7 to 9 a.m.: Heart rate increases, body temperature rises and adrenal hormones peak as the body gears up for the day ahead. More people over 65 suffer heart failure and stroke now than at any other time of day. The majority of all deaths, including suicide, occur.

9 to 11 a.m.: The body is least sensitive to pain and anxiety levels are lowest. Alertness peaks in late morning when body temperature is high.

Short-term memory is 15 percent more efficient and problem-solving abilities are sharper.

Noon: eyesight is sharpest.

One to two p.m.: Energy levels and alertness drop temporarily.

Three to four p.m.: The best time for athletics as muscle strength, body flexibility and aerobic capacity reach their peak. Long-term memory is significantly better. A second peak in the death rate occurs at 4 p.m.

Five p.m.: Blood pressure peaks. Taste and smell are sharpest.

Six to seven p.m.: The worst time of the day for dieters to eat -- more calories end up as fat due to fluctuations of body metabolism.

Eight to 11 p.m.: The brain hormones serotonin and adenosine shut down the electrical activity of some neutrons, causing drowsiness and sleep.

Midnight to three a.m.: Blood pressure, heart rate and stress hormones all bottom out. Heart attacks are rare, as are most deaths, because the body is in its most relaxed state.

Four a.m.: The body temperature drops to its lowest level of the day.

Industrial accidents are unusually high now. The body steps up its production of histamine, increasing wheezing attacks in asthmatics.