Exercise-Induced Fatigue

All participants completed an exercise session on an instrumented treadmill (h/p/Cosmos Mercury 4.0). Older individuals wore a safety harness attached to an overhead suspension system. Starting with a treadmill speed of 1.33 m/s, participants walked at faster speeds until they were forced to break into a jog to keep up with the treadmill speed. The treadmill speed used during fatiguing bouts was the fastest speed observed in the period while walking was maintained³⁰. This determination period doubled as a warm-up.

For the walking task, three 5-minute trials were performed. Fatigue during walking was elicited by increasing the treadmill incline in increments of 2⁰ (from level) every minute to a maximum of 8⁰. Participants were allowed to rest for five minutes between each the three fatiguing periods of walking. Immediately following this exercise routine, subjects were reassessed for reaction times, balance, strength, gait, and falls risk.

During the treadmill walking test, both heart rate and RPE values were attained. Heart rate (HR) was recorded using a Polar® monitor (Polar, Inc.). Selected heart rate measures (i.e., maximum heart rate and overall change in HR (maximum HR − baseline HR)) were used to determine the physiological effort for the walking tasks. A rating of perceived exertion (RPE) was obtained at the beginning and end of each fatigue walking trial using a modified Borg 10-point scale (1 as “little or no exertion” to 10 as “maximal effort”). The final RPE and the average change in RPE (i.e. RPE at the end of each fatigue trial minus the baseline RPE) were determined.