i did a little research of my own..looks like it is a controversial matter but this article is from cnn....
Experts disagree on ideal time of day to exercise
Doctor says late afternoon workouts best bet for bodyBy Stephanie Smith
CNN
Tuesday, January 13, 2004 Posted: 12:33 AM EST (0533 GMT)
(CNN) -- Whether trekking on a
treadmill or slicing through a pool, for many people, exercising in the morning is like drinking a cup of coffee. The early physical activity stimulates them and gives the day a strong start.
"I feel great after morning exercise," said Orlando Suarez, a 39-year-old director of special events in Los Angeles, California. "I feel very energetic, very clear. It's like I have a sustained
energy throughout the day."
But one neurologist is challenging the old convention of the morning workout. In fact, Dr. Phyllis Zee of Northwestern University has a different opinion about when is the ideal time to exercise.
"The best time to work out is in the late afternoon," Zee said. "The reason for that is your muscle strength is at its peak, its highest. You're going to be less likely to injure yourself. It's also a time when people are most awake and alert."
The science behind Zee's assertion resides with delicate rhythms of the brain called circadian rhythms. According to Zee, circadian rhythms explain why working out later in the day might be more productive and beneficial.
"One of the things that circadian rhythms does is that it determines when your best performance time is," Zee said. "Your ability to perform changes throughout 24 hours."
Circadian rhythms operate like an internal clock in the
body. Neuron signals are fired out by the hypothalamus [a region of the brain], controlling sleep patterns, blood pressure, even our moods.
"These are rhythms that are innate," Zee said. "They are in almost any organism, whether you are an animal or a plant, and they recur every 24 hours."
Circadian rhythms also control
body temperature, a key element of a more productive workout. According to Zee, by the afternoon,
body temperature is between one and two degrees warmer than in the morning, making muscles in the
body more supple and lowering the risk of injury.
Another circadian expert agrees.
"Maximum
body temperature happens between 2 and 4 p.m.," said Dr. Michael Vitiello, a professor of psychiatry and behavioral sciences at the University of Washington. "After that, [body temperature] starts to decline for most people.
"It all depends on whether you want to exercise in early afternoon or early evening. But we're not talking about a gigantic difference [from the peak period]."
Challenging popular notions
David Padron, a 28-year-old graphic designer in Fresno, California, finds that his afternoon workouts aren't only easier on his
body but also that his performance increases, too.
"I look forward to it all day," Padron said. "I feel more relaxed. In the afternoon, I have the
energy to lift 20 more
pounds than in the morning."
Some health experts recommend exercising in the morning because the
body's metabolism will get an early start at burning
calories and sustain that higher metabolic rate during the hours after.
But for one
fitness expert, that might not be enough of an argument for morning exercise.
"There is some evidence that morning exercise promotes more
fat burning than other times of the day, but the difference is so small that it really wouldn't matter," said Richard Cotton, an exercise physiologist. "And if you're going to exercise inconsistently in the morning, then it's not worth it at all."
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