People sleep significantly better and feel more alert during the day if they get at least 150 minutes of exercise a week, a new study concludes. A nationally representative sample of more than 2,600 men and women, ages 18-85, found that 150 minutes of moderate to vigorous activity a week, which is the national guideline, provided a 65 percent improvement in sleep quality. People also said they felt less sleepy during the day, compared to those with less physical activity. The study, out in the December issue of the journal Mental Health and Physical Activity, lends more evidence to mounting research showing the importance of exercise to a number of health factors. Among adults in the United States, about 35 to 40 percent of the population has problems with falling asleep or with daytime sleepiness. Increasingly, the scientific evidence is encouraging as regular physical activity may serve as a non-pharmaceutical alternative to improve sleep.  After controlling for age, BMI (Body Mass Index), health status, smoking status, and depression, the relative risk of often feeling overly sleepy during the day compared to never feeling overly sleepy during the day decreased by 65 percent for participants meeting physical activity guidelines. Similar results were also found for having leg cramps while sleeping (68 percent less likely) and having difficulty concentrating when tired (45 percent decrease).