長期上臂固定會增加離心運動引起肌肉損傷的負面效果

Long-term upper arm immobilization can increase the magnitude of eccentric exercise-induced muscle damage

緒論：固定術（immobilization, IM）時常使用在肢體嚴重受傷或骨折時，作為限制其關節活動、提供支撐並達到保護受傷組織之目的，同時能防止受傷部位在癒合過程中受外力或牽拉造成二次傷害。然而，長期固定後若進行最大強度離心運動（maximal eccentricexercise, MAX）引起肌肉損傷（exercise-induced muscle damage, EIMD）的影響程度為何，目前尚不清楚。目的：考驗「單側肘屈肌接受長期固定後，進行一回合最大離心運動（MAX）對引起肌肉損傷的影響」。方法：招募18位健康大專成年男性為研究對象，隨機分配至IM組與控制組（CON組）（n = 9/組）。IM組使用石膏將其非慣用側肘關節固定連續21天；CON組無接受任何固定。在固定前、後，進行單側最大等長肌力（MVC）、上臂圍（CIR）測量，並且在石膏拆除後第24小進行一回合5組x 6次最大離心運動（MAX），MAX前與MAX後第1、2、3天測量血液中肌球蛋白濃度（Mb）、延遲性肌肉酸痛（DOMS）、CIR、MVC的變化情形。結果：IM組經過21天固定後MVC與CIR的下降率顯著高於CON組（p < .05），在MAX後IM組所有指標的損傷程度均明顯高於CON組（p < .05）。結論：肌肉經過長期固定休息之後，在隨後進行一回合高強度離心運動引起肌肉損傷的程度，明顯比單純進行一回合最大離心運動的控制組來得大之負面反應的效果。因此，未來研究宜針對此問題建立可避免或減緩發生肌肉傷害的策略或方法。

Introduction: Immobilization (IM) is frequently applied to limit joint movement, provide support, and protect injured tissues when a limb is severely injured, or bones are fractured to prevent secondary injuries caused by external force or movements during the healing process. However, the effects of maximal eccentric exercise (MAX)–induced muscle damage (EIMD) after long-term IM remain unclear. Purpose: The purpose of the present study was to test whether the magnitude of EIMD increases following the long-term IM of elbow flexors compared with a control group without IM (CON). Methods: Eighteen healthy men were recruited from a local university and randomly assigned to the IM group or the CON group (n = 9/group). The IM group had their non-dominant elbow joints fixed in a cast to provide IM for 21 consecutive days, whereas the CON group did not receive any IM. Before and after the IM intervention, the maximal voluntary isometric contraction strength (MVC) and upper arm circumference (CIR) were measured for the non-dominant arm of each participant, and 5 sets of 6 MAX repetitions were performed 24 hours after cast removal. Plasma myoglobin (Mb) concentrations, delayed-onset muscle soreness (DOMS), CIR, and MVC were measured before, 1, 2, and 3 days after MAX performance in both groups. Results: Significant decreases in MVC and CIR were evident after 21 days of IM in the IM group compared with the CON group (p < .05). Significantly larger magnitudes of EIMD marker changes were observed after MAX in the IM group compared with the CON group (p < .05). Conclusion: Long-term elbow flexor IM negatively affected muscle functions and increased the magnitude of muscle damage induced by a subsequent bout of MAX. Future studies are warranted to establish efficient prevention strategies to avoid EIMD after IM.