Shirai Takanaga, Uemichi Kazuki, Iwai Ryoto, Shinkai Hayato, Iwata Tomohiro, Tanimura Riku, Sugiyama Shunsuke, Takemasa Tohru
Department of Human Sciences, Kanagawa University, Kanagawa, Japan.
Research Fellow of Japan Society for Promotion Science, Tokyo, Japan.
Am J Physiol Endocrinol Metab. 2025 May 1;328(5):E695-E710. doi: 10.1152/ajpendo.00433.2024. Epub 2025 Apr 18.
In this study, we examined the effects of concurrent functional overload and endurance exercise on muscle hypertrophy, mitochondrial function, and systemic adaptations in male mice. The mice were assigned to three groups: Sham (Sham), overload-induced hypertrophy (OL), and overload with concurrent 60-min free swimming (5 times/wk) (OL + Swim), for 4 wk. Although OL promoted muscle hypertrophy and protein synthesis through the Akt/mammalian/mechanistic target of rapamycin (mTOR) signaling pathway, the addition of swimming (OL + Swim) attenuated these effects, resulting in less pronounced muscle growth and a smaller increase in myofiber cross-sectional area. Notably, the OL + Swim group exhibited enhanced mitochondrial activity and glycogen content compared with the OL group. Both the OL and OL + Swim groups showed elevated rates of protein synthesis, with a significant upregulation of AMP-activated kinase (AMPK) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) in the OL + Swim group, suggesting enhanced mitochondrial biogenesis and adaptation. Concurrent training also resulted in systemic benefits, including reduced inguinal and epididymal white adipocyte size, improved mitochondrial enzyme activities in adipose and liver tissues, and higher levels of fibronectin type III domain containing protein 5 (FNDC5), fibroblast growth factor 21 (FGF21), and brain-derived neurotrophic factor (BDNF) in serum, which contributed to enhanced muscle protein synthesis in cultured muscle cells. These results highlight the trade-offs between muscle hypertrophy and metabolic health in mice and underscore the importance of balanced training regimens to optimize overall metabolic health and muscle function. Our results provide further insight into how concurrent strength and endurance training can be optimized for health and performance benefits. This study provides novel insights into the mechanisms underlying the interference effect that occurs in concurrent training, highlighting the potential systemic benefits of combining resistance and endurance exercises. Despite a reduction in muscle hypertrophy, concurrent training enhances metabolic adaptations and systemic health markers and offers a comprehensive approach to improving both muscle and metabolic fitness.
在本研究中，我们检测了同时进行功能性超负荷训练和耐力运动对雄性小鼠肌肉肥大、线粒体功能及全身适应性的影响。将小鼠分为三组：假手术组（Sham）、超负荷诱导肥大组（OL）和同时进行60分钟自由游泳（每周5次）的超负荷训练组（OL + Swim），为期4周。尽管OL通过Akt/哺乳动物/雷帕霉素机制性靶标（mTOR）信号通路促进肌肉肥大和蛋白质合成，但加入游泳训练（OL + Swim）减弱了这些作用，导致肌肉生长不明显，肌纤维横截面积增加较小。值得注意的是，与OL组相比，OL + Swim组的线粒体活性和糖原含量增强。OL组和OL + Swim组的蛋白质合成率均升高，OL + Swim组的AMP激活蛋白激酶（AMPK）和过氧化物酶体增殖物激活受体γ共激活因子1α（PGC-1α）显著上调，提示线粒体生物合成和适应性增强。同时训练还带来了全身益处，包括腹股沟和附睾白色脂肪细胞尺寸减小、脂肪和肝脏组织中线粒体酶活性提高，以及血清中含III型纤连蛋白结构域蛋白5（FNDC5）、成纤维细胞生长因子21（FGF21）和脑源性神经营养因子（BDNF）水平升高，这些都有助于增强培养肌细胞中的肌肉蛋白质合成。这些结果凸显了小鼠肌肉肥大与代谢健康之间的权衡，并强调了平衡训练方案对优化整体代谢健康和肌肉功能的重要性。我们的结果为如何优化同时进行的力量和耐力训练以获得健康和性能益处提供了进一步的见解。本研究为同时训练中发生的干扰效应的潜在机制提供了新的见解，突出了结合抗阻训练和耐力训练的潜在全身益处。尽管肌肉肥大有所减少，但同时训练增强了代谢适应性和全身健康指标，并提供了一种改善肌肉和代谢适应性的综合方法。
