This study examined the effects of flat-soled footwear on toe function and muscle mass in middle-aged adults. In a two-month intervention study, participants aged 50 and older were assigned to either an intervention group that wore flat insole shoes or a control group that used standard commercial footwear. All participants maintained consistent dietary habit and activity level during the study. To assess functional outcomes, we used a custom-built toe-tapping sensor embedded in insoles, together with body composition measurements. The intervention group showed significant improvements in toe-tap frequency (36.8 vs. 30.4 taps, p < 0.05) and increases in limb muscle mass, compared to the control group. Statistical significance was confirmed using Mann-Whitney U test. The findings suggest that flat-soled shoes may enhance toe activation and maintain muscle mass, which are critical factors in preventing frailty. This accessible, non-invasive intervention may support locomotor function in aging populations. Further study is warranted to evaluate long-term benefits and broader applicability.