Dynamics of changes in the cardiovascular response to submaximal exercise during low-intensity endurance training with particular reference to the systolic time intervals

Eighteen male volunteers (aged 20-23 years), not involved in any sporting activities, were submitted to 13 weeks of training consisting of 30 min exercise [at 50%-75% maximal oxygen intake (VO2max)] on a cycle ergometer, performed 3 times a week. Every 4 weeks cardiac function was evaluated by measuring the systolic time intervals at rest and during submaximal cycle exercise. Stroke volume (SV), heart rate (HR) and blood pressure (BP) responses to submaximal exercise, VO2max and anaerobic threshold (AT) were also determined. Significant increases in VO2max, increases in AT and SV at the submaximal exercise intensities, as well as decreases in HR and BP were found after 4 weeks of training. Resting systolic time intervals were not affected by training, but during the submaximal cycle exercise the values of the pre-ejection period (PEP) and isovolumic contraction time (ICT) corresponding to HR of 100 beats.min-1 were significantly lowered after 13 weeks of training, whereas PEP, ICT and total electromechanical systole corresponding to HR of 130 beats.min-1 were significantly shortened by the 4th week. The ratios of PEP:LVET (left ventricular ejection time) and ICT:LVET during submaximal exercise were significantly lowered by training starting from the 8th week. These changes might be interpreted as evidence of the training-induced enhancement of the "contractility reserve", i.e. the ability to increase heart muscle contractility with increasing exercise intensity.     

Perceived exertion and gas exchange after calcium and beta-blockade in atrial fibrillation

Nine male patients (mean age 65 yr) with chronic atrial fibrillation underwent maximal exercise testing during placebo, beta-adrenergic (celiprolol, 600 mg), or calcium (diltiazem, 30 or 60 mg four times daily) channel blockade. The results were analyzed to determine which factors most closely related to ratings of perceived exertion (RPE) during exercise. Heart rate (HR), blood pressure (BP), oxygen uptake (VO2), minute ventilation (VE), and carbon dioxide production (VCO2) were evaluated at rest, 3.0 mph/0% grade, the gas exchange anaerobic threshold (ATge), 80% of placebo maximal O2 uptake, and maximal exercise. Both beta-adrenergic and calcium channel blockade significantly reduced heart rate and systolic blood pressure relative to placebo; these effects were more profound during beta-adrenergic blockade and as exercise progressed. Correlation coefficients and estimates of slope were derived for changes in RPE during exercise vs. changes in HR, VO2, VE, and VCO2 during the three treatments (r = 0.76 to 0.92, P less than 0.001). Although RPE was significantly correlated with HR during placebo and diltiazem therapy (r = 0.45, P less than 0.01), this was not the case during beta-adrenergic blockade (r = 0.31, NS). Slope of the regression lines between RPE and VO2, VE, and VCO2 did not differ between the three treatments. Slope of the regression lines between RPE and HR differed only during calcium channel blockade. Because the presence of atrial fibrillation and beta-adrenergic blockade altered the associations between RPE, VO2, and HR, these results suggest that VE is more closely related to RPE than the other parameters.     

Fluid replacement and glucose infusion during exercise prevent cardiovascular drift.

This study examined the influence of both hydration and blood glucose concentration on cardiovascular drift during exercise. We first determined if the prevention of dehydration during exercise by full fluid replacement prevents the decline in stroke volume (SV) and cardiac output (CO) during prolonged exercise. On two occasions, 10 endurance-trained subjects cycled an ergometer in a 22 degrees C room for 2 h, beginning at 70 +/- 1% maximal O2 uptake (VO2max) and in a euhydrated state. During one trial, no fluid (NF) replacement was provided and the subject's body weight declined 2.09 +/- 0.19 kg or 2.9%. During the fluid replacement trial (FR), water was ingested at a rate that prevented body weight from declining after 2 h of exercise (i.e., 2.34 +/- 0.17 1/2 h). SV declined 15% and CO declined 7% during the 20- to 120-min period of the NF trial while heart rate (HR) increased 10% and O2 uptake (VO2) increased 6% (all P less than 0.05). In contrast, SV was maintained during the 20- to 120-min period of FR while HR increased 5% and thus CO actually increased 7% (all P less than 0.05). Rectal temperature, SV, and HR were similar during the 1st h of exercise during NF and FR. However, after 2 h of exercise, rectal temperature was 0.6 degree C higher (P less than 0.05) and SV and CO were 11-16% lower (P less than 0.05) during NF compared with FR.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardiorespiratory response to absolute and relative work intensity in untrained men

Twenty young, untrained men performed two tests on cycle ergometer in order to verify whether the kinetics of the cardiorespiratory reactions exhibit any relation to maximal oxygen uptake (VO2max) in the untrained state. On the 1st day, the subjects exercised at work intensities of 50 and 100 W, the increase as a step function, for periods of 10 min each. The next day, they performed exercise at a relative intensity of 50% VO2max for 10 min. Respiratory frequency, tidal volume, minute ventilation (VE), heart rate (HR), stroke volume (SV), and cardiac output (Q) were measured continuously. The SV was measured by impedance plethysmography. All the cardiorespiratory variables increased rapidly at the onset of both absolute and relative intensity of work, with a faster response for Q than for VE. The increase in absolute intensity of work from 50 to 100 W caused a significantly slower cardiorespiratory reaction than at the beginning of exercise. The SV increased by 20 ml during first 20 s of both absolute and relative intensities of work and then began to decrease after 6 and 4 min of the exercise, respectively. The decrease in SV was associated with an increase in HR and a stable value of Q. Acceleration at the beginning of, and deceleration during recovery from, the relative intensity of work for VE, HR, and Q were well correlated with individual levels of VO2max in the tested men. It is concluded that the kinetics of cardiorespiratory reaction to a constant, relative intensity of work is related to VO2max in untrained men, and that the kinetics probably constitute a physiological feature of an individual.     

The relationship between lactate and ventilatory thresholds: coincidental or cause and effect?

To determine if blood lactate (LA) is the stimulus responsible for 'breakaway' ventilation (VE), the lactate (LT) and ventilation (VT) thresholds were monitored during one-legged cycling exercise. Ten healthy volunteer male subjects (Mean 2-legged VO2max = 4.27 l X min-1) performed prior exercise (PE) to reduce muscle glycogen stores by cycling at 75-85% of maximal heart rate (HR max) for 60-75 min, followed by a 30 h low carbohydrate diet. Pre- and post- LT and VT tests were performed on a cycle ergometer employing a continuous protocol with increments of 16 W every 3 min. Muscle biopsies were taken from the vastus lateralis muscle before the PE ride, prior to the threshold test 24 h later, and before testing the non-exercised (NE) leg. An I.V. catheter placed in the antecubital vein was used for serial blood samples taken at rest, and during the final 30 s of each progressive load. Gas analysis was calculated every 30 s (Beckman Metabolic Measurement Cart). Biopsies (N = 3) showed that the exercise and diet regimen elicited glycogen reduction which significantly (p less than 0.05) reduced R and the blood LA concentration in both the PE (2.62 to 1.99 mmol X l-1) and NE (2.87 to 2.26 mmol X l-1) legs at LT. At VT, LA concentrations were also significantly reduced in the PE (3.35 to 2.56 mmol X l-1) and NE (3.59 to 2.74 mmol X l-1) legs. VO2 and VE, however, were similar between pre- and post- tests.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of 3-day bed rest on physiological responses to graded exercise in athletes and sedentary men.

To test the hypotheses that short-term bed-rest (BR) deconditioning influences metabolic, cardiorespiratory, and neurohormonal responses to exercise and that these effects depend on the subjects' training status, 12 sedentary men and 10 endurance- and 10 strength-trained athletes were submitted to 3-day BR. Before and after BR they performed incremental exercise test until volitional exhaustion. Respiratory gas exchange and heart rate (HR) were recorded continuously, and stroke volume (SV) was measured at submaximal loads. Blood was taken for lactate concentration ([LA]), epinephrine concentration ([Epi]), norepinephrine concentration ([NE]), plasma renin activity (PRA), human growth hormone concentration ([hGH]), testosterone, and cortisol determination. Reduction of peak oxygen uptake (VO(2 peak)) after BR was greater in the endurance athletes than in the remaining groups (17 vs. 10%). Decrements in VO(2 peak) correlated positively with the initial values (r = 0.73, P < 0.001). Resting and exercise respiratory exchange ratios were increased in athletes. Cardiac output was unchanged by BR in all groups, but exercise HR was increased and SV diminished in the sedentary subjects. The submaximal [LA] and [LA] thresholds were decreased in the endurance athletes from 71 to 60% VO(2 peak) (P < 0.001); they also had an earlier increase in [NE], an attenuated increase in [hGH], and accentuated PRA and cortisol elevations during exercise. These effects were insignificant in the remaining subjects. In conclusion, reduction of exercise performance and modifications in neurohormonal response to exercise after BR depend on the previous level and mode of physical training, being the most pronounced in the endurance athletes.     

Muscle recruitment patterns regulate physiological responses during exercise of the same intensity

On different days, 10 men performed 30-min sessions of cycling at 50-55% of their peak oxygen uptake (VO(2)); one at 40 rpm and another at 80 rpm. Rectal temperature, heart rate (HR), mean arterial pressure (MAP), plasma lactate, glucose, insulin, and cortisol were measured before exercise, during the 15th and 30th min of exercise, and at 5 and 10 min postexercise. Rating of perceived exertion (RPE) was assessed 15 and 30 min into exercise. Electromyography established cadence-specific different intensities of quadriceps activation during cycling. At minute 30 of exercise and 5 min postexercise, HR was significantly (P < 0.05) greater at 40 rpm than at 80 rpm. MAP remained elevated longer after the 40-rpm than after the 80-rpm bout. Similarly, exercise-induced increases in plasma lactate persisted longer after the 40-rpm bout. Cortisol levels were elevated only at 40 rpm. RPE was higher during the slower cadence. These data indicated that the more pronounced muscle activation pattern associated with pedaling at 40 rpm resulted in greater physiological and psychophysiological stress than that observed at 80 rpm even though VO(2) was the same.     

Effects of detraining on cardiovascular responses to exercise: role of blood volume

In this study we determined whether the decline in exercise stroke volume (SV) observed when endurance-trained men stop training for a few weeks is associated with a reduced blood volume. Additionally, we determined the extent to which cardiovascular function could be restored in detrained individuals by expanding blood volume to a similar level as when trained. Maximal O2 uptake (VO2max) was determined, and cardiac output (CO2 rebreathing) was measured during upright cycling at 50-60% VO2max in eight endurance-trained men before and after 2-4 wk of inactivity. Detraining produced a 9% decline in blood volume (5,177 to 4,692 ml; P less than 0.01) during upright exercise, due primarily to a 12% lowering (P less than 0.01) of plasma volume (PV; Evans blue dye technique). SV was reduced by 12% (P less than 0.05) and VO2max declined 6% (P less than 0.01), whereas heart rate (HR) and total peripheral resistance (TPR) during submaximal exercise were increased 11% (P less than 0.01) and 8% (P less than 0.05), respectively. When blood volume was expanded to a similar absolute level in the trained and detrained state (approximately 5,500 +/- 200 ml) by infusing a 6% dextran solution in saline, the effects of detraining on cardiovascular response were reversed. SV and VO2max were increased (P less than 0.05) by PV expansion in the detrained state to within 2-4% of trained values. Additionally, HR and TPR during submaximal exercise were lowered to near trained values. These findings indicate that the decline in cardiovascular function following a few weeks of detraining is largely due to a reduction in blood volume, which appears to limit ventricular filling during upright exercise.     

Crossmodal session rating of perceived exertion response at low and moderate intensities

Session rating of perceived exertion (SRPE) permits global effort estimations after an exercise bout and has shown promise for evaluating training load. However, factors mediating SRPE are not well understood. The purpose of this study was to compare SRPE between cycling and treadmill exercise at low and moderate intensities. In a counterbalanced order, male subjects (n = 7) completed a VO2max trial on a cycle ergometer and a motor-driven treadmill. Then, participants completed trials at 50 and 75% mode-specific VO2max on a cycle ergometer (BK75, BK50) and a treadmill (TM75, TM50) to achieve ～ 400-kcal energy expenditure per trial. Acute RPE (i.e., during exercise) at 5 minutes, midway, and test termination were recorded with SRPE (20-minutes postexercise) expressed as overall (SRPEO), legs (SRPEL), and breathing also recorded were heart rate (HR) and change in rectal temperature (ΔTrec). Significance was accepted at p ≤ 0.05. Repeated-measures analysis of variance revealed significantly greater SRPE for higher intensities within each mode. Crossmodal comparisons also show a higher SRPE at moderate (75% VO2max) intensities [SRPEO] = BK75: 7.6 ± 1.0, TM75: 6.9 ± 1.3) vs. lower (50% VO2max) intensities (BK50: 4.6 ± 1.4, TM50: 4.6 ± 1.1). Within modes, SRPE corresponded well with ΔTrec and HR. Acute RPE was linked with intensity and drifted upward across time. Results indicated that overall and differentiated SRPEs are magnified with exercise intensity with the corresponding disruption in internal environment potentially mediating subjective responses. From a practical application standpoint, SRPE provides a subjective assessment for immediate evaluation of daily training. Results indicate that, when using SRPE to monitor training, consideration should be given to responses across differing exercise modes.     

Concurrent validity of an OMNI rating of perceived exertion scale for bench stepping exercise

To develop and validate a modified OMNI rating of perceived exertion (RPE) scale for use during bench stepping exercise (OMNI-BS). Thirty women (age: 19.8 ± 1.8 years) undertook 2 experimental trials, separated by 7 days. Concurrent validity was established by examining the relation between physiological criterion variables, oxygen consumption (VO2), and heart rate (HR), with the concurrent variable, RPE from OMNI-BS, during 2 trials in which the intensity increased linearly (test 1) and intermittently (test 2). The first test consisted of 3-minute stages. Subjects stepped up and down on the bench at 120 b·min(-1). The test was terminated owing to subject fatigue. Exercise intensity increased as bench height increased every 3 minutes. The second test consisted of three 3-minute exercise bouts that reproduced exercise stage 1 (low intensity), stage 3 (moderate intensity), and stage 5 (high intensity) performed in the first test. The order of these 3 exercise bouts was counterbalanced. Intraclass correlation analysis from experimental trials indicated a strong positive association between RPE and VO2 (r = 0.96 and r = 0.95) and HR (r = 0.95 and r = 0.95). Concurrent validity for the OMNI-BS RPE scale was established for women performing bench stepping exercise.     

Menstrual cycle phase affects temperature regulation during endurance exercise.

We investigated whether menstrual cycle phase would affect temperature regulation during an endurance exercise bout performed at room temperature (Ta) of 22 degrees C and 60% relative humidity. Nine eumenorrheic women [age 27.2 +/- 3.7 yr, peak O2 uptake (VO2) 2.52 +/- 0.35 l/min] performed 60 min of cycle exercise at 65% of peak VO2. Subjects were tested in both midfollicular (F) and midluteal (L) phases, although one woman did not show a rise in serum progesterone (P4) that is typically evident 1 wk after ovulation. VO2, rectal (Tre) and skin (Tsk) temperatures, heart rates (HR), and ratings of perceived exertion (RPE) were measured throughout exercise. Sweat loss (SL) was estimated from pre- and postexercise body weight differences. VO2, SL, and Tsk were not affected by menstrual cycle phase. Preexercise Tre was 0.3 degrees C higher during L than during F conditions, and this difference increased to 0.6 degrees C by the end of exercise (P less than 0.01). Compared with F, HRs during L were approximately 10 beats/min greater (P less than 0.001) at all times, whereas RPE responses were significantly greater (P less than 0.01) by 50 min of cycling. No differences in any measured values were found in the subject whose P4 was low in both test conditions. Results indicate that thermoregulation (specifically, regulation of Tre), as well as cardiovascular strain and perception of exercise, was adversely affected during the L phase.     

The effects of specificity of training on rating of perceived exertion at the lactate threshold

To determine the effects of cycle and run training on rating of perceived exertion at the lactate threshold (LT), college men completed a 40-session training program in 10 weeks (n = 6 run training, n = 5 cycle training, n = 5 controls). Pre- and post-training variables were measured during graded exercise tests on both the bicycle ergometer and treadmill. ANOVA on the pre- and post-training difference scores resulted in similar improvements in VO2max for both testing protocols, regardless of training mode. The run training group increased VO2 at the LT by 58.5% on the treadmill protocol and by 20.3% on the cycle ergometer. Cycle trainers increased VO2 LT only during cycle ergometry (+38.7%). No changes were observed in the control group. No differences for RPE at the LT were found before or after training, or between testing protocols for any group. Perception of exercise intensity at the LT ranged from "very light" to "light". The relationship between RPE and %VO2max was altered by the specific mode of training, with trained subjects having a lower RPE at a given %VO2max (no change in RPE at max.). It was concluded that RPE at the LT was not affected by training, despite the fact that after training the LT occurs at a higher work rate and was associated with higher absolute and relative metabolic and cardiorespiratory demands.     

Plasma volume shifts during progressive arm and leg exercise

Upper and lower body exercise was performed to assess the influence muscle mass has on plasma volume (PV) shifts. Nine male subjects (mean = 28 yr) completed a progressive intensity, discontinuous test with an arm crank (AC) and cycle (CY) ergometer. Power output (PO) levels for the AC were 25, 74, 98, and 133 W. PO levels for the CY were 49, 98, 147, and 263 W. At a given submaximal oxygen uptake (VO2), PV efflux was significantly greater for AC compared with CY exercise. When PV efflux was related to the relative intensity of the exercise (ergometer specific % peak VO2), responses were nearly identical. Maximal PV efflux was 18% for both AC and CY exercise. Mean arterial pressure (MAP) was significantly greater for AC compared with CY exercise for a given VO2. MAP plotted against the relative intensity of exercise, however, was similar for both AC and CY exercise. These results suggest that the amount of plasma efflux during exercise is related to the MAP, which is directly related to the relative intensity of the exercise.     

Influence of cold exposure on blood lactate response during incremental exercise

This study examined the effect of acute exposure of the whole body to cold on blood lactate response during incremental exercise. Eight subjects were tested with a cycle ergometer in a climatic chamber, room temperature being controlled either at 24 degrees C (MT) or at -2 degrees C (CT). The protocol consisted of a step increment in exercise intensity of 30 W every 2 min until exhaustion. Oxygen consumption (VO2) was measured at rest and during the last minute of each exercise intensity. Blood samples were collected at rest and at exhaustion for estimations of plasma norepinephrine (NE), epinephrine (E), free fatty acid (FFA) and glucose concentrations, during the last 15 s of each exercise step and also during the 1st, 4th, 7th, and the 10th min following exercise for the determination of blood lactate (LA) concentration. The VO2 was higher during CT than during MT at rest and during nearly every exercise intensity. At CT, lactate anaerobic threshold (LAT), determined from a marked increase of LA above resting level, increased significantly by 49% expressed as absolute VO2, and 27% expressed as exercise intensity as compared with MT. The LA tended to be higher for light exercise intensities and lower for heavy exercise intensities during CT than during MT. The E and NE concentrations increased during exercise, regardless of ambient temperature. Furthermore, at rest and at exhaustion E concentrations did not differ between both conditions, while NE concentrations were greater during CT than during MT. Moreover, an increase off FFA was found only during CT.(ABSTRACT TRUNCATED AT 250 WORDS)     

Role of hypoxemia for the cardiovascular responses to apnea during exercise

We sought to define the role of hypoxemia in eliciting the cardiovascular responses to apnea during exercise. Eleven men performed repeated apneas during 100-W steady-state exercise, either with normoxic gas (air) or 95% oxygen (oxygen). Beat-by-beat arterial blood pressure, arterial oxygen saturation, and heart rate (HR) were determined, and stroke volume (SV) was estimated from impedance cardiography calibrated with soluble gas rebreathing. There were large interindividual variabilities of HR, mean arterial pressure (MAP), and total peripheral resistance (TPR) at end-apnea (ea). However, for each individual, HR(ea), MAP(ea), and TPR(ea) were highly correlated between air and oxygen (R = 0.94, 0.78, and 0.93). HR decreased and MAP increased faster during apnea with air than with oxygen (ANOVA, P < 0.05), but MAP(ea) was not different between conditions. Cardiac output was reduced by 33% with air and by 11% with oxygen (P < 0.001 for air vs. oxygen). We conclude that the hypoxemia component cannot account for the wide interindividual differences of HR and TPR responses to apnea. However, hypoxemia augments the HR and TPR responses and may limit the MAP response to apnea by preventing a bradycardia-associated increase of SV.     

Cardiovascular responses to voluntary and nonvoluntary static exercise in humans.

We have measured the cardiovascular responses during voluntary and nonvoluntary (electrically induced) one-leg static exercise in humans. Eight normal subjects were studied at rest and during 5 min of static leg extension at 20% of maximal voluntary contraction performed voluntarily and nonvoluntarily in random order. Heart rate (HR), mean arterial pressure (MAP), and cardiac output (CO) were determined, and peripheral vascular resistance (PVR) and stroke volume (SV) were calculated. HR increased from approximately 65 +/- 3 beats/min at rest to 80 +/- 4 and 78 +/- 6 beats/min (P < 0.05), and MAP increased from 83 +/- 6 to 103 +/- 6 and 105 +/- 6 mmHg (P < 0.05) during voluntary and nonvoluntary contractions, respectively. CO increased from 5.1 +/- 0.7 to 6.0 +/- 0.8 and 6.2 +/- 0.8 l/min (P < 0.05) during voluntary and nonvoluntary contractions, respectively. PVR and SV did not change significantly during voluntary or nonvoluntary contractions. Thus the cardiovascular responses were not different between voluntary and electrically induced contractions. These results suggest that the increases in CO, HR, SV, MAP, and PVR during 5 min of static contractions can be elicited without any contribution from a central neural mechanism (central command). However, central command could still have an important role during voluntary static exercise.     

Possible biphasic sweating response during short-term heat acclimation protocol for tropical natives

The aim of the present study was to evaluate the sweat loss response during short-term heat acclimation in tropical natives. Six healthy young male subjects, inhabitants of a tropical region, were heat acclimated by means of nine days of one-hour heat-exercise treatments (40+/-0 degrees C and 32+/-1% relative humidity; 50% (.)VO(2peak) on a cycle ergometer). On days 1 to 9 of heat acclimation whole-body sweat loss was calculated by body weight variation corrected for body surface area. On days 1 and 9 rectal temperature (T(re)) and heart rate (HR) were measured continuously, and rating of perceived exertion (RPE) every 4 minutes. Heat acclimation was confirmed by reduced HR (day 1 rest: 77+/-5 b.min(-1); day 9 rest: 68+/-3 b.min(-1); day 1 final exercise: 161+/-15 b.min(-1); day 9 final exercise: 145+/-11 b.min(-1), p<0.05), RPE (13 vs. 11, p<0.05) and T(re) (day 1 rest: 37.2+/-0.2 degrees C; day 9 rest: 37.0+/-0.2 degrees C; day 1 final exercise: 38.2+/-0.2 degrees C; day 9 final exercise: 37.9+/-0.1 degrees C, p<0.05). The main finding was that whole-body sweat loss increased in days 5 and 7 (9.49+/-1.84 and 9.56+/-1.86 g.m(-2).min(-1), respectively) compared to day 1 (8.31+/-1.31 g.m(-2).min(-1), p<0.05) and was not different in day 9 (8.48+/-1.02 g.m(-2).min(-1)) compared to day 1 (p>0.05) of the protocol. These findings are consistent with the heat acclimation induced adaptations and suggest a biphasic sweat response (an increase in the sweat rate in the middle of the protocol followed by return to initial values by the end of it) during short-term heat acclimation in tropical natives.     

The relationship between anaerobic threshold and electromyographic fatigue threshold in college women

The purpose of this study was to investigate the relationship between anaerobic threshold (Th(an)) and muscle fatigue threshold (EMGFT) as estimated from electromyographic (EMG) data taken from the quadriceps muscles (vastus lateralis) during exercise on a cycle ergometer. The subjects in this study were 20 female college students, including highly trained endurance athletes and untrained sedentary individuals, whose fitness levels derived from their maximal oxygen consumption ranged from 24.9 to 62.2 ml.kg-1.min-1. The rate of increase in integrated EMG (iEMG) activity as a function of time (iEMG slope) was calculated at each of four constant power outputs (350, 300, 250, 200 W), sufficiently high to bring about muscle fatigue. The iEMG slopes so obtained were plotted against the exercise intensities imposed, resulting in linear plots which were extrapolated to zero slope to give an intercept on the power axis which was in turn interpreted as the highest exercise intensity sustainable without electromyographic evidence of neuromuscular fatigue (EMGFT). The Th(an) was estimated from gas exchange parameters during an incremental exercise test on the same cycle ergometer. The mean results indicated that oxygen uptake (VO2) at Than was 1.39 l.min-1, SD 0.44 and VO2 at EMGFT was 1.33 l.min-1, SD 0.57. There was no significant difference between these mean values (P greater than 0.05) and there was a highly significant correlation between VO2 at Than and VO2 at EMGFT (r = 0.823, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Control of cutaneous vascular conductance and sweating during recovery from dynamic exercise in humans.

The purpose of the study was to examine the effect of 1) passive (assisted pedaling), 2) active (loadless pedaling), and 3) inactive (motionless) recovery modes on mean arterial pressure (MAP), skin blood flow (SkBF), and sweating during recovery after 15 min of dynamic exercise. It was hypothesized that an active recovery mode would be most effective in attenuating the fall in MAP, SkBF, and sweating during exercise recovery. Six male subjects performed 15 min of cycle ergometer exercise at 70% of their predetermined peak oxygen consumption followed by 15 min of 1) active, 2) passive, or 3) inactive recovery. Mean skin temperature (T(sk)), esophageal temperature (T(es)), SkBF, sweating, cardiac output (CO), stroke volume (SV), heart rate (HR), total peripheral resistance (TPR), and MAP were recorded at baseline, end exercise, and 2, 5, 8, 12, and 15 min postexercise. Cutaneous vascular conductance (CVC) was calculated as the ratio of laser-Doppler blood flow to MAP. In the active and passive recovery modes, CVC, sweat rate, MAP, CO, and SV remained elevated over inactive values (P < 0.05). The passive mode was equally as effective as the active mode in maintaining CO, SV, MAP, CVC, and sweat rate above inactive recovery. Sweat rate was different among all modes after 8 min of recovery (P < 0.05). TPR during active recovery remained significantly lower than during recovery in the passive and inactive modes (P < 0.05). No differences in either T(es) or T(sk) were observed among conditions. Given that MAP was higher during passive and active recovery modes than during inactive recovery suggests differences in CVC may be due to differences in baroreceptor unloading and not factors attributed to central command. However, differences in sweat rate may be influenced by factors such as central command and mechanoreceptor stimulation.