Short-term Power Output Research Articles

Short term power output in relation to growth and maturation

Objective—To examine short term power output during growth and maturation using a multilevel modelling approach. Methods—Body mass, stature, and triceps and subscapular skinfold thicknesses of boys and girls, aged 12.2...

Changes in short-term power output in 10- to 12-year-olds

In this study, we used multi‐level regression modelling to assess the influence of age, sex, body size, skinfold thicknesses, maturity, thigh muscle volume and isokinetic leg strength on the development of load- and inertia‐adjusted peak (1 s) and mean power (30 s) determined using the Wingate anaerobic test. Fifteen males and 19 females were measured twice, first aged 10.0±45 0.3 years and then aged 11.8 ± 0.3 years. Initial models identified body mass and height as significant explanatory variables ( P < 0.05) for peak power and mean power, with an additional age effect for the former. No significant differences between the sexes or maturity effects were observed for either peak or mean power ( P > 0.05). The introduction of sum of skinfolds improved the fit of the model and rendered the height term non‐significant for both peak and mean power ( P > 0.05). An age effect became apparent for mean power. When isokinetic leg strength and thigh muscle volume were entered into the model, the latter exerted a significant effect on both peak and mean power ( P < 0.05), whereas isokinetic leg strength was not a significant explanatory variable for either ( P > 0.05). In conclusion, thigh muscle volume exerts a positive influence on young people's short‐term power output, which is additional to the effects of body mass, sum of skinfolds and age.

Longitudinal changes in young people's short-term power output.

The influences of age, body size, skin-fold thickness, gender, and maturation on the short-term power output of young people were examined using multilevel modelling. Subjects were 97 boys and 100 girls, aged 12.2 +/- 0.4 yr at the onset of the study. Sexual maturity was classified according to Tanner's indices of pubic hair. Peak power (PP) and mean power (MP) were determined on two occasions 1 yr apart using the Wingate Anaerobic Test (WAnT). The data were analyzed using multilevel regression modelling. Initial models identified body mass and stature as significant explanatory variables with an additional positive effect of age, which was smaller for girls' MP. A significant gender difference was apparent for both power indices with girls achieving lower values than boys. A significant incremental effect of later maturity (stages 4 and 5 for pubic hair development) was identified for MP only. Subsequent incorporation of sum of two skin-fold thicknesses into the model yielded significant negative parameter estimates for PP and MP and negated both the stature effects and the maturation influence upon MP. There are gender differences in the longitudinal growth of performance on the WanT. Regardless of gender differences, body mass and skin-fold thicknesses appear to be the best anthropometric predictors of WAnT determined PP and MP in young people.

A Nonmotorized Treadmill Test to Assess Children’s Short-Term Power Output

The purpose of this study was to develop a nonmotorized treadmill sprint test (ExNMT) to assess children’s short-term power output, to establish the test’s repeatability, and to compare the results to corresponding Wingate anaerobic test (WAnT) measurements. Nineteen children (aged 10.9±0.3 years) completed 2 ExNMTs and 2 WAnTs. Statistical analysis revealed coefficients of repeatability for the ExNMT that compared very favorably with the WAnT for both peak power (26.6 vs. 44.5 W) and mean power (15.3 vs. 42.1 W). The validity of the ExNMT as a test of anaerobic performance is reflected by significant correlations (p ≤.05) with the WAnT (peak power, r = 0.82; mean power, r = 0.88) and reinforced by the relatively high post-exercise blood lactate concentrations (7.1 ± 1.3 vs. 5.6 ± 1.5 mmol · L−1 for the ExNMT and WAnT, respectively). This study has developed a promising laboratory running test with which to examine young people’s short-term power output.

ANAEROBIC POWER OUTPUT : SEX-RELATED DEVELOPMENTAL CHANGES.

843 It is well established that the anaerobic function in children improves during maturation. However, gender difference during this period has still to be clarified. The purpose of this study was to examine the effects of age and body composition on short-term cycling power output in prepubescent, pubescent and postpubescent girls (n = 465) and boys (n = 443). Peak Power output (PP) was measured with the Force Velocity Test (inertia of the flywheel included). Percent body fat and lean leg volume (LLV) were determined by anthropometry. Results showed that absolute PP; PP to body mass or LLV increased significantly ( P < 0.001) with age in both girls and boys until 18 yrs. PP was similar in both sexes before 14 yrs, whereas after 14 yrs, boys had significantly higher PP (+35%, P < 0.001) than girls (see fig.). When PP was standardized for body mass(W·kg-1) or for LLV (W·1-1) the gender-related differences was reduced (+25%, P < 0.001; +15%, P < 0.001, respectively). These results suggest that other factors than body composition may explain the gender differences in PP during growth.Figure

Children's and adolescents' anaerobic performance during cycle ergometry.

Cycle ergometry studies originated in the early 1900s but it was not until the early 1970s that the first studies of children and anaerobic performance were established. Since that time, research into the anaerobic performance of children and adolescents has proliferated, mainly due to attempts by investigators to overcome methodological problems. Besides the increase in studies using the most popular anaerobic test, the friction-braked Wingate, other tests such as the force-velocity and isokinetic cycle ergometers are becoming more common. No matter how the data are standardised, there is unequivocal agreement that children's and adolescents' anaerobic power scores are lower than those of adults. Qualitative muscular differences are often cited for this disparity rather than differences in the quantity of muscle, but conclusive research is lacking in this area. Despite the ethical considerations involved in studies with children, cycle ergometry has aided researchers to assess external short term power output, mean power and fatigue.

The effects of salmeterol on power output in nonasthmatic athletes

Background: Salmeterol xinafoate is a new aerosol inhalant that is used in the treatment of asthma. It is currently banned by the International Olympic Committee because of the concern that it may lend an unfair competitive advantage to the user. Objective: The purpose of this study was to determine whether salmeterol improves short-term anaerobic performance in elite nonasthmatic track cyclists. Methods: Eleven elite track cyclists volunteered to perform a 30-second all-out cycle ergometer test 3 hours after receiving either 42 μg of salmeterol xinafoate or placebo applied in a double-blind crossover procedure. During the ergometer test, peak power output, total work, time to peak power, and percent fatigue (decline in power output) were measured. Pulmonary measurements were also taken before and at various time points after inhalation and the ergometer test. A methacholine challenge was administered to each subject before participation in the study to ensure that none of the subjects had any reactive airway diseases. Results: There were no significant differences ( p > 0.05) between the placebo and salmeterol trials for peak power output, total work performed during the 30-second test, percent fatigue, and time to peak power. No differences between trials were observed for the pulmonary function test variables at any of the time points. Blood lactate concentrations before and after administration of drug or placebo were also not significantly different between trials. Additionally, salmeterol did not affect the maximal heart rate achieved during the test as compared with the placebo. Conclusion: Short-term salmeterol use within the prescribed dosage was not shown to increase short-term power output in nonasthmatic cyclists. (J Allergy Clin Immunol 1997;99:443-9.)

Effect of anthropometric characteristics and socio-economic status on physical performances of pre-pubertal children living in Bolivia at low altitude

We have previously observed that 11-year-old children of low socio-economic status (LSES) showed a delayed physical growth of approximately 2 years and developed lower normalized short-term power output than children of high socio-economic status (HSES) of the same age. In contrast, maximal oxygen uptake (VO2max) per unit of fat free mass was no different in either group. The aim of this study was to evaluate the effect of anthropometric characteristics between HSES and LSES prepubertal children in aerobic and anaerobic performance. To compare children of the same body dimensions, 11-year-old boys (n = 30) and girls (n = 31) of LSES and 9-year-old boys (n = 21) and girls (n = 27) of HSES were studied. Anthropometric measurements, VO2max (direct test), maximal anaerobic power (Pmax, force-velocity test) and mean anaerobic power (P, Wingate test) were determined. In these children having the same body dimensions: mean VO2max were the same in LSES and HSES children [1.2 (SD 0.2) l.min-1]; Pmax and P were lower in LSES subjects [154.0 (SD 33.2) vs 174.6 (SD 38.4) W and 116.3 (SD 23.3) vs 128.2 (SD 28.0) W, respectively]; the linear relationships between VO2max and fat free mass were the same in LSES and HSES boys but, in the girls, the LSES group had lower values. For anaerobic performance, the relationships were significantly different: the slopes were the same but LSES values for the both sexes were lower. These results would suggest that factors other than differences in body dimensions alone were responsible for the lower performance of LSES girls and boys. Cultural factors and motor learning, structural and functional alterations of muscle induced by marginal malnutrition have been discussed.

Effects of acute inhalation of the bronchodilator, albuterol, on power output

This study was designed to examine the effects of acute inhalation of the bronchodilator, albuterol (Proventil, Schering Corp.), on high intensity power output. Fifteen healthy nonasthmatic subjects (eight male, seven female, 18-33 yr) performed four supramaximal 15-s rides on a bicycle ergometer. Rides were arranged in pairs with a 10-min rest interval. Each pair of rides was preceded by a 5-min warm-up. Sessions were separated by a minimum of 48 h. The study design was fully randomized and double blind. Ten minutes prior to each pair of rides subjects inhaled two metered doses (180 micrograms) of albuterol (A) or a placebo (P). Individual ANOVAs revealed a significant difference between the A and P treatment for peak power (A = 886.6 W, P = 858.3 W) and fatigue (A = 27.2%, P = 24.4%). Mean changes in FEF25-75% (A = 0.712, P = 0.040 l.s-1), FEV1.0 (A = 0.188, P = 0.007 l), and PEF (A = 0.573, P = -0.155 l.s-1) were also statistically significant; however, these changes did not correlate to the anaerobic performance changes. No significant differences were found between treatments for heart rate increases resulting from the power test (A = 56.73 bpm, P = 53.20 bpm). These results indicate an ergogenic effect of the bronchodilator on short-term power output independent of impact on respiratory smooth muscle, with no effect on cardiac response.

Effect of fatigue on maximal power output at different contraction velocities in humans

The effect of fatigue as a result of a standard submaximal dynamic exercise on maximal short-term power output generated at different contraction velocities was studied in humans. Six subjects performed 25-s maximal efforts on an isokinetic cycle ergometer at five different pedaling rates (60, 75, 90, 105, and 120 rpm). Measurements of maximal power output were made under control conditions [after 6 min of cycling at 30% maximal O2 uptake (VO2max)] and after fatiguing exercise that consisted of 6 min of cycling at 90% VO2max with a pedaling rate of 90 rpm. Compared with control values, maximal peak power measured after fatiguing exercise was significantly reduced by 23 +/- 19, 28 +/- 11, and 25 +/- 11% at pedaling rates of 90, 105, and 120 rpm, respectively. Reductions in maximum peak power of 11 +/- 8 and 14 +/- 8% at 60 and 75 rpm, respectively, were not significant. The rate of decline in peak power during the 25-s control measurement was least at 60 rpm (5.1 +/- 2.3 W/s) and greatest at 120 rpm (26.3 +/- 13.9 W/s). After fatiguing exercise, the rate of decline in peak power at pedaling rates of 105 and 120 rpm decreased significantly from 21.5 +/- 9.0 and 26.3 +/- 13.9 W/s to 10.0 +/- 7.3 and 13.3 +/- 6.9 W/s, respectively. These experiments indicate that fatigue induced by submaximal dynamic exercise results in a velocity-dependent effect on muscle power. It is suggested that the reduced maximal power at the higher velocities was due to a selective effect of fatigue on the faster fatigue-sensitive fibers of the active muscle mass.

A Comparison of Maximal Power Outputs between Elite Male and Female Weightlifters in Competition

Films taken at the first Women’s World Weightlifting Championship were analyzed to determine the average power output during the total pulling phase, and the second pull phase, for the heaviest successful snatch and clean lift of gold medalists in each of nine body-weight divisions. Comparisons were made with previously published data on power output by male lifters in World and Olympic competition. Average relative power output values were one and a half to two times greater for both men and women when only the second pull phase of each lift was analyzed. Results show that women can generate higher short-term power outputs than previously documented, but lower than for men in absolute values and relative to body mass. Male/female comparisons in other high power sport events and basic strength measures are discussed. The high power outputs suggest the value of including the types of lifts analyzed in training programs to improve short-term power output.

A constant-load ergometer for measuring peak power output and fatigue.

A constant-load cycle ergometer was constructed that allows maximal power output to be measured for each one-half pedal revolution during brief, high-intensity exercise. To determine frictional force, an electronic load cell was attached to the resistance strap and the ergometer frame. Dead weights were attached to the strap's free end. Flywheel velocity was recorded by means of a magnetic switch and two magnets placed on the pedal sprocket. Pedaling resulted in magnetically activated switch closures, which produced two electronic pulses per pedal revolution. Pulses and load cell output were recorded (512 Hz), digitized, and stored on disk via microcomputer. Power output was later computed for each pair of adjacent pulses, representing average power per one-half pedal revolution. Power curves generated for each subject were analyzed for peak power output (the highest one-half pedal revolution average), time to peak power, power fatigue rate and index, average power, and total work. Thirty-eight males performed two 15-s tests separated by 15 min (n = 16) or 48 h (n = 22). Peak power output ranged from 846.0 to 1,289.1 W. Intraclass correlation analysis revealed high test-retest reliability for all parameters recorded on the same or different days (R = 0.91-0.97). No significant differences (P greater than 0.05) were noted between parameter means of the first and second tests. These results indicate that the ergometer described provides a means for conveniently and reliably assessing short-term power output and fatigue.

Effect of prior exercise on maximal short-term power output in humans.

The effect of prior exercise (PE) on subsequent maximal short-term power output (STPO) was examined during cycling exercise on an isokinetic ergometer. In the first series of experiments the duration of PE at a power output equivalent to 98% maximum O2 uptake (VO2max) was varied between 0.5 and 6 min before measurement of maximal STPO. As PE duration increased subsequent STPO fell to approximately 70% of control values after 3-6 min. In series ii the effect of varying the intensity of PE of fixed 6-min duration was studied in five subjects. After PE less than 60% VO2max there was an increase of 12% in STPO, but after greater than 60% VO2max there was a progressive fall in STPO as PE intensity increased, indicating a reduction of approximately 35% at 100% VO2max compared with control values. In series iii we examined the effect on STPO of allowing a recovery period after a fixed intensity (mean = 87% VO2max) of 6 min PE before measurement of STPO. This indicated a rapid recovery of dynamic function with a half time of approximately 32 s, which is similar to the kinetics of PC resynthesis and taken with the other findings suggests the dominant role that PC exerts on the STPO under these conditions.

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.

Human muscle function following prolonged eccentric exercise.

4 subjects performed repeated eccentric contractions with leg extensors during prolonged downhill walking (-25% gradient) at 6.44 km.h-1 until collapse due to muscle weakness (range of exercise duration 29 to 40 min). During the exercise oxygen uptake rose progressively from approximately 45% of the previously determined VO2max at 10 min to approximately 65% at the end of the exercise. Following the exercise there was an immediate, significant, and sustained reduction in maximal voluntary isometric contraction, and short term (anaerobic) power output measured concentrically on an isokinetic ergometer. These reductions in muscle function persisted for 96 hours post exercise, and were reflected by significant reductions in the tension generated at low frequency (20 Hz) relative to higher frequency (50 Hz) percutaneous stimulation of the quadriceps. All four subjects showed an increase in plasma levels of creatine kinase post eccentric exercise. Performing concentric contractions by walking uphill for one hour at a significantly greater metabolic cost failed to induce comparable reductions in muscle function. These results provide evidence for the consequences of prolonged eccentric work upon dynamic function which complements earlier reports of structural, enzymatic, and static function changes.

Mechanical power output in children aged 11 and 14 years.

Short-term power output in jumping and cycling has been measured in 56 children aged 11 and 14 years. The results showed that the peak power output in cycling (Wb) and jumping (Wp) were closely associated (r = 0.91) but in absolute terms Wb was approximately 34% greater than Wb. There were no significant differences in Wb (or Wp) between the 11-year-old boys and girls, but the 14-year-old boys recorded approximately 25% higher power output values in cycling and jumping than girls of the same age and were approximately twice as powerful as their younger male counterparts. The velocity of movement in cycling (Vb) and jumping (VT) for a given age were identical and independent of sex in the younger children. Peak power output in cycling was reached when force and velocity were equivalent to 50% of their calculated maximal values. When Wb and Wp were related to an anthropometric estimate of leg muscle (plus bone) volume the difference in absolute power output between the children disappeared. The results suggest that the difference between Wp and Wb and the increase in absolute mechanical power output with age is mainly a function of size and the force which can be exerted at the optimal frequency of movement in children.

Effect of heating on the contractile properties of triceps surae and maximal power output during jumping in elderly men.

The electrically evoked contractile properties of the triceps surae and short-term (less than 2 s) maximal power output during vertical jumping have been examined before and after heating (by water immersion) in 5 elderly men aged 70 +/- 5 years. Leg immersion in water at 44 degrees C for 30 min produced a 3.4 degrees C rise in muscle temperature (Tm) and was associated with a significant (p less than 0.001) reduction in maximal time to peak tension and half relaxation time of the twitch, but was without affect on maximal twitch, tetanic (20 and 50 Hz) and voluntary tensions. However, at 10 Hz maximal tetanic tension was reduced (p less than 0.05) from 604 +/- 104 to 422 +/- 142 N. During vertical jumping from a force platform, peak power output (W) was significantly (p less than 0.05) increased from 1,155 +/- 212 to 1,381 +/- 307 W after heating. The rise in W was due to a small increase in both take-off velocity and the exerted force, and was reflected in a 3-cm increase in the height jumped from the force platform. It is concluded that the contractile characteristics of elderly triceps surae can be modified by heating and a rise in Tm does effect a change in the capacity of the muscle to generate power.

Maximal Short-term (Anaerobic) Power Output Following Submaximal Exercise

Maximal Short-term (Anaerobic) Power Output Following Submaximal Exercise

Optimal Velocity for Maximal Short-term (Anaerobic) Power Output in Cycling

Optimal Velocity for Maximal Short-term (Anaerobic) Power Output in Cycling