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1.
The purpose of the investigation was to study the relationship between thrust phase duration, ground reaction force, velocity increase after pole thrust and pole angles versus pole length during double poling in roller skiing. Seven male regional elite cross-country skiers volunteered as subjects for the study. The subjects performed a maximal double pole thrust on roller skis with each of the three different pole lengths: 'short', self-selected (normal) and 'long'. The short and long poles were 7.5 cm shorter and 7.5 cm longer than the self-selected pole length. The subjects made seven maximal pole thrusts with each pole length, which were randomly selected during 21 trials. For each trial the subjects accelerated from a 1.2 m high downhill slope attaining a speed of 3.92 m.s-1 before making a maximal double pole thrust on a force plate placed at the bottom of the slope. The vertical (F2), anterior-posterior (Fy) and mediolateral (Fx) reaction forces of the left pole were measured by the force plate. The positions of the pole were recorded in 3-D by an opto-electronic system. Thrust phase duration, impulse, mean force, velocity increase after pole thrust and pole angles were calculated from the recorded data. Double poling with long poles produced a significantly larger propulsive anterior-posterior reaction force impulse and velocity increase than normal (p < .05) and short poles (p < .05). This was in spite of a larger mean anterior-posterior reaction force being produced with short poles. Thus, thrust phase duration was a primary factor in determining propulsive anterior-posterior impulse. For the practitioner, the results can be useful in the selection of pole length when the aim is to increase thrust phase duration, anterior-posterior force impulse and velocity.  相似文献   

2.
The purpose of this study was to measure alterations in sensorimotor skills and balance resulting from slackline training and conventional balance training. Forty-three physically fit subjects were randomized into three groups. Two groups practiced three times a week for 15?minutes, including at least once supervised session, on the slackline or perform conventional balance training for 6 weeks. The control group was not allowed to perform any balance training. Before and after the intervention, the subjects underwent sensorimotor and strength tests. The results of our intra-class correlation analysis showed that the stability parameters from the multifunctional training device (MFT, 0.7), the height during the countermovement jump (CMJ, 0.95) and the maximum force (0.88) during leg press showed excellent reliability. A post hoc comparison indicated a larger effect of conventional training (almost 11% reduction in MFT stability) compared with slackline training in group-wide comparisons of the pre- to the post-training measurements. The factor analysis showed that stability and sensorimotor assessment using MFT were correlated, as were height during CMJ and maximal force during leg press, which represented dynamic strength. Because CMJ had the highest intra-class correlation value, it was chosen over maximum force from leg press. For these reasons, only two out of nine measured parameters, namely MFT stability and CMJ, were analysed across groups. The only observed difference between the two groups was MFT stability (slackline???1.5%, conventional???13%), whereas the improvement of CMJ was the same (slackline?+?3%, conventional?+?3%). It can be concluded that slacklining is partly complementary to conventional sensorimotor training.  相似文献   

3.
The purpose of this study was to evaluate the behaviour of cross-country ski poles during double poling on a treadmill using three-dimensional kinematics. The results were compared with standard laboratory tests of the pole manufacturers. A total of 18 skiers were analysed at two speeds (85% and 95% of the maximal speed) at grades of 1.5% and 7%. Variables describing cycle characteristics, bending stiffness, bending behaviour, and trajectories of the pole markers were analysed. Triangular-shaped poles demonstrated the greatest stiffness and lowest variability in maximal bending. Softer poles demonstrated greater variability in bending behaviour and lost ground contact at high skiing speeds, which for some skiers resulted in failure to complete high-speed tests. Considerable variations in pole behaviour for similar poles between skiers were observed, which might be attributed to differences in technique, indicating that mechanical properties of the poles did not exclusively determine pole behaviour in the dynamic situation. The greatest magnitude of pole bending was in the middle part of the pole, which differed from the standard static pole analysis of the manufacturer. Increases in grade demonstrated the greatest effect on pole bending. Distinct differences from the pole manufacturers' laboratory measures were apparent, suggesting that basic pole testing might be adapted.  相似文献   

4.
Skiing     
The purpose of the investigation was to study the relationship between thrust phase duration, ground reaction force, velocity increase after pole thrust and pole angles versus pole length during double poling in roller skiing. Seven male regional elite cross‐country skiers volunteered as subjects for the study. The subjects performed a maximal double pole thrust on roller skis with each of the three different pole lengths: ‘short’, self‐selected (normal) and ‘long’. The short and long poles were 7.5 cm shorter and 7.5 cm longer than the self‐selected pole length. The subjects made seven maximal pole thrusts with each pole length, which were randomly selected during 21 trials. For each trial the subjects accelerated from a 1.2 m high downhill slope attaining a speed of 3.92 m.s‐1 before making a maximal double pole thrust on a force plate placed at the bottom of the slope. The vertical (Fz), anterior‐posterior (Fy) and medio‐lateral (Fx) reaction forces of the left pole were measured by the force plate. The positions of the pole were recorded in 3‐D by an opto‐electronic system. Thrust phase duration, impulse, mean force, velocity increase after pole thrust and pole angles were calculated from the recorded data. Double poling with long poles produced a significantly larger propulsive anterior‐posterior reaction force impulse and velocity increase than normal (p < .05) and short poles (p < .05). This was in spite of a larger mean anterior‐posterior reaction force being produced with short poles. Thus, thrust phase duration was a primary factor in determining propulsive anterior‐posterior impulse. For the practitioner, the results can be useful in the selection of pole length when the aim is to increase thrust phase duration, anterior‐posterior force impulse and velocity.  相似文献   

5.
In this study, we investigated a new method of training for maximal strength and flexibility, which included exertion with superimposed vibration (vibratory stimulation, VS) on target muscles. Twenty‐eight male athletes were divided into three groups, and trained three times a week for 3 weeks in one of the following conditions: (A) conventional exercises for strength of the arms and VS stretching exercises for the legs; (B) VS strength exercises for the arms and conventional stretching exercises for the legs; (C) irrelevant training (control group). The vibration was applied at 44 Hz while its amplitude was 3 mm. The effect of training was evaluated by means of isotonic maximal force, heel‐to‐heel length in the two‐leg split across, and flex‐and‐reach test for body flexion. The VS strength training yielded an average increase in isotonic maximal strength of 49.8%, compared with an average gain of 16% with conventional training, while no gain was observed for the control group. The VS flexibility training resulted in an average gain in the legs split of 14.5 cm compared with 4.1 cm for the conventional training and 2 cm for the control groups, respectively. The ANOVA revealed significant pre‐post training effects and an interaction between pre‐post training and ‘treatment’ effects (P< 0.001) for the isotonic maximal force and both flexibility tests. It was concluded that superimposed vibrations applied for short periods allow for increased gains in maximal strength and flexibility.  相似文献   

6.
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   

7.
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   

8.
The aim of this study was to compare selected physiological variables and performance markers of soldiers from two "elite" units of the British Army. Ten soldiers from each of the two units were recruited for this study (n = 20). All participants completed three tests while carrying a 20 kg backpack load: (1) a maximal treadmill test using the Bruce protocol; (2) a 2 mile backpack run test specific to Unit A on a consistently flat tarmac road; and (3) a 29 km time-trial over hilly terrain typical of a mountainous area used by Unit B for performance assessment. Heart rate, maximal blood lactate concentration and performance (run time) were assessed during all three tests, with peak oxygen uptake also being measured during the maximal treadmill test. Measurements of anthropometry, isokinetic strength and mental toughness (MT48) were also recorded. There were no significant differences in terms of performance markers between the units (P > 0.05). Performance on the maximal treadmill test correlated with performance on the 2 mile backpack run test (r = -0.57) and 29 km time-trial (r = -0.66). Performance on the 2 mile backpack run test in turn correlated with 29 km time-trial performance (r = -0.77), accounting for 59% of the variance. In conclusion, the maximal treadmill test and the 2 mile backpack run test are useful indicators of performance on the arduous hill march and could be employed in the screening and selection of potential recruits.  相似文献   

9.
This study aims to re-examine to what extent the testing procedure of the Artificial Athlete Berlin (DIN18032) is a valid evaluation method to assess the shock absorbency of third generation artificial turf (3-g turf) and to establish a new testing procedure, which precisely reflects the acute load by human sports action. The DIN test was conducted for 3-g turfs with different infill component. The baseline of the load of acute human sports action was obtained from the ground reaction force underneath the standard type of 3-g turf sample during landing from a 55-cm height with minimal shock attenuation. For reproducing the force similar to such a hard landing, a testing rig was developed and the same 3-g turf samples were tested. The DIN test failed to distinguish most types of 3-g turf and was found to be inappropriate to evaluate the shock absorbency of the 3-g turf mainly due to bouncing actions of the test foot on measured samples. In contrast, the newly developed testing rig succeeded in illustrating the differences of shock attenuation properties among most types of 3-g turfs in a high loading condition. In terms of players’ safety, the necessity of high loading test using an alternative testing procedure was highlighted.  相似文献   

10.
In this study, we examined the relationship between anthropometric, strength and power characteristics of rugby forwards, their body position when scrummaging, and their ability to apply force when scrummaging. Force applied to an instrumented scrum machine was measured for 56 players, both individually and as scrum packs. Measurements of body position for individuals were made by digitizing videotape records of the trials. Forty players subsequently had their anthropometry assessed and completed several strength and power tests. Body mass, each component of somatotype, maximal anaerobic power developed on a cycle ergometer, and isokinetic knee extension strength correlated significantly with individual scrummaging force. A regression model (P?0.001) including body mass, mesomorphy, maximal anaerobic power and hip angle while in the scrummaging position accounted for 45% of the variance in individual scrummaging force. The packs that produced the largest scrummaging forces were, in general, characterized by a greater pack force to sum of individual force ratio than the packs producing lower forces. Our results emphasize the need for a scrum pack to develop technique and coordination as a unit to maximize scrummaging force.  相似文献   

11.
In this study, we examined the relationship between anthropometric, strength and power characteristics of rugby forwards, their body position when scrummaging, and their ability to apply force when scrummaging. Force applied to an instrumented scrum machine was measured for 56 players, both individually and as scrum packs. Measurements of body position for individuals were made by digitizing videotape records of the trials. Forty players subsequently had their anthropometry assessed and completed several strength and power tests. Body mass, each component of somatotype, maximal anaerobic power developed on a cycle ergometer, and isokinetic knee extension strength correlated significantly with individual scrummaging force. A regression model (P < 0.001) including body mass, mesomorphy, maximal anaerobic power and hip angle while in the scrummaging position accounted for 45% of the variance in individual scrummaging force. The packs that produced the largest scrummaging forces were, in general, characterized by a greater pack force to sum of individual force ratio than the packs producing lower forces. Our results emphasize the need for a scrum pack to develop technique and coordination as a unit to maximize scrummaging force.  相似文献   

12.
Purpose: An advanced system for the assessment of climbing-specific performance was developed and used to: (a) investigate the effect of arm fixation (AF) on construct validity evidence and reliability of climbing-specific finger-strength measurement; (b) assess reliability of finger-strength and endurance measurements; and (c) evaluate the relationship between finger flexor all-out test scores and climbing ability. Methods: To determine the effect of AF, 22 male climbers performed 2 maximal strength and all-out tests with AF (shoulder and elbow flexed at 90°) and without AF (shoulder flexed at 180° and elbow fully extended). To determine reliability, 9 male climbers completed 2 maximal strength tests with and without AF and an all-out and intermittent test without AF. Results: The maximal strength test without AF more strongly determined climbing ability than the test with AF (r2 = .48 and r2 = .42 for sport climbing; r2 = .66 and r2 = .42 for bouldering, respectively). Force and time variables were highly reliable; the rate of force development and fatigue index had moderate and low reliability. The maximal strength test with AF provided slightly higher reliability than without AF (intraclass correlation coefficient [ICC] = 0.94, ICC = 0.88, respectively). However, smaller maximal forces were achieved during AF (484 ± 112 N) than without AF (546 ± 132 N). All-out test average force had sufficiently high reliability (ICC = 0.92) and a relationship to sport climbing (r2 = .42) and bouldering ability (r2 = .58). Conclusion: Finger strength and endurance measurements provided sufficient construct validity evidence and high reliability for time and force parameters. Arm fixation provides more reliable results; however, the position without AF is recommended as it is more related to climbing ability.  相似文献   

13.
Maximal strength training with a focus on maximal mobilization of force in the concentric phase improves endurance performance that employs a large muscle mass. However, this has not been studied during work with a small muscle mass, which does not challenge convective oxygen supply. We therefore randomized 23 adult females with no arm-training history to either one-arm maximal strength training or a control group. The training group performed five sets of five repetitions of dynamic arm curls against a near-maximal load, 3 days a week for 8 weeks. This training increased maximal strength by 75% and improved rate of force development during both strength and endurance exercise, suggesting that each arm curl became more efficient. This coincided with a 17-18% reduction in oxygen cost at standardized submaximal workloads (work economy), and a 21% higher peak oxygen uptake and 30% higher peak load during maximal arm endurance exercise. Blood flow assessed by Doppler ultrasound in the axillary artery supplying the working biceps brachii and brachialis muscles could not explain the training-induced adaptations. These data suggest that maximal strength training improved work economy and endurance performance in the skeletal muscle, and that these effects are independent of convective oxygen supply.  相似文献   

14.
目的:探讨各种轻负荷条件下半蹲起力-时间曲线特征和力增加速率与各种肌肉收缩运动表现的相关性;分析轻负荷抗阻练习与等长、等动及纵跳动作的下肢发力特征间的内在生物力学联系。方法:募集日本筑波大学9名男子运动员,在测力台上进行不同负荷的半蹲起(Half-squat,HS)以获取地面反作用数据(GRF),进而计算出力增加速率(RFD)。进行最大负荷(>1RM)的静力收缩以测得最大力量(Fmax),进行各种纵跳练习(SJ、CMJ、RJ)以测得跳跃能力参数;采用多关节等速测力系统测取不同角速度下的膝伸展峰力矩(Peak torque,PT);采用Pearson相关系数反映不同负荷半蹲起RFD值与最大力量、跳跃能力和等速膝伸展峰力矩间的相关关系。结果:1)轻负荷半蹲起动作的平均发力时间在0.2 s以内,RFD值在0~60 ms区间内相近或相等;2)20 kg、40 kg和60 kg半蹲起RFD值与Fmax之间无相关关系(P>0.05),60 kg半蹲起RFD值与300°/s条件下的膝伸展PT存在显著性正相关(P<0.01);3)CMJ-JH和RJ-JH显著高于SJ-JH(P<0.01),而RJ的RFD值显著大于SJ和CMJ(P<0.01);4)40 kg半蹲起RFD值与SJ-JH、CMJ-JH之间存在显著性正相关(P<0.05);5)RFD与Fpeak和T-Fpeak之间分别存在显著性正相关和负相关(P<0.05),但Fpeak和T-Fpeak之间未存在相关关系(P>0.05)。结论:轻负荷半蹲起可以作为短跑、游泳等项目运动员起动力量训练手段,以减少起跑和起跳入水的反应时,强化起点技术;在20~60 kg负荷范围内,RFD值在短时间内保持相对恒定;轻负荷半蹲起在保持高输出功率的同时,具有更加高速的发力特征,可作为提高优秀运动员纵跳能力的有效练习手段。  相似文献   

15.
The purpose of this study was to examine the interaction of players’ skill level, body strength, and sticks of various construction and stiffness on the performance of the slap and wrist shots in ice hockey. Twenty male and twenty female subjects were tested. Ten of each gender group were considered skilled and ten unskilled. In addition to general strength tests, each subject performed the slap and wrist shots with three stick shafts of different construction and stiffness. Shot mechanics were evaluated by simultaneously recording ground reaction forces from a force plate, stick movement and bending from high speed filming and peak puck velocity from a radar gun. Data were analysed with a 4-way repeated measures ANOVA for several dependent variables including peak puck velocity, peak Z (vertical) force, peak bending and stick to ground angles, peak angular deflection of the shaft, and hand placement on the stick. The results indicated that: 1) the slap shot was much faster than the wrist shot corresponding to greater vertical loading force, stick bending, and greater width of the hand placement; 2) the puck velocity was influenced by skill level and body strength but not stick type; and, 3) that skilled players were able to generate more vertical force and bend of the stick, in part, by adjusting their hand positions on the stick. Further studies are needed to address the specific influence of body strength and skill on the techniques of these shots and in relation to stick material and construction properties.  相似文献   

16.
The purpose of this study was to quantify the inter-session reliability of force–velocity–power profiling and estimated maximal strength in youth. Thirty-six males (11–15 years old) performed a ballistic supine leg press test at five randomized loads (80%, 100%, 120%, 140%, and 160% body mass) on three separate occasions. Peak and mean force, power, velocity, and peak displacement were collected with a linear position transducer attached to the weight stack. Mean values at each load were used to calculate different regression lines and estimate maximal strength, force, velocity, and power. All variables were found reliable (change in the mean [CIM] = ? 1 to 14%; coefficient of variation [CV] = 3–18%; intraclass correlation coefficient [ICC] = 0.74–0.99), but were likely to benefit from a familiarization, apart from the unreliable maximal force/velocity ratio (CIM = 0–3%; CV = 23–25%; ICC = 0.35–0.54) and load at maximal power (CIM = ? 1 to 2%; CV = 10–13%; ICC = 0.26–0.61). Isoinertial force–velocity–power profiling and maximal strength in youth can be assessed after a familiarization session. Such profiling may provide valuable insight into neuromuscular capabilities during growth and maturation and may be used to monitor specific training adaptations.  相似文献   

17.
高水平女子撑竿跳运动员的大周期力量训练分期   总被引：1，自引：0，他引：1  
李山  谢慧松  周铁民 《体育学刊》2006,13(6):107-110
对我国2名国家队高水平女子撑竿跳运动员一个参赛周期的力量训练分期进行研究。结果认为:(1)根据撑竿跳运动专项力量构成特点,一个参赛周期的力量训练可沿基础性全身力量训练、原动肌肉体积适度增加训练、原动肌肉最大力量提高训练、专项爆发力提高训练、最大力量与专项爆发力保持训练途径进行阶段性复合训练;(2)分期式力量训练不仅有助于专项力量的转化与提高,而且可以保证竞赛期专项力量在比赛中发挥积极的作用。通过个案研究发现,2名国家队高水平女子撑竿跳运动员经过系统性力量分期训练,在各项最大力量(负重半蹲、上斜卧推、肩上推举、硬拉、腿弯举、提踵)与专项力量指标(下肢无氧功率自行车测试、助跑5级跨跳远、跳远)上较上一训练周期有了较明显的提高,并促进了专项成绩的进一步提高。  相似文献   

18.
Abstract

The aim of this study was to compare selected physiological variables and performance markers of soldiers from two “elite” units of the British Army. Ten soldiers from each of the two units were recruited for this study (n = 20). All participants completed three tests while carrying a 20 kg backpack load: (1) a maximal treadmill test using the Bruce protocol; (2) a 2 mile backpack run test specific to Unit A on a consistently flat tarmac road; and (3) a 29 km time-trial over hilly terrain typical of a mountainous area used by Unit B for performance assessment. Heart rate, maximal blood lactate concentration and performance (run time) were assessed during all three tests, with peak oxygen uptake also being measured during the maximal treadmill test. Measurements of anthropometry, isokinetic strength and mental toughness (MT48) were also recorded. There were no significant differences in terms of performance markers between the units (P > 0.05). Performance on the maximal treadmill test correlated with performance on the 2 mile backpack run test (r = ?0.57) and 29 km time-trial (r = ?0.66). Performance on the 2 mile backpack run test in turn correlated with 29 km time-trial performance (r = ?0.77), accounting for 59% of the variance. In conclusion, the maximal treadmill test and the 2 mile backpack run test are useful indicators of performance on the arduous hill march and could be employed in the screening and selection of potential recruits.  相似文献   

19.
Thirty-eight competitive cross-country skiers were divided into three groups to assess the reliability and validity of a new double poling ergometer. Group A (n = 22) performed two maximal 60-s tests, Group B (n = 8) repeated peak oxygen uptake tests on the double poling ergometer, and Group C (n = 8) performed a maximal 6-min test on the double poling ergometer and a double poling time-trial on snow. The correlation between the power calculated at the flywheel and the power applied at the base of the poles was r = 0.99 (P < 0.05). The power at the poles was 50-70% higher than that at the flywheel. There was a high test-retest reliability in the two 60-s power output tests (coefficient of variation = 3.0%) and no significant difference in peak oxygen uptake in the two 6-min all-out tests (coefficient of variation = 2.4%). There was a strong correlation between the absolute (W) and relative power (W x kg(-1)) output in the 6-min double poling ergometer test and the double poling performance on snow (r = 0.86 and 0.89 respectively; both P < 0.05). In conclusion, our results show that the double poling ergometer has both high reliability and validity. However, the power calculated at the flywheel underestimated the total power produced and needs to be corrected for in ergonomic estimations.  相似文献   

20.
本文观察了16名女子赛艇运动员30周训练期间有氧和无氧代谢运动能力的变化。前13周以力量训练为主,后17周以专项训练为主。观察发现过多力量训练无助于有氧能力发展,在专项训练期,应保持足够强度才能在发展有氧能力的同时提高最大乳酸值。  相似文献   

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