Alterations in pain perception after resistance exercise performed in the morning and evening

The purpose of the present study was to examine whether changes in experimentally induced pain perception after acute resistance exercise (RE) are influenced by the time of day that RE is performed. Twenty-one recreationally trained (>1 year of regular recreational RE participation) young men (mean age = 21 years) completed 2 acute RE sessions at different times of day. One RE session was performed between 6:00 and 8:00 in the morning, and the other was performed between 6:00 and 8:00 in the evening. The RE sessions consisted of completing 3 sets of 10 repetitions for 4 different exercises at 75% of each individual's 1 -repetition maximum. Assessments of pain threshold and pain ratings were obtained during exposure to an experimentally induced pressure pain stimulus before and after (1 and 15 minutes) each bout of RE. The results revealed that, irrespective of the time of day RE was performed, pain threshold increased significantly (p < 0.01) at 1 minute after exercise. Pain ratings were also found to be significantly (p < 0.01) lower at 1 minute after RE in both the morning and evening. It is concluded that acute RE results in alterations in the perception of experimentally induced pressure pain and that this hypoalgesic response is not influenced by the time of day that RE is performed. KEY WORDS acute exercise, diurnal variations, hypoalgesia, strength training