Can the Center of Mass Reflect the Metabolic Expenditure?

LANGUAGE NOTE | Document text in English; abstract also in Chinese. In the past studies, the movement of center or mass (COM) was one of the descriptor to estimate the metabolic expenditure. However, the sensitivity of this method among the wide range speed, the locomotion pattern and during the Energetically Optimal Transition Speed (EOTS) is still unexplored. Hence that, the purpose of this investigation was to determine the metabolic and COM pattern differences between walk and run among the EOTS with a reflective marker motion analysis system and indirect pulmonary ventilation machine. The results showed that there is a metabolic intersection on two locomotion patterns (walk and run) between 100 and 125% Preferred Transition Speed (PTS), which coincides with the past EOTS studies, whereas, COM result showed that the variation of vertical COM displacement for running is significantly higher than walking among the entire tested speed. The pattern between the metabolic and COM variables is an inverse relation after the EOTS. Hence, the present investigator doubted that there would be a reliability problem for those instruments which use the COM displacement to estimate the metabolic cost or the intensity of physical activity among 5.15 to 9.82km/h for walk and run. 在過去的研究身體質量中心移動常常被用作評估身體耗能的一種方法。可是這種方法在不同速度、動作型態及最佳轉換速度(EOTS)之可信範圍一直都沒有作出深入探討。因此本研究目的希望利用動作及生理分析系統對身體中心及身體耗能在兩種動作型態(走和跑)和在EOTS的情況底下的趨勢上作出分析及探討。結果顯示在兩個動作型態上在100及125%自然轉換速度情況下身體耗能出現交叉點(EOTS)而此發現與過去EOTS之文獻相吻合反之身體質量中心結果顯示跑步在身體質量中心之穩定性在所有測試速度情況下都比走路有統計上之差異跑步的垂直位移變異量明顯比走路大。由此可見身體耗能及身體質量中心變異量顯示出兩者在EOTS出現後是反比關係。因此本研究結果可推斷現在有利用身體質量中心變異量去推估身體耗能或身體活動量的儀器在速度5.15—9.82公里的情況底下可能會出現信度問題。