Non-autonomic component in bradycardia of endurance trained men at rest and during exercise

Autonomic nervous alterations have generally been held responsible for the bradycardia of the endurance athlete. In order to determine whether there is also a non-autonomic component in the bradycardia of long-term training, we compared the intrinsic heart rate (HR) of highly trained bicyclists (heart volume: 995±155 ml) with that of untrained men (heart volume: 805±195 ml) at rest and during bicycle ergometer exercise at 50, 75 and 100% of maximal oxygen uptake (V_O2 max.) Intrinsic HR was achieved by combined vagal and beta-adrenergic blockade with atropine and propranolol or metoprolol (cardioselective) injected intravenously. Intrinsic HR was significantly lower in trained (T) than in untrained (UT) at rest and at all levels of exercise. The chronotropic reserve from resting HR to maximal HR was identical in the two groups. Nearly identical intrinsic HRs were achieved with atropine and either beta-adrenergic antagonist. HR differences between T and UT were very similar in magnitude—approximately 13 beats/min—at rest and during exercise at a given percentage of V_O2 max, with and without autonomic blockade. Evidence is thus provided for a non-autonomic component in the bradycardia of well-trained men which may be responsible for a parallel downward shift in the relationship between HR and percentage of V_O2 max. The lower intrinsic HR in well-trained men might be explained by, i.a. the cardiac enlargement.     

Evaluation of a cycling pre-load time trial protocol in recreationally active humans

The need for greater sensitivity in exercise performance measures is of particular importance in nutritional intervention studies and such measures have been investigated in trained cyclists, but not in those who have no experience of laboratory testing and/or the need to pace their effort. The aim of the present study was to evaluate a mixed design approach (constant load then time-trial) endurance type cycle ergometer protocol using recreationally active participants not well accustomed to cycling. Seven participants including one female (age 25 ± 5 years; body mass 74.4 ± 9.3 kg; peak VO₂ 3.91 ± 0.96 l) completed four repeat cycle tests. The test consisted of a “pre-load” (60 min at 65% of peak VO₂) followed by a 20 min time trial (performance measure). Reliability for the performance measure was assessed by calculating the individual participant coefficient of variation (CV) and a mean CV for the group. Excluding a familiarisation trial, mean CV for the group was 3.4% (95% confidence interval between 2.0 and 10.1%). It is concluded that the performance test described can be used in recreationally active young adults with lower variation after one familiarisation trial. The protocol might be used to evaluate an intervention if changes in performance are expected to be greater than 3.4%, or greater than around 7% if a signal to noise ratio of 2: 1 was to be considered appropriate.     

Effect of ambient temperature on caffeine ergogenicity during endurance exercise

It is well established that caffeine ingestion during exercise enhances endurance performance. Conversely, the physiological and psychological strain that accompanies increased ambient temperature decreases endurance performance. Little is known about the interaction between environmental temperature and the effects of caffeine on performance. The purpose of this study was to compare the effects of ambient temperature (12 and 33°C) on caffeine ergogenicity during endurance cycling exercise. Eleven male cyclists (mean ± SD; age, 25 ± 6 years; [(V)\dot] \textO_2max , {\dot V \text{O}}_{2\max } , 58.7 ± 2.9 ml kg⁻¹ min⁻¹) completed four exercise trials in a randomized, double blind experimental design. After cycling continuously for 90 min (average 65 ± 7% [(V)\dot] \textO_2max {\dot V \text{O}}_{2\max } ) in either a warm (33 ± 1°C, 41 ± 5%rh) or cool (12 ± 1°C, 60 ± 7%rh) environment, subjects completed a 15-min performance trial (PT; based on total work accumulated). Subjects ingested 3 mg kg⁻¹ of encapsulated caffeine (CAF) or placebo (PLA) 60 min prior to and after 45 min of exercise. Throughout exercise, subjects ingested water so that at the end of exercise, independent of ambient temperature, their body mass was reduced 0.55 ± 0.67%. Two-way (temperature × treatment) repeated-measures ANOVA were conducted with alpha set at 0.05. Total work (kJ) during the PT was greater in 12°C than 33°C [P < 0.001, η² = 0.804, confidence interval (CI): 30.51–62.30]. When pooled, CAF increased performance versus PLA independent of temperature (P = 0.006, η² = 0.542 CI: 3.60–16.86). However, performance differences with CAF were not dependent on ambient temperature (i.e., non-significant interaction; P = 0.662). CAF versus PLA in 12 and 33°C resulted in few differences in other physiological variables. However, during exercise, rectal temperature (T _re) increased in the warm environment (peak T _re; 33°C, 39.40 ± 0.45; 12°C, 38.79 ± 0.42°C; P < 0.05) but was not different in CAF versus PLA (P > 0.05). Increased ambient temperature had a detrimental effect on cycling performance in both the CAF and PLA conditions. CAF improved performance independent of environmental temperature. These findings suggest that caffeine at the dosage utilized (6 mg/kg body mass) is a, legal drug that provides an ergogenic benefit in 12 and 33°C.     

Effects of expectation and caffeine on arousal, well-being, and reaction time

The objective of this study is to determine the impact of expectation associated with placebo and caffeine ingestion. We used a three-armed, randomized, double-blind design. Two three-armed experiments varying instruction (true, false, control) investigated the role of expectations of changes in arousal (blood pressure, heart rate), subjective well-being, and reaction time (RT). In Experiment 1 (N = 45), decaffeinated coffee was administered, and expectations were produced in one group by making them believe they had ingested caffeinated coffee. In Experiment 2 (N = 45), caffeinated orange juice was given in both experimental groups, but only one was informed about the true content. In Experiment 1, a significant effect for subjective alertness was found in the placebo treatment compared to the control group. However, for RT and well-being no significant effects were found. In Experiment 2, no significant expectancy effects were found. Caffeine produced large effects for blood pressure in both treatments compared to the control group, but the effects were larger for the false information group. For subjective well-being (alertness, calmness), considerable but nonsignificant changes were found for correctly informed participants, indicating possible additivity of pharmacologic effect and expectations. The results tentatively indicate that placebo and expectancy effects primarily show through introspection.     

Effect of flurazepam, pentobarbital, and caffeine on arousal threshold

After laboratory and procedure adaptation, 6 normal subjects were randomly administered 30 mg flurazepam (twice), 100 mg pentobarbital (twice), 400 mg caffeine (once), and placebo (twice) on nonconsecutive nights. On each night subjects were aroused from standard segments of stage 2 sleep five to eight times with an ascending series of 1,000 Hz tones produced by an audiometer. Arousal threshold and awake threshold after each arousal were measured. Both thresholds were increased by flurazepam and pentobarbital and decreased by caffeine. All of the drugs appeared to modify arousal threshold in a time course fashion such that extreme effects were found during the first half of the night. However, the modifications of waking threshold by caffeine and flurazepam continued throughout the sleep period. The method may be a means of measuring the behavioral time course of drug activity during the sleep period.     

Effect of pedalling rates on physiological response during endurance cycling

This study was undertaken to examine the effect of different pedalling cadences upon various physiological responses during endurance cycling exercise. Eight well-trained triathletes cycled three times for 30 min each at an intensity corresponding to 80% of their maximal aerobic power output. The first test was performed at a freely chosen cadence (FCC); two others at FCC - 20% and FCC + 20%, which corresponded approximately to the range of cadences habitually used by road racing cyclists. The mean (SD) FCC, FCC - 20% and FCC + 20% were equal to 86 (4), 69 (3) and 103 (5) rpm respectively. Heart rate (HR), oxygen uptake (VO2), minute ventilation (VE) and respiratory exchange ratio (R) were analysed during three periods: between the 4th and 5th, 14th and 15th, and 29th and 30th min. A significant effect of time (P < 0.01) was found at the three cadences for HR, VO2. The VE and R were significantly (P < 0.05) greater at FCC + 20% compared to FCC - 20% at the 5th and 15th min but not at the 30th min. Nevertheless, no significant effect of cadence was observed in HR and VO2. These results suggest that, during high intensity exercise such as that encountered during a time-trial race, well-trained triathletes can easily adapt to the changes in cadence allowed by the classical gear ratios used in practice.     

The effect of skin temperature on performance during a 7.5-km cycling time trial

Aerobic exercise performance is seriously compromised in the heat. Possibly, a high skin temperature causes a rating of perceived exertion (RPE)-mediated decrease in exercise intensity. The purpose of this study was to determine the effect of skin temperature on power output during a 7.5-km cycling time trial. Thirteen well-trained male subjects performed a 7.5-km cycling time trial at 15°C and 50% relative humidity (CONTROL), with radiative heat stress during the time trial, and with (PRECOOL) or without (HEAT) precooling. Heat stress was applied by infrared heaters positioned in front of the cycle ergometer between 1.5 and 6.0 km. Skin, rectal, and pill temperature, power output, heart rate, and RPE were measured during the trial. Despite the lower mean skin temperature at the start of the time trial for PRECOOL compared to HEAT (-2.1 ± 0.7°C; P < 0.01) and CONTROL (-1.8 ± 0.6°C; P < 0.05), and a greater increase in mean skin temperature during the heat stress period for PRECOOL (4.5 ± 1.0°C) and HEAT (3.9 ± 0.8°C) than for CONTROL (-0.3 ± 0.6°C; P < 0.01), no differences in power output were found between HEAT (273 ± 45 W) and CONTROL (284 ± 43 W; P = 0.11) and between HEAT and PRECOOL (266 ± 50 W; P = 0.47). Power output during the time trial was greater for CONTROL than for PRECOOL (P < 0.05). Additionally, no differences were observed in core temperature measures, HR, and RPE. Skin temperature does not affect the selection and modulation of exercise intensity in a 7.5-km cycling time trial.     

An acute oral dose of caffeine does not alter glucose kinetics during prolonged dynamic exercise in trained endurance athletes

This study investigated the possible influence of oral caffeine administration on endogenous glucose production and energy substrate metabolism during prolonged endurance exercise. Twelve trained endurance athletes [seven male, five female; peak oxygen consumption ( ) = 65.5 ml·kg^–1·min^–1] performed 60 min of cycle ergometry at 65% twice, once after oral caffeine administration (6 mg·kg^–1) (CAF) and once following consumption of a placebo (PLA). CAF and PLA were administered in a randomized double-blind manner 75 min prior to exercise. Plasma glucose kinetics were determined with a primed-continuous infusion of [6,6-²H]glucose. No differences in oxygen consumption ( ), and carbon dioxide production ( ) were observed between CAF and PLA, at rest or during exercise. Blood glucose concentrations were similar between the two conditions at rest and also during exercise. Exercise did lead to an increase in serum free fatty acid (FFA) concentrations for both conditions; however, no differences were observed between CAF and PLA. Both the plasma glucose rate of appearance ( ) and disappearance ( ) increased at the onset of exercise (P<0.05), but were not affected by CAF, as compared to PLA. CAF did lead to a higher plasma lactate concentration during exercise (P<0.05). It was concluded that an acute oral dose of caffeine does not influence plasma glucose kinetics or energy substrate oxidation during prolonged exercise in trained endurance athletes. However, CAF did lead to elevated plasma lactate concentrations. The exact mechanism of the increase in plasma lactate concentrations remains to be determined. Electronic Publication     

Effect of endurance training on different mechanical efficiency indices during submaximal cycling in subjects unaccustomed to cycling.

The purpose of this study was to evaluate different efficiency indices, i.e., gross (GE: no baseline correction), net (NE: resting metabolism as baseline correction), and work (WE: unloaded exercise as baseline correction), to reveal the effect of endurance training on mechanical efficiency. Nine healthy sedentary women undertook an incremental test and submaximal cycling exercise, at an intensity corresponding to 50% of the pretraining peak oxygen uptake, before and after 6 weeks of endurance training (18 sessions of 45 min). The training effects on efficiency indices were tested by comparisons based on GE, NE, and WE as well as by the differences between the percentage changes of all indices (%GE, %NE, %WE). Endurance training resulted in significantly higher GE (+11.1%; p < 0.001) and NE (+9.1%; p < 0.01). Only minor significant improvement (+2.4%; p < 0.05) was observed with the WE index because the value used for baseline subtraction was significantly reduced by the training sessions, due perhaps to improvement in pedaling skill. As a consequence, %WE was significantly lower than %GE (p < 0.01) and %NE (p < 0.05), while %GE and %NE were not significantly different. We conclude that mechanical efficiency of cycling increases with training in women previously unfamiliar with cycling, and that the WE index is less sensitive to this training effect than GE and NE indices.     

Reliability of a cycling time trial in a glycogen-depleted state

The aim of this study was to investigate the reliability of a protocol designed to simulate endurance performance in events of long duration (∼5 h) where endogenous carbohydrate stores are low. Seven male subjects were recruited (age 27 ± 7 years, VO_2max 66 ± 5 ml/kg/min, W _max 367 ± 42 W). The subjects underwent three trials to determine the reliability of the protocol. For each trial subjects entered the laboratory in the evening to undergo a glycogen-depleting exercise trial lasting approximately 2.5 h. The subjects returned the following morning in a fasted state to undertake a 1-h steady-state ride at 50% W _max followed by a time trial of approximately 40-min duration. Each trial was separated by 7–14 days. The trials were analysed for reliability of time to completion of the time trial using a coefficient of variation (CV), with 95% confidence intervals (data are mean ± SD). The times to complete the three trials were 2,546 ± 529, 2,585 ± 490 and 2,568 ± 555 s for trials 1, 2 and 3, respectively. The CV between trials 1 and 2 was 4.5% (95% CI 2.9–10.4%) and between trials 2 and 3, 3.8% (95% CI 2.4–9.9%). There was no difference in oxygen uptake, respiratory exchange ratio, carbohydrate oxidation, fat oxidation, plasma glucose concentration and plasma lactate concentration between the three trials. Therefore we can conclude that prior glycogen depletion does produce a reliable measure of performance with metabolic characteristics similar to ultraendurance exercise.     

Effect of exercise-induced hyperventilation on airway resistance and cycling endurance

The purpose of the present study was to investigate the effect of exercise induced hyperventilation and hypocapnia on airway resistance (R _aw), and to try to answer the question whether a reduction of R _aw is a mechanism contributing to the increase of endurance time associated with a reduction of exercise induced hyperventilation as for example has been observed after respiratory training. Eight healthy volunteers of both sexes participated in the study. Cycling endurance tests (CET) at 223 (SD 47) W, i.e. at 74 (SD 5)% of the subject's peak exercise intensity, breathing endurance tests and body plethysmograph measurements of pre- and postexercise R _aw were carried out before and after a 4-week period of respiratory training. In one of the two CET before the respiratory training CO₂ was added to the inspired air to keep its end-tidal concentration at 5.4% to avoid hyperventilatory hypocapnia (CO₂-test); the other test was the control. The pre-exercise values of specific expiratory R _aw were 8.1 (SD 2.8), 6.8 (SD 2.6) and 8.0 (SD 2.1) cm H₂O?·?s and the postexercise values were 8.5 (SD 2.6), 7.4 (SD 1.9) and 8.0 (SD 2.7) cm H₂O?·?s for control CET, CO₂-CET and CET after respiratory training, respectively, all differences between these tests being nonsignificant. The respiratory training significantly increased the respiratory endurance time during breathing of 70% of maximal voluntary ventilation from 5.8 (SD 2.9) min to 26.7 (SD 12.5) min. Mean values of the cycling endurance time (t _cend) were 22.7 (SD 6.5) min in the control, 19.4 (SD 5.4) min in the CO₂-test and 18.4 (SD 6.0) min after respiratory training. Mean values of ventilation ( ${\dot V}$ _E) during the last 3?min of CET were 123 (SD 35.8) l?·?min^?1 in the control, 133.5 (SD 35.1) l?·?min^?1 in the CO₂-test and 130.9 (SD 29.1) l?·?min^?1 after respiratory training. In fact, six subjects ventilated more and cycled for a shorter time, whereas two subjects ventilated less and cycled for a longer time after the respiratory training than in the control CET. In general, the subjects cycled longer the lower the ${\dot V}$ _E, if all three CET are compared. It is concluded that R _aw measured immediately after exercise is independent of exercise-induced hyperventilation and hypocapnia and is probably not involved in limiting t _cend, and that t _cend at a given exercise intensity is shorter when ${\dot V}$ _E is higher, no matter whether the higher ${\dot V}$ _E occurs before or after respiratory training or after CO₂ inhalation.     

Comparison of changes in testosterone concentrations after strength and endurance exercise in well trained men

Summary Changes in the testosterone concentrations after single sessions of endurance and strength training were measured in seven well trained men, experienced in both forms of training. Both training sessions were rated as hard to very hard on the Borg scale. Blood samples for testosterone measurements were taken before, immediately after, and 2, 4 and 6 h after the training sessions as well as the next morning. The mean tes tosterone concentration increased 27% (P<0.02) and 37% (P< 0.02) during the strength and endurance training session, respectively. Two hours after the training sessions the mean testosterone concentration had re turned to the pre-training level and remained at that level for the length of the observation period. There were no significant differences in the changes in testosterone concentration after strength and endurance training but there were large differences in the testosterone response at the level of the individual. A high correlation (r=0.98;P<0.001) for individuals was found between increases in testosterone concentration after strength and after endurance training. It was concluded that the changes in mean testosterone values followed the same timecourse after single sessions of strength and endurance training of the same duration and perceived exertion. The interindividual differences in tes tosterone response may be of importance for individual adaptation to training.     

Effect of isokinetic cycling versus weight training on maximal power output and endurance performance in cycling

The aim of this study was to compare the effects of a weight training program for the leg extensors with isokinetic cycling training (80 rpm) on maximal power output and endurance performance. Both strength training interventions were incorporated twice a week in a similar endurance training program of 12 weeks. Eighteen trained male cyclists (VO_2peak 60 ± 1 ml kg⁻¹ min⁻¹) were grouped into the weight training (WT n = 9) or the isokinetic training group (IT n = 9) matched for training background and sprint power (P _max), assessed from five maximal sprints (5 s) on an isokinetic bicycle ergometer at cadences between 40 and 120 rpm. Crank torque was measured (1 kHz) to determine the torque distribution during pedaling. Endurance performance was evaluated by measuring power, heart rate and lactate during a graded exercise test to exhaustion and a 30-min performance test. All tests were performed on subjects’ individual race bicycle. Knee extension torque was evaluated isometrically at 115° knee angle and dynamically at 200° s⁻¹ using an isokinetic dynamometer. P _max at 40 rpm increased in both the groups (~15%; P < 0.05). At 120 rpm, no improvement of P _max was found in the IT training group, which was possibly related to an observed change in crank torque at high cadences (P < 0.05). Both groups improved their power output in the 30-min performance test (P < 0.05). Isometric knee extension torque increased only in WT (P < 0.05). In conclusion, at low cadences, P _max improved in both training groups. However, in the IT training group, a disturbed pedaling technique compromises an improvement of P _max at high cadences.     

Effect of transdermal nicotine administration on exercise endurance in men

Nicotine is widely reported to increase alertness, improve co-ordination and enhance cognitive performance; however, to our knowledge there have been no attempts to replicate these findings in relation to exercise endurance. The purpose of this study was to determine the effects nicotine might have on cycling endurance, perception of exertion and a range of physiological variables. With local ethics committee approval and having obtained informed consent, 12 healthy, non-smoking men (22 +/- 3 years; maximal O2 uptake, 56 +/- 6 ml kg(-1) min(-1), mean +/- s.d.) cycled to exhaustion at 18 degrees C and 65% of their peak aerobic power, wearing either a 7 mg transdermal nicotine patch (NIC) or a colour-matched placebo (PLA) in a randomized cross-over design; water was available ad libitum. Subjects were exercising at approximately 75% of their maximal O2 uptake with no differences in cadence between trials. Ten out of 12 subjects cycled for longer with NIC administration, and this resulted in a significant 17 +/- 7% improvement in performance (P < 0.05). No differences were observed for perceived exertion, heart rate or ventilation. There were no differences in concentrations of plasma glucose, lactate or circulating fatty acids. In the absence of any effect on peripheral markers, we conclude that nicotine prolongs endurance by a central mechanism. Possible modes of action are suggested.     

Stroke volume response to incremental submaximal exercise in aerobically trained, active, and sedentary men.

Stroke volume response of trained cyclists (n = 10; Trained), active but untrained men (n = 10; Active), and sedentary men (n = 10; Sedentary) was determined by impedance cardiography during cycle ergometer exercise. For the Trained, at a heart rate of 90 beats. min(-1), stroke volume increased by 27% compared to baseline levels, whereas stroke volume of Active and Sedentary groups did not significantly increase. Throughout exercise indices of ventricular emptying and filling of Trained were significantly greater than that of the other two groups whereas ventricular rates of the Active were significantly greater than those of the Sedentary. Throughout exercise cardiac contractility of the Trained was significantly greater than the other two groups. Results indicate that despite similar resting heart rate, stroke volume, and body mass, Trained compared to Active men significantly enhanced stroke volume, ventricular filling, and cardiac contractility during incremental ergometry exercise. Active compared to Sedentary men, however, displayed significantly larger stroke volume and ventricular filling rates during ergometry. We conclude that impedance cardiography indices of ventricular performance of aerobically trained men were superior to those of active, untrained men possessing similar resting stroke volume and heart rate. Furthermore, the ventricular performance of the active men possessing large resting stroke volume was superior to that of sedentary men.     

Effect of cycling position on oxygen uptake and preferred cadence in trained cyclists during hill climbing at various power outputs

Numerous researchers have studied the physiological responses to seated and standing cycling, but actual field data are sparse. One open issue is the preferred cadence of trained cyclists while hill climbing. The purpose of this study, therefore, was to examine the affect of cycling position on economy and preferred cadence in trained cyclists while they climbed a moderate grade hill at various power outputs. Eight trained cyclists (25.8 ± 7.2 years, 68.8 ± 5.0 ml kg⁻¹ min⁻¹, peak power 407.6 ± 69.0 W) completed a seated and standing hill climb at approximately 50, 65 and 75% of peak power output (PPO) in the order shown, although cycling position was randomized, i.e., half the cyclists stood or remained seat on their first trial at each power output. Cyclists also performed a maximal trial unrestricted by position. Heart rate, power output, and cadence were measured continuously with a power tap; ventilation , BF and cadence were significantly higher with seated climbing at all intensities; there were no other physiological differences between the climbing positions. These data support the premise that trained cyclists are equally economical using high or low cadences, but may face a limit to benefits gained with increasing cadence.     

Effect of posture on high-intensity constant-load cycling performance in men and women

The time sustained during a graded cycle exercise is ~10% longer in an upright compared with a supine posture. However, during constant-load cycling this effect is unknown. Therefore, we tested the postural effect on the performance of high-intensity constant-load cycling. Twenty-two active subjects (11 men, 11 women) performed two graded tests (one upright, one supine), and of those 22, 10 subjects (5 men, 5 women) performed three high-intensity constant-load tests (one upright, two supine). To test the postural effect on performance at the same absolute intensity, during the upright and one of the supine constant-load tests subjects cycled at 80% of the peak power output achieved during the upright graded test. To test the postural effect on performance at the same relative intensities, during the second supine test subjects cycled at 80% of the peak power output achieved during the supine graded test. Exercise time on the graded and absolute intensity constant-load tests for all subjects was greater (P<0.05) in the upright compared with supine posture (17.9±3.5 vs. 16.1±3.1 min for graded; 13.2±8.7 vs. 5.2±1.9 min for constant-load). This postural effect at the same absolute intensity was larger in men (19.4±8.5 upright vs. 6.6±1.6 supine, P<0.001) than women (7.1±2 upright vs. 3.9±1.4 supine, P>0.05) and it was correlated (P<0.05) with both the difference in between positions during the first minute of exercise (r=0.67) and the height of the subjects (r=0.72). In conclusion, there is a very large postural effect on performance during constant-load cycling exercise and this effect is significantly larger in men than women.     

Respiratory responses of elite oarsmen,former oarsmen,and highly trained non-rowers during rowing,cycling and running

The position of the body and use of the respiratory muscles in the act of rowing may limit ventilation and thereby reduce maximal aerobic power relative to that achieved in cycling or running, in spite of the greater muscle mass involved in rowing. This hypothesis was investigated for three groups of male subjects: nine elite senior oarsmen, eight former senior oarsmen and eight highly trained athletes unskilled in rowing. The subjects performed graded exercise to maximal effort on a rowing ergometer, cycle ergometer and treadmill while respiratory minute volume and oxygen consumption were monitored continuously. The VE at a given during intense submaximal exercise (greater than 75% of maximal ) was not significantly lower in rowing compared with that in cycling and treadmill running for any group, which would suggest that submaximal rowing does not restrict ventilation. At maximal effort, and for rowing were less than those for the other types of exercise in all the groups, although the differences were not statistically significant in the elite oarsmen. These data are consistent with a ventilatory limitation to maximal performance in rowing that may have been partly overcome by training in the elite oarsmen. Alternatively, a lower maximal VE in rowing might have been an effect rather than a cause of a lower maximal if maximal was limited by the lower rate of muscle activation in rowing.