Incremental Cycle Ergometer Exercise Research Articles

Estimation of the exercise ventilatory compensation point by the analysis of the relationship between minute ventilation and heart rate

Cardiopulmonary exercise test is the gold standard for the identification of the ventilatory compensation point (VCP), an important threshold for exercise training prescription. We hypothesized that changes in the slope of increment in minute ventilation (V'(E)) over heart rate (HR) during incremental exercise can be utilized, as alternative to the ventilatory equivalents method, for VCP detection. In 14 healthy subjects (ten males, four females, age 31 +/- 10 SD) we studied the ventilatory, cardiovascular and gas exchange adaptations during two incremental cycle ergometer exercise: (F) fast work rate increments (30-20 watt/min, M-F), (S) slow work rate increments (15-10 watt/min, M-F). A good between-method agreement in VCP detection in terms of oxygen uptake (V'O(2)) was found in both F and S protocols (F: -7 +/- 118 V'O(2) ml/min; S: -36 +/- 144 V'O(2) ml/min). VCP occurred at the same percentage of peak V'O(2) in both protocols. The changes in the V'(E) versus HR slope during incremental exercise can be used to detect the VCP as alternative to the ventilatory equivalents method.

The effects of patent foramen ovale (PFO) on pulmonary gas exchange during incremental exercise

The prevalence of a probe‐patent foramen ovale (PFO) reported in autopsy studies vary between 20 and 35%. We hypothesized that individuals with a PFO (PFO+) would have greater pulmonary gas exchange inefficiency during exercise than subjects without a PFO (PFO−) because a PFO could act as a right‐to‐left shunt. PFO+ (n=8) and PFO− (n=8) performed two incremental cycle ergometer exercise tests to max, separated by one hour, while breathing either room air or hypoxic gas (FIO2=0.12). Using saline contrast echocardiography, both PFO− and PFO+ demonstrated significant intrapulmonary shunt (bubbles appearing in the left atrium (LA) after 5 heart beats) during both exercise conditions. However, at rest and during both exercise conditions in PFO+, contrast bubbles were also observed traveling through the foramen ovale as small, intermittent boluses entering directly into the LA within 3 heart beats. These findings suggest, qualitatively, a very small intracardiac shunt at rest and during exercise in PFO+. Consequently, the alveolar‐to‐arterial oxygen difference was not significantly different between PFO+ and PFO− at either peak normoxic (24.2 ± 7.8 vs. 17.5 ± 10.8 mm Hg, p= 0.18) or hypoxic (22.7 ± 2.9 vs. 20.2 ± 4.9 mm Hg, p= 0.25) exercise. We conclude that a PFO does not further exacerbate pulmonary gas exchange inefficiency occurring during exercise in healthy humans. Support: HL‐15469 & T32 HL07654; AHA 0550176Z.

Exercise and cardiovascular risk reduction: time to update the rationale for exercise?

although it is generally accepted that the promotion of exercise accords with clinical best practice, the anecdotal experience of many primary care physicians, cardiologists, and exercise physiologists is that, even when exercise prescriptions are adhered to, risk factors often fail to demonstrate

Muscle histopathology and physiology in chronic fatigue syndrome.

Chronic fatigue syndrome (CFS) is characterized by fatigue at rest which is made worse by exercise. Previous biopsy studies on small numbers of CFS patients have shown a range of morphological changes to which have been attributed fatigue and myalgia. We have now studied 108 patients with CFS or muscle pain and 22 normal volunteers by light and electron microscopy. There was no consistent correlation between symptoms and changes in fibre type prevalence, fibre size, degenerative or regenerative features, glycogen depletion, or mitochondrial abnormalities. Physiological contractile properties of quadriceps (maximal isometric force generation, frequency: force characteristics and relaxation rate) were also examined before and for up to 48 hours after a symptom-limited incremental cycle ergometer exercise test in 12 CFS patients and 12 normal volunteers. Voluntary and stimulated force characteristics were normal at rest and during recovery. Exercise duration was similar in the two groups although CFS patients had higher perceived exertion scores in relation to heart rate during exercise, indicating a reduced effort sensation threshold. On physiological and pathological grounds it is clear that CFS is not a myopathy. Psychological/psychiatric factors appear to be of greater importance in this condition.

Możliwości wnioskowania o zdolności wysiłkowej chorych na przewlekłą obturacyjną chorobę płuc na podstawie krzywej maksymalnego przepływu i objętości

Patients with chronic obstructive pulmonary disease (COPD) often present reduced exercise tolerance. Limitation of exercise capacity in COPD is an essential feature, which can be accurately determined by incremental cycle ergometry. The relationship between resting lung function variables and exercise capacity has been studied extensively in COPD patients. A clear relationship between resting pulmonary function testing and exercise capacity has not been established. The present study was designed to assess the accuracy of new index such as area under the maximal expiratory flow-volume curve [A(ex)] in predicting exercise capacity (expressed by maximum oxygen uptake - V'O(2max) and maximal mechanical work - W(max)) in COPD patients. The study was performed on 41 patients with mild - to severe COPD (FEV1, 57.2 +/- 15.3% predicted). Each subject underwent resting spirometry (area under the maximal expiratory flow-volume curve - A(ex) was calculated). Subsequently, they performed maximal incremental cycle ergometer exercise for determination of V'O(2max), W(max). Significant correlation was found between A(ex) and V'O(2max) (r = 0.57, p < 0.001). In the group of severe COPD significant correlation was found between A(ex) and W(max) (r = 0.50 p < 0.05). In chronic obstructive pulmonary disease, the index - area under the maximal expiratory flow-volume curve - A(ex), could be useful in assesment of COPD severity and in predicting exercise capacity.

Favorable Responses to Acute and Chronic Exercise in McArdle Patients

This study reports acute exercise responses in a large (N = 46) series of patients with McArdle disease and responses to exercise training in a smaller (n = 9) set of patients. Patients were studied during both incremental and steady-state cycle ergometer exercise, using cardiopulmonary testing, and the patients were compared with age- and gender-matched controls. The study was performed in a university setting (clinical exercise physiology laboratory). The 46 patients showed common features of McArdle disease. They were definitively diagnosed by histochemistry, biochemistry, and/or molecular genetic analysis. The 46 controls were healthy, sedentary individuals. Nine patients were studied before and after an 8-month supervised aerobic exercise training program (including five weekly sessions of walking and/or cycling exercise with a duration no greater than 60 minutes). The main indicators of exercise capacity that we measured were peak power output, peak oxygen uptake (VO2peak), and ventilatory threshold (VT). Exercise capacity (peak power output, 35% control; VO2peak, 44% control; VT, 66% control) was markedly depressed in the patients. The patients who trained improved peak power output (25%), VO2peak (44%), and VT (27%), with no evidence of negative outcomes from training. Although not achieving normal values, the response to training put the patients into the lower limit of normal controls. Under carefully controlled conditions, patients with McArdle disease may perform acute exercise safely, and they may respond favorably to training. This may offer an additional therapeutic option to help normalize the lifestyles of these patients.

Plasma lactate accumulation is reduced during incremental exercise in untrained women compared with untrained men

The lactate threshold (LT) is commonly reported as not different between sexes, yet lower blood lactate concentrations have been reported in women during submaximal exercise. The purpose of the present study was to measure the changes in plasma lactate concentration [La(-1)] in men and women during incremental cycle ergometer exercise using the same protocol and compare the data using several different methods of analysis. A group of untrained men (n = 21) and women (n = 22) were studied and venous blood drawn at regular intervals during and after exercise for assay of plasma [La(-1)]. Plasma [La(-1)] increased during exercise in both sexes, reaching higher values in men, both at exhaustion (men 8.6 +/- 2.3 mmol l(-1); women 6.2 +/- 2.3 mmol l(-1); P = 0.01) and post-exercise (men 11.8 +/- 2.1 mmol l(-1); women 10.2 +/- 2.4 mmol l(-1); P = 0.03). Logarithmic transformation of the data yielded LT values that were not different between sexes (men 44.2 +/- 12.9; women 50.2 +/- 12.6; %VO2peak; P = 0.45), yet both the 2 and 4 mmol l(-1) fixed concentration LT occurred at lower relative intensities in men (2 mmol l(-1): men 50.9 +/- 12.9; women 66.9 +/- 11.1; %VO2peak; P = 0.01). 4 mmol l(-1): men 75.7 +/- 11.0; women 90.6 +/- 9.2; VO2peak; P = 0.01). However, when the plasma [La(-1)] was examined in both sexes throughout exercise, using a single exponential function, plasma [La(-1)] was significantly lower in women (P < 0.05) at all relative intensities between 30 and 100%VO2peak. While the basis of this sex difference is unknown, reduced plasma [La(-1)] during submaximal exercise in women may offset to some degree the endurance performance disadvantage of their lower VO2peak.

Relationships between Total Energy Expenditure and Both Physical Fitness and Body Fat in Japanese Adolescents: with Special Reference to Regular Sport Activity

It has been reported that the physical fitness of adolescents has been decreasing gradually over the past twenty years in Japan. The reasons for this decrement were a decrease in physical activity and an increase in the prevalence of obesity. However, there is no clear evidence on the relationships between physical activity and physical fitness or body composition for adolescents. The purpose of this study was to measure the total energy expenditure (TEE), physical activity level (PAL) and times spent in light, moderate and vigorous physical activity and to ascertain relationships between physical activity and physical fitness, and body composition for adolescents. Twenty four male adolescents (age: 17.3±1.3) volunteered for participation. Subjects assigned as trained adolescents group (n=16) and untrained group (n=8). TEE was measured by doubly labeled water method and times spent in physical activity were assessed by accelerometer method. VO2max was indirectly measured by breath-by-breath method with stepwise incremental cycle ergometer exercise test. Measurement of physical fitness tests was conducted according to the Ministry of Education, Culture, Sports, Science and Technology. TEE and PAL were significantly higher in trained adolescents (4813±439 kcal/day and 2.64±0.14) than untrained (2859±147 kcal/day and 1.84±0.16), respectively. Times spent in light, moderate and vigorous activities measured from accelerometer were significantly higher in trained adolescents than untrained, while times in sedentary activity were significantly higher in untrained adolescents than trained. PAL and times spent in physical activity (light, moderate, vigorous) were significantly correlated with physical fitness (Vo2max, sit-ups and sitting trunk flexion). Additionally, times spent in moderate related to 20-meter shuttle run. However, PAL and times spent in physical activity were not significantly related to %body fat. These results indicated that daily sport activity results in significant difference of activity energy expenditure between trained and untrained adolescents, and that increase in PAL and times spent in physical activity while engaging in daily sport activity would contribute to improvement of health-related fitness in adolescents.

Absence of Age-Related Increases in the Risk of Lifestyle-Related Diseases in Male Rowers

It is well known that rowing exercise is composed of aerobic and resistance exercises, which enhances muscle function and/or cardiopulmonary fitness. However, there is little information on effects of rowing on risk factors of metabolic syndrome, osteoporosis, and sarcopenia. We hypothesized that increases in their risks and body composition with age are either absent or attenuated in those who perform habitual rowing exercise. PURPOSE: The present cross-sectional study was aimed to determine the relation between habitual rowing, aging, and their risk factors. METHODS: Healthy Japanese men (n=95) aged 19–70 yrs participated in this study, and were either divided by 4 groups; 26 young rowers (YR), 24 senior rowers (SR), 23 sedentary young controls (YC), and 22 senior controls (SC). Total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, glucose, and HbA1c were measured in all subjects. Total and regional lean soft tissue and fat masses and bone mineral density (BMD) were measured using Dual-energy X-ray absorptiometry (DXA). We measured VO2peak during an incremental cycle ergometer exercise in YC and SC, and during increased rowing exercise in YR and SR. RESULTS: The HDL-cholesterol in SR (67.4 ±13.4 mg/dl) was significantly higher than in SC (59.2 ± 11.9 mg/dl, p < 0.05). Furthermore, HDL-cholesterol in SR was equal to in YR (66.1 ±10.8 mg/dl). Arm, leg, and trunk lean soft tissue mass in SR (5.6 ± 0.6 kg, 18.2 ± 1.8 kg, 27.3 ± 3.2 kg, respectively) were significantly higher than in SC (5.1 ±0.4 kg, 16.3 ± 1.4 kg, 24.6 ± 1.7 kg, p < 0.05). BMD in SR were also significantly higher than in SC (in ribs, lumbar spine, and pelvis segments, p < 0.05). VO2peak in SR (35.0 ± 6.5 ml/kg/min) was significantly higher than in SC (29.1 ± 3.1 ml/kg/min, p < 0.05). Handgrip strength in SC (38.9 ± 5.5 kg) was 21% significantly lower in YC (49.9 ± 9.9 kg), however, there was no difference between YR (46.1 ± 7.6 kg) and SR (47.7 ± 6.6 kg) in rowers. CONCLUSIONS:The age-related increases in the risk factors of metabolic syndrome, osteoporosis, and sarcopenia are absent in rowing-trained men. These results suggest that a habitual rowing exercise may favorably influence the prevention of lifestyle-related diseases in middle-aged and old rowers.

Exertional symptoms and exercise capacity in individuals with brain injury

Purpose. To examine factors affecting cycling exercise performance in individuals with acquired brain injury.Methods. Thirty individuals with acquired brain injury and 18 sedentary controls (SC) participated. Heart rate, bicycle power output and rating of perceived exertional (RPE) were recorded, throughout incremental cycle ergometer exercise. The SC group and 18 moderately impaired individuals from the ABI group performed a 25-W (B25) protocol. The remaining 12 individuals performed a 10-W protocol (B10).Results. The B10 group terminated exercise at the lowest RPE, percentage age predicted maximal heart rate (% APMHR) and bicycle power output, followed by the B25 and then the SC group (RPE: Kruskal – Wallis test P < 0.001, %APMHR and bicycle power output: one-way ANOVA P < 0.01). RPE was correlated with %APMHR and percentage of peak bicycle output (B10 group: R2 0.1 to 0.67; B25 group: 0.69 – 0.83; SC group: 0.76 – 0.91). There was no difference in RPE at the same relative work intensity between the B25 and the sedentary control group (P > 0.05). Forward regression analysis revealed fatigue levels were predictive of %APMHR at test termination (β = −0.411, P < 0.05) and quadriceps strength was predictive of peak bicycle power output (β = 0.612, P < 0.05).Conclusions. Individuals with brain injury terminated exercise at lower exercise intensities but rated exertion no differently from healthy individuals. General fatigue levels predicted %APMHR and quadriceps strength predicted peak bicycle power output.

Is Cardiorespiratory Fitness Related to Quality of Life in Survivors of Breast Cancer?

The purpose of this study was to investigate whether indices of cardiorespiratory fitness are related to quality of life (QOL) in women survivors of breast cancer. Using the European Organization for Research and Treatment of Cancer QLQ-30 questionnaire, we assessed the QOL of 16 participants (age, 50 +/- 9 years; body mass, 66.6 +/- 9.6 kg). All participants performed incremental cycle ergometer exercise to determine several indices of cardiorespiratory fitness (e.g., peak oxygen uptake [.V(O2)peak, in L.min(-1), ml.kg(-1).min(-1)]), peak power output (PPO, in W), PPO/ body mass (W.kg(-1), peak heart rate (HRpeak, b.min(-1), peak ventilation (VEpeak), and .V(O2) and heart rate (HR) at the ventilatory (VT) and respiratory compensation (RCT) thresholds. Relationships between QOL and variables were assessed using Spearman rank-difference correlation tests. A significant inverse relationship (p < 0.05) was found for QOL scores and values for age (years) and body mass (kg) ( = -0.53), %HRpeak@VT ( = -0.59) and %VEpeak@VT ( = -0.61). A significant positive relationship (p < 0.05) was found for QOL and PPO/body mass ( = 0.59) and HRpeak ( = 0.78), .V(O2)@RCT (ml.kg(-1.min(-1) ( = 0.51), power output (PO, expressed as either W or W.kg(-1) at RCT, and HR at RCT ( = 0.54). No other significant relationship was found between QOL and variables obtained from the tests. In conclusion, these findings highlight possible relationships between cardiorespiratory fitness and well-being in survivors of breast cancer. From a practical point of view, our data emphasize the need for this population to engage in programmed cardiorespiratory exercise training, mainly designed to improve VT and RCT. The improvement of both submaximal indices can have a beneficial effect on QOL.

β1-Adrenoceptor Mediated Origin of the Heart Rate Performance Curve Deflection

The deflection of the HR performance curve (HRPC) has been described as an objective marker of submaximal exercise performance. HR response to incremental cycle ergometer exercise is shown to be neither linear nor uniform and a physiological explanation of the deflection phenomenon is lacking. We hypothesized that differences in the beta1-adrenoceptor site are the source of these differences. The aim of the study was to investigate the influence of the highly selective beta1-adrenoceptor (beta1-AR) antagonist bisoprolol (Bi) on the HRPC in young healthy male subjects with different HR response patterns. Sixteen subjects were treated in randomized order with Bi or a placebo (Pl) in two separate trials. HR response during incremental cycle ergometer exercise was compared between the two trials. Blood lactate concentration (La) and ventilatory variables were measured throughout both tests. Bi changed the direction of the HRPC more in subjects with a regular, s-shaped response pattern under placebo than those with a nonregular or linear pattern. The influence of Bi on the HR at the second lactate turn point was significantly related (R = 0.78; P < 0.001) to the pattern of the HRPC in Pl conditions. We suggest that differences between the subjects with regular s-shaped versus nonregular HRPC may be due to differences at the beta1-AR site. The origin of the HRPC deflection is mediated in part by the beta1-AR sensitivity.

Heart Rate Performance Curve And Arg389gly ?? 1???adrenoceptor Polymorphism

Differences in ß 1-adrenoceptor (AR) sensitivity were described to explain different response patterns of the Heart Rate Performance Curve (HRPC) (MSSE 33, 2001, 5: S202). PURPOSE The purpose of the study was to investigate if the Arg389Gly ß 1- adrenoceptor polymorphism is related to different patterns of the HRPC. METHODS 164 young healthy male sports students participated in the study. Incremental cycle ergometer exercise (40 W start, 20W/min increase) was performed in all subjects to obtain the heart rate performance (HRPC) and to determine the different HR patterns by means of the degree and the direction of deflection (kHR) of the HRPC. The ß 1-adrenoceptor Arg389Gly polymorphism was determined from venous blood samples according to published standards. ANOVA was calculated to describe differences of kHR between the three genetic variants. RESULTS The number of subjects presenting different variants was 83 (AA), 73 (AG) and 8 (GG). kHR was found at 0.29±0.34 (AA), 0.37±0.36 (AG) and 0.37±0.37 (GG). No significant difference was found for kHR between the different polymorphisms, however a trend to lower values in the AA variant was found. CONCLUSION As previously reported the Arg389Gly ß 1-AR polymorphism had no significant functional relationship with HR response to incremental cycle ergometer exercise in young healthy male subjects.

Heart Rate Performance Curve And Arg389gly ß 1–adrenoceptor Polymorphism

Differences in ß 1-adrenoceptor (AR) sensitivity were described to explain different response patterns of the Heart Rate Performance Curve (HRPC) (MSSE 33, 2001, 5: S202). PURPOSE The purpose of the study was to investigate if the Arg389Gly ß 1- adrenoceptor polymorphism is related to different patterns of the HRPC. METHODS 164 young healthy male sports students participated in the study. Incremental cycle ergometer exercise (40 W start, 20W/min increase) was performed in all subjects to obtain the heart rate performance (HRPC) and to determine the different HR patterns by means of the degree and the direction of deflection (kHR) of the HRPC. The ß 1-adrenoceptor Arg389Gly polymorphism was determined from venous blood samples according to published standards. ANOVA was calculated to describe differences of kHR between the three genetic variants. RESULTS The number of subjects presenting different variants was 83 (AA), 73 (AG) and 8 (GG). kHR was found at 0.29±0.34 (AA), 0.37±0.36 (AG) and 0.37±0.37 (GG). No significant difference was found for kHR between the different polymorphisms, however a trend to lower values in the AA variant was found. CONCLUSION As previously reported the Arg389Gly ß 1-AR polymorphism had no significant functional relationship with HR response to incremental cycle ergometer exercise in young healthy male subjects.

Calculated Target Heart Rate And Objective Markers Of Performance In Cardiac Patients

PURPOSE The aim of this study was to investigate the relationship between objective parameters of sub maximal performance and various calculations of target training heart rate in patients with ischemic heart disease. METHODS Thirty-four patients (age: 62±10 yrs) participated in the study. Each subject performed an incremental cycle ergometer exercise test (initial workload 20 Watt; followed by increments of 10 W/min) until the limit of tolerance and at least two constant load exercise tests for the determination of the maximal lactate steady state (MLSS). The heart rate turn point (HRTP), the second lactate turn point (LTP2) and the respiratory compensation point (RCP) were assessed. Target training heart rate was calculated as a percentage of maximal heart rate (%HRmax), as heart rate reserve (HRR) or combined with age. RESULTS Power output was not significantly different and significantly related between objective markers of sub maximal performance (MLSS: 109±33, HRTP: 113±37, LTP2: 114±37, RCP: 114±38) however calculations of target heart rate revealed significantly different power output. 70% HRR was similar; however, correlation was significantly lower indicating inappropriate target HR in individual cases. CONCLUSIONS Compared to MLSS, intensities measured at the HRTP and LTP2 were valid and superior to other methods of calculated target heart rates.Table

Comparison of forearm blood flow responses to incremental handgrip and cycle ergometer exercise: relative contribution of nitric oxide

The contribution of endothelium-derived nitric oxide (NO) to exercise hyperaemia remains controversial. Disparate findings may, in part, be explained by different shear stress stimuli as a result of different types of exercise. We have directly compared forearm blood flow (FBF) responses to incremental handgrip and cycle ergometer exercise in 14 subjects (age +/-s.e.m.) using a novel software system which calculates conduit artery blood flow continuously across the cardiac cycle by synchronising automated edge-detection and wall tracking of high resolution B-mode arterial ultrasound images and Doppler waveform envelope analysis. Monomethyl arginine (L-NMMA) was infused during repeat bouts of each incremental exercise test to assess the contribution of NO to hyperaemic responses. During handgrip, mean FBF increased with workload (P < 0.01) whereas FBF decreased at lower cycle workloads (P < 0.05), before increasing at 120 W (P < 0.001). Differences in these patterns of mean FBF response to different exercise modalities were due to the influence of retrograde diastolic flow during cycling, which had a relatively larger impact on mean flows at lower workloads. Retrograde diastolic flow was negligible during handgrip. Although mean FBF was lower in response to cycling than handgrip exercise, the impact of L-NMMA was significant during the cycle modality only (P < 0.05), possibly reflecting the importance of an oscillatory antegrade/retrograde flow pattern on shear stress-mediated release of NO from the endothelium. In conclusion, different types of exercise present different haemodynamic stimuli to the endothelium, which may result in differential effects of shear stress on the vasculature.

The Menstrual Cycle or Oral Contraceptive Pill

1911 Substrate utilisation during exercise differs between the oral contraceptive pill (OCP) and normal menstrual cycle (NMC) such that OCP users metabolise fewer carbohydrates and oxidise a greater proportion of fat than women in the luteal phase of the NMC 1. There is, however, an increasing consensus that aerobic capacity is impaired with OCP use 2. PURPOSE: Given that exogenous female steroid hormones seem to reduce aerobic capacity but have the potential to alter energy substrate utilisation compared to endogenous female steroid hormones this study aimed to compare the effects of these hormones during the NMC and OCP, on exercise status in young (18–30 yrs), sedentary women. METHODS: Twenty-three women taking a monophasic OCP and fourteen women with normal menstrual cycles (NMC) performed incremental cycle ergometer exercise to exhaustion and 20 min steadystate exercise at 75% VO2peak. RESULTS: Maximal power output and endurance time to exhaustion were higher in the OCP group. Oxygen uptake (VO2, L·min−1) was significantly higher in the OCP group from 40% − 100% VO2peak (P < 0.05). The OCP group had a higher oxygen pulse (ml·beat−1) and a lower respiratory exchange ratio at all levels of exercise intensity (P < 0.01) in the incremental test. During both exercise tests the OCP group were deriving more energy from lipid (P < 0.01) than the NMC group and there was no difference between the groups in terms of heart rate and rate of perceived exertion. CONCLUSIONS: Exercise status defined by aerobic capacity and endurance performance is increased in young, sedentary women taking an OCP and the results suggest this could be due to a both an improvement in stroke volume and a greater dependence on fat metabolism associated with exogenous steroid hormone administration.

Influence of Venous Emptying on Reactive Hyperemic Blood Flow and Exercise Performance

0179 Recent work by Tschakovsky & Hughson (Am J Physiol Heart Circ Physiol 279: H1007, 2000) indicates that venous emptying serves as a stimulus for vasodilation. This suggests the importance of recognizing the potential Influence of venous function on reactive hyperemic blood flow (RHBF) following occlusion. PURPOSE: To examine the Influence of venous emptying on RHBF. METHODS: Participants underwent an upright incremental cycle ergometer exercise test with gas exchange analysis. Non-dominant forearm in-flow, venous capacitance and outflow were examined in 22 individuals [age = 22±2.34y]. Forearm arterial inflow, venous capacitance, and outflow were obtained two times using strain gauge plethysmography. Forearm blood in flow was estimated at rest and following 5 min of upper arm occlusion. Forearm venous capacitance and outflow were obtained following 5 min of upper arm venous occlusion pressure at 7 mmHg below diastolic blood pressure. Prior to the second measure the arm was passively elevated for 2 minutes. Immediately before returning the arm to its original position the upper arm cuff was again inflated to 240mmHg. Subsequently, RHBF and venous measures were obtained. RESULTS: Average resting in-flow was 2.76±1.15 ml/100ml/min. RHBF was significantly greater following venous emptying (Before: 18.01±4.03; After: 23.6±6.06 ml/100ml/min, p = 0.001). Venous capacitance was also greater (Before: 2.04±0.81; After: 2.90±0.81%, p = 0.001), whereas venous outflow (Before: 36.61±10.86; After: 37.83±12.44 ml/100ml/min, p = 0.18) remained unaffected after venous emptying. Interestingly, venous outflow after emptying was significantly associated with VO2peak (r = 0.78, p = 0.01) as measured on a cycle ergometer. Finally, venous outflow was strongly related to RHBF (r = 0.71, p = 0.01). CONCLUSION: Venous emptying prior to upper arm occlusion results in a significant greater RHBF response and venous capacitance. Moreover, venous outflow was strongly associated with the RHBF response. This suggests the importance of recognizing the Influence of venous outflow on blood inflow. Finally, the strong association between venous outflow and exercise performance warrants further attention.

The Menstrual Cycle or Oral Contraceptive Pill

1911 Substrate utilisation during exercise differs between the oral contraceptive pill (OCP) and normal menstrual cycle (NMC) such that OCP users metabolise fewer carbohydrates and oxidise a greater proportion of fat than women in the luteal phase of the NMC 1. There is, however, an increasing consensus that aerobic capacity is impaired with OCP use 2. PURPOSE: Given that exogenous female steroid hormones seem to reduce aerobic capacity but have the potential to alter energy substrate utilisation compared to endogenous female steroid hormones this study aimed to compare the effects of these hormones during the NMC and OCP, on exercise status in young (18–30 yrs), sedentary women. METHODS: Twenty-three women taking a monophasic OCP and fourteen women with normal menstrual cycles (NMC) performed incremental cycle ergometer exercise to exhaustion and 20 min steadystate exercise at 75% VO2peak. RESULTS: Maximal power output and endurance time to exhaustion were higher in the OCP group. Oxygen uptake (VO2, L·min−1) was significantly higher in the OCP group from 40% − 100% VO2peak (P < 0.05). The OCP group had a higher oxygen pulse (ml·beat−1) and a lower respiratory exchange ratio at all levels of exercise intensity (P < 0.01) in the incremental test. During both exercise tests the OCP group were deriving more energy from lipid (P < 0.01) than the NMC group and there was no difference between the groups in terms of heart rate and rate of perceived exertion. CONCLUSIONS: Exercise status defined by aerobic capacity and endurance performance is increased in young, sedentary women taking an OCP and the results suggest this could be due to a both an improvement in stroke volume and a greater dependence on fat metabolism associated with exogenous steroid hormone administration.

Heart Rate as a Measure of Exercise Testing Early after Acquired Brain Injury

Summary Background The relationship between heart rate and oxygen consumption ( VO 2 ) in individuals with acquired brain injury has been described as being curvilinear; which could lead to under-estimation of exercise intensity when prescribed by heart rate. Purpose This study examines the linearity of the heart rate/oxygen consumption relationship during incremental cycle ergometer exercise in individuals early after brain injury and provides an estimate of the intra-individual reliability of the heart rate response.