不同落地訓練時期對成長中母鼠骨骼之影響

Abstract

目的：探討不同時間長度之落地訓練對骨骼的影響，以釐清骨骼適應高衝擊性運動在時間序列上的變化。方法：使用96隻週齡7週的Wistar雌性大鼠，在四個時間點分別設置落地訓練組與對照組，每組動物數為12，依序為1週落地訓練組 (E1)、1週對照組 (C1)、2週落地訓練組 (E2)、2週對照組 (C2)、4週落地訓練組 (E4)、4週對照組 (C4)、8週落地訓練組 (E8)、8週對照組 (C8)，落地訓練組每日接受30次自40公分的高處落下著地之訓練，並於每週的第一次訓練與第五次訓練架設測力板以記錄地面反作用力 (ground reaction force, GRF) 作為運動強度探討；對照組則維持正常的籠內活動。各組實驗動物分別於4個時間點（訓練1、2、4及8週之後）犧牲，並採集其左右的股骨與脛骨，進行骨密度、組織型態、組織生物力學、斷面參數等測量與分析。採用獨立樣本t檢定與單因子變異數分析 (α=.05)。結果：大鼠在第一週第一天的落地GRF值顯著高於其他時間點 (p＜.05)；股骨的皮質骨面積與厚度呈現E1顯著低於C1、E4顯著高於C4，脛骨則是E8在皮質骨面積、皮質骨厚度及斷面轉動慣量矩顯著高於C8；股骨與脛骨海綿骨的骨生成指數（鹼性磷酸酶染色）、骨密度與結構參數（包括骨量比率及骨小樑厚度）皆為E8顯著高於C8組，而脛骨的海綿骨骨吸收指數（破骨細胞數）則是E8顯著低於C8；股骨的斷裂負荷值E1顯著低於C1，而E8的股骨與脛骨皆有顯著高於C8的斷裂負荷值。結論：皮質骨承受落地訓練初期時會因衝擊過大造成骨骼結構與骨生物力學強度暫時性的變弱，經過長期訓練適應之後則可恢復並增強；對快速成長中之海綿骨而言，訓練初期雖無法觀察到訓練效果，唯長期訓練則可呈現結構強化並提升骨密度。

Purpose: To investigate the effects of a time course free-fall landing training on bone metabolism in growing female rats. Methods: Ninety-six rats (7 weeks old) were assigned into eight groups (n=12/group), which were E1, E2, E4 E8, C1, C2, C4 and C8. Animals of the E1, E2, E4 and E8 groups were respectively subjected to 1, 2, 4 and 8 weeks free-fall landing training, in which animals were free-fallen from a height of 40 cm for 30 times per day; 5 days per week. The C1, C2, C4 and C8 groups served as the time matched groups. Additionally, we collected ground reaction force (GRF) data from force plate on day 1 and day 5 every week for 8 weeks. We used methods of micro-computed tomography (μCT), static histomorphometry, geometry measurement and tissue biomechanical testing to estimate the effects of free fall landing on growing bone. Results: Peak GRF on day 1 in first week was significantly higher than other time points (p＜.05). In the geometry measurement of femur, E1 group was significantly lower than C1 group whereas E4 was significantly higher than C4 in cortical area and thickness. In addition, E8 group was significantly higher than C8 in cortical area, cortical thickness and cross-sectional moment of inertia of tibiae. In trabecular bone formation index (alkaline phosphatase staining), bone mineral density and trabecular architectures (e.g. bone volume ratio, trabecular thickness) of femora and tibiae, E8 groups were significantly higher than C8 groups. In addition, E8 was significantly lower than C8 in trabecular bone resorption index (osteoclast number) of tibiae. In Biomechanical testing, fracture load of femora was significantly lower in E1 group as compared to C1. Conversely, E8 group was higher than C8 group in femora and tibiae. Conclusion: Landing training would cause a transiently compromised bone material in initial phase of cortical bone, and a recovery and enhancement in bone strength would occur following a longer period of training. Efficacy of landing training on trabecular bone was only showed after the 8-week training period.