Physiological responses to indoor rock-climbing and their relationship to maximal cycle ergometry

PURPOSE: To quantify the cardiorespiratory responses to indoor climbing during two increasingly difficult climbs and relate them to whole-body dynamic exercise. It was hypothesized that as climbing difficulty increased, oxygen consumption ([V02] and heart rate would increase, and that climbing would require utilization of a significant fraction of maximal cycling values. METHODS: Elite competitive sport rock climbers (6 male, 3 female) completed two data collection sessions. The first session was completed at an indoor climbing facility, and the second session was an incremental cycle test to exhaustion. During indoor climbing subjects were randomly assigned to climb two routes designated as "harder" or "easier" based on their previous best climb. Subjects wore a portable metabolic system, which allowed measurement of oxygen consumption [V02], minute ventilation ([V02]E), respiratory exchange ratio (RER), and heart rate. During the second session, maximal values for [V02], [V02]E, RER, and heart rate were determined during an incremental cycle test to exhaustion. RESULTS: Heart rate and [VO2], expressed as percent of cycling maximum, were significantly higher during harder climbing compared with easier climbing. During harder climbing, %HR(max) was significantly higher than %[V02] (2max) (89.6% vs 51.2%), and during easier climbing, %HR(max) was significantly higher than %[V02] (2max) (66.9% vs 45.3%). CONCLUSIONS: With increasing levels of climbing difficulty, there is a rise in both heart rate and [V02]. However, there is a disproportional rise in heart rate compared with [V02], which we attribute to the fact that climbing requires the use of intermittent isometric contractions of the arm musculature and the reliance of both anaerobic and aerobic metabolism.     

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

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

The effect of training specificity on maximal and submaximal physiological responses to treadmill and cycle ergometry

The purpose of this study was to investigate the effect of training specificity during maximal and submaximal treadmill (TM) and bicycle ergometer (BE) exercise. A group of trained runners (RG, no. 7) and trained bikers (BG, no. 7) underwent graded exercise testing on both TM and BE, utilizing the same testing protocol within each exercise mode for both groups. Data for VO2 HR and BP were collected during each 3 min stage. Group by trial ANOVAs followed by Tukey's post hoc analysis, showed no group difference in VO2max, HRmax or BPmax during TM exercise. However, during each of the first four submaximal 3 min stages, VO2 and HR were significantly less (p less than .05) in RG vs BC, with no significant difference in BP. During BE exercise, VO2max was significantly less for both groups compared with TM (RG-59.6 vs 50.1 ml.kg-1.min-1 BS-59.4 vs 55.1 ml.kg-1.min-1) (p less than .05), with BG exhibiting the greater BEmax (p less than .05). RG also had a reduced HRmax during BE exercise (p less than .05). Both groups showed greater BPmax during BE vs TM exercise (p less than .05). Although submaximal VO2 was slightly less during BE for each stage in RG than BG, these differences were not significant as measured either by ml.kg-1.min-1 or l.min-1. Both submaximal HR and BP mirrored the VO2 response, with no significant differences between RG and BG. These data agree with previous studies, showing a greater effect of training specificity during maximal BE than during maximal TM exercise. However, during submaximal exercise, training specificity appear to have a greater effect during TM than BE exercise.     

Force-velocity and power-velocity relationships during maximal short-term rowing ergometry

INTRODUCTION: Maximal rowing power-velocity relationships that exhibit ascending and descending limbs and a local maximum have not been reported. Further, duty cycle (portion of the stroke occupied by the pull phase) is unconstrained during rowing and is known to influence average muscular power output. PURPOSE: Our purposes for conducting this study were to fully describe maximal short-term rowing force-velocity and power-velocity relationships. Within the context of those purposes, we also aimed to determine the apex of the power-velocity relationship and the influence of freely chosen duty cycle on stroke power. METHODS: Collegiate varsity male rowers (N = 11, 22.9 +/- 2.3 yr, 84.1 + 12.1 kg, 184 +/- 7 cm) performed five maximal rowing trials using an inertial load ergometer. For each stroke, we determined force and power averaged for the pull phase and the complete stroke, instantaneous peak force and power, average handle velocity for the pull phase, handle velocity at peak instantaneous force and power, pull time, recovery time, and freely chosen duty cycle. Force-velocity and power-velocity relationships were characterized using regression analyses, and optimal velocities were determined from the regression coefficients. RESULTS: Pull force-velocity (r2 = 0.99) and peak instantaneous force-velocity (r2 = 0.93) relationships were linear. Stroke power (r2 = 0.98), pull power (r2 = 0.99), and instantaneous peak power (r2 = 0.99) were quadratic, with apexes at 2.04, 3.25, and 3.43 m x s(-1), respectively. Maximum power values were 812 +/- 28 W (9.8 +/- 0.4 W x kg(-1)), 1995 +/- 67 W (23.9 +/- 0.7 W x kg(-1)), and 3481 +/- 112 W (41.9 +/- 1.3 W x kg(-1)) for stroke, pull, and instantaneous power, respectively. Freely chosen duty cycle decreased from 58 +/- 1% on the first stroke to 26 +/- 1% on the fifth stroke. CONCLUSIONS: These data characterized the maximal rowing force-velocity and power-velocity relationships and identified the optimal velocity for producing maximal rowing power. Differences in maximum pull and stroke power emphasized the importance of duty cycle.     

Plasma beta-endorphin immunoreactivity during graded cycle ergometry

The present study was undertaken to define the response of plasma beta-endorphin immunoreactivity (ir-BE) to exercise of increasing intensity. Nineteen healthy males performed continuous exercise for 32 min on a cycle ergometer, comprised of 8-min bouts at %VO2max approximating 25, 50, and 75% of maximal exercise. Venous blood samples were collected before exercise (T = -20 and 0 min), during exercise (T = 8, 16, 24, and 32 min), and in recovery (T = +15, +30 min). Ir-BE in plasma was measured by radioimmunoassay using Immuno Nuclear assay kits. Plasma ir-BE level (pg X ml-1) was not altered from pre-exercise (18.3 +/- 1.3) after 8 min of exercise at 25 and 50% VO2max intensity; however, ir-BE rose significantly after 8 min of 75% VO2max work intensity (27.1 +/- 2.4) and was further elevated at maximal exercise (74.1 +/- 8.6). Ir-BE level remained elevated 15 min (60.9 +/- 8.1) and 30 min (35.2 +/- 5.2) post-exercise. The response pattern was further characterized by a significant (P less than 0.05) inter-individual variation, both at rest and during exercise; also, regression analysis indicated the ir-Be levels attained at maximal exercise were inversely related to the relative VO2max (ml X kg-1 X min-1) of the subject (predicted ir-BE = 248.2 - 3.39 VO2max; r = -0.397, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Optimal pedalling rate in prolonged bouts of cycle ergometry

This study was designed to investigate the variables which contribute to the determination of optimal pedalling rate in cycling. Five trained bicycle racers were used as subjects for the study. The experiment consisted of five 20- to 30-min tests at about 85% of each subject's pre-determined VO2max. Pedal rates of 40, 60, 80, 100, and 120 rpm were used. In the experiment, efficiency, heart rate, and perceived exertion measures were obtained at 10 and 20 min of exercise. Blood lactate concentration and plasma levels of epinephrine and norepinephrine were measured at rest, during the exercise sampling periods, and at 5 min of recovery following the exercise bout. When compared across pedal rates, gross efficiency, heart rate, and perceived exertion all were minimal at 60 or 80 rpm for each sampling period. Blood lactate showed the same relationship to pedal rate as the preceding variables at 10 min of exercise but not late in the test. The catecholamine values appeared to follow a similar trend but not significantly. The experiment showed that for this group of cyclists an optimal pedal rate existed for a prolonged period of exercise and was evident in measures of both efficiency and perceived exertion. The experiment indicates that, for researchers and for cyclists who use high power outputs, the choice of pedal rate is an important one.     

Accurate prediction of VO2max in cycle ergometry

Numerous equations exist for predicting VO2max from the duration (an analog of maximal work rate, Wmax) of a treadmill graded exercise test (GXT). Since a similar equation for cycle ergometry (CE) was not available, we saw the need to develop such an equation, hypothesizing that CE VO2max could be accurately predicted due to its more direct relationship with W. Thus, healthy, sedentary males (N = 115) and females (N = 116), aged 20-70 yr, were given a 15 W.min-1 CE GXT. The following multiple linear regression equations which predict VO2max (ml.min-1) from the independent variables of Wmax (W), body weight (kg), and age (yr) were derived from our subjects: Males: Y = 10.51 (W) + 6.35 (kg) - 10.49 (yr) + 519.3 ml.min-1; R = 0.939, SEE = 212 ml.min-1. Females: Y = 9.39 (W) + 7.7 (kg) - 5.88 (yr) + 136.7 ml.min-1; R = 0.932, SEE = 147 ml.min-1 Using the 95% confidence limits as examples of worst case errors, our equations predict VO2max to within 10% of its true value. Internal (double cross-validation) and external cross-validation analyses yielded r values ranging between 0.920 and 0.950 for the male and female regression equations. These results indicate that use of the equations generated in this study for a 15 W.min-1 CE GXT provides accurate estimates of VO2max.     

The relationship between total-body mass, fat-free mass and cycle ergometry power components during 20 seconds of maximal exercise.

The purpose of this study was to compare the maximal exercise performance of 10 men during friction braked cycle ergometry of 20 s duration when resistive forces reflected total body mass (TBM) or fat free mass (FFM). Fat mass was calculated from the sum of skinfold thicknesses. Increases (P < 0.05) in peak power output (PPO) were found between TBM and FFM (1,015+/-165 W TBM vs 1,099+/-172 W FFM). Decreases (P < 0.05) were observed for the time taken to reach PPO (3.8+/-1.4 s TBM vs 2.9+/-1 s FFM). Pedal velocity increased (P < 0.05) during the FFM protocol (129.4+/-8.2 rpm TBM vs 136.3+/-8 rpm FFM). Rating of perceived exertion (RPE) was also (P < 0.05) greater for FFM (18.4+/-1.6 TBM vs 19.8+/-0.4 FFM). No changes were found for Mean Power Output (MPO), fatigue index (FI) or Work Done (WD) between trials. These findings suggest that high intensity resistive force loading protocols may need to be reconsidered. Results from this study indicate that the active tissue component of body composition needs consideration in resistive force selection when ascertaining maximal cycle ergometer power profiles.     

Cadence, power, and muscle activation in cycle ergometry

PURPOSE: Based on the resistance-rpm relationship for cycling, which is not unlike the force-velocity relationship of muscle, it is hypothesized that the cadence which requires the minimal muscle activation will be progressively higher as power output increases. METHODS: To test this hypothesis, subjects were instrumented with surface electrodes placed over seven muscles that were considered to be important during cycling. Measurements were made while subjects cycled at 100, 200, 300, and 400 W at each cadence: 50, 60, 80, 100, and 120 rpm. These power outputs represented effort which was up to 32% of peak power output for these subjects. RESULTS: When all seven muscles were averaged together, there was a proportional increase in EMG amplitude each cadence as power increased. A second-order polynomial equation fit the EMG:cadence results very well (r2 = 0.87- 0.996) for each power output. Optimal cadence (cadence with lowest amplitude of EMG for a given power output) increased with increases in power output: 57 +/- 3.1, 70 +/- 3.7, 86 +/- 7.6, and 99 +/- 4.0 rpm for 100, 200, 300, and 400 W, respectively. CONCLUSION: The results confirm that the level of muscle activation varies with cadence at a given power output. The minimum EMG amplitude occurs at a progressively higher cadence as power output increases. These results have implications for the sense of effort and preferential use of higher cadences as power output is increased.     

The accuracy of the ACSM cycle ergometry equation.

The purpose of this study was to determine the accuracy of the American College of Sports Medicine's equation for estimating the oxygen cost of exercise performed on a cycle ergometer. Sixty healthy males, ages 19-39 yr old, performed a five stage (30, 60, 90, 120, and 150 W) submaximal cycle ergometer test while their oxygen uptake was measured. Results indicated the standard error of estimate for the predicted oxygen values ranged from 0.11 to 0.22 l.min-1, with correlations between the actual and predicted values ranging from r = 0.22 to r = 0.50. Total errors ranged from 0.23 to 0.31 l.min-1. The actual oxygen cost was underestimated from 0.16 to 0.29 l.min-1 (P less than 0.05) by the equation at each workload. A revised equation was developed based upon the actual VO2-power relationship. The resulting slope was lower and the intercept higher when compared with the current ACSM equation. The slope and intercept of the revised equation are more consistent with values published in the literature. This equation appears as: VO2 (ml.min-1) = kgm.min-1 x 1.9 ml.min-1) + ((3.5 ml.kg-1.min-1 x kg body weight) + 260 ml.min-1). Predicted values from the revised equation were more accurate as reflected by slightly higher correlations, lower total errors, and lower mean differences from actual VO2 measurements than those from the current equation.     

Cardiovascular responses during upright and semi-recumbent cycle ergometry testing

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

Protocol dependency of VO2max during arm cycle ergometry in males with quadriplegia

The purpose of this study was to determine whether maximal oxygen uptake (VO2max) is protocol dependent during arm cycle ergometry (ACE) for quadriplegic males with spinal cord injuries (SCI). Twenty-four non-ambulatory subjects (aged 20-38 yr) with cervical SCI were divided into two groups based on wheelchair sports classification (IA group = 14; IB/IC group = 10). They underwent three different, continuous graded exercise tests spaced at least 1 wk apart on an electronically braked arm cycle ergometer. Following a 3-min, unloaded warm-up at 60 rpm, the work rate was increased 2, 4, or 6 W.min-1 for the IA group and 4, 6, or 8 W.min-1 for the IB/IC group. Ventilation and gas exchange were measured breath-by-breath with a SensorMedics 4400 computerized system. Repeated-measures ANOVA showed no significant difference among the three protocols for VO2max in the IA group (P greater than 0.05). The mean (+/- SD) VO2max values (ml.kg-1.min-1) were 10.8 (+/- 3.4), 11.0 (+/- 2.7), and 10.2 (+/- 2.9) for the 2, 4, and 6 W.min-1 protocols, respectively. In contrast, the IB/IC group showed a significant difference among the protocols for VO2max (P less than 0.05). The mean (+/- SD) VO2max values (ml.kg-1.min-1) were 16.8 (+/- 4.5), 15.3 (+/- 4.3), and 14.6 (+/- 4.3) for 4, 6, and 8 W.min-1, respectively. Post hoc analysis revealed a difference between the 4 and 8 W.min-1 protocols. Our results suggest that graded exercise testing of SCI persons with quadriplegia, using ACE, should employ work rate increments between 2-6 W.min-1 and that work rate increments of 8 W.min-1 or greater will underestimate VO2max.     

Cardiovascular physiology during supine cycle ergometry and dobutamine stress

PURPOSE: This study compared cardiac hemodynamics during supine cycle ergometry and dobutamine stress. METHODS: Thirty-two healthy volunteers (19 female, 13 male, 23.5 +/- 3.5 yr old) completed respective tests on separate days and in random order. Heart rate, blood pressure, and cardiac output were recorded at baseline and peak stress. Echocardiographic measures included left ventricular end-diastolic dimension, fractional shortening, heart rate corrected velocity of circumferential fiber shortening, end-systolic wall stress, and the difference between measured and predicted fiber shortening for measured wall stress. RESULTS: Compared with peak exercise, dobutamine infusion resulted in lower cardiac output (12 +/- 2 vs 16 +/- 4 l x min(-1), P < 0.0001), heart rates (163 +/- 7 vs 175 +/- 12 beats x min(-1), P < 0.0001), and systolic blood pressure (160 +/- 22 vs 185 +/- 20 mm Hg, P < or = 0.0001). Echocardiography demonstrated smaller left ventricular end-diastolic dimension (4.2 +/- 0.7 vs 4.5 +/- 0.7 cm, P = 0.013), higher fractional shortening (0.55 +/- 0.07 vs 0.50 +/- 0.06%, P < 0.001), higher VCFc (2.07 +/- 0.36 vs 1.54 +/- 0.20 circs x s(-1), P < 0.001) higher VCFdiff (0.94 +/- 0.35 vs 0.48 +/- 0.20 circs x s(-1), P < 0.001), and lower end-systolic wall stress (25 +/- 11 vs 42 +/- 16 g x cm(-2), P < 0.001). The stress-velocity relationship during dobutamine demonstrated higher y-intercept and steeper slope, indicating greater load-independent contractility. CONCLUSION: The cardiovascular adaptation to exercise and dobutamine stress differ significantly. Cardiac output during peak exercise is greater than during peak dobutamine secondary to increased heart rate and stroke volume. Despite a greater increase in contractility and decrease in afterload, a smaller increase in cardiac output during dobutamine stress may be secondary to limited ventricular preload.     

Montelukast has no ergogenic effect on cycle ergometry in cold temperature

PURPOSE: To examine the effects of a single 10-mg dose of ML on physical performance in EIB- and EIB+ athletes. METHODS: Twenty-four male college ice hockey players performed two 6-min maximal work accumulation bouts on an electronically braked cycle ergometer in subfreezing conditions (-2.5 +/- 0.4 degrees C) 6-8 h after either ML or placebo (PL) to obtain total work accumulated (kJ); subjects were evaluated for EIB after each exercise trial. RESULTS: Eight (33%) subjects were identified as EIB+ (23.5 +/- 13.35% fall in FEV1); 16 were EIB- (1.8 +/- 3.03% fall in FEV1). ML provided an approximately 50% protection against postexercise fall in FEV1. No significant differences in kJ were found between PL and ML trials for pooled subjects (95.3 +/- 13.69 and 94.8 +/- 13.27 kJ, respectively), EIB- subjects (99.6 +/- 13.26 and 99.0 +/- 11.81 kJ, respectively), or EIB+ subjects (86.8 +/- 10.67 and 86.5 +/- 12.72 kJ, respectively). Total work accumulated for EIB- subjects was significantly greater than for EIB+ subjects for both PL and ML (P < 0.05). CONCLUSION: A single 10-mg dose of ML had no ergogenic effect for EIB- and EIB+ subjects performing short-duration high-intensity exercise in subfreezing temperature, supporting the use of ML as EIB prophylaxis during international sport competition.     

A maximal cycle exercise protocol to predict maximal oxygen uptake

Maximal oxygen uptake (VO_2max) was predicted from maximal power output (MPO) in a progressive cycle ergometer test. The subjects were 232 men and 303 women 15–28 years of age. The relationship between VO_2max and MPO was: V O_2max (1 · min⁻¹) = 0.16 + (0.0117 × MPO) (w). A correlation coefficient of r = 0.88 was found between MPO and VO_2max. Test-retest reliability was evaluated by two procedures. Standard deviations of test-retest differences in MPO and VO_2max using the same standardized procedure in 35 subjects, were 10% and 8%, respectively, and Pearson correlations between test and retest values were 0.95 and 0.96, respectively.
When MPO of tests conducted at the schools was compared to a standardized test performed by a physiologist in 267 subjects, test-retest Pearson correlation was 0.82. A prediction model only including MPO and explaining 80% of the variability in VO_2max, is suggested for use in healthy adolescents and young adults.     

Effect of handlebar gripping on blood pressure during cycle ergometry

The effects on SBP, DBP and HR of gripping the cycle ergometer handlebar during dynamic cycle ergometry were evaluated in 39 healthy males. Heart rate, SBP and DBP were measured at 150 Watt power load while gripping and not gripping the handlebar of a cycle ergometer. The sequence of gripping first or second was randomized. No differences in SBP, DBP or HR were shown under the two treatments. For submaximal cycle ergometry the influence of static handgrip on the handlebar does not seem to have a significant influence on SBP, DBP or HR response to dynamic exercise.