Effects of Altering Pedal Cadence on Cycling Time-Trial Performance
G. Watson T. Swensen
Our purpose was to examine the effects of altering cadence on 5mile (8.045 km) time-trial (TT) performance in well-trained amateur male cyclists. Twelve cyclists (mean [SD] age: 24 [4] y; body mass: 70.9 [5.9] kg; and V˙O2max: 4.56 [0.52] L · min–1) rode three 5-mile TT. The first was at their freely chosen or preferred cadence (PC); the other two, high cadence (HC; PC + 10.8 %) and low cadence (LC; PC – 9.2 %), were randomly assigned and completed in a counterbalanced crossover design. Subjects rode their own bicycles, fitted with a power meter, and attached to a windload simulator. Practice sessions were completed 2 d prior to each TT. Cadences for PC, LC, and HC were 92 (2), 83 (6), 101 (6) rpm, respectively; they were also significantly different from
Introduction To maximize velocity, cyclists typically compete with a cadence between 80 and 105 revolutions per minute (rpm) [9,11, 20]. At various times in a race, they use different cadence strategies to sustain maximal velocity, sometimes pedaling quickly with low force or slowly with high force [16]. The various cadence strategies used by cyclists elicit different physiological responses. Pedal force, for example, is lower at 105 rpm than 90 rpm in amateur cyclists at 200 W (70.7 to 75.8 % V˙O2max) for 40 s and 5 min [23]. Similarly, myoelectrical and EMG activity is lower at 100 rpm than 80 rpm in professional cyclists at 366 W (92 % V˙O2max) for 6 min [14] or in subjects from a mixture of athletic backgrounds at 400 W for 60 s [18], indicat-
each other (p < 0.05). LC was 2.5 % faster than HC and more economical than HC and PC (66 [3], 69 [2], 71 [4 W · L–1O2 · min–1, respectively) (p ≤ 0.05). LC heart rate and ventilatory efficiency (V˙E/ V˙O2-ratio) were lower than PC counterparts, while LC and HC minute ventilation (V˙E) were less than PC V˙E (p < 0.05). LC may be the optimal cadence for 5 mile TT in well-trained amateur male cyclists because LC was the most economical, was faster than HC, resulted in the greatest proportion of fastest times (58 % vs. 25 % and 17 % for PC and HC, respectively), and elicited less cardiorespiratory strain than PC.
Training & Testing
Abstract
Key words Bicycling · pedaling · power · velocity · physiology
ing less type II motor unit activation [17], or conversely, greater utilization of the more economical and fatigue resistant type I myofibers at these power outputs. As a consequence of reducing pedal force and type II myofiber activation, high cadences lower muscle stress [19, 23]. They also slow glycogen depletion [1], improve cycling efficiency [4,14, 21], and enhance muscle blood flow, which may increase O2 and substrate delivery, as well as lactate clearance [9]. Collectively, the aforementioned data suggest that a high cadence-low force strategy could improve cycling performance. The adoption of a high cadence-low force strategy, however, is not without potential physiological cost, as higher cadences are generally less economical [5, 9,16]. For instance, V˙O2 is lower at 80 rpm than 100 rpm in amateur and national elite level cyclists
Affiliation Department of Exercise and Sport Sciences, Ithaca College, Ithaca, NY, USA Correspondence Greig Watson · Department of Kinesiology · University of Connecticut · Storrs · CT 06269 · USA · Phone: + 86 04 86 26 49 · E-mail:
[email protected] Accepted after revision: March 8, 2005 Bibliography Int J Sports Med © Georg Thieme Verlag KG · Stuttgart · New York · DOI 10.1055/s-2005-865654 · Published online 2005 · ISSN 0172-4622
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at 300 W for 3 min and 350 W for 8 min, respectively. Professional cyclists, however, produce higher V˙O2 when using a low (60 rpm) versus high cadence (100 rpm) [14], but have considerably higher economy and efficiency during high power output (> 350 W) compared to amateur and well trained cyclists [12,13]; thus it is essential to differentiate between professional and amateur cyclists. At best, for amateur cyclists, the increased cost of cycling at higher cadences may limit or completely offset the theoretical performance gains incurred by adopting this pedaling strategy. At worse, the increased cost of cycling at higher cadences could decrease performance.
Training & Testing
Whereas numerous studies have examined the physiological responses to various cadence strategies, none have determined if these strategies alter performance. Our primary purpose, therefore, was to examine how altering pedal cadence from a cyclist’s preferred cadence affects performance in well-trained amateur cyclists during a 5-mile time-trial (TT).
Materials and Methods Subjects Twelve well-trained male amateur cyclists volunteered to participate. The mean (SD) age, weight, and height of the subjects were 24 (4) y, 70.9 (5.9) kg, and 180 (6) cm, respectively. Subjects had cycle trained regularly for 5.0 (2.1) y previous to the study and were “in training” during the testing period. The study had university ethical committee approval, and each subject gave written consent after being informed about the nature of the experiment and the possible risks.
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Experimental design Each subject reported to the laboratory on seven occasions over a 4-wk period. V˙O2max was measured during the first visit; each subject then reported to the lab twice a wk for the next 3 wk. These biweekly meetings included a familiarization session, and 48 h later, a 5-mile (8.045 km) TT. The TT were conducted at the same time of day each week to avoid circadian fluctuations in performance [18]. During the first week of the 3 biweekly meetings, subjects rode at their freely chosen or preferred cadence (PC). In a counterbalanced cross-over design, 6 subjects completed the low cadence treatment (LC: PC-10%) and 6 subjects completed the high cadence treatment (HC: PC+ 10%) during week 2; subjects were randomly assigned to these initial treatments. In week 3, the opposite cadence treatment was completed by each subject. V˙O2max test On arriving at the laboratory, the subject’s nude body mass was determined (Balance scale, Detecto, WEBB City, MO, U.S.A.). They then completed a self-selected warm-up on a cycle ergometer (Monark, Model 834 e, Varberg, Sweden) fitted with racing handlebars and the subject’s pedal system. The initial test workload was 160 W, which was increased by 40 W every two min until volitional exhaustion or the prescribed cadence of 80 rpm was not maintained. Peak power output (PPO) was calculated using the following equation: PPO (W) = Wfinal + [(t/120 s) · 40 W], where Wfinal is the last workload in W reached but not necessarily completed for 120 seconds, t is the time the last workload was mainWatson G, Swensen T. Cadence and Cycling Performance … Int J Sports Med
tained, 120 is the duration of each workload, in seconds, and 40 is the wattage difference between consecutive workloads. To reduce thermal stress, subjects were fan cooled during this and all subsequent tests. V˙O2 and V˙E were measured throughout the test (Parvo Medics, Salt Lake City, UT, USA); rating of perceived exertion (RPE) using the category ratio scale [3] and heart rate via telemetry (Polar Instruments Inc., Oulu, Finland) were measured in the final 10 s of each stage. Immediately after volitional exhaustion had been reached, 3 successive 25-µl blood samples were collected from one fingertip puncture for triplicate analysis of blood lactate (YSI 1500 Sports Tester, Yellow Springs, OH, USA, calibrated according to the manufacturer’s guidelines). Samples were analyzed immediately, and in order of collection. Measurement of the ambient temperature, humidity, and pressure was made during all tests using an electronic weather station (Perception II, Davis Instruments, Hayward, CA, USA). Bike setup During all familiarization sessions and TT, the subjects cycled in the laboratory on their own bicycles, which were attached to a Kreitler windload simulator that was equipped with a Killer Headwind resistance unit (Kreitler Rollers Inc., Ottawa, KS, USA). The headwind unit was set to one quarter open, which closely approximates road conditions [22]. A rear wheel that contained a power meter (Tune Power∼Tap, Cambridge, MA, USA) and the subject’s cassette (cogs or gears) was fitted to the bike prior to attaching it to the windload simulator. The subject’s cassette was used to maintain gear ratio familiarity and avoid chain/cog incompatibility. Rear tire pressure was standardized to 100 psi, and the power meter torque was zeroed in accordance to the manufacturer’s guidelines. Power∼Tap power measurements have been shown to be approximately 2.5 ± 0.5 % lower compared to a dynamic calibration rig and are stable across an 11-month racing season [7]. Familiarization sessions Approximately 48 h prior to each TT, subjects rode three 10-min intervals at the cadence they were assigned for that week. These intervals followed a standardized self-selected warm-up that was used by the subject for all familiarization and TT sessions. Intervals were separated by 10 min of active rest (pedaling at a self-selected load below 200 W). Heart rate, V˙O2, and RPE were measured as previously described, while the power meter recorded cadence and power output. These sessions were an opportunity for the subject to familiarize himself with each cadence while riding on the windload simulator and to establish a preferred gear ratio for the start of the upcoming TT. Time-trials On arriving at the laboratory the subjects’ nude body mass was measured, as previously described. Subjects then completed their standardized warm-up, which was followed by a “rollout test”. The rollout test was performed to increase the reliability of the power measurement at a set cadence by standardizing average power recorded over 1 min to ± 4 W. It was previously determined that error can result from differences in the tightness of the power meter wheel against the roller of the windload simulator; this tightness is altered by a retaining bolt on the simulator. If the desired power output was not achieved on the first rollout test, the tire/roller resistance was altered using the retaining
bolt and the test was repeated until the desired power output was achieved. The TT began immediately after the rollout test. The clock was started once the subject, using a rolling start, attained the target cadence. The power meter measured velocity, power output, and cadence. Heart rate and RPE were recorded every other minute, while V˙O2 and V˙E were measured throughout the TT as previously described. Immediately after the TT, subjects remained stationary while blood samples were collected for blood lactate determination as previously described.
Condition PC (92 ± 6) TT time (s)*b
LC (83 ± 6)
HC (101 ± 6)
747 ± 63
736 ± 63
754 ± 59
Velocity (miles · hr–1)*b
39.05 ± 3.35
39.58 ± 3.33
38.62 ± 3.06
Power output (W)**c
290 ± 33
297 ± 30
278 ± 28
W · rev–1*a
3.1 ± 0.4
3.6 ± 0.5
2.7 ± 0.4
V˙O2 (L · min–1)
4.23 ± 0.49
4.21 ± 0.38
4.19 ± 0.37
V˙E (L · min–1)*b
105 ± 15
99 ± 14
101 ± 14
V˙E/V˙O2*b
24.9 ± 2.4
23.5 ± 1.9
24.0 ± 2.4
69 ± 2
71 ± 4
67 ± 3
180.6 ± 8.4
175.8 ± 11.4
178.2 ± 9.4
13.2 ± 3.1
12.1 ± 3.2
12.3 ± 2.8
44 ± 4
43 ± 4
45 ± 6
Economy (W · LO2 · min–1)*c Heart rate (bpm)*d Blood lactate (mmol · L–1) f (breaths · min–1)
PC = preferred cadence, LC = low cadence, HC = high cadenceTT = time-trial, ˙O2 = rate of oxygen uptake, V ˙E = W · rev–1 = average power per pedal revolution, V ˙O2 = ventilatory efficiency, f = breathing frequency. ˙ E/V minute ventilation, V * p ≤ 0.05 and ** p < 0.01 for Treatment main effect. a, b, c and d are post-hoc analysis where a = difference between all conditions, b = between LC and HC, c = between PC and HC, and LC and HC, and d = between PC and LC. The alpha level was set at 0.5
Data analysis Descriptive statistics (mean and standard deviation) were calculated for all variables. A 2 × 3 ANOVA (Group × Treatment) with repeated measures on the 2nd factor was completed for: body mass, laboratory atmospheric conditions, rollout test power output and cadence, and for TT cadence, velocity, time, power output, economy (calculated by dividing average power output [W] by average V˙O2 [L · min–1]), blood lactate, heart rate, V˙O2, V˙E, V˙E/ V˙O2 ratio, power per pedal revolution (W · rev–1), breathing frequency, and RPE. The between-subjects factor Group compared results from the subjects that rode the HC TT first with those that rode the LC TT first. The within-subjects factor Treatment compared individual responses to the PC, LC, and HC TT. For all statistical tests, the alpha level was set at 0.05. The Tukey (HSD) post hoc test was used to determine the location of any withinsubject differences.
Time-trial test results TT results are shown in Table 1. No order effects were observed between HC and LC. On average, the LC TT was 2.5 % faster than the HC TT (p ≤ 0.05); the mean reduction in time between LC and HC was 17.8 (26.9) s. Seven subjects (58 % of the subject cohort) were fastest using LC, compared to three (25 %) using PC, and two (17 %) using HC. LC was the most economical (p ≤ 0.05) because it produced 6.0 and 2.8 % more power per liter of oxygen consumed each minute compared to HC and PC, respectively. Heart rate was 3.4 % lower during LC (p ≤ 0.05) than PC, and minute ventilation (V˙E) was lower during LC and HC compared to PC (p ≤ 0.05) by 6 and 4.5 %, respectively. The V˙E/V˙O2 ratio was 5.8 % lower during the LC TT than HC TT (p ≤ 0.05). The LC produced 15 % more power per pedal revolution (W · rev–1) than PC (p ≤ 0.05), and PC produced 14 % more W · rev–1 than HC (p ≤ 0.05). There were no other significant differences.
Results
Discussion
The subjects’ V˙O2max and peak power output (PPO) were 64.3 (5.0) ml · kg–1 · min–1 and 364 (33) W, respectively. There were no differences in body mass and ambient temperature, pressure, and humidity in the laboratory across the study. The power meter was also reliably calibrated for each TT, as there was no difference in the cadence and power output maintained during the rollout tests. The average TT cadences were significantly different from each other (p ≤ 0.05). PC, LC, and HC averaged 92 (6), 83 (6), and 101 (6) rpm, respectively, so the actual difference in cadence between PC and LC and PC and HC was 10.8 % and 9.2 %, respectively.
Our purpose was to examine how altering pedal cadence from preferred cadence (PC) affects 5-mile TT performance in welltrained amateur cyclists. We found TT time was shortest with a pedal rate that was ∼ 10% lower than the PC compared to one that was ∼ 10% higher. Although low cadence (LC) did not significantly improve TT time compared to PC, 9 out of the 12 cyclists went faster during the LC than PC TT. In addition, LC was more economical than PC and high cadence (HC), and LC elicited less cardiorespiratory stress than PC. At a low-medium power output (< 300 – 350 W), lower cadences are more economical than higher cadences, as V˙O2 increases Watson G, Swensen T. Cadence and Cycling Performance … Int J Sports Med
Training & Testing
To avoid the confounding effects of pacing, subjects had no knowledge of velocity or time during the TT. However, they were told when they had reached each mile, 4.5 miles, 4.75 miles, and 4.9 miles, or at any other time during the TT if they indicated the need to know by raising a finger. Similarly the subjects had no visible knowledge of cadence, but received constant verbal feedback as to their current cadence and average cadence. Subjects were free to alter the gear ratio at anytime while riding the TT, but had to maintain the required pedal cadence. They were also informed not to alter their racing position during the study, because altering position affects power output, potentially biasing the data. Subjects were instructed to rest the day before each TT and to maintain a similar level of activity between weeks. Diet was not controlled, but subjects were asked to keep a similar nutritional regimen during the study.
Table 1 Mean and standard deviation for selected variables by Condition
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with cadence in a linear [16], parabolic [2, 6], and exponential [5, 9] fashion. The parabolic relationship lessens as power output increases, but it is still significant at 300 W [2], which is similar to the TT power output of our subject cohort. Although altering cadence did not change V˙O2 in this study, it did change power output, which decreased as cadence increased; consequently, LC was the most economical cadence, followed by PC and HC, respectively. This finding conforms to observations that at 300 W, in cyclists with a relative V˙O2max similar to the one in our subject cohort (∼ 65 ml · kg–1 · min–1), the most economical cadence is in the range of 80 [6] to 90 rpm [9,11].
Training & Testing 4
The reduced power output at the same V˙O2 during the HC vs. LC TT may be partially explained by the additional oxygen cost of lifting the legs more often [8], the effort of which does not increase propulsive power [24] and reduces the force effectiveness index [19], thereby possibly lowering pedaling efficiency [21]. Since higher cadences require greater O2 consumption for a given power output below 300 – 350 W [5, 9], it is unlikely that our subjects could have cycled faster during HC without first becoming more fit or skilled at pedaling, as the average V˙O2 during all TT was approximately 93 % of V˙O2max, which was sustained for 12.4 (0.1) min at 94 % of HRmax, and the subsequent post-TT lactate concentration was 12.5 (2.7) mM. In short, our cyclists were at or near their maximal sustainable V˙O2 for that distance. Our TT velocity data imply that the theoretical benefits of using HC, such as reduced muscular stress [10], improved muscle blood flow [8,11], or slowed glycogen utilization [1] were not the primary determinates for short TT performance under our experimental conditions. Instead, V˙O2 or effective application of pedal forces or some combination of these two factors was the probable performance determinate. Perhaps only those cyclists who have the aerobic power to sustain 400 W, that is, professional cyclists can benefit from using a cadence higher than PC as suggested by myoelectrical or EMG data. At 300 W, for example, the EMG minimum for cycling specific muscles occurs at 86 ± 7.6 rpm, whereas at 366 to 400 W, the nadir occurs near 100 rpm [15]. A ± 10% change in cadence from PC did not alter whole body RPE. Most subjects, however, remarked that LC caused the greatest “leg fatigue”, probably reflecting the higher force produced per pedal revolution at this cadence, a consequence of a high forcelow cadence strategy. Despite the difference in pedal force per rev across the TT, there was no difference in blood lactate. In contrast to their perception of effort during LC, most subjects said that HC produced the greatest “lung or central fatigue”, a consequence of a low force-high cadence strategy. Although HC and LC breathing frequency and minute ventilation (V˙E) were similar, the ventilatory equivalent of oxygen (V˙E/V˙O2), an estimate of ventilatory efficiency, was 5.8 % lower (p ≤ 0.05) during LC than HC, which may partially explain the subjects’ feeling of “lung fatigue”. The manipulation of cadence in this study was modest (± 10% of PC) and based on each subject’s PC. Changes in cadence were based on PC so that we could be assured the variable was actually manipulated. Had we decided that HC was 100 rpm, for example, any subject whose PC was 100 rpm would not have completed a Watson G, Swensen T. Cadence and Cycling Performance … Int J Sports Med
HC TT. In short, changing cadence relative to PC meant that each subject had a true LC and HC TT relative to a PC TT and that the cadence manipulations were of similar magnitude. Altering cadence from PC also required the subjects to complete the PC TT first, a limitation of the study. There was, however, no order effect between the LC and HC TT that followed the PC TT, suggesting that this limitation was minimal at best. The modest change in cadence in this study was also purposeful. Larger changes would have resulted in cadences well outside most subjects’ comfort zone, potentially confounding the data. To examine the effects of larger changes in cadence on TT performance in well- to highly-trained cyclists would probably require a training study of sufficient duration to stimulate meaningful adaptations, a bigger sample size, and a significant alteration in the cyclists’ inseason or late pre-season exercise regimen, factors that reduce the practicality of such a study.
Conclusion We found that TT time using a low cadence was significantly faster than a high cadence. Furthermore, although the difference in TT time between the low cadence and preferred cadence was statistically insignificant, nine subjects rode faster during the low cadence TT than the preferred cadence TT. Additionally, the low cadence was more economical than the preferred cadence and high cadence, elicited a lower heart rate and minute ventilation than the preferred cadence, and resulted in the greatest proportion of the fastest times. Collectively, these data show that a lower cadence optimized 5-mile TT performance in well-trained amateur cyclists under our experimental conditions.
Acknowledgements A section of this data was presented at the American College of Sports Medicine 2002 Conference (Med Sci Sports Exerc 2002; 34: S26).
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