Inter-individual variability at a global level.

BackgroundThe extent of inter-individual variability in response to heavy resistance exercise training (HReT), and the possible existence of non-responders, remains unclear. This study aimed to determine the degree of variability in response to prolonged HReT in healthy older men.MethodsWe conducted a secondary analysis of an 8- and 16-week intervention involving thrice-weekly HReT (EX) or continuation of a sedentary lifestyle (SED). Fifty-eight healthy men (age 72 ± 5) were randomized to EX (n = 38) or SED (n = 20). Assessments were conducted at baseline, 8-weeks, and 16-weeks for five outcomes: maximal voluntary contraction strength (MVC), rate of force development (RFD), quadriceps cross-sectional area (qCSA), and type I and II myofibre cross-sectional area (fCSA). Inter-individual variability was assessed using the standard deviation of individual responses (SDIR). Individual changes relative to a Typical Error were used to classify responders as Poor, Trivial, Robust, or Excellent.Results16 weeks of EX led to group-level increases in MVC (19 ± 14%), RFD (58 ± 80%), qCSA (3 ± 4%), and type II fCSA (14 ± 25%), with no changes in SED. Substantial inter-individual variability was observed. After 16 weeks, 82% of EX participants were classified as Robust or Excellent responders; only 5% were Poor responders. Training compliance and 1RM progression did not explain this variability. Lower baseline levels were linked to greater improvements but did not fully account for response differences.ConclusionsThis study provides strong evidence of inter-individual variability in response to HReT among healthy older men. Given the rarity of true non-responders, our data support HReT as the universally recommended first-line strategy for enhancing muscle mass and strength.

研究背景：个体对大强度抗阻训练（Heavy Resistance Exercise Training, HReT）的响应存在个体差异的程度，以及无响应者是否真实存在，目前仍不明确。本研究旨在明确健康老年男性接受长期大强度抗阻训练后的响应差异程度。

研究方法：本研究对一项为期8周、16周的干预试验进行二次分析，试验将受试者分为每周进行3次大强度抗阻训练组（EX）与维持久坐生活方式组（SED）。共纳入58名健康男性（年龄72±5岁），采用随机分组方式将其分配至EX组（n=38）与SED组（n=20）。研究分别在基线、8周、16周时对5项结局指标进行评估：最大自主收缩力量（maximal voluntary contraction strength, MVC）、力量发展速率（rate of force development, RFD）、股四头肌横截面积（quadriceps cross-sectional area, qCSA）以及I型与II型肌纤维横截面积（type I and II myofibre cross-sectional area, fCSA）。本研究采用个体响应标准差（standard deviation of individual responses, SDIR）评估个体间响应差异，并基于个体变化值与典型误差的比值，将受试者的训练响应划分为较差、微小、良好与优秀四个等级。

研究结果：干预16周后，EX组受试者的MVC提升19%±14%、RFD提升58%±80%、qCSA提升3%±4%、II型肌纤维fCSA提升14%±25%；SED组各项指标均无显著变化。本研究观察到显著的个体间响应差异。干预16周后，EX组中有82%的受试者被划分为良好或优秀响应者，仅5%为较差响应者。训练依从性与单次最大重复重量（1RM）的提升幅度均无法解释该个体差异。基线指标水平较低与训练后更大的提升幅度相关，但无法完全解释响应程度的个体差异。

研究结论：本研究为健康老年男性在大强度抗阻训练中的响应存在个体差异提供了有力证据。鉴于真正意义上的无响应者极为罕见，本研究数据支持将大强度抗阻训练作为提升肌肉量与肌肉力量的通用推荐一线干预策略。