Why do we need to sleep?

Why do I feel like the more I work out, the less sleep I need?

• I've noticed the more exercise I do, the less sleep I need. I work from 3pm-1130pm and when I wasn't seriously working out, go to bed at 2am and not wake up until 11am. Now if I go to sleep at 2am, I try to sleep till 10 but by 9am my body keeps waking me up. What is the reason behind this?

• Answer:

  It's not that you need less sleep, but rather the fact that your body may be stressed (physically) is what may be making you wake up earlier. A secondary question to yours may be "What is the quality of your energy levels upon waking up?" Also some things to consider: 1. What times are you exercising? If you are exercising right before you sleep (the time from you're done work, 11pm, until 1:30-2am), then it could be explained that you're stressing your CNS (central nervous system), which accounts for the reduction in overall sleep. Again, what is the quality of the energy levels upon waking? (A study done measuring exercise and sleep patterns in college athletes: http://www.amsciepub.com/doi/pdf/10.2466/pms.1966.23.3f.1203 From the study: "The fact that evening exercise produces a more disturbed sleep (more brief periods of wakefulness) suggests that it is a stressor, producing CNS activation opposing a more general (perhaps metabolic) effect of exercise tending to in- crease delta sleep requirements." ...with delta sleep referring to "...our deepest sleep, the point when our brain waves are least like waking. Consequently, it is most difficult stage in which to wake sleepers, and when they are awakened they are usually sleepy and disoriented. [http://web.mst.edu/~psyworld/sleep_stages.htm%5D) 2. If you are exercising before work, there is still a plausible explanation: You are exerting more energy throughout the day, and when it is time for sleep, your quality of sleep levels go up. Quality of sleep =/= quantity of sleep. (A study done to evaluate the relationship between average sleep quality versus average sleep quantity measuring health and well-being in college students: http://www.ncbi.nlm.nih.gov/pubmed/9226606) 3. What are your eating habits before you sleep? Generally speaking, a large influx of food would dramatically increase your insulin levels among a host of other hormones, and on the other hand a reduction or little eating overall may have the opposite effect, and it may in fact prevent you from receiving adequate sleep. -Miguel Aragoncillo http://www.miguelaragoncillo.wordpress.com