Kinetics and kinematics analysis of incremental cycling to exhaustion

Technique changes in cyclists are not well described during exhaustive exercise. Therefore the aim of the present study was to analyze pedaling technique during an incremental cycling test to exhaustion. Eleven cyclists performed an incremental cycling test to exhaustion. Pedal force and joint kinematics were acquired during the last three stages of the test (75%, 90% and 100% of the maximal power output). Inverse dynamics was conducted to calculate the net joint moments at the hip, knee and ankle joints. Knee joint had an increased contribution to the total net joint moments with the increase of workload (5–8% increase, p < 0.01). Total average absolute joint moment and knee joint moment increased during the test (25% and 39%, for p < 0.01, respectively). Increases in plantar flexor moment (32%, p < 0.01), knee (54%, p < 0.01) and hip flexor moments (42%, p = 0.02) were found. Higher dorsiflexion (2%, for p = 0.03) and increased range of motion (19%, for p = 0.02) were observed for the ankle joint. The hip joint had an increased flexion angle (2%, for p < 0.01) and a reduced range of motion (3%, for p = 0.04) with the increase of workload. Differences in joint kinetics and kinematics indicate that pedaling technique was affected by the combined fatigue and workload effects.     

Muscle activity and pedal force profile of triathletes during cycling to exhaustion

The purpose of this study was to analyze pedaling cadence, pedal forces, and muscle activation of triathletes during cycling to exhaustion. Fourteen triathletes were assessed at the power output level relative to their maximal oxygen uptake (355 +/- 23 W). Cadence, pedal forces, and muscle activation were analyzed during start, middle, and end test stages. Normal and tangential forces increased from the start to the end of the test (-288 +/- 33 to -352 +/- 42 N and -79 +/- 45 to -124 +/- 68 N, respectively) accompanied by a decrease in cadence (96 +/- 5 to 86 +/- 6 rpm). Muscle activation increased from the start to the middle and the end in the gluteus maximus (27 +/- 5.5% and 76 +/- 9.3%) and in the vastus lateralis (13 +/- 3.5% and 27 +/- 4.4%), similar increase was observed from the start to the end in the rectus femoris and the vastus medialis (50 +/- 9.3% and 20 +/- 5.7%, respectively). Greater normal force along with enhanced activation of knee and hip extensor muscles is linked with fatigue and declines in cadence of triathletes during cycling to exhaustion.     

Similar results for face mask versus mouthpiece during incremental exercise to exhaustion

Investigations in the 1990s evaluated the influence of breathing assemblies on respiratory variables at rest and during exercise; however, research on new models of breathing assemblies is lacking. This study compared metabolic gas analysis data from a mouthpiece with a noseclip (MOUTH) and a face mask (MASK). Volunteers (7 males, 7 females; 25.1 ± 2.7 years) completed two maximal treadmill tests within 1 week, one MOUTH and one MASK, in random order. The difference in maximal oxygen consumption (VO_2max) between MOUTH (52.7 ± 11.3 ml · kg^?1 · min^?1) and MASK (52.2 ± 11.7 ml · kg^?1 · min^?1) was not significant (P = 0.53). Likewise, the mean MOUTH–MASK differences in minute ventilation (V_E), fraction of expired oxygen (FEO₂) and carbon dioxide (FECO₂), respiration rate (RR), tidal volume (V_t), heart rate (HR), and rating of perceived exertion (RPE) at maximal and submaximal intensities were not significant (P > 0.05). Furthermore, there was no systematic bias in the error scores (r = ?0.13, P = 0.66), and 12 of the 14 participants had a VO_2max difference of ≤3 ml · kg^?1 · min^?1 between conditions. Finally, there was no clear participant preference for using the MOUTH or MASK. Selection of MOUTH or MASK will not affect the participant’s gas exchange or breathing patterns.     

Effect of creatine plus caffeine supplements on time to exhaustion during an incremental maximum exercise

Abstract

This study investigated the effects of acute caffeine ingestion following short-term creatine supplementation on an incremental cycling to exhaustion task. Twelve active males performed the task under three conditions: baseline condition (BASE, no ergogenic aid), creatine plus caffeine condition (CRE + CAF), and creatine with placebo condition (CRE + PLA). Following the establishment of BASE condition, participants were administered CRE + CAF (0.3 g·kg^?1·day^?1 of creatine for 5 days followed by 6 mg·kg^?1 of caffeine 1 h prior to testing) and CRE + PLA (0.3 g·kg^?1·day^?1 of creatine for 5 days followed by 6 mg·kg^?1 of placebo 1 h prior to testing) in a double-blind, randomized crossover and counterbalancing protocol. No significant differences were observed in relative maximal oxygen consumption ([Vdot]O_2max) (51.7±5.5, 52.8±4.9 and 51.3±5.6 ml·kg^?1·min^?1 for BASE, CRE + CAF and CRE + PLA, respectively; P>0.05) and absolute [Vdot]O_2max (3.6±0.4, 3.7±0.4 and 3.5±0.5 l·min^?1 for BASE, CRE + CAF and CRE + PLA, respectively; P>0.05). Blood samples indicated significantly higher blood lactate and glucose concentrations in the CRE + CAF among those in the BASE or CRE + PLA condition during the test (P<0.05). The time to exhaustion on a cycling ergometer was significantly longer for CRE + CAF (1087.2±123.9 s) compared with BASE (1009.2±86.0 s) or CRE + PLA (1040.3±96.1 s). This study indicated that a single dose of caffeine following short-term creatine supplementation did not hinder the creatine–caffeine interaction. In fact, it lengthened the time to exhaustion during an incremental maximum exercise test. However, this regime might lead to the accumulation of lactate in the blood.     

The effects of prior incremental cycle exercise on the physiological responses during incremental running to exhaustion: relevance for sprint triathlon performance

It is common for the physiological working capacity of a triathlete when cycling and running to be assessed on two separate days. The aim of this study was to establish whether an incremental running test to exhaustion has a negative effect after a 5 h recovery from an incremental cycling test. Eight moderately trained triathletes (age, 26.2 +/- 3.4 years; body mass, 67.3 +/- 9.1 kg; VO2max when cycling, 59 +/- 13 ml x kg x min(-1); mean +/- s) completed an incremental running test 5 h after an incremental cycling test (fatigue) as well as an incremental running test without previous activity (control). Maximum running speed, maximal oxygen uptake (VO2max) and the lactate threshold were determined for each incremental running test and correlated with the average speed during a 5 km run, which was performed immediately after a 20 km cycling time-trial, as in a sprint triathlon. There were no significant differences in maximum running speed, VO2max or the lactate threshold in either incremental running test (control or fatigue). Furthermore, good agreement was found for each physiological variable in both the control and fatigue tests. For the fatigue test, there were significant correlations between the average speed during a 5 km run and both VO2max expressed in absolute terms (r = 0.83) and the lactate threshold (r = 0.88). However, maximum running speed correlated most strongly with the average speed during a 5 km run (r = 0.96). The results of this study indicate that, under controlled conditions, an incremental running test can be performed successfully 5 h after an incremental cycling test to exhaustion. Also, the maximum running speed achieved during an incremental running test is the variable that correlates most strongly with the average running speed during a 5 km run after a 20 km cycling time-trial in well-trained triathletes.     

Validity and reliability of the Moxy oxygen monitor during incremental cycling exercise

Introduction: The Moxy is a novel, cutaneously placed muscle oxygen monitor which claims to measure local oxygen saturation (SmO₂) and total haemoglobin (THb) using near-infrared spectroscopy. If shown to be reliable, its data storage and telemetric capability will be useful for assessing localised O₂ usage during field-based exercise. This study investigated the reliability of the Moxy during cycling and assessed the correlations between its measurements, whole-body O₂ consumption (VO₂) and heart rate (HR). Methods: Ten highly trained cyclists performed an incremental, step-wise cycling protocol on two occasions while wearing the Moxy. SmO₂, THb, VO₂ and HR were recorded in the final minute of each five-minute stage. Data were analysed using Spearman’s Order-Rank Coefficient (SROC), Intraclass Correlation (ICC), and Coefficient of Variance (COV). Significance was set at p?≤?.05. Results: SmO₂ showed a ‘strong’ or ‘very large’ correlation between trials (SROC: r?=?0.842–0.993, ICC: r?=?0.773–0.992, p?≤?.01) and was moderately correlated with VO₂ and HR (r?=??0.71–0.73, p?≤?.01). SmO₂ showed a moderate to high reliability at low intensities, but this decreased as relative exercise intensity increased. THb showed poor correlations between tests and with the other measured variables, but was highly reliable at all power outputs. Conclusions: The Moxy is a reliable device to measure SmO₂ at low to moderate intensities, but at higher intensities, greater variation in measurements occurs, likely due to tissue ischaemia or increased movement artefacts due to more frequent muscular contractions. THb has low variation during exercise, and does not appear to be a valid indicator of muscle oxygenation.     

Three-dimensional kinematics of competitive and recreational cyclists across different workloads during cycling

Although the link between sagittal plane motion and exercise intensity has been highlighted, no study assessed if different workloads lead to changes in three-dimensional cycling kinematics. This study compared three-dimensional joint and segment kinematics between competitive and recreational road cyclists across different workloads. Twenty-four road male cyclists (12 competitive and 12 recreational) underwent an incremental workload test to determine aerobic peak power output. In a following session, cyclists performed four trials at sub-maximal workloads (65, 75, 85 and 95% of their aerobic peak power output) at 90?rpm of pedalling cadence. Mean hip adduction, thigh rotation, shank rotation, pelvis inclination (latero-lateral and anterior–posterior), spine inclination and rotation were computed at the power section of the crank cycle (12 o'clock to 6 o'clock crank positions) using three-dimensional kinematics. Greater lateral spine inclination (p?p?p?相似文献   

Quantitative analysis of kinematics and kinetics of catchers throwing to second base

Abstract

The catcher has the most demanding position in the games of baseball and softball with no regulations on how many throws they make during game. It was the purpose of this study to describe the kinematics and kinetics of the throwing motion in catchers when throwing down to second base. It was hypothesised that younger and older catchers would display significantly different throwing kinematics and kinetics. Thirty-eight baseball and softball catchers volunteered to participate. Twenty participants were considered younger (aged 9–14, 10.95 ± 1.76 years, 151.11 ± 15.64 cm, 47.94 ± 18.84 kg) and 18 were deemed the older group (aged 15–23, 18.11 ± 2.61 years, 170.91 ± 8.67 cm, 74.88 ± 10.74 kg). Participants received a pitch and completed five accurate throws to second base in full catching gear. The average ball speed of the older catchers was 21 ± 3.58 meters per second (47 ± 8.02 mph) while the younger catchers averaged 17.2 ± 4.0 meters per second (38.6 ± 8.96 mph). Older catchers had greater shoulder elevation at ball release and significantly greater shoulder external rotation at foot contact and shoulder maximum external rotation than younger catchers. It is clear that chronological age plays a role in the throwing mechanics observed in catchers throwing down to second base, however the effects of these differences are not fully understood (i.e., skeletal maturity, experience, strength).     

药膳对运动性疲劳的机理研究

近几年中药防治运动性疲劳机理的实验研究取得了很大的进展,中西医结合开发药膳,是今后研究药膳防治运动性疲劳的发展方向。阐述了药膳防治运动性疲劳的机理,并介绍了健脾益气、补益肾气、养血补肝三种药膳中的一些实用药膳方。     

场地自行车4 000 m追逐赛不同起动方式摄氧动力模型的分析

目的：研究4 000 m场地自行车运动VO2反应,及前15 s高功率起动对运动成绩的影响。方法：11名男子自行车运动员在功率车上进行递增负荷试验和两种不同起动强度的4 000 m运动。首先进行前60 s平均功率（128±2）%MAP即（501.7±41.9）w强度对照模式运动;5 h后进行模拟模式运动,强度在第8~10 s达到最高值235%MAP（928.3±77.6）w,后逐步下降,15 s时至平均功率（421.9±40.1）w,维持15~60 s。60 s之后两组均进行自由速度模式,强度控制在380~420 w之间。结果：整个测试过程模拟组较对照组平均功率高19 w左右,有统计学差异。模拟组15~60 sVO2高于对照组,模拟组15s~60sVO2高于对照组,而AOD却低于对照组,对整个运动表现有促进作用。结论：4 000 m场地自行车运动前15 s高输出功率可伴随着更快的VO2反应而不是单一归于节省时间理论,并可促进中等距离自行车计时运动员的摄氧动员能力。     

美国短跑运动员途中跑运动学参数的因子和回归分析

选择1982年美国14名奥林匹克集训男子短跑运动员途中跑生物力学参数作为研究对象,对美国优秀男子短跑运动员途中跑运动学参数进行因子和回归分析,旨在发现和找到样本参数间的一些内在规律,为我国的短跑运动训练提供参考。     

A mathematical model for simulating cycling: applied to track cycling

A review of existing mathematical models for velodrome cycling suggests that cyclists and cycling coaches could benefit from an improved simulation tool. A continuous mathematical model for cycling has been developed that includes calculated slip and steering angles and, therefore, allows for resulting variation in rolling resistance. The model focuses on aspects that are particular, but not unique, to velodrome cycling but could be used for any cycling event. Validation of the model is provided by power meter, wheel speed and timing data obtained from two different studies and eight different athletes. The model is shown to predict the lap by lap performance of six elite female athletes to an average accuracy of 0.36% and the finishing times of two elite athletes competing in a 3-km individual pursuit track cycling event to an average accuracy of 0.20%. Possible reasons for these errors are presented. The impact of speed on steering input is discussed as an example application of the model.     

急性力竭运动对大鼠肝细胞损伤的影响

研究证明，在发育、稳态、疾病等的生理病理过程中，肝细胞会发生凋亡。通过不同强度力竭运动对大鼠肝细胞损伤的影响，以及氧自由基和线粒体摄取Ca^2＋在肝细胞损伤中所起的作用，探寻力竭运动导致肝细胞损伤的机理。     

Bilateral arm power imbalance in swim bench exercise to exhaustion

We examined the supposition that swimmers may exhibit an imbalance in bilateral arm power output during simulated swimming exercise. Ten competitive front crawl swimmers (5 males, 5 females; age 20.5+/-2.3 years; height 1.74+/-0.09 m; body mass 72.0+/-16.7 kg; 400 m freestyle swim time 278+/-20.5 s; mean +/- s) performed four incremental (10 W x min(-1)) swim ramp tests on a computer-interfaced biokinetic swim bench ergometer. External power output from each arm was measured continuously to exhaustion. The results showed that, throughout the course of the simulated swim, external power output clearly favoured the left arm (F1,9 = 12.5, P= 0.006). This was especially evident in the final 30 s to exhaustion, when 54.0+/-3.87% of external power output was derived from the left arm versus 46.0+/-3.87% from the right arm. The disparity in external power output was further highlighted when the participants were grouped into unilateral and bilateral breathers. Unilateral breathers (n = 5) produced 57.1+/-2.62% of external power output from the left armversus 42.9+/-2.62% from the right arm (P= 0.001). Bilateral breathers (n = 5) exhibited a more balanced external power output of 51.0+/-1.82% from the left arm and 49.0+/-1.82% from the right arm (P = 0.177). Evidence of power imbalance in the simulated swimming stroke may have important implications for optimizing swim performance. The observed power imbalance may be reduced when a bilateral breathing technique is adopted.     

跳远起跳时缓冲的运动学分析

跳远技术包括4个部分:助跑、起跳、腾空、落地.根据现有的资料研究表明,助跑和起跳是影响跳远成绩的主要因素.现代跳远技术认为,助跑到上板,在动作形成中不应出现显著的变化,起跳前能保持跑的动作结构,正是高水平跳远技术的主要特征.要做到这一切,下肢肌肉的缓冲能力的好坏是至关重要的.可以看出,在未来的跳远发展中,下肢缓冲动作变得尤为重要,不可忽视.     

优秀速滑运动员弯道滑行姿势的运动学分析

从弯道滑行姿势的角度,以我国优秀运动员为样本,分析其目前的身体滑行姿势和蹬冰姿势的动态变化状态,进而比较传统式冰鞋与新式冰鞋在蹬冰过程中下肢的变化特点,为教学与训练提供理论依据。     

Physiological correlates to off-road cycling performance

The aim of this study was to examine the relationships between maximal and submaximal tests for aerobic fitness and performance in an off-road cross-country circuit race. Thirteen competitive off-road male cyclists participated in the study. Peak oxygen uptake (VO2peak), peak power output, and lactate thresholds corresponding to 1 mmol x l(-1) above baseline (lactate threshold) and to 4 mmol x l(-1) (onset of blood lactate accumulation) were measured during an incremental cycling test. Race time and final ranking within the same group of cyclists were determined during a cross-country off-road competition. All correlations between the measured parameters of aerobic fitness and off-road cycling performance were significant, particularly between race time and physiological parameters scaled to body mass0.79 (r = -0.68 to -0.94; P < 0.05) and between final ranking and physiological parameters expressed relative to body mass0.79 (r = -0.81 to - 0.96; P < 0.001). Moreover, there was a large difference (effect sizes = 1.12-1.70) in all measured parameters of aerobic fitness between the group of six cyclists with a race time above the median and the group of six cyclists with a race time below the median (P < 0.05). In conclusion, the results of this study provide empirical support to the widespread use of these maximal (VO2peak, peak power output) and submaximal (lactate thresholds) parameters of aerobic fitness in the physiological assessments of off-road cyclists. Furthermore, our results suggest body size should be taken into account when evaluating such athletes.