Relationship between aerobic capacity, injury risk and tenure for new-hire delivery drivers

Over a 2-year study period, aerobic capacity was measured at time of hire for 1419 delivery drivers. Injury experience and tenure were then monitored for these new-hires during that same period. Number of strain injuries, time to first strain and time to termination were regressed on aerobic capacity adjusting for tenure. Statistically significant, monotonically changing relationships were found for all three outcome variables. A unit increase in aerobic capacity was predicted to result in a 3.7% decrease in injury rate and a 1.1% decrease in risk of termination. When age was included in the model for time to termination, aerobic capacity was no longer a significant predictor. The findings regarding injury experience and aerobic capacity support National Institute for Occupational Safety and Health recommendations that individuals should work at no more than 21-30% of their aerobic capacity. STATEMENT OF RELEVANCE: Knowledge of the nature of the relationship between aerobic capacity, injury experience and retention allows the ergonomist to determine whether there is a point of diminishing returns in intervention effectiveness for higher levels of aerobic capacity.