Pain perception after running a 100-mile ultramarathon.

Abstract

To determine if pain perception is affected by an extreme bout of exercise that causes ongoing exercise-related pain. Repeated-measures design. Pre-race registration area and finish area of an endurance race. Twenty-one competitors in the 2005 Western States 100 Mile Endurance Run and 11 control subjects who were assisting at the race but not running. Not applicable. Overall pain and pain ratings on a pressure pain test before and after the event. Mean overall pain +/- standard deviation on a 100-mm scale increased (P<.05) from 3+/-6mm before the run to 39+/-28mm after the run among the runners. The faster runners showed a mean reduction (P<.05) in pain ratings after the race of 15+/-20mm (on a 100-mm scale), whereas there was no change for the slower runners and controls. Findings were confirmed by model-based analysis. The faster runners in a 100-mile (161-km) running race experience a modest temporary reduction in pressure pain perception that does not appear to be augmented by ongoing pain related to the exercise. The lack of a reduction in pain perception among the slower runners may be because an extreme bout of exercise of this nature can "exhaust" the systems responsible for exercise-induced analgesia in all but the most well-trained of runners, or that these systems were not activated because the slower runners were unable to maintain a high enough exercise intensity during the later stages of the race.