Resistance training (RT) is recommended to counteract the deleterious effects of sarcopenia on muscle mass and function.^1-3 The evidence about optimal RT scheme (training intensity, volume, rest, and so on) for optimal muscle outcomes in older individuals with and without sarcopenia as assessed by novel and recently recommended measurement techniques (magnetic resonance imaging, computed tomography, bioimpedance, dual-energy X-ray absorptiometry)^{1, 2} remains limited.

We therefore read with great interest the recent paper in the journal by Otsuka and colleagues,⁴ which evaluated the effects of different RT protocols (low-load (LL-) RT and moderate load (ML-) RT) versus control on muscle quantity, quality and strength in healthy older adults. After 24 weeks of the intervention, a significant increase in cross-sectional area of lower limb muscles in RT groups, and a significant improvement in some bioimpedance parameters (phase angle and membrane capacitance) in ML-RT group was demonstrated. While both RT groups were superior to control group in improvement of cross-sectional area of lower limb muscle and phase angle at 12 and 24 weeks, there was no significant difference between RT groups in muscle quantity and quality.⁴ Despite novel findings on muscle mass and quality, the study RT protocol needs some attention. In contrast to recent RT guidelines in healthy older adults,³ the authors compared only the effects of LL-RT [40% of one repetition maximum (1-RM)] and ML-RT (60% of 1-RM)⁴; both of them may present a suboptimal stimulus to induce muscle hypertrophy and strength gains.^{3, 5} Current recommendations are also supported by the previous two meta-analysis showing the safety and superiority of high-load (HL-RT) over ML-RT and LL-RT on muscle strength, and similar effects on muscle hypertrophy in healthy young and older adults.^{6, 7} Furthermore, the cumulative training load should have been balanced between LL-RT and ML-RT groups by a number of repetitions (both RT groups performed three sets of 14 repetitions). In addition, the repetition range at a given RT load was suboptimal, as RT recommendations suggest the use of more than 15 repetitions/set when exercising at the intensities lower than 65% of 1-RM.⁸

We believe that the study protocol as designed was suboptimal for potential muscle outcomes and may largely explain the lack of difference between RT groups for most of muscle hypertrophy measures as well as maximal muscle strength. What the authors do not report but it would be interesting to know is whether there was a difference in improvement of 1-RM between each RT group and control group, similar as they reported for muscle quality and quantity outcomes.

As the sarcopenia trajectory severely affects muscle mass and function, it is important to use optimal RT to counteract such changes. The excellent study by Otsuka et al.⁴ has demonstrated novel insights in the dose-dependent relationship between RT load and changes in muscle hypertrophy and strength. While there is a mounting evidence that muscle atrophy can be attenuated using variety of RT intensities (from LL to HL),^{6, 7} clinicians should also be aware on its negative impact of muscle function. With ageing, the loss of muscle mass is closely related to muscle denervation and a decrease in circulating anabolic hormones (e.g. growth hormone, insulin-like growth factors I and II),^{1, 9, 10} which may be counteracted by the use of HL-RT, especially given its superiority over LL-RT in improvement of maximal muscle strength and activation.^{3, 6, 7} Additionally, the recent studies and guidelines in chronic disease patients (such as cancer,^{11, 12} coronary artery disease,¹³ chronic kidney disease,^14-16 chronic pulmonary disease¹⁷) with higher risk of sarcopenia² have replaced LL-RT with progressive ML-to-HL-RT or solely HL-RT. Currently, cumulating evidence demonstrates beneficial effects of ML-RT and HL-RT on muscle hypertrophy and muscle strength compared with standard care or even with aerobic training alone.

We therefore are proponents to include HL-RT as a core component in primary and secondary prevention of sarcopenia in older adults and patients. Further research should primarily focus on the safety, feasibility and efficacy of HL-RT compared with other RT modalities in terms of maximal muscle strength and activation, anabolic hormone signalling pathways, and muscle quality and quantity in sarcopenic and/or cachectic patients.

建议进行阻力训练 (RT) 以抵消少肌症对肌肉质量和功能的有害影响。^1-3通过新的和最近推荐的测量技术（磁共振成像、计算机断层扫描、生物阻抗）评估有和没有肌肉减少症的老年人最佳肌肉结果的最佳 RT 方案（训练强度、训练量、休息等）的证据, 双能 X 射线骨密度仪) ^{1, 2}仍然有限。

因此，我们非常感兴趣地阅读了 Otsuka 及其同事最近在期刊上发表的论文⁴，该论文评估了不同 RT 方案（低负荷 (LL-) RT 和中负荷 (ML-) RT）与肌肉量控制的效果，健康老年人的质量和力量。干预24周后，RT组下肢肌肉横截面积显着增加，ML-RT组一些生物阻抗参数（相位角和膜电容）显着改善。12周和24周时两组RT组下肢肌肉横截面积和相位角的改善均优于对照组，但RT组肌肉数量和质量无显着差异。⁴尽管关于肌肉质量和质量的新发现，研究 RT 协议需要一些关注。与最近针对健康老年人的 RT 指南相比，³作者仅比较了 LL-RT [一次最大重复次数的 40% (1-RM)] 和 ML-RT (1-RM 的 60%) ⁴的效果；它们都可能呈现次优刺激来诱导肌肉肥大和力量增加。^{3, 5}前两项荟萃分析也支持当前的建议，显示高负荷 (HL-RT) 相对于 ML-RT 和 LL-RT 在肌肉力量方面的安全性和优越性，以及对健康年轻人肌肉肥大的类似影响和老年人。^6、7此外，LL-RT 组和 ML-RT 组之间的累积训练负荷应该通过多次重复来平衡（两个 RT 组都进行了三组 14 次重复）。此外，在给定的 RT 负荷下的重复范围不是最理想的，因为 RT 建议在强度低于 1-RM 的 65% 时使用超过 15 次/组的重复次数。⁸

我们认为，所设计的研究方案对于潜在的肌肉结果并不理想，并且可以在很大程度上解释 RT 组之间在大多数肌肉肥大测量以及最大肌肉力量方面缺乏差异。作者没有报告但有趣的是，每个 RT 组和对照组之间的 1-RM 改善是否存在差异，类似于他们报告的肌肉质量和数量结果。

由于肌肉减少症轨迹严重影响肌肉质量和功能，因此使用最佳 RT 来抵消这些变化非常重要。Otsuka等人的出色研究。^图4展示了 RT 负荷与肌肉肥大和力量变化之间的剂量依赖性关系的新见解。虽然有越来越多的证据表明使用各种放疗强度（从 LL 到 HL）可以减轻肌肉萎缩^，6、7临床医生也应该意识到它对肌肉功能的负面影响。随着年龄的增长，肌肉量的减少与肌肉去神经支配和循环合成代谢激素（例如生长激素、胰岛素样生长因子 I 和 II）的减少密切相关，^1,9,10这可以通过使用 HL-RT 来抵消，特别是考虑到它在改善最大肌肉力量和激活方面优于 LL-RT。^{3, 6, 7}此外，近期针对肌肉减少症风险较高的慢性病患者（如癌症，^{11, 12}冠状动脉疾病，¹³慢性肾病，^14-16慢性肺病^{17 ）}的研究和指南已经取代了 LL -RT 与渐进式 ML-to-HL-RT 或仅 HL-RT。目前，越来越多的证据表明，与标准护理甚至单独的有氧训练相比，ML-RT 和 HL-RT 对肌肉肥大和肌肉力量的有益影响。

因此，我们支持将 HL-RT 作为老年人和患者肌肉减少症一级和二级预防的核心组成部分。进一步的研究应主要关注 HL-RT 与其他 RT 方式相比在肌肉减少和/或恶病质患者的最大肌肉力量和激活、合成代谢激素信号通路以及肌肉质量和数量方面的安全性、可行性和有效性。