The researchers mixed a certain plant lactic acid bacteria into the feed of the experimental rats. After the experimental rats ate the feed for 4 weeks, they continued to exert mental pressure sufficient to cause sleep disorders for two weeks, and then let the experimental rats pedal the wheel during the nocturnal activity period to test their activity. The results showed that the downward trend of the activity of the experimental rats extracted with the lactic acid bacteria was curbed, However, the rats in the control group who did not eat the feed containing the lactic acid bacteria had difficulty falling asleep during the day and lack of sleep, resulting in a significant decrease in their activity at night. 
In addition to pedaling the wheel, the experimental rats had no other activities at night
 the researchers believe that the intake of lactic acid bacteria can improve the sleep disorder caused by mental stress.