The effect of physical exhaustion on gait stability in young and older individuals.

Fatigue directly affects key features of the sensorimotor system which disorganizes voluntary control of movement accuracy. Local dynamic stability of walking is considered a sensitive measure for neuromuscular performance. To gain greater insight in the role of fatigue in motor behaviour in older and young adults during walking, the current experiment analyses gait patterns of healthy young but maximal fatigued individuals and gait patterns in submaximal fatigued older adults. Ten young and 18 older subjects performed a bicycle incremental exercise test on a cycle ergometer. In young subjects, the incremental test was performed until total physical exhaustion. In older subjects, the test was performed until submaximal fatigue. Prior to and after the test, the participants walked for 2.5min on a treadmill. Based on linear acceleration data of the trunk, local dynamic stability was assessed. Student's t-test was used to check if differences are statistically significant. In young individuals, we found a significant decrease in the finite-time maximal Lyapunov exponents between unfatigued walking and maximal fatigued walking. In older participants, significant increases in the finite-time maximal Lyapunov between unfatigued walking and submaximal fatigued walking were observed. The results indicate that (1) young and sporty subjects become more stable after having passed a maximum cardiopulmonary exercise test on a cycle ergometer while (2) older individuals walk less locally stable in a submaximal fatigued condition. Older cohorts might show a higher fall risk when they are physically fatigued.