Department of Life Sciences, Research Centre for Musculoskeletal Science & Sports Medicine, Manchester Metropolitan University, Manchester, UK.
Lithuanian Sports University, Kaunas, Lithuania.
Exp Physiol. 2020 Dec;105(12):2110-2122. doi: 10.1113/EP089096. Epub 2020 Nov 12.
What is the central question of this study? Does combining endurance and hypertrophic stimuli blunt the adaptations to both modalities and is this effect greater in muscles with larger baseline fibre cross sectional area? What is the main finding and its importance? Endurance exercise and hypertrophic stimuli can be combined to increase fatigue resistance and fibre size without blunting either adaptation regardless of baseline fibre size.
Previous studies have demonstrated that fibre cross-sectional area (FCSA) is inversely related to oxidative capacity, which is thought to be determined by diffusion limitations of oxygen, ADP and ATP. Consequently, it is hypothesised that (1) when endurance training is combined with a hypertrophic stimulus the response to each will be blunted, and (2) muscles with a smaller FCSA will show a larger hypertrophic response than those with a large FCSA. To investigate this, we combined overload with endurance exercise in 12-month-old male mice from three different strains with different FCSA: Berlin High (BEH) (large fibres), C57BL/6J (C57) (normal-sized fibres) and Berlin Low (BEL) (small fibres). The right plantaris muscle was subjected to overload through denervation of synergists with the left muscle acting as an internal control. Half the animals trained 30 min per day for 6 weeks. The overload-induced hypertrophy was not blunted by endurance exercise, and the exercise-induced increase in fatigue resistance was not impaired by overload. All strains demonstrated similar absolute increases in FCSA, although the BEH mice with more fibres than the C57 mice demonstrated the largest increase in muscle mass and BEL mice with fewer fibres the smallest increase in muscle mass. This study suggests that endurance exercise and hypertrophic stimuli can be combined without attenuating adaptations to either modality, and that increases in FCSA are independent of baseline fibre size.
这项研究的核心问题是什么？将耐力和肥大刺激相结合是否会削弱两种刺激的适应能力，而且这种影响在基线纤维横截面积较大的肌肉中更大？主要发现及其重要性是什么？耐力运动和肥大刺激可以结合使用，在不削弱任何一种适应能力的情况下提高疲劳抵抗力和纤维大小，而与基线纤维大小无关。
以前的研究表明，纤维横截面积（FCSA）与氧化能力呈反比，氧化能力被认为是由氧、ADP 和 ATP 的扩散限制决定的。因此，有人假设（1）当耐力训练与肥大刺激结合时，每种刺激的反应都会减弱，（2）FCSA 较小的肌肉比 FCSA 较大的肌肉表现出更大的肥大反应。为了研究这一点，我们将超负荷与耐力运动相结合，对来自三个不同 FCSA （柏林高（BEH）（大纤维）、C57BL/6J（C57）（正常大小纤维）和柏林低（BEL）（小纤维）的不同品种的 12 个月大雄性小鼠进行了研究。右侧比目鱼肌通过协同肌去神经化来超负荷，左侧肌肉作为内部对照。一半的动物每天训练 30 分钟，持续 6 周。耐力运动并没有削弱超负荷引起的肥大，而超负荷并没有损害运动引起的疲劳抵抗力的增加。所有品系的 FCSA 都表现出相似的绝对增加，尽管比 C57 小鼠纤维更多的 BEH 小鼠表现出肌肉质量增加最多，而纤维较少的 BEL 小鼠肌肉质量增加最少。这项研究表明，耐力运动和肥大刺激可以结合使用，而不会削弱对任何一种刺激的适应能力，并且 FCSA 的增加与基线纤维大小无关。
