Defining exercise intensities.

BackgroundAerobic exercise promotes mitochondrial morphological, enzymatic, and bioenergetic adaptions to improve muscle health and function. Although moderate intensity continuous training (MICT) is frequently recommended for sedentary and multiple clinical populations, there is little consensus regarding the effects of chronic MICT on these adaptations. The aim of this systematic review and meta-analysis is to evaluate the evidence for the effects of MICT on molecular transducers of mitochondrial biogenesis and cardiorespiratory fitness in adults.MethodsA comprehensive search was conducted in PubMed and CINAHL. Eligible studies assessed MICT lasting ≥2 weeks in adults, published since 2010, and collected vastus lateralis skeletal muscle biopsies pre and post chronic endurance exercise exposure. Data were extracted for mitochondrial transcription factor A (TFAM), citrate synthase (CS), peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC-1α), mitofusin 2 (MFN2), dynamin-related protein 1 (DRP1), VO₂max, and mitochondrial density (MitoVD). Meta-analyses using inverse-variance random effects models were conducted for outcomes reported in at least three studies.ResultsA total of fourteen studies (n = 184) met inclusion criteria, with an overall low to moderate risk of bias and very low to low certainty of evidence. MICT significantly increased MitoVD (p p p = 0.05) and MFN2 showed a modest increase (p = 0.01) following MICT. No changes were observed for TFAM, DRP1, or PGC-1α.ConclusionMICT significantly improves MFN2 expression, CS activity, MitoVD, and VO2 max in adults. However, the overall quality of evidence is low. Heterogeneity in molecular responses suggests potential moderating effects of training duration, modality (e.g., cycling vs. treadmill), and sex – warranting further research.RegistrationPROSPERO ID:CRD42024611640.

背景 有氧运动可促进线粒体在形态、酶学及生物能量学层面的适应性改变，从而改善肌肉健康与功能。尽管中等强度持续训练（Moderate Intensity Continuous Training, MICT）常被推荐给久坐人群及多种临床患者群体，但目前针对慢性中等强度持续训练对上述适应性改变的影响，学界尚未达成广泛共识。本系统综述与荟萃分析旨在评估慢性中等强度持续训练对成人体线粒体生物发生分子转导通路及心肺适能的影响证据。方法 研究团队在PubMed及CINAHL数据库中开展了全面的文献检索。纳入标准为：研究对象为成年人，干预为时长≥2周的中等强度持续训练，发表时间为2010年及以后，且在慢性耐力训练干预前后采集了股外侧肌骨骼肌活检样本。提取的研究数据包括线粒体转录因子A（Mitochondrial Transcription Factor A, TFAM）、柠檬酸合酶（Citrate Synthase, CS）、过氧化物酶体增殖物激活受体γ辅激活因子1-α（Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-Alpha, PGC-1α）、线粒体融合蛋白2（Mitofusin 2, MFN2）、动力相关蛋白1（Dynamin-Related Protein 1, DRP1）、最大摄氧量（VO₂max）及线粒体密度（Mitochondrial Density, MitoVD）。针对至少3项研究共同报道的结局指标，采用逆方差随机效应模型开展荟萃分析。结果 最终共有14项研究（n=184）符合纳入标准，整体偏倚风险为低至中等水平，证据确定性为极低至低水平。中等强度持续训练可显著提升线粒体密度（MitoVD，p<0.001）、柠檬酸合酶活性（p=0.02）及最大摄氧量（VO₂max，p=0.05），线粒体融合蛋白2（MFN2）则呈现小幅上调（p=0.01）；未观察到线粒体转录因子A（TFAM）、动力相关蛋白1（DRP1）及过氧化物酶体增殖物激活受体γ辅激活因子1-α（PGC-1α）出现显著变化。结论 本研究结果显示，中等强度持续训练可显著提升成人体线粒体融合蛋白2（MFN2）表达水平、柠檬酸合酶活性、线粒体密度及最大摄氧量。但整体证据质量仍处于较低水平。分子层面的应答异质性提示，训练时长、训练形式（如骑行与跑台训练）及性别可能存在调节效应，亟需开展进一步研究加以验证。注册信息 PROSPERO编号：CRD42024611640。