Evaluation of a specific test in cross-country skiing

Six Danish male cross-country skiers were studied during the end-of-summer and winter seasons. Their maximal oxygen uptake was measured while running on a treadmill and using a ski ergometer incorporating the double-poling technique. Maximal oxygen uptake during treadmill running and double-poling was correlated with performance, expressed as a ranking score during 10 ski races. The tests were undertaken in September, December and April. Upper body maximal oxygen uptake increased 5.8% from September to December, decreasing to 2.3% above the September level in April. Upper body work output (2 min at maximal intensity) increased 11.8% from September to December (P less than 0.05). The relationship between upper body and leg maximal oxygen uptake--the upper body/leg ratio--was 89.4% in September. In four skiers, both treadmill and upper body tests were undertaken on each test occasion. The upper body/leg ratio changed from 87.7% in September to 95.7% in December. In April, the ratio was 91.0%. The maximal oxygen uptake measured using the ski ergometer during double-poling was significantly correlated with performance (P less than 0.05). It is concluded that the upper body ski ergometer can be used in the evaluation of elite cross-country skiers.     

Gross efficiency predicts a 6-min double-poling ergometer performance in recreational cross-country skiers

The purpose of the study was to investigate which physiological parameters would most accurately predict a 6-min, all-out, double-poling (DP) performance in recreational cross-country skiers. Twelve male recreational cross-country skiers performed tests consisting of three series lasting 10 s, one lasting 60 s, plus a 6-min, all-out, DP performance test to estimate mean and peak power output. On a separate day, gross mechanical efficiency (GE) was estimated from a 10-min, submaximal, DP test and maximal oxygen consumption (VO₂ max) was estimated from an incremental treadmill running test. Power was measured after each stroke from the acceleration and deceleration of the flywheel that induced the friction on the ergometer. The power was shown to the skier on a small computer placed on the ergometer. A multivariable correlation analysis showed that GE most strongly predicted 6-min DP performance (r = 0.79) and interestingly, neither DP VO₂ max, nor treadmill-running VO₂ max, correlated with 6-min DP performance. In conclusion, GE correlated most strongly with 6-min DP performance and GE at the ski ergometer was estimated to be 6.4 ± 1.1%. It is suggested that recreational cross-country skiers focus on skiing technique to improve gross mechanical efficiency during intense DP.     

Scaling of upper-body power output to predict time-trial roller skiing performance

Abstract

The purpose of the present study was to establish the most appropriate allometric model to predict mean skiing speed during a double-poling roller skiing time-trial using scaling of upper-body power output. Forty-five Swedish junior cross-country skiers (27 men and 18 women) of national and international standard were examined. The skiers, who had a body mass (m) of 69.3 ± 8.0 kg (mean ± s), completed a 120-s double-poling test on a ski ergometer to determine their mean upper-body power output (W). Performance data were subsequently obtained from a 2-km time-trial, using the double-poling technique, to establish mean roller skiing speed. A proportional allometric model was used to predict skiing speed. The optimal model was found to be: Skiing speed = 1.057 · W ^0.556 · m ^?0.315, which explained 58.8% of the variance in mean skiing speed (P < 0.001). The 95% confidence intervals for the scaling factors ranged from 0.391 to 0.721 for W and from ?0.626 to ?0.004 for m. The results in this study suggest that allometric scaling of upper-body power output is preferable for the prediction of performance of junior cross-country skiers rather than absolute expression or simple ratio-standard scaling of upper-body power output.     

Improving paddling efficiency through raising sitting height in female white water kayakers

The study compared female white water paddlers over two conditions: with seat raise and with no seat raise. The aim was to determine whether raising the sitting height would improve paddling efficiency. Sitting height of each participant was recorded in order to calculate the seat raise height required and three-dimensional kinematic data was collected for six participants over both conditions. Twelve measures of efficiency were utilised. The efficiency of all participants improved on the seat condition for ≥4 of the measures, with three participants showing improvement for ≥6 of the measures. The stern snaking measure had the highest value of significance (P = 0.1455) and showed an average of 11.98% reduction in movement between no seat and seat conditions. The results indicate that improvements were seen although these were individualistic. Therefore it can be concluded that it is worth experimenting with a seat raise for a female kayaker who is lacking efficiency, noting, however, that improvements might depend on anthropometrics and the seat height selected, and therefore could elicit differing results.     

2008残奥会战略与我国坐式排球运动现状

2008年北京残奥会坐式排球在体育运动中举足轻重.作者对参加2002年全国坐式排球优胜队联赛暨世锦赛选拔赛的运动队进行问卷调查与分析.结果显示,我国坐式排球开展较晚、起点低,运动员体育基础和文化素养不尽人意;教练员多数处于"打短工"、"业余性质"状态;经验不足,训练不系统,管理体制不完善.在此基础上提出了一些建议.     

Changes in performance and poling kinetics during cross-country sprint skiing competition using the double-poling technique

In this study, changes in skiing performance and poling kinetics during a simulated cross-country sprint skiing competition were investigated. Twelve elite male cross-country skiers performed simulated sprint competition (4 × 1,150 m heat with 20 min recovery between the heats) using the double-poling technique. Vertical and horizontal pole forces and cycle characteristics were measured using a force plate system (20-m long) during the starting spurt, racing speed, and finishing spurt of each heat. Moreover, heat and 20-m phase velocities were determined. Vertical and horizontal pole impulses as well as mean cycle length were calculated. The velocities of heats decreased by 2.7 ± 1.7% (p = 0.003) over the simulated competition. The 20-m spurting velocity decreased by 16 ± 5% (p < 0.002) and poling time increased by 18 ± 9% (p < 0.003) in spurt phases within heats. Vertical and horizontal poling impulses did not change significantly during the simulation; however, the mean forces decreased (p < 0.039) (vertical by 24 ± 11% and horizontal by 20 ± 10%) within heats but not between the heats. Decreased heat velocities over the simulated sprint and spurting velocities within heats indicated fatigue among the skiers. Fatigue was also manifested by decreased pole force production and increased poling time.     

体能训练对坐式滑雪运动员成绩提高的研究

体能训练的方法在坐式滑雪项目上应重点采用。为达到夺取残疾人滑雪奖牌的目标,力争下届冬季残奥会实现奖牌零的突破,应将体能训练用于残疾人雪上项目专项能力的提高上,并且提前着手进行。     

Measurement of contact forces on a kayak ergometer with a sliding footrest–seat complex

Kinematic analysis is done by measurement of the position of bodies, followed by differentiation to get the accelerations of the centres of mass, and it is widely used in sport research. Another common approach is to measure the forces directly. Our intention here is to perform both a kinematic and a kinetic analysis of the same athlete-equipment system, in this case an athlete on a sliding kayak ergometer, with the aim of exploring the errors that may occur with each measurement type. The kayak ergometer with a sliding trolley, instrumented by seven uniaxial force sensors and two goniometers, was placed in a filming area. The instrumentation was validated in the direction of the anteroposterior axis using Newton’s second law. Ten athletes paddled at 92 strokes per minute, following a stationary phase. The comparison between the net force and the time-derivative of the linear momentum indicated a friction level of about 20 N between the trolley and the frame. Other errors came mainly from the inertial parameters of the trunk. A first analysis of contact forces shows a large inter-subject variability, in particular for the forces applied to the footrest and the seat.     

Fatigue in a simulated cross-country skiing sprint competition

Abstract

The aim of this study was to assess fatigue during a simulated cross-country skiing sprint competition based on skating technique. Sixteen male skiers performed a 30-m maximal skiing speed test and four 850-m heats with roller skies on a tartan track, separated by 20 min recovery between heats. Physiological variables (heart rate, blood lactate concentration, oxygen consumption), skiing velocity, and electromyography (EMG) were recorded at the beginning of the heats and at the end of each 200-m lap during the heats. Maximal skiing velocity and EMG were measured in the speed test before the simulation. No differences were observed in skiing velocity, EMG or metabolic variables between the heats. The end (820–850 m) velocities and sum-iEMG of the triceps brachii and vastus lateralis in the four heats were significantly lower than the skiing velocity and sum-iEMG in the speed test. A significant correlation was observed between mean oxygen consumption and the change in skiing velocity over the four heats. Each single heat induced considerable neuromuscular fatigue, but recovery between the heats was long enough to prevent accumulation of fatigue. The results suggest that the skiers with a high aerobic power were less fatigued throughout the simulation.     

The effect of active sitting on trunk motion

BackgroundProlonged sitting is a risk factor for low-back pain. The primary purpose of this study is to determine if prolonged active sitting will result in increased trunk motion.MethodsFifteen healthy female participants volunteered to sit for 30 min on each of three surfaces including an air-cushion, a stability ball, and a hard surface. Trunk motion was monitored using a Vicon motion capture system, and foot center of pressure was collected with two AMTI force plates.ResultsOur findings indicated that the average speed of the trunk center of mass significantly increased with seating surface compliance. There were significant differences in right and left foot centers of pressure in the antero-posterior direction between the ball and air-cushion conditions and the ball and chair conditions.ConclusionActive sitting results in increased trunk motion and could have a positive effect on low-back health.     

Physiological aspects of competitive cross-country skiing.

The physiological demands of cross-country skiing require competitive skiers to have high maximal oxygen uptakes and anaerobic thresholds. Anaerobic capacity has a relatively less important role, but may be of greater importance today with the faster race velocities resulting from the new skiing techniques of ski skating. Although use of the ski skating techniques results in faster race velocities than the classical techniques, it has been found that under some conditions the double-pole technique is more economical than other skiing techniques. It is suggested that this results from a more effective storage and recovery of elastic energy, a greater proportion of the forces being directed along the line of travel, and a lower air resistance due to greater trunk and hip flexion with the double-pole technique. The greater economy of the double-pole technique suggests that this may be advantageous in certain race conditions if the upper body is adequately prepared. The greater propulsive forces generated with the upper body with ski skating also suggest that training of the upper body should receive more emphasis. The potential cardiovascular adaptations from cross-country ski training appear to be similar for the classical and skating techniques, yet training specificity is important for optimal performance.     

艺术体操运动员脊柱曲度异常与躯干两侧活动度和力量对称性的关系

目的:描述艺术体操运动员在日常状况下和完成专项动作时脊柱异常的表现及左右对称性,探讨与之相关的因素。方法:以9名艺术体操运动员为研究对象,进行站立位脊柱X光片拍摄,获得脊柱额状面和矢状面的弯曲方向和角度;使用三维摄像方法定量评价运动员完成后搬腿动作和侧搬腿动作时的脊柱活动幅度;运用后伸肌群和双侧屈肌群测试系统对运动员的坐姿躯干后伸和双侧侧屈等长收缩力量进行测试。比较躯干活动幅度和躯干肌肉力量的左右对称性,比较不同脊柱侧凸方向间躯干活动差异。检验脊柱弯曲角度与躯干活动特征的相关性。结果:后搬左侧腿时的活动幅度显著小于后搬右侧腿(P<0.01),对应躯干向左扭转的幅度显著大于向右扭转幅度(P<0.05)。侧搬腿时躯干活动幅度越大对应的躯干扭转角度越大。胸曲角度与右侧搬腿活动幅度角存在正相关(P<0.05),与右侧搬腿躯干扭转角之间为显著负相关(P<0.05),腰曲角度与左侧搬腿活动幅度角之间存在显著正相关(P<0.05),与右侧搬腿躯干扭转角之间存在显著负相关(P<0.05)。肌肉力量方面,胸曲角度越大,3个位置躯干后伸力矩峰值越小。侧屈力量上,运动员绝大多数角度下的右屈力量显著大于左屈力量。胸曲角度、腰°曲角度分°别与不同躯干侧屈角度下右屈力矩峰值存在显著负相关。腰曲角度与左屈0、15°、30和右屈15°位置的躯干左屈力矩峰值存在显著负相关。结论:艺术体操运动员躯干两侧活动度和肌肉力量存在不对称,后伸幅度左侧大于右侧,侧屈肌力右侧大于左侧;但这种不对称与脊柱额状面上异常弯曲无明显关系;集中于躯干右侧和躯干后伸动作的训练,可能是导致胸曲变直的原因。     

山东省优秀散打运动员有氧能力的研究

目的：探讨山东省优秀散打运动员有氧能力的特点。方法：对山东省优秀散打运动员（实验组）（n=27,其中健将级运动员5人,国家一级运动员22人）以及对照组（n=19,均为二级运动员）的肺功能、心血管功能、最大吸氧量、血乳酸以及身体成分等指标进行比较分析。结果：1）实验组具有高的瘦体重和瘦体重/体脂（P〈0.05）。2）实验组的最大吸氧量无论是其绝对值还是相对值均显著高于对照组（P〈0.05）。3）实验组和对照组在安静状态下的血乳酸均无显著性差异;但定量负荷后即刻实验组表现出较低的血乳酸值,而对照组则表现出较高的血乳酸值（P〈0.05）。结论：优秀散打运动员具有较高的有氧能力。     

RPE6-20量表预测最 氧量的实验研究进展

基于运动过程中人体心、生理对运动负荷与强度的整体感知与反映,Rating of Perceived Exertion (RPE)量表用以预测机体最大摄氧量的信效度已得到众多实验研究的证实.但由于RPE值本身具有主观性,易受人群特征影响,因此,其利用RPE量表对最大摄氧量的预测结果存在争议性.采用文献综述的方法,对现有研究中采用的RPE量表模式、实验对象、RPE6-20量表区段值与临界值、运动形式与负荷以及运动器材等方面予以概述和总结.建议:在扩大群体样本量的基础上,统一实验环境与实验程序,针对某一个或几个相似性因素群进行研究与验证;在实际应用过程中则应因人而异地选择和利用相应的程序、方法,建议与其它预测指标(如心率)相结合,以提高预测最大摄氧量的准确性.     

An Analysis of Heart Rateesponse to Exercise

Abstract

Heart rate response to exercise and recovery after exercise were studied analytically on the basis that any energy extracted from a muscle must ultimately be supplied by oxidation. Any discrepancy between oxygen supply rate and equivalent oxygen consumption rate was assumed to be made up by utilizing a finite reserve; thus allowing supply to lag consumption at the onset of exercise. Heart rate was assumed and experimentally demonstrated to be linearly related to oxygen supply rate during both steady-state and the transition period after exercise starts or stops. During recovery the withdrawals from reserves are repaid as heart rate returns to normal. Consideration of these factors resulted in an exponential heart rate response equation which closely agreed with observations. Coefficients, evaluated from experimental data, gave average time constants of 1.2 to 1.7 sec. with recovery being slower than response to exercise. Integration of this equation over the exercise range gave an estimate of the deficiency of supply as compared to consumption. A similar integration over the recovery phase indicated that in this range, supply exceeded consumption by at least as much as it was deficient during the exercise phase.     

浅谈女子武术套路运动员的合理营养

合理、均衡的膳食营乔越来越受到重视和关注,但针对女子武术运动员的合理曾乔的研冤较少。文章采用文献资料法、归纳法和类比法等研究方法,从武术套路运动的项目特征、女子运动员的能量需求特点以及合理营养的建议等方面对女子武术套路运动员的合理营养需求进行了初步的分析,以便为武术运动员的训练、比赛和恢复提供营养参考,同时也希望能引起科研人员和专家的重视,对这一问题进行全面深入的研究。     

男子l500m跑时身体各环节输出功的初步研究

运动高速摄影和跑台气体代谢法对男子中长跑运动员进行了研究。通过测定运动员1500m跑步过程中身体各环节输出功,发现运动员身体各环节输出功的比例关系为;摆动腿占比例最大,其次是支撑腿,上肢和躯干的输出功的比例相当,头部所占比例很小。运动员跑步过程中,环节内和环节之间存在能量转换,且环节之间能量转换是主要的。     

跑跳运动员脊柱腰段椎体形态和生理曲度的研究

本文用X线摄片法对照研究了跑跳运动员和普通大、中学生脊柱腰段的椎体形态和生理曲度。研究结果表明,运动员椎体高度的变化幅度大于普通学生。第五腰椎的垂直指数小于普通学生。脊柱腰段长度占身高的比例小于普通学生,显示出下肢长、躯干短的身材特点。用腰曲指数作为评价脊柱腰段生理曲度的指标,运动员和普通学生之间无显著性差异。     

运动员训练、比赛中的合理营养(综述)

对运动员在训练、比赛时的合理营养进行了综述。合理营养是运动员保持良好训练状态的物质基础 ,对运动员技能状态、体力的恢复及防治运动性疾病有重要作用。