Instructions to Adopt an External Focus Enhance Muscular Endurance

Abstract

The influence of internal (movement focus) and external (outcome focus) attentional-focusing instructions on muscular endurance were investigated using three exercise protocols with experienced exercisers. Twenty-three participants completed a maximal repetition, assisted bench-press test on a Smith's machine. An external focus of attention resulted in significant (p < .05) improvements in performance compared to the internal focus of attention, but not the control condition. Seventeen participants completed repetitions to failure at 75% 1-RM on free bench-press and squat exercises. In both tasks, externally focused instructions resulted in significantly greater repetitions to failure than control and internal focus conditions (p < .05). These results support previous research showing beneficial effects of externally focused instructions on movement efficiency.     

Using Principal Components Analysis to Identify Individual Differences in Vertical Jump Performance

Purpose: The purpose of this study was to determine the reliability of cardiorespiratory and pelvic kinematic responses to simulated horseback riding (SHBR) and to characterize responses to SHBR relative to walking in apparently healthy children. Method: Fifteen healthy children (M_age = 9.5 ± 2.6 years) completed SHBR on a commercially available simulator at low intensity (0.27 Hz) and high intensity (0.65 Hz) during 3 sessions on different occasions. Heart rate (HR), blood pressure, and respiratory gases were measured at rest and during steady-state exercise at both intensities. Pelvic displacement was measured during steady-state exercise. Rate of energy expenditure, mean arterial pressure, and rate pressure product (RPP) were calculated. Participants also walked on a treadmill for 26.8 m/min to 80.5 m/min in 13.4-m/min increments at 0% grade during 1 session to compare cardiorespiratory responses with those of SHBR. Results: Physiological variables across all 3 SHBR sessions were similar at both intensities (p>.05 for all). Intraclass correlation coefficients (ICCs) and coefficients of variation indicate good to modest reliability of cardiorespiratory measures during SHBR (ICCs = .542–.996 for oxygen consumption, energy expenditure, and RPP). Cardiorespiratory variables, except for HR, were 2% to 19% greater, and pelvic displacement was up to 37% greater with high-intensity riding. Treadmill walking at all speeds elicited greater physiological responses compared with SHBR (p < .05). Conclusion: Cardiorespiratory responses and pelvic kinematics are reproducible with SHBR in young children, and these responses were lower than those elicited by slow treadmill walking.     

负重深蹲与保加利亚蹲对冰球运动员专项移动能力影响的实验研究

目的：探讨负重深蹲练习与保加利亚蹲练习两种不同的下肢力量训练方式对冰球运动员专项移动能力的影响,并比较两种训练方式对提升冰球运动员滑行能力的差异。方法：将18名U16冰球运动员随机分为保加利亚蹲组和负重深蹲组,对其训练前后冰上30米滑行、冰上重复冲刺、8字滑行以及陆地30米跑、立定三级跳、侧跨跳、Y-Balance成绩变化进行测试。结果：两种下肢力量训练方式均可提高冰球运动员的冰上滑行能力、下肢爆发力及下肢平衡能力。在冰上滑行能力方面,保加利亚蹲组冰上重复冲刺能力提高优于负重深蹲组,具有显著性差异,冰上8字滑行速度两组间不存在显著性差异;在下肢爆发力方面,保加利亚蹲组30米冲刺跑成绩显著优于负重深蹲组。在下肢Y-Balance测试方面,两组不具有显著性差异。结论：保加利亚蹲与负重深蹲练习均可以显著提高男子U16冰球运动员的直线加速滑行能力,前者在提高重复冲刺能力方面显著优于手者,两种练习均可以提升男子U16冰球运动员的下肢爆发力与平衡能力。     

下蹲式抓举技术动作的力学原理与解剖学分析

文章从力学和解剖学的角度对下蹲式抓举技术动作进行分析,阐明抓举技术动作的一般原理和内在规律,从而得出改进技术动作方法的理论依据。     

短跑道速度滑冰运动员坡路训练方法

目的:探究坡路训练方法对短跑道速度滑冰运动员速度与速度耐力素质的影响;方法:采用坡路(坡度15°左右)进行快速屈膝走,利用血乳酸作为强度监控指标进行无氧耐力速度训练;结果:坡路训练方法,坡度15°~20°为宜,长度150~200m为完成有效负荷的距离,血乳酸达到10mmol/L为有效强度;结论:坡路训练是改善短道速滑运动员骨胳肌代谢水平,提高其乳酸生成能力与发展快速蹬冰力量的有效手段。     

优秀男子举重运动员成功与失败抓举技术的对比研究

运用三维运动学的研究方法,对我国9名举重国际健将比赛条件下抓举同等杠铃重量时成功与失败的18次试举技术进行对比研究,探讨优秀运动员特定负荷下成功试举与失败试举技术特点及差异。研究结果表明,从动作的时空特征来看成功试举与失败试举间不具有显著性差异,成功试举与失败试举伸膝提铃阶段合加速度矢量方向具有显著性差异,成功试举时提铃用力较均匀,而失败试举时运动员对杠铃不稳定作用力的方向是造成试举失败的主要原因。     

不同力量训练即刻下肢CMJ纵跳能力变化的研究

设计了静蹲训练与静蹲施加振动干预训练两种训练方式,分别在30 s、45 s和60 s训练时间后即刻测试CMJ纵跳水平,并与未进行该实验前初始水平进行比较分析,以及对实验组之间进行对比分析,以研究在静蹲训练中施加振动干预后即刻下肢CMJ纵跳能力的变化。     

Kinematic and neuromuscular relationships between lower extremity clinical movement assessments*

Lower extremity injuries have immediate and long-term consequences. Lower extremity movement assessments can assist with identifying individuals at greater injury risk and guide injury prevention interventions. Movement assessments identify similar movement characteristics and evidence suggests large magnitude kinematic relationships exist between movement patterns observed across assessments; however, the magnitude of the relationships for electromyographic (EMG) measures across movement assessments remains largely unknown. This study examined relationships between lower extremity kinematic and EMG measures during jump landings and single leg squats. Lower extremity three-dimensional kinematic and EMG data were sampled from healthy adults (males = 20, females = 20) during the movement assessments. Pearson correlations examined the relationships of the kinematic and EMG measures and paired samples t-tests compared mean kinematic and EMG measures between the assessments. Overall, significant moderate correlations were observed for lower extremity kinematic (r_avg = 0.41, r_range = 0.10–0.61) and EMG (r_avg = 0.47, r_range = 0.32–0.80) measures across assessments. Kinematic and EMG measures were greater during the jump landings. Jump landings and single leg squats place different demands on the body and necessitate different kinematic and EMG patterns, such that these measures are not highly correlated between assessments. Clinicians should, therefore, use multiple assessments to identify aberrant movement and neuromuscular control patterns so that comprehensive interventions can be implemented.     

激活后增强效应的间歇时间对下蹲跳高度影响的Meta分析

目的：探究激活后增强效应（PAP）间歇时间对下蹲跳高度影响。方法：检索PubMed等数据库,查找相关随机对照试验,检索时间从建库至2017年11月30日。按纳入与排除标准筛选文献、提取数据和评价纳入文献研究方法质量后,采用Review Manager 5.3软件进行Meta分析。结果：共纳入15篇文献286名受试者。Meta分析结果显示：间歇时间为0~3 min[MD=-1.46,95% CI（-2.15,-0.78）,P<0.000 1],实验组优于对照组;间歇时间为4~7 min[MD=1.90,95% CI（0.81,2.99）,P=0.000 6]和8~12 min[MD=1.46,95% CI（0.78,2.15）,P<0.000 1],对照组优于实验组;间歇时间为13 min以上[MD=-0.45,95% CI（-2.26,1.36）,P=0.62],对照组与实验组间的差异无统计学意义。敏感性分析提示：改变研究质量差异、纳入标准、统计模型以及效应量的选择等,发现合并结果改变不明显,且受异质性影响的可能较小。结论：诱导方式为杠铃深蹲,诱导强度在85%~93% 1RM之间,重复次数为5~10次,可诱导产生PAP。间歇时间为0~3 min,可以明显提高受试者下蹲跳高度,间歇时间为4~7 min和8~12 min时下蹲跳高度未能显著增加,间歇时间为13min以上时,仍需更多高质量随机对照试验进一步研究证实。在制定诱导PAP方案时,还需考虑诱导对象的年龄与性别、训练经历和力量水平对PAP的影响。     

Letter to the editor concerning the article “Bar velocities capable of optimising the muscle power in strength-power exercises” by Loturco,Pereira, Abad,Tabares, Moraes,Kobal, Kitamura & Nakamura (2017)

Loturco and co-workers (2017) recently published data in the Journal of Sports Sciences to present the optimum loading magnitudes regarding the maximization of the “mean propulsive power” of the leg and arm muscles. Among the most important findings were that (1) the recorded power in the squat and squat jump exercises was markedly low, (2) the optimum external load that maximized the power in the same exercises was close to 100% of body weight, while (3) the ballistic bench press throw revealed smaller power than the regular bench press typically performed with relatively low level of muscle activation towards the end of the propulsive lifting phase. The findings are either counter-intuitive, or contradict the literature findings, or both, and we believe that they originate from apparent methodological flaws. The first one is neglecting the force acting against the body segments moved together with the external load that is particularly high in squat exercises. The second one is an erroneous calculation of the propulsive phase that included a part of the bar’s flight time. Both of these methodological flaws are frequent in the literature and could be associated with the improper use and calculation of variables when utilizing linear position transducers.