Effect of acute calcium slow-channel antagonism on the cardiorespiratory response to graded exercise testing

The effect of acute calcium slow-channel antagonism on the cardiorespiratory responses of 12 healthy males was studied during multistage maximal exercise testing. Oral diltiazem (60 mg), nifedipine (10 mg), verapamil (80 mg), and placebo were administered in a randomized double-blind crossover fashion 1.5 h before an intermittent multistage cycle ergometer exercise test. At peak effort, heart rate, pulmonary ventilation, CO2 production, and respiratory exchange ratio were not significantly modified by drug ingestion. In contrast, maximal O2 consumption (2.6% reduction, P less than 0.02) and performance time (6.4% reduction, P less than 0.02) were reduced by nifedipine. During submaximal exercise, the chronotropic response was accentuated by nifedipine but not by diltiazem or verapamil. Furthermore, nifedipine altered the relationship of percentage of maximal O2 consumption to percentage of maximal heart rate, and both the relative and absolute O2 consumption corresponding to 70% and 85% of the maximal heart rate were significantly reduced after nifedipine ingestion. The results indicated that in persons without symptomatic coronary artery disease exercise performed at a given percentage of the maximal heart rate will yield a lower than expected relative and absolute intensity in the presence of acute nifedipine-induced calcium slow-channel antagonism.     

The long-acting phosphodiesterase inhibitor tadalafil does not influence athletes' VO2max, aerobic, and anaerobic thresholds in normoxia

Whereas experimental studies showed that in healthy trained subjects, the phosphodiesterase-5 inhibitor (PDE-5i) sildenafil improves exercise capacity in hypoxia and not in normoxia, no studies on the effects of the long half-life PDE-5i tadalafil exist. In order to evaluate whether tadalafil influences functional parameters and performance during a maximal exercise test in normoxia, we studied 14 healthy male athletes in a double-blind cross-over protocol. Each athlete performed two tests on a cycle ergometer, both after placebo or tadalafil (at therapeutic dose: 20 mg) administration. Oxygen consumption (VO2), blood lactate, respiratory exchange ratio, rate of perceived exertion, arterial blood pressure (BP), heart frequency (HR) and oxygen pulse (VO2/HR) were evaluated before exercise, at individual ventilatory and anaerobic thresholds (IVT and IAT), at VO2max and during recovery. Compared to placebo, a single tadalafil administration significantly reduced systolic BP before and after exercise (p < 0.05), decreased VO2/HR at IVT (13.3 +/- 1.8 vs. 14.5 +/- 2.1 mL . beat (-1); p = 0.03), but did not modify individual VO2max, IVT, or IAT. In healthy athletes, 20 mg of tadalafil does not substantially influence physical fitness-related parameters, exercise tolerance, and cardiopulmonary responses to maximal exercise in normoxia; it remains to be verified if higher doses/prolonged use influence health and/or sport performance in field conditions.     

Physiological predictors of performance in cross-country skiing from treadmill tests in male and female subjects

In order to study which parameter that best corresponds to performance during cross-country skiing, seven male and nine female cross-country skiers were tested with treadmill tests. Parameters measured or computed by metabolic gas measurements were the anaerobic threshold (AT), threshold of decompensated metabolic acidosis (TDMA), the exercise intensity where the Respiratory exchange ratio reaches 1.0 (R = 1) and peak oxygen (O2) uptake (VO2peak). Onset of blood lactate accumulation (OBLA, 4 mmol.l-1 blood lactate) was also measured. The various parameters were measured in percentage of maximal heart rate, percentage of peak O2 uptake, VO2 ml.kg-1.min-1, VO2 ml.min-1.kg-2/3 and VO2 l.min-1. Results from four large competitions were also collected to rank the subjects. With correlation analysis, it was revealed that in male subjects a high OBLA was associated with good ranking results (r = (-0.829) - (-0.964); P < 0.05-0.001). In female subjects, the best association with competition results was found for R = 1 (r = (-0.715) - (-0.810); P < 0.05). Concerning VO2 measurements, for male subjects the unit l.min-1 is suggested to be used and for female subjects either the units l.min-1, ml.min-1.kg-2/3, or ml.kg-1.min-1 could be used when predicting performance in cross-country skiing. In conclusion, treadmill tests can be used for the prediction of performance in cross-country skiing. Further, various parameters from treadmill tests in men and women are best used as predictors of performance in cross-country skiing.     

Acute effects of marihuana smoking on maximal exercise performance

To evaluate the effects of marihuana smoking on exercise performance, 12 healthy young subjects did progressive exercise testing on an ergocycle to exhaustion under two conditions: non-smoking (control) and 10 min after smoking a marihuana cigarette (containing 1.7% of delta-9-tetra-hydro-cannabinol) of 7 mg X kg-1 body weight. Heart rate, arterial blood pressure, minute ventilation (VE), breathing rate (fb), oxygen uptake (VO2), and carbon dioxide output (VCO2) were measured before, during, and for 4 min after the exercise. Tidal volume was calculated from VE X fb-1. The exercise duration was also measured. Forced expiratory volume (FEV1) was measured: before smoking (rest); before exercise (10 min after smoking); and after exercise. Carboxyhemoglobin levels were measured before and 10 min after smoking in four subjects. Marihuana smoking reduced exercise duration (16.1 +/- 4.0 to 15.1 +/- 3.3 min, P less than 0.05). At peak exercise performance, there were no differences in VO2, VCO2, heart rate, and VE between the two experimental conditions. Marihuana induced tachycardia at preexercise (94.3 +/- 13.3 beats X min-1 to 119.0 +/- 18.0, P less than 0.01) that was sustained up to 80% of maximum effort and during the recovery period. After marihuana, VE, VO2 and VCO2 were increased above control from 50% of maximum effort to the end of the test. Marihuana induced a bronchodilation (FEV1 from 4.28 +/- 1.00 to 4.43 +/- 1.031, P less than 0.0) that was still present after exercise. Exercise induced a bronchodilation in the control condition but not in the marihuana smoking condition.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of salbutamol on performance in elite nonasthmatic athletes.

The effect of salbutamol on performance was studied in seven male nonasthmatic highly trained (VO2max > or = 60 ml.kg-1 x min-1) cyclists. Salbutamol (S = 2 puffs = 200 micrograms) or placebo (P) was administered by metered-dose inhaler, through a spacer device, 20 min prior to testing in a double-blind, randomized cross-over design. Testing sessions on a cycle ergometer included the measurement of maximal oxygen uptake (VO2max), peak power, maximal heart rate, and pulmonary function. A timed sprint to exhaustion was performed after 45 min of exercise at 70% of VO2max, and a Wingate anaerobic test was used to measure total work and peak power. There was a nonsignificant decrease in VO2max (P = 63.5 +/- 3.2; S = 62.6 +/- 3.3 ml.kg-1 x min-1). No difference was found in peak power, maximum heart rate, endurance sprint time, Wingate peak power, or total work. After an anticipated baseline increase was taken into account, the pattern of change in FEV1 over time did not differ between salbutamol and placebo. It was concluded that a therapeutic dose of aerosol salbutamol does not have an ergogenic effect in elite nonasthmatic athletes, and it is therefore recommended that inhaled salbutamol continue to be permitted in international competition for individuals with exercise induced bronchospasm.     

Maximal exercise responses to acute and chronic beta-adrenergic blockade in healthy male subjects

Conflicting data on the alterations in the maximal exercise response to beta blockade (BB) may be the result of differences in the length of time the subject has been on medication, i.e., hours vs days. The purpose of this study was to examine maximal exercise responses during acute and chronic administration of BB. Twenty-eight healthy males, 14 untrained (UT) and 14 involved in a personal training regimen (TR), performed maximal treadmill tests after 1 d and 9 d under three double-blind, randomized conditions: a placebo (PLAC), propranolol (PROP) 80 mg b.i.d., and atenolol (ATEN) 100 mg o.d. Maximal heart rate (HR), oxygen consumption (VO2), ventilation (VE), and treadmill time were significantly reduced by PROP and ATEN after an acute and chronic dose when compared to PLAC (P less than 0.05) in both groups of subjects. Maximal HR was decreased more after 1 d of BB than after 9 d of BB with both PROP and ATEN in the UT subjects and with PROP only in the TR group. VO2max, VEmax, and treadmill time were also less attenuated after 9 d of BB; however, this trend did not reach statistical significance. The nonselective beta blocker, PROP, caused greater reductions in VO2max compared to the selective beta blocker, ATEN, in both groups of subjects. These data indicate that, other than a small change in maximal HR, there is no difference in the exercise response to acute and chronic BB in normal and highly conditioned individuals.     

Effects of rider position on continuous wave Doppler responses to maximal cycle ergometry.

Using 10 well-trained (VO2peak = 60.6 ml kg-1min-1) college age cyclists and continuous wave Doppler echocardiography, peak acceleration (PkA) and velocity (PkV) of blood flow in the ascending aorta, and the stroke velocity integral (SVI) were assessed to determine if rider position influenced the central haemodynamic responses to graded maximal cycle ergometry. Cyclist position was determined by hand placement on the uprights (UPRI) or drops (DROP) of conventional handlebars or using aerodynamic handlebars (AHB). All subjects consistently achieved a peak workload of 300 W. The Doppler variables did not differ significantly between rider positions at each stage of the maximal exercise tests but did change in response to increasing workloads. PkA was significantly (P < 0.05) greater at workloads > or = 240 W versus < or = 120 W. PkV increased significantly (P < 0.05) up to 180 W and then reached a plateau. SVI increased to a workload of 120 W and then progressively declined, becoming significantly (P < 0.05) less at 300 W. For each stage, neither submaximal VO2, VI nor heart rate (HR) differed significantly between each trial. These results suggest that rider position does not affect the physiological response to maximal bicycle ergometry as responses to each position are similar.     

Comparison of physiological strain and muscular performance of athletes during two intermittent running exercises at the velocity associated with VO2max

The purpose of this study was to examine physiological strain and muscular performance responses of well trained athletes during two intermittent running exercise protocols at the velocity associated with VO2max. Ten national level middle-distance runners (VO2max 69.4+/-5.1; mean+/-SD) performed in random order two 28 min treadmill running exercises: 14 bouts of 60 s runs with 60 s rest (IR60) and 7 bouts of 120 s runs with 120 s rest between each run (IR120). During IR120 peak oxygen uptake (12%), peak heart rate (3%) and peak blood lactate (79%) were significantly higher than during IR60 (P< 0.001) and almost the same as in the VO2max test. In IR120 the relative aerobic energy release calculated on the basis of the accumulated oxygen deficit during the running bouts was significantly higher than in IR60 (81.5+/-2.7 vs. 70.2+/-2.6%, P<0.001) likewise the sum oxygen consumption during the 14 min running (P< 0.001), while during the 14 min recovery it was as much lower (P < 0.001). There were no changes either during or between the IR60 and IR120 protocols with regard to the muscular performance parameters, stride length or height of maximal vertical jumps. In conclusion, during intermittent running at the velocity associated with VO2max doubling the duration of work and rest bouts from 60 s to 120s increased the physiological strain of well trained athletes to the same level as at exhaustion in the VO2max test but the muscular performance variables were not influenced.     

Effects of diltiazem or propranolol during exercise training of hypertensive men

This was a prospective, randomized, double-blind, placebo-controlled trial to establish whether beta blockers or calcium-channel blockers limit exercise capacity and training responses in men with mild hypertension. Circuit weight and aerobic training was used to assess the effects of drugs on cardiovascular fitness and muscle strength. Fifty-two sedentary men, ages 25-59 yr, with a diastolic blood pressure of 90-105 mm Hg off drugs, without significant ST depression during maximal stress testing, received diltiazem, propranolol, or placebo. Maximal oxygen uptake (VO2max) and exercise duration during treadmill testing, as well as one-repetition maximal strength, were assessed on eight weight machines after a single-blind placebo baseline, after 2 wk of drug run-in, and after 10 wk of exercise training. Total daily doses were 240 mg for propranolol and 360 mg for diltiazem. Propranolol decreased VO2max after drug run-in (P less than 0.05). Exercise training increased VO2max (P less than 0.05) in the diltiazem and placebo groups. After training VO2max in the propranolol group increased (P less than 0.05) from run-in but not beyond baseline levels. Thus, the reduction of VO2max consequent to propranolol therapy limited the overall benefits of training. Exercise duration did not change with run-in and increased (P less than 0.05) with training by 22%, 19%, and 10% for the diltiazem, placebo, and propranolol groups, respectively. Strength after run-in was unchanged, and exercise training increased strength (P less than 0.0001) on all weight machines in all groups. The results show an advantage of diltiazem to propranolol, particularly among physically active patients engaged in aerobic exercise who require antihypertensive therapy.     

Pre-exercise feeding does not affect endurance cycle exercise but attenuates post-exercise starvation-like response

The effects of ingesting a mixed-snack food (CB), fructose (FRU), or placebo (PBO) prior to exercise (70% peak VO2) on the metabolic response during and after cycle exercise were studied in eight normal healthy volunteers with a wide range of peak VO2 (30-70 cc.kg-1.min-1). The study was designed to minimize the impact of confounding factors by using various strategies. First, the volunteers were grouped in teams with stratification by peak VO2, and the tests were randomized by a Latin-square design. Second, subjects received two acclimation trials in the cycle ergometer to diminish the effect of learning experiences and allow them to get used to the room and equipment. In addition, financial incentives were offered for team and individual endurance times. The test meals were administered 30 min prior to the beginning of exercise, and the subjects exercised to exhaustion, which was defined with clear-cut endpoints. Gas and blood samples were taken at regular intervals before, during, and for 60 min after each exercise bout. CB and FRU induced higher pre-exercise glucose and insulin concentrations. Blood lactate increased 100% with FRU ingestion. Despite these differences; endurance time, substrate, and hormone concentrations as well as rates of substrate oxidation during exercise were identical among the three conditions. During the post-exercise recovery period, PBO was associated with a starvation-like pattern of substrate utilization in which lipid oxidation was 60% greater and carbohydrate oxidation 50% less than following either CB (75 +/- 11, 248 +/- 27 mg.min-1, P less than 0.05) or F ingestion (93 +/- 4, 221 +/- 14 mg.min-1).(ABSTRACT TRUNCATED AT 250 WORDS)     

Exercise training below and above the lactate threshold in the elderly

In this study we report the effects of training at intensities below and above the lactate threshold on parameters of aerobic function in elderly subjects (age range 65-75 yr). The subjects were randomized into high-intensity (HI, N = 8; 75% of heart rate reserve = approximately 82% VO2max = approximately 121% of lactate threshold) and low-intensity (LI, N = 9; 35% of heart rate reserve = approximately 53% VO2max = approximately 72% of lactate threshold) training groups which trained 4 d.wk-1 for 30 min.session-1 for 8 wk. Before and after the training, subjects performed an incremental exercise test for determination of maximal aerobic power (VO2max) and lactate threshold (LT). In addition, the subjects performed a 6-min single-stage exercise test at greater than 75% of pre-training VO2max (SST-High) during which cardiorespiratory responses were evaluated each minute of the test. After training, the improvements in VO2max (7%) for LI and HI were not different from one another (delta VO2max for LI = 1.8 +/- 0.7 ml.kg-1.min-1; delta VO2max for HI = 1.8 +/- 1.0 ml.kg-1.min-1) but were significantly greater (P = 0.02) than the post-testing change observed in the control group (N = 8). Training improved the LT significantly (10-12%; P less than 0.01) and equally for both LI and HI (delta LT for for LI = 2.3 +/- 0.6 ml O2.kg-1.min-1; delta LT for HI = 1.8 +/- 0.8 ml O2.kg-1.min-1).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of formoterol on endurance performance in athletes at an ambient temperature of -20 degrees C

The use of inhaled beta2-agonists is restricted in sports. No benefit of inhaled formoterol upon performance was found in healthy athletes under normal climatic conditions, but it has not been investigated whether formoterol improves performance in athletes during exposure to cold. To investigate the effect of inhaled formoterol vs placebo upon performance and lung function at -20 degrees C in 20 healthy male athletes. We used a randomized double-blind, placebo-controlled, cross-over design. The subjects performed a run until exhaustion after inhaled study drug. The speed was 95% of the predetermined maximal oxygen uptake (VO2 max) the first minute and increased to 107% of VO2 max for the remaining part of the test. Time until exhaustion, ventilation (VE), VO2, respiratory rate (RR), tidal volume (VT), heart rate (HR) and arterial oxyhemoglobin saturation (SPO2) were recorded during exercise. Lung function was measured before inhaling, after inhaling the study drug and after the treadmill run. Inhaled formoterol did not improve endurance performance in cold environments compared with placebo, although formoterol significantly improved lung function (FEV1, FEF50 and PEF) and HR 4 min after the start of the exercise. Inhaled formoterol did not improve endurance performance in healthy, well-trained athletes exposed to cold.     

Metabolic and cardiorespiratory responses to the performance of Wing Chun and T'ai Chi Chuan exercise

The primary purpose of this study was to examine the metabolic and cardiorespiratory responses to the continuous performance of Wing Chun and T'ai Chi Chuan exercise. No significant differences in VO2max or HRmax obtained during treadmill exercise were found between the practitioners of the two styles. Average values for oxygen uptake (VO2) were 23.3 +/- 7.5 ml.kg-1.min-1 (6.6 METS) and 16.0 +/- 3.9 ml.kg-1.min-1 (4.6 METS) for Wing Chun and T'ai Chi Chuan exercise, respectively. Mean heart rates obtained during exercise were 137 +/- 25 beats.min-1 for Wing Chun and 116 +/- 22 beats.min-1 for T'ai Chi Chuan exercise. These exercise values corresponded to 52.4% of VO2max and 70.5% of HRmax for Wing Chun and only 36.4% of VO2max and 59.8% of HRmax for T'ai Chi Chuan exercise. Thus, only the continuous performance of Wing Chun exercise elicited VO2 and HR responses that would be expected to bring about a cardiorespiratory training effect in subjects with a relatively low initial VO2max. The ventilatory equivalent for oxygen (VE/VO2) obtained during T'ai Chi Chuan exercise (21.7) was significantly lower than for Wing Chun exercise (24.2), suggesting that T'ai Chi practitioners utilize efficient breathing patterns during exercise. Both Wing Chun and T'ai Chi Chuan styles may have a small static component that produces a slightly elevated heart rate relative to metabolic load when compared to traditional aerobic activities. However, the effect was not severe and these forms of exercise should not be considered dangerous for individuals at high risk for cardiovascular disease.     

Influence of caffeine on blood lactate response during incremental exercise

To test the hypothesis that caffeine ingestion prior to exercise would delay the onset of blood lactate accumulation, eight male subjects were studied during incremental exercise to maximal work rates on a cycle ergometer under two conditions: 1 h after ingestion of 200 ml of either decaffeinated, calorie-free cola (control trial) or the same cola drink with 5 mg caffeine/kg body weight added (caffeine trial). Maximal exercise values for oxygen consumption (VO2 max), ventilation, heart rate, respiratory exchange ratio (R), work rate, and blood lactate were not affected by caffeine. Submaximal exercise VO2, ventilation, and R also were unaffected by caffeine. During the caffeine trial, submaximal exercise blood lactate was significantly higher and heart rate significantly lower than during the control trial (P less than 0.05). The lower exercise heart rate at the same VO2 resulted in a significantly greater O2 pulse during all submaximal exercise intensities for the caffeine trial (P less than 0.05). Data on R indicated that caffeine had no effect on substrate utilization during exercise. Data on exercise blood lactate response suggested that caffeine does not delay and may accelerate the onset of blood lactate accumulation during incremental exercise. When defined as either a "breakpoint," delta l mM (above resting lactate), or fixed level of 4 mM, the lactate threshold (LT) did not differ between caffeine and control trials. However, in using a 2 mM lactate level as a criterion, the LT during the caffeine trial (2.13 +/- 0.22 l X min-1) was significantly (P less than 0.05) lower than during the control trial (2.71 +/- 0.17 l X min-1).(ABSTRACT TRUNCATED AT 250 WORDS)     

Postexercise hypotension and hemodynamics: the role of exercise intensity

AIM: Although postexercise hypotension (PEH) has already been extensively demonstrated, the influence of exercise intensity on its magnitude and mechanisms is still controversial. METHODS: Twenty-three normotensive subjects were submitted to a control (45 minutes of rest) and 3 exercise sessions (cycle ergometer, 45 minutes at 30%, 50% and 75% of .VO(2peak)) to investigate the role of exercise intensity on PEH. Blood pressure (BP - auscultatory), heart rate (HR - ECG), and cardiac output (CO - CO2 rebreathing) were measured before and after the control and exercise sessions. RESULTS: Systolic BP decreased significantly after exercise at 50% and 75% of .VO(2peak). Diastolic BP increased significantly during the control session, did not change after exercise at 30% of .VO(2peak), and decreased significantly after exercise at 50% and 75% of .VO(2peak). This fall was greater and longer after more intense exercise. CO and systemic vascular resistance (SVR) responses were similar between sessions, CO increased whereas SVR decreased significantly. Stroke volume (SV) increased and heart rate (HR) decreased following control and exercise at 30% of .VO(2peak) whereas SV decreased and HR increased after exercise at 50% and 75% of .VO(2peak). CONCLUSION: PEH is greater and longer after more intense exercise. BP profile is followed by a decrease in SVR and an increase in CO, what was not influenced by previous exercise. The increase in CO is caused by an increase in SV after rest and low intensity exercise and by an increase in HR after moderate and more intense aerobic exercise.     

Cardiovascular responses during upright and semi-recumbent cycle ergometry testing

To compare cardiovascular (CV) responses during cycle ergometry testing, 20 unmedicated mild hypertensive subjects (10 male, 10 female; mean age = 47.9 yr) underwent exercise testing on an upright (UP) cycle and a semi-recumbent (SR) cycle. Tests were administered in counterbalanced order on two separate days. Heart rate (HR), blood pressure (BP), ventilation (VE), and rate pressure product (RPP) were recorded at absolute workloads (1.0 and 1.5 l.min-1) as well as at relative workloads (50, 75, and 90% of VO2 peak). In addition, the CV variables were measured at rest and peak exercise for each position. At absolute submaximal levels, women had higher HR, VE, and RPP values in both positions, reflecting responses at a greater percentage of their maximum exercise capacity. At relative workloads, HRs were significantly lower at rest and at 75 and 90% VO2 peak in the SR position. Men had greater systolic blood pressure (SBP) and RPP in both positions, and RPP was significantly lower at rest and at 75 and 90% VO2 peak in the SR position. Women displayed lower VE at all relative workloads. At peak exercise, subjects achieved significantly higher peak heart rates on the upright cycle (UP = 163 bpm, SR = 157 bpm). The UP cycle was associated with higher levels of peak VO2. The ability to achieve a higher HR and greater VO2 at peak exercise suggests that the UP cycle ergometer may be a preferable mode to the SR ergometer for evaluating maximal exercise performance among patients with mild hypertension.     

Physiological response to water aerobics.

Heart rate (HR) and oxygen uptake (VO2) measured during water aerobics (WA) were compared to maximal values obtained during an incremental treadmill test to assess the energy demand and potential cardiorespiratory (CR) training effects of WA. Sixteen college-age females served as subjects (mean +/- SD = 20.4 +/- 1.6 years). WA elicited a mean HR of 162 b.min-1 and a mean VO2 of 18.4 ml.kg-1.min-1 which represented 74% of HR reserve, 82% of maximal HR, and 48% of VO2 max. Average caloric expenditure was 5.7 kcal.min-1. HR values for WA were consistent with guidelines established by the American College of Sports Medicine for developing and maintaining CR fitness in healthy adults. However, the VO2 fell just below the recommended minimum threshold level. It was concluded that WA may provide an attractive alternative to traditional modes of exercise for improving CR fitness, however, HR measures may overestimate the metabolic intensity of the exercise.     

Cardiorespiratory fitness in highly active versus inactive paraplegics

Maximum and submaximum arm crank exercise performances were assessed in male paraplegics (PARA) with the purpose of comparing cardiovascular responses among individuals of highly active (A, N = 15) vs inactive (I, N = 15) lifestyles. The A PARAs (average VO2 peak during arm cranking 2.24 l.min-1) demonstrated a significantly higher maximal cardiorespiratory fitness compared to I subjects (average VO2 peak 1.56 l.min-1). During graded arm exertion, at exercise intensities approximating 45%, 57%, and 70% of VO2 peak, the active subjects developed cardiac outputs (assessed via CO2-rebreathing) ranging from 9.07 to 11.21 l.min-1; a 34-44% advantage relative to their inactive counterparts (6.30-8.36 l.min-1). Similarly, exercise stroke volumes for A (76-80 ml) were 38-45% higher than for I paraplegics (55-56 ml). Although both groups demonstrated a distinctive circulatory hypokinesis during arm cranking, the immediate pattern of cardiovascular response was dissimilar for the highly active versus inactive subjects. The former demonstrated a predominantly "central" adaptation to steady-state arm exercise (exhibiting normal stroke volumes and arteriovenous O2 extractions for spinal cord-injured subjects), while the latter displayed markedly reduced stroke volumes concomitant with abnormally large peripheral arteriovenous oxygen extractions for a given oxygen uptake.