Development and evaluation of a core balance exercise program based on clinical electromyographic analysis findings

Introduction Core muscle activity and stability are essential for posture, balance, and mobility, particularly among older adults. However, conventional core exercises are often too strenuous or complex for older adults and are therefore unsuitable for individuals with age-related physical limitations. This study aimed to develop and evaluate the physiological efficacy of a low-intensity accessible core balance exercise (CBE) program. Method A seven-movement CBE program was developed through literature review, expert consultation, and pilot testing to select feasible movements and refine the exercise sequence. We conducted a cross-sectional clinical study across two visits at the Korean Medicine Hospital of Wonkwang University following Institutional Review Board approval. Twenty healthy participants (12 men and 8 women; mean age, 25.2 ± 2.9 years) were recruited through convenience sampling using hospital advertisements. All participants provided informed consent and were free of medical conditions that could interfere with exercise participation or surface electromyography (sEMG) assessment. Muscle activation of the bilateral rectus abdominis (RA), external oblique, erector spinae (ES), and gluteus maximus (GM) was measured using sEMG. Electrodes were placed according to SENIAM guidelines, sEMG signals were sampled at 512 Hz, band-pass filtered (20-450 Hz), full-wave rectified, and smoothed using a 126-sample moving window with 50% overlap. EMG amplitudes were normalized to the mean value of the central 3 s from two 5-s maximum voluntary isometric contraction (MVIC) trials obtained for each muscle using standardized manual testing procedures. Activation patterns were analyzed across movements and submotions, and inter-session reliability was evaluated using the intraclass correlation coefficient (ICC), together with bilateral correlation analysis. Results The CBE program elicited moderate muscle activation (mean MVIC, ∼30%) with certain motions—particularly CBE3 (one-leg tree flow) and CBE6 (grounding and opening flow)—eliciting high GM engagement (>60% MVIC). CBE5 (standing trunk rotation flow) was associated with the highest ES activation. A submotion-level analysis identified peak activation phases such as CBE3-3 (right trunk sweep; 96.7% MVIC in the GM) and CBE1-1 (skyward stretch; 79.4% MVIC in the RA). Repeated-measures ANOVA demonstrated significant differences in muscle activation among the seven CBE movements (all p < 0.01), with the largest movement effect observed for the external oblique muscle. Discussion The program demonstrated high test–retest reliability for five of seven movements. Most motions showed strong bilateral correlations for the RA and ES, indicating consistent bilateral muscle recruitment. The GM showed more variable activation patterns. Conclusion The CBE program elicited low-to-moderate core muscle activation with acceptable inter-session reliability, supporting its use as a standardized core balance exercise program for future clinical evaluation.