Multivariable optimization of cycling biomechanics

Relying on a biomechanical model of the lower limb which treats the leg-bicycle system as a five-bar linkage constrained to plane motion, a cost function derived from the joint moments developed during cycling is computed. At constant average power of 200 W, the effect of five variables on the cost function is studied. The five variables are pedalling rate, crank arm length, seat tube angle, seat height, and longitudinal foot position on the pedal. A sensitivity analysis of each of the five variables shows that pedalling rate is the most sensitive, followed by the crank arm length, seat tube angle, seat height, and longitudinal foot position on the pedal (the least sensitive). Based on Powell's method, a multivariable optimization search is made for the combination of variable values which minimize the cost function. For a rider of average anthropometry (height 1.78 m, weight 72.5 kg), a pedalling rate of 115 rev min-1, crank arm length of 0.140 m, seat tube angle of 76 degrees, seat height plus crank arm length equal to 97% of trochanteric leg length, and longitudinal foot position on the pedal equal to 54% of foot length correspond to the cost function global minimum. The effect of anthropometric parameter variations is also examined and these variations influence the results significantly. The optimal crank arm length, seat height, and longitudinal foot position on the pedal increase as the size of rider increases whereas the optimal cadence and seat tube angle decrease as the rider's size increases. The dependence of optimization results on anthropometric parameters emphasizes the importance of tailoring bicycle equipment to the anthropometry of the individual.     

Effects on the crank torque profile when changing pedalling cadence in level ground and uphill road cycling

Despite the importance of uphill cycling performance during cycling competitions, there is very little research investigating uphill cycling, particularly concerning field studies. The lack of research is partly due to the difficulties in obtaining data in the field. The aim of this study was to analyse the crank torque in road cycling on level and uphill using different pedalling cadences in the seated position. Seven male cyclists performed four tests in the seated position (1) on level ground at 80 and 100 rpm, and (2) on uphill road cycling (9.25% grade) at 60 and 80 rpm.The cyclists exercised for 1 min at their maximal aerobic power. The bicycle was equipped with the SRM Training System (Schoberer, Germany) for the measurement of power output (W), torque (Nm), pedalling cadence (rpm), and cycling velocity (km h(-1)). The most important finding of this study indicated that at maximal aerobic power the crank torque profile (relationship between torque and crank angle) varied substantially according to the pedalling cadence and with a minor effect according to the terrain. At the same power output and pedalling cadence (80 rpm) the torque at a 45 degrees crank angle tended (p < 0.06) to be higher (+26%) during uphill cycling compared to level cycling. During uphill cycling at 60 rpm the peak torque was increased by 42% compared with level ground cycling at 100 rpm.When the pedalling cadence was modified, most of the variations in the crank torque profile were localised in the power output sector (45 degrees to 135 degrees).     

Determinants of metabolic cost during submaximal cycling.

The metabolic cost of producing submaximal cycling power has been reported to vary with pedaling rate. Pedaling rate, however, governs two physiological phenomena known to influence metabolic cost and efficiency: muscle shortening velocity and the frequency of muscle activation and relaxation. The purpose of this investigation was to determine the relative influence of those two phenomena on metabolic cost during submaximal cycling. Nine trained male cyclists performed submaximal cycling at power outputs intended to elicit 30, 60, and 90% of their individual lactate threshold at four pedaling rates (40, 60, 80, 100 rpm) with three different crank lengths (145, 170, and 195 mm). The combination of four pedaling rates and three crank lengths produced 12 pedal speeds ranging from 0.61 to 2.04 m/s. Metabolic cost was determined by indirect calorimetery, and power output and pedaling rate were recorded. A stepwise multiple linear regression procedure selected mechanical power output, pedal speed, and pedal speed squared as the main determinants of metabolic cost (R(2) = 0.99 +/- 0.01). Neither pedaling rate nor crank length significantly contributed to the regression model. The cost of unloaded cycling and delta efficiency were 150 metabolic watts and 24.7%, respectively, when data from all crank lengths and pedal speeds were included in a regression. Those values increased with increasing pedal speed and ranged from a low of 73 +/- 7 metabolic watts and 22.1 +/- 0.3% (145-mm cranks, 40 rpm) to a high of 297 +/- 23 metabolic watts and 26.6 +/- 0.7% (195-mm cranks, 100 rpm). These results suggest that mechanical power output and pedal speed, a marker for muscle shortening velocity, are the main determinants of metabolic cost during submaximal cycling, whereas pedaling rate (i.e., activation-relaxation rate) does not significantly contribute to metabolic cost.     

Optimal design parameters of the bicycle-rider system for maximal muscle power output

The purpose of this study was to find the optimal values of design parameters for a bicycle-rider system (crank length, pelvic inclination, seat height, and rate of crank rotation) which maximize the power output from muscles of the human lower limb during bicycling. The human lower limb was modelled as a planar system of five rigid bodies connected by four smooth pin joints and driven by seven functional muscle groups. The muscles were assumed to behave according to an adapted form of Hill's equation. The dependence of the average power on the design parameters was examined. The instantaneous power of each muscle group was studied and simultaneous activity of two seemingly antagonistic muscle groups was analyzed. Average peak power for one full pedal revolution was found to be around 1100 W. The upper body position corresponding to this peak power output was slightly reclined, and the pedalling rate was 155 rpm for a nominal crank length of 170 mm.     

An angular velocity profile in cycling derived from mechanical energy analysis

The contributions of this article are twofold. One is procedure for determining the angular velocity profile in seated cycling that maintains the total mechanical energy of both legs constant. A five-bar linkage model (thigh, shank, foot, crank and frame) of seated (fixed hip) cycling served for the derivation of the equations to compute potential and kinetic energies of the leg segments over a complete crank cycle. With experimentally collected pedal angle data as input, these equations were used to compute the total combined mechanical energy (sum of potential and kinetic energies of the segments of both legs) for constant angular velocity pedalling at 90 rpm. Total energy varied indicating the presence of internal work. Motivated by a desire to test the hypothesis that reducing internal work in cycling will reduce energy expenditure, a procedure was developed for determining the angular velocity profile that eliminated any change in total energy. Using data recorded from five subjects, this procedure was used to determine a reference profile for an average equivalent cadence of 90 rpm. The phase of this profile is such that highest and lowest angular velocities occur when the cranks are near vertical and horizontal respectively. The second contribution is the testing of the hypothesis that the reference angular velocity profile serves to effectively reduce internal work for the subjects whose data were used to develop this profile over the range of pedalling rates (80-100 rpm) naturally preferred. In this range, the internal work was decreased a minimum of 48% relative to the internal work associated with constant angular velocity pedalling. The acceptance of this hypothesis has relevance to the protocol for future experiments which explore the effect of reduced internal work on energy expenditure in cycling.     

Cycling efficiency and pedalling frequency in road cyclists

The purpose of this study was to determine the influence of pedalling rate on cycling efficiency in road cyclists. Seven competitive road cyclists participated in the study. Four separate experimental sessions were used to determine oxygen uptake (VO(2)) and carbon dioxide output (VCO(2)) at six exercise intensities that elicited a VO(2) equivalent to 54, 63, 73, 80, 87 and 93% of maximum VO(2) (VO(2max)). Exercise intensities were administered in random order, separated by rest periods of 3-5 min; four pedalling frequencies (60, 80, 100 and 120 rpm) were randomly tested per intensity. The oxygen cost of cycling was always lower when the exercise was performed at 60 rpm. At each exercise intensity, VO(2) showed a parabolic dependence on pedalling rate (r = 0.99-1, all P < 0.01) with a curvature that flattened as intensity increased. Likewise, the relationship between power output and gross efficiency (GE) was also best fitted to a parabola (r = 0.94-1, all P < 0.05). Regardless of pedalling rate, GE improved with increasing exercise intensity (P < 0.001). Conversely, GE worsened with pedalling rate (P < 0.001). Interestingly, the effect of pedalling cadence on GE decreased as a linear function of power output (r = 0.98, n = 6, P < 0.001). Similar delta efficiency (DE) values were obtained regardless of pedalling rate [21.5 (0.8), 22.3 (1.2), 22.6 (0.6) and 23.9 (1.0)%, for the 60, 80, 100 and 120 rpm, mean (SEM) respectively]. However, in contrast to GE, DE increased as a linear function of pedalling rate (r = 0.98, P < 0.05). The rate at which pulmonary ventilation increased was accentuated for the highest pedalling rate (P < 0.05), even after accounting for differences in exercise intensity and VO(2) (P < 0.05). Pedalling rate per se did not have any influence on heart rate which, in turn, increased linearly with VO(2). These results may help us to understand why competitive cyclists often pedal at cadences of 90-105 rpm to sustain a high power output during prolonged exercise.     

Goniometric measurement of hip motion in cycling while standing

The purpose of this study was to develop an instrument for quantifying the motion of the hip relative to the bicycle while cycling in the standing position. Because of the need to measure hip motion on the road as well as in the laboratory, a goniometer which locates the hip using spherical coordinates was designed. The goniometer is presented first, followed by the development of the equations that enable the distance from the joint center to the pedal spindle to be determined. The orientation of this line segment is specified by calculating two angles referenced to the frame. Also outlined are the procedures used to both calibrate the goniometer and perform an accuracy check. The results of this check indicate that the attachment point of the goniometer to the rider can be located to within 2.5 mm of the true position. The goniometer was used to record the hip movement patterns of six subjects who cycled in the standing position on a treadmill. Representative results from one test subject who cycled at 6% grade and 25 km h-1 are presented. Results indicate that the bicycle is leaned from side to side with the frequency of leaning equal to the frequency of pedalling. Extreme lean angles are +/- 6 degrees. The distance from the hip to the pedal varies approximately sinusoidally with frequency equal to pedalling rate and amplitude somewhat less than crank arm length. The absolute elevation of the hip, however, exhibits two cycles for each crank cycle. Asymmetry in the plot of elevation over a single crank cycle indicates that the pelvis rocks from side to side and that the elevation of the pelvis midpoint changes. Extreme values of the pelvis rocking angle are +/- 12 degrees. Highest pelvis midpoint elevations, however, do not occur at the same crank angles as those angles at which the pelvis rocking is extreme. It appears that the vertical motion of the hips affects pedalling mechanics when cycling in the standing position.     

A theoretical analysis of an optimal chainring shape to maximize crank power during isokinetic pedaling

Previous studies have sought to improve cycling performance by altering various aspects of the pedaling motion using novel crank–pedal mechanisms and non-circular chainrings. However, most designs have been based on empirical data and very few have provided significant improvements in cycling performance. The purpose of this study was to use a theoretical framework that included a detailed musculoskeletal model driven by individual muscle actuators, forward dynamic simulations and design optimization to determine if cycling performance (i.e., maximal power output) could be improved by optimizing the chainring shape to maximize average crank power during isokinetic pedaling conditions. The optimization identified a consistent non-circular chainring shape at pedaling rates of 60, 90 and 120 rpm with an average eccentricity of 1.29 that increased crank power by an average of 2.9% compared to a conventional circular chainring. The increase in average crank power was the result of the optimal chainrings slowing down the crank velocity during the downstroke (power phase) to allow muscles to generate power longer and produce more external work. The data also showed that chainrings with higher eccentricity increased negative muscle work following the power phase due to muscle activation–deactivation dynamics. Thus, the chainring shape that maximized average crank power balanced these competing demands by providing enough eccentricity to increase the external work generated by muscles during the power phase while minimizing negative work during the subsequent recovery phase.     

Neuromuscular fatigue during prolonged pedalling exercise at different pedalling rates

The purpose of this study was to estimate the differences in neuromuscular fatigue among prolonged pedalling exercises performed at different pedalling rates at a given exercise intensity. The integrated electromyogram (iEMG) slope defined by the changes in iEMG as a function of time during exercise was adopted as the measurement for estimating neuromuscular fatigue. The results of this experiment showed that the relationship between pedalling rate and the means of the iEMG slopes for eight subjects was a quadratic curve and the mean value at 70 rpm [1.56 (SD 0.65) V·min^–1] was significantly smaller (P < 0.01) than that at 50 and 60 rpm [2.25 (SD 0.54), and 2.22 (SD 0.68), respectively]. On the other hand, the mean value of oxygen consumption obtained simultaneously showed a tendency to increase linearly with the increase in pedalling rate, and the values at 70 and 80 rpm were significantly higher than those at 40 and 50 rpm. In conclusion, it was demonstrated that the degree of neuromuscular fatigue estimated by the iEMG changes for five periods of prolonged pedalling exercise at a given exercise intensity was different among the different pedalling rates, and that the pedalling rate at which minimal neuromuscular fatigue was obtained was not coincident with the rate at which the minimal oxygen consumption was obtained, but was coincident with the rate which most subjects preferred. These findings would suggest that the reason why most people prefer a relative higher pedalling rate, even though higher oxygen consumption is required, is closely related to the development of neuromuscular fatigue in the working muscles.     

The association between negative muscle work and pedaling rate.

The objective of this research was to use a pedal force decomposition approach to quantify the amount of negative muscular crank torque generated by a group of competitive cyclists across a range of pedaling rates. We hypothesized that negative muscular crank torque increases at high pedaling rates as a result of the activation dynamics associated with muscle force development and the need for movement control, and that there is a correlation between negative muscular crank torque and pedaling rate. To test this hypothesis, data were collected during 60, 75, 90, 105 and 120 revolutions per minute (rpm) pedaling at a power output of 260 W. The statistical analysis supported our hypothesis. A significant pedaling rate effect was detected in the average negative muscular crank torque with all pedaling rates significantly different from each other (p < 0.05). There was no negative muscular crank torque generated at 60 rpm and negligible amounts at 75 and 90 rpm. But substantial negative muscular crank torque was generated at the two highest pedaling rates (105 and 120 rpm) that increased with increasing pedaling rates. This result suggested that there is a correlation between negative muscle work and the pedaling rates preferred by cyclists (near 90 rpm), and that the cyclists' ability to effectively accelerate the crank with the working muscles diminishes at high pedaling rates.     

Laboratory versus outdoor cycling conditions: differences in pedaling biomechanics

The aim of our study was to compare crank torque profile and perceived exertion between the Monark ergometer (818 E) and two outdoor cycling conditions: level ground and uphill road cycling. Seven male cyclists performed seven tests in seated position at different pedaling cadences: (a) in the laboratory at 60, 80, and 100 rpm; (b) on level terrain at 80 and 100 rpm; and (c) on uphill terrain (9.25% grade) at 60 and 80 rpm. The cyclists exercised for 1 min at their maximal aerobic power. The Monark ergometer and the bicycle were equipped with the SRM Training System (Schoberer, Germany) for the measurement of power output (W), torque (Nxm), pedaling cadence (rpm), and cycling velocity (kmxh-1). The most important findings of this study indicate that at maximal aerobic power the crank torque profiles in the Monark ergometer (818 E) were significantly different (especially on dead points of the crank cycle) and generate a higher perceived exertion compared with road cycling conditions.     

On the relation between joint moments and pedalling rates at constant power in bicycling

Joint moments are of interest because they bear some relation to muscular effort and hence rider performance. The general objective of this study is to explore the relation between joint moments and pedalling rate (i.e. cadence). Joint moments are computed by modelling the leg-bicycle system as a five-bar linkage constrained to plane motion. Using dynamometer pedal force data and potentiometer crank and pedal position data, system equations are solved on a computer to produce moments at the ankle, knee and hip joints. Cadence and pedal forces are varied inversely to maintain constant power. Results indicate that average joint moments vary considerably with changes in cadence. Both hip and knee joints show an average moment which is minimum near 105 rotations min-1 for cruising cycling. It appears that an optimum rotations min-1 can be determined from a mechanical approach for any given power level and bicycle-rider geometry.     

Effect of muscle temperature on leg extension force and short-term power output in humans

The effect of changing muscle temperature on performance of short term dynamic exercise in man was studied. Four subjects performed 20 s maximal sprint efforts at a constant pedalling rate of 95 crank rev.min-1 on an isokinetic cycle ergometer under four temperature conditions: from rest at room temperature; and following 45 min of leg immersion in water baths at 44; 18; and 12 degrees C. Muscle temperature (Tm) at 3 cm depth was respectively 36.6, 39.3, 31.9 and 29.0 degrees C. After warming the legs in a 44 degrees C water bath there was an increase of approximately 11% in maximal peak force and power (PPmax) compared with normal rest while cooling the legs in 18 and 12 degrees C water baths resulted in reductions of approximately 12% and 21% respectively. Associated with an increased maximal peak power at higher Tm was an increased rate of fatigue. Two subjects performed isokinetic cycling at three different pedalling rates (54, 95 and 140 rev.min-1) demonstrating that the magnitude of the temperature effect was velocity dependent: At the slowest pedalling rate the effect of warming the muscle was to increase PPmax by approximately 2% per degree C but at the highest speed this increased to approximately 10% per degree C.     

Crank inertial load affects freely chosen pedal rate during cycling.

Cyclists seek to maximize performance during competition, and gross efficiency is an important factor affecting performance. Gross efficiency is itself affected by pedal rate. Thus, it is important to understand factors that affect freely chosen pedal rate. Crank inertial load varies greatly during road cycling based on the selected gear ratio. Nevertheless, the possible influence of crank inertial load on freely chosen pedal rate and gross efficiency has never been investigated. This study tested the hypotheses that during cycling with sub-maximal work rates, a considerable increase in crank inertial load would cause (1) freely chosen pedal rate to increase, and as a consequence, (2) gross efficiency to decrease. Furthermore, that it would cause (3) peak crank torque to increase if a constant pedal rate was maintained. Subjects cycled on a treadmill at 150 and 250W, with low and high crank inertial load, and with preset and freely chosen pedal rate. Freely chosen pedal rate was higher at high compared with low crank inertial load. Notably, the change in crank inertial load affected the freely chosen pedal rate as much as did the 100W increase in work rate. Along with freely chosen pedal rate being higher, gross efficiency at 250W was lower during cycling with high compared with low crank inertial load. Peak crank torque was higher during cycling at 90rpm with high compared with low crank inertial load. Possibly, the subjects increased the pedal rate to compensate for the higher peak crank torque accompanying cycling with high compared with low crank inertial load.     

Optimal pedalling velocity characteristics during maximal and submaximal cycling in humans

The aim of this study was to compare optimal pedalling velocities during maximal (OVM) and submaximal (OVSM) cycling in human, subjects with different training backgrounds. A group of 22 subjects [6 explosive (EX), 6 endurance (EN) and 10 non-specialised subjects] sprint cycled on a friction-loaded ergometer four maximal sprints lasting 6 s each followed by five 3-min periods of steady-state cycling at 150 W with pedalling frequencies varying from 40 to 120 rpm. The OVM and OVSM were defined as the velocities corresponding to the maximal power production and the lowest oxygen consumption, respectively. A significant linear relationship (r2 = 0.52, P < 0.001) was found between individual OVM [mean 123.1 (SD 11.2) rpm] and OVSM [mean 57.0 (SD 4.9) rpm, P < 0.001] values, suggesting that the same functional properties of leg extensor muscles influence both OVM and OVSM. Since EX was greater than EN in both OVM and OVSM (134.3 compared to 110.9 rpm and 60.8 compared to 54.0 rpm, P < 0.01 and P < 0.05, respectively) it could be hypothesised that the distribution of muscle fibre type plays an important role in optimising both maximal and submaximal cycling performance.     

The influence of pedaling rate on bilateral asymmetry in cycling.

The objectives of this study were to (1) determine whether bilateral asymmetry in cycling changed systematically with pedaling rate, (2) determine whether the dominant leg as identified by kicking contributed more to average power over a crank cycle than the other leg, and (3) determine whether the dominant leg asymmetry changed systematically with pedaling rate. To achieve these objectives, data were collected from 11 subjects who pedaled at five different pedaling rates ranging from 60 to 120 rpm at a constant workrate of 260 W. Bilateral pedal dynamometers measured two orthogonal force components in the plane of the bicycle. From these measurements, asymmetry was quantified by three dependent variables, the percent differences in average positive power (%AP), average negative power (%AN), and average crank power (%AC). Differences were taken for two cases--with respect to the leg generating the greater total average for each power quantity at 60 rpm disregarding the measure of dominance, and with respect to the dominant leg as determined by kicking. Simple linear regression analyses were performed on these quantities both for the subject sample and for individual subjects. For the subject sample, only the percent difference in average negative power exhibited a significant linear relationship with pedaling rate; as pedaling rate increased, the asymmetry decreased. Although the kicking dominant leg contributed significantly greater average crank power than the non-dominant leg for the subject sample, the non-dominant leg contributed significantly greater average positive power and average negative power than the dominant leg. However, no significant linear relationships for any of these three quantities with pedaling rate were evident for the subject sample because of high variability in asymmetry among the subjects. For example, significant linear relationships existed between pedaling rates and percent difference in total average power per leg for only four of the 11 subjects and the nature of these relationships was different (e.g. positive versus negative slopes). It was concluded that pedaling asymmetry is highly variable among subjects and that individual subjects may exhibit different systematic changes in asymmetry with pedaling rate depending on the quantity of interest.     

VO2/power output relationship and the slow component of oxygen uptake kinetics during cycling at different pedaling rates: relationship to venous lactate accumulation and blood acid-base balance.

In this experiment we studied the effect of different pedalling rates during cycling at a constant power output (PO) 132+/-31 W (mean+/-S.D.), corresponding to 50% VO2 max, on the oxygen uptake and the magnitude of the slow component of VO2 kinetics in humans. The PO corresponded to 50% of VO2 max, established during incremental cycling at a pedalling rate of 70 rev.min(-1). Six healthy men aged 22.2+/-2.0 years with VO2 max 3.89+/-0.92 l.min(-1), performed on separate days constant PO cycling exercise lasting 6 min at pedalling rates 40, 60, 80, 100 and 120 rev.min(-1), in random order. Antecubital blood samples for plasma lactate [La]pl and blood acid-base balance variables were taken at 1 min intervals. Oxygen uptake was determined breath-by-breath. The total net oxygen consumed throughout the 6 min cycling period at pedalling rates of 40, 60, 80, 100 and 120 rev.min(-1) amounted to 7.727+/-1.197, 7.705+/-1.548, 8.679+/-1.262, 9.945+/-1.435 and 13.720+/-1.862 l, respectively for each pedalling rate. The VO2 during the 6 min of cycling only rose slowly by increasing the pedalling rate in the range of 40-100 rev.min(-1). This increase, was 0.142 l per 20 rev.min(-1) on the average. Plasma lactate concentration during the sixth minute of cycling changed little within this range of pedalling rates: the values were 1.83+/-0.70, 1.80+/-0.48, 2.33+/-0.88 and 2.52+/-0.33 mmol.l(-1). The values of [La]pl reached in the 6th minute of cycling were not significantly different from the pre-exercise levels. Blood pH was also not affected by the increase of pedalling rate in the range of 40-100 rev.min(-1). However, an increase of pedalling rate from 100 to 120 rev.min(-1) caused a sudden increase in the VO2 amounting to 0.747 l per 20 rev.min(-1), accompanied by a significant increase in [La]pl from 1.21+/-0.26 mmol.l(-1) in pre-exercise conditions to 5.92+/-2.46 mmol.l(-1) reached in the 6th minute of cycling (P<0.01). This was also accompanied by a significant drop of blood pH, from 7.355+/-0.039 in the pre-exercise period to 7.296+/-0.060 in the 6th minute of cycling (P < 0.01). The mechanical efficiency calculated on the basis of the net VO2 reached between the 4th and the 6th minute of cycling amounted to 26.6+/-2.7, 26.4+/-2.0, 23.4+/-3.4, 20.3+/-2.6 and 14.7+/-2.2%, respectively for pedalling rates of 40, 60, 80, 100 and 120 rev.min(-1). No significant increase in the VO2 from the 3rd to the 6th min (representing the magnitude of the slow component of VO2 kinetics) was observed at any of the pedalling rates (-0.022+/-0.056, -0.009+/-0.029, 0.012+/-0.073, 0.030+/-0.081 and 0.122+/-0.176 l.min(-1) for pedalling rates of 40, 60, 80, 100 and 120 rev.min(-1), respectively). Thus a significant increase in [La]pl and a decrease in blood pH do not play a major role in the mechanism(s) responsible for the slow component of VO2 kinetics in humans.     

A method for biomechanical analysis of bicycle pedalling

This paper reports a new method, which enables a detailed biomechanical analysis of the lower limb during bicycling. The method consists of simultaneously measuring both the normal and tangential pedal forces, the EMGs of eight leg muscles, and the crank arm and pedal angles. Data were recorded for three male subjects of similar anthropometric characteristics. Subjects rode under different pedalling conditions to explore how both pedal forces and pedalling rates affect the biomechanics of the pedalling process. By modelling the leg-bicycle as a five bar linkage and driving the linkage with the measured force and kinematic data, the joint moment histories due to pedal forces only (i.e. no motion) and motion only (i.e. no pedal forces) were generated. Total moments were produced by superimposing the two moment histories. The separate moment histories, together with the pedal forces and EMG results, enable a detailed biomechanical analysis of bicycle pedalling. Inasmuch as the results are similar for all three subjects, the analysis for one subject is discussed fully. One unique insight gained via this new method is the functional role that individual leg muscles play in the pedalling process.     

Methodical aspects of perceived exertion rating and its relation to pedalling rate and rotating mass.

Methodical aspects of the relationship between pedalling rate and rotating mass and perceived exertion rating (PER; Borg, 1962) were studied in trained, untrained, and ill subjects in bicycle ergometry. Pedalling rate varied between 40 and 100 rpm, work load steps were 5, 10, 15 and 20 mkp/sec in the healthy subjects, and 2.5, 5, 7.5 and 10 mkp/sec in the patients. PER decreased with increasing pedalling rate in all healthy subjects. In the patients, PER increased moderately at work load of 2.5 mkp/sec, but decreased at higher work loads up to 80 rpm, followed by a slight increase at 100 rpm. Higher mass of the flywheel, studied in 6 trained subjects, lowered the PER insignificantly. In the healthy subjects, test criteria, such as reproducibility, reliability, sensitivity, and linearity remained almost unaffected by pedalling rate. In patients, increasing pedalling speed diminished reproducibility and sensitivity. The strictness of the PER work load relationship is lowered at higher pedalling rate, especially at 100 rpm. When using the PER scale, pedalling rate has to be considered as an factor of main influence.     

Estimation of oxygen cost of internal power during cycling exercise with changing pedal rate

It has been reported that oxygen uptake (VO2) increases exponentially with levels of the pedal rate during cycling. The purpose of this study was therefore to test the hypothesis that the O2 cost for internal power output (Pint) exerted in exercising muscle itself would be larger than for an external power output (Pext) calculated from external load and pedal rate during cycling exercise under various conditions of Pint and Pext in a large range of pedal rates. The O2 cost (DeltaVO2/ Deltapower output) was investigated in three experiments that featured different conditions on a cycle ergometer that were carried out at the same levels of total power output (Ptot; sum of Pint and Pext) (Exp. 1), Pext (Exp. 2) and load (Exp. 3). Each experiment consisted of three exercise tests with three levels of pedal rate (40 rpm for a lower pedal rate: LP; 70-80 rpm for a moderate pedal rate: MP; and 100-120 rpm for a higher pedal rate: HP) lasting for 2-3 min of unloaded cycling followed by 4-5 min of loaded cycling. Blood lactate accumulations (2.3-3.4 mmol l(-1)) at the HP were significantly higher compared with the LP (0.6-0.9 mmol l(-1)) and MP (0.9-1.0 mmol l(-1)) except for the LP in Exp. 1. The VO2 (360-432 ml min(-1) for LP, 479-644 ml min(-1) for MP, 960-1602 ml min(-1) for HP) during unloaded cycling in the three experiments increased exponentially with increasing pedal rates regardless of Pext=0. Moreover, the slope of the VO2-Pint (13.7 ml min(-1) W(-1)) relation revealed a steeper inclination than that of the VO2-Pext (10.2 ml min(-1) W(-1)) relation. We concluded that the O2 cost for Pint was larger than for Pext during the cycling exercises, indicating that the O2 cost for Ptot could be affected by the ratio of Pint to Ptot due to the levels of pedal rate.