Cadence and performance in elite cyclists

Many studies have attempted to describe the optimal cadence in cycling. However, the effect on performance has received little attention. The aim of the present study was therefore to examine the effect of cadence on performance during prolonged cycling (~30 min). Fourteen male elite cyclists performed two or five time trials at different cadences [60, 80, 100, 120 rpm or freely chosen cadence (FCC)]. The total work was the same between the time trials, and the subjects were instructed to complete each time trial as fast as possible by adjusting the workload with buttons mounted on the handlebar. Accumulated work and cadence was visualised on a monitor. Oxygen uptake was measured continuously and blood lactate concentration every fifth minute. Compared to 80 rpm, finishing times at 60, 100 and 120 rpm were 3.5, 1.7 and 10.2% slower (P<0.05). Finishing time at FCC (mean 90 rpm) was indistinguishable from 80 and 100 rpm. Gross efficiency at 80 rpm was 2.9, 2.3, 3.4 and 12.3% larger than at 60, FCC, 100 and 120 rpm, respectively (P<0.05). The maximal energy turnover rate was 1.7% higher at 100 than at 80 rpm (P<0.05). This could not, however, compensate for the 3.4% lower efficiency at 100 rpm. This study demonstrated that elite cyclists perform best at their most efficient cadence despite the maximal energy turnover rate being larger at a higher cadence.     

Factors associated with the selection of the freely chosen cadence in non-cyclists

The purpose of this study was to examine both the freely chosen cadence (FCC) and the physical variables associated with cadence selection in non-cyclists. Eighteen participants pedalled at 40, 50, and 60% of their maximal power output (determined by a maximal oxygen uptake test, W _max), whilst cadence (50, 65, 80, 95, 110 rpm, and FCC) was manipulated. Gross efficiency, was used to analyse the most economical cadence whilst central and peripheral ratings of perceived exertion (RPE) were used to measure the most comfortable cadence and the cadence whereby muscle strain was minimised. Peak (T _peak), mean crank torque (T _mean) and the crank torque profile were analysed at 150 and 200 W at cadences of 50, 65, 80, 95, and 110 rpm in order to determine the mechanical load. FCC was found to be approximately 80 rpm at all workloads and was significantly higher than the most economical cadence (50 rpm). At 60% W _max, RPE peripheral was minimised at 80 rpm which coincided with the FCC. Both T _peak and T _mean decreased as cadence increased and, conversely, increased as power output increased. An analysis of the crank torque profile showed that the crank angle at both the top (DP_top) and the bottom (DP_bot) dead point of the crank cycle at 80 rpm occurred later in the cycling revolution when compared to 50 rpm. The findings suggested that the FCC in non-cyclists was more closely related to variables that minimise muscle strain and mechanical load than those associated with minimising metabolic economy.     

Freely chosen pedal rate during free cycling on a roller and ergometer cycling

The purpose of this study was to examine the effect of regulation of work rate, computer controlled versus controlled by the subject, on the relationship between work rate, freely chosen pedal rate (FCC) and gross efficiency. Eighteen male cyclists participated in the study. One group, freely cycling (FC) on a competition bike mounted on an electromagnetic roller, could use gearing and cadence to achieve each work rate. The other group (EC) was cycling on an ergometer which enables a constant work rate, independent of cadence. Subjects performed an increasing work rate protocol from 100 W up to exhaustion. We found a strong interaction between group and work rate on cadence (P < 0.001). In the FC group, work rate affected cadence (P < 0.001), increasing from 72 rpm at 100 W to 106 rpm at 350 W. For the EC group, no work rate effect was present (average FCC 92 rpm). Gross efficiency increased with work rate for both groups. The efficiency–cadence relationship was strongly affected by the protocol. At a given work rate, very similar efficiency values were obtained at highly different cadences. The discrepancy in the FCC-work rate relationship between the EC group and the FC group may be related to the manner in which one can regulate work rate. FCC depends not only on work rate but is also affected considerably by the manner in which the work rate can be controlled by cadence. This finding may have important implications for the interpretation of the preferred pedaling rate, especially how this is related to optimizing metabolic cost.     

Cardiorespiratory, neuromuscular and kinematic responses to stationary running performed in water and on dry land

The purpose of this study was to analyze the cardiorespiratory, neuromuscular and kinematic responses obtained during the stationary running in aquatic and dry land environments. Twelve women took part in the experimental protocol. Stationary running was performed for 4 min at three submaximal cadences and for 15 s at maximal velocity, with the collection of kinematic (peak hip angular velocity (AV)), cardiorespiratory (oxygen uptake (VO₂)) and neuromuscular variables (electromyographic (EMG) signal from the rectus femoris (RF), vastus lateralis (VL), semitendinosus (ST) and short head of the biceps femoris (BF) muscles) in land-based and water-based test protocols. Factorial ANOVA was used, with an alpha level of 0.05. AV was significantly higher when the exercise was performed on land, and became significantly higher as the execution cadence increased. Similarly, VO₂ was significantly higher in the land-based exercise and rose as cadence increased. With the increase in the submaximal execution cadences, there was no corresponding increase in the EMG signal from the VL, BF, RF and ST muscles in either environment, though such a significantly increase was seen between the submaximal cadences and the maximal velocity. Dry land presented significantly greater EMG signal responses for all muscles at the submaximal cadences, except for the ST muscle. However, at the maximal velocity, all the analyzed muscle groups showed similar responses in both environments. In summary, for both environments, cardiorespiratory responses can be maximized by increasing the submaximal cadences, while neuromuscular responses are only optimized by using maximal velocity.     

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.     

Effect of end-point cadence on the maximal work-time relationship

This study examined the effect of end-point cadence on the parameters of the work-time relationship determined for cycle ergometry. Eight male subjects completed four maximal tests on an electrically-braked cycle ergometer that regulated a constant power output independent of cadence. The power outputs imposed ranged between an average of 259 W and 403 W, whereas the corresponding durations ranged between 139 s and 1691 s. During each test subjects were required to maintain a cadence of 80–90 rpm. Accumulated time to end-point cadences of 70, 60 and 50 rpm were recorded. The four work-time determinations for each of three end-point cadences were used to determine linear relationships between work and time, yielding both a y-intercept, which represents anaerobic work capacity, and a slope, which is termed critical power (CP), for each end-point cadence. There was a significant increase in the y-intercept as end-point cadence decreased from 70 to 60 rpm (F[1,7]=36.7, p < 0.001) or 70 to 50 rpm (F[1,7]=80.1, p < 0.001), but not from 60 rpm to 50 rpm (F[1,7]=3.28, p > 0.05). In contrast, there was no effect of end-point cadence on CP (F[2,14]=1.89, p < 0.05). These results demonstrate that the end-point cadence selected to terminate tests only affects the y-intercept of the work-time relationship. To control for this effect, the cadence at which each test is terminated should be standardised if determination of anaerobic work capacity, as represented by the y-intercept, is required.     

Effect of exercise duration on optimal pedaling rate choice in triathletes.

The purpose of this study was to investigate the effect of an exercise duration similar to triathlon's cyclism event (approximately 1 hr), on factors determining the freely chosen cadence. Nine trained triathletes completed a cycling track session conducted at a speed corresponding to 75% of maximal heart rate. This session was composed of five submaximal rides performed at five cadences presented in a random order (65, 80, 95, 110 rpm and freely chosen cadence) realized before and after a 1-hr exercise at the freely chosen cadence. Results show, during the first condition, that triathletes choose spontaneously a cadence (90,1 +/- 10,7 rpm) close to the neuromuscular optimum (89,6 +/- 1,1 rpm) while at the end of exercise, a decrease of the freely chosen cadence (82,8 +/- 8,7 rpm) was observed toward the energetically optimal cadence (78,6 +/- 5,8 rpm). These findings suggest the hypothesis of an adaptation of the movement pattern with the exercise duration in order to minimize the energy cost rather than the neuromuscular cost of cycling.     

Gear, inertial work and road slopes as determinants of biomechanics in cycling

In cycling the gear determines the distance travelled and the mean applied force at each leg thrust. According to Padilla et al. (J Appl Physiol 89:1522–1527, 2000), an elite cyclist was able to cycle for an hour at 14.6 m·s^–1 developing 510 W at a pedal frequency of 101 rpm. Thus, the opposing force was 34 N (=500/14.6), whereas the mean force, developed by the leg muscles, was 144.1 N. It can be calculated that in the same subject cycling on a 20% slope at the same pedal frequency, the velocity would be reduced by about 5 times, i.e. to 2.9 m·s^–1because of a fivefold increase of the opposing force. In reality, the increase of mean force developed by leg muscles is even larger, because of the fall of the cadence to 60 rpm. In general, during mountain ascents cyclists develop high forces at low cadences that are likely to be more economical; in contrast, on flat ground, they increase the pedalling rates because their aerodynamic posture does not allow high force production. The intermittent pattern of muscular force application generates speed changes that become more evident at great inclines and low cadences. It can be shown that inertial work is appreciable in cycling, increasing with the incline of the road and decreasing with the cadence. However, inertial work does not seem to affect efficiency. Differences in physiologic potential make differences in performance more evident in time trials where the mean incline of the road is not negligible. Cyclists with low body size have an advantageous force versus mass ratio in high mountain ascents.     

Power-cadence relationship in endurance cycling

In maximal sprint cycling, the power–cadence relationship to assess the maximal power output (P _max) and the corresponding optimal cadence (C _opt) has been widely investigated in experimental studies. These studies have generally reported a quadratic power–cadence relationship passing through the origin. The aim of the present study was to evaluate an equivalent method to assess P _max and C _opt for endurance cycling. The two main hypotheses were: (1) in the range of cadences normally used by cyclists, the power–cadence relationship can be well fitted with a quadratic regression constrained to pass through the origin; (2) P _max and C _opt can be well estimated using this quadratic fit. We tested our hypothesis using a theoretical and an experimental approach. The power–cadence relationship simulated with the theoretical model was well fitted with a quadratic regression and the bias of the estimated P _max and C _opt was negligible (1.0 W and 0.6 rpm). In the experimental part, eight cyclists performed an incremental cycling test at 70, 80, 90, 100, and 110 rpm to yield power–cadence relationships at fixed blood lactate concentrations of 3, 3.5, and 4 mmol L⁻¹. The determined power outputs were well fitted with quadratic regressions (R ² = 0.94–0.96, residual standard deviation = 1.7%). The 95% confidence interval for assessing individual P _max and C _opt was ±4.4 W and ±2.9 rpm. These theoretical and experimental results suggest that P _max, C _opt, and the power–cadence relationship around C _opt could be well estimated with the proposed method.     

The effect of pedalling cadence on maximal accumulated oxygen deficit

Pedalling cadence influences the oxygen demand and the tolerable duration of severe intensity cycle ergometer exercise. Both of these variables are factors in the calculation of maximal accumulated oxygen deficit (MAOD), which is a widely accepted measure of anaerobic capacity. We were therefore interested in determining whether pedalling cadence affected the value of MAOD. Eighteen university students performed square wave cycling tests, using cadences of 60, 80, and 100 rev min(-1), at work rates selected to cause exhaustion in ~5 min. The oxygen demands for the tests were estimated by extrapolation from the steady-state oxygen uptake in two 4-min moderate intensity bouts performed using each cadence, and were greater at higher cadences. Times to exhaustion were shorter at higher cadences (368 ± 168 s at 60 rev min(-1) > 299 ± 118 s at 80 rev min(-1) > 220 ± 85 s at 100 rev min(-1)). These factors conflated to produce values for MAOD that were not affected by cadence (52 ± 5 ml kg(-1) = 52 ± 5 ml kg(-1) = 52 ± 5 ml kg(-1)). Similarly, the blood lactate concentrations measured 5 min post-exercise were not affected by the pedalling cadence (10.5 ± 2.1 mM = 10.8 ± 1.0 mM = 10.7 ± 2.0 mM). Although muscle contraction frequency influences many exercise responses, we conclude that the expression of anaerobic capacity is not affected by the choice of pedalling cadence.     

The energetically optimal cadence decreases after prolonged cycling exercise

This study investigated the change in the energetically optimal cadence after prolonged cycling. The energetically optimal cadence (EOC) was determined in 14 experienced cyclists by pulmonary gas exchange at six different cadences (100–50 rpm at 10 rpm intervals). The determination of the EOC was repeated after a prolonged cycling exercise of 55 min duration, where cadence was fixed either at high (>95 rpm) or low (<55 rpm) pedalling rates. The EOC decreased after prolonged cycling exercise at a high as well as at a low fixed cadence (P < 0.01). According to the generalized muscle equations of Hill, this indicates that most likely more type I muscle fibres contribute to muscular power output after fatiguing cycling exercise compared to cycling in the beginning of an exercise bout. We suggest that the determination of EOC might be a potential non-invasive method to detect the qualitative changes in activated muscle fibres, which needs further investigation.     

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.     

Prediction of time to exhaustion from blood lactate response during submaximal exercise in competitive cyclists

The aim of this investigation was to develop and validate a new method to predict time to exhaustion (pTE) from blood lactate variables measured during a submaximal non-exhaustive constant workload cycling test in professional cyclists. A multiple regression equation to estimate pTE from blood lactate variables measured within the first 10 min of a submaximal test and TE was determined in 40 competitive cyclists. Predicted TE reliability [individual coefficient of variation (CV)] was calculated in eight amateur cyclists who repeated the proposed test three times. Seasonal variations of pTE were monitored in 12 professional cyclists. Validity of pTE was determined by the known-group difference method in 49 professional cyclists. The prediction equation was: log_nTE = 4.2067 − 0.8221(log_n B) − 0.2519(log_n C), where B is the lactate concentration at the 10th minute of the constant workload test and C is the lactate slope calculated between the 5th and 10th minute (adjusted r ² =0.83, root mean square error in cross validation=23.1%). Predicted TE CV was 11.7%. The pTE obtained at the beginning of the season and the best and worst tests performed during the competitive season, resulted 162, 224 and 103% higher than the basic period test, respectively (P<0.05). Predicted TE was the only parameter discriminating elite from subelite professional cyclists. In conclusion, this study demonstrates that pTE is a valid and practical alternative to incremental tests and direct measures of endurance capacity requiring exhaustive efforts for the evaluation of competitive cyclists.     

Validity of the W170 test for predicting maximal oxygen intake

Summary Recent research has related pedalling frequency to perceived exertion, indicating that subjects pedalling at higher frequencies tend to perceive lower levels of exertion. If tests administered at higher pedalling speeds are valid, then more accurate data on extremely low fit individuals might be possible. The purpose of this study was to determine the validity of the Wahlund-Sjostrand W₁₇₀ test administered at 50 and 80 rpm. Maximal oxygen intake was determined for thirty male volunteer college students using standard open-circuit techniques. W₁₇₀ tests were administered at 50 and 80 rpm using standard test protocol. The results indicated a differential effect of pedalling speed upon the validity of the W₁₇₀ tests. Validity coefficients of r _xy=0.73 and r _xy=0.64 were found for the 50 and 80 rpm tests, respectively. Maximal oxygen intake predicted from the W₁₇₀ test administered at 80 rpm was significantly different from both the criterion maximal oxygen intake and the W₁₇₀ prediction at 50 rpm. This difference was attributed to a significantly higher heart rate response to 80 rpm tests at the lower workload of 600 kpm/min. It was concluded that more valid W₁₇₀ tests are attained at the conventional pedalling speed of 50 rpm.     

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.     

Physiological parameters determined at OBLA vs. a fixed heart rate of 175 beats x min-1 in an incremental test performed by amateur and professional cyclists

A blood lactate concentration of 4 mmol x l-1 (OBLA) is frequently used as an indicator of the maximal steady state of lactate (MLSS) for workload planning in training programs. The aim of the present investigation was to compare several metabolic parameters determined at OBLA and at a fixed heart rate of 175 beats x min-1 (HR175) in amateur cyclists (AC) and professional cyclists (PC). Sixteen AC and 22 PC performed an exercise test on a cycle ergometer following a ramp protocol (25 W x min-1, 70-80 rpm) to exhaustion. Gaseous exchange was monitored throughout the test. VO2, %VO2 max, and power output (W) corresponding to OBLA and HR175 were determined and mean values compared using a Student's t-test. Findings indicated higher VO2 max and W in general in PC (p<0.01), and higher VO2 and W at OBLA and HR175 in PC (p<0.01). No significant difference was found between values determined at OBLA and HR175 in the AC group, while in the PC group, VO2, %VO2 max, and W were higher at OBLA. These observations suggest the possible use of a fixed, reference HR of 175 beats x min-1 to determine the exercise intensity corresponding to OBLA in amateur cyclists. This was not the case for the professional cyclists.     

Influence of cycling cadence on neuromuscular activity of the knee extensors in humans

The aim of the present study was to investigate the influence of pedalling rate and power output in cycling on the neuromuscular activity of the knee extensor muscles. Ten subjects took part in 15 randomised trials, which consisted of three levels of power outputs (60%, 80% and 100% maximal aerobic power) and five cadences (70%, 85%, 100%, 115% and 130% of the freely chosen cadence, FCC). Root mean square (rms) was utilized to quantify electromyographic activity of the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) muscles. The mean (SD) FCC did not change with power output, ranging from 85.0 (11.9) to 88.0 (11.1) rpm. A significant power effect (P<0.01) for the rms of VL, VM and RF muscles was observed. Results showed no significant cadence effect on neuromuscular activity of the VL and VM muscles, while the rms of the RF muscle was significantly greater (P<0.05) at 70% FCC when compared to other cadences. In conclusion, the neuromuscular activity of the knee extensor muscles was not significantly influenced by cadence manipulations. Thus, minimisation of the neuromuscular activity of these muscles would not seem to lead to the choice of a cadence in cycling. Electronic Publication     

Peak and submaximal steady-state metabolic and cardiorespiratory responses during arm-powered and arm-trunk-powered handbike ergometry in able-bodied participants

The purpose of this study was to compare the peak and submaximal metabolic and cardiorespiratory responses during steady-state arm-powered (AP) and arm-trunk-powered (ATP) handbike ergometry. Twelve male able-bodied participants with no prior experience in handcycling completed a maximal progressive incremental test and a series of 6-minute submaximal tests at 130 W with various cadences in a custom-designed handbike ergometer that allowed a realistic simulation of AP and ATP handcycling. Peak power output, peak oxygen uptake, and peak ventilation were significantly lower, whereas peak blood lactate concentration was significantly higher during AP handcycling. Mean gross mechanical efficiency was significantly higher during AP handcycling (range 16.7 to 20.5%) compared with ATP handcycling (range 15.8 to 17.6%). These results suggest that AP handcycling is advantageous during submaximal steady-state handcycling, whereas ATP handcycling allows for a higher peak power output generation. However, it remains unclear which handbike configuration would be favorable during competition.     

The role of muscle pump in the development of cardiovascular drift

This study examined the role of muscle pump in the development of cardiovascular drift (CV_drift) during cycling. Twelve healthy males (23.4 ± 0.5 years, mean ± SE) exercised for 90 min with 40 and 80 pedal revolutions per minute (rpm) at the same oxygen consumption, in two separate days. CV_drift was developed in both conditions as indicated by the drop in stroke volume (SV) and the rise in heart rate (HR) from the 20th min onwards (ΔSV = −16.2 ± 2.0 and −17.1 ± 1.0 ml beat⁻¹; ΔHR = 18.3 ± 2.0 and 17.5 ± 3.0 beats min⁻¹ for 40 and 80 rpm, respectively, P < 0.05) but without difference between conditions. Mean cardiac output (CO₂ rebreathing) was 14.7 ± 0.3 l min⁻¹ and 15.0 ± 0.3 l min⁻¹, and mean arterial pressure was 100.0 ± 1.0 mmHg and 96.7 ± 0.8 mmHg for 40 and 80 rpm, respectively, without significant changes over time, and without difference between conditions. Electromyographic activity (iEMG) was lower throughout exercise with 80 rpm (35.6 ± 1.2% and 11.0 ± 1.0% for 40 and 80 rpm, respectively). Similarly, total hemoglobin, determined with near-infrared spectroscopy (NIRS) was 58.0 ± 0.8 (AU) for 40 rpm and 53.0 ± 1.4 (arbitrary units) for 80 rpm, from 30th min onwards (P < 0.05), an indication of lower leg blood volume during the faster pedal rate condition. Thermal status (rectal and mean skin temperature), blood and plasma volume changes, blood lactate concentration, muscle oxygenation (NIRS signal) and the rate of perceived exertion were similar in the two trials. It seems that muscle pump is not an important factor for the development of CV_drift during cycling, at least under the present experimental conditions.     

Endurance enhancement related to the human angiotensin I-converting enzyme I-D polymorphism is not due to differences in the cardiorespiratory response to training

Human physical performance is strongly influenced by genetic factors. We have previously reported that the I variant of the human angiotensin I-converting enzyme (ACE) gene is associated with greater endurance performance in mountaineers and Olympic runners and improved performance in army recruits. In this study we examined whether this effect is mediated by improvements in cardiovascular fitness with training in 58 army recruits homozygous for the insertion (I, ACE genotype II) or deletion (D, ACE genotype DD) allele. A submaximal and maximal exercise protocol was used to calculate both the heart rate/oxygen uptake ( ) relationship and changes in maximal oxygen uptake ( ), respectively. There was no significant intergroup difference in at baseline (P=0.19) or after training (P=0.22). There was no difference between genotypes with training in the heart rate/ elevation (P=0.79 for the mean difference in mean adjusted heart rates). However, at all exercise intensities in the submaximal test was lower for all subjects after training and at 80 W the reduction in was greater for the II subjects compared to DD subjects [mean(SEM)] [1.6 (0.27) and 0.68 (0.27) ml kg^–1 min^–1, respectively; P=0.02 for mean difference]. The I/D polymorphism may play a role in enhanced endurance performance but this is not mediated by differences in or the heart rate/ relationship in response to training. Electronic Publication