Acute caffeine ingestion enhances strength performance and reduces perceived exertion and muscle pain perception during resistance exercise

Abstract

The efficacy of caffeine ingestion in enhancing aerobic performance is well established. However, despite suggestions that caffeine may enhance resistance exercise performance, research is equivocal on the effect of acute caffeine ingestion on resistance exercise performance. It has also been suggested that dampened perception of perceived exertion and pain perception might be an explanation for any possible enhancement of resistance exercise performance due to caffeine ingestion. Therefore, the aim of this study was to examine the acute effect of caffeine ingestion on repetitions to failure, rating of perceived exertion (RPE) and muscle pain perception during resistance exercise to failure. Eleven resistance trained individuals (9 males, 2 females, mean age±SD=26.4±6.4 years), took part in this double-blind, randomised cross-over experimental study whereby they ingested a caffeinated (5 mg kg^?1) or placebo solution 60 minutes before completing a bout of resistance exercise. Experimental conditions were separated by at least 48 hours. Resistance exercise sessions consisted of bench press, deadlift, prone row and back squat exercise to failure at an intensity of 60% 1 repetition maximum. Results indicated that participants completed significantly greater repetitions to failure, irrespective of exercise, in the presence of caffeine (p=0.0001). Mean±S.D of repetitions to failure was 19.6±3.7 and 18.5±4.1 in caffeine and placebo conditions, respectively. There were no differences in peak heart rate or peak blood lactate values across conditions (both p >0.05). RPE was significantly lower in the caffeine compared to the placebo condition (p=0.03) and was significantly higher during lower body exercises compared to upper body exercises irrespective of substance ingested (p=0.0001). For muscle pain perception, a significant condition by exercise interaction (p=0.027) revealed that muscle pain perception was lower in the caffeine condition, irrespective of exercise. With caffeine, pain perception was significantly higher in the deadlift and back squat compared to the bench press. However, with placebo, pain perception was significantly higher for the deadlift and back squat compared to the prone row only. Therefore, acute caffeine ingestion not only enhances resistance exercise performance to failure but also reduces perception of exertion and muscle pain.     

The effect of breast support and breast pain on upper-extremity kinematics during running: implications for females with large breasts

The relationship between inappropriate breast support and upper-extremity kinematics for female runners is unclear. The purpose of this study was to investigate the effect of breast support and breast pain on upper-extremity kinematics during running. Eleven female recreational runners with larger breasts (UK D and E cup) completed a 7 min 20 s treadmill run (2.58 m · s^?1) in a high and low breast support condition. Multi-planar breast and upper-extremity kinematic data were captured in each breast support condition by eight infrared cameras for 30 s towards the end of the run. Breast pain was rated at the end of each treadmill run using a numeric analogue scale. The high support bra reduced breast kinematics and decreased breast pain (P < 0.05). Upper-extremity kinematics did not differ between breast support conditions (P > 0.05), although some moderate positive correlations were found between thorax range of motion and breast kinematics (r = 0.54 to 0.73). Thorax and arm kinematics do not appear to be influenced by breast support level in female runners with large breasts. A high support bra that offers good multi-planar breast support is recommended for female runners with larger breasts to reduce breast pain.     

慢性下腰痛患者腰部表面肌电信号的变化特征

在中等强度动态等惯性力运动负荷条件下采集腰部L3-L4和L5-S1部位的sEMG信号，采用快速傅立叶变换和定量递归分析与复杂度计算等方法分析研究sEMG信号变化特征，采用主动康复治疗手段观察其对腰部肌肉功能的影响。结果表明：采样部位对各项sEMG分析指标以及被试分组对AEMG的作用无明显统计学意义，而采样时间对各项sEMG分析指标以及被试分组对其它sEMG分析指标的影响均有明显统计学意义。慢性下腰痛患者的sEMG信号具有低频、不复杂和有序的信号特征，主动康复治疗对改善腰部肌肉功能具有明显的作用。     

伦理行为类型学说（上）——《新伦理学》研究（9）

“伦理行为”是伦理学的核心概念,它关联起一切形态的道德规范与美德要求,因而它异常复杂。“伦理行为”的复杂性表现在它既要把伦理动机与伦理目的联系起来,又要把情感与理性纠结在一起;更重要的是,它还要以利益为原动力,把人的需要、欲望带入其中,并对人性予以审查与拷问。正是由于这种复杂性,使《新伦理学》对伦理行为类型学说的探讨与构建,仍然仅滞留于意识的表层而未能达向深度拷问。《新伦理学》的这种局限,构成了伦理行为类型学说之基本思想探讨的真正起点,以此为步,对伦理行为问题予以深度检讨,揭示了伦理学它那空阔深幽的人性化的情意世界。     

Influence of moderate intensity physical activity levels and gender on conditioned pain modulation

This study examined the potential influence of moderate intensity physical activity (PA) levels and gender on central pain modulation using conditioned pain modulation (CPM) in healthy men and women. Twenty four individuals (12 men and 12 women) who reported engaging in the moderate intensity PA for 150 min or more per week and 24 individuals (12 men and 12 women) who reported engaging in moderate intensity PA for 60 min or less per week completed a self-report PA questionnaire and a 7-day PA assessment using an accelerometer. Furthermore, the participants completed the CPM testing to evaluate the efficiency of central pain modulation. The active individuals scored higher on the PA questionnaire and spent more minutes for light, lifestyle, moderate and vigorous intensity PA than the less active individuals. The active men and women exhibited comparable magnitudes of CPM, and showed a greater magnitude of CPM when compared to their less active counterparts. However, these beneficial effects of higher dose moderate intensity PA disappeared when time spent for vigorous intensity PA was statistically controlled for. These results suggest that the higher dose moderate intensity PA does not add to the benefits from vigorous intensity PA to further improve central pain modulatory systems.     

心理渐进放松对延迟性肌肉酸痛及血乳酸指标的影响

心理渐进放松法是为了缓解精神紧张与焦虑而设计的精神放松方法。基于身体与精神活动存在紧密的相互影响关系的理论,本研究将心理渐进放松法运用于力量训练后的肌肉放松。以某高校12名男生为被试,经随机分组,以训练后的肌肉酸痛4级评价法和血乳酸测试为主要指标监测法进行对照实验。结果发现,心理渐进放松法对缓解延迟性肌肉酸痛有着明显的效果,而且对训练后血乳酸的恢复也具有积极的促进作用。     

鼠蹊部的形态结构基础及其与疼痛产生的关系

通过尸体解剖观察和资料搜集的方法，研究了鼠蹊部的形态结构特征，用“四点、两缘、两隙”加以描述。并对其在运动中产生疼痛的原因进行了分析，认为运动中由肌肉主动发力所完成的运作、肌肉被动拉长的运作，韧带牵拉等动作都会使鼠蹊部的结构受到牵拉产生疼痛。为临床认识鼠蹊部疼痛提供了理论依据。     

沉痛的逍遥:论庄子的精神世界

庄子学术本以讲明"无为"的政治理想为主旨,但残酷的政治现实促成其重心偏移至个人的安心立命之道,追求个体的精神自由,以获得自我超越与解脱。当知识分子的良知与道义感驱使庄子重新试图以自己的政治理想去干预现实政治时,现实却再次幻灭了他心中的理想。于是,庄子重又别无选择地逃返内心深处,作无奈而沉痛的逍遥游。庄子的一生是在理想与现实、入世与出世的矛盾与冲突中反复挣扎、徘徊、犹豫乃至于迷惑不已、痛苦不堪的一生。     

“孤独”“痛苦”和“恐惧”——史铁生生命体验散文的三重主题

上帝在给予史铁生苦难的同时,也给予了他独特的感觉与独特的体悟,面对人生三大困境——孤独、痛苦、恐惧,他以自己残缺的身体,在生命体验散文中展现了最为健全而丰满的思想,让我们感受到了来自心灵最深处的颤抖。他用笔实现了自我的超越,为自己闯开了一条生命永恒之路。