48. Exercise and Stress. Many studies have shown that people who engage in any exercise have improved mental health over those that never exercise. In particular, even a small amount of exercise seems to confer some resilience to stress. Most of these studies, by necessity, have been observational studies. A recent experiment with mice moves us one step closer to determining a causal association. In the study, mice were randomly assigned to either an enriched environment (EE) where there was an exercise wheel available or a standard environment (SE) with no exercise options. After three weeks in the specified environment, for five minutes a day for two weeks, the mice were each exposed to a "mouse bully"-a mouse that was very strong, aggressive, and territorial. At the end of the two weeks, the mice in the SE group exhibited maladaptive, depressive-like, and anxiety-like behavior across a wide spectrum of activities. This was not true of the mice in the EE group; they behaved similarly to mice that had never had the stress-inducing bully experience. In particular, one measure of mouse anxiety is amount of time hiding in a dark compartment, with mice that are more anxious spending more time in darkness. The amount of time spent in darkness during one trial is recorded for all the mice and is shown in the table below. Test to see if mice that have spent time in an enriched environment with options for exercise spend significantly less time in darkness after a stress-inducing experience. Note here the pvalue of 1.714 is 0.05

Do mice from an enriched environment spend less time in darkness

Environment time in darkness (seconds)

Enriched	359	280	138	227	203	184	231
Standard	394	477	439	428	301	488	454

Enriched environment _EE = 231.7 S_EE = 71.2 n_EE = 7

Standard environment _SE = 438.7 S_SE = 37.7 n_SE= 7