左右二側肘屈肌群進行二回合離心運動順序對動脈血管硬化之影響

Effect of performing order of the first and repeated bouts of maximal eccentric exercise of the right and left elbow flexors on arterial stiffness

緒論：近期研究發現，先以一側肢體肌群做一回合離心運動 (the first bout of eccentric exercise, EC1) 之後間隔2-3週休息之後，改成對側肌群進行相同一回合離心運動訓練 (the second bout of EC, EC2) 時，可明顯降低引起肌肉損傷之效果，相關文獻稱此現象為交叉重複訓練效果 (contralateral repeated bout effect, CL-RBE)。最近文獻發現，人體以單側肘屈肌群 (elbow flexors, EF) 進行一回合離心運動引起肌肉損傷(exercise-induced muscle damage, EIMD) 時，會誘發暫時性動脈血管硬化之現象，並推測EIMD可能是藉由發炎反應作用，進而誘發動脈血管硬化之現象，但目前不清楚人體以同側、對側或甚至於是慣用側 (dominant limb, DL) 與非慣用側 (non-DL, NDL) 肌群不同順序等方式，進行二回合離心運動訓練，是否可以有效降低誘發動脈血管硬化之效果。因此，本研究目的在於探討「人體以DL或NDL進行EC1引起肌肉損傷後，換成另一側群繼續進行相同一回合離心訓練 (EC2) 時，其對降低動脈硬化之影響」。方法：招募24位坐式生活的大學健康男性學生為研究對象，並以隨機方式分成：NDL組、DL組或控制組 (control, CON) 之中 (每組8人)。所有三組都進行二回合EF最大等速 (30°/s) 離心運動 (每回合30次；二回合之間間隔4週)；其中，NDL組以非慣用手EF作EC1，慣用手EF進行EC2；DL組先以慣用手EF作EC1，非慣用手EF接受EC2；CON組統一以非慣用手EF作EC1-2。最大自主等長收縮肌力 (maximal voluntary isometric contraction, MVIC)、肌肉酸痛 (SOR)、頸股動脈波傳導速率 (carotid-femoral pulse wave velocity, cfPWV)、舒張壓、收縮壓及心跳，在每回合訓練前與後第0 (30分鐘)、2、4天各進行一次測驗。以二因子混合設計變異數分析，考驗每個依變項在回合與時間因子之間的差異情形。結果：在EC1之後，除了舒張壓、收縮壓及心跳無產生明顯改變外，其他指標均產生顯著的變化 (e.g. MVIC最大下降率: -49 ± 5 %；p < .05)，但不同三組之間無差異 (p > .05)。在EC2之後，NDL組 (-29 ± 6%) 與CON組 (-30 ± 5 %) 依變項的變化程度明顯比DL組 (-39 ± 2 %) 來得小。NDL組與CON組在EC2後引起MVIC、SOR和cfPWV變化程度均明顯 (p < .05) 小於CON的EC1，但是DL組在EC2後的依變項變化程度與CON組EC1之間無差異 (p > .05)。結論：本研究發現，人體先以非慣用手EF作EC1後，在改換成慣用手EF進行EC2時，則可與單側EF產生相同程度之訓練效果，並且能避免誘發動脈血管硬化之效果；但是在一開始先以慣用手EF作EC1後，再改由非慣用手EF作EC2的話，就無法產生降低誘發動脈血管硬化之效果。因此，這些研究結果，將可提供給EIMD研究者作為實驗設計時之參考。

Introduction: Recent studies have found that an initial bout of maximal eccentric exercise (EC1) using the ipsilateral limb performed 2-3 weeks prior to a subsequent bout of the same exercise (EC2) using the contralateral limb could reduce muscle damage on the contralateral limb. This phenomenon is called contralateral RBE (CL-RBE). Previous studies found that performing one bout of EC using the elbow flexors (EF) of the ipsilateral limb induced muscle damage and transient arterial stiffening, but it is still unknown whether the order in which the two limbs are used [e.g., performing EC1 with the dominant limb (DL) and EC2 with the non-dominant limb (NDL), or vice versa] will affect the magnitude of arterial stiffening. Therefore, the purpose of the present study tested the hypothesis that performing an initial bout of maximal eccentric exercise (i.e., EC1) using either the DL or NDL would result in reduced arterial stiffness following a subsequent bout of eccentric exercise (i.e., EC2) using the opposite limb. Methods: Twenty-four young untrained men were allocated to NDL, DL or control (CON) group (n=8 per group). All groups performed two bouts of maximal eccentric exercise (EC1, EC2) consisting of 30 maximal EF contractions at the angular velocity of 30°/s. The NDL group performed EC2 using the dominant limb at 4 weeks after EC1 using the non-dominant limb. The DL group performed EC2 using the non-dominant limb at 4 weeks after EC1 of the dominant limb. The CON group performed EC2 using the NDL at 4 weeks after EC1 using the same NDL. Changes in maximal voluntary isometric strength (MVIC), muscle soreness (SOR), arterial stiffness [carotid-femoral pulse-wave velocity (cfPWV)], systolic (SBP) and diastolic blood pressure (DBP), and heart rate (HR) were measured before, immediately after (~30 minutes), and 2 and 4 days after each bout. Changes in each dependent variable over time after eccentric exercise were compared by a mixed-design ANOVA. Results: SBP, DBP and HR were not significantly changed following EC1 and EC2. However, changes in the rest of the dependent variables (e.g. greatest MVIC loss: -49 ± 5 %) showed significantly changes (p < .05) following EC1 without significant differences among the groups. After EC2, both the NDL (-29 ± 6%) and CON groups (-30 ± 5 %) showed significantly smaller changes than the DL group (-39 ± 2 %). Changes in MVIC, SOR and cfPWV of the NDL and CON groups following EC2 were significantly (p < .05) smaller compared with those of the CON group following EC1, but those of the DL group following EC2 showed no significant difference (p > .05) from those of the CON group following EC1. Conclusion: These results suggest that an initial bout of EC1 using the EF of the non-dominant limb, followed by EC2 using the EF of the dominant limb, produced CL-RBE and decreased arterial stiffness. However, these effects were not observed when EC1 was performed using the dominant EF, followed by EC2 using the non-dominant EF. Therefore, the results of the present study can provide a useful reference for investigators of EC-induced muscle damage.