max) in the heat, interspersed by 10 min of rest. No significant differences were found between the genders for the examined variables. At rest, hypohydration elicited a 5% decrease in plasma volume with less than 1% change in red cell volume. During exercise, plasma volume increased by 4% when subjects were euhydrated and decreased by 4% when subjects were hypohydrated. These percent changes in plasma volume values were significantly (P less than 0.01) different between the euhydration and hypohydration tests. Although red cell volume remained fairly constant during the euhydration test, these values were significantly (P less than 0.01) lower when hypohydrated during exercise. We conclude that hydration level alters vascular fluid shifts during exercise in a hot environment; hemodilution occurs when euhydrated and hemoconcentration when hypohydrated during light intensity exercise for this group of fit men and women.

Adult↗
PubMed1984

Thermal responses during arm and leg and combined arm-leg exercise in water.

Thermal and metabolic responses were examined during exposures in stirred water at approximately 20, 26, and 33 degrees C while subjects were performing 45 min of either arm (A), leg (L), or combined arm-leg (AL) exercise. Eight males immersed to the neck completed a low exercise intensity for A exercise and both a low and high exercise intensity for L and AL exercise. During low-intensity exercise, final metabolic rate (M) for A, L, and AL exercise was not different (P greater than 0.05) between exercise type for each water temperature (Tw). In contrast final rectal temperatures (Tre) for A and AL exercise were significantly lower than L values for each Tw during low-intensity exercise. These findings were supported by both mean weighted skin temperature (Tsk) and mean weighted heat flow (Hc) values, which were greater during A than L for each Tw. During high-intensity exercise, final Tre values were lower (P less than 0.05) during AL compared with L exercise across all Tw. Final Tsk and Hc values were not different between each type of exercise, although M was significantly lower during L exercise in 20 degrees C water. These data suggest a greater conductive and convective heat loss during exercise utilizing the arms when compared with leg-only exercise.

Adult↗
PubMed1984

Heat exchange during upper- and lower-body exercise.

This study examined evaporative and dry heat exchange during upper- and lower-body exercise. Four male subjects performed arm-crank or cycle exercise at the same O2 uptake level (approximately 1.6 l/min) in an environment facilitating dry heat exchange [radiative and convective (R + C)] [ambient temperature (Ta) = 18 degrees C, dew-point temperature (Tdp) = 14 degrees C] and an environment facilitating evaporative heat loss (Esk) (Ta = 35 degrees C, Tdp = 14 degrees C). (R + C) was determined from the torso with a net radiometer and from the limbs with heat flow discs, whereas Esk was determined from the torso and limbs by ventilated dew-point sensors. In both environments neither esophageal temperature nor mean skin temperature were different between exercise types (P greater than 0.05). Torso (R + C) was significantly (P less than 0.05) greater during arm-crank than during cycle exercise in both environments. Torso Esk, as well as arm (R + C), and arm Esk were not different (P greater than 0.05) between exercise types in each environment. Leg (R + C) was greater (P less than 0.05) during cycle than during arm-crank exercise in the 18 degrees C environment, whereas leg Esk was greater (P less than 0.05) during cycle than during arm-crank exercise in the 35 degrees C environment. These data indicate that to compensate for greater torso sensible heat loss during upper body exercise lower body exercise elicits additional (R + C) or Esk from the legs. The avenue for this compensatory sensible and insensible heat loss depends upon the differential heat transfer coefficients which influence tissue conductivity and mass transfer.

Adult↗
PubMed1984

Aerobic fitness and the hypohydration response to exercise-heat stress.

This study examined the influence that aerobic fitness (VO2 max) had on final heart rate (HR), final rectal temperature (Tre), and total body sweat rate (Msw) when subjects exercised while euhydrated and hypohydrated (-5.0% from baseline body weight). Eight male and six female subjects completed four exercise tests both before and after a 10-d heat acclimation program. The tests were a euhydration and a hypohydration exposure conducted in a comfortable (20 degrees C, 40% rh) and in a hot-dry (49 degrees C, 20% rh) environment. Significant differences were not generally found between the genders for HR, Tre and Msw during the tests. In the comfortable environment, HR, Tre and Msw were not generally significantly correlated (p greater than 0.05) with VO2max. In the hot-dry environment, Tre and VO2max were significantly correlated (r = -0.58) when euhydrated before acclimation. HR was significantly related to VO2max before acclimation when eu- (r = -0.61) and hypohydrated (r = -0.60) as well as after acclimation when eu- (r = -0.57) and hypohydrated (r = -0.67). These data indicate that, when euhydrated in the heat, aerobic fitness provides cardiovascular and thermoregulatory benefits before acclimation, but only cardiovascular benefits after acclimation. However, when hypohydrated in the heat, cardiovascular benefits are present for fit subjects both before and after acclimation, but thermoregulatory benefits are not associated with fitness.

Acclimatization↗
PubMed1984

Effects of heat acclimation on atropine-impaired thermoregulation.

The effects of saline or atropine injection (2 mg, im) on eccrine sweating and performance time in seven healthy male subjects were evaluated during treadmill walking (1.34 m X s-1) in a hot-dry environment (Ta = 49 degrees C, Tdp = 20.5 degrees C) before and after heat acclimation (HA). Mean skin temperature (Tsk), rectal temperature (Tre), and heart rate (HR) were continuously measured. Sweat loss from the skin (Msw) was calculated by changes in body weight. HA resulted in decreased (p less than 0.05) Tre (0.4 degrees C) and HR (17 b X min-1), and increased (p less than 0.05) Msw (16 g X m-2 X h-1) during the saline experiments. Pre-acclimation, Msw was reduced (p less than 0.01) 65% (151 g X m-2 X h-1) with atropine, which resulted in higher (p less than 0.01) Tre (0.4 degrees C) and Tsk (2.8 degrees C). HR was increased 48% (53 b X min-1) by atropine pre-acclimation (p less than 0.01). Post-acclimation, atropine reduced (p less than 0.01) Msw 33% (100 g X m-2 X h-1) and increased (p less than 0.01) HR 63% (62 b X min-1) compared to saline exposures. The change in Tre X min-1 (delta Tre/delta t) was lower (p less than 0.05) in atropine-injected subjects following heat acclimation, and their worktime was improved by an average of 23.5 min (p = 0.08). These data demonstrate that heat acclimation improves the endurance time of atropine-treated subjects in a hot-dry environment. This improvement was, in part, due to the potentiation of sweat gland activity enabling greater evaporative cooling for the same dose of atropine.

Acclimatization↗
PubMed1984

Hypohydration and acclimation: effects on hormone responses to exercise/heat stress.

This study was designed to assess the effects of hypohydration (-5% body weight) and heat acclimation on plasma cortisol (PC) and growth hormone (GH) responses to exercise (1.34 m X s-1) in a hot-wet (35 degrees C, 79% rh) or hot-dry (49 degrees C, 20% rh) environment. Preacclimation, hypohydration in both the hot-wet and hot-dry environments resulted in significant (p less than 0.05) increments in PC levels during the fourth exercise interval. Acclimation had no effects on PC levels in the euhydrated condition, but in the hot-wet environment there did occur an attenuation of the PC response when hypohydrated. Preacclimation exercise in either the hot-wet or hot-dry environment resulted in significant (p less than 0.05) increments in GH when euhydrated. While the effects of acclimation were inconsistent, hypohydration generally resulted in elevated levels of GH compared to euhydration. We concluded from these studies that hypohydration to -5% of body weight generally elicited elevations in circulating levels of stress hormones, and that acclimation did not effect consistent decrements in these responses.

Acclimatization↗
PubMed1983

Cardio-respiratory physical training in water and on land.

Fifteen unconditioned young men, who were similar in maximal aerobic power (VO2 max), were divided into three groups (n = 5 each) and physically trained for one month on a cycle ergometer either on land (I) or immersed to the neck in water of either 32 degrees C (II) or 20 degrees C (III) to determine if physical training (PT) in water and air differ. PT consisted of one-hour daily exercise, 5 times/wk, with exercise intensity readjusted each week to maintain a constant training stimulus of approximately 75% VO2 max (determined on land). Throughout the training period, heart rates (fc) of III averaged 20 and 10 beats . min-1 less than I and II, respectively, despite working at the same VO2 and % VO2 max. Training elicited a 16% increase in VO2 max in I compared to increases of 13 and 15% for II and III, respectively. It was concluded that PT in water produces similar physiological adaptations as does training on land. In cold water, VO2 max is improved despite training with fc significantly lower than that on land.

Adult↗
PubMed1983

Determination of maximal aerobic power during upper-body exercise.

The purpose of this investigation was to evaluate four protocols for their effectiveness in eliciting maximal aerobic power (peak VO2) during arm-crank exercise. Comparisons were made 1) between a continuous (CON) and an intermittent (INT) protocol (both employed a crank rate of 50 rpm) and 2) among the CON protocols employing crank rates of 30, 50, or 70 rpm. For the first group of experiments no significant (P greater than 0.05) differences were found between the CON and INT protocols for peak VO2, maximal pulmonary ventilation (VEmax), maximal heart rate (HRmax), or maximal blood lactate (LAmax) responses. For the second group of experiments, the CON-50 was compared with the CON-30 and CON-70 protocols. In comparison to the CON-50, significantly higher peak VO2 (+10%) and VEmax (+14%) responses were elicited by the CON-70 protocol, whereas significantly lower peak VO2 (-11%), VEmax (-23%), HRmax (-8%), and LAmax (-29%) responses were elicited by the CON-30 protocol. Of the arm-crank protocols examined the combination of a continuous design and a crank rate of 70 rpm provided the most effective protocol to elicit peak VO2 values.

Adult↗
PubMed1983

Cardiorespiratory responses to exercise distributed between the upper and lower body.

The present study examined the influence that distributing exercise between upper (arm crank exercise) and lower (cycle exercise) body muscle groups had on cardiorespiratory responses to constant power output (PO) exercise. Six male volunteers completed five submaximal exercise bouts of 7-min duration at both 76 and 109 W. The arm PO/total PO (% arm) for these bouts was approximately 0, 20, 40, 60, and 100%. At 76 W, O2 uptake (VO2) did not change (P greater than 0.05) from 0 to approximately 20% arm (approximately 1.30 1 x min-1) but increased with increasing percent arm values up to 100% (1.58 1 x min-1). At 109 W, VO2 increased throughout the range of 0 (1.70 1 x min-1) to 100% arm (2.33 1 x min-1). In general, minute ventilation (VE) and respiratory exchange ratio (R) increased with increased percent arm values at 76 and 109 W. The heart rate (HR) responses remained unchanged from 0 to 60% arm at both 76 and 109 W; however, between 60 and 100% arm, a 26-beats x min-1 increase was observed at 76 W (143 beats x min-1 at 100% arm) and a 45-beats x min-1 increase at 109 W (174 beats x min-1 at 100% arm). These data suggested that during upper body exercise, the increased VO2 associated with increased percent arm values was not accompanied by an elevated HR response when at least 40% of the PO was performed by the lower body. This might be attributed to a facilitated venous return and/or a decreased total peripheral resistance when the lower body was involved in the exercise.

Adult↗
PubMed1983

Hypohydration and exercise: effects of heat acclimation, gender, and environment.

This study examined the effects of heat acclimation and subject gender on treadmill exercise in comfortable (20 degrees C, 40% rh), hot-dry (49 degrees C, 20% rh), and hot-wet (35 degrees C, 79% rh) environments while subjects were hypo- or euhydrated. Six male and six female subjects, matched for maximal aerobic power and percent body fat, completed two exercise tests in each environment both before and after a 10-day heat acclimation program. One exercise test was completed during euhydration and one during hypohydration (-5.0% from baseline body weight). In general, no significant (P greater than 0.05) differences were noted between men and women at the completion of exercise for rectal temperature (Tre), mean skin temperature (Tsk), or heat rate (HR) during any of the experimental conditions. Hypohydration generally increased Tre and HR values and decreased sweat rate values while not altering Tsk values. In the hypohydration experiments, heat acclimation significantly reduced Tre (0.19 degrees C) and HR (13 beats X min-1) values in the comfortable environment, but only HR values were reduced in hot-dry (21 beats X min-1) and hot-wet (21 beats X min-1) environments. The present findings indicated that men and women respond in a physiologically similar manner to hypohydration during exercise. They also indicated that for hypohydrated subjects heat acclimation decreased thermoregulatory and cardiovascular strain in a comfortable environment, but only cardiovascular strain decreased in hot environments.

Acclimatization↗
PubMed1983

Hypohydration and heat acclimation: plasma renin and aldosterone during exercise.

This study was designed to assess the effects of hydration, acclimation, environment, and exercise on plasma levels of renin and aldosterone. Sixteen subjects exercised (1.34 m X s-1), both pre- and postacclimation, when euhydrated or hypohydrated (-5% of body wt) in a comfortable (20 degrees C, rh = 40%), hot-wet (35 degrees C, rh = 79%), or hot-dry (49 degrees C, rh = 20%) environment. Although light exercise in a thermoneutral environment had no effects on plasma levels of renin activity (PRA) or aldosterone (ALD), exercise in both hot environments resulted in significantly increased levels of both. Increments in both PRA and ALD were greater when hypohydrated, and PRA effects were significantly moderated by heat acclimation in both the euhydration and hypohydration experiments. Although PRA and ALD responses were generally correlated, acclimation did not consistently attenuate ALD increments. We concluded that hydration state, acclimation level, and environmental conditions all affected the responses of PRA and ALD to light exercise.

Acclimatization↗
PubMed1983

Effect of endurance training on perceived exertion and stress hormones in women.

Fifteen women (20- to 23-yr.-old), engaged in an intensive 6- to 8-wk. endurance running program, progressively increased distance from 20 miles during the first week to 50 miles during the fifth week and thereafter. Before (T1), during (T2), and after training (T3), submaximal treadmill runs of 1-hr. duration subdivided into three successive 20-min. segments were completed at approximately 60, 70, and 80% of maximal oxygen uptake, respectively. Ratings of perceived exertion (RPE) were differentiated to obtain local (L), central (C), and over-all (O) responses during these 20-min. segments. Subjects rated the effort during the final 30 sec. of each 5-min. interval. Upon completion of each exercise segment, blood samples were drawn for analysis of lactate (Hla), epinephrine (E), and norepinephrine (NE) to determine the relationship between the differentiated RPEs and these stress markers. Endurance training significantly lowered central and over-all ratings of perceived exertion between T1 and T3 runs but no change occurred in the L-RPE responses to muscular and joint strain. Significant correlations between the stress markers and RPE pooled across sessions were observed during the three treadmill sessions (Hla vs L-RPE, eta = 0.68; E vs C-RPE, eta = 0.54; and NE vs C-RPE, eta = 0.63). These findings indicate that central and over-all ratings of perceived exertion may be more readily influenced by intensive endurance training than local ratings. In addition, while lactate levels may be related to local ratings of perceived exertion, catecholamine levels appear to be associated with central ratings.

Adult↗
PubMed1983

Does heat acclimation lower the rate of metabolism elicited by muscular exercise?

Heat acclimation has been suggested to either lower or have no effect on the rate of metabolism (M) elicited by muscular exercise. The purpose of the present investigation (Study I) was to examine the effect heat acclimation has on the M (W . kg-1 or VO2 in ml . kg-1 . min-1) elicited by muscular exercise. Two additional investigations were evaluated to determine if season (summer or winter) of year (Study II) and subject gender (Study III) further influence the effect heat acclimation has on M during exercise. Volunteers for Study I (n = 15 men), II (n = 8 men), and III (n = 10 men and 9 women) completed standardized treadmill walks in hot (40 degrees C, 30% rh or 49 degrees C, 20% rh) and cool (20 degrees C, 40% rh) environments immediately before and after heat acclimation. After heat acclimation, a lower M was observed for Study I (-4%; p less than 0.05), II (-2%; N.S.) and III (-3%; p = 0.06) in the hot environments. In addition, after heat acclimation a lower M was observed for Study I (-3%; p = 0.08), II (-5%; p less than 0.05) and III (-6%; p less than 0.05) in the cool environment. Season of year and subject gender did not have a significant effect on these results. These data indicate that heat acclimation does lower the M elicited by exercise. The observed percent decrease was lower in the hot (-3%) than cool (-5%) test environments.

Acclimatization↗