TRX suspension vs Swiss-ball core training for core-muscle endurance and static/dynamic balance in overweight inactive women: a randomized trial

Purpose Prolonged sitting and physical inactivity are key risk factors for trunk-muscle weakness, impaired balance, and low-back pain in overweight women. Although unstable-surface training is widely prescribed, head-to-head comparisons between TRX suspension and Swiss-ball exercise are limited. We compared these modalities for effects on core-muscle endurance and balance. Methods Thirty overweight, inactive women (30 ± 5 years; BMI 27.3 ± 1.6 kg·m⁻ 2 ) were block-randomized (1:1) to 8 weeks (3 sessions/week) of TRX or Swiss-ball training using five matched exercises at Borg RPE 13–15 on the 6–20 scale. Outcomes were trunk-extensor (Biering-Sørensen), trunk-flexor (60° curl-up), and trunk-lateral (side-bridge) endurance; static balance (Stork test); and dynamic balance (Y-Balance composite). Baseline-adjusted ANCOVA compared post-intervention scores between groups. No non-exercise control was included; therefore, within-group changes cannot be interpreted causally. Results Twenty-eight participants completed the study (14/group). Participants in both groups demonstrated improvements following training on all outcomes (all p < 0.001); however, without a non-exercise control group, practice/retest effects and other non-specific factors cannot be excluded. After baseline adjustment, TRX showed larger uncorrected between-group differences than Swiss-ball in trunk-extensor endurance (adjusted Δ = 9.1 s, 95% CI: 1.9 to 16.3, p = 0.015) and trunk-lateral endurance (adjusted Δ = 4.2 s, 95% CI: 0.2 to 8.2, p = 0.041). These findings did not survive Bonferroni correction for five primary comparisons (adjusted p = 0.075 and 0.205, respectively). Trunk-flexor endurance, static balance, and dynamic balance did not differ between groups (all adjusted p ≥ 0.48). Conclusion TRX and Swiss-ball training were associated with within-group improvements in core endurance and balance in overweight, inactive women. TRX showed larger exploratory posterior-chain gains than Swiss-ball, but these differences did not survive correction for multiple comparisons. Because no non-exercise control group was included, causal inference is not possible; findings should be interpreted as associations and considered exploratory.