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1.
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. 相似文献
2.
L R McNaughton 《Journal of sports sciences》1992,10(5):415-423
Nine healthy male subjects who were all participating in athletic events volunteered to take part in this study, the aim of which was to determine whether there are specific dosages of sodium bicarbonate (HCO3-) that are useful as an ergogenic aid as far as anaerobic performance times are concerned. A control, placebo (CaCO3 500 mg kg-1) and five dosages of bicarbonate (100, 200, 300, 400 and 500 mg kg-1) were used. The anaerobic test consisted of pedalling a Repco Exertech cycle ergometer for 1 min during which total work (kJ) and peak power (W) were measured. The subjects completed more work in the 200 (P < 0.05), 300, 400 and 500 mg kg-1 (P < 0.005) trials with most work being undertaken in the 300 mg kg-1 trial (41.9 kJ min-1). Peak power was not significantly different from the control until the 300 mg kg-1 dose, and there were no further changes from this with increasing doses of HCO3-. The highest level of peak power achieved was 1295 +/- 72.8 W at the 300 mg kg-1 dosage. Blood pH indicated that after ingestion of all but the 100 mg kg-1 dose, a state of alkalosis was achieved (P < 0.005), and this was also indicated by changes in base excess. Bicarbonate levels increased post-ingestion in all but the 100 mg kg-1 dose, with these changes reflecting the changes that occurred in the work output. Blood lactate (BLa) levels increased post-exercise (P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
3.
A 30-s 'all-out' power protocol was studied in four groups of racing cyclists including internationals (n = 8), Category 1 (n = 10), Category 2 (n = 15) and Category 3 (n = 11). Following warm-up each subject completed five trials interspersed by 3 min of low intensity exercise on an ergowheel racing cycle ergometry system at a power output of 15 W kg-1 body weight, generated at 130 rev min-1. Temporal indices of performance included delay time (DT) to achieve the power criterion, total time (TT) of the maintenance of the power criterion and the ratio of TT/DT. 'Explosive' leg strength was assessed from a vertical jump. The results indicated that international and Category 1 cyclists had lower DT (2.2 +/- 0.1 s and 2.1 +/- 0.0 s, respectively; P less than 0.05), higher TT (28.1 +/- 0.7 s and 27.0 +/- 0.7 s, respectively; P less than 0.05) and elevated TT/DT (12.8 and 12.9, respectively; P less than 0.01). 'Explosive' leg strength was also higher (P less than 0.05) in the internationals than in the other groups of cyclists. The protocol provides a sport-related method for the assessment of short term endurance performance ability in racing cyclists which may be of value in identifying the anaerobic capability of individual cyclists. 相似文献
4.
There is little published data in relation to the effects of caffeine upon cycling performance, speed and power in trained cyclists, especially during cycling of approximately 60 s duration. To address this, eight trained cyclists performed a 1 km time-trial on an electronically braked cycle ergometer under three conditions: after ingestion of 5 mg x kg-1 caffeine, after ingestion of a placebo, or a control condition. The three time-trials were performed in a randomized order and performance time, mean speed, mean power and peak power were determined. Caffeine ingestion resulted in improved performance time (caffeine vs. placebo vs. control: 71.1 +/- 2.0 vs. 73.4 +/- 2.3 vs. 73.3 +/- 2.7 s; P = 0.02; mean +/- s). This change represented a 3.1% (95% confidence interval: 0.7-5.6) improvement compared with the placebo condition. Mean speed was also higher in the caffeine than placebo and control conditions (caffeine vs. placebo vs. control: 50.7 +/- 1.4 vs. 49.1 +/- 1.5 vs. 49.2 +/- 1.7 km x h-1; P = 0.0005). Mean power increased after caffeine ingestion (caffeine vs. placebo vs. control: 523 +/- 43 vs. 505 +/- 46 vs. 504 +/- 38 W; P = 0.007). Peak power also increased from 864 +/- 107 W (placebo) and 830 +/- 87 W (control) to 940 +/- 83 W after caffeine ingestion (P = 0.027). These results provide support for previous research that found improved performance after caffeine ingestion during short-duration high-intensity exercise. The magnitude of the improvements observed in our study could be due to our use of sport-specific ergometry, a tablet form and trained participants. 相似文献
5.
The aim of this study was to examine joint power generation during a concentric knee extension isokinetic test and a squat vertical jump. The isokinetic test joint power was calculated using four different methods. Five participants performed concentric knee extensions at 0.52, 1.57, 3.14 and 5.23 rad x s(-1) on a Lido isokinetic dynamometer. The squat vertical jump was performed on a Kistler force plate. Kinematic data from both tests were collected and analysed using an ELITE optoelectronic system. An inverse dynamics model was applied to measure knee joint moment in the vertical jump. Knee angular position data from the kinematic analysis in the isokinetic test were used to derive the actual knee angular velocity and acceleration, which, in turn, was used to correct the dynamometer moment for inertial effects. Power was measured as the product of angular velocity and moment at the knee joint in both tests. Significant differences (P < 0.05) were found between mean (+/- s) peak knee joint power in the two tests (squat vertical jump: 2255 +/- 434 W; isokinetic knee extension: 771 +/- 81 W). Correlation analysis revealed that there is no relationship between the peak knee joint power during the vertical jump and the slow velocity isokinetic tests. Higher isokinetic velocity tests show better relationships with the vertical jump but only if the correct method for joint power calculation is used in the isokinetic test. These findings suggest that there are important differences in muscle activation and knee joint power development that must be taken into consideration when isokinetic tests are used to predict jumping performance. 相似文献
6.
Effect of loading on peak power of the bar, body, and system during power cleans, squats, and jump squats 总被引：3，自引：3，他引：0
Nine males (age 24.7 ± 2.1 years, height 175.3 ± 5.5 cm, body mass 80.8 ± 7.2 kg, power clean 1-RM 97.1 ± 6.36 kg, squat 1-RM = 138.3 ± 20.9 kg) participated in this study. On day 1, the participants performed a one-repetition maximum (1-RM) in the power clean and the squat. On days 2, 3, and 4, participants performed the power clean, squat or jump squat. Loading for the power clean ranged from 30% to 90% of the participant's power clean 1-RM and loading for the squat and jump squat ranged from 0% to 90% of the participant's squat 1-RM, all at 10% increments. Peak force, velocity, and power were calculated for the bar, body, and system (bar + body) for all power clean, squat, and jump squat trials. Results indicate that peak power for the bar, body, and system is differentially affected by load and movement pattern. When using the power clean, squat or jump squat for training, the optimal load in each exercise may vary. Throwing athletes or weightlifters may be most concerned with bar power, but jumpers or sprinters may be more concerned with body or system power. Thus, the exercise type and load vary according to the desired stimulus. 相似文献
7.
The purpose of this study was to compare the maximal exercise performance during cycle ergometry of 34 men and 47 women. External peak power output (OPP) and optimized pedalling rate (ORPM) were calculated from data gathered during an optimization procedure performed on a friction braked cycle ergometer. In addition, lean leg volume (LLV) and lean upper leg volume (LULV) were determined using an anthropometric technique. Both OPP and ORPM were greater in men than in women (1007 +/- 135 vs 673 +/- 109 W and 119.5 +/- 7.0 vs 104.5 +/- 8.4 rev min-1, respectively; P less than 0.001). The LLV and LULV were also greater in men than in women (7.41 +/- 0.82 vs 5.19 +/- 0.85 l and 4.96 +/- 0.63 vs 3.35 +/- 0.62 l, respectively; P less than 0.001). The ratio standards OPP/LLV and OPP/LULV did not differ significantly between men and women (136.3 +/- 14.7 vs 131.0 +/- 20.6 W l-1 and 204.4 +/- 27.1 vs 204.4 +/- 37.0 W l-1, respectively; P greater than 0.05). Peak power output was related to each of the anthropometric indices in both men and women (LLV:r = 0.614 and 0.527, P less than 0.001; LULV:r = 0.489 and 0.396, P less than 0.01). Analysis of covariance revealed no significant differences between the groups in the variance about regression and the regression coefficients (P greater than 0.05), but the elevation of the regression lines did differ (P less than 0.001). The results suggest that there are differences between maximal exercise performance in men and women that are independent of estimated lean leg volume. They also demonstrate that, in this case, consideration of ratio standards is misleading and that a comparison of regression standards is more appropriate. 相似文献
8.
Jeffrey M. McBride Tracie L. Haines Tyler J. Kirby 《Journal of sports sciences》2013,31(11):1215-1221
Abstract Nine males (age 24.7 ± 2.1 years, height 175.3 ± 5.5 cm, body mass 80.8 ± 7.2 kg, power clean 1-RM 97.1 ± 6.36 kg, squat 1-RM = 138.3 ± 20.9 kg) participated in this study. On day 1, the participants performed a one-repetition maximum (1-RM) in the power clean and the squat. On days 2, 3, and 4, participants performed the power clean, squat or jump squat. Loading for the power clean ranged from 30% to 90% of the participant's power clean 1-RM and loading for the squat and jump squat ranged from 0% to 90% of the participant's squat 1-RM, all at 10% increments. Peak force, velocity, and power were calculated for the bar, body, and system (bar + body) for all power clean, squat, and jump squat trials. Results indicate that peak power for the bar, body, and system is differentially affected by load and movement pattern. When using the power clean, squat or jump squat for training, the optimal load in each exercise may vary. Throwing athletes or weightlifters may be most concerned with bar power, but jumpers or sprinters may be more concerned with body or system power. Thus, the exercise type and load vary according to the desired stimulus. 相似文献
9.
In this study, we assessed the ventilatory response in 84 children (46 males: age 8.1 +/- 1.0 years, body mass 34.2 +/- 7.9 kg, height 1.32 +/- 0.16 m; 38 females: age 8.0 +/- 0.8 years, body mass 31.7 +/- 8.7 kg, height 1.31 +/- 0.08 m) during a cycle ergometer test to determine if there was an influence of gender on ventilatory efficiency. The test commenced at 25 W and increased by 10 W every minute. Expired air was collected through a face mask and analysed breath by breath. The ventilatory anaerobic threshold was determined according to gas exchange methods and we focused our attention on the analysis of carbon dioxide production (VCO(2)), ventilation (V(E)), the ratio V(E)/VCO(2) and its slope. Differences between the sexes at maximal power output were strongly significant for V(E) and VCO(2) (P = 0.0001 and P = 0.0004 respectively) and moderately significant for the V(E)/VCO(2) ratio (P = 0.05). The slope of V(E) versus VCO(2) was 30.8 +/- 4.2 for males and 29.4 +/- 3.2 for females, with no difference between the sexes (P = 0.1). In conclusion, although the peak values of V(E) and VCO(2) were significantly different between the sexes, there were no such differences in ventilatory efficiency during a maximal incremental test expressed as the slope of V(E)/VCO(2), at least in young children. 相似文献
10.
Complex training, a combination of resistance training and plyometrics is growing in popularity, despite limited support for its efficacy. In pre- and early pubertal children, the study of complex training has been limited, and to our knowledge an examination of its effect on anaerobic performance characteristics of the upper and lower body has not been undertaken. Furthermore, the effect of detraining after complex training requires clarification. The physical characteristics (mean+/-s) of the 54 male participants in the present study were as follows: age 12.3 +/- 0.3 years, height 1.57 +/- 0.07 m, body mass 50.3 +/- 11.0 kg. Participants were randomly assigned to an experimental (n = 33) or control group (n = 21). The training, which was performed three times a week for 12 weeks, included a combination of dynamic constant external resistance and plyometrics. After training, participants completed 12 weeks of detraining. At baseline, after training and after detraining, peak and mean anaerobic power, dynamic strength and athletic performance were assessed. Twenty-six participants completed the training and none reported any training-related injury. Complex training was associated with small increases (< or =5.5%) in peak and mean power during training, followed by decreases of a similar magnitude (< or = -5.9%) during detraining (P < 0.05). No changes or minor, progressive increases (< or =1.5%) were evident in the control group (P > 0.05). In the experimental group, dynamic strength was increased by 24.3 - 71.4% (dependent on muscle group; P < 0.01), whereas growth-related changes in the control group varied from 0 to 4.4% (P > 0.05). For 40-m sprint running, basketball chest pass and vertical jump test performance, the experimental group saw a small improvement (< or =4.0%) after training followed by a decline (< or = -4.4%) towards baseline during detraining (P < 0.05), whereas the control group experienced no change (P > 0.05). In conclusion, in pre- and early pubertal boys, upper and lower body complex training is a time-effective and safe training modality that confers small improvements in anaerobic power and jumping, throwing and sprinting performance, and marked improvements in dynamic strength. However, after detraining, the benefits of complex training are lost at similar rates to other training modalities. 相似文献
11.
为了解体育专业学生和普通学生无氧能力的差异,不同无氧测试方法的特点和互相关系,采用MONARK894E无氧功率自行车和HUR测力台对27名体育专业男大学生和10名普通学生无氧功能进行测试,测试学生纵跳、10s和30s的无氧能力,收集最大功率、平均功率等指标。体育专业学生不同无氧测试输出功率均高于普通学生,不同专业体育生无氧能力指标无显著差异,无氧功率自行车和HUR测力台测试的最大输出功具有显著正相关。体育专业学生无氧能力强于普通学生,不同专项体育大学生无氧能力无显著差别,测力台测试结果可以预测大学生较长时间的无氧能力。 相似文献
12.
The aims of this study were to compare the physiological and anthropometric characteristics of successful mountain bikers and professional road cyclists and to re-examine the power-to-weight characteristics of internationally competitive mountain bikers. Internationally competitive cyclists (seven mountain bikers and seven road cyclists) completed the following tests: anthropometric measurements, an incremental cycle ergometer test and a 30 min laboratory time-trial. The mountain bikers were lighter (65.3+/-6.5 vs 74.7+/-3.8 kg, P= 0.01; mean +/- s) and leaner than the road cyclists (sum of seven skinfolds: 33.9+/-5.7 vs 44.5+/-10.8 mm, P = 0.04). The mountain bikers produced higher power outputs relative to body mass at maximal exercise (6.3+/-0.5 vs 5.8+/-0.3 W x kg(-1), P= 0.03), at the lactate threshold (5.2+/-0.6 vs 4.7+/-0.3 W x kg(-1), P= 0.048) and during the 30 min time-trial (5.5+/-0.5 vs 4.9+/-0.3 W x kg(-1), P = 0.02). Similarly, peak oxygen uptake relative tobody mass was higher in the mountain bikers (78.3+/-4.4 vs 73.0+/-3.4 ml x kg(-1) x min(-1), P = 0.03). The results indicate that high power-to-weight characteristics are important for success in mountain biking. The mountain bikers possessed similar anthropometric and physiological characteristics to previously studied road cycling uphill specialists. 相似文献
13.
《European Journal of Sport Science》2013,13(9):1184-1194
AbstractThis study aimed to analyse whether increasing the eccentric overload (EO) during resistance training, in terms of range of motion and/or velocity using an electric-motor device, would induce different muscle adaptations than conventional flywheel-EO resistance training. Forty physically active university students (21.7?±?3.4 years) were randomly placed into one of the three training groups (EX1, EX2, FW) and a control group without training (n?=?10 per group). Participants in the training groups completed 12 sessions (4 sets of 7 repetitions) of iso-inertial single-leg squat training over 6 weeks for the dominant leg. Resistance was generated either by an electric-motor device at two different velocities for the eccentric phase; 100% (EX1) or 150% (EX2) of concentric speed, or by a conventional flywheel device (FW). Thigh lean tissue mass, unilateral leg press one-repetition maximum (1-RM), unilateral muscle power at different percentages of the 1-RM and bilateral/unilateral vertical jump were assessed before and after the 6-week training. There were significant (p?<?0.05–0.001) main effects of time in the 3 training groups, indicating increased thigh lean tissue mass (2.5–5.8%), 1-RM load (22.4–30.2%), vertical jump performance (9.1–32.9%) and muscle power (8.8–21.7%), without differences across experimental groups. Participants in the control group did not improve any of the variables measured. In addition, EX2 showed greater gains in eccentric average peak power during training than EX1 and FW (p?<?0.001). Despite the different EO offered, 6 weeks of resistance training using flywheel or electric-motor devices induced similar significant gains in muscle mass, strength, muscle power and vertical jump. 相似文献
14.
Allan Power Brent E. Faught Eryk Przysucha Moira McPherson 《Measurement in physical education and exercise science》2013,17(1):69-80
In this study the authors examine the test–retest reliability and concurrent validity of the Repeat Ice Skating Test (RIST). This was an on-ice field anaerobic test that measured average peak power and was validated with 3 anaerobic lab tests: (a) vertical jump, (b) the Margaria–Kalamen stair test, and (c) the Wingate Anaerobic Test. The participants (n?=?14) were 11- to 12-year-old males selected from a Peewee “A” level ice hockey team (Thunder Bay, Canada). The results of the test–retest reliability estimation showed that the RIST was a reliable test at measuring average peak power in watts (R = .99, C.I.95% = 0.97 to 0.99) and watts per kilogram (R = .98, C.I.95% = 0.94 to 0.99). The RIST was also a valid test when correlated with the 3 anaerobic lab tests for measuring peak power in watts: vertical jump (r = .86, C.I.95% = 0.72 to 0.94), Margaria–Kalamen stair test (r = .66, C.I.95% = 0.39 to 0.83) and Wingate Anaerobic Test (r = .86, C.I.95% = 0.72 to 0.93). The test is considered promising because it does not require any specific equipment, and is a sport-specific, on-ice test, that can be administered during a regular ice hockey practice session. 相似文献
15.
Tarak Driss Tarak Driss Henry Vandewalle Jacques Quièvre Christian Miller Hugues Monod 《Journal of sports sciences》2013,31(2):99-105
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. 相似文献
16.
Hertogh C Chamari K Damiani M Martin R Hachana Y Blonc S Hue O 《Journal of sports sciences》2005,23(9):937-942
In this study, we examined the effects of a prior run-up on intermittent maximal vertical jump performance. Seven regionally ranked male volleyball players volunteered to participate in the study. They performed three randomized tests: (1) six repeated intermittent maximal jumps (jump condition), (2) six repeated intermittent run-ups (run-up condition), and (3) six repeated run-ups followed by maximal jumps (run-up plus jump condition). All performances were assessed and blood lactate concentration and heart rate were measured before and after each of the tests. Mean ( +/- ) jump performance (64.7 +/- 2.3 cm) increased significantly (P = 0.02) over the course of the jump condition and was significantly higher (P < 0.001) than for the run-up plus jump condition (58.0 +/- 3.2 cm), which tended to decrease with repetition. Blood lactate concentration was significantly higher in the run-up plus jump condition (3.73 +/- 0.24 mmol . l(-1)) than in the jump (2.61 +/- 0.26 mmol . l(-1), P = 0.02) and run-up (2.86 +/- 0.18 mmol . l(-1), P = 0.03) conditions. The increase in heart rate was significantly higher both in the run-up plus jump condition (33 +/- 6 beats . min(-1), P = 0.05) and run-up condition (33 +/- 4 beats . min(-1), P = 0.02) than in the jump condition (21 +/- 3 beats . min(-1)). The results indicate that the addition of run-ups probably impeded performance in the repetition of vertical jumps. 相似文献
17.
Frost DM Cronin JB Newton RU 《Sports biomechanics / International Society of Biomechanics in Sports》2008,7(3):372-385
Explosive upper-body movements, with which the load is not thrown (non-ballistic), may comprise a phase during which forces are produced in opposition to the motion of the load. Thirty men completed three test sessions (free weight, ballistic, and pneumatic), each consisting of a one-repetition maximum (1-RM) and four explosive repetitions of a bench press at six loads (15, 30, 45, 60, 75, and 90% 1-RM). The end of the lifting phase for the non-ballistic conditions (free weight and pneumatic) was defined by: the point of peak barbell displacement and the point at which the vertical force became negative (positive work). When analysed by peak displacement, the ballistic condition elicited significantly greater mean velocity, force, and power at loads of 15-60% 1-RM compared with the free weight condition. When the period of negative work was removed, the mean free weight velocity, force, and power at loads below 60% 1-RM increased. Consequently, the only differences between the free weight and ballistic conditions were found at loads of 15% and 30% 1-RM. Including a period of negative work may underestimate all kinematic and kinetic variables dependent on the time to, or position of, the end of the lifting phase, for non-ballistic efforts. 相似文献
18.
ABSTRACT We aimed to determine key biomechanical parameters explaining age-related jumping performance differences in youth elite female soccer players. Multiple biomechanical parameters from countermovement (CMJ) squat (SJ) and drop (DJ) jump testing of elite female soccer players (n = 60) within the same national training centre were analysed across ages 9-11y, 12-14y and 15-19y. Effects of age group and jump type on jump height were found, with the older jumping higher than the younger groups in all jumps (P < 0.05). For DJ, higher reactive strength index was found for older, compared to each younger group (P < 0.001). For CMJ and SJ, peak power was the most decisive characteristic, with significant differences between each group for absolute peak power (P < 0.0001) and body-weight-normalised peak power in CMJ (57 ± 7W/kg, 50 ± 7W/kg, 44.7 ± 5.5W/kg; P < 0.05) and between the older and each younger group in SJ (56.7 ± 7.1W/kg, 48.9 ± 7.1W/kg, 44.6 ± 6W/kg; P < 0.01). Age-related differences in jumping performance in youth elite female soccer players appear to be due to power production during standing jumps and by the ability to jump with shorter ground contact times during reactive jumps. 相似文献
19.
The purpose of this study was to assess the power output of field-based downhill mountain biking. Seventeen trained male downhill cyclists (age 27.1 +/- 5.1 years) competing nationally performed two timed runs of a measured downhill course. An SRM powermeter was used to simultaneously record power, cadence, and speed. Values were sampled at 1-s intervals. Heart rates were recorded at 5-s intervals using a Polar S710 heart rate monitor. Peak and mean power output were 834 +/- 129 W and 75 +/- 26 W respectively. Mean power accounted for only 9% of peak values. Paradoxically, mean heart rate was 168 +/- 9 beats x min(-1) (89% of age-predicted maximum heart rate). Mean cadence (27 +/- 5 rev x min(-1)) was significantly related to speed (r = 0.51; P < 0.01). Analysis revealed an average of 38 pedal actions per run, with average pedalling periods of 5 s. Power and cadence were not significantly related to run time or any other variable. Our results support the intermittent nature of downhill mountain biking. The poor relationships between power and run time and between cadence and run time suggest they are not essential pre-requisites to downhill mountain biking performance and indicate the importance of riding dynamics to overall performance. 相似文献
20.
Anna Iossifidou Vasilios Baltzopoulos Giannis Giakas 《Journal of sports sciences》2013,31(10):1121-1127
The aim of this study was to examine joint power generation during a concentric knee extension isokinetic test and a squat vertical jump. The isokinetic test joint power was calculated using four different methods. Five participants performed concentric knee extensions at 0.52, 1.57, 3.14 and 5.23 rad?·?s?1 on a Lido isokinetic dynamometer. The squat vertical jump was performed on a Kistler force plate. Kinematic data from both tests were collected and analysed using an ELITE optoelectronic system. An inverse dynamics model was applied to measure knee joint moment in the vertical jump. Knee angular position data from the kinematic analysis in the isokinetic test were used to derive the actual knee angular velocity and acceleration, which, in turn, was used to correct the dynamometer moment for inertial effects. Power was measured as the product of angular velocity and moment at the knee joint in both tests. Significant differences (P <?0.05) were found between mean (?± s) peak knee joint power in the two tests (squat vertical jump: 2255?±?434W; isokinetic knee extension: 771?±?81W). Correlation analysis revealed that there is no relationship between the peak knee joint power during the vertical jump and the slow velocity isokinetic tests. Higher isokinetic velocity tests show better relationships with the vertical jump but only if the correct method for joint power calculation is used in the isokinetic test. These findings suggest that there are important differences in muscle activation and knee joint power development that must be taken into consideration when isokinetic tests are used to predict jumping performance. 相似文献