Long-Term Effects and Impressions of Minimal Footwear in Older Adults.

Introduction: Foot pathologies can lead to difficulty walking and falls in older adults. Intrinsic foot muscles contribute to the structural support and alignment of the foot and provide somatosensory input from the ground. Minimally cushioned footwear may naturally strengthen intrinsic foot muscles and enhance sensory input to the foot; however, these effects are largely unknown in older adults. Further, there is little evidence regarding the prescription of minimal footwear and the perceptions of this footwear by older adults.

Methods: Twenty-four adults age ≥65 volunteered to use minimal footwear for prescribed times during daily activities for 16 weeks. The cross-sectional area (CSA) of 5 intrinsic foot muscles was measured using ultrasound imaging at baseline, 8 weeks, and 16 weeks. Semi-structured interviews were recorded regarding participants' impressions of the footwear, the progressive wear schedule, the footwear's effects on orthopedic-related pain, balance, and foot awareness/sensation.

Results: Across the cohort, there was no significant difference in CSA of the 5 muscles after 16 weeks of minimal footwear use. Thirteen participants had clinically meaningful increased CSA of the abductor hallucis muscle (Abh). These positive responders had no significant differences in age, grip strength, foot structure, or fall risk scores compared to participants with little to no CSA change. Interview results indicated a generally positive experience with minimal footwear for 68.1% of the cohort. A large percentage of the cohort reported no difficulty with the progressive wear schedule (77.2%), no aggravation of preexisting conditions and no new pain (77.2%), improved balance (63.6%), and improved foot awareness/sensation (72.7%) with minimal footwear use. The progressive wear schedule was perceived as inconvenient by some in the first few weeks (22.8%), but resulted in mild to no adverse effects when followed as prescribed.

Conclusion: Sixteen weeks of progressive minimal footwear use in older adults did not lead to changes in intrinsic foot muscle CSA; however, half of the cohort had clinically meaningful increased CSA in the Abh muscle. It is unclear what individual qualities were associated with this positive response. Older adults reported generally positive experiences with minimal footwear with self-reported improvements in balance and foot awareness/sensation. The wear schedule may have been too conservative or not long enough to produce foot muscle hypertrophy, but subjective reports suggest beneficial neuromuscular adaptations and sensory changes occurred. Future research may need a greater length of time and larger samples to further determine the effects of long-term minimal footwear use in older adults.