Investigating whether HRV would be a more sensitive measure than heart rate during tasks that have combined physical and cognitive demands would be of benefit, as may be investigating any associations with aerobic fitness. To meet this objective, relationships between HRV and HR, and load carriage performance, are of interest as not only is aerobic fitness strongly associated with load carriage performance, it is a strong predictor of selection success and is often integrated with tasks imparting cognitive demands (e.g., navigation).