Effects of strength training on lactate threshold and endurance performance

To determine the effects of 12 wk of strength training on lactate threshold (LT) and endurance performance, 18 healthy untrained males between 25 and 34 yr of age were randomly assigned to either strength training (N = 10) or control (N = 8) groups. Despite no changes in treadmill VO2max or cycle peak VO2, a 33 +/- 5% increase (P less than 0.001) in cycling time to exhaustion at 75% of peak VO2 was observed following training. No significant changes in cycling time were observed in the control group. There were significant reductions in plasma lactate concentration at all relative exercise intensities ranging between 55 and 75% of peak VO2 training. The improved endurance performance was associated with a 12% increase in LT (r = 0.78, P less than 0.001). The strength training program resulted in significant improvements (P less than 0.001) of 31 +/- 5% and 35 +/- 7% in isokinetic peak torque values for leg extension and flexion, respectively, at a velocity of 30 degrees.s-1. There were also significant increases in 1-RM values of 30 +/- 4% (P less than 0.001) for leg extension, 52 +/- 6% (P less than 0.001) for leg flexion, and 20 +/- 4% (P less than 0.001) for the bench press. These findings indicate that strength training improves cycle endurance performance independently of changes in VO2max. This improved performance appears to be related to increases in LT and leg strength.     

VO2max responses in separate and combined arm and leg air-braked ergometer exercise

Using an air-braked cycle ergometer, we sought to determine the relative contributions of the arms and legs in eliciting the maximal O2 uptake (VO2max). Ten healthy, non-arm-trained males did progressive exercise to exhaustion on the ergometer instrumented to partition the push-pull arm exercise from the cycling leg exercise. Exercise was done with arms only (100% arms), legs only (100% legs, with arms at sides), and in combinations of 10% arms/90% legs, 20% arms/80% legs, and 30% arms/70% legs. To approximate conventional bicycling, four subjects exercised to exhaustion doing leg cycling on the air-braked ergometer with the hands fixed to stationary bars. The maximal power output and VO2max were not significantly different (P greater than 0.05) for the 10% arms/90% legs and the 20% arms/80% legs combinations. Maximal power output and VO2max for 10% arms/90% legs was significantly greater than that for the 100% arms, 100% legs, and 30% arms/70% legs regimens (P less than 0.05). The highest VO2max measured in combined arm/leg exercise for four subjects using 10% arms/90% legs (N = 3) or 20% arms/80% legs (N = 1) was not significantly different from that measured in air-braked ergometer leg cycling with hands fixed to stationary bars (P greater than 0.05). We conclude that push-pull arm exercise of 10 or 20%, combined with leg cycling of 90 or 80%, respectively, or leg cycling with hands fixed to bars optimize the arm/leg contributions in eliciting VO2max. These findings suggest that the upper-body stabilizing effort in conventional cycling (legs cycling, hands fixed) contributes approximately 10-20% to inducing VO2max.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of caffeine on leg muscle pain during cycling exercise among females

PURPOSE: This double-blind, within-subjects experiment examined the effects of ingesting two doses of caffeine on perceptions of leg muscle pain during moderate-intensity cycling exercise among females. METHODS: Low-caffeine-consuming college-aged females (N = 11) ingested one of two doses of caffeine (5 or 10 mg x kg(-1) body weight) or a placebo and 1 h later completed 30 min of cycling on an ergometer at approximately 60% VO2peak. The conditions were completed in a counterbalanced order. Perceptions of leg muscle pain as well as power output, heart rate, systolic blood pressure, and oxygen consumption (VO2) were recorded during exercise. RESULTS: Caffeine had a significant effect on leg muscle pain ratings [F (2,20) = 10.63, P = 0.001, n2 = 0.52]. The mean pain intensity scores during exercise after ingesting 10 mg x kg(-1) body weight caffeine, 5 mg x kg(-1) body weight caffeine, and placebo were 1.6 +/- 1.1, 1.3 +/- 0.7, and 2.4 +/- 1.1, respectively. CONCLUSION: The results support that caffeine ingestion has a large effect on reducing leg muscle pain during exercise among females, but this effect does not appear to be dose-dependent between 5 and 10 mg.kg body weight caffeine.     

Prescribing water-based exercise from treadmill and arm ergometry in cardiac patients.

This study investigated the appropriateness of prescribing upright water-based exercise from treadmill and arm ergometry in uncomplicated, trained patients with cardiovascular disease (CVD) who were accustomed to water-based activities. Ten male patients with established CVD (mean age 59.4 +/- 8.7 yr) underwent maximal treadmill and arm ergometry in randomized counterbalanced order (half of the patients completed the treadmill test first and the other half completed the arm ergometer test first). Electrocardiographic (ECG), rating of perceived exertion (RPE), and oxygen uptake (VO2) measurements were made during both tests. Patients performed upright water-based exercise at 60, 70, and 80% of their maximal treadmill heart rate for 6 min at each intensity in a heated pool with a water temperature of 28-30 degrees C. They also performed an easy tethered swim, defined as performing at a comfortable exercise intensity, eliciting a heart rate of 86% of the treadmill maximum. VO2 and RPE were collected for all water-based exercise. To compare the RPE and VO2 between water-based, treadmill, and arm ergometry exercise, individual regression equations were constructed between heart rate, VO2, and RPE for both treadmill and arm ergometry tests. VO2 and RPE were then compared at the same heart rates between the three exercise modes. At 60% intensity, treadmill exercise exhibited a higher VO2 than water-based and arm ergometry exercise (P less than 0.05) but similar RPE. At 70%, treadmill exercise still yielded higher VO2, but also lower RPE than (P less than 0.05) and arm ergometry exercise (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Accuracy of polar S410 heart rate monitor to estimate energy cost of exercise

PURPOSE: The purpose of this study was to examine the accuracy of the Polar S410 for estimating gross energy expenditure (EE) during exercise when using both predicted and measured VO2max and HRmax versus indirect calorimetry (IC). METHODS: Ten males and 10 females initially had their VO2max and HRmax predicted by the S410, and then performed a maximal treadmill test to determine their actual values. The participants then performed three submaximal exercise tests at RPE of 3, 5, and 7 on a treadmill, cycle, and rowing ergometer for a total of nine submaximal bouts. For all submaximal testing, the participant had two S410 heart rate monitors simultaneously collecting data: one heart rate monitor (PHRM) utilized their predicted VO2max and HRmax, and one heart rate monitor (AHRM) used their actual values. Simultaneously, EE was measured by IC. RESULTS: In males, there were no differences in EE among the mean values for the AHRM, PHRM, and IC for any exercise mode (P > 0.05). In females, the PHRM significantly overestimated mean EE on the treadmill (by 2.4 kcal x min(-1)), cycle (by 2.9 kcal x min(-1)), and rower (by 1.9 kcal x min(-1)) (all P < 0.05). The AHRM for females significantly improved the estimation of mean EE for all exercise modes, but it still overestimated mean EE on the treadmill (by 0.6 kcal x min(-1)) and cycle (by 1.2 kcal x min(-1)) (P < 0.05). CONCLUSION: When the predicted values of VO2max and HRmax are used, the Polar S410 HRM provides a rough estimate of EE during running, rowing, and cycling. Using the actual values for VO2max and HRmax reduced the individual error scores for both genders, but in females the mean EE was still overestimated by 12%.     

Aerobic fitness does not contribute to prediction of orthostatic intolerance

Several investigations have suggested that orthostatic tolerance may be inversely related to aerobic fitness (VO2max). To test this hypothesis, 18 males (age 29 to 51 yr) underwent both treadmill VO2max determination and graded lower body negative pressures (LBNP) exposure to tolerance. VO2max was measured during the last minute of a Bruce treadmill protocol. LBNP was terminated based on pre-syncopal symptoms, and LBNP tolerance (peak LBNP) was expressed as the cumulative product of LBNP and time (torr-min). Changes in heart rate, stroke volume, cardiac output, blood pressure, and impedance rheographic indices of mid-thigh-leg fluid accumulation were measured at rest and during the final minute of LBNP. For all 18 subjects, mean (+/- SE) fluid accumulation index and leg venous compliance index at peak LBNP were 139 +/- 22 ml and 3.9 +/- 0.4 ml . 100 ml . torr-min-2 x 10(3), respectively. Pearson product-moment correlations and step-wise linear regression were used to investigate relationships with peak LBNP. Variables associated with endurance training, such as VO2max and percent body fat, were not found to correlate significantly (P less than 0.05) with peak LBNP and did not add sufficiently to the prediction of peak LBNP to be included in the step-wise regression model. The step-wise regression model included only fluid accumulation index, leg venous compliance index, and blood volume, and resulted in a squared multiple correlation coefficient of 0.978. These data do not support the hypothesis that orthostatic tolerance as measured by LBNP is lower in individuals with high aerobic fitness.     

Physiological and biomechanical factors associated with elite endurance cycling performance

In this study we evaluated the physiological and biomechanical responses of "elite-national class" (i.e., group 1; N = 9) and "good-state class" (i.e., group 2; N = 6) cyclists while they simulated a 40 km time-trial in the laboratory by cycling on an ergometer for 1 h at their highest power output. Actual road racing 40 km time-trial performance was highly correlated with average absolute power during the 1 h laboratory performance test (r = -0.88; P less than 0.001). In turn, 1 h power output was related to each cyclists' VO2 at the blood lactate threshold (r = 0.93; P less than 0.001). Group 1 was not different from group 2 regarding VO2max (approximately 70 ml.kg-1.min-1 and 5.01 l.min-1) or lean body weight. However, group 1 bicycled 40 km on the road 10% faster than group 2 (P less than 0.05; 54 vs 60 min). Additionally, group 1 was able to generate 11% more power during the 1 h performance test than group 2 (P less than 0.05), and they averaged 90 +/- 1% VO2max compared with 86 +/- 2% VO2max in group 2 (P = 0.06). The higher performance power output of group 1 was produced primarily by generating higher peak torques about the center of the crank by applying larger vertical forces to the crank arm during the cycling downstroke. Compared with group 2, group 1 also produced higher peak torques and vertical forces during the downstroke even when cycling at the same absolute work rate as group 2. Factors possibly contributing to the ability of group 1 to produce higher "downstroke power" are a greater percentage of Type I muscle fibers (P less than 0.05) and a 23% greater (P less than 0.05) muscle capillary density compared with group 2. We have also observed a strong relationship between years of endurance training and percent Type I muscle fibers (r = 0.75; P less than 0.001). It appears that "elite-national class" cyclists have the ability to generate higher "downstroke power", possibly as a result of muscular adaptations stimulated by more years of endurance training.     

Potential benefits of maximal exercise just prior to return from weightlessness

The purpose of this study was to determine whether performance of a single maximal bout of exercise during weightlessness within hours of return to earth would enhance recovery of aerobic fitness and physical work capacities under a 1G environment. Ten healthy men (36-51 yr) underwent maximal supine exercise followed by upright maximal exercise before and after a 10-d bedrest period in the 6 degrees headdown position. A graded maximal supine cycle ergometer test was performed before and at the end of bedrest to simulate exercise during weightlessness. Following 3 h of resumption of the upright posture from the supine exercise test, a second maximal exercise test was performed on a treadmill to measure work capacity under conditions of 1G. Compared to before bedrest, peak VO2 decreased (p less than 0.05) by 8.7% and peak HR increased (p less than 0.05) by 5.6% in the supine cycle test at the end of bedrest. However, there were no significant changes in peak VO2 and peak HR in the upright treadmill test following bedrest. These data, based on a simulation, suggest that one bout of maximal leg exercise prior to return from 10 d of weightlessness may be adequate to restore preflight aerobic fitness and physical work capacity.     

Haemoglobin saturation during incremental arm and leg exercise.

There are few reports concerning the alterations in the percent of haemoglobin saturated with oxygen (%SO2) during non-steady state incremental exercise. Further, no data exist to describe the %SO2 changes during arm exercise. Therefore, the purpose of this study was made to assess the dynamic changes in %SO2 during incremental arm and leg work. Nine trained subjects (7 males and 2 females) performed incremental arm and leg exercise to exhaustion on an arm crank ergometer and a cycle ergometer, respectively. Ventilation and gas exchange measurements were obtained minute by minute via open circuit spirometry and changes in %SO2 were recorded via an ear oximeter. No significant difference (p greater than 0.05) existed between arm and leg work in end-tidal oxygen (PETO2), end-tidal carbon dioxide (PETCO2), or %SO2 when compared as a function of percent VO2 max. These results provide evidence that arterial O2 desaturation occurs in a similar fashion in both incremental arm and leg work with the greatest changes in %SO2 occurring at work rates greater than 70% VO2 max.     

RPE, blood glucose, and carbohydrate oxidation during exercise: effects of glucose feedings

This study examined the effects of glucose ingestion on differentiated and undifferentiated ratings of perceived exertion (RPE) during prolonged cycling exercise. On two occasions, seven trained males cycled for 180 min on a Monark cycle ergometer at 70% peak VO2 (VO2peak). Subjects consumed an 8% glucose/electrolyte drink (G) or a flavored water placebo (P) every 15 min throughout exercise. Measurement of RPE, ventilation (VE), oxygen uptake (VO2), respiration rate (RR), respiratory exchange ratio (RER), heart rate (HR), and venous blood sample collection preceded ingestion of the drink. Subjects were homogenous with respect to height, weight, and VO2peak. RPE for the legs and overall body were significantly attenuated (P less than 0.05) during the last 45 min of exercise. Plasma glucose and insulin were higher (P less than 0.05) in G than in P at virtually all time points. CHO oxidation and work rate were maintained throughout exercise in G but not during the last 30 min of exercise in P (P less than 0.05). Percent changes in plasma volume, plasma lactate, HR, VE, RR, and RPE for the chest were not different between conditions (P greater than 0.05). The data suggest that ingestion of carbohydrate beverages during endurance cycling can maintain plasma glucose and CHO oxidation during the latter stages of prolonged exercise. As a result, it appears that a relationship exists between attenuation of ratings of perceived exertion (especially in the legs), blood glucose, and CHO oxidation late in prolonged exercise. The mechanism for this probably involves the increased availability of blood-borne glucose to serve as substrate for brain and/or muscle energy metabolism during a time when endogenous stores of carbohydrate are low.     

Cardio-respiratory responses to rowing ergometry and treadmill exercise soon after myocardial infarction

PURPOSE: The aim of this study was to compare the cardio-respiratory differences between rowing ergometry and treadmill exercise in beta-blocked men participating in exercise rehabilitation soon after myocardial infarction (postMI). METHODS: Eleven males all receiving beta-blockade medication were measured for oxygen consumption (VO2), respiratory exchange ratio (RER), and rating of perceived exertion (RPE) at individualized submaximal exercise target heart rates (THR) during 6 min of exercise on each of a motorized treadmill and a rowing ergometer 2-6 wk (4.9 +/- 1.4) postMI. RESULTS: The mean THR of the group, predetermined from an exercise ECG stress test, was 107 +/- 16 beats x min(-1). No significant difference was found between rowing versus treadmill VO2 (19.4 +/- 3.2 vs 19.7 +/- 4.2 mL x kg(-1) x min(-1); P = 0.53) or RPE (12.6 +/- 1 vs 12.7 +/- 1; P = 0.72). RER was significantly greater (P = 0.02) during rowing (0.99 +/- 0.07) compared with treadmill exercise (0.94 +/- 0.07). CONCLUSION: Exercising at a specified submaximal THR during rowing versus treadmill exercise in beta-blocked men participating in very early cardiac rehabilitation represents the same VO2 and RPE. A significantly greater RER was, however, apparent during rowing compared with treadmill exercise; thus, agreement was shown with previous studies on healthy individuals where rowing ergometry was less metabolically efficient than treadmill exercise. The results suggest that establishing a THR from a standard treadmill stress test soon after MI is not only suitable for walking/treadmill exercise but also in setting exercise intensity for rowing ergometry.     

Radionuclide ejection fraction: comparison of response to treadmill and bicycle exercise

Most exercise radionuclide studies utilise the supine bicycle ergometer during imaging, although exercise on a treadmill results in greater cardiovascular stress. Twenty-three patients were studied to compare the radionuclide left ventricular ejection fraction (LVEF) estimated immediately following treadmill exercise with that obtained at peak supine bicycle exercise in patients with coronary artery disease (CAD) and patients with normal coronary arteries. In 14 patients with CAD the rest LVEF was 47 +/- 7% (mean +/- SD) by first pass and 49 +/- 10% by equilibrium blood pool techniques. Immediately following maximum treadmill exercise, 13 of the 14 patients with coronary artery disease showed either no change or a decrease in LVEF, the LVEF was 49 +/- 7% (P = NS) and 47 +/- 8% (P = NS) by first pass and equilibrium determinations respectively. In comparison the LVEF during peak supine bicycle exercise decreased significantly to 42 +/- 12% (P less than 0.01). In nine patients with angiographically normal coronary arteries the rest LVEF was 51 +/- 4% by first pass and 54 +/- 6% by equilibrium, increasing to 67 +/- 7% (P less than 0.01) and 64 +/- 7% (P less than 0.01) respectively following treadmill exercise. During peak bicycle exercise LVEF increased in the normal patients to 61 +/- 7% (P less than 0.05). These data suggest that quantitative radionuclide angiography following either maximum treadmill exercise or during peak bicycle exercise can discriminate between patients with coronary artery disease and normal subjects, although the magnitude of left ventricular functional changes are greater during bicycle stress.     

Leg blood flow and VO2 during peak cycle exercise in younger and older women

PURPOSE: To test the hypothesis that leg blood flow and leg O2 extraction during peak exercise are reduced with age in healthy normally active women. METHODS: Thirteen younger (20-27 yr) and 12 older (60-71 yr) nonendurance trained women performed graded upright leg cycling to maximum exertion (VO2peak), while leg blood flow (femoral vein thermodilution), cardiac output (acetylene rebreathing), mean arterial pressure (MAP, radial artery), and blood O2 contents were measured. RESULTS: Peak leg VO2 was 32% lower in the older versus younger women (0.81 +/- 0.06 vs 1.18 +/- 0.10 L x min(-1)) and was correlated with peak systemic VO2 (1.33 +/- 0.1 vs 1.78 +/- 0.1 L x min(-1)) in both groups. Peak leg blood flow and estimated leg vascular conductance were 29% and 38% lower, respectively, in the older women (both P < 0.001). Peak leg blood flow and peak estimated cardiac output were correlated in the older (r2 = 0.51, P = 0.02), but not younger (r2 = 0.10, P = 0.35), group. Estimates of peak systemic and leg arterial-venous O2 difference did not differ between groups (both P > 0.28). CONCLUSIONS: Reduced leg blood flow is a major contributor to the reduced peak systemic VO2 observed in older nonendurance trained women. Diminished leg blood flow during peak exercise in older women, in turn, is due to both central (reduced cardiac output) and peripheral (reduced leg vascular conductance) limitations.     

Effects of pseudoephedrine on maximal cycling power and submaximal cycling efficiency

PURPOSE: To study the effects of a therapeutic dose of pseudoephedrine on anaerobic cycling power and aerobic cycling efficiency. METHODS: Eleven healthy moderately trained males (VO (2peak) 4.4 +/- 0.8 L x min(-1) participated in a double-blinded crossover design. Subjects underwent baseline (B) tests for anaerobic (Wingate test) and aerobic (VO (2peak) test) cycling power. Subjects ingested either 60 mg of pseudoephedrine hydrochloride (D) or a placebo (P) and, after 90 min of rest, a Wingate and a cycling efficiency test were performed. During the cycling efficiency test, heart rate (HR) and VO(2) were averaged for the last 5 min of a 10-min cycle at 40% and 60% of the peak power achieved during the VO (2peak) test. RESULTS: There were no significant differences in peak power (B = 860 +/- 154, D = 926 +/- 124, P = 908 +/- 118 W), total work (B = 20 +/- 3, D = 21 +/- 3, P = 21 +/- 3 kJ), or fatigue index (B = 39 +/- 8, D = 45 +/- 5, P = 43 +/- 5%). There were no significant differences in HR at 40% power (D = 138 +/- 10, P = 137 +/- 10 beats.min-1) or 60% power (D = 161 +/- 11, P = 160 +/- 11 beats x min(-1). There were no significant differences in cycling efficiency at 40% power (D = 18.8 +/- 1.8, P = 18.5 +/- 1.8%) or 60% power (D = 20.3 +/- 2.0, P = 20.1 +/- 2.1%). CONCLUSION: A therapeutic dose of pseudoephedrine hydrochloride does not affect anaerobic cycling performance or aerobic cycling efficiency.     

A comparison of energy expenditure during rowing and cycling ergometry

Metabolic and cardiorespiratory responses of healthy adults were compared at similar incremental power outputs during a variable-resistance rowing exercise and a fixed-resistance cycle ergometer exercise. Repeated measurements of power (watts), VEBTPS, VO2 STPD, and HR were obtained on 60 men and 47 women ranging in age from 20 to 74 yr. Average maximal power output for the men was significantly higher (P less than 0.05) for cycling than rowing: 207 +/- 5.2 W vs 195 +/- 58 W (mean +/- SE). A similar difference was also observed for women favoring cycling: 135 +/- 4.1 W vs 126 +/- 4.9 W (mean +/- SE). VEBTPS, VO2 STPD, and HR were significantly higher at all power increments during the rowing graded exercise test (RGXT) when compared with the same exercise intensity during the cycle graded exercise test (CGXT). Consistent linearity was found between VEBTPS and VO2 STPD and between HR and VO2 STPD for both exercises. The linear relationship between VEBTPS and VO2 STPD for men during RGXT was r = 0.976, P less than 0.001, slope = 44.6 +/- 1.03, and for women during RGXT it was r = 0.990, P less than 0.001, slope = 19.6 +/- 0.36. The relationship between HR and VO2 STPD for men during rowing was r = 0.989, P less than 0.001, slope = 29.1 +/- 0.76, and for women during rowing it was r = 0.971, P less than 0.001, slope = 35.7 +/- 0.89. The linear relationship between VEBTPS and VO2 STPD for men during CGXT was r = 0.991, P less than 0.001, slope = 31.1 +/- 0.98, and for women it was r = 0.959, P less than 0.991, slope = 29.6 +/- 0.87. The relationship between HR and VO2 STPD for men during CGXT was r = 0.997, P less than 0.001, slope = 28.1 +/- 0.83, and for women it was r = 0.990, R less than 0.001, slope = 35.9 +/- 0.96. Results indicated that energy costs for rowing ergometry was significantly higher than cycle ergometry at all comparative power outputs including maximum levels. It was concluded that rowing ergometry could be an effective alternative activity for physical fitness and exercise rehabilitation programs.     

Effects of resistance training on H+ regulation, buffer capacity, and repeated sprints

PURPOSE: We investigated the effects of resistance training on muscle buffer capacity, H regulation, and repeated-sprint ability (RSA). METHODS: Sixteen recreationally active females performed a graded exercise test to determine VO2peak and the lactate threshold (LT), a repeated-sprint test (5 x 6 s, every 30 s) to determine RSA, and a 60-s high-intensity exercise test based on their pretraining RSA score (CIT60; continuous cycling at approximately 160% VO2peak). Muscle biopsies (vastus lateralis) were sampled before and immediately after CIT60. Subjects were then randomly assigned to either a high-repetition (three to five sets of 15-20 reps) short-rest (20 s) resistance-training group or to a control group. RESULTS: Training did not result in significant improvements in VO2peak (P > 0.05) but did improve the LT, leg strength, and RSA (P < 0.05). There were no significant improvements in muscle buffer capacity after training (P > 0.05); however, there was a significant reduction in H in the muscle and blood after high-intensity exercise (CIT60) (P < 0.05), CONCLUSIONS: High-repetition, short-rest, resistance training does not improve muscle buffer capacity in active females, but it does reduce H accumulation during high-intensity exercise (approximately 160% VO2peak). It is likely that increases in strength, LT, and ion regulation contributed to the improved RSA.     

Effect of hypervolemia on heart rate during 4 days of prolonged exercises

The aim was to evaluate the cardiodynamic adjustment during 4 days of prolonged exercises and to check if the plasma volume (PV) expansion which is observed generally during such events plays a role in this adaptation. Thirteen subjects exercised 5 hours per day on a cycle ergometer alternately with a treadmill for 4 days (D1 to D4) (6 x 50 min sessions per day). The individual cycle ergometer load and the treadmill speed were unchanged during each exercise session and throughout all the sessions, and corresponded to a moderate exercise intensity: 58 - 63 % of peak oxygen uptake (VO (2)peak). Heart rate (HR) was recorded every 15 s during each exercise session and VO (2) was measured from the expired air at the beginning and the end of each exercise session. Relative PV changes were measured from haematocrit and haemoglobin changes in the morning before the exercise bouts. No significant changes of VO (2) were observed between the first and the last exercise session i. e. for cycling: 2.1 +/- 0.2 l/min and for running: 2.4 +/- 0.3 l/min. Between the first and the last day, HR decreased from 143 to 129 bpm for cycle (p < 0.0001) and from 147 to 137 bpm (p = 0.01) for treadmill. As compared to D1, PV increased gradually from D2 (+ 1.8 % +/- 4.7 %) to D4 (+ 8.5 % +/- 4.7 %). The individual PV increases were significantly correlated with cycling HR decreases from D1 to D4 (r (2) = 0.40, p = 0.02). In conclusion, the 4 days' prolonged exercise induced a HR decrease during submaximal exercise without VO (2) drift. Here we suggested that this HR decline could be in part linked to the transient PV expansion.     

Effect of acute hypoxia on maximal oxygen uptake and maximal performance during leg and upper-body exercise in Nordic combined skiers

We examined the effect of normobaric hypoxia (3200 m) on maximal oxygen uptake (VO2max) and maximal power output (Pmax) during leg and upper-body exercise to identify functional and structural correlates of the variability in the decrement of VO2max (DeltaVO2max) and of maximal power output (DeltaPmax). Seven well trained male Nordic combined skiers performed incremental exercise tests to exhaustion on a cycle ergometer (leg exercise) and on a custom built doublepoling ergometer for cross-country skiing (upper-body exercise). Tests were carried out in normoxia (560 m) and normobaric hypoxia (3200 m); biopsies were taken from m. deltoideus. DeltaVO2max was not significantly different between leg (-9.1+/-4.9%) and upper-body exercise (-7.9+/-5.8%). By contrast, Pmax was significantly more reduced during leg exercise (-17.3+/-3.3%) than during upper-body exercise (-9.6+/-6.4%, p<0.05). Correlation analysis did not reveal any significant relationship between leg and upper-body exercise neither for DeltaVO2max nor for DeltaPmax. Furthermore, no relationship was observed between individual DeltaVO2max and DeltaPmax. Analysis of structural data of m. deltoideus revealed a significant correlation between capillary density and DeltaPmax (R=-0.80, p=0.03), as well as between volume density of mitochondria and DeltaPmax (R=-0.75, p=0.05). In conclusion, it seems that VO2max and Pmax are differently affected by hypoxia. The ability to tolerate hypoxia is a characteristic of the individual depending in part on the exercise mode. We present evidence that athletes with a high capillarity and a high muscular oxidative capacity are more sensitive to hypoxia.     

Dietary regimen and performance of high intensity ergometer exercise.

The influence of preceding diet (mixed, MD; carbohydrate CD; protein PD) on performance during high intensity endurance cycling was examined in six middle distance runners. Subjects undertook cycle ergometer exercise at a workload equivalent to 80% VO2 max until exhaustion following each of the three dietary regimens. Dietary analyses were performed using a computerised evaluation technique and cardiorespiratory, blood glucose and lactate responses to exercise were measured along with exercise time to exhaustion. Significant differences in carbohydrate and protein intakes were noted between respective diets as well as significantly higher total energy intake in MD (P less than 0.05). A significant relationship was observed between carbohydrate intake and exercise time to exhaustion (r = 0.59, P less than 0.05). No significant differences were noted in cardiorespiratory measures or blood glucose response after exhaustive exercise between the three dietary regimens but peak blood lactate concentration was lower following PD (P less than 0.05). Total time to exhaustion was significantly higher on CD (1070.0 +/- 106.7 s) than on PD (642.5 +/- 84.3 s, P less than 0.01). Performance time on MD (895.7 +/- 84.3 s) did not differ significantly for performance time on either CD or PD. It was concluded that dietary manipulation significantly improves exercise time to exhaustion during short term, high intensity cycling.     

Regional rates of sweat evaporation during leg and arm cycling

The rate of sweat evaporation from the arm, chest, back and thigh, aural temperature, skin temperature (arm, chest, back and thigh), heat production (derived from measurements of respiratory gas exchange) and heart rate were measured in 7 men during 15 minutes of leg or arm cycling at 32% of predicted maximum oxygen uptake (VO2 max). The regional sweat evaporation rates and changes in body temperature were similar during both forms of exercise. The peak rates of sweat evaporation from the arm, chest, back and thigh were 15.7 +/- 19.8, 25.0 +/- 21.6, 28.7 +/- 22.7 and 21.0 +/- 18.2 mg.cm-2 hr-1 during leg cycling and 13.2 +/- 11.6, 22.2 +/- 14.4, 27.6 +/- 14.7 and 19.2 +/- 13.3 (SD) mg.cm-2 hr-1 respectively during arm cycling. The sweat evaporation rates from the different body regions were not significantly different from one another.