Laughter and health outcomes
A more recent attempt at documenting the effect of laughter on muscles used a more sophisticated technique (4). Based on Paskind’s earlier work that indicated a period of muscular relaxation follows laugh- ter, this study examined how laughter and several other respiratory movements influenced spinal motor excitabil- ity, as measured by the Hoffmann reflex (H-reflex). The H-reflex is a clinical method of measurement, similar to tapping the patella to elicit a deep tendon reflex. However, the H-Reflex is different from a tendon tap in two respects. First, the stimulus is an electrical shock to sensory fibers coming from muscle spindles rather than a mechanical stretching of those receptors. Second, the response is recorded using an electromyographic (EMG). The H-Reflex method is a preferred measure- ment because the stimulus is better controlled, the response can be measured more precisely, and changes in muscle stretch receptor sensitivity do not affect the results. When looking at the H-reflex, increased twitching indicates increased spinal cord excitability. Thirteen healthy volunteers doing a variety of 10 different tasks (including laughter, simulated laughter and various respiratory movements) participated in this study. The results indicated that laughter resulted in H-reflex suppression. H-reflex percentage differed between the neutral task (79.4 16.1%), true laughter (43.7 17.9%)
and simulated laughter (66.6 24.3%). Coughing resulted in H-reflex suppression, but not as deeply as
laughter. During the other H-reflex increased compared from this study indicate that
respiratory maneuvers, the to the neutral task. Findings both laughter and simulated
laughter decreased spinal true laughter evoked more
excitability, and that depression than simu-
lated laughter, which depress the H-reflex,
suggests that mirth on its own can leading to the post-laughter muscle
In addition to changes in muscle tone, there is evidence that laughter leads to changes in respiratory function. Fry’s work demonstrates that laughter leads to episodes of sharply sporadic deep breathing (5). However, these breathing changes do not appear to significantly improve oxygen saturation levels, at least in healthy individuals (6). Of course, with healthy subjects, their normal oxygen saturation rate would be expected to be near or at 100%. It may be that there is little to no room for improvement in this group. It would be interesting to learn how laughter influences oxygen saturation rates in a more compromised population, such as persons with chronic lung disease.
Fry’s later work supports the theory that laughter can lead to acute changes in cardio-respiratory functioning. Hard laughter leads to increased heart-rate, respiratory rate and oxygen consumption, which is indeed similar to changes seen with aerobic exercise. However, these changes are in effect only during periods of intense laughter, which are very difficult to sustain for any
length of time (7). This makes it unlikely that laughter can be regarded as a realistic substitute for aerobic exercise.
Laughter, Stress and Anxiety
According to James–Lange theory of emotion and later theories (8), all intense emotions, regardless of their content, lead to activation of the sympathetic nervous system. This was tested in an investigation by Averill, in which three groups of men were exposed to either a humorous movie, a sad movie or a neutral movie (9). Physiological responses were determined by heart rate, blood pressure, respiratory rate, skin temperature and galvanic skin response. Both the humorous stimulus and the sad stimulus produced significant increases in galvanic skin response (GSR), indicating activation of the sympathetic nervous system. However, while exposure to a sad stimulus caused significant increases in blood pressure over the control group, the blood pressure of those exposed to humor remained stable, even though the GSR reading of both groups would indicate activation of the sympathetic nervous system (9). The results of this study suggest that while a humorous stimulus can activate the sympathetic nervous system similar to some stressors, it may also help buffer some of the negative effects of sympathetic activation upon blood pressure.
To determine if humor can be beneficial in the treatment of anxiety, the impact of a humorous stimulus upon anxiety and heart rate was investigated during a stressful waiting period (10). A sample of 53 college students was told that they would receive a shock after a brief waiting period. Subjects in the experimental group listened to a humorous tape while waiting to receive a shock, the placebo control group listened to a non- humorous tape during this waiting period, and non- intervention control group did not listen to a tape. Subjects in the humor group reported decreased anxiety during the anticipatory period (P50.05), while those with the highest level of sense of humor (measured by SHRQ) had the lowest reported anxiety (P50.01). However, the heart rate of the three groups were not significantly different, and all three groups experienced increased heart rate during the waiting period (P50.001). The authors concluded that the effect of humor may be primarily cognitive, rather than having a physical stress reduction capability, because heart rate was not significantly different among the groups (10). However, as the investigations reported above indicate, laughter tends to increase heart and respiratory rate in itself, and therefore heart-rate may not have been the best physiological measure of reduced anxiety for this experiment. Also, it would have been interesting to see what results this intervention had on GSR’s and blood pressure, as it