Mirthful Laughter and Muscle Soreness / Pain

The purpose of this study is first to investigate the effect of a controlled intervention with a comedy video on pain tolerance in a social setting while quantitatively measuring laughter in a young healthy population experiencing delayed onset muscle soreness. The comedy intervention will be compared to a control of watching a documentary. The second aim is to examine to what extent various methods of eliciting pain would cause physiological responses that confound the interpretation of a pain stimulus.

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.

The main study was conducted using a randomized controlled cross-over approach. Participants made three visits each for the two video watching interventions. The interventions were separated by a minimum of 1week as a washout. Each intervention included one day of inducing muscle soreness in one leg through eccentric muscle contractions; a second day of testing muscle soreness and pain tolerance and watching a 30-min video (either a comedy or documentary); and a third day of testing muscle soreness and pain tolerance again to see if the effects of the video viewing persisted the next day (i.e., 24 h after the video viewing).

The peak force is measured by using a force transducer and applying it to participants' quadriceps. Using data acquisition software the investigators can find the peak force applied.

Inclusion Criteria: Between the age of 20 and 40 Considered healthy Exclusion Criteria: Candidates that are on cardiovascular acting drugs. Candidates currently taking anticoagulants. Candidates that have chronic pain or other musculoskeletal injuries. Candidates with a body fat percentage less than 5%. Candidates with bleeding disorders or neurological disorders Raynaud's disease History of severe frost bite.

Lapierre SS, Baker BD, Tanaka H. Effects of mirthful laughter on pain tolerance: A randomized controlled investigation. J Bodyw Mov Ther. 2019 Oct;23(4):733-738. doi: 10.1016/j.jbmt.2019.04.005. Epub 2019 Apr 13.