Energy cost and efficiency of riding aerodynamic bicycles

Influence of wind speed and road grade on the estimation of drag area in cycling

The estimation of aerodynamic drag in cycling through road tests has the advantage of considering actual cycling conditions. The main drawback is that its accuracy depends on factors of the testing scenario as the wind speed v w and the road grade θ . For that reason, the effect of v w and θ on the estimation of drag area (C D A ) was studied. Numerical and experimental approaches were combined. The numerical approach investigated the sensitivity of C D A to v w and θ perturbations. The experimental approach analysed the effect of including or not v w and θ on the identification of C D A by comparing the changes in the prediction of power delivered. It was found that disregarding small values of v w (e.g. 0.5 m/s) and θ (e.g. gradient of 0.05%) leads to errors in the estimation of C D A of around 10%, referred to the actual value. It was also obtained that the average error of the power prediction when considering v w and θ for the identification of the parameters is about 4.4% and about 25.5% when v w and θ are neglected. It is concluded that including v w and θ data reduces the error on the identification of C D A through outdoor road experiments.

Changes in Sex Difference in Time-Limited Ultra-Cycling Races from 6 Hours to 24 Hours

Background and objective: Existing research shows that the sex differences in distance-limited ultra-cycling races decreased with both increasing race distance and increasing age. It is unknown, however, whether the sex differences in time-limited ultra-cycling races will equally decrease with increasing race distance and age. This study aimed to examine the sex differences regarding performance for time-limited ultra-cycling races (6, 12, and 24 h). Methods: Data were obtained from the online database of the Ultra-Cycling Marathon Association (UMCA) of time-limited ultra-cycling races (6, 12, and 24 h) from the years 1983–2019. A total of 18,241 race results were analyzed to compare cycling speed between men and women by calendar year, age group (<29; 30–39; 40–49; 50–59; 60–69; >70 years), and race duration. Results: The participation of both men (85.1%) and women (14.9%) increased between 1983 and 2019. The age of peak performance was between 40 and 59 years for men and between 30 and 59 years for women. Between 2000 and 2019, more men (63.1% of male participants and 52.2% of female participants) competed in 24 h races. In the 24 h races, the sex difference decreased significantly in all age groups. Men cycled 9.6% faster than women in the 12 h races and 4% faster in the 24 h races. Both women and men improved their performance significantly across the decades. Between 2000 and 2019, the improvement in the 24 h races were 15.6% for men and 21.9% for women. Conclusion: The sex differences in cycling speed decreased between men and women with increasing duration of ultra-cycling races and with increasing age. Women showed a greater performance improvement than men in the last 20 years. The average cycling speed of men and women started to converge in the 24 h races.

Optimizing the Team for Required Power During Track-Cycling Team Pursuit

Purpose: Since the aim of the men’s team pursuit in time-trial track cycling is to accomplish a distance of 4000 m as fast as possible, optimizing aerodynamic drag can contribute to achieving this goal. The aim of this study was to determine the drafting effect in second, third, and fourth position during the team pursuit in track cycling as a function of the team members’ individual frontal areas in order to minimize the required power. Method: Eight experienced track cyclists of the Dutch national selection performed 39 trials of 3 km in different teams of 4 cyclists at a constant velocity of 15.75 m/s. Frontal projected areas were determined, and together with field-derived drag coefficients for all 4 positions, the relationships between frontal areas of team members and drag fractions were estimated using generalized estimating equations. Results: The frontal area of both the cyclist directly in front of the drafter and the drafter himself turned out to be significant determinants of the drag fraction at the drafter’s position (P < .05) for all 3 drafting positions. Predicted required power for individuals in drafting positions differed up to 35 W depending on team composition. For a team, a maximal difference in team efficiency (1.2%) exists by selecting cyclists in a specific sequence. Conclusion: Estimating required power for a specific team composition gives insight into differences in team efficiency for the team pursuit. Furthermore, required power for individual team members ranges substantially depending on team composition.

The physiology of submaximal exercise: The steady state concept

The steady state concept implies that the oxygen flow is invariant and equal at each level along the respiratory system. The same is the case with the carbon dioxide flow. This condition has several physiological consequences, which are analysed. First, we briefly discuss the mechanical efficiency of exercise and the energy cost of human locomotion, as well as the roles played by aerodynamic work and frictional work. Then we analyse the equations describing the oxygen flow in lungs and in blood, the effects of ventilation and of the ventilation - perfusion inequality, and the interaction between diffusion and perfusion in the lungs. The cardiovascular responses sustaining gas flow increase in blood are finally presented. An equation linking ventilation, circulation and metabolism is developed, on the hypothesis of constant oxygen flow in mixed venous blood. This equation tells that, if the pulmonary respiratory quotient stays invariant, any increase in metabolic rate is matched by a proportional increase in ventilation, but by a less than proportional increase in cardiac output.

Energetic Assessment of the Nonexercise Activities under Free-Living Conditions

Nonexercise activities (NAs) are common types of physical activity in daily life and critical component in energy expenditure. However, energetic assessment of NA, particularly in free-living subjects, is a technical challenge. In this study, mechanical modeling and portable device were used to evaluate five common types of NA in daily life: sit to stand, lie to sit, bowing while standing, squat, and right leg over left. A human indirect calorimeter was used to measure the activity energy expenditure of NA. Mechanical work and mechanical efficiency of NA were calculated for mechanical modeling. Thirty-two male subjects were recruited for the study (20 subjects for the development of models and 12 subjects for evaluation of models). The average (mean ± SD) mechanical work of 5 NAs was 2.31 ± 0.50, 2.88 ± 0.57, 1.75 ± 0.55, 3.96 ± 1.25, and 1.25 ± 0.51 J/kg·m, respectively. The mean mechanical efficiencies of those activities were 22.0 ± 3.3%, 26.5 ± 5.1%, 19.8 ± 3.7%, 24.0 ± 5.5%, and 26.3 ± 5.5%. The activity energy expenditure estimated by the models was not significantly different from the measurements by the calorimeter (p > 0.05) with accuracies of 102.2 ± 20.7%, 103.7 ± 25.8%, 105.6 ± 14.6%, 101.1 ± 28.0%, and 95.8 ± 20.7%, respectively, for those activities. These findings suggest that the mechanical models combined with a portable device can provide an alternative method for the energetic analysis of nonexercise activities under free-living condition.

Maximal aerobic power and anaerobic capacity in cycling across the age spectrum in male master athletes

PURPOSE

We analyzed the best performance times of master cycling athletes in the 200-3000 m track competitions to estimate the decay of maximal aerobic power (MAP) and anaerobic capacity (AnS) with aging.

METHODS

In various decades of age (30-80 years), MAP and AnS were estimated using an iterative procedure as the values that minimize the difference between: (1) the metabolic power ([Formula: see text]) necessary to cover a given distance (d) in the time t and; (2) the maximal metabolic power ([Formula: see text]) maintained at a constant level throughout the competition.

RESULTS

MAP started decreasing at 45 years of age. Thereafter, it showed an average percent rate of decrease of about 16 % for decade, as previously shown in other classes of master athletes. In addition, AnS seemed to decay by about 11 % every 10 years from the second part of the fifth decade.

CONCLUSIONS

The decay of MAP occurred in spite of the active lifestyle of the subjects and it may be attributed to the progressive impairment of maximal O2 delivery and/or of peripheral O2 utilization. The loss of AnS might derive from the progressive loss of muscle mass occurring after the fifth decade of life, to the progressive qualitative deterioration of the anaerobic energy yielding pathways or to the lower capacity of MN recruitment during maximal efforts. The proposed approach may be applied to other types of human locomotion of whom the relationship between performance t and [Formula: see text] is known.

Field-measured drag area is a key correlate of level cycling time trial performance

Drag area (Ad ) is a primary factor determining aerodynamic resistance during level cycling and is therefore a key determinant of level time trial performance. However, Ad has traditionally been difficult to measure. Our purpose was to determine the value of adding field-measured Ad as a correlate of level cycling time trial performance. In the field, 19 male cyclists performed a level (22.1 km) time trial. Separately, field-determined Ad and rolling resistance were calculated for subjects along with projected frontal area assessed directly (AP ) and indirectly (Est AP ). Also, a graded exercise test was performed to determine [Formula: see text] peak, lactate threshold (LT), and economy. [Formula: see text] peak ([Formula: see text]) and power at LT were significantly correlated to power measured during the time trial (r = 0.83 and 0.69, respectively) but were not significantly correlated to performance time (r = - 0.42 and -0.45). The correlation with performance time improved significantly (p < 0.05) when these variables were normalized to Ad . Of note, Ad alone was better correlated to performance time (r = 0.85, p < 0.001) than any combination of non-normalized physiological measure. The best correlate with performance time was field-measured power output during the time trial normalized to Ad (r = - 0.92). AP only accounted for 54% of the variability in Ad . Accordingly, the correlation to performance time was significantly lower using power normalized to AP (r = - 0.75) or Est AP (r = - 0.71). In conclusion, unless normalized to Ad , level time trial performance in the field was not highly correlated to common laboratory measures. Furthermore, our field-measured Ad is easy to determine and was the single best predictor of level time trial performance.

Predicting energy expenditure through hand rim propulsion power output in individuals who use wheelchairs

AIM

To examine the relationship between hand rim propulsion power and energy expenditure (EE) during wheelchair wheeling and to investigate whether adding other variables to the model could improve on the prediction of EE.

METHODS

Individuals who use manual wheelchairs (n=14) performed five different wheeling activities in a wheelchair with a PowerTap power meter hub built into the right rear wheel. Activities included wheeling on a smooth, level surface at three different speeds (4.5, 5.5 and 6.5 km/h), wheeling on a rubberised track at one speed (5.5 km/h) and wheeling on a sidewalk course that included uphill and downhill segments at a self-selected speed. EE was measured using a portable indirect calorimetry system. Stepwise linear regression was performed to predict EE from power output variables. A repeated-measures analysis of variance was used to compare the measured EE to the estimates from the power models. Bland-Altman plots were used to assess the agreement between the criterion values and the predicted values.

RESULTS

EE and power were significantly correlated (r=0.694, p<0.001). Regression analysis yielded three significant prediction models utilising measured power; measured power and speed; and measured power, speed and heart rate. No significant differences were found between measured EE and any of the prediction models.

CONCLUSION

EE can be accurately and precisely estimated based on hand rim propulsion power. These results indicate that power could be used as a method to assess EE in individuals who use wheelchairs.

A new method to measure rolling resistance in treadmill cycling

The purpose of this study was to evaluate a new method of measuring rolling resistance in treadmill cycling and to establish its sensitivity and reproducibility. One participant was asked to keep a bicycle in equilibrium on a treadmill without pedalling at a constant speed of 5.56 m x s(-1), which was held in place in the front by a dynamometer. For each condition, the method consisted of 11 measurements of the force required to hold the cycle at different treadmill slopes (0-10%, increment 1%). The coefficient of rolling resistance was calculated based on the forces applied to the bicycle in equilibrium. To test the sensitivity of the method, the bicycle was successively equipped with three tyre types (700 x 28, 700 x 23, 700 x 22) and inflation pressure was set at 150, 300, 600, 900, and 1100 kPa. To test the reproducibility of the method, a second experimenter repeated all measurements done with the 700 x 23 tyres. The method was sensitive enough to detect an effect of both tyre type and inflation pressure (P < 0.001: two-way ANOVA). The measurement of the coefficient of rolling resistance by two separate experimenters resulted in a small bias of 0.00029 (95% CI, -0.00011 to 0.00068). In conclusion, the new method is sensitive and reliable, as well as being simple and affordable.

Influence of exercise on nutritional requirements

There is no consensus on the best diet for exercise, as many variables influence it. We propose an approach that is based on the total energy expenditure of exercise and the specific macro- and micronutrients used. di Prampero quantified the impact of intensity and duration on the energy cost of exercise. This can be used to determine the total energy needs and the balance of fats and carbohydrates (CHO). There are metabolic differences between sedentary and trained persons, thus the total energy intake to prevent overfeeding of sedentary persons and underfeeding athletes is important. During submaximal sustained exercise, fat oxidation (FO) plays an important role. This role is diminished and CHO's role increases as exercise intensity increases. At super-maximal exercise intensities, anaerobic glycolysis dominates. In the case of protein and micronutrients, specific recommendations are required. We propose that for submaximal exercise, the balance of CHO and fat favors fat for longer exercise and CHO for shorter exercise, while always maintaining the minimal requirements of each (CHO: 40% and fat: 30%). A case for higher protein (above 15%) as well as creatine supplementation for resistance exercise has been proposed. One may also consider increasing bicarbonate intake for exercise that relies on anaerobic glycolysis, whereas there appears to be little support for antioxidant supplementation. Insuring minimal levels of substrate will prevent exercise intolerance, while increasing some components may increase exercise tolerance.

An analysis of performance in human locomotion

This paper reports an analysis of the principles underlying human performances on the basis of the work initiated by Pietro Enrico di Prampero. Starting from the concept that the maximal speed that can be attained over a given distance with a given locomotion mode is directly proportional to the maximal sustainable power and inversely proportional to the energy cost of locomotion, we discuss the maximal powers (and capacities) of anaerobic (lactic and alactic) and aerobic metabolisms and the factors that limit them, and the factors affecting the energy cost of various locomotion modes. Special attention is given to the role of air resistance and frictional forces. Finally, computation of performance speed is discussed along the approach originally developed by di Prampero.

The energetics of cycling on Earth, Moon and Mars

From 1885, technological improvements, such as the use of special metal alloys and the application of aerodynamics principles, have transformed the bicycle from a human powered heavy transport system to an efficient, often expensive, object used to move not only in our crowded cities, but also in leisure activities and in sports. In this paper, the concepts of mechanical work and efficiency of cycling together with the corresponding metabolic expenditure are discussed. The effects of altitude and aerodynamic improvements on sports performances are also analysed. A section is dedicated to the analysis of the maximal cycling performances. Finally, since during the next decades the return of Man on the Moon and, why not, a mission to Mars can be realistically hypothesised, a section is dedicated to cycling-based facilities, such as man powered short radius centrifuges, to be used to prevent cardiovascular and skeletal muscle deconditioning otherwise occurring during long-term exposure to microgravity.

Energy cost and mechanical efficiency of riding a human-powered recumbent bicycle

When dealing with human-powered vehicles, it is important to quantify the capability of converting metabolic energy in useful mechanical work by measuring mechanical efficiency. In this study, net mechanical efficiency (eta) of riding a recumbent bicycle on flat terrain and at constant speeds (v, 5.1-10.0 m/s) was calculated dividing mechanical work (w, J/m) by the corresponding energy cost (C(c), J/m). w and C(c) increased linearly with the speed squared: w = 9.41 + 0.156 . v(2); C(c) = 39.40 + 0.563 . v(2). eta was equal to 0.257 +/- 0.0245, i.e. identical to that of concentric muscular contraction. Hence, i) eta seems unaffected by the biomechanical arrangement of the human-vehicle system; ii) the efficiency of transmission seems to be close to 100%, suggesting that the particular biomechanical arrangement does not impair the transformation of metabolic energy in mechanical work. When dealing with human-powered vehicles, it is important to quantify mechanical efficiency (eta) of locomotion. eta of riding a recumbent bicycle was calculated dividing the mechanical work to the corresponding energy cost of locomotion; it was practically identical to that of concentric muscular contraction (0.257 +/- 0.0245), suggesting that the power transmission from muscles to pedals is unaffected by the biomechanical arrangement of the vehicle.

Electromyographic analysis of pedaling: a review

Although pedaling is constrained by the circular trajectory of the pedals, it is not a simple movement. This review attempts to provide an overview of the pedaling technique using an electromyographic (EMG) approach. Literature concerning the electromyographic analysis of pedaling is reviewed in an effort to make a synthesis of the available information, and to point out its relevance for researchers, clinicians and/or cycling/triathlon trainers. The first part of the review depicts methodological aspects of the EMG signal recording and processing. We show how the pattern of muscle activation during pedaling can be analyzed in terms of muscle activity level and muscle activation timing. Muscle activity level is generally quantified with root mean square or integrated EMG values. Muscle activation timing is studied by defining EMG signal onset and offset times that identify the duration of EMG bursts and, more recently, by the determination of a lag time maximizing the cross-correlation coefficient. In the second part of the review, we describe whether the patterns of the lower limb muscles activity are influenced by numerous factors affecting pedaling such as power output, pedaling rate, body position, shoe-pedal interface, training status and fatigue. Some research perspectives linked to pedaling performance are discussed throughout the manuscript and in the conclusion.

Influence of different racing positions on mechanical and electromyographic patterns during pedalling

The aim of this study was to test the hypothesis that, in comparison with standard postures, aero posture (AP) would modify the coordination of lower limb muscles during pedalling and consequently would influence the pedal force production. Twelve triathletes were asked to pedal at an intensity near the ventilatory threshold (VT+Delta20%) and at an intenisty corresponding to the respiratory compensation point (RCP). For each intensity, subjects were tested under three positions: (1) upright posture (UP), (2) dropped posture (DP), and (3) AP. Gas exchanges, surface electromyography and pedal effective force were continuously recorded. No significant difference was found for the gas-exchange variables among the three positions. Data illustrate a significant increase [gluteus maximus (GMax), vastus medialis (VM)] and decrease [rectus femoris (RF)] in electromyography (EMG) activity level in AP compared with UP at RCP. A significant shift forward of the EMG patterns (i.e. later onset of activation) was observed for RF (at VT+Delta20% and RCP), GMax, VL, and VM (at RCP) in AP compared with UP. These EMG changes are closely related to alteration of force profile in AP (higher downstroke positive peak force, lower upstroke negative peak force, and later occurrence of these peaks along the crank cycle).

The Science of Cycling

This review presents information that is useful to athletes, coaches and exercise scientists in the adoption of exercise protocols, prescription of training regimens and creation of research designs. Part 2 focuses on the factors that affect cycling performance. Among those factors, aerodynamic resistance is the major resistance force the racing cyclist must overcome. This challenge can be dealt with through equipment technological modifications and body position configuration adjustments. To successfully achieve efficient transfer of power from the body to the drive train of the bicycle the major concern is bicycle configuration and cycling body position. Peak power output appears to be highly correlated with cycling success. Likewise, gear ratio and pedalling cadence directly influence cycling economy/efficiency. Knowledge of muscle recruitment throughout the crank cycle has important implications for training and body position adjustments while climbing. A review of pacing models suggests that while there appears to be some evidence in favour of one technique over another, there remains the need for further field research to validate the findings. Nevertheless, performance modelling has important implications for the establishment of performance standards and consequent recommendations for training.

Science and cycling: current knowledge and future directions for research

In this holistic review of cycling science, the objectives are: (1) to identify the various human and environmental factors that influence cycling power output and velocity; (2) to discuss, with the aid of a schematic model, the often complex interrelationships between these factors; and (3) to suggest future directions for research to help clarify how cycling performance can be optimized, given different race disciplines, environments and riders. Most successful cyclists, irrespective of the race discipline, have a high maximal aerobic power output measured from an incremental test, and an ability to work at relatively high power outputs for long periods. The relationship between these characteristics and inherent physiological factors such as muscle capilliarization and muscle fibre type is complicated by inter-individual differences in selecting cadence for different race conditions. More research is needed on high-class professional riders, since they probably represent the pinnacle of natural selection for, and physiological adaptation to, endurance exercise. Recent advances in mathematical modelling and bicycle-mounted strain gauges, which can measure power directly in races, are starting to help unravel the interrelationships between the various resistive forces on the bicycle (e.g. air and rolling resistance, gravity). Interventions on rider position to optimize aerodynamics should also consider the impact on power output of the rider. All-terrain bicycle (ATB) racing is a neglected discipline in terms of the characterization of power outputs in race conditions and the modelling of the effects of the different design of bicycle frame and components on the magnitude of resistive forces. A direct application of mathematical models of cycling velocity has been in identifying optimal pacing strategies for different race conditions. Such data should, nevertheless, be considered alongside physiological optimization of power output in a race. An even distribution of power output is both physiologically and biophysically optimal for longer ( > 4 km) time-trials held in conditions of unvarying wind and gradient. For shorter races (e.g. a 1 km time-trial), an 'all out' effort from the start is advised to 'save' time during the initial phase that contributes most to total race time and to optimize the contribution of kinetic energy to race velocity. From a biophysical standpoint, the optimum pacing strategy for road time-trials may involve increasing power in headwinds and uphill sections and decreasing power in tailwinds and when travelling downhill. More research, using models and direct power measurement, is needed to elucidate fully how much such a pacing strategy might save time in a real race and how much a variable power output can be tolerated by a rider. The cyclist's diet is a multifactorial issue in itself and many researchers have tried to examine aspects of cycling nutrition (e.g. timing, amount, composition) in isolation. Only recently have researchers attempted to analyse interrelationships between dietary factors (e.g. the link between pre-race and in-race dietary effects on performance). The thermal environment is a mediating factor in choice of diet, since there may be competing interests of replacing lost fluid and depleted glycogen during and after a race. Given the prevalence of stage racing in professional cycling, more research into the influence of nutrition on repeated bouts of exercise performance and training is required.

The physiological effects of cycling on tandem and single bicycles

OBJECTIVE

The purpose of this field study was to compare the physiological responses from cycling on a tandem road bicycle to those from cycling on a single road bicycle.

METHODS

Nine pairs of experienced, recreational tandem cyclists rode a tandem or their single bicycle for 5 min at each velocity of 19.3, 22.5, 25.8, and 29.0 kph on a flat, paved surface. Heart rate (HR), rating of perceived exertion (RPE), and lactic acid (LA) data were collected after each interval.

RESULTS

Riding a tandem resulted in lower HR, RPE, and LA mean values across the four velocities compared to the single bicycle. Mean (SD) HR, RPE, and LA for tandem and single bicycles were 126 (20.7) v 142 (20.1) bpm, 10.1 (1.7) v 11.3 (2.6), and 1.46 (1.0) mM/L v 2.36 (1.7) mM/L, respectively. No position differences were observed between the captain and stoker (front and rear positions) when both were on the tandem. Stokers had significantly lower HR, LA, and RPE values when they rode a tandem compared to a single bicycle. No statistical differences were observed between bicycles for the captains. When on the single bicycle, captains exhibited significantly lower HR, RPE, and LA values than stokers.

CONCLUSION

Cycling on a tandem resulted in lower physiological stress than when cycling at the same velocity on a single bicycle. Cyclists were able to ride from 4.8-8.0 kph faster on a tandem than on a single bicycle at similar physiological stress. Apparently, stokers can add to power output on a tandem without adding significantly to wind resistance.

The 4000-m team pursuit cycling world record: theoretical and practical aspects

Due to constant competition conditions, track cycling can be accurately modeled through physiological and biomechanical means. Mathematical modeling predicts an average workload of 520 W for every team member for a new team pursuit world record. Performance in team pursuit racing is highly dependent on aerobic capacity, anaerobic skills, and aerodynamic factors. The training concept of the 2000 record-breaking team pursuit team was based on unspecific training of these qualities and periodical, short-term recall of previously acquired track specific skills. Aerobic performance was trained through high overall training mileage (29,000-35,000 km.yr-1) with workload peaks during road stage races. Before major track events, anaerobic performance, and track-specific technical and motor skills were improved through discipline-specific track training. Training intensities were monitored through heart rate and lactate field tests during defined track-training bouts, based on previously performed laboratory exercise tests. During pursuit competition, analysis of half-lap split times allowed an estimation of the individual contribution of each rider to the team's performance and thereby facilitated modifications in team composition to optimize race speed. The theoretically predicted performance necessary for a new world record was achieved through careful planning of training and competition schedules based on a concise theoretical concept and the high physiological capacities of the participating athletes.

Modelling human locomotion: applications to cycling

Mathematical models of performance in locomotor sports are reducible to functions of the sort y = f(x) where y is some performance variable, such as time, distance or speed, and x is a combination of predictor variables which may include expressions for power (or energy) supply and/or demand. The most valid and useful models are first-principles models that equate expressions for power supply and power demand. Power demand in cycling is the sum of the power required to overcome air resistance and rolling resistance, the power required to change the kinetic energy of the system, and the power required to ride up or down a grade. Power supply is drawn from aerobic and anaerobic sources, and modellers must consider not only the rate but also the kinetics and pattern of power supply. The relative contributions of air resistance to total demand, and of aerobic energy to total supply, increase curvilinearly with performance time, while the importance of other factors decreases. Factors such as crosswinds, aerodynamic accessories and drafting can modify the power demand in cycling, while body configuration/orientation and altitude will affect both power demand and power supply, often in opposite directions. Mathematical models have been used to solve specific problems in cycling, such as the chance of success of a breakaway, the optimal altitude for performance, creating a 'level playing field' to compare performances for selection purposes, and to quantify, in the common currency of minutes and seconds, the effects on performance of changes in physiological, environmental and equipment variables. The development of crank dynamometers and portable gas-analysis systems, combined with a modelling approach, will in the future provide valuable information on the effect of changes in equipment, configuration and environment on both supply and demand-side variables.

Enhancing cycling performance using an eccentric chainring

PURPOSE AND METHODS

This study was designed to compare the physiological responses and performance of well trained cyclists riding with two different chainring designs, round or eccentric, during a brief and intense cycling exercise: an "all-out" 1-km laboratory test. The eccentrically designed chainring was made of two crank arms sliding into each other, with the inside arm fixed on the center of the arm of a circular chainring and the outside arm sliding along the inside and revolving around an elliptical cam. This design increases crank arm length at the downstroke and decreases it during the upstroke, thus increasing and decreasing the torque. In terms of the chainring's revolution, the crank arm length at 0 degrees and 180 degrees is similar to the arm length of circular chainrings (175 mm). However, during the downstroke (0-180 degrees ), it increases to its maximum length of 200 mm at 90 degrees and then returns to its original length of 175 mm at 180 degrees. During the upstroke, it decreases to a minimum length of 150 mm at 270 degrees and then increases to 175 mm at 360 degrees. Eleven cyclists performed an all-out 1-km laboratory test using each chainring. The study was conducted over two consecutive weeks with the order of chainring use randomized. During all trials, ventilatory data were collected every minute using an automated breath-by-breath system. Heart rate was measured using a telemetry system.

RESULTS

None of the cardiorespiratory variables showed significant differences between chainring trials. Performance, however, was significantly improved using the eccentric design (64.25 +/- 1.05 vs 69.08 +/- 1.38 s, P < 0.004, with the eccentric and the round design, respectively).

CONCLUSION

We concluded that the eccentric chainring significantly improved the cycling performance during an all-out 1-km test. Further testing with indoor cycling specialists performing on a velodrome would be helpful to define the maximal possibilities of such a chainring.

Scientific approach to the 1-h cycling world record: a case study

The purpose of this study was to describe the physiological and aerodynamic characteristics and the preparation for a successful attempt to break the 1-h cycling world record. An elite professional road cyclist (30 yr, 188 cm, 81 kg) performed an incremental laboratory test to assess maximal power output (W(max)) and power output (W(OBLA)), estimated speed (V(OBLA)), and heart rate (HR(OBLA)) at the onset of blood lactate accumulation (OBLA). He also completed an incremental velodrome (cycling track) test (VT1), during which V(OBLAVT1) and HR(OBLAVT1) were measured and W(OBLAVT1) was estimated. W(max) was 572 W, W(OBLA) 505 W, V(OBLA) 52.88 km/h, and HR(OBLA) 183 beats/min. V(OBLAVT1), HR(OBLAVT1), and W(OBLAVT1) were 52.7 km/h, 180 beats/min, and 500.6 W, respectively. Drag coefficient and shape coefficient, measured in a wind tunnel, were 0. 244 and 0.65 m(2), respectively. The cyclist set a world record of 53,040 m, with an estimated average power output of 509.5 W. Based on direct laboratory data of the power vs. oxygen uptake relationship for this cyclist, this is slightly higher than the 497. 25 W corresponding to his oxygen uptake at OBLA (5.65 l/min). In conclusion, 1) the 1-h cycling world record is the result of the interaction between physiological and aerodynamic characteristics; and 2) performance in this event can be predicted using mathematical models that integrate the principal performance-determining variables.

Effect of changing the saddle angle on the incidence of low back pain in recreational bicyclists

OBJECTIVE

According to the literature, 30-70% of cyclists suffer from cervical, dorsal, or lumbar back pain. This study was conducted to evaluate one of the possible causes of low back pain and to suggest a solution by appropriate adjustments to the bicycle.

METHODS

Serial fluoroscopic studies were performed while cyclists sat on different types of bicycle (sports, mountain, and city). Pelvic/spine angles were measured at different seat angles, and the related force vectors analysed.

RESULTS

There was a tendency towards hyperextension of the pelvic/spine angle which resulted in an increase in tensile forces at the promontorium. These forces can easily be reduced by appropriate adjustment of the seat angle--that is, by creating an anterior inclining angle. The findings of the biomechanical analysis were then applied to a group of cyclists who were members of a cycling club and who complained of low back pain. After appropriate adjustment of the saddle angle, most of the cyclists (>70%) reported major improvement in the incidence and magnitude of their back pain.

CONCLUSIONS

The incidence and magnitude of back pain in cyclists can be reduced by appropriate adjustment of the angle of the saddle. It is important that these findings be conveyed to cyclists, bicycle salesmen, trainers, and members of the general public who engage in cycling, in order to decrease the prevalence of back pain.

Racing cyclist power requirements in the 4000-m individual and team pursuits

PURPOSE

The purpose of this paper is: 1) to present field test data describing the power requirements of internationally competitive individual and team pursuiters, and 2) to develop a theoretical model for pursuit power based upon on these tests.

METHODS

In preparing U.S. cycling's pursuit team for the 1996 Atlanta Olympics, U.S. team scientists measured cycling power of seven subjects on the Atlanta track using a crank dynamometer (SRM) at speeds from 57 to 60 kph. By using these field data and other tests, mathematical models were devised which predict both individual and team pursuit performance. The field data indicate the power within a pace line at 60 kph averages 607 W in lead position (100%), 430 W in second position (70.8%), 389 W in third position (64.1%), and 389 W in fourth position (64.0%). A team member requires about 75% of the energy necessary for cyclists riding alone at the same speed. These results compare well with field measurements from a British pursuit team, to recent wind tunnel tests, and to earlier bicycle coast down tests.

RESULTS

The theoretical models predict performance with reasonable accuracy when the average power potential of an individual or team is known, or they may be used to estimate the power of pursuit competitors knowing race times. The model estimates that Christopher Boardman averaged about 520 W when setting his 1996, 4000-m individual pursuit record of 4 min 11.114 s and the Italian 4000-m pursuit team averaged about 480 W in setting their record of 4:00.958. Both used the "Superman" cycling position.

CONCLUSIONS

These records would be very difficult to break using less aerodynamic riding positions, due to the extraordinarily high power requirements.

Comparing cycling world hour records, 1967-1996: modeling with empirical data

PURPOSE

The world hour record in cycling has increased dramatically in recent years. The present study was designed to compare the performances of former/current record holders, after adjusting for differences in aerodynamic equipment and altitude. Additionally, we sought to determine the ideal elevation for future hour record attempts.

METHODS

The first step was constructing a mathematical model to predict power requirements of track cycling. The model was based on empirical data from wind-tunnel tests, the relationship of body size to frontal surface area, and field power measurements using a crank dynamometer (SRM). The model agreed reasonably well with actual measurements of power output on elite cyclists. Subsequently, the effects of altitude on maximal aerobic power were estimated from published research studies of elite athletes. This information was combined with the power requirement equation to predict what each cyclist's power output would have been at sea level. This allowed us to estimate the distance that each rider could have covered using state-of-the-art equipment at sea level. According to these calculations, when racing under equivalent conditions, Rominger would be first, Boardman second, Merckx third, and Indurain fourth. In addition, about 60% of the increase in hour record distances since Bracke's record (1967) have come from advances in technology and 40% from physiological improvements.

RESULTS AND CONCLUSIONS

To break the current world hour record, field measurements and the model indicate that a cyclist would have to deliver over 440 W for 1 h at sea level, or correspondingly less at altitude. The optimal elevation for future hour record attempts is predicted to be about 2500 m for acclimatized riders and 2000 m for unacclimatized riders.

Determination of optimal pacing strategy in track cycling with an energy flow model

The purpose of this study was to investigate the effect of pacing strategies on performance times in the 1000 m time trial event and the 4000 m pursuit event in track cycling. For this purpose, we simulated these events with a model based on the flow of energy in cycling. Different strategies in distributing the available anaerobic energy were evaluated and we compared model predictions of split times and final times with values achieved by cyclists during championships. The best result at the 1000 m time trial was obtained when the cyclist had the highest anaerobic peak power output and used an 'all-out' strategy. The fastest time on the 4000 m pursuit was achieved with an 'all-out' start at a high level of initial power output, followed by a constant anaerobic power output after 12 seconds, resulting in an evenly paced race. The results show that even small variations in pacing strategy may have substantial effects on performance. There seems to be an opportunity to gain a competitive advantage when individual athletes experiment with small variations in pacing strategy to find the precise individual strategy that works best under specific conditions.

Efficiency of skeletal and cardiac muscle

In the human physiology literature values for skeletal and cardiac mechanical efficiency are being reported that seem to be much higher than are found in isolated tissue studies. We consider some of the different efficiency definitions and explore some possible reasons for low isolated tissue values, these include the experimental protocols used, the time at which measurements are made, afterloaded versus sinusoidal contractions, the effects of varying activation levels and recovery heat uncertainty. We examine some of the mechanical and energetic differences between cardiac and skeletal muscle--the absence of shortening heat, the linear relationship between energy per beat and pressure-volume area, constant contractile efficiency, and a larger crossbridge (CB) working stroke. Some observations are made on muscle energetics and loose and tight coupling CB models.

Energetics of best performances in track cycling

VO2max and best performance times (BPTs) obtained during maximal voluntary trials over 1, 2, 5, and 10 km from a stationary start were assessed in 10 elite cyclists. Steady-state VO2 and peak blood lactate concentration ([La]b) were also determined in the same subjects pedaling on a track at constant submaximal speeds. The energy cost of cycling (Cc, J.m-1) was calculated as the ratio of VO2, corrected for glycolytic energy production and expressed in W, to v (m.s-1). Individual relationships between Cc and v were described by: Cc = Ccrr + k1 v2 where Ccrr is the energy spent against friction and k1 v2 is that spent against drag. Overall energy cost of cycling (Cctot) was obtained, adding to Cc the energy spent to accelerate the total moving mass from a stationary start. Individual theoretical BPTs were then calculated and compared with the actual ones as follows. The maximal metabolic power sustained at a constant level by a given subject (Emax, W) is a known function of the exhaustion time (te). It depends on his VO2max and maximal anaerobic capacity; it was obtained from individual VO2max and [La]b values. The metabolic power (Ec, W) necessary to cover any given distance (d) is a known function of the performance time over d (td); it is given by Ec = Cctot v = Cctot d td. For all subjects and distances, the t values solving the equalities Emax F(te) = Ec F(td) were calculated and assumed to yield theoretical BPTs. Calculations showed a fairly good agreement between actual and calculated BPTs with an average ratio of 1.035 +/- 0.058.

Influence of different racing positions on metabolic cost in elite cyclists

The spectacular improvements of the 1-h world record in cycling in the last four years have highlighted the importance of aerodynamics in modern bicycle racing. We have investigated the metabolic consequences of the low-crouched aero-positions necessary to reduce air drag. In this study, 14 elite male bicycle racers (24.0 +/- 1.0 yr, VO2max 69.4 +/- 0.5 mL.kg-1.min-1) were tested for oxygen consumption (VO2) and heart rate (HR) at 70% (302.6 +/- 5.3 W) of their individual VO2max in three different riding positions during a single test run. The subjects rode their racing bicycles on a wind braked roller; the sequence of the three following positions was randomized: 1) upright cycling (UP), cadence 90 rpm; 2) hands on drops (DP), 90 rpm; and 3) hands on clip-on aero-handlebars (AP), 90 rpm. VO2 and HR values in AP were significantly higher by 1.5 mL.kg-1.min-1 and 5 beats.min-1, respectively, compared with UP. We concluded that riding a bicycle in an extreme aero-position increases the metabolic cost of cycling when wind resistance is not taken into account. However, when the mechanical power losses of 9 W (estimated by the VO2 increase) are compared with the expected aerodynamic power savings of approximately 100 W, it appears that aerodynamic advantages by far outweight their metabolic cost.

Effects of altitude on top speeds during 1 h unaccompanied cycling

The present world record for 1 h unaccompanied cycling (55.291 km) was set by T. Rominger in November 1994 at sea level (Bordeaux, France). However, maximal aerobic cycling performances can be expected to increase at altitude because, for a given air temperature, air density decreases more than VO2max. The combined effect of these opposite trends results in an improvement of performances. In this study, based on the aerodynamics of track cycling, and assuming an average decrease of VO2max with altitude as from the literature, we show that the ideal altitude for Rominger is 4000 m where he could cover 60.1 km in 1 h. To our knowledge, only two cyclists attempted at close time intervals to set the 1 h record at sea level and at altitude (Mexico, 2230 m above sea level): F. Moser and J. Longo. Their increase of performance with altitude was only about 50% of that predicted on the basis of similar calculations as performed on Rominger. This suggests that the decrease of VO2max resulting from altitude is greater for athletes than for average trained subjects and/or that the fraction of VO2max that can be maintained throughout 1 h decreases with altitude.