Exploring quadriceps activity variations in women: the role of seated posture during stair climbing

Adults in modern society spend most of their time in a sitting position. However, sitting for long periods of time can affect the length and sensation of the quadriceps muscle and negatively affect the performance of functional tasks required in daily life. In addition, it may have different characteristics according to sitting postures.

The aim of this study is to investigate the differences in quadriceps muscle activity during stair climbing and descending based on various sitting postures.

Thirty healthy adult women were classified into sitting upright (SU), sitting with legs crossed (SLC), and sitting with ankles crossed over knees (SAC). The muscle activities of the vastus medialis (VM), vastus lateral (VL), and rectus femoris (RF) were collected during climbing and descending the stairs three times each. After which a sitting posture was maintained for 15 min, the post-measurement was performed in the same way as the pre-measurement. One-way analysis of variance or Kruskal-Walli's test was used to check homogeneity between each group, least significant difference (LSD) was used for post-hoc testing. Paired-sample t-test or Wilcoxon signed-rank test was used to check before-and-after differences within the group. Repeated measures analysis of variance was used to determine between-group and within-group interactions.

VM muscles were significantly decreased after maintaining a sitting posture during descending stairs of SAC group (p = 0.047). In conclusion, this study indicates that maintaining a SAC sitting posture for a certain period causes a temporary decrease in muscle activity of the VM muscle during descending stairs. This provides important implications for early treatment to manage knee pain and strengthen quadriceps muscles in women. Future studies should focus on groups with patellofemoral pain syndrome or knee pain to better understand the impact of sitting posture on quadriceps activity.