Machine-based Resistance Training Including Calf Raises versus Unstable Balance Training on Fall-related Functional Outcomes in Middle-aged Women: A Pilot Randomized Controlled Trial

Purpose: Balance-challenging exercise has stronger evidence for fall prevention than resistance training alone, but most resistance-training protocols evaluated to date have omitted ankle plantarflexor exercises.This pilot randomized controlled trial examined the feasibility of a full-scale trial comparing machine-based resistance training (MRT) including calf raises with unstable balance training (UBT), and explored preliminary change patterns in fall-related functional outcomes among middle-aged women.Methods: Ten women aged 45-64 from Seoul were randomized 1:1 to MRT (n=5) or UBT (n=5); one UBT participant withdrew before baseline (n=9 analyzed).Both groups completed 12 sessions over 6 weeks (60 minutes, 2×/week).MRT used six machine-based exercises with calf raises; UBT used five unilateral unstable-surface exercises.Feasibility (recruitment, retention, attendance, adverse events), body composition, balance (Timed Up and Go, single-leg stance, Y-balance), and isokinetic knee strength were assessed.Within-group change was described using Hedges' g as exploratory signals.Results: Feasibility was supported by 90% retention, ≥ 90% attendance, and no serious adverse events.Withingroup patterns showed MRT with a larger Y-balance change (g=＋1.60)and UBT with a larger Timed Up and Go change (g=-0.96).Both groups reduced body fat and improved knee-flexor total work.Single-leg-stance results were limited by ceiling effect (eyes open) and baseline-variance artifact (eyes closed).All effect-size estimates are exploratory; no between-group inference is warranted.Conclusion: A future non-inferiority trial appears feasible with approximately 35 participants per arm as an initial planning estimate, pending refinement of variance and incorporation of stratified randomization on baseline blood pressure.