Pasiakos Stefan M, McClung Holly L, Margolis Lee M, Murphy Nancy E, Lin Gregory G, Hydren Jay R, Young Andrew J
Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA, United States of America.
Military Performance Division, US Army Research Institute of Environmental Medicine, Natick, MA, United States of America.
PLoS One. 2015 Oct 16;10(10):e0140863. doi: 10.1371/journal.pone.0140863. eCollection 2015.
Effects of conventional endurance (CE) exercise and essential amino acid (EAA) supplementation on protein turnover are well described. Protein turnover responses to weighted endurance exercise (i.e., load carriage, LC) and EAA may differ from CE, because the mechanical forces and contractile properties of LC and CE likely differ. This study examined muscle protein synthesis (MPS) and whole-body protein turnover in response to LC and CE, with and without EAA supplementation, using stable isotope amino acid tracer infusions. Forty adults (mean ± SD, 22 ± 4 y, 80 ± 10 kg, VO 2peak 4.0 ± 0.5 L ∙ min(-1)) were randomly assigned to perform 90 min, absolute intensity-matched (2.2 ± 0.1 VO2 L ∙ m(-1)) LC (performed on a treadmill wearing a vest equal to 30% of individual body mass, mean ± SD load carried 24 ± 3 kg) or CE (cycle ergometry performed at the same absolute VO2 as LC) exercise, during which EAA (10 g EAA, 3.6 g leucine) or control (CON, non-nutritive) drinks were consumed. Mixed-muscle and myofibrillar MPS were higher during exercise for LC than CE (mode main effect, P < 0.05), independent of dietary treatment. EAA enhanced mixed-muscle and sarcoplasmic MPS during exercise, regardless of mode (drink main effect, P < 0.05). Mixed-muscle and sarcoplasmic MPS were higher in recovery for LC than CE (mode main effect, P < 0.05). No other differences or interactions (mode x drink) were observed. However, EAA attenuated whole-body protein breakdown, increased amino acid oxidation, and enhanced net protein balance in recovery compared to CON, regardless of exercise mode (P < 0.05). These data show that, although whole-body protein turnover responses to absolute VO2-matched LC and CE are the same, LC elicited a greater muscle protein synthetic response than CE.
常规耐力（CE）运动和补充必需氨基酸（EAA）对蛋白质周转的影响已有充分描述。蛋白质周转对负重耐力运动（即负荷携带，LC）和EAA的反应可能与CE不同，因为LC和CE的机械力和收缩特性可能不同。本研究使用稳定同位素氨基酸示踪剂输注，研究了在补充或不补充EAA的情况下，LC和CE对肌肉蛋白质合成（MPS）和全身蛋白质周转的影响。40名成年人（平均±标准差，22±4岁，80±10 kg，VO₂峰值4.0±0.5 L·min⁻¹）被随机分配进行90分钟、绝对强度匹配（2.2±0.1 VO₂ L·m⁻¹）的LC（在跑步机上穿着相当于个体体重30%的背心进行，平均±标准差负荷为24±3 kg）或CE（在与LC相同的绝对VO₂下进行自行车测力计运动），在此期间饮用EAA（10 g EAA，3.6 g亮氨酸）或对照（CON，无营养）饮料。无论饮食处理如何，运动期间LC的混合肌肉和肌原纤维MPS均高于CE（运动方式主效应，P<0.05）。无论运动方式如何，EAA均可增强运动期间的混合肌肉和肌浆MPS（饮料主效应，P<0.05）。恢复期间，LC的混合肌肉和肌浆MPS高于CE（运动方式主效应，P<0.05）。未观察到其他差异或相互作用（运动方式×饮料）。然而，与CON相比，无论运动方式如何，EAA均可减轻全身蛋白质分解，增加氨基酸氧化，并增强恢复期间的净蛋白质平衡（P<0.05）。这些数据表明，尽管全身蛋白质周转对绝对VO₂匹配的LC和CE的反应相同，但LC比CE引发了更大的肌肉蛋白质合成反应。
