Validity and reliability of a novel optoelectronic device to measure movement velocity,force and power during the back squat exercise

This study analysed the validity and reliability of a new optoelectronic device (Velowin) for the measurement of vertical displacement and velocity as well as to estimate force and mechanical power. Eleven trained males with Mean (SD) age = 27.4 (4.8) years, completed an incremental squat exercise test with 5 different loads (<30–90% of their 1?repetition maximum) while displacement and vertical velocity of the barbell were simultaneously measured using an integrated 3D system (3D motion capture system + force platform) and Velowin. Substantial to almost perfect correlation (concordance correlation coefficient = 0.75–0.96), root mean square error as coefficient of variation ±90% confidence interval ≤10% and good to excellent intraclass correlation coefficient = 0.84–0.99 were determined for all the variables. Passing and Bablock regression methods revealed no differences for average velocity. However, significant but consistent bias were determined for average or peak force and power while systematic and not proportional bias was found for displacement. In conclusion, Velowin, in holds of some potential advantages over traditionally used accelerometer or linear transducers, represents a valid and reliable alternative to monitor vertical displacement and velocity as well as to estimate average force and mechanical power during the squat exercise.     

Effect of different velocity loss thresholds during a power-oriented resistance training program on the mechanical capacities of lower-body muscles

This study compared the effects of two velocity loss thresholds during a power-oriented resistance training program on the mechanical capacities of lower-body muscles. Twenty men were counterbalanced in two groups (VL10 and VL20) based on their maximum power capacity. Both groups used the same exercises, relative intensity and repetition volume, only differing in the velocity loss threshold of each set (VL10: 10% vs. VL20: 20%). Pre- and post-training assessments included an incremental loading test and a 15-m linear sprint to assess the force- and load-velocity relationships and athletic performance variables, respectively. No significant between-group differences (P > 0.05) were observed for the force-velocity relationship parameters (ES range = 0.15–0.42), the MPV attained against different external loads (ES range = 0.02–0.18) or the 15-m sprint time (ES = 0.09). A high between-participants variability was reported for the number of repetitions completed in each training set (CV = 30.3% for VL10 and 29.4% for VL20). These results suggest that both velocity loss thresholds induce similar changes on the lower-body function. The high and variable number of repetitions completed may compromise the velocity-based approach for prescribing and monitoring the repetition volume during a power-oriented resistance training program conducted with the countermovement jump exercise.     

久蹲后快速与缓慢站立对脑血流速度的影响

为探讨久蹲(5min)后以较快和缓慢2种不同速度站立对脑血流速度的影响,应用CBS-II经颅多普勒诊断系统,分别在久蹲(5min)后即刻、久蹲后较快(1s)站立和久蹲后缓慢(3s)站立,即刻检测了20名男女受试者大脑中动脉的平均血流速度(MCAVmean)。结果:久蹲后较快站立MCAVmean由(49.67±5.36)cm·s-1下降至(32.67±5.27)cm·s-1(P<0.01),下降了34.23%;久蹲后缓慢站立MCAVmean由(49.32±5.62)cm·s-1下降至(42.84±5.56)cm·s-1(P<0.05),下降了14.01%。结果说明久蹲后较快和缓慢站立都能引起脑血流速度下降,但较快站立脑血流速度下降的辐度大于缓慢站立脑血流速度下降的幅度。     

Effects of different intensities of resistance training with equated volume load on muscle strength and hypertrophy

The present study investigated the effects of different intensities of resistance training (RT) on elbow flexion and leg press one-repetition maximum (1RM) and muscle cross-sectional area (CSA). Thirty men volunteered to participate in an RT programme, performed twice a week for 12 weeks. The study employed a within-subject design, in which one leg and arm trained at 20% 1RM (G20) and the contralateral limb was randomly assigned to one of the three conditions: 40% (G40); 60% (G60), and 80% 1RM (G80). The G20 started RT session with three sets to failure. After G20 training, the number of sets was adjusted for the other contralateral limb conditions with volume-matched. CSA and 1RM were assessed at pre, post-6 weeks, and post-12 weeks. There was time effect for CSA for the vastus lateralis (VL) (8.9%, 20.5%, 20.4%, and 19.5%) and elbow flexors (EF) (11.4%, 25.3%, 25.1%, and 25%) in G20, G40, G60, and G80, respectively (p?>?.05). G80 showed higher CSA than G20 for VL (19.5% vs. 8.9%) and EF (25% vs. 11.4%) at post-12 weeks (p?p?相似文献   

The influence of different footwear on 3-D kinematics and muscle activation during the barbell back squat in males

Abstract

The barbell back squat is commonly used by athletes participating in resistance training. The barbell squat is typically performed using standard athletic shoes, or specially designed weightlifting footwear, although there are now a large number of athletes who prefer to squat barefoot or in barefoot-inspired footwear. This study aimed to determine how these footwear influence 3-D kinematics and muscle activation potentials during the barbell back squat. Fourteen experienced male participants completed squats at 70% 1 rep max in each footwear condition. 3-D kinematics from the torso, hip, knee and ankle were measured using an eight-camera motion analysis system. In addition, electromyographical (EMG) measurements were obtained from the rectus femoris, tibialis anterior, gastrocnemius, erector spinae and biceps femoris muscles. EMG parameters and joint kinematics were compared between footwear using repeated-measures analyses of variance. Participants were also asked to subjectively rate which footwear they preferred when performing their squat lifts; this was examined a chi-squared test. The kinematic analysis indicated that, in comparison to barefoot the running shoe was associated with increased squat depth, knee flexion and rectus femoris activation. The chi-squared test was significant and showed that participants preferred to squat barefoot. This study supports anecdotal evidence of athletes who prefer to train barefoot or in barefoot-inspired footwear although no biomechanical evidence was found to support this notion.     

Effect of cadence on volume and myoelectric activity during agonist-antagonist paired sets (supersets) in the lower body

The aim of this study was to investigate the effect of cadence on volume load (VLoad) and muscle activity during agonist –antagonist paired sets (APS) in the lower body. Twelve trained men (24.0 ± 3.3 years; 78.3 ± 9.7 kg; 1.77 ± 0.58 m) volunteered to participate in this study. After the 10 maximum repetition test for leg extension and seated leg curl, participants performed three experimental protocols: first protocol (traditional)—three sets of only leg extension (60 bpm); second protocol (fast cadence)—three sets of leg extension, with each set preceded by one set on the seated leg curl with fast cadence (90 bpm); third protocol (slow cadence)—similar to the second, but seated leg curl with slow cadence (40 bpm). The total number of repetitions, VLoad and the electromyography activity for the vastus lateralis, vastus medialis and rectus femoris muscles were recorded. The VLoad was higher during APS than the traditional method, but the cadence (fast or slow) of antagonist exercise did not influence VLoad. Muscle activity of vastus lateralis was higher during traditional protocol; on the other hand, rectus femoris showed higher activity on APS fast cadence protocol, indicating that APS has a different influence on quadriceps components.     

Effects of rest interval during high-repetition resistance training on strength,aerobic fitness,and repeated-sprint ability

Abstract

The effect of altering the rest period on adaptations to high-repetition resistance training is not well known. Eighteen active females were matched according to leg strength and repeated-sprint ability and randomly allocated to one of two groups. One group performed resistance training with 20-s rest intervals between sets, while the other group employed 80-s rest intervals between sets. Both groups performed the same total training volume and load. Each group trained 3 days a week for 5 weeks [15- to 20-repetition maximum (RM), 2 – 5 sets]. Repeated-sprint ability (5×6-s maximal cycle sprints), 3-RM leg press strength, and anthropometry were determined before and after each training programme. There was a greater improvement in repeated-sprint ability after training with 20-s rest intervals (12.5%) than after training with 80-s rest intervals (5.4%) (P = 0.030). In contrast, there were greater improvements in strength after training with 80-s rest intervals (45.9%) than after training with 20-s rest intervals (19.6%) (P = 0.010). There were no changes in anthropometry for either group following training. These results suggest that when training volume and load are matched, despite a smaller increase in strength, 5 weeks of training with short rest periods results in greater improvements in repeated-sprint ability than the same training with long rest periods.     

不同负荷强度运动时表面肌电图中位频率与血乳酸浓度变化的关系

采用等速运动方式 ,以表面肌电图和血乳酸为指标 ,在 10 %、3 0 %和 50 %MVC三种负荷条件下 ,对肘关节屈伸运动时的肱三头肌、肱二头肌和前腕骨肌的表面肌电图和血乳酸浓度的变化进行了比较分析。结果表明 :(1)肘关节屈伸运动时 ,伸展运动的力矩峰值下降幅度大于屈曲运动。 (2 )以 3 0 %和 50 %MVC负荷强度运动时 ,出现了表面肌电图的MF值逐步下降和血乳酸浓度逐渐增加的现象 ;工作肌群MF下降幅度 ,由大到小依次为肱三头肌 >肱二头肌 >前腕骨肌。 (3 )肱三头肌、肱二头肌和前腕骨肌的表面肌电图的MF变化与血乳酸浓度变化相互比较 ,10 %、3 0 %和 50 %MVC三种运动形式都表现出了非常明显的相关性。实验结果可以说明 ,sEMG作为特异性良好的非损伤性检测手段 ,不但能够直观地反映肌肉的收缩活动 ,还与肌肉组织代谢变化有一定的相关关系     

Effect of loading on peak power of the bar,body, and system during power cleans,squats, and jump squats

Abstract

Nine males (age 24.7 ± 2.1 years, height 175.3 ± 5.5 cm, body mass 80.8 ± 7.2 kg, power clean 1-RM 97.1 ± 6.36 kg, squat 1-RM = 138.3 ± 20.9 kg) participated in this study. On day 1, the participants performed a one-repetition maximum (1-RM) in the power clean and the squat. On days 2, 3, and 4, participants performed the power clean, squat or jump squat. Loading for the power clean ranged from 30% to 90% of the participant's power clean 1-RM and loading for the squat and jump squat ranged from 0% to 90% of the participant's squat 1-RM, all at 10% increments. Peak force, velocity, and power were calculated for the bar, body, and system (bar + body) for all power clean, squat, and jump squat trials. Results indicate that peak power for the bar, body, and system is differentially affected by load and movement pattern. When using the power clean, squat or jump squat for training, the optimal load in each exercise may vary. Throwing athletes or weightlifters may be most concerned with bar power, but jumpers or sprinters may be more concerned with body or system power. Thus, the exercise type and load vary according to the desired stimulus.     

补醋对力竭运动后血乳酸、血氨、血气等指标的影响

目的探讨递增负荷运动至力竭后补充镇江香醋对消除疲劳及相关生化指标变化的影响.方法研究对象为18名日本国士馆大学体育学院在校优秀的男田径运动员,在不同时间(相隔1周)进行两次递增负荷运动,到力竭后即刻,分别补充蒸馏水和镇江香醋溶液,对两次实验进行自身对照.运动后补充蒸馏水为C组,运动后补镇江香醋稀释溶液为V组.并且测试运动员血乳酸、血氨浓度、血气等指标的变化情况.结果V组与C组在消除血乳酸速率、血液pH值和HCO3-浓度等指标上有显著差异(P＜0.05),清除血氨浓度的变化也存在显著差异(P＜0.05).结论外源性补充镇江香醋溶液可以加快运动后血乳酸的消除速率,提高血液缓冲能力,缓解体内代谢性酸中毒的发生,从而促进运动性疲劳的恢复.     

武术大负荷训练对民族传统体育大学生血乳酸和血尿素氮影响的研究

观察15名民族传统体育专业大学生在武术大负荷训练前后血乳酸和血尿素氮的变化,分析血乳酸和血尿素氮与民族传统体育大学生训练水平的关系,结果表明：血乳酸和血尿素氮能够客观评定训练强度,为科学训练提供依据;大运动负荷训练对学生血乳酸和血尿素氮变化有不同程度的影响,但存在个体差异。     

Effect of body composition on redox homeostasis at rest and in response to exercise: The case of underfat women

Underfat individuals have been neglected as a malnourished population in terms of redox homeostasis. The aim of the present study was to evaluate the effect of body composition on redox homeostasis at rest and in response to exercise. Underfat, lean and overfat women, classified according to their BMI and body fat percentage, participated in the study and were subjected to an acute session of eccentric exercise. With regard to muscle function and damage, a significant group × time interaction was found for range of motion (P < .01), isometric peak torque at 90° (P < .01), delayed onset muscle soreness (P < .01) and creatine kinase (P < .05), with the lean group generally exhibiting faster recovery compared to the underfat and overfat groups. With regard to redox homeostasis, a significant group × time interaction was found for F₂-isoprostanes, protein carbonyls and glutathione (P < .01 for all biomarkers), with the underfat and overfat groups exhibiting increased resting oxidative stress levels and lower exercise-induced reactive species production . In conclusively, our data underline the importance of normal body composition for redox homeostasis, since underfat and overfat women demonstrate a similar pattern of redox disturbances both at rest and in response to exercise.     

补充不同剂量支链氨基酸对运动大鼠下丘脑5-羟色胺及其前体的影响

观察补充支链氨基酸(BCAA)后大鼠力竭游泳运动恢复期下丘脑细胞外液BCAA、游离色氨酸(f-Trp)和5-羟色胺(5-HT)的变化,分析补充BCAA是否能够提高大鼠的运动能力,比较补充BCAA的效果,探索补充BCAA的最佳剂量。方法:将32只大鼠随机分为对照组、小剂量补充组[1.25g/(kg·BW-1)]、中剂量补充组[2.5g/kg·BW-1)]和大剂量补充组[5g/(kg·BW-1)],每组8只。BCAA补充方案为:每天上午补充一次,每周6次(周日暂停),持续6周。6周后,在大鼠进行力竭游泳运动前一天下午取大鼠尾血测试血氨。采用毛细管电泳-激光诱导荧光法检测大鼠下丘脑细胞外液BCAA、f-Trp和5-HT的浓度。结论:血氨随着BCAA补充剂量的增加而升高,小剂量补充BCAA对机体血氨的生成无影响;补充BCAA能提高大鼠力竭游泳运动能力,但并不随BCAA补充剂量的增加而提高;补充BCAA可能提高了血浆BCAA与f-Trp竞争通过血脑屏障的能力且具有推迟和减少脑5-HT生成的作用;小剂量[1.25g/(kg·BW-1)]补充BCAA对提高大鼠运动能力效果最佳。