Chronic pain affects 116 million people, that is more than the total affected by cardiovascular disease, cancer, and diabetes combined. Chronic pain has at least as large of a negative impact on quality of life as any other chronic disorder, and in the United States alone, the cost of chronic pain exceeds $635 billion per year. Interventions that effectively manage chronic pain are becoming increasingly important as the elderly population, who often suffer from osteoarthritis and low back pain, rises. Pain sensitivity and tolerance are impacted by a variety of affective factors. The laughter therapy is one of the most discussed and often controversial strategies for the management of pain. There are some preliminary uncontrolled studies reporting that pain tolerance is increased acutely with humor and laughter. Accordingly, the primary aim of the present study is to investigate the effect of a highly controlled intervention with a comedy video on pain tolerance and compare it to a control of watching a documentary video. Quantitatively measuring laughter with a chest stress-strain gauge during the interventions will allow the investigators to look for a possible dose response relationship. The investigators will use the pain and soreness felt from delayed onset muscle soreness (DOMS) in healthy subjects to simulate the condition of individuals suffering from chronic pain. This study will serve as a precursor to eventual studies specifically on individuals with chronic pain. If it can be proven that pain tolerance is increased in a healthy population than it is possible the intervention will have a greater affect in the chronic pain population.

Using healthy subjects with delayed onset muscle soreness allows the investigators to easily recruit and control for other diseases or disorders that may accompany a chronic pain individual.

There have been a number of different techniques used to assess pain tolerance. The modes of stimulating pain used in previous studies of laughter and humor on pain tolerance remain controversial. These studies utilized the cold pressor test and the inflation of a blood pressure cuff to elicit pain. Both of these methods are known to elicit marked cardiovascular responses along with the pain responses. An important part of the pain regulatory process in humans is that there is a functional interaction between the cardiovascular and pain regulatory systems. The brain regions underlying control of the cardiovascular system are known to overlap substantially with those that contribute to anti-nociception. Accordingly, it is difficult to determine how much of the pain tolerance is affected by cardiovascular reflexes. Thus, the secondary aim of the present study is to test how much cardiovascular responses will be elicited by a variety of methods of eliciting pain (pumping up a blood pressure cuff, the cold pressor test, and the application of blunt force on muscles).

The application of blunt force will be used to elicit pain without causing a systemic response involving cardiovascular reflexes which is seen in the cold pressor and inflation of a blood pressure cuff. The investigators believe these vast cardiovascular responses may cause pain tolerance to not be truly measured. It has been inferred that blunt force applied within a few seconds to a local, specific spot on the quadriceps will not stimulate a systemic and cardiovascular response and thus the pain tolerance measurement will be more accurate if independent of cardiovascular responses. Pressure and force application is widely used as an experimental pain stimulus, but it has not been utilized in the context of laughter and pain.