Power output and work in different muscle groups during ergometer cycling

The aim of this study was to calculate the magnitude of the instantaneous muscular power output at the hip, knee and ankle joints during ergometer cycling. Six healthy subjects pedalled a weight-braked bicycle ergometer at 120 watts (W) and 60 revolutions per minute (rpm). The subjects were filmed with a cine camera, and pedal reaction forces were recorded from a force transducer mounted in the pedal. The muscular work at the hip, knee and ankle joint was calculated using a model based upon dynamic mechanics described elsewhere. The mean peak concentric power output was, for the hip extensors, 74.4 W, hip flexors, 18.0 W, knee extensors, 110.1 W, knee flexors, 30.0 W and ankle plantar flexors, 59.4 W. At the ankle joint, energy absorption through eccentric plantar flexor action was observed, with a mean peak power of 11.4 W and negative work of 3.4 J for each limb and complete pedal revolution. The energy production relationships between the different major muscle groups were computed and the contributions to the total positive work were: hip extensors, 27%; hip flexors, 4%; knee extensors, 39%; knee flexors, 10%; and ankle plantar flexors 20%.     

Mechanical muscular power output and work during ergometer cycling at different work loads and speeds

The aim of the study was to calculate the magnitude of the instantaneous muscular power output at the hip, knee and ankle joints during ergometer cycling at different work loads and speeds. Six healthy subjects pedalled a weight-braked cycle ergometer at 0, 120 and 240 W at a constant speed of 60 rpm. The subjects also pedalled at 40, 60, 80 and 100 rpm against the same resistance, giving power outputs of 80, 120, 160 and 200 W respectively. The subjects were filmed with a cine-film camera, and pedal reaction forces were recorded from a force transducer mounted in the pedal. The muscular work for the hip, knee and ankle joint muscles was calculated using a model based upon dynamic mechanics and described elsewhere. The total work during one pedal revolution significantly increased with increased work load but did not increase with increased pedalling rate at the same braking force. The relative proportions of total positive work at the hip, knee and ankle joints were also calculated. Hip and ankle extension work proportionally decreased with increased work load. Pedalling rate did not change the relative proportion of total work at the different joints.     

Effect of pedal cadence on the accumulated oxygen deficit, maximal aerobic power and blood lactate transition thresholds of high-performance junior endurance cyclists

In this study we investigated the effect of pedal cadence on the cycling economy, accumulated oxygen deficit (AOD), maximal oxygen consumption (VO2max) and blood lactate transition thresholds of ten high-performance junior endurance cyclists [mean (SD): 17.4 (0.4) years; 183.8 (3.5) cm, 71.56 (3.75) kg]. Cycling economy was measured on three ergometers with the specific cadence requirements of: 90-100 rpm for the road dual chain ring (RDCR90-100 rpm) ergometer, 120-130 rpm for the track dual chain ring (TDCR120-130 rpm) ergometer, and 90-130 rpm for the track single chain ring (TSCR90-130 rpm) ergometer. AODs were then estimated using the regression of oxygen consumption (VO2) on power output for each of these ergometers, in conjunction with the data from a 2-min supramaximal paced effort on the TSCR90-130 rpm ergometer. A regression of VO2 on power output for each ergometer resulted in significant differences (P<0.001) between the slopes and intercepts that produced a lower AOD for the RDCR90-100 rpm [2.79 (0.43) l] compared with those for the TDCR120-130 rpm [4.11 (0.78) l] and TSCR90-130 rpm [4.06 (0.84) l]. While there were no statistically significant VO2max differences (P = 0.153) between the three treatments [RDCR90-100 rpm: 5.31 (0.24) l x min(-1); TDCR120-130 rpm; 5.33 (0.25) 1 x min(-1); TSCR90-130 rpm: 5.44 (0.27) l x min(-1)], all pairwise comparisons of the power output at which VO2max occurred were significantly different (P<0.001). Statistically significant differences were identified between the RDCR90-100 rpm and TDCR120-130 rpm tests for power output (P = 0.003) and blood lactate (P = 0.003) at the lactate threshold (Thla-), and for power output (P = 0.005) at the individual anaerobic threshold (Thiat). Our findings emphasise that pedal cadence specificity is essential when assessing the cycling economy, AOD and blood lactate transition thresholds of high-performance junior endurance cyclists.     

Linear increase in optimal pedal rate with increased power output in cycle ergometry

This experiment was designed to estimate the optimum pedal rates at various power outputs on the cycle ergometer. Five trained bicycle racers performed five progressive maximal tests on the ergometer. Each rode at pedal rates of 40, 60, 80, 100, and 120 rev X min-1. Oxygen uptake and heart rate were determined from each test and plotted against pedal rate for power outputs of 100, 150, 200, 250, and 300 W. Both VO2 and heart rate differed significantly among pedal rates at equivalent power outputs, the variation following a parabolic curve. The low point in the curve was taken as the optimal pedal rate; i.e., the pedal rate which elicited the lowest heart rate or VO2 for a given power output. When the optimum was plotted against power output the variation was linear. These results indicate that an optimum pedal rate exists in this group of cyclists. This optimum pedal rate increases with power output, and when our study is compared to studies in which elite racers, or non-racers were used, the optimum seems to increase with the skill of the rider.     

Spinal Loads during Cycling on an Ergometer

Cycling on an ergometer is an effective exercise for improving fitness. However, people with back problems or previous spinal surgery are often not aware of whether cycling could be harmful for them. To date, little information exists about spinal loads during cycling. A telemeterized vertebral body replacement allows in vivo measurement of implant loads during the activities of daily living. Five patients with a severe compression fracture of a lumbar vertebral body received these implants. During one measurement session, four of the participants exercised on a bicycle ergometer at various power levels. As the power level increased, the maximum resultant force and the difference between the maximum and minimum force (force range) during each pedal revolution increased. The average maximum-force increases between the two power levels 25 and 85 W were 73, 84, 225 and 75 N for the four patients. The corresponding increases in the force range during a pedal revolution were 84, 98, 166 and 101 N. There were large variations in the measured forces between the patients and also within the same patient, especially for high power levels. In two patients, the maximum forces during high-power cycling were higher than the forces during walking measured on the same day. Therefore, the authors conclude that patients with back problems should not cycle at high power levels shortly after surgery as a precaution.     

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.     

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.     

Torque-velocity relationship in isokinetic cycling exercise

Seven healthy female subjects performed brief (less than 10 s) periods of maximal exercise on a constant-velocity cycle ergometer, over the functional range of pedaling velocities, and an isometric contraction with each leg. There was an inverse relationship between peak torque and pedal crank velocity in all subjects; isometric torque was (mean +/- SE) 19.8 +/- 8.3% greater than the torque recorded at the slowest velocity of 11 rpm. The torque-velocity relationship was described best by a single exponential equation: y = 189.6 X e-0.0834x, where y is peak torque in Newton . meters and x is crank velocity in revolutions per minute. Peak power was a parabolic function of crank velocity; the data were fitted suitably by a second-order polynomial equation: y = -0.0589x2 + 14.504x + 47.092, where y is peak power in watts and x is crank velocity in revolutions per minute. Maximal peak power occurred at crank velocities ranging from 120 to 160 rpm, when the torque was 0.36 +/- 0.06 of the maximal isometric tension. These results demonstrate the importance of recording velocity in measurements of dynamic maximal power.     

Sprint performance-duration relationships are set by the fractional duration of external force application

We hypothesized that the maximum mechanical power outputs that can be maintained during all-out sprint cycling efforts lasting from a few seconds to several minutes can be accurately estimated from a single exponential time constant (k(cycle)) and two measurements on individual cyclists: the peak 3-s power output (P(mech max)) and the maximum mechanical power output that can be supported aerobically (P(aer)). Tests were conducted on seven subjects, four males and three females, on a stationary cycle ergometer at a pedal frequency of 100 rpm. Peak mechanical power output (P(mech max)) was the highest mean power output attained during a 3-s burst; the maximum power output supported aerobically (P(aer)) was determined from rates of oxygen uptake measured during a progressive, discontinuous cycling test to failure. Individual power output-duration relationships were determined from 13 to 16 all-out constant load sprints lasting from 5 to 350 s. In accordance with the above hypothesis, the power outputs measured during all-out sprinting efforts were estimated to within an average of 34 W or 6.6% from P(mech max), P(aer), and a single exponential constant (k(cycle) = 0.026 s(-1)) across a sixfold range of power outputs and a 70-fold range of sprint trial durations (R2 = 0.96 vs. identity, n = 105; range: 180 to 1,136 W). Duration-dependent decrements in sprint cycling power outputs were two times greater than those previously identified for sprint running speed (k(run) = 0.013 s(-1)). When related to the respective times of pedal and ground force application rather than total sprint time, decrements in sprint cycling and running performance followed the same time course (k = 0.054 s(-1)). We conclude that the duration-dependent decrements in sprinting performance are set by the fractional duration of the relevant muscular contractions.     

The influence of circadian rhythm on muscle activity and efficient force production during cycling at different pedal rates.

The aim of this study was to examine the pedal rate and chronobiological impacts on muscle activity pattern and propulsive force production during cycling. Ten male competitive cyclists performed at 06:00 and 18:00 h a submaximal exercise on a cycle ergometer at a power output which elicited 50% of their respective W(max). The exercise was divided into 4 periods lasting 5 min each during which subjects were requested to use different pedal rates (free pedal rate, 70, 90 and 120 rev min-1) in random order. The study demonstrated that, under high pedal rate, several muscles exhibited a phase advance of activity. These modifications of temporal organization of muscle activity were not sufficient to keep an identical propulsive torque pattern. Time to peak torque was delayed when pedal rate increased. The effects of circadian fluctuation on electromyographic activity were limited to a later M. rectus femoris burst end and shorter activity duration for M. tibialis anterior at 06:00 h. From the results of this study, it seems that the influence of pedal rate in the range of torque fluctuation would depend on time-of-day of testing. The decrease in torque fluctuation due to pedal rate increase is reinforced when testing in the early morning. Taking this specific variable into consideration, the chronobiological effect increases the impact of pedal rate variations.     

Effect of power, pedal rate, and force on average muscle fiber conduction velocity during cycling.

Muscle fiber conduction velocity (MFCV) provides indications on motor unit recruitment strategies due to the relation between conduction velocity and fiber diameter. The aim of this study was to investigate MFCV of thigh muscles during cycling at varying power outputs, pedal rates, and external forces. Twelve healthy male participants aged between 19 and 30 yr cycled on an electronically braked ergometer at 45, 60, 90, and 120 rpm. For each pedal rate, subjects performed two exercise intensities, one at an external power output corresponding to the previously determined lactate threshold (100% LT) and the other at half of this power output (50% LT). Surface electromyogram signals were detected during cycling from vastus lateralis and medialis muscles with linear adhesive arrays of eight electrodes. In both muscles, MFCV was higher at 100% LT compared with 50% LT for all average pedal rates except 120 rpm (mean +/- SE, 4.98 +/- 0.19 vs. 4.49 +/- 0.18 m/s; P < 0.001). In all conditions, MFVC increased with increasing instantaneous knee angular speed (from 4.14 +/- 0.16 to 5.08 +/- 0.13 m/s in the range of instantaneous angular speeds investigated; P < 0.001). When MFCV was compared at the same external force production (i.e., 90 rpm/100% LT vs. 45 rpm/50% LT, and 120 rpm/100% LT vs. 60 rpm/50% LT), MFCV was higher at the faster pedal rate (5.02 +/- 0.17 vs. 4.64 +/- 0.12 m/s, and 4.92 +/- 0.19 vs. 4.49 +/- 0.11 m/s, respectively; P < 0.05) due to the increase in inertial power required to accelerate the limbs. It was concluded that, during repetitive dynamic movements, MFCV increases with the external force developed, instantaneous knee angular speed, and average pedal rate, indicating progressive recruitment of large, high conduction velocity motor units with increasing muscle force.     

Effects of isokinetic training of the knee extensors on isometric strength and peak power output during cycling

Isokinetic training of right and left quadriceps femoris was undertaken three times per week for 16 weeks. One group of subjects (n = 13) trained at an angular velocity of 4.19 rad.s-1 and a second group (n = 10) at 1.05 rad.s-1. A control group (n = 10) performed no training. Maximal voluntary contraction (MVC) of the quadriceps, and peak pedal velocity nu p,peak) and peak power output (Wpeak) during all-out cycling (against loads equivalent to 9, 10, 11, 12, 13 and 14% MVC) were assessed before and after training. The two training groups did not differ significantly from each other in their training response to any of the performance variables (P > 0.05). No significant difference in MVC was observed for any group after the 16-week period (P = 0.167). The post-training increases in average Wpeak (7%) and nu p,peak (6%) during the cycle tests were each significantly different from the control group response (P = 0.018 and P = 0.008, respectively). It is concluded that 16 weeks of isokinetic strength training of the knee extensors is able to significantly improve nu p, peak and Wpeak during spring cycling, an activity which demands considerable involvement of the trained muscle group but with its own distinct pattern of coordination.     

Blood lactate vs. exhaustive exercise to evaluate aerobic fitness

This study compared the predictive power of a lactate-related index determined during submaximal cycle exercise to that of an exhaustive cycle ergometer test for evaluating the endurance exercise capacity of soldiers. The subjects (n = 48 males) performed a continuous exercise test to voluntary exhaustion on the cycle ergometer. Power output (PO) increased by 50 W steps each fourth min, with determinations of heart rate (HR), RPE and blood lactate concentrations (HLa) just prior to each PO increase. The PO at a 4 mmol L(-1) HLa concentration (WOBLA) was interpolated; based on the time to exhaustion the maximal PO that could be maintained for 6 min (Wmax6) was calculated from previously documented formulae. Subjects were timed during a 3000 m cross-country run. Both the cycle test and the run were performed again 3 months later, as was an additional 3000 m run with full military equipment weighing about 21 kg. All 3000 m times were significantly correlated (p less than 0.05) with both Wmax6 and WOBLA; similar predictive power was demonstrated for both Wmax6 and WOBLA, suggesting that accuracy in evaluation would not be sacrificed by substituting the submaximal for the exhaustive exercise test. HR and RPE-related indices showed markedly lower predictive power. The results extend the previously documented relationship between HLa during treadmill ergometry and running performance to include the use of cycle ergometry for the evaluation of running performance. The results also proved applicable to running performance while load carrying.     

Cycling as a novel approach to resistance training increases muscle strength, power, and selected functional abilities in healthy older women.

Cycling on a mechanically braked cycle ergometer was used as a novel approach to compare the effects of three different 16-wk resistance-training programs on isometric force, power output, and selected functional abilities in 31 healthy 65- to 74-yr-old women. Training was conducted three times per week. During each session, individuals of the speed group performed 8 sets of 16 pedal revolutions at 40% of the maximal resistance to complete two revolutions (2 RM); strength group performed 8 sets of 8 revolutions at 80% of 2 RM; and combination group performed 4 sets of 16 revolutions at 40% and 4 sets of 8 revolutions at 80% of 2 RM. During each set, all participants were required to pedal as fast as possible with a 2-min interval between sets. All training groups significantly increased force, power, and functional abilities (maximal treadmill walking speed, vertical jumping, and box stepping) at week 8 (in the range from 6.5 to 20.8%) with no further improvement at week 16 (except maximal treadmill walking speed), but no significant differences were observed between the three groups. The novel approach to performing both low- and high-resistance training, based on the use of a cycle ergometer, has been shown to be effective in improving strength, power, and functional abilities in a group of healthy women. Even fit older women can still improve in functional abilities. Interestingly, the "high-speed" and "low-speed" programs induced an increase in both power and strength of similar magnitude.     

Alterations in plasma volume, electrolytes and protein during incremental exercise at different pedal speeds

We investigated the effects of pedal speed on changes in plasma volume, electrolytes and protein during incremental exercise. Ten adult males participated in two, 30 minute incremental cycle ergometer exercise tests at room temperature (22° C, rh=56%). Exercise load was increased from 20 to 70% of peak . Five minutes were spent at each of six stages which were equally spaced in exercise intensity. Subjects pedaled at 50 (50 RPM) and 90 (90 RPM) rev · min^–1. Venous blood samples were drawn prior to exercise and during the last minute of each stage. Relative plasma volume changes showed a progressive hemoconcentration during the exercise. There were no significant differences due to pedal speed as plasma volume loss averaged –7.3% during exercise. [Na+], [Cl–], and [K+] increased significantly during exercise but were not influenced by pedal speed. Changes in plasma protein and albumin concentrations indicated that there was a loss of globulin from the vascular volume in both conditions and an addition of albumin to the plasma in 50 RPM. The difference in plasma albumin dynamics was possibly related to an effect of pedal speed on movement of fluid in the lymphatic vessels of the legs.This work was supported in part by Grants from the Theresa Monaco Endowment of the University of Houston College of Education and Nautilus Sports/Medical Industries     

Muscle mass as a factor limiting physical work

Maximal exercise has been performed by eight men and eight women, using four types of ergometer (2-leg, 1-leg, arm + shoulder, and arm) while breathing room air and while breathing 12% O2. Results have been related to anthropometric estimates of muscle mass in the active limbs. Although significant sex differences of O2 transfer and power output are shown, the sex-specific aerobic performance was roughly proportional to active muscle volume (both when comparing individuals on a given type of ergometer and when comparing average scores of the several types of ergometer). However, the relationship was closer for steady power output than for peak O2 intake (where the scores for arm work were boosted by the use of accessory muscles and by hyperventilation). When breathing 12% O2, the 2-leg performance was substantially reduced (an average of 28.7% for O2 transport and 19.2% for power output). This effect dropped to 9.1% for O2 transport and 12% for power output in one-leg ergometry and was negligible for arm or arm plus shoulder work. It is argued that because of difficulty in perfusing small muscles, arm work is limited largely by the intrinsic power of the active muscles, that single-leg ergometry is limited rather equally by central circulatory and muscular factors, and that two-leg ergometry is almost entirely dependent on the central circulatory transport of O2.     

Altered single cell force-velocity and power properties in exercise-trained rat myocardium.

Myocardial function is enhanced by endurance exercise training, but the cellular mechanisms underlying this improved function remain unclear. The ability of the myocardium to perform external work is a critical aspect of ventricular function, but previous studies of myocardial adaptation to exercise training have been limited to measurements of isometric tension or unloaded shortening velocity, conditions in which work output is zero. We measured force-velocity properties in single permeabilized myocyte preparations to determine the effect of exercise training on loaded shortening and power output. Female Sprague-Dawley rats were divided into sedentary control (C) and exercise trained (T) groups. T rats underwent 11 wk of progressive treadmill exercise. Myocytes were isolated from T and C hearts, chemically skinned, and attached to a force transducer. Shortening velocity was determined during loaded contractions at 15 degrees C by using a force-clamp technique. Power output was calculated by multiplying force times velocity values. We found that unloaded shortening velocity was not significantly different in T vs. C myocytes (T = 1.43 muscle lengths/s, n = 46 myocytes; C = 1.12 muscle lengths/s, n = 43 myocytes). Training increased the velocity of loaded shortening and increased peak power output (peak power = 0.16 P/P(o) x muscle length/s for T myocytes; peak power = 0.10 P/P(o) x muscle length/s for C myocytes, where P/P(o) is relative tension). We found no effect of training on myosin heavy chain isoform content. These results suggest that training alters power output properties of single cardiac myocytes and that this adaptation may improve the work capacity of the myocardium.     

Comparison of the Wingate and Bosco anaerobic tests

The purpose of this study was to compare the Wingate cycling and Bosco repeated jumps anaerobic tests. Eleven men (21.36 +/- 1.6 years; 179.1 +/- 9.3 cm; 78.7 +/- 11.0 kg) and 9 women (21.89 +/- 3.66 years; 171.8 +/- 10.0 cm; 75.9 +/- 21.4 kg), all university athletes, volunteered to participate. Subjects performed each test in random order. The tests consisted of a 30-second Wingate test and a 60-second Bosco test. The Wingate test was conducted using a Monark cycle ergometer and the Bosco test was conducted on a force platform. Following the performance of each test, peak lactate concentrations were determined. Average and peak power values were statistically greater in men and on the Bosco test. Peak lactate values were statistically greater in men but did not differ based on test. Correlations between peak lactate concentrations between tests and lactate values with peak or average power were not statistically significant. The relationship between peak power between tests was statistically significant among men, but not women. The results of the study indicated that the Bosco and Wingate tests, which both measure anaerobic characteristics, appear to measure different aspects of anaerobic power and capacity. The Bosco test also may be inappropriate for athletes who are not well trained in jumping.     

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.