The Relationship between Muscle Activity of the Quadriceps Muscle and Ground Reaction Force in the Supporting Leg during Ascent and Descent Motions

[Purpose] To understand stair ascent and descent motions, we examined the muscle activities of the vastus medialis (VM) and vastus lateralis (VL) and the ground reaction force (GRF) in the supporting leg of eight young healthy males. We also compared these data with level walking data. [Result] The muscle activities of VM and VL during the ascent motion were the highest among the three tasks. The muscle activity ratios of VM and VL during ascending and descending differed from that during level walking. The VM contribution increased in the ascent and descent tasks compared with level walking. There was no significant difference for the vertical GRF among the tasks. Although the anterior-posterior GRF during the ascent motion was similar to that during level walking, the anteriorposterior GRF during the descent motion was different from that of the ascent motion and level walking. Further, the medial-lateral GRF during ascending and descending were different from that during level walking. [Conclusion] The results of this study suggest that the increased VM contribution of the supporting leg may be related to the change of medial-lateral GRF during ascent and descent. This finding will add knowledge to the rehabilitation and physical therapy of ascent and descent motions for elderly people and patients with motor disorders.
〔目的〕段差昇降時の支持脚の大腿四頭筋（内側広筋と外側広筋）と床反力の関係について筋電図計と床反力計を用いて測定した。〔対象〕若年健康男性8 名とした。〔結果〕内側広筋と外側広筋の筋活動は昇段動作で最も大きな値を示していた。内側広筋と外側広筋の筋活動の比率は歩行に比べ段差昇降動作で大きな値を示し，内側広筋の活動の関与を高めていた。垂直方向の床反力の値は動作間で差はみられなかったが，昇降動作時の外側方向の分力は歩行に比べ有意に低い値を示していた。内側方向の分力に動作間の差がみられなかったことから，相対的に内側方向への力が増大し，内側広筋の筋活動の増大に関連している可能性が示唆される。〔結語〕段差昇降では身体の内外側方向の安定化に内側広筋の活動が寄与していることが明らかとなり，昇降動作の理学療法ではこれらのことに考慮して行う必要がある。