The role of the plantar intrinsic foot muscles in gait and balance – and their trainability – in older adults in the context of fall prevention

Falls in older adults are a growing problem. Due to population aging and the increase in chronic conditions, more and more older people are at risk of falling. A fall can have serious consequences, such as fractures, loss of independence, or even premature death. Therefore, effective fall prevention is essential. It is well known that exercise programs aimed at improving walking and postural balance help reduce the risk of falling. However, in existing exercise programs for fall prevention, the short foot muscles – located in the foot sole – often receive little attention, even though these muscles seem to play an important role in walking and balance. The overall aim of this doctoral research was therefore to improve fall prevention by gaining insight into the trainability of the intrinsic foot muscles and their role in walking and balance in older adults. The research consisted of consecutive steps leading up to an intervention study. First, we examined whether we could reliably measure foot muscle size — an indicator of the muscles’ level of training — using a portable ultrasound device. This turned out to be true. Next, we reviewed existing scientific evidence. This revealed that foot muscle training likely benefits walking and balance, but that high-quality research in older adults was still lacking. We then compared specific foot exercises, such as toe spreading, with more functional exercises, such as standing or walking on the toes. Functional exercises appeared to activate the foot muscles just as well, or even better, and are often easier to perform. Finally, we conducted an intervention study among community-dwelling older adults with a potentially increased risk of falling. They followed a twelve-week training program that included both specific and functional foot exercises. Participants trained at home five times per week, with one session per week supervised by a trainer. The research produced interesting findings. First, the trainability of the foot muscles was confirmed, as we observed that the muscles became larger and stronger. Contributing factors were the participants’ high adherence to the exercises and the good fit of the training program with their abilities. Second, the results showed that participants felt more confident while walking and were less worried about falling. At the same time, we did not observe changes in balance or walking speed in the motion laboratory, although many participants reported feeling more stable and confident in their physical abilities in daily life. In conclusion, training the foot muscles can be a valuable addition to existing exercise programs for older adults. This is particularly relevant for older individuals who feel insecure or have concerns about falling. Future research should examine whether this addition indeed leads to the desired outcomes by measuring improvements in real-world walking performance — for example, using wearable sensors — and by monitoring the actual occurrence of falls.