Energy Balance & Body Composition Laboratory, Musculoskeletal Assessment Laboratory, Department of Kinesiology & Sport Management, Texas Tech University, Box 43011, Lubbock, TX 79409 USA.
J Int Soc Sports Nutr. 2017 Nov 28;14:46. doi: 10.1186/s12970-017-0203-x. eCollection 2017.
Pre-workout supplements purportedly enhance feelings of energy, reduce fatigue and improve exercise performance. The purpose of this study was to examine the performance effects of caffeinated and non-caffeinated multi-ingredient pre-workout supplements.
In a counterbalanced, double-blind, placebo-controlled design, eccentric and concentric force production during lower body resistance exercise on a mechanized squat device were assessed after supplement ingestion. Repetitions-in-reserve/RPE and subjective feelings of energy, focus and fatigue were also examined. Twenty-one resistance-trained adults (12 F, 9 M) completed three conditions in random order: caffeinated supplement, non-caffeinated supplement and placebo. Subjects were not informed of the presence of a placebo condition. Thirty minutes after supplement ingestion, a 3-repetition maximum test and 5 sets of 6 repetitions were completed using the squat device. Each repetition involved 4-s eccentric and concentric phases, and the force signal throughout each repetition was sampled from a load cell contained within the squat device. The scaled and filtered force signals were analyzed using customized software. Repeated measures analysis of variance and appropriate follow-up analyses were utilized to compare dependent variables, and relevant effect sizes (d) were calculated.
Supplement or placebo ingestion led to similar subjective responses ( > 0.05). Energy (+8 to 44%; d = 0.3 to 0.8) and focus (+8 to 25%; d = 0.3 to 0.5) were acutely increased by supplement or placebo ingestion and decreased as the exercise session progressed. Fatigue was acutely decreased by supplement or placebo ingestion (-7 to 38%; d = -0.1 to -0.6) and increased as the exercise session progressed. Eccentric and concentric forces were unimproved by supplementation during the exercise sets for both sexes. In the non-caffeinated supplement condition only, maximal eccentric force production was lower during sets 3 to 5, as compared to set 1 ( < 0.05). Effect size data indicated that both the caffeinated and non-caffeinated supplements may contribute to small increases in concentric force production in males (+5 to 20%, d = 0.2 to 0.4 relative to placebo), but not females.
As compared to placebo, caffeinated and non-caffeinated multi-ingredient pre-workout supplements failed to improve concentric and eccentric force production. In males, effect size data indicate a possible small benefit of supplementation on concentric force production, although this was not statistically significant. When resistance-trained subjects were unaware of the presence of a placebo, resistance exercise performance was similar regardless of whether a placebo or multi-ingredient supplement was ingested.
据称，健身前补剂能增强活力、减轻疲劳并改善运动表现。本研究旨在检验含咖啡因和不含咖啡因的多成分健身前补剂对运动表现的影响。
在一项均衡、双盲、安慰剂对照设计中，在机械深蹲器上进行下肢抗阻运动后，评估了摄入补剂后的离心和向心力量产生情况。还检查了储备重复次数/RPE 和主观的能量、专注和疲劳感。21 名接受过抗阻训练的成年人（12 名女性，9 名男性）以随机顺序完成了三种条件：含咖啡因的补剂、不含咖啡因的补剂和安慰剂。受试者不知道存在安慰剂条件。摄入补剂 30 分钟后，使用深蹲器完成 3 次重复最大测试和 5 组 6 次重复。每次重复涉及 4 秒的离心和向心阶段，并且通过深蹲器内的称重传感器对每个重复的力信号进行采样。经缩放和滤波后的力信号使用定制软件进行分析。采用重复测量方差分析和适当的后续分析来比较因变量，计算了相关的效应量（d）。
摄入补剂或安慰剂导致类似的主观反应（ > 0.05）。摄入补剂或安慰剂可使能量（增加 8%至 44%；d 值为 0.3 至 0.8）和专注度（增加 8%至 25%；d 值为 0.3 至 0.5）急性增加，并随着运动过程的进展而降低。疲劳感可因摄入补剂或安慰剂而急性降低（减少 7%至 38%；d 值为-0.1 至-0.6），并随着运动过程的进展而增加。对于两性，补充剂在运动组中都没有改善离心和向心力量。仅在非咖啡因补充剂条件下，与第 1 组相比，第 3 至 5 组的最大离心力产生降低（ < 0.05）。效应量数据表明，咖啡因和非咖啡因的补剂可能都会使男性的向心力量产生小幅度增加（增加 5%至 20%，相对于安慰剂，d 值为 0.2 至 0.4），但不会增加女性的力量。
与安慰剂相比，含咖啡因和不含咖啡因的多成分健身前补剂都不能改善向心和离心力量产生。在男性中，效应量数据表明补充剂可能对向心力量产生有较小的好处，但没有达到统计学意义。当接受过抗阻训练的受试者不知道存在安慰剂时，摄入安慰剂或多成分补剂对运动表现没有影响。
