VO2 Response Research Articles

Physiological Responses When Performing Resistive Arm Exercise While Walking

PURPOSE Performing resistive-arm exercise while walking can increase energy expenditure without raising the intensity of walking. We found that resistive arm exercise (waist belt with pull cords) raises energy expenditure approximately 30% during walking at a preferred pace. To achieve a greater rate of energy expenditure, it is possible that adding arm exercise while walking may be preferred over walking faster or jogging. The purpose of this study was to compare the physiological responses between resistive-arm exercise + walking (AW) to walking only (W) at a given VO2. METHODS Fourteen participants (age: 27 ± 9 yr; mean ± SD) performed two walk trials, the first at a preferred pace (AW) and the other at a faster pace (W) to match VO2 during AW. Walk time ranged from 5 to 8 min, during which steady state VO2, VE, HR, RPE and blood lactate were measured. Repeated measures ANOVA was used to determine differences between trials. RESULTS Preferred walk pace was 3.7 ± 0.3 mph during the AW trial. To match the VO2 during AW, walk pace during W was 4.2 ± 0.4 mph, 1.25 ± 1.1% grade. Despite similar VO2, HR and lactate responses; RPE was higher (p <0.03) during W compared to AW. VE was higher (p <0.01) during AW due to a higher breathing rate (32 ± 6 vs 27 ± 6 br/min), which was likely due to the set rate of cord pulling during arm exercise (30 pulls/min). CONCLUSIONS These data indicate that performing resistive arm exercise during a preferred walking pace may be a viable alternative to a more uncomfortable faster walking pace when attempting to increase energy expenditure. Partially supported by Walker's Warehouse, Tequesta, FL.Table

Misdiagnosis Of Hypertrophic Cardiomyopathy In An Elite Athlete

HISTORY An 35 year old, male International x-country and track endurance runner attended the CRY Centre for Sports Cardiology at the Olympic Medical Institute for second opinion following a diagnosis of hypertrophic cardiomypathy and advice to hault all high intensity training and competition. The initial diagnosis was made following 6 episodes of syncope reportedly during exercise, and echocardiographic evidence of left ventricular hypertrophy with a posterior free wall thickness of 14mm. PHYSICAL EXAMINATION Resting bradycardia with normal heart sounds and resting BP. DIFFERENTIAL DIAGNOSIS Hypertrophic Cardiomyopathy, Exercise Induced arrhythmia or vaso-vagal syndrome. TEST AND RESULTS The athlete had no family history of cardiovascular disease including Hypertrophic Cardiomyopathy and sudden cardiac death. On questioning the syncopal episodes always occured when the athlete ceased exercise to micturate. Resting ECG was unremarkable for an elite endurance athlete. Integrated cardiopulmonary stress test demonstrated a normal HR, BP, VO2, VCO2 and VE response with no inducible arrhythmia. Immediately on cessation of exercise blood pressure fell from 220/80 to 100/400 mmHg with a commensurate fall in HR from 192 to 50 bpm, leading to pre-syncopal symptoms described previously and near syncope abated by hyperventilation. Echocardiography was unremarkable with maximum wall thickness of 12mm and normal diastolic and systolic function. FINAL WORKING DIAGNOSIS Exercise induced vasovagal syndrome. TREATMENT AND OUTCOMES Continuation of training and competition with progressive warm-down built into sessions avoiding sudden cessation of exercise.

Active Muscle Mass And The Evaluation Of The Vo2 Response During Two-minute, All Out Exercise

Active Muscle Mass And The Evaluation Of The Vo2 Response During Two-minute, All Out Exercise

Interpretation and implementation of oxygen uptake kinetics studies in children with spastic cerebral palsy

From the scant data available, it seems that children with CP have a low maximum Vo2, a high O2 cost of submaximal exercise, and inefficient gait mechanics characterized by high levels of co-contraction. Despite the non-steady-state nature of habitual activity, there seem to be no published data focusing on Vo2 kinetics in children with CP Before measuring Vo2 kinetics, the noise content of the data needs to be examined because this has important implications for estimating tau Vo2 values. On the basis of the preliminary findings presented here, the breath-by-breath Vo2 responses of children with CP seem to have a similar noise magnitude to those of typically developing children; however, because they have smaller response amplitudes, the averaging of several repeated trials will be even more important than in typically developing children. Thorough habituation will be required to enable participants to complete the simulated step change exercise protocols that will enable Vo2 kinetics to be quantified. To facilitate appropriate comparisons with control groups on the basis of relative exercise intensities, further work is needed to establish the efficacy of estimating T(Lac) from gas exchange data in children with CP. By measuring Vo2, kinetics in children with CP, it is hoped that we will not only gain valuable insights into their exercise intolerance, but we will also have an important tool for assessing the effects of interventions using submaximal, and therefore less strenuous, exercise.

Effects Of Prior Warm-up Regime On Severe Intensity Cycling Performance

PURPOSE To test the hypothesis that prior heavy exercise would improve performance during subsequent severe intensity cycling performance, whereas prior moderate exercise would have no effect and prior sprint exercise would negatively affect performance. METHODS Following habituation to the experimental methods, 12 well-trained cyclists completed a series of 7 min performance trials, involving 2 min of constant work rate exercise at ∼90% VO2max and a further 5 min in which subjects attempted to maximise power output, both without prior intervention and 10 min following bouts of moderate, heavy or sprint exercise in a random order. Pulmonary gas exchange was measured breath-by-breath during all performance trials. RESULTS At the onset of the performance trial, baseline blood [lactate] was significantly elevated after heavy and sprint, but not moderate exercise (mean (SD): control, 1.0 (0.3) mM; moderate, 1.0 (0.2) mM; heavy, 3.0 (1.1) mM; sprint, 5.9 (1.5) mM). All three interventions significantly increased the amplitude of the primary VO2 response (control, 2.59 (0.28) L·min−1; moderate, 2.69 (0.27) L·min−1; heavy, 2.78 (0.26) L·min−1; sprint 2.78 (0.30) L·min−1). Mean power output was significantly increased by prior moderate and heavy exercise, but slightly reduced after sprint exercise (control, 330 (42) W; moderate, 338 (39) W; heavy, 339 (42) W; sprint, 324 (45) W). CONCLUSIONS These data indicate that priming exercise performed in the moderate and heavy intensity domains can improve severe intensity cycling performance by ∼2–3%, the latter condition doing so despite a mild lactacidosis being present at exercise onset.

Pulmonary Kinetics Of Oxygen Uptake And Sport Specific Fitness In Soccer Players

Elite soccer performance is, in part, dependent on a high level of cardiopulmonary fitness, which can either be assessed maximally (VO2max), or as a dynamic response to a change in work (VO2 kinetics). The kinetics of oxygen uptake (VO2) are enhanced following endurance training, and are also differentially fastest in elite endurance athletes; it is therefore surprising that VO2 kinetics have not been reported in intermittent sports such as soccer, where the ability to rapidly respond to a change in work is of importance. PURPOSE To compare laboratory (VO2 kinetics & VO2 max) and field based (Yo-Yo intermittent test) assessments of cardiopulmonary fitness in professional and amateur soccer players. METHODS A group of professional (Pro) (n = 18) and amateur (Am) (n = 18) soccer players agreed to participate in the study. Both groups performed 3 tests: 1) a graded exercise test to exhaustion for the determination of VO2 max 2) four repeats of a single exercise transient from walking to 80%Δ (80% of the difference between Tvent and VO2 max) for the assessment of VO2 kinetics, and 3) a soccer specific test (Yo-Yo Intermittent Recovery Test level 2). Gas exchange was measured breath-by-breath and a two component exponential model was used to characterise the kinetics of the VO2 response. Statistical analyses were made using ANOVA and ‘t’ tests as appropriate. RESULTS There was no difference in the cardiopulmonary fitness of the professional and amateur players when expressed as VO2 max (Pro 56.5 ± 2.9ml.kg·min−1 vs Am 55.7 ± 3.5ml.kg·min−1) or the VO2 kinetic fundamental (τ1 onset, Pro 24.5±3.2 s vs Am 24.0±1.8 s; τ1 offset, Pro 28.7±2.8 s vs Am 29.3±3.5 s) and slow components (τ2 onset, Pro 98.2±56.6 s vs Am 142.2±58.6 s; τ2 offset, Pro 261.1±60.7 s vs 277.8±71.7 s). However, professionals (966 ± 153m) achieved a greater total distance covered than amateurs (840 ± 156m) in the Yo-Yo test (p < 0.05). CONCLUSION The intermittent demands of soccer make the determination of specific fitness difficult to quantify. Nevertheless, the findings of this study suggest that sport specific assessment has greater relevance to the identification of fitness in performers participating at different levels of the sport. Whilst cardiopulmonary fitness is important for soccer performance, the ability to rapidly respond to a change in work rate does not contribute to the difference in soccer specific performance observed between the professional and amateur players. Other factors, such as anaerobic fitness, may be of more importance.

Effects of Prior Warm-up Regime on Severe-Intensity Cycling Performance

The purpose of the present study was to determine the effect of three different warm-up regimes on cycling work output during a 7-min performance trial. After habituation to the experimental methods, 12 well-trained cyclists completed a series of 7-min performance trials, involving 2 min of constant-work rate exercise at approximately 90% VO2max and a further 5 min during which subjects attempted to maximize power output. This trial was performed without prior intervention and 10 min after bouts of moderate, heavy, or sprint exercise in a random order. Pulmonary gas exchange was measured breath by breath during all performance trials. At the onset of the performance trial, baseline blood [lactate] was significantly elevated after heavy and sprint but not moderate exercise (mean +/- SD: control, 1.0 +/- 0.3 mM; moderate, 1.0 +/- 0.2 mM; heavy, 3.0 +/- 1.1 mM; sprint, 5.9 +/- 1.5 mM). All three interventions significantly increased the amplitude of the primary VO2 response (control, 2.59 +/- 0.28 L x min(-1); moderate, 2.69 +/- 0.27 L x min(-1); heavy, 2.78 +/- 0.26 L x min(-1); sprint, 2.78 +/- 0.30 L x min(-1)). Mean power output was significantly increased by prior moderate and heavy exercise but not significantly reduced after sprint exercise (control, 330 +/- 42 W; moderate, 338 +/- 39 W; heavy, 339 +/- 42 W; sprint, 324 +/- 45 W). These data indicate that priming exercise performed in the moderate- and heavy-intensity domains can improve severe-intensity cycling performance by ~2-3%, the latter condition doing so despite a mild lactacidosis being present at exercise onset.

Active Muscle Mass And The Evaluation Of The Vo2 Response During Two-minute, All Out Exercise

Active Muscle Mass And The Evaluation Of The Vo2 Response During Two-minute, All Out Exercise

Kinetics of V̇o2 and femoral artery blood flow during heavy-intensity, knee-extension exercise

It has been suggested that, during heavy-intensity exercise, O(2) delivery may limit oxygen uptake (.VO2) kinetics; however, there are limited data regarding the relationship of blood flow and .VO2 kinetics for heavy-intensity exercise. The purpose was to determine the exercise on-transient time course of femoral artery blood flow (Q(leg)) in relation to .VO2 during heavy-intensity, single-leg, knee-extension exercise. Five young subjects performed five to eight repeats of heavy-intensity exercise with measures of breath-by-breath pulmonary .VO2 and Doppler ultrasound femoral artery mean blood velocity and vessel diameter. The phase 2 time frame for .VO2 and Q(leg) was isolated and fit with a monoexponent to characterize the amplitude and time course of the responses. Amplitude of the phase 3 response was also determined. The phase 2 time constant for .VO2 of 29.0 s and time constant for Q(leg) of 24.5 s were not different. The change (Delta) in .VO2 response to the end of phase 2 of 0.317 l/min was accompanied by a DeltaQ(leg) of 2.35 l/min, giving a DeltaQ(leg)-to-Delta.VO2 ratio of 7.4. A slow-component .VO2 of 0.098 l/min was accompanied by a further Q(leg) increase of 0.72 l/min (DeltaQ(leg)-to-Delta.VO2 ratio = 7.3). Thus the time course of Q(leg) was similar to that of muscle .VO2 (as measured by the phase 2 .VO2 kinetics), and throughout the on-transient the amplitude of the Q(leg) increase achieved (or exceeded) the Q(leg)-to-.VO2 ratio steady-state relationship (ratio approximately 4.9). Additionally, the .VO2 slow component was accompanied by a relatively large rise in Q(leg), with the increased O(2) delivery meeting the increased Vo(2). Thus, in heavy-intensity, single-leg, knee-extension exercise, the amplitude and kinetics of blood flow to the exercising limb appear to be closely linked to the .VO2 kinetics.

Effect of Endurance Training on the &amp;OV0312;O2???Work Rate Relationship in Normoxia and Hypoxia

We postulated that the relationship between VO2 and work rate (VO2-WR relationship) during incremental exercise is dependent on O2 availability, and that training-induced adaptations alter this relationship. We therefore studied the effect of endurance training on VO2 response during incremental exercise in normoxia and hypoxia (FIO2=0.134). Before and after training (6 d.wk, 4 wk), eight subjects performed incremental exercises under normoxia and hypoxia and one constant-work rate exercise in normoxia at 80% of pretraining VO2max. The slopes of the VO2-WR relationship during incremental exercise were calculated using all the points (whole slope) or only points before the lactate threshold (pre-LT slope). The difference between VO2max measured and VO2max expected from the pre-LT slope (DeltaVO2) was determined, as was the difference between VO2 at minute 10 and VO2 at minute 4 during the constant-work rate exercise (DeltaVO2(10'-4')). In normoxia, training induced a significant decrease in the whole slope (11.0+/-1.0 vs 9.9+/-0.4 mL.min.W, P<0.05). In hypoxia, training induced a significant increase in the pre-LT slope (8.7+/-1.2 vs 9.8+/-0.7 mL.min.W; P<0.05) and the whole slope (8.5+/-1.2 vs 9.4+/-0.5 mL.min.W; P<0.05). A significant correlation between the decrease of DeltaVO2 and the decrease of DeltaVO2(10'-4') with training was found in normoxia (P<0.01, r=0.79). Taken together, these results indicate that adaptations induced by endurance training are associated with more efficient incremental and constant-workload exercise performed in normoxia. Moreover, training contributes to improved O2 delivery during moderate exercise performed in hypoxia, and to enhanced near-maximal exercise tolerance.

Temporal Aspects of the VO2 Response at the Power Output Associated with VO2peak in Well Trained Cyclists—Implications for Interval Training Prescription

The power output achieved at peak oxygen consumption (VO 2Peak) and the time this power can be maintained (i. e., Tmax) have been used in prescribing high-intensity interval training. In this context, the present study examined temporal aspects of the VO2 response to exercise at the cycling power that output well trained cyclists achieve their VO 2peak (i. e., Pmax). Following a progressive exercise test to determine VO 2peak, 43 well trained male cyclists (M age = 25 years, SD = 6; M mass = 75 kg, SD = 7; M VO2 peak = 64.8 ml-kg1 min−1, SD = 5.2) performed two Tmax tests 1 week apart. Values expressed for each participant are means and standard deviations of these two tests. Participants achieved a mean VO 2peak during the Tmax test after 176 s (SD = 40; M = 74% of Tmax, SD = 12) and maintained it for 66 s (SD = 39; M = 26% of Tmax, SD = 12). Additionally, they obtained mean 95% of VO 2peak after 147 s (SD = 31; M = 62% of Tmax, SD = 8) and maintained it for 95 s (SD = 38; M = 38 % of Tmax, SD = 8). These results suggest that 60–70 % of Tmax is an appropriate exercise duration for a population of well trained cyclists to attain VO 2peak during exercise at Pmax. However, due to intraparticipant variability in the temporal aspects of the VO2 response to exercise at Pmax, future research is needed to examine whether individual high-intensity interval training programs for well trained endurance athletes might best be prescribed according to an athlete's individual VO2 response to exercise at Pmax.

Overshoot in V?O2 following the onset of moderate-intensity cycle exercise in trained cyclists

We have previously observed that following the onset of moderate intensity cycle ergometry, the pulmonary O2 uptake (VO2) in trained cyclists often does not increase towards its steady-state value with the typical mono-exponential characteristics; rather, there is a transient "overshoot". The purpose of this study was to systematically examine this phenomenon by comparing the VO2 responses to two moderate-intensity work rates and one high-intensity work rate in trained and untrained subjects. Following a ramp exercise test to the limit of tolerance for the determination of the gas exchange threshold (GET) and VO2(peak), seven trained cyclists [mean (SD); VO2(peak) 66.6 (2.5) ml x kg(-1) x min(-1)] and eight sedentary subjects [VO2(peak) 42.9 (5.1) ml x kg(-1) x min(-1)] completed six step transitions from baseline cycling to work rates requiring 60% and 80% GET and three step transitions from baseline cycling to a work rate requiring 50% of the difference between GET and VO2(peak) (50%delta). VO2 was measured breath-by-breath and modelled using standard techniques. The sedentary subjects did not overshoot the steady-state VO2 at any intensity. At 60% GET, six of the seven cyclists overshot the steady-state VO2 [by an integral volume of 164 (44) ml between approximately 45 and 125 s]. At 80% GET, four of the seven cyclists overshot the steady-state VO2 [by an integral volume of 185 (92) ml between approximately 55 and 140 s]. None of the cyclists showed an overshoot at 50%delta. These results indicate that trained cyclists evidence an overshoot in VO2 before steady-state is reached in the transition to moderate-intensity exercise. The mechanism(s) responsible for this effect remains to be elucidated, as does whether the overshoot confers any functional or performance benefit to the trained cyclist.

Oxygen Uptake Response to an 800-m Running Race

We tested the hypothesis that time course of O (2) uptake (VO (2)) measured during a supramaximal exercise performed in the field is driven to maximal oxygen uptake (VO (2max)). On an outdoor track, five middle-distance male runners first performed a test to determine VO (2max) and a supramaximal 800-m running test at least two days apart. VO (2) response was measured from the start to the end of exercise with the use of a miniaturised telemetric gas exchange system (Cosmed K4). VO (2max) was reached by all subjects 45 +/- 11 s (mean +/- SD) after the onset of the 800-m race (i.e., 316 +/- 75 m), and was maintained during the next 33 +/- 6 s (i.e., 219 +/- 41 m). The mean relative exercise intensity of the 800 m was 120 % VO (2max). An unexpected significant decrease in VO (2) (24.1 +/- 7.0 %; p < 0.05) was observed in all subjects during the final 38 +/- 17 s (i.e., the last 265 +/- 104 m). We concluded that, at onset of a simulated 800 m running event, VO (2) is quickly projected towards the VO (2max), and then becomes limited by the achievable VO (2max). This race profile shown by all athletes is in some contrast to what can be expected from earlier findings in a laboratory setting.

Frequency of Verbal Encouragement Effects Sub-Maximal Exertional Perceptions During Exercise Testing in Young Adult Women

0915 PURPOSE: The purpose of this investigation was to determine the effect of frequency of verbal encouragement on ratings of perceived exertion (RPE) at sub-maximal exercise test intensities in young (18 to 21 year old) healthy females. METHODS: Thirty-six healthy females were randomly assigned to either a control group (no verbal encouragement), a 20 second encouragement group (verbal encouragement every 20s) or a 60 second encouragement group (verbal encouragement every 60s). All subjects completed two maximal exercise tests, a baseline test (without verbal encouragement) and an experimental test, using the Bruce treadmill protocol. Subjects were oriented to the OMNI-Walk/Run Scale which was used to assess RPE during the last 20 seconds of each exercise stage. RESULTS: Groups did not differ in age, body composition or baseline maximal aerobic power. Sub-maximal RPE-Overall was significantly lower for the 20 second encouragement group during stages II and III than baseline response (2.2 ± .75 vs. 3.5 ± 1.24, P < 0.01; 4.6 ± 1.0 vs. 6.1 ± 1.37, P < 0.01, respectively). Sub-maximal RPE-Overall responses were also significantly lower for the 60 second encouragement group during stage II and stage III than the baseline condition (2.25 ± .86 vs. 3.4 ± 1.0, P < 0.01; 5.0 ± 1.13 vs. 6.2 ± 1.33, P < 0.05, respectively). Submaximal RPE-Leg responses were significantly lower for the 20 second encouragement group during stages II and III than baseline response (2.3 ± 1.07 vs. 3.5 ± 1.16, P < 0.05; 4.6 ± 1.37 vs. 6.1 ± 1.6, P < 0.05, respectively). In addition, verbal encouragement every 60 seconds resulted in a significantly lower RPE-Legs response during stage II than in the baseline condition (2.3 ± .77 vs. 3.5 ± 1.0, P < 0.01). No between group differences were observed for any sub-maximal VO2 and HR response. There were no between or within group differences in maximal oxygen consumption and treadmill performance time. CONCLUSIONS: The findings suggest that the mechanisms underlying the psychological impact of verbal encouragement during sub-maximal exercise are complex but may include a dampening of unpleasant stimuli as they travel to the sensory cortex for coding and ultimately conscious expression as an exertional estimate.

Oxygen Consumption Changes During EECP Treatment in Patients with and without Coronary Artery Disease

1475 BACKGROUND: Enhanced External Counterpulsation (EECP) therapy has been found to be effective in increasing functional capacity and improving angina in patients with symptomatic coronary artery disease who are unable to undergo traditional revascularization procedures. It has been hypothesized that repetitive treatments of EECP may condition the cardiac and skeletal muscle, enhancing the ability of the muscles to more efficiently utilize consumed oxygen. PURPOSE: To determine the acute oxygen consumption (VO2) responses to EECP therapy, we evaluated VO2 responses during a single EECP therapy session in subjects with and without known coronary artery disease. METHODS: Twelve subjects (8 men, 4 women, mean +/− SD age = 50 +/− 18) volunteered to participate in the study. This group consisted of 7 healthy, sedentary individuals and 5 coronary artery disease patients. EECP treatment was performed using the TS3 EECP system (Vasomedical Corp, Westbury, NY) in conjunction with concomitant VO2 measurement (MedGraphics CPX/D, Medical Graphics Corp, Minneapolis, MN). VO2 was measured continuously throughout a 10-minute rest period, a 30-minute EECP protocol, and 10-minute recovery period. RESULTS: EECP therapy resulted in statistically significant increases (0.58 +/− 0.31 ml/kg/min; P = 0.0001) in VO2 as compared to those measured at rest. In addition, a significant decrease (−0.57 +/− 0.25 ml/kg/min; P = 0.0001) in VO2 was observed immediately following the cessation of therapy and throughout the recovery period. Intergroup comparisons showed cardiac patients to be older (P = 0.02), have higher body fat percentage (P = 0.03) and lower VO2 during EECP treatment (P = 0.05) as compared to their healthy counterparts. CONCLUSION: EECP therapy results in significant increases in somatic oxygen consumption as compared to measured resting and recovery levels. These finding highlight the potential significance of VO2 improvement as the mechanism underlying the benefits seen with EECP therapy.

Effect of L-NAME on the VO2 Response to Incremental Cycle Exercise

1587 Nitric oxide is believed to play a role both in muscle vasodilatation and in the regulation of oxidative metabolism during exercise. However, surprisingly few studies have investigated the effect of nitric oxide synthase (NOS) inhibition on oxygen uptake (VO2) during exercise in humans. PURPOSE: To determine the effect of NOS inhibition on the VO2 response to incremental cycle exercise. METHODS: Seven healthy males (aged 25 ± 4 yrs; mass 78.5 ± 9.2 kg) completed an incremental exercise test to exhaustion on an electrically braked cycle ergometer (work rate (WR) increment: 30 W.min−1) following prior intravenous infusion of either the NOS inhibitor L-NAME (4 mg.kg−1 body mass in 50 ml saline) or 50 ml saline as a placebo. Pulmonary gas exchange was measured nreath-by-breath. The gas exchange threshold (GET) was determined with the V-slope method and peak VO2 was defined as the average VO2 recorded over the last 30 s of the test. The ΔVO2-/ΔWR slope was calculated for the region from 1 min into exercise to the GET (S1) and from the GET to the attainment of peak VO2 (S2). The results were analysed using paired ttests. RESULTS: L-NAME resulted in an increase in mean arterial blood pressure immediately before exercise (mean ± S.D. L-NAME: 109 ± 10 vs. CON: 97 ± 8 mmHg; P<0.05) and within 30 s of the completion of exercise (L-NAME: 123 ± 9 vs. CON: 105 ± 15 mmHg; P<0.05). L-NAME also resulted in a reduction in heart rate immediately before exercise (L-NAME: 79 ± 8 vs. CON: 84 ± 10 b.min−1; P = 0.10), during exercise, and at exhaustion (L-NAME: 178 ± 7 vs. CON: 186 ± 10 b.min−1; P<0.01). L-NAME resulted in a significant reduction in peak VO2 (L-NAME: 3.80 ± 0.34 vs. CON: 4.02 ± 0.41 L.min−1; P<0.05). However, L-NAME did not significantly influence the GET (L-NAME: 2.01 ± 0.41 vs. CON: 1.94 ± 0.47 L.min−1), the ΔVO2−/ΔWR slopes S1(L-NAME: 8.7 ± 0.9 vs. CON: 8.7 ± 0.6 ml.min−1. W−1. W) or S2 (L-NAME: 9.1 ± 0.8 vs. CON: 9.2 ± 0.6 ml.min−1. W-1. W), or the time to exhaustion (L-NAME: 12.0 ± 1.1 vs. CON: 12.2 ± 1.3 min; P = 0.09). CONCLUSIONS: Inhibition of NOS with L-NAME reduces peak VO2 during incremental cycle exercise in man, presumably by altering central or peripheral components of muscle O2 delivery.

Oxygen Consumption Changes During EECP Treatment in Patients with and without Coronary Artery Disease

1475 BACKGROUND: Enhanced External Counterpulsation (EECP) therapy has been found to be effective in increasing functional capacity and improving angina in patients with symptomatic coronary artery disease who are unable to undergo traditional revascularization procedures. It has been hypothesized that repetitive treatments of EECP may condition the cardiac and skeletal muscle, enhancing the ability of the muscles to more efficiently utilize consumed oxygen. PURPOSE: To determine the acute oxygen consumption (VO2) responses to EECP therapy, we evaluated VO2 responses during a single EECP therapy session in subjects with and without known coronary artery disease. METHODS: Twelve subjects (8 men, 4 women, mean +/− SD age = 50 +/− 18) volunteered to participate in the study. This group consisted of 7 healthy, sedentary individuals and 5 coronary artery disease patients. EECP treatment was performed using the TS3 EECP system (Vasomedical Corp, Westbury, NY) in conjunction with concomitant VO2 measurement (MedGraphics CPX/D, Medical Graphics Corp, Minneapolis, MN). VO2 was measured continuously throughout a 10-minute rest period, a 30-minute EECP protocol, and 10-minute recovery period. RESULTS: EECP therapy resulted in statistically significant increases (0.58 +/− 0.31 ml/kg/min; P = 0.0001) in VO2 as compared to those measured at rest. In addition, a significant decrease (−0.57 +/− 0.25 ml/kg/min; P = 0.0001) in VO2 was observed immediately following the cessation of therapy and throughout the recovery period. Intergroup comparisons showed cardiac patients to be older (P = 0.02), have higher body fat percentage (P = 0.03) and lower VO2 during EECP treatment (P = 0.05) as compared to their healthy counterparts. CONCLUSION: EECP therapy results in significant increases in somatic oxygen consumption as compared to measured resting and recovery levels. These finding highlight the potential significance of VO2 improvement as the mechanism underlying the benefits seen with EECP therapy.

Influence of Strenuous Training on Cardiorespiratory Response Sensitivity and Primary Kinetics in Elite Rowers

1799 It was theorized that fatigue in elite athletes, induced by strenuous training sessions, is associated with a decrease in responsiveness of the cardiorespiratory system (CRS). PURPOSE: This study was conducted to determine the effect of strenuous training workloads on the sensitivity of the CRS in response to carbon dioxide, hypoxia, and changes in primary CRS kinetics in elite rowers. METHODS: 12 elite male rowers, members of the national team of Poland, age 21 +/− 0, 8 participated in this study. Participants were examined in the morning prior to strenuous training and the following day after strenuous trainings sessions (two daily sessions of intermittent types of workload characteristic for this group elite athletes). CO2, normocapnic hypoxia, and CRS sensitivity in rebreathing tests (standard rest) were measures as well as VE, VO2 and HR kinetics (monoexponential function) at 0,7 VO2max (transition from 25 W, on ergometer) All measurements were performed with the use of “Oxycon Alfa” (Jaeger). ANOVA with repeated measures were utilized for comparison between the groups. RESULTS: Significant changes of sensitivity and kinetics of CRS were uncovered after series of intermittent strenuous training sessions. In comparison with initial level ÄVE/ÄPACO2 was significantly decreased from 1.53 (0.11) to 1.34 (0.10) l•min−1per 1 mm Hg (p<0.05). Sensitivity of VE and HR to hypoxia responses were increased markedly (p<0.001). The rapid segments of VE response in 8 of 12 examined athletes was decreased (p<0.05). Half-time (T50) VO2 response significantly increased from 24.1 (1.3) to 29.6 (1.4) s (p<0.05). Also observed was a relationship in the changes in sensitivity to CO2 and kinetics (T50) VE and VO2 (r = −0.62 and −0.54, respectively, (p<0.05). CONCLUSION: The findings indicate that during recovery period (12–14 hours) after vigorous intermittent types of training, CRS sensitivity to CO2 and primary kinetics in elite rowers were decreased compared to a full recovery (24 hours). This might represent a specific integral feature of fatigue caused by intermittent training sessions. Such fatigue might limit the responsiveness of CRS to following exercise training session and possibly have modifying effects on training as well.

Effect of L-NAME on the VO2 Response to Incremental Cycle Exercise

1587 Nitric oxide is believed to play a role both in muscle vasodilatation and in the regulation of oxidative metabolism during exercise. However, surprisingly few studies have investigated the effect of nitric oxide synthase (NOS) inhibition on oxygen uptake (VO2) during exercise in humans. PURPOSE: To determine the effect of NOS inhibition on the VO2 response to incremental cycle exercise. METHODS: Seven healthy males (aged 25 ± 4 yrs; mass 78.5 ± 9.2 kg) completed an incremental exercise test to exhaustion on an electrically braked cycle ergometer (work rate (WR) increment: 30 W.min−1) following prior intravenous infusion of either the NOS inhibitor L-NAME (4 mg.kg−1 body mass in 50 ml saline) or 50 ml saline as a placebo. Pulmonary gas exchange was measured nreath-by-breath. The gas exchange threshold (GET) was determined with the V-slope method and peak VO2 was defined as the average VO2 recorded over the last 30 s of the test. The ΔVO2-/ΔWR slope was calculated for the region from 1 min into exercise to the GET (S1) and from the GET to the attainment of peak VO2 (S2). The results were analysed using paired ttests. RESULTS: L-NAME resulted in an increase in mean arterial blood pressure immediately before exercise (mean ± S.D. L-NAME: 109 ± 10 vs. CON: 97 ± 8 mmHg; P<0.05) and within 30 s of the completion of exercise (L-NAME: 123 ± 9 vs. CON: 105 ± 15 mmHg; P<0.05). L-NAME also resulted in a reduction in heart rate immediately before exercise (L-NAME: 79 ± 8 vs. CON: 84 ± 10 b.min−1; P = 0.10), during exercise, and at exhaustion (L-NAME: 178 ± 7 vs. CON: 186 ± 10 b.min−1; P<0.01). L-NAME resulted in a significant reduction in peak VO2 (L-NAME: 3.80 ± 0.34 vs. CON: 4.02 ± 0.41 L.min−1; P<0.05). However, L-NAME did not significantly influence the GET (L-NAME: 2.01 ± 0.41 vs. CON: 1.94 ± 0.47 L.min−1), the ΔVO2−/ΔWR slopes S1(L-NAME: 8.7 ± 0.9 vs. CON: 8.7 ± 0.6 ml.min−1. W−1. W) or S2 (L-NAME: 9.1 ± 0.8 vs. CON: 9.2 ± 0.6 ml.min−1. W-1. W), or the time to exhaustion (L-NAME: 12.0 ± 1.1 vs. CON: 12.2 ± 1.3 min; P = 0.09). CONCLUSIONS: Inhibition of NOS with L-NAME reduces peak VO2 during incremental cycle exercise in man, presumably by altering central or peripheral components of muscle O2 delivery.

HEART RATE AND VO2 RESPONSES TO INCREMENTAL EXERCISE WITH LAND AND AQUATIC CYCLING

Hydrostatic pressures enhance venous return to the heart during aquatic exercise, thus increasing stroke volume and reducing heart rate (HR). The current standard in aquatic therapy is to subtract 17 beats from the land-based (LB) HR to achieve an equivalent intensity for warm water (WW) exercise. PURPOSE The purpose of this study was to compare HR (bpm) and VO2 (ml/kg/min) responses to incremental exercise with LB and WW cycling using the 17 beat standard. METHODS Nine healthy subjects (5 males, 4 females, 21 ± 3 yrs) completed an LB graded maximal bicycle test and on a separate day a WW (33.3°C) bicycle test to assess HR and VO2 responses. The LB protocol followed an incremental increase in workload starting at 60% age predicted maximal HR with a 10% increase at each stage (I-V) leading to volitional fatigue. The WW test followed the same protocol with a 17 beat subtraction from LB HR at each stage. RESULTS All subjects met the criteria for volitional fatigue on each exercise test. As expected, peak HR was significantly lower for the WW test as compared to the LB test (185 ± 9.5 vs. 193 ± 7, p < 0.05). Peak VO2 was not significantly different between tests (41.7 ± 10 vs. 41.3 ± 7.1, p > 0.05). The submaximal (SM) HR values (p < 0.05) were significantly lower in water at each exercise stage. The SM VO2 values were also significantly lower in water than on land at each stage: I (13.7 ± 5.5 vs. 19.9 ± 3.9, p < 0.05), II (21.7 ± 5.6 vs. 25.2 ± 5.5, p < 0.05), III (25.2 ± 7.9 vs. 29.8 ± 6.0, p < 0.05) and IV (33.0 ± 5.7 vs. 38.0 ± 8.2, p < 0.05). CONCLUSIONS Despite the difference in peak HR's, peak VO2 values were equivalent. However, the WW values for both HR and VO2 at SM levels were significantly lower than the LB values. The WW HR was lower due to the implementation of the 17 beat subtraction from the LB HR. The observed differences in VO2 at SM levels suggests that the 17 beat land to water HR reduction may not be accurately depicting the same relative exercise intensity between LB and WW exercise.