Pressure pain tolerance at different sites on the quadriceps femoris prior to and following eccentric exercise.

Downhill running, particularly for the untrained subject, is a mode of eccentric exercise that produces delayed-onset muscle soreness (DOMS) in the quadriceps femoris muscle which is maximal between 24 and 72 h after the exercise. It is not clear whether sensitivity to pain is uniform over the surface of the muscle, or whether some locations become more sensitive following eccentric exercise. The purpose of this investigation was to compare pressure pain tolerance (PPTO) at various sites on the quadriceps femoris muscle on 2 days prior to exercise, immediately after, and at 24, 48 and 72 h following a bout of eccentric exercise. Fifteen untrained female subjects performed a 40 min downhill run on a motorized treadmill with a gradient of -12%, where running speed was adjusted to elicit a heart rate of approximately 60% of age-related maximum heart rate reserve, and were measured for PPTO at seven sites on the right thigh. Sites were visited sequentially three times and repeated on each of 6 days. Pressure pain tolerance as an index of tenderness was determined using a strain gauge algometer. Two sites were close to the distal myotendinous junction, three sites were located on the mid belly of the muscle and two sites were located at the proximal myotendinous junction. There was a significant difference (p<0.01) in PPTO between muscle sites prior to eccentric exercise (Days 1 and 2), and a significant difference between sites following eccentric exercise (p<0.01). Sites close to the distal and proximal myotendinous junction were most sensitive to pain (p<0.01). There was no difference in PPTO at any site across the belly of the muscle. These results suggest that the belly of the quadriceps femoris is the most suitable area for measurement of PPTO.