Siegler Jason C, Mudie Kurt, Marshall Paul
Sport and Exercise Science, School of Science and Health, Western Sydney University, Sydney, New South Wales, Australia.
Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, Victoria, Australia.
Exp Physiol. 2016 Nov 1;101(11):1383-1391. doi: 10.1113/EP085933.
What is the central question of this study? Does metabolic alkalosis in humans, induced by sodium bicarbonate, affect rates of skeletal muscle fatigue differentially in muscle groups composed predominately of slow- and fast-twitch fibres? What is the main finding and its importance? Sodium bicarbonate exhibited no effect on the fatigue profile observed between triceps surae and brachii muscle groups during and after 2 min of tetanic stimulation. For the first time in exercising humans, we have profiled the effect of sodium bicarbonate on the voluntary and involuntary contractile characteristics of muscle groups representative of predominately slow- and fast-twitch fibres. The effect of metabolic alkalosis on fibre-specific maximal force production and rates of force development (RFD) has been investigated previously in animal models, with evidence suggesting an improved capacity to develop force rapidly in fast- compared with slow-twitch muscle. We have attempted to model in vivo the fatigue profile of voluntary and involuntary maximal force and RFD in the triceps surae and brachii after sodium bicarbonate (NaHCO ) ingestion. In a double-blind, three-way repeated-measures design, participants (n = 10) ingested either 0.3 g kg NaHCO (ALK) or equivalent calcium carbonate (PLA) prior to 2 min of continuous (1 Hz) supramaximal stimulation (300 ms at 40 Hz) of the triceps surae or brachii, with maximal voluntary efforts (maximal voluntary torque) coupled with direct muscle stimulation also measured at baseline, 1 and 2 min. Metabolic alkalosis was achieved in both ALK trials but was not different between muscle groups. Regardless of the conditions, involuntary torque declined nearly 60% in the triceps brachii (P < 0.001) and ∼30% in the triceps surae (P < 0.001). In all trials, there was a significant decline in normalized involuntary RFD (P < 0.05). Maximal voluntary torque declined nearly 28% but was not different between conditions (P < 0.01), and although declining nearly 21% in voluntary RFD (P < 0.05) there was no difference between PLA and ALK in either muscle group (P = 0.93). Sodium bicarbonate exhibited no effect on the fatigue observed between representative fibre-type muscle groups on maximal voluntary and involuntary torque or rates of torque development during and after 2 min of tetanic stimulation.
本研究的核心问题是什么？由碳酸氢钠诱发的人体代谢性碱中毒，是否会对主要由慢肌纤维和快肌纤维组成的肌肉群中骨骼肌疲劳的发生率产生不同影响？主要发现及其重要性是什么？在强直刺激2分钟期间及之后，碳酸氢钠对腓肠肌和肱三头肌肌肉群之间观察到的疲劳情况没有影响。在进行运动的人体中，我们首次分析了碳酸氢钠对主要代表慢肌纤维和快肌纤维的肌肉群的随意和非随意收缩特性的影响。此前已在动物模型中研究了代谢性碱中毒对纤维特异性最大力量产生和力量发展速率（RFD）的影响，有证据表明，与慢肌纤维相比，快肌纤维快速产生力量的能力有所提高。我们试图在体内模拟摄入碳酸氢钠（NaHCO₃）后腓肠肌和肱三头肌随意和非随意最大力量及RFD的疲劳情况。在一项双盲、三因素重复测量设计中，参与者（n = 10）在对腓肠肌或肱三头肌进行2分钟持续（1Hz）超强刺激（40Hz，300ms）之前，摄入0.3g/kg碳酸氢钠（ALK）或等量碳酸钙（PLA），同时在基线、1分钟和2分钟时测量最大随意努力（最大随意扭矩）以及直接肌肉刺激。在两个ALK试验中均实现了代谢性碱中毒，但肌肉群之间没有差异。无论何种情况，肱三头肌的非随意扭矩下降近60%（P < 0.001），腓肠肌下降约30%（P < 0.001）。在所有试验中，标准化非随意RFD均显著下降（P < 0.05）。最大随意扭矩下降近28%，但不同条件之间没有差异（P < 0.01）；尽管随意RFD下降近21%（P < 0.05），但在两个肌肉群中PLA和ALK之间均无差异（P = 0.93）。在强直刺激2分钟期间及之后，碳酸氢钠对代表不同纤维类型的肌肉群在最大随意和非随意扭矩或扭矩发展速率方面观察到的疲劳没有影响。
