Optimal velocity for maximal power production in non-isokinetic cycling is related to muscle fibre type composition

Oxygen saturation in the triceps brachii muscle during an arm Wingate test: the role of training and power output

The purpose of this study was to investigate the role of training and power output on muscle oxygen desaturation during and resaturation after an arm Wingate test (WAnT). Two groups of subjects were studied; the first group consisted of nine athletes participating in upper arm anaerobic sports and the second group of 11 university students. As a consequence, the group of athletes (HP) produced higher peak and mean power output (p < 0.01) than the group of university students (LP). Muscle oxygenation status was evaluated by using near infrared spectroscopy at the triceps brachii. The HP group exhibited 17.6 +/- 8.0% less muscle oxygen desaturation than the LP group (p < 0.05) but similar muscle total hemoglobin during exercise and faster (p < 0.05) muscle oxygen resaturation during recovery (tau = 12.4 +/- 5.2 sec in HP vs. tau = 24.2 +/- 11.0 sec in LP). These results indicate that the HP group exhibits less muscle desaturation during an arm WAnT and has a faster resaturation rate, probably attributed to differences in muscle mass, muscle fiber recruitment capability, and ATP production through anaerobic pathways.

Relationship between vertical jumping performance and anthropometric characteristics during growth in boys and girls

The aim of the study was to compare vertical jumping performances in boys and girls during growth. The maximum heights attained in a countermovement jump (CMJ) and squat jump (SJ) were measured using an Ergojump Bosco System. Average power output (PO) was recorded, and percentage of fast-twitch (%FT) muscle fiber distribution was estimated during the rebound jump. Differences in the maximum CMJ and SJ (CMJ-SJ) heights were calculated. Regressions between PO and age, lean body mass (LBM), and leg muscle volume (LMV), respectively, were computed for 240 boys and 239 girls (aged 11-16 years). Height, LMV, and body mass values were larger in boys than girls aged 14 years. Both groups had a similar body mass index independently of age. The CMJ, SJ, PO, and %FT were larger in boys than in girls between 12 and 16 years of age. Strong correlations were found between PO and age in the population as a whole, and between PO and LBM, PO and LMV in each group. The CMJ-SJ decreased with increasing age in both groups without significant differences. Conclusion Jumping performance increases during growth, with gender differences manifesting from 14 years onwards due to the much greater increase in leg length and LMV in boys than in girls.

Understanding sprint-cycling performance: the integration of muscle power, resistance, and modeling

Sprint-cycling performance is paramount to competitive success in over half the world-championship and Olympic races in the sport of cycling. This review examines the current knowledge behind the interaction of propulsive and resistive forces that determine sprint performance. Because of recent innovation in field power-measuring devices, actual data from both elite track- and road-cycling sprint performances provide additional insight into key performance determinants and allow for the construction of complex models of sprint-cycling performance suitable for forward integration. Modeling of various strategic scenarios using a variety of field and laboratory data can highlight the relative value for certain tactically driven choices during competition.

Anaerobic capacity of the upper arms in top-level team handball players

PURPOSE

Handball is a sport with high anaerobic demands in lower body as has been indicated by Wingate test (WT) performed with the legs, but there are no data available concerning power production during a WT performed with the arms in handball players (HndP). Therefore, the purpose of this study was to explore the arm anaerobic profile of HndP during a WT.

METHODS

Twenty-one elite HndP and 9 physical education students (CON), performed a 30-s arm WT. Power production and muscle oxygenation were recorded.

RESULTS

Peak power (PP) as well as mean power (MP) was higher (P = .017 and 0.03, and ES = 1.00 and 0.86, respectively) for HndP (HndP PP: 7.6 +/- 0.8 W x kg(-1); CON PP: 6.7 +/- 1.1 W x kg(-1); HndP MP 5.3 +/- 0.6 W x kg(-1); CON MP 4.7 +/- 0.9 W x kg(-1)) with no significant difference in fatigue index between the two groups. Muscle oxygen saturation (StO2) declined approximately 30% with exercise with no differences between groups. During recovery the HndP group had higher StO2 (P = .01, ES= 3.04), total hemoglobin and oxygenated hemoglobin compared with the CON group (P < .01 ES = 3.29 and 0.99, respectively). StO2 returned to resting values in 29.5 +/- 2.3 s in HndP, whereas this variable did not recover after 2 min in CON.

CONCLUSIONS

The arm anaerobic capacity of the HndP was "excellent," significantly higher than that by the control group. Moreover, HndP exhibited faster recovery of StO2 compared with the control group. The greater power output and the faster muscle reoxygenation of arms in HndP can be attributed to specific training adaptations related to high performance in handball.

Somatosensory feedback from the limbs exerts inhibitory influences on central neural drive during whole body endurance exercise

We investigated whether somatosensory feedback from contracting limb muscles exerts an inhibitory influence on the determination of central command during closed-loop cycling exercise in which the subject voluntarily determines his second-by-second central motor drive. Eight trained cyclists performed two 5-km time trials either without (5K(Ctrl)) or with lumbar epidural anesthesia (5K(Epi); 24 ml of 0.5% lidocaine, vertebral interspace L(3)-L(4)). Percent voluntary quadriceps muscle activation was determined at rest using a superimposed twitch technique. Epidural lidocaine reduced pretime trial maximal voluntary quadriceps strength (553 +/- 45 N) by 22 +/- 3%. Percent voluntary quadriceps activation was also reduced from 97 +/- 1% to 81 +/- 3% via epidural lidocaine, and this was unchanged following the 5K(Epi), indicating the presence of a sustained level of neural impairment throughout the trial. Power output was reduced by 9 +/- 2% throughout the race (P < 0.05). We found three types of significant effects of epidural lidocaine that supported a substantial role for somatosensory feedback from the exercising limbs as a determinant of central command throughout high-intensity closed-loop cycling exercise: 1) significantly increased relative integrated EMG of the vastus lateralis; 2) similar pedal forces despite the reduced number of fast-twitch muscle fibers available for activation; 3) and increased ventilation out of proportion to a reduced carbon dioxide production and heart rate and increased blood pressure out of proportion to power output and oxygen consumption. These findings demonstrate the inhibitory influence of somatosensory feedback from contracting locomotor muscles on the conscious and/or subconscious determination of the magnitude of central motor drive during high intensity closed-loop endurance exercise.

Potential role of optimal velocity as a qualitative factor of physical functional performance in women aged 72 to 96 years

OBJECTIVE

To assess the relationship of maximal leg power and its corresponding determinants (eg, optimal velocity and optimal torque) measured during maximal voluntary knee extension to physical functional performance of older women.

DESIGN

Descriptive.

SETTING

Community retirement homes.

PARTICIPANTS

Women (N=39) aged 72 to 96 years.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Volunteers performed in sitting position maximal knee extensions on an Ergopower dynamometer to calculate maximal leg power, optimal velocity, and optimal torque. Three standardized tests were also performed to evaluate physical performance: walking speed over 6m, time taken to rise 5 times from a chair, and time to climb 6 stairs.

RESULTS

On multiple regression analysis, leg power (mean, 1.37+/-0.80 W/kg) significantly correlated with physical performance as measured by 6-m walking speed (mean, .85+/-.40 m/s), chair-stand time (mean, 16.3+/-7.7s), and stair-climb time (mean, 7+/-4s), describing 16% to 33% of the variance. Optimal velocity (mean, 1.79+/-1.20 rad/s) also significantly correlated with 6-m walking speed, chair-stand time, and stair-climb time, describing 46% to 89% of the variance. Optimal torque (50.8+/-16.9 Nm) did not correlate with physical performance.

CONCLUSIONS

Maximal power and moreover optimal velocity were thus found to be determinants of physical performance, both appearing as significant mobility factors in older adults. This may provide more focus on velocity-oriented training as a means of improving functional status.

Torque-velocity and power-velocity relationships during isokinetic trunk flexion and extension

BACKGROUND

No study has reported the possibility of establishing torque-velocity and power-velocity relationships for both flexor and extensor trunk muscles. The present study therefore sought to assess these relationships during isokinetic exercise.

METHODS

Nine healthy male subjects performed series of isokinetic trunk flexions and extensions at six different velocities ranging from 45 degrees s(-1) to 120 degrees s(-1). Trunk flexor and extensor muscles were, respectively, assessed on two separate days. All experiments used a Biodex dynamometer.

FINDINGS

Torque-velocity relationships were significantly well described by a linear relationship for both trunk flexor (P<0.01; r=0.92-0.99) and extensor muscles (P<0.05; r=0.82-0.97) in all subjects. Power-velocity relationships exhibited a parabolic shape for all subjects (P<0.05; r=0.96-0.99) for both muscle groups.

INTERPRETATION

Results showed that trunk muscle torque- and power-velocity relationships can be assessed during isokinetic exercise. The findings were in agreement with previous studies of lower and upper limbs. This kind of measurement can therefore be applied in assessing low-back pain patients during rehabilitation.

Does an eccentric chainring improve conventional parameters of neuromuscular power?

This study compared the conventional parameters of anaerobic cycling power in physically active non-cyclists using the Pro-Race system and a traditional chainring. The force-velocity test was chosen for this purpose because it is the shortest validated cycling laboratory test in which each parameter of maximal anaerobic power can be estimated. The power output (W(max)) and the force at which W(max) is produced (F(opt)) were significantly improved with the eccentric chainring (1100+/-227W versus 1006+/-197W and 1.39+/-0.15N/kg body mass versus 1.13+/-0.16N/kg body mass with the eccentric and round designs, respectively; P<0.006 and P<0.0004, respectively). The power gained (delta power) was significantly correlated with the eccentric chainring F(opt) (r=0.649; P<0.05), the mid-thigh circumference (r=0.685; P<0.05), the estimated lean thigh volume (r=0.765; P<0.01) and the estimated lean lower limb volume (r=0.665; P<0.05). We concluded that the eccentric chainring significantly improved the estimated anaerobic power output during a force-velocity test by increasing the force component, F(opt). Cautious interpretation of our results suggests that the subjects with physical attributes that contribute to developing high forces may have a significant advantage in performing with the eccentric chainring.

Influence of resistive load on power output and fatigue during intermittent sprint cycling exercise in children

This study examined the effects of two resistive loads on fatigue during repeated sprints in children. Twelve 11.8 (0.2) year old boys performed a force-velocity test to determine the load (Fopt) corresponding to the optimal pedal rate. On two separate occasions, ten 6-s sprints interspersed with 24-s recovery intervals were performed on a friction-loaded cycle ergometer, against a load equal to Fopt or 50%Fopt. Although mean power output (MPO) was higher in the Fopt [397 (24) and 356 (19) W, P < 0.01], the decline in MPO over the 10 sprints was similar in Fopt [8.8 (1.9) %] and 50%Fopt [9.0 (2.4) %]. In contrast, peak power (PPO) was not different in sprint 1 between the two conditions [459 (24) and 460 (28) W], but was decreased only in 50%Fopt [11.4 (3.2) %, P < 0.01], while it was maintained in the Fopt despite the higher total work during each sprint. Fatigue within each sprint (percent drop from peak to end power output) was also higher in the 50%Fopt compared with the Fopt [32 (2.5) vs. 10 (1.6) %, P < 0.01]. Peak and mean pedal rate in Fopt condition were close to the optimum (Vopt), while a large part of the sprint time in 50%Fopt was spent far from Vopt. The present study shows that sprinting against Fopt reduces fatigue within and between repeated short sprints in children. It is suggested that fatigue during repeated sprints is modified when pedal rate is not close to Vopt, according to the parabolic power versus pedal rate relationship.

Why does power output decrease at high pedaling rates during sprint cycling?

PURPOSE

The objective of this study was to partly explain, from electromyographical (EMG) activity, the decrease in power output beyond optimal pedaling rate (PRopt) during sprint cycling.

METHODS

Eleven cyclists performed four 8-s nonisokinetic sprints on a cycle ergometer against four randomized friction loads (0.5, twice 0.75, and 0.9 N x kg(-1) of body mass). Power output and EMG activity of both right and left gluteus maximus, rectus femoris, biceps femoris, and vastus lateralis were measured continuously. Individual crank cycles were analyzed. Crank angles corresponding to the beginning and the peak of each downstroke and EMG burst onset and offset crank angles were computed. Moreover, crank angles corresponding to the beginning and the end of muscle force response were determined assuming a 100-ms lag time between the EMG activity and the relevant force response (or electromechanical delay).

RESULTS

Muscle coordination (EMG onset and offset) was altered at high pedaling rates. Thus, crank angles corresponding to muscle force response increased significantly with pedaling rate. Consequently, at pedaling rates higher than the optimal pedaling rate, force production of lower-limb extensor muscles was shifted later in the crank cycle. Mechanical data confirmed that downstrokes occurred later in the crank cycle when pedaling rate increased. Hence, force was produced on the pedals during less effective crank cycle sectors of the downstroke and during the beginning of the upstroke.

CONCLUSION

During nonisokinetic sprint cycling, the decrease in power output when pedaling rates increased beyond PRopt may be partly explained by suboptimal muscle coordination.

Maximal torque- and power-pedaling rate relationships for elite sprint cyclists in laboratory and field tests

Performance models provide an opportunity to examine cycling in a broad parameter space. Variables used to drive such models have traditionally been measured in the laboratory. The assumption, however, that maximal laboratory power is similar to field power has received limited attention. The purpose of the study was to compare the maximal torque- and power-pedaling rate relationships during "all-out" sprints performed on laboratory ergometers and on moving bicycles with elite cyclists. Over a 3-day period, seven male (mean +/- SD; 180.0 +/- 3.0 cm; 86.2 +/- 6.1 kg) elite track cyclists completed two maximal 6 s cycle ergometer trials and two 65 m sprints on a moving bicycle; calibrated SRM powermeters were used and data were analyzed per revolution to establish torque- and power-pedaling rate relationships, maximum power, maximum torque and maximum pedaling rate. The inertial load of our laboratory test was (37.16 +/- 0.37 kg m(2)), approximately half as large as the field trials (69.7 +/- 3.8 kg m(2)). There were no statistically significant differences between laboratory and field maximum power (1791 +/- 169; 1792 +/- 156 W; P = 0.863), optimal pedaling rate (128 +/- 7; 129 +/- 9 rpm; P = 0.863), torque-pedaling rate linear regression slope (-1.040 +/- 0.09; -1.035 +/- 0.10; P = 0.891) and maximum torque (266 +/- 20; 266 +/- 13 Nm; P = 0.840), respectively. Similar torque- and power-pedaling rate relationships were demonstrated in laboratory and field settings. The findings suggest that maximal laboratory data may provide an accurate means of modeling cycling performance.

Optimized versus corrected peak power during friction-braked cycle ergometry in males and females

The aim of this study was to compare optimization and correction procedures for the determination of peak power output during friction-loaded cycle ergometry. Ten male and 10 female sports students each performed five 10-s sprints from a stationary start on a Monark 864 basket-loaded ergometer. Resistive loads of 5.0, 6.5, 8.0, 9.5, and 11.0% body weight were administered in a counterbalanced order, with a recovery period of 10 min between sprints. Peak power was greater and occurred earlier, with less work having been done before the attainment of peak power, when the data were corrected to account for the inertial and frictional characteristics of the ergometer. Corrected peak power was independent of resistive load (P > 0.05), whereas uncorrected peak power varied as a quadratic function of load (P < 0.001). For males and females, optimized peak power (971 +/- 122 and 668 +/- 37 W) was lower (P < 0.01) than either the highest (1074 +/- 111 and 754 +/- 56 W respectively) or the mean (1007 +/- 125 and 701 +/- 45 W respectively) of the five values for corrected peak power. Optimized and mean corrected peak power were highly correlated both in males (r = 0.97, P < 0.001) and females (r = 0.96, P < 0.001). The difference between optimized and mean corrected peak power was 37 +/- 30 W in males and 33 +/- 14 W in females, of which approximately 15 W was due to the correction for frictional losses. We conclude that corrected peak power is independent of resistive load in males and females.

Power Output and Muscle Myosin Heavy Chain Composition in Young and Elderly Men

PURPOSE

Aging is associated with a decline in muscle volume, power output, and the velocity at which peak power (Vopt) occurs. The current study aimed to examine the relationship between lower-limb power output characteristics, muscle myosin heavy chain (MHC) composition, and lean limb volume.

METHODS

Lower-limb power output during repeated efforts on an inertial sprint cycle and single-leg thrusts on the modified Nottingham power rig was studied in seven young and seven old males in relation to muscle MHC isoform composition of the vastus lateralis.

RESULTS

Older subjects produced significantly lower power outputs and Vopt under all conditions (P < 0.01) and had lower proportions of fast MHC isoforms (P< 0.05). Peak power output during cycling was significantly related to lower-limb lean volume (r = 0.92, P < 0.05), whereas Vopt during sprint cycling was closely related to vastus lateralis MHC-II composition (r = 0.80, P < 0.05).

CONCLUSIONS

These results provide further evidence of the importance of fast myosin isoform composition in the maintenance of dynamic muscle function in later life and particularly for maximal cycling performance.

Performance following prolonged sub-maximal cycling at optimal versus freely chosen pedal rate

It was tested whether cyclists perform better during all-out cycling following prolonged cycling at the pedal rate resulting in minimum oxygen uptake (VO(2)), i.e. the energetically optimal pedal rate (OPR) rather than at the freely chosen pedal rate (FCPR). Nine trained cyclists cycled at 180 W to determine individual OPR and FCPR. Baseline performance was determined by measuring mean power output (W(5min)) and peak VO(2) during 5-min all-out cycling at FCPR. Subsequently, on two separate days, the cyclists cycled 2.5 h at 180 W at OPR and FCPR, with each bout followed by a 5-min all-out trial. FCPR was higher (P < 0.05) than OPR at 180 W (95 +/- 7 and 73 +/- 11 rpm, respectively). During the prolonged cycling, VO(2), heart rate (HR), and rate of perceived exertion (RPE) were 7-9% higher (P < 0.05) at FCPR than at OPR and increased (P < 0.05) 2-21% over time. During all-out cycling following prolonged cycling at OPR and FCPR, W(5min) was 8 and 10% lower (P < 0.05) than at baseline, respectively. Peak VO(2) was lower (P < 0.05) than at baseline only after FCPR. The all-out trial power output was reduced following 2.5 h of cycling at 180 W at both OPR and FCPR. However, this aspect of performance was similar between the two pedal rates, despite a higher physiological load (i.e. VO(2), HR, and RPE) at FCPR during prolonged cycling. Still, a reduced peak VO(2) only occurred after cycling at FCPR. Therefore, during prolonged sub-maximal cycling, OPR is at least as advantageous as FCPR for performance optimization in subsequent all-out cycling.

Peak anaerobic power in patients with COPD: gender related differences

The aim of the study was to investigate peak anaerobic power during all-out exercise in patients with COPD. Twenty patients (ten women, ten men) [FEV1=50.5 (7.6)% of predicted] and 11 healthy subjects (six women, five men) performed: (1) three maximal sprints on a cycle ergometer to measure peak anaerobic power (Pmax) and optimal velocity (Vopt), (2) assessment of whole-body composition by dual-energy X-ray absorptiometry (DEXA) and (3) assessment of mean habitual daily energy expenditure (MHDEE). Pmax was 30% lower in COPD than in healthy subjects [22.9 (7.1) vs. 32.8 (5.6) W kg-1 (legs FFM), P<0.001]. Nevertheless, Vopt was similar in both series. In COPD, Pmax was lower in women than in men [21.4 (7.7) vs. 23.8(6.4) W kg-1 (legs FFM), P<0.05]. Vopt was lower in women than in COPD men [72.6 (11.3) vs. 89.3 (13.8) rpm, P<0.05]. MHDEE was lower in COPD than in healthy subjects [8019 (1254) vs. 9093 (1660) kJ day-1]. In COPD, MHDEE was lower in women than in men (P<0.001). This study demonstrates that in COPD patients, the decrease in peak anaerobic power could play a role in their specific muscular dysfunction. Considerable differences were observed in peripheral muscle function, body composition and MHDEE between women and men. The skeletal muscle of women and men may therefore adapt to COPD in different ways.

Respiratory muscle performance with stretch-shortening cycle manoeuvres: maximal inspiratory pressure-flow curves

AIM

To test the hypothesis that the maximal inspiratory muscle (IM) performance, as assessed by the maximal IM pressure-flow relationship, is enhanced with the stretch-shortening cycle (SSC).

METHODS

Maximal inspiratory flow-pressure curves were measured in 12 healthy volunteers (35 +/- 6 years) during maximal single efforts through a range of graded resistors (4-, 6-, and 8-mm diameter orifices), against an occluded airway, and with a minimal load (wide-open resistor). Maximal inspiratory efforts were initiated at a volume near residual lung volume (RV). The subjects exhaled to RV using slow (S) or fast (F) manoeuvres. With the S manoeuvre, they exhaled slowly to RV and held the breath at RV for about 4 s prior to maximal inspiration. With the F manoeuvre, they exhaled rapidly to RV and immediately inhaled maximally without a post-expiratory hold; a strategy designed to enhance inspiratory pressure via the SSC.

RESULTS

The maximal inspiratory pressure-flow relationship was linear with the S and F manoeuvres (r2 = 0.88 for S and r2 = 0.88 for F manoeuvre, P < 0.0005 in all subjects). With the F manoeuvre, the pressure-flow relationship shifted to the right in a parallel fashion and the calculated maximal power increased by approximately 10% (P < 0.05) over that calculated with the S manoeuvre.

CONCLUSION

The maximal inspiratory pressure-flow capacity can be enhanced with SSC manoeuvres in a manner analogous to increases in the force-velocity relationship with SSC reported for skeletal muscles.

Peak leg muscle power, peak VO2 and its correlates with physical activity in 57 to 70-year-old women

The two aims of this study were first to measure short-term muscle power (STMP) by means of a cycling force-velocity test (cycling peak power: CPP) and a vertical jump test (jumping peak performance: JPP) and second, to examine the relationships between physical activity (PA) level, peak oxygen uptake (peak VO2) and STMP in healthy elderly women. Twenty-three independent community-dwelling elderly women (mean age: 64+/-4.4) performed on separate days, a peak oxygen uptake test on cycle ergometer, a cycling force-velocity test and a vertical jump test. A questionnaire (QUANTAP) was used to assess lifespan exercise habits. Four indices expressed in kJ day(-1) kg(-1) were calculated. Two indices represented average past PA level: 1/quantity of habitual physical activity (QHPA), 2/quantity of sports activities (QSA). Two indices represented the actual PA level: 3/actual quantity of habitual physical activity (AQHPA), 4/actual quantity of sports activities (AQSA). CPP (6.3+/-1.2 W kg(-1)) was closely correlated to JPP (14.8+/-3.4 cm) (r=0.80, P<0.001). AQHPA and AQSA were only positively associated with peak VO2 (ml min(-1) kg(-1)) (r=0.49; r=0.50, P<0.05, respectively). Past PA level was not related to fitness measurements. Results show that in this population: (1) jumping peak performance was closely related to CPP measured in the laboratory; (2) the cardio-respiratory fitness was related to the actual habitual physical activity level; (3) only age and anthropometric variables explained the actual performances in multivariate analysis.

Effects of load on ground reaction force and lower limb kinematics during concentric squats

The purpose of this study was to examine the effects of external load on vertical ground reaction force, and linear and angular kinematics, during squats. Eight males aged 22.1 +/- 0.8 years performed maximal concentric squats using loads ranging from 7 to 70% of one-repetition maximum on a force plate while linear barbell velocity and the angular kinematics of the hip, knee and ankle were recorded. Maximum, average and angle-specific values were recorded. The ground reaction force ranged from 1.67 +/- 0.20 to 3.21 +/- 0.29 times body weight and increased significantly as external load increased (P < 0.05). Bar linear velocity ranged from 0.54 +/- 0.11 to 2.50 +/- 0.50 m x s(-1) and decreased significantly with increasing external load (P < 0.05). Hip, knee and ankle angles at maximum ground reaction force were affected by external load (P < 0.05). The force-barbell velocity curves were fitted using linear models with coefficients (r2) ranging from 0.59 to 0.96. The results suggest that maximal force exertion during squat exercises is not achieved at the same position of the lower body as external load is increased. In contrast, joint velocity coordination does not change as load is increased. The force-velocity relationship was linear and independent from the set of data used for its determination.

Quadriceps maximal power and optimal shortening velocity in 335 men aged 23-88 years

The ability to develop adequate quadriceps muscle power may be highly predictive of subsequent disability among older persons. Rate as well as quantitative (sarcopenia) and qualitative (among other slowing of muscles) contributors to that age-related power decline are poorly known. The relationship of quadriceps maximal short-term power (P(max)) and corresponding optimal shortening velocity (upsilon(opt)) with age was assessed in 335 healthy men aged 23-88 years. The P(max) and upsilon(opt) were measured on a friction loaded non-isokinetic cycle ergometer. Anthropometric dimensions were used to estimate lean thigh volume (LTVest) and quadriceps mass. The decline in P(max) across the adult life span (10.7% per decade) was greater than the usually reported decrease in maximal muscle strength. Power decreased already after the fourth decade. Both muscle mass (4.1% decline for LTVest or 3.4% for quadriceps mass per decade) and upsilon(opt) (6.6% decline per decade) contributed to the decrease in power. Age contributed to the variability in P(max) independently to the LTVest/quadriceps mass and upsilon(opt). The age-related decrease pattern of P(max) reflects both stabilization (or even increase) of anthropometric measures (LTVest or quadriceps mass) from youth to middleage and systematic decline of upsilon(opt) already from the thirties. This implicates more focus on velocity-orientated training as a means of enhancing leg power and improving functional status.

Comparison between maximal power in the power-endurance relationship and maximal instantaneous power

The purpose of this study was to analyze the relevance of introducing the maximal power (P(m)) into a critical-power model. The aims were to compare the P(m) with the instantaneous maximal power (P(max)) and to determine how the P(m) affected other model parameters: the critical power ( P(c)) and a constant amount of work performed over P(c)(W'). Twelve subjects [22.9 (1.6) years, 179 (7) cm, 74.1 (8.9) kg, 49.4 (3.6) ml/min/kg] completed one 15 W/min ramp test to assess their ventilatory threshold (VT), five or six constant-power to exhaustion tests with one to measure the maximal accumulated oxygen deficit (MAOD), and six 5-s all-out friction-loaded tests to measure P(max) at 75 rpm, which was the pedaling frequency during tests. The power and time to exhaustion values were fitted to a 2-parameter hyperbolic model (NLin-2), a 3-parameter hyperbolic model (NLin-3) and a 3-parameter exponential model (EXP). The P(m) values from NLin-3 [760 (702) W] and EXP [431 (106) W] were not significantly correlated with the P(max) at 75 rpm [876 (82) W]. The P(c) value estimated from NLin-3 [186 (47) W] was not significantly correlated with the power at VT [225 (32) W], contrary to other models ( P <0.001). The W' from NLin-2 [25.7 (5.7) kJ] was greater than the MAOD [14.3 (2.7) kJ, P < 0.001] with a significant correlation between them (R = 0.76, P <0.01). For NLin-3, computation of W (P > P c), the amount of work done over P(C), yielded results similar to the W' value from NLin-2: 27.8 (7.4) kJ, which correlated significantly with the MAOD (R = 0.72, P <0.01). In conclusion, the P(m) was not related to the maximal instantaneous power and did not improve the correlations between other model parameters and physiological variables.

Muscle fiber type effects on energetically optimal cadences in cycling

Fast-twitch (FT) and slow-twitch (ST) muscle fibers vary in their mechanical and energetic properties, and it has been suggested that muscle fiber type distribution influences energy expenditure and the energetically optimal cadence during pedaling. However, it is challenging to experimentally isolate the effects of muscle fiber type on pedaling energetics. In the present study, a modeling and computer simulation approach was used to test the dependence of muscle energy expenditure on pedaling rate during submaximal cycling. Simulations were generated using a musculoskeletal model at cadences from 40 to 120 rev min(-1), and the dynamic and energetic properties of the model muscles were scaled to represent a range of muscle fiber types. Energy expenditure and the energetically optimal cadence were found to be higher in a model with more FT fibers than a model with more ST fibers, consistent with predictions from the experimental literature. At the muscle level, mechanical efficiency was lower in the model with a greater proportion of FT fibers, but peaked at a higher cadence than in the ST model. Regardless of fiber type distribution, mechanical efficiency was low at 40 rev min(-1), increased to a broad plateau between 60 and 100 rev min(-1) , and decreased substantially at 120 rev min(-1). In conclusion, muscle fiber type distribution was confirmed as an important determinant of the energetics of pedaling.

Diminution de la fonction musculaire dynamique dans la BPCO : étude préliminaire

BACKGROUND

The aim of the study was to investigate dynamic muscle function during all-out exercise in patients with chronic obstructive pulmonary disease (COPD) and to observe the relationship between body composition and skeletal muscle function.

MATERIAL AND METHODS

Eight patients (FEV1: 53.0 +/- 9.3%) performed three tests i) three maximal sprints on a specialised cycle ergometer to assess individual Velocity-Power relationship, and measure of maximal anaerobic power (Pmax), optimal velocity (Vopt), ii) assessment of whole-body and subregional fat-free mass (FFM) by dual-energy X-ray absorptiometry, iii) determination of maximal oxygen consumption.

RESULTS

Maximal anaerobic power and corresponding optimal velocity were 3.9 +/- 1.6 W x kg(-1) et 85.4 +/- 17.0 rpm, respectively. COPD showed a 30% decrease of Pmax, compared to healthy older subjects (5.6 +/- 1.1 W x kg(-1)). No such difference was observed with Vopt (85.4 +/- 13.0 rpm vs 86.8 +/- 9.5 rpm). Pmax and Vopt were highly significantly correlated with lower extremities FFM, but not with airflow obstruction parameters.

CONCLUSION

Our results showed that skeletal muscle function parameters such as Pmax and Vopt could characterise peripheral muscle weakness of COPD.

Longitudinal Changes of Maximal Short-Term Peak Power in Girls and Boys during Growth

PURPOSE

The aims of this study are twofold: first, to analyze the influence of age, body mass, and lean leg volume (LLV) on short-term leg peak power (Pmax) of young females and males during growth using multilevel regression analysis and, second, to compare the regression results of boys and girls.

METHODS

The individuals were 100 girls and 109 boys aged 7.5-17.5 yr old. Pmax, LLV, and mass were determined on two occasions using the cycling force-velocity test. The optimal force (Fopt) and pedaling frequency (Vopt) corresponded to the force and pedaling frequency at Pmax.

RESULTS

It was observed that the increase of Pmax doesn't depend on gender until the age of 14. From that age, Pmax values are significantly lower in girls than in boys. In girls, LLV is the main predictor of Pmax variance (68%; P < 0.001), whereas in boys it is age (57%; P < 0.001). Results of ANCOVA were that for the same leg length (LL), Vopt is significantly (P < 0.001) higher in boys than in girls. It also indicated that for the same LLV, there are no significant (P > 0.05) gender differences of Fopt.

CONCLUSION

These results illustrated that during the growth period, the increase of Pmax is significantly higher in boys than in girls. Qualitative muscular factors (Type II fiber, glycolytic ability, motor coordination, and motor unit activation) may account for the significantly higher Pmax production in boys than in girls. Precisely, the gender differences might be explained by neuromuscular determinants of contraction velocity. In conclusion, children should develop their neuromuscular determinants of contraction velocity rather than their lean leg volume.

A simple method for measurement of maximal downstroke power on friction-loaded cycle ergometer

The aim of this study was to propose and validate a post-hoc correction method to obtain maximal power values taking into account inertia of the flywheel during sprints on friction-loaded cycle ergometers. This correction method was obtained from a basic postulate of linear deceleration-time evolution during the initial phase (until maximal power) of a sprint and included simple parameters as flywheel inertia, maximal velocity, time to reach maximal velocity and friction force. The validity of this model was tested by comparing measured and calculated maximal power values for 19 sprint bouts performed by five subjects against 0.6-1 N kg(-1) friction loads. Non-significant differences between measured and calculated maximal power (1151+/-169 vs. 1148+/-170 W) and a mean error index of 1.31+/-1.20% (ranging from 0.09% to 4.20%) showed the validity of this method. Furthermore, the differences between measured maximal power and power neglecting inertia (20.4+/-7.6%, ranging from 9.5% to 33.2%) emphasized the usefulness of power correcting in studies about anaerobic power which do not include inertia, and also the interest of this simple post-hoc method.

Differences in morphology and force/velocity relationship between Senegalese and Italian sprinters

In order to investigate whether the supremacy of African sprinters is related to the leg extensor force/velocity relationship or to leg morphology, two groups of elite sprinters originating respectively from Senegal (S) and Italy (I) were compared in this respect. The groups included 13 S and 15 I male sprinters. Their mean best performances over 100 m during the preceding track and field season were 10.66 (0.3) and 10.61 (0.3) s (NS), respectively. Age, height and mass were similar in the two groups. The force/velocity relationship of the leg extensors was assessed during maximal half-squats on a guided horizontal barbell with masses of 20-140 kg added on the shoulders. Leg morphology was assessed by relating the sub-ischial length to the standing height (L/H) and by measuring the inertia in the vertical (IZ in kg.cm2), antero-posterior (IY, kg.cm2) and medio-lateral (IX, kg.m2) planes. The two groups developed non-different force and power when lifting the heaviest loads. Inversely, the lighter the load, the lower the force and power developed by S, as compared to I (P<0.001). S demonstrated greater L/H (P<0.001), and 26% lower IZ (P<0.01), 15% lower IY (P=0.09), and 14% lower IX (P=0.10). These results suggest that S and I sprinters were similar as regards the muscle abilities involved in slow maximal contractions. However, S demonstrated lower values in muscle abilities related to high-speed contractions, suggesting that S sprinters had a lower percentage of fast twitch fibres. This is likely to be compensated for by the lower level of internal work due to longer and lighter legs.

Short-term peak power changes in adolescents of similar anthropometric characteristics

PURPOSE

The present study was undertaken to examine changes of cycling peak power (P(max)), optimal pedaling frequency (Vopt), and optimal pedaling force (Fopt) with age in subjects with the same lean leg volume (LLV), leg length (LL), and percentage body fat (%BF).

METHOD

A total of 132 males aged 9.5-16.5 volunteered for this study. The population was divided into prepubertal (G1), pubertal (G2), and postpubertal (G3) groups. Within G1, G2, and G3, although the subjects were divided into three different age subgroups, there were no significant differences for LLV, %BF, and LL.

RESULTS

Results showed that within G1, G2, and G3, P(max) increased significantly with age. Optimal velocity (Vopt) increased significantly with age in G1, whereas optimal force (Fopt) increased significantly with age into the other groups (G2 and G3).

CONCLUSION

This study demonstrated that when anthropometric characteristics were controlled (LLV, LL, and %BF), P(max) and its two components (Vopt and Fopt) still increased with age. This indicates that other factors of qualitative nature have to be considered when determining P(max), Vopt, and Fopt.

Muscle fibre type, efficiency, and mechanical optima affect freely chosen pedal rate during cycling

This study investigated the variation in freely chosen pedal rate between subjects and its possible dependence on percentage myosin heavy chain I (%MHC I) in m. vastus lateralis, maximum leg strength and power, as well as efficiency. Additionally, the hypothesis was tested that a positive correlation exists between percentage MHC I and efficiency at pre-set pedal rates but not at freely chosen pedal rate. Twenty males performed cycling at low and high submaximal power output ( approximately 40 and 70% of the power output at which maximum oxygen uptake (VO(2max)) was attained at 80 r.p.m.) with freely chosen and pre-set pedal rates (61, 88, and 115 r.p.m.). Percentage MHC I as well as leg strength and power were determined. Freely chosen pedal rate varied considerably between subjects: 56-88 r.p.m. at low and 61-102 r.p.m. at high submaximal power output. This variation was only partly explained by percentage MHC I (21-97%) as well as by leg strength and power. Interestingly, %MHC I correlated significantly with the pedal rate at which maximum peak crank power occurred (r = -0.81). As hypothesized, %MHC I and efficiency were unrelated at freely chosen pedal rate, which was in contrast to a significant correlation found at pre-set pedal rates (r = 0.61 and r = 0.57 at low and high power output, respectively).

CONCLUSIONS

Subjects with high percentage MHC I chose high pedal rates close to the pedal rates at which maximum peak crank power occurred, while subjects with low percentage MHC I tended to choose lower pedal rates, favouring high efficiency. Nevertheless, the considerable variation in freely chosen pedal rate between subjects was neither fully accounted for by percentage MHC I nor by leg strength and power. Previously recognized relationships between percentage Type I ( approximately %MHC I) and efficiency as well as between pedal rate and efficiency were confirmed for pre-set pedal rates, but for freely chosen pedal rate, these variables were unrelated.

Training techniques to improve endurance exercise performances

In previously untrained individuals, endurance training improves peak oxygen uptake (VO2peak), increases capillary density of working muscle, raises blood volume and decreases heart rate during exercise at the same absolute intensity. In contrast, sprint training has a greater effect on muscle glyco(geno)lytic capacity than on muscle mitochondrial content. Sprint training invariably raises the activity of one or more of the muscle glyco(geno)lytic or related enzymes and enhances sarcolemmal lactate transport capacity. Some groups have also reported that sprint training transforms muscle fibre types, but these data are conflicting and not supported by any consistent alteration in sarcoplasmic reticulum Ca2+ ATPase activity or muscle physicochemical H+ buffering capacity. While the adaptations to training have been studied extensively in previously sedentary individuals, far less is known about the responses to high-intensity interval training (HIT) in already highly trained athletes. Only one group has systematically studied the reported benefits of HIT before competition. They found that >or=6 HIT sessions, was sufficient to maximally increase peak work rate (W(peak)) values and simulated 40 km time-trial (TT(40)) speeds of competitive cyclists by 4 to 5% and 3.0 to 3.5%, respectively. Maximum 3.0 to 3.5% improvements in TT(40) cycle rides at 75 to 80% of W(peak) after HIT consisting of 4- to 5-minute rides at 80 to 85% of W(peak) supported the idea that athletes should train for competition at exercise intensities specific to their event. The optimum reduction or 'taper' in intense training to recover from exhaustive exercise before a competition is poorly understood. Most studies have shown that 20 to 80% single-step reductions in training volume over 1 to 4 weeks have little effect on exercise performance, and that it is more important to maintain training intensity than training volume. Progressive 30 to 75% reductions in pool training volume over 2 to 4 weeks have been shown to improve swimming performances by 2 to 3%. Equally rapid exponential tapers improved 5 km running times by up to 6%. We found that a 50% single-step reduction in HIT at 70% of W(peak) produced peak approximately 6% improvements in simulated 100 km time-trial performances after 2 weeks. It is possible that the optimum taper depends on the intensity of the athletes' preceding training and their need to recover from exhaustive exercise to compete. How the optimum duration of a taper is influenced by preceding training intensity and percentage reduction in training volume warrants investigation.

Effects of external loading on power output in a squat jump on a force platform: a comparison between strength and power athletes and sedentary individuals

The aim of this study was to determine the effects of external loading on power output during a squat jump on a force platform in athletes specializing in strength and power events (6 elite weight-lifters and 16 volleyball players) and in 20 sedentary individuals. Instantaneous power was computed from time-force curves during vertical jumps with and without an external load (0, 5 or 10 kg worn in a special vest). The jumps were performed from a squat position, without lower limb counter-movement or an arm swing. Peak instantaneous power corresponded to the highest value of instantaneous power during jumping. Average power throughout the push phase of the jump was also calculated. A two-way analysis of variance showed significant interactions between the load and group effects for peak instantaneous power (P< 0.01) and average power (P< 0.001). Peak instantaneous power decreased significantly in sedentary individuals when moderate external loads were added. The peak instantaneous power at 0 kg was greater than that at 5 and 10 kg in the sedentary individuals. In contrast, peak instantaneous power was independent of load in the strength and power athletes. Mean power at 0 kg was significantly lower than at 5 kg in the athletes; at 0 kg it was significantly higher than at 10 kg in the sedentary males and at 5 and 10 kg in the sedentary females. In all groups, the force corresponding to peak instantaneous power increased and the velocity corresponding to peak instantaneous power decreased with external loading. The present results suggest that the effects of external loading on peak instantaneous power are not significant in strength and power athletes provided that the loads do not prevent peak velocity from being higher than the velocity that is optimal for maximal power output.

Quadriceps muscle function in relation to habitual physical activity and VO2max in men and women aged more than 65 years

The relationship of quadriceps maximal muscle power (Pmax), corresponding optimal shortening velocity (v(opt)), and relative fatigability (Pmax%D) to maximal oxygen uptake (VO2max) and habitual physical activity (PA) was examined in healthy community-dwelling subjects (29 women and 25 men) aged more than 65 years old. PA was evaluated by a questionnaire and expressed using two activity indices: mean habitual daily energy expenditure (MHDEE) and the daily energy expenditure corresponding to leisure time sports activities (Sports Activity). In women, Pmax correlated positively with VO2max (r = .56) and with Sports Activity (rho = .41). Both Sports Activity and Pmax were significant independent predictors of VO2max and accounted for 62% of variance in VO2max. In men, v(opt) was significantly negatively related to MHDEE (r = -.59) and to Sports Activity (rho = -.40). Neither in women nor in men was Pmax%D correlated with VO2max or PA indices. The different relationship of Pmax and v(opt) with VO2max and PA indices suggests that habitual PA may be sufficient in active older women, but not in men, to positively influence quadriceps muscle function. These gender differences may suggest different approaches in exercise programming for elderly women and men.

Maximal power across the lifespan

BACKGROUND

Previous investigators have reported that maximal power increases during growth and decreases with aging. These age-related differences have been reported to persist even when power is scaled to body mass or muscle size. We hypothesized that age-related differences in maximal power were primarily related to differences in muscle size and fiber-type distribution rather than to age per se.

METHODS

Maximum cycling power (Pmax) and optimal pedaling rate (Vopt, a surrogate measure for muscle fiber type) were determined for 195 boys and men, 8-70 years of age, by using inertial load cycle ergometry. Anthropometric dimensions were used to estimate lean thigh volume (LTVest) of all subjects, and magnetic resonance imagery was used to determine thigh and hip muscle volume (MRIvol) for 24 subjects.

RESULTS

Pmax was highly related to the product of LTVest and Vopt (LTVest X Vopt; r2 = .83). Multiple regression revealed that Pmax was significantly related to both LTVest x Vopt and age (R2 = .84). Power scaled by LTVest X Vopt was stable during growth and exhibited a small but significant decrease with aging. MRIvol was highly correlated with LTVest, and the ratio of LTVest to MRIvol was independent of age.

CONCLUSIONS

These results suggest that muscle volume and optimal pedaling rate are the main determinants of maximal power across the lifespan and that the contractile properties of muscle are developed early in childhood and remain nearly intact late into the lifespan.

Influence of fatigue on EMG/force ratio and cocontraction in cycling

PURPOSE

The purpose of the present study was to observe force and power losses and electromyographic manifestations of fatigue during repeated sprints performed on a friction-loaded cycle ergometer.

METHODS

Ten subjects performed 15 maximal 5-s sprints with 25-s rests between them. Power, velocity, and torque were measured during sprints 1 and 13 and during two submaximal constant-velocity (50 rpm) periods of cycling performed before and after the sprints. The EMG signals of five leg muscles were stored to determine the EMG/force ratio of power producer muscles and the coactivation of antagonist muscles. The power producer muscles were activated to the same level during sprints 1 and 13, despite a loss of force, whereas the vastus lateralis muscle was recruited more during the submaximal cycling period under fatigue conditions.

RESULTS

This led to an increased EMG/force ratio for the power producer muscles, indicating the peripheral fatigue status of these muscles. Antagonist muscles were less activated during the sprints after fatigue; whereas they stayed unchanged during the last submaximal cycling period.

CONCLUSIONS

This suggests that there is a decrease in coactivation as agonist force is lost. This decrease in coactivation under fatigue conditions has not been previously reported and is probably due to the training status of the subjects. Subjects may have learned to better use their antagonist muscles to efficiently transfer force and power to the rotating pedal. This coordination can be adapted to cope with fatigue of the power producer muscles.

Adaptation of muscle coordination to altered task mechanics during steady-state cycling

The objective of this work was to increase our understanding of how motor patterns are produced during movement tasks by quantifying adaptations in muscle coordination in response to altered task mechanics. We used pedaling as our movement paradigm because it is a constrained cyclical movement that allows for a controlled investigation of test conditions such as movement speed and effort. Altered task mechanics were introduced using an elliptical chainring. The kinematics of the crank were changed from a relatively constant angular velocity using a circular chainring to a widely varying angular velocity using an elliptical chainring. Kinetic, kinematic and muscle activity data were collected from eight competitive cyclists using three different chainrings--one circular and two different orientations of an elliptical chainring. We tested the hypotheses that muscle coordination patterns (EMG timing and magnitude), specifically the regions of active muscle force production, would shift towards regions in the crank cycle in which the crank angular velocity, and hence muscle contraction speeds, were favorable to produce muscle power as defined by the skeletal muscle power-velocity relationship. The results showed that our hypothesis with regards to timing was not supported. Although there were statistically significant shifts in muscle timing, the shifts were minor in absolute terms and appeared to be the result of the muscles accounting for the activation dynamics associated with muscle force development (i.e. the delay in muscle force rise and decay). But, significant changes in the magnitude of muscle EMG during regions of slow crank angular velocity for the tibialis anterior and rectus femoris were observed. Thus, the nervous system used adaptations to the muscle EMG magnitude, rather than the timing, to adapt to the altered task mechanics. The results also suggested that cyclists might work on the descending limb of the power-velocity relationship when pedaling at 90 rpm and sub-maximal power output. This finding might have important implications for preferred pedaling rate selection.

Muscle function during brief maximal exercise: accurate measurements on a friction-loaded cycle ergometer

A friction loaded cycle ergometer was instrumented with a strain gauge and an incremental encoder to obtain accurate measurement of human mechanical work output during the acceleration phase of a cycling sprint. This device was used to characterise muscle function in a group of 15 well-trained male subjects, asked to perform six short maximal sprints on the cycle against a constant friction load. Friction loads were successively set at 0.25, 0.35, 0.45, 0.55, 0.65 and 0.75 N.kg-1 body mass. Since the sprints were performed from a standing start, and since the acceleration was not restricted, the greatest attention was paid to the measurement of the acceleration balancing load due to flywheel inertia. Instantaneous pedalling velocity (v) and power output (P) were calculated each 5 ms and then averaged over each downstroke period so that each pedal downstroke provided a combination of v, force and P. Since an 8-s acceleration phase was composed of about 21 to 34 pedal downstrokes, this many v-P combinations were obtained amounting to 137-180 v-P combinations for all six friction loads in one individual, over the widest functional range of pedalling velocities (17-214 rpm). Thus, the individual's muscle function was characterised by the v-P relationships obtained during the six acceleration phases of the six sprints. An important finding of the present study was a strong linear relationship between individual optimal velocity (vopt) and individual maximal power output (Pmax) (n = 15, r = 0.95, P < 0.001) which has never been observed before. Since vopt has been demonstrated to be related to human fibre type composition both vopt, Pmax and their inter-relationship could represent a major feature in characterising muscle function in maximal unrestricted exercise. It is suggested that the present method is well suited to such analyses.