EFFECT OF UPRIGHT SITTING VERSUS CONVENTIONAL CORE EXERCISE ON REGIONAL POSTURAL ALIGNMENT IN UNIVERSITY STUDENTS: A SECONDARY ANALYSIS OF A RANDOMIZED CONTROLLED TRIAL

Abstract

Background: Upright sitting is widely recommended for postural health but has rarely been prescribed and monitored as an intervention. Whether it improves measured postural alignment more than conventional core exercise is unknown. Objective: To compare the effects of upright sitting, conventional core exercise, and their combination on regional postural alignment in university students with core muscle weakness. Methods: Secondary analysis of a three-arm, parallel-group randomized controlled trial. One hundred and twenty asymptomatic university students aged 18–25 years with core muscle weakness were allocated equally to upright sitting (Group A), conventional core exercise (Group B), or both (Group C) for four weeks. Frontal-plane alignment of the head, shoulders, pelvis, knees and feet was scored from standardised anterior and posterior photographs using the APECS photogrammetric application at baseline and four weeks, with lower scores indicating better alignment. Group-by-time interaction was assessed by mixed-model analysis of variance. Within-group change was tested by Wilcoxon signed-rank test and between-group change by Mann–Whitney U test with Bonferroni adjustment, with Cohen's d as the effect size. Results: All 120 participants completed both assessments. Groups were comparable at baseline in all five regions. Alignment improved significantly in every group in every region (all p ≤ 0.003). A significant group-by-time interaction was found for shoulder alignment (partial η² = 0.101), knees alignment (0.076), head tilt (0.066) and pelvic tilt (0.063). Upright sitting produced greater improvement than conventional exercise in head tilt (Z = 2.780, p = 0.006, d = 0.653) and greater improvement than combined training in shoulder alignment (Z = 3.415, p < 0.001, d = 0.813) and pelvic tilt (Z = 2.975, p = 0.003, d = 0.626). Conventional exercise produced greater improvement than upright sitting at the knees alignment (Z = 3.175, p = 0.002, d = 0.755). Feet did not differ between groups. Conclusions: Upright sitting improved frontal-plane alignment of the head, shoulders and pelvis more than conventional core exercise or combined training, while conventional exercise improved knees alignment more. Each intervention produced its largest effect in the regions it directly engaged, and postural benefit did not follow the pattern of muscular benefit reported for this trial elsewhere.