排序方式： 共有25条查询结果，搜索用时 484 毫秒
21.
《European Journal of Sport Science》2013,13(1):49-56
Abstract The effects of exercise training on heart have been widely explored. However, less understood are the effects of dehydration and rehydration on electrocardiographic (ECG) and echocardiographic (Echo) parameters in wrestlers. The aim of this study was to determine the effect of dehydration and rehydration on some ECG and Echo parameters. Fourteen healthy high school wrestlers (age 18.1±2.6 years, weight 77.2±10.2 kg, BMI 25.2±2.9 kg · m?2; mean±s) were randomly assigned to an experimental (loss of 3–4% of their weight through 10-min bouts in dry sauna) or a control (dry sauna exposure with mineral water proportionate to their body weight loss) group. Blood and urine sampling, 12-lead ECG, and echocardiogram were recorded in euhydration, dehydration, and 18 h after sauna. Moreover, a 6-min high-intensity arm ergometer cranking test (8×15 s intervals at maximum workload and 30 s active recovery) was completed in each of the three stages. Data were analysed with repeated-measures analysis of variance, independent t-tests, and Pearson correlations. Dehydration by 3–4% of body weight in sauna resulted in augmentation of the sum of amplitudes of P waves and QRS complexes (mm), but decreased left ventricular end-systolic volume (LVESV), left ventricular end-diastolic volume (LVEDV), and stroke volume (ml). As expected, rehydration was associated with recovery of the P wave and ECG parameters. In general, QRS amplitude correlated poorly with LVESV, LVEDV, and P wave, but was inversely related to stroke volume (r=–0.387, P=0.011). In conclusion, dehydration in Greco-Roman wrestlers results in physiological alterations (amplitude of the P wave and QRS complex, LVESV, LVEDV, and stroke volume) of the electrical properties of the passive volume conductor. Further research is necessary to assess the potential for adverse events and appropriateness of this short-term weight loss strategy for young wrestlers or other populations. 相似文献
22.
Yukio Fujita Keisuke Koizumi Saori Sukeno Motomu Manabe Jun Nomura 《Journal of sports sciences》2013,31(11):1145-1151
Abstract The effects of active recovery using previously active and inactive muscle groups on power output and respiratory responses were examined. Ten male volunteers underwent two exhaustive 40-s bouts of leg cycling (1st Ex and 2nd Ex), separated by a 20-min recovery period. The recovery conditions were leg (Leg-Active) or arm (Arm-Active) cranking at 50% ventilatory threshold (VT), or sedentary control (Passive). The total output work (Total work) during the 2nd Ex in the Leg-Active condition was significantly higher than that in the Passive (299 vs. 282 J · kg body mass?1 (J · BM?1)). The values of Total work, peak [Vdot]O2 and peak heart rate during the 2nd Ex were significantly higher than those during the 1st Ex in both Leg- and Arm-Active. Total CO2excess after the 1st Ex was significantly higher than that after the 2nd Ex (67.6 vs. 26.0 ml · BM?1) in Passive. After the 2nd Ex, the Total CO2excess in the Leg-Active (51.5 ml · BM?1) was significantly higher than that in both the Passive (26.0) and Arm-Active (36.5), with Arm-Active being significantly higher than Passive. The recovery exercise using previously inactive muscles improved respiratory compensation ability related to performance enhancement. 相似文献
23.
Abstract This investigation was conducted to compare the influence of high and low perceived competence (PC) and various causal dimension orientations on expectations, persistence, and performance while perceiving failure on a motor task. Based on a response to a PC scale, 84 junior high school students were selected to participate in this study. Separately, 42 low and 42 high PC subjects were oriented to perceive their performance on a stabilometer balancing task as due to: (a) internal, controllable, unstable factors (ICU); (b) internal, uncontrollable, stable factors (IUS); or (c) nothing in particular (NDO). Subjects then received fictitious negative feedback over 15 trials. Results revealed that persistence, expectations, and performance dependent measures were significant for PC and Causal Dimension groups. More specifically, the High PC group persisted longer, had higher expectations, and performed significantly better than the Low PC group. Furthermore, the subjects presented ICU orientations persisted for a longer amount of time, revealed higher expectations over trials, and performed significantly better over trials than the subjects in the IUS and NDO groups. These findings suggest that perceived competence and causal dimensional orientations influence children's expectations, persistence, and performance when perceiving failure on a motor task. 相似文献
24.
Christof A. Leicht Aris Papanagopoulos Sam Haghighat Steve H. Faulkner 《Journal of sports sciences》2017,35(17):1752-1758
Plasma heat shock protein 70 (HSP70) concentrations rise during heat stress, which can independently induce cytokine production. Upper body exercise normally results in modest body temperature elevations. The aim of this study was to investigate the impacts of additional clothing on the body temperature, cytokine and HSP70 responses during this exercise modality. Thirteen males performed 45-min constant-load arm cranking at 63% maximum aerobic power (62 ± 7%V?O2peak) in either a non-permeable whole-body suit (intervention, INT) or shorts and T-shirt (control, CON). Exercise resulted in a significant increase of IL-6 and IL-1ra plasma concentrations (P < 0.001), with no difference between conditions (P > 0.19). The increase in HSP70 from pre to post was only significant for INT (0.12 ± 0.11ng?mL?1, P < 0.01 vs. 0.04 ± 0.18 ng?mL?1, P = 0.77). Immediately following exercise, Tcore was elevated by 0.46 ± 0.29 (INT) and 0.37 ± 0.23ºC (CON), respectively (P < 0.01), with no difference between conditions (P = 0.16). The rise in mean Tskin (2.88 ± 0.50 and 0.30 ± 0.89ºC, respectively) and maximum heat storage (3.24 ± 1.08 and 1.20 ± 1.04 J?g?1, respectively) was higher during INT (P < 0.01). Despite large differences in heat storage between conditions, the HSP70 elevations during INT, even though significant, were very modest. Possibly, the Tcore elevations were too low to induce a more pronounced HSP70 response to ultimately affect cytokine production. 相似文献
25.
目的:探讨手臂摆动对人体行走步态特征的影响,从而为无臂的仿人机器人以及假肢的设计提供理论支持. 方法:选用10名青年男性大学生为受试者,以1. 5 ± 0. 3m/s的速度完成手臂自然摆动和限制双臂摆动的行走运动,研究采用Kistler三维测力台、Motion红外高速运动捕捉系统同步采集受试者行走时动力学和运动学数据. 结果:(1)限制摆臂会显著降低步行频率;(2)限制摆臂会显著增大步行时重心的上下摆动、减少骨盆的旋转角度;(3)踝关节的生物力学参数在两种不同运动状态下表现出显著性差异,不摆臂时踝关节屈伸角度增大、屈伸力矩增大、关节做功增大;同时,不摆臂会造成膝伸力矩显著性增大,做功增多;针对髋关节,不摆臂会造成髋关节的屈伸角度增大;(4)下肢各参数在两种走路模式上表现出高度的相关性. 结论:步行中手臂自然摆动可以降低腿部的能量消耗,是节省能量的一种行走模式;摆臂与不摆臂两种行走状态下肢的运动模式在不同水平上高度一致. 相似文献