A limitation of this study is that there was no control group who did not undertake the exercise programs, which could have provided more generalizable results. Focht and Koltyn (2009) reported that pain perception decreased after as little as 1 minute of exercise, and that it didn't matter if the exercise was done in the morning or evening. However in an assessment of pain perception 15 minutes after the exercise, pain sensitivity was reported to have returned to normal levels. Another limitation is that the participants were trained and conditioned men, and there was no testing of untrained men, unconditioned men, also affecting the generalisablity. Droste, Greenlee, Schreck and Roskamm (1991) and Koltyn, Wertz, Gardner and Nelson (1996) found that pain perception was reduced after high intensity episodes of running and cycling. However, this too cannot be generalizable because not everyone has the ability to undertake such high intensity aerobic activity. Similarly, Tesarz et al. (2012) reported that physical exercise is associated with specific alterations in pain perception, but it was also found that pain perception was lower in athletes when compared to non-athletes. Scheef et al. (2012) also found that pain perception was much lower in trained athletes when compared with untrained athletes. They added that this is due to the brain is at less sensitive state after the completion of endurance exercise. A major difference of this study is that they realised not everyone can complete high intensity exercise and that not everyone is a trained athlete. Therefore they administered mild aerobic exercise to both athletes and non-athletes. They found that in both groups, pain perception was reduced, concluding that physical exercise can be used to alter pain perception, particularly in patients with chronic pain states. Sjögren (2005) also tried to alleviate this athlete/non-athlete inconsistency.
