Pacing during a cross-country mountain bike mass-participation event according to race performance,experience, age and sex

This study describes pacing strategies adopted in an 86-km mass-participation cross-country marathon mountain bike race (the ‘Birkebeinerrittet’). Absolute (km·h^?1) and relative speed (% average race speed) and speed coefficient of variation (%CV) in five race sections (15.1, 31.4, 52.3, 74.4 and 100% of total distance) were calculated for 8182 participants. Data were grouped and analysed according to race performance, age, sex and race experience. The highest average speed was observed in males (21.8?±?3.7?km/h), 16–24?yr olds (23.0?±?4.8?km/h) and those that had previously completed >4 Birkebeinerrittet races (22.5?±?3.4?km/h). Independent of these factors, the fastest performers exhibited faster speeds across all race sections, whilst their relative speed was higher in early and late climbing sections (Cohen's d?=?0.45–1.15) and slower in the final descending race section (d?=?0.64–0.98). Similar trends were observed in the quicker age, sex and race experience groups, who tended to have a higher average speed in earlier race sections and a lower average speed during the final race section compared to slower groups. In all comparisons, faster groups also had a lower %CV for speed than slower groups (fastest %CV?=?24.02%, slowest %CV?=?32.03%), indicating a lower variation in speed across the race. Pacing in a cross-country mountain bike marathon is related to performance, age, sex and race experience. Better performance appears to be associated with higher relative speed during climbing sections, resulting in a more consistent overall race speed.     

1991年亚洲自行车锦标赛1000米计时赛骑行速度的分析

对1991年亚洲自行车锦标赛1000米计时赛男女前5名运动员骑行速度的分析,呈现出以下规律:全程速度变化是由出发开始加速至第一圈末达最高点,随后逐渐减速至终点的过程,但在一圈半时减速缓慢。后四半圈速度变化波动越小,越均衡,成绩越好,表现出运动员时速控制能力强。成绩越好,耗体力越大,耗能量越多,表现体能越强,后四半圈体力波动越小,耗能量越少,表现出体力分配越合理,出现能量节省化状态。     

Somatotype and size of elite female basketball players

The aim of this study was to compare the somatotype and size of elite female basketball players in terms of playing position and team performance. Anthropometry and somatotype data were collected on 168 players from 14 countries before the Women's World Basketball Championship, Australia, 1994. There were 64 guards (mean?±?s: age 25.4?±?3.3 years, height 1.72?±?0.06?m, mass 66.1?±?6.2?kg, somatotype?=?2.9?–?3.9?–?2.6), 57 forwards (age 25.2?±?3.8 years, height 1.81?±?0.06?m, mass 73.3?±?5.9?kg, somatotype?=?2.8?–?3.5?–?3.2) and 47 centres (age 24.1?±?3.1 years, height 1.90?±?0.06?m, mass 82.6?±?8.2?kg, somatotype?=?3.2?–?3.1?–?3.4). Mean somatotypes by position were significantly different (F?=?7.73, P?<?0.01). Guards had greater mesomorphy than centres and less ectomorphy than forwards and centres. When discriminant function analysis was applied to endomorphy, mesomorphy, ectomorphy, age, height and mass, only height, mass and ectomorphy entered (Wilks' λ?=?0.351, F?=?31.40, P?<?0.000), 70% of the variance was accounted for, and 72% of players were correctly classified. In the four top versus four bottom teams, guards were taller and more ectomorphic, forwards were taller, with lower mesomorphy and higher ectomorphy, and centres did not differ. Thus there are some differences in somatotypes by position and team placing, but the combination of height, mass and ectomorphy provide the best differentiation by position.     

Towards a wearable monitoring tool for in-field ice hockey skating performance analysis

Abstract

The capturing of movements by means of wearable sensors has become increasingly popular in order to obtain sport performance measures during training or competition. The purpose of the current study was to investigate the feasibility of using body worn accelerometers to identify previous highlighted performance related biomechanical changes in terms of substantial differences across skill levels and skating phases. Twenty-two ice hockey players of different caliber were equipped with two 3D accelerometers, located on the skate and the waist, as they performed 30 m forward skating sprints on an ice rink. Two measures of the temporal stride characteristics (contact time and stride time) and one measure of the propulsive power (stride propulsion) of a skating stride were calculated and checked for discriminating effects across (i) skill levels and (ii) sprint phases as well as for their (iii) strength of association with the sprint performance (total sprint time). High caliber players showed an increased stride propulsion (+22%, P?<?0.05) and shorter contact time (?5%, P?<?0.05). All three analysed variables highlighted substantial biomechanical differences between the accelerative and constant velocity phases (P?<?0.05). Stride propulsion of acceleration strides primarily correlated to total sprint time (r?=??0.57, P?<?0.05). The results demonstrate the potential of accelerometers to assess skating technique elements such as contact time or elements characterizing the propulsive power such as center of mass acceleration, to gauge skating performance. Thus, the findings of this study might contribute to establishing wearable sensors for in-field ice hockey skating performance analysis.     

Underwater and surface strategies of 200 m world level swimmers

Pacing strategies of elite swimmers have been consistently characterised from the average lap velocities. In the present study, we examined the racing strategies of 200 m world class-level swimmers with regard to their underwater and surface lap components. The finals and semi-finals of the 200 m races at the 2013 World Swimming Championships (Barcelona, Spain) were analysed by an innovative image-processing system (InThePool® 2.0). Free swimming velocities of elite swimmers typically decreased throughout the 200 m race laps (?0.12 m · s^–1, 95% CI ?0.11 to ?0.14 m · s^–1, P = 0.001, η² = 0.81), whereas underwater velocities, which were faster than free swimming, were not meaningfully affected by the race progress (0.02 m · s^–1, ?0.01 to 0.04 m · s^–1, P = 0.01, η² = 0.04). When swimming underwater, elite swimmers typically travelled less distance (?0.66 m, ?0.83 to ?0.49 m, P = 0.001, η² = 0.34) from the first to the third turn of the race, although underwater distances were maintained on the backstroke and butterfly races. These strategies allowed swimmers to maintain their average velocity in the last lap despite a decrease in the free swimming velocity. Elite coaches and swimmers are advised to model their racing strategies by considering both underwater and surface race components.     

世界优秀短道速滑运动员500m滑行轨迹的运动学研究

目的：通过对现场采集的短道速滑500 m项目的优秀运动员运动视频进行处理,获取相关运动学参数,揭示优秀短道速滑运动员滑行运动学参数特征,为运动员科学训练提供依据。方法：通过单台摄像机定点拍摄获取比赛录像,无须在现场放置框架,利用冰面现有文字和线段进行摄像机空间标定,利用SIMImotion解析软件得到运动员滑行轨迹的像坐标,最后通过射影变换原理获取运动员在冰面上的滑行轨迹等运动学指标。结果：数据显示在第三圈男女平均速度都达到最大,男子最大圈平均速度为14.14 m/s,女子为13.07 m/s。男女直道平均速度、弯道平均速度、入弯瞬时速度和出弯瞬时速度都在第5次达到最大值。男子直道最大平均速度为14.13 m/s,女子为13.13 m/s;男子弯道最大平均速度为14.70 m/s,女子为13.51 m/s;男子入弯最大瞬时速度为14.76 m/s,女子为13.66 m/s;男子出弯道最大瞬时速度为14.21 m/s,女子为13.12 m/s。起跑到第8步时,男女瞬时速度分别达到了8.39 m/s和7.63 m/s,男女步长分别达到2.98 m和2.44 m。结论：(1)利用射影变换原理完成运动员比赛滑行路线的标定,为短道速滑研究提供了一种新方法。(2)优秀短道速滑运动员在500 m滑行中弯道速度贡献大于直道,起跑爆发力对抢位战术影响较大,运动员体能情况对最后两圈影响较大。     

我国备战2010年冬奥会潜在优势项目与发展对策

备战2010年冬奥会是当前我国冬季体育工作的首要任务,认为雪上女子单板U型场地滑雪、女子冰壶、男子短距离速度滑冰、女子短道速滑1000m、1500m和接力赛项目是我国参加冬奥会的潜在优势项目。提出加强教练员队伍的建设,选择科学、合理的训练模式,加强科研、保健、信息与后勤保障工作,开展政治思想工作等发展对策,最大程度地发挥举国体制优势,为更好地完成温哥华冬奥会的备战与参赛任务提供参考。     

浅谈中国女子曲棍球队短角球战术研究

短角球是曲棍球比赛中最有效的得分手段,它具有破门速度短、配合方式灵活、防守难度大等特点,一个球队短角球成功率的高低是该队能否取得胜利的重要因素;很多大赛、重要比赛的结果也是由短角球的成功率来决定的,因此各国球队都将其作为研究的重点。通过对中国队在重大比赛中短角球战术的技术统计,比较在相同赛事中中国女曲与其他参赛队之间短角球的进攻和防守,中国女曲在各大赛中短角球的进攻和防守做出比较分析,揭示短角球战术在中国女曲中的重要性,找出中国女曲与世界强队之间在短角球战术上的差距和不足,并试图揭示中国女曲短角球成功率与比赛结果间的关系。最后针对分析结果,对中国女曲提出意见和建议。     

Running speed-induced changes in foot contact pattern influence impact loading rate

Purpose. We aimed to determine the effect of speed-induced changes in foot contact patterns on the vertical instantaneous loading rate (VILR). We hypothesized that transition runners, i.e. runners that shift towards a mid- (MF) or forefoot contact pattern (FF) when running speed increases, show smaller increases in VILR than non-transition runners, i.e. runners that remain with a rearfoot contact pattern (RF).

Methods. Fifty-two male and female runners ran overground at 3.2, 4.1, 5.1 and 6.2?m?s^?1. Ground reaction forces, lower limb sagittal plane knee and ankle kinematics and plantar pressures were recorded. Multi-level linear regression models were used to assess differences between transition and non-transition runners.

Results. Non-transition runners experienced larger speed-induced increases in VILR (48.6?±?2.6?BW?s^?1 per m?s^?1) than transition runners (–1.4?±?7.6?BW?s^?1 per m?s^?1). Transition runners showed higher VILRs and a more flat foot touch down at the same pre-transition speed than non-transition runners.

Conclusion. When running speed increases, some runners transition towards more anterior foot contact patterns. This reduces or even eliminates the speed-induced increase in VILR. This result is especially the case for those RF runners who already have relatively high VILRs and flat foot positioning at slower running speeds.     

短道速滑个人项目体力分配策略研究

目的：探析短道速滑个人项目两届冬奥会及冬奥会与世锦赛体力分配策略规律差异。方法：收集整理索契、平昌冬奥会,以及2014—2017年世锦赛短道速滑个人项目相关数据,分析单圈用时、肯德尔相关系数。结果：（1）冬奥会各单项单圈用时不同程度地少于世锦赛,平昌不同程度地少于索契;（2）除2016世锦赛500 m,其他赛事均全程具有显著相关（P＜0.05）;（3）除索契冬奥会女子1 000 m,其他赛事均较早出现显著相关（P＜0.05）,平昌冬奥会男子与女子均在第7、8圈为高相关（r≥0.70）;（4）平昌冬奥会1 500 m男子第12、13圈,女子第13圈为高相关（r≥0.70）,两者均从第9圈开始出现显著相关（P＜0.05）。结论：500 m出发位置尤为重要,高速滑行中稳固站位能力需求突出,冬奥会中对全程维持速度能力的要求逐步提高;冬奥会1 000 m与1 500 m比赛争夺有利位置战术的实施位置较以往更为靠后。     

Physiological Correlates of Female Road Racing Performance

Abstract

The purpose of this study was to determine the relationship between female distance running performance on a 10 km road race and body composition, maximal aerobic power ([Vdot]O_{2 max} ), running economy (steady-state [Vdot]O₂ at standardized speeds), and the fractional utilization of [Vdot]O_2max at submaximal speeds (% [Vdot]O_2max ). The subjects were 14 trained and competition–experienced female runners. The subjects averaged 43.7 min on the 10 km run, 53.0 ml · kg^?1 · min^?1 on [Vdot]O_2max , and 33.9, 37.7, and 41.8 ml · kg^?1 · min^?1 for steady-state [Vdot]O₂ at three standardized running paces (177, 196, and 215 m · min^?1). The mean values for fractional utilization of aerobic capacity for these three submaximal speeds were 64.3, 71.4, and 79.3% [Vdot]O_2max , respectively. Significant (p < 0.01) relationships with performance were found for [Vdot]O_2max (r = ?0.66) and % [Vdot]O_2max at a standardized speed (r = 0.65). No significant (p > 0.05) relationships were found between running performance and either running economy or relative body fat. As with male heterogeneous groups, trained female road racing performance is significantly related to [Vdot]O_2max and % [Vdot]O_2max , but not related to body composition or running economy. It was further concluded that on a 10 km road race, trained females operate at a % [Vdot]O_2max similar to that of their trained male counterparts.     

The effects of work – rest duration on intermittent exercise and subsequent performance

This study examined the effects of different work?–?rest durations during 40?min intermittent treadmill exercise and subsequent running performance. Eight males (mean?±?s: age 24.3?±?2.0 years, body mass 79.4?±?7.0?kg, height 1.77?±?0.05?m) undertook intermittent exercise involving repeated sprints at 120% of the speed at which maximal oxygen uptake (v-[Vdot]O_2max) was attained with passive recovery between each one. The work?–?rest ratio was constant at 1:1.5 with trials involving short (6:9?s), medium (12:18?s) or long (24:36?s) work?–?rest durations. Each trial was followed by a performance run to volitional exhaustion at 150% v-[Vdot]O_2max. After 40?min, mean exercise intensity was greater during the long (68.4?±?9.3%) than the short work?–?rest trial (54.9?±?8.1% [Vdot]O_2max; P?<?0.05). Blood lactate concentration at 10?min was higher in the long and medium than in the short work?–?rest trial (6.1?±?0.8, 5.2?±?0.9, 4.5?±?1.3?mmol?·?l^?1, respectively; P?<?0.05). The respiratory exchange ratio was consistently higher during the long than during the medium and short work?–?rest trials (P <?0.05). Plasma glucose concentration was higher in the long and medium than in the short work?–?rest trial after 40?min of exercise (5.6?±?0.1, 6.6?±?0.2 and 5.3?±?0.5?mmol?·?l^?1, respectively; P?<?0.05). No differences were observed between trials for performance time (72.7?±?14.9, 63.2?±?13.2, 57.6?±?13.5?s for the short, medium and long work?–?rest trial, respectively; P = 0.17), although a relationship between performance time and 40?min plasma glucose was observed (P?<?0.05). The results show that 40?min of intermittent exercise involving long and medium work?–?rest durations elicits greater physiological strain and carbohydrate utilization than the same amount of intermittent exercise undertaken with a short work?–?rest duration.     

Men vs. women world marathon records’ pacing strategies from 1998 to 2018

Abstract

The aim of this study was to analyse the pacing strategies adopted by elite male and female marathon runners when setting every world record since 1998. For data analysis, the total distance of the marathon was divided into eight sections of 5?km and a final section of 2.195?km, and the relative average speed of each section was calculated individually. Female athletes maintained similar speeds in the first and second half of the marathon (ES?=?0.22, small effect, p?=?0.705), whereas male athletes increased their speed as the marathon progressed (ES?=?1.18, moderate effect, p?=?0.011). However, no differences were observed between men and women in either the first (ES?=?0.56, small effect, p?=?0.290), or in the second half of the marathon (ES?=?0.60, moderate effect, p?=?0.266). When comparing the women’s world records (1998–2003) vs. men’s records (1998–2018) by sections, we observed differences at the beginning of the race (second section, ES?=?0.89, moderate effect) and at the end (last section, ES?=?0.87, moderate effect). The pace variations during the race were similar between male athletes and that of women with male pacemakers (1.53%?±?0.60 vs. 1.68%?±?0.84, respectively). However, a trend towards higher pace variations during the race in the female records with female pacemakers was observed (2.28%?±?0.95). This study shows how male and female marathon records in the last 20 years have been set using different pacing strategies. While men used a negative strategy (faster finishing), women used a less uniform pacing strategy.     

世界优秀女子500m速滑运动员全程速度节奏量化特征研究

为探讨世界优秀女子500m速滑运动员全程速度节奏问题,以个案研究法,对2008年荷兰短距离世锦赛两名优秀女子运动员比赛数据进行了量化分析,结果表明：（1）李相花入第一弯道速度较快,利用弯道加速能力一般,珍妮沃夫有意控制入第一弯道速度,弯道中加速较大,入弯道速度节奏可能是影响弯道加速能力的重要因素;（2）两次滑跑的稳定性是最终决胜的关键性因素,珍妮沃夫两次滑跑成绩稳定性优于李相花;（3）两名运动员保持高速滑行的距离较长,且全程滑跑速度平稳无过大波动起伏;（4）虽然在个别环节速度节奏存在差异,但两名运动员全程速度曲线的总体趋势较一致,表明优秀运动员的速度变化具有一定的规律性;（5）＂一拼到底＂的滑跑策略可能不是一种最佳选择,适当控制进弯道速度和出弯道后稍作调整再进行直道加速,可能更有利于创造优异成绩。     

Hip adductor muscle function in forward skating

Adductor strain injuries are prevalent in ice hockey. It has long been speculated that adductor muscular strains may be caused by repeated eccentric contractions which decelerate the leg during a stride. The purpose of this study was to investigate the relationship of skating speed with muscle activity and lower limb kinematics, with a particular focus on the role of the hip adductors. Seven collegiate ice hockey players consented to participate. Surface electromyography (EMG) and kinematics of the lower extremities were measured at three skating velocities 3.33 m/s (slow), 5.00 m/s (medium) and 6.66 m/s (fast). The adductor magnus muscle exhibited disproportionately larger increases in peak muscle activation and significantly prolonged activation with increased speed. Stride rate and stride length also increased significantly with skating velocity, in contrast, hip, knee and ankle total ranges of motion did not. To accommodate for the increased stride rate with higher skating speeds, the rate of hip abduction increased significantly in concert with activations of adductor magnus indicating a substantial eccentric contraction. In conclusion, these findings highlight the functional importance of the adductor muscle group and hip abduction–adduction in skating performance as well as indirectly support the notion that groin strain injury potential increases with skating speed.     

Relationship between exchange block time in swim starts and final performance in relay races in international championships

Abstract

The purpose of this study was to investigate the association between relay exchange block time and final performance in 4 × 100-m and 4 × 200-m freestyle and 4 × 100-m medley relays as a function of sex (men and women) and classification (medallists and non-medallists) in international competitions. Nineteen international competitions covering a 13-year period (2000–2012) were analysed retrospectively. The data corresponded to a total of 827 team relay histories (407 men, 420 women). Kruskal–Wallis and Mann–Whitney tests were performed to determine any differences by sex, classification, and event. Similarly, the relationship between the exchange block times and final performance was examined by means of a Pearson correlation analysis. In the three events, the men’s exchange block times were shorter than those of the women (η² = 0.049–0.109; P < 0.001). The exchange block time was especially relevant for the women’s relay medallists in the 4 × 100-m freestyle (r = 0.306, P = 0.021) and 4 × 100-m medley (r = 0.385, P = 0.011), while for men the relationship was clearer for the non-medallists. These results suggest that the exchange block time should be considered as one of the performance parameters of swimming relay starts, and thus should be included explicitly as part of training. In particular, the coach could design training targeted at standardising an optimal exchange block time equal to or less than that expected for other teams in the competition.     

Push-off forces in elite short-track speed skating

This study performed an analysis of the push-off forces of elite-short-track speed skaters using a new designed instrumented short-track speed skate with the aim to improve short-track skating performance. Four different skating strokes were distinguished for short-track speed skaters at speed. The strokes differed in stroke time, force level in both normal and lateral directions, and the centre of pressure (COP) on the blade. Within the homogeneous group of male elite speed skaters (N = 6), diversity of execution of the force patterns in the four phases of skating was evident, while skating at the same velocities. The male participants (N = 6) with a better personal record (PR) kept the COP more to the rear of their blades while hanging into the curve (r = 0.82, p < 0.05), leaving the curve (r = 0.86, p < 0.05), and entering the straight (r = 0.76, p < 0.10). Furthermore, the male skaters with a better PR showed a trend of a lower lateral peak force while entering the curve (r = 0.74, p < 0.10). Females showed a trend towards applying higher body weight normalised lateral forces than the males, while skating at imposed lower velocities.     

Impact of hockey skate design on ankle motion and force production

Dynamic forces and range of motion (ROM) were measured during on-ice skating using a standard hockey skate and a modified skate (MS) with an altered tendon guard and eyelet configuration. The objective of this study was to determine if these modifications resulted in biomechanical and performance changes during on-ice skating skills. The right skate of each type was instrumented with a calibrated strain gauge force transducer system to measure medial?Clateral and vertical forces during ice skating. In addition, a goniometer was placed about the ankle and rear foot to measure ROM during skating. Ten subjects executed three skills: forward skating, crossovers inside foot and crossovers outside foot. The MS demonstrated significant gains of 5°?C9° in dorsi-plantarflexion ROM (p?<?0.05). Total peak force occurred later during plantarflexion, suggesting a more prolonged and effective force generation with the MS during a given skating stride. A 14?C20?% increase (p?>?0.05) in mean work and power output was noted with the MS, although no improved times were observed during the skating skills. Potentially, some players may need a period of familiarization to take advantage of the design alterations of the MS.     

Bilateral inter-arm coordination in freestyle swimming: Effect of skill level and swimming speed

The aim of this study was to examine the influence of level of skill and swimming speed on inter-limb coordination of freestyle swimming movements. Five elite (2 males, 3 females; age 18.9?±?1.0 years, height 1.71?±?0.04?m, body mass 62.1?±?7.0?kg) and seven novice (age 22.0?±?2.0 years, height 1.77?±?0.04?m, body mass 74.8?±?9.0?kg) swimmers swam a sprint and a self-paced 25?m freestyle trial. The swimming trials were recorded by four digital cameras operating at 50 Hz. The digitized frames underwent a three-dimensional direct linear transformation to yield the three-dimensional endpoint kinematic trajectories. The spatio-temporal relationship between the upper limbs was quantified by means of the peak amplitude and time lag of the cross-correlation function between the right and left arm's endpoint trajectories. A strong anti-phase coupling between the two arms, as confirmed by peak amplitudes greater than 0.8, was noted for both groups and swimming speeds. Significantly higher (P <?0.05) peak amplitudes were observed for the sprint compared with self-paced swimming. No significant differences in the strength of inter-limb coupling were noted between the elite and novice swimmers (P >?0.05). Time lags were very close to 0?ms and did not differ between groups or swimming speeds. We conclude that in freestyle swimming, the intrinsic anti-phase (180° phase difference) inter-limb relationship is strongly preserved despite the physically powerful environmental influence of the water and this “preferred” pattern is not affected by level of skill. In contrast, increasing movement speed results in stronger inter-limb coupling that is closer to the anti-phase inter-limb relationship.     

Age and gender interactions in short distance triathlon performance

Abstract

This study investigated the participation and performance trends as well as the age and gender interaction at the Olympic distance ‘Zürich Triathlon’ (1.5?km swim, 40?km cycle and 10?km run) from 2000 to 2010 in 7,939 total finishers (1,666 females and 6,273 males). Female triathletes aged from 40 to 54 years significantly (P?<?0.05) increased their participation while the participation of younger females and males remained stable. Males of 50–54 years of age and females of 45–49 years of age improved their total race time. For elite top five overall triathletes, mean gender differences in swimming, cycling, running and overall race time were 15.2?±?4.6%, 13.4?±?2.3%, 17.1?±?2.5%, and 14.8?±?1.8%, respectively. For both elite and age group athletes, the gender difference in cycling time was significantly (P?<0.001) lower than for swimming and running. The gender difference in overall Olympic distance triathlon performance increased after the age of 35 years, which appeared earlier compared to long distance triathlon as suggested by previous studies. Future investigations should compare gender difference in performance for different endurance events across age to confirm a possible effect of exercise duration on gender difference with advancing age.