Exercise can help us sleep better and reduce our risk for chronic disease—but does it matter when you do it?
New research on mice from the University of California, Los Angeles’s Brain Research Institute suggests that exercising during the daytime can improve your sleep and reduce your risk for health problems that are associated with a
disrupted internal clock, like fatigue during the day, difficulty sleeping, weight gain, and dysfunction of the cardiovascular and immune systems. What they did not find, as some media outlets reported, is that the afternoon is the best time to exercise in order to reap these benefits.

Researchers observed several groups of mice running in their wheels. Some were otherwise healthy and some were bred to have a malfunctioning internal clock, or circadian timing system. Some mice could run whenever they wanted, while others only had access to the wheel at the mouse equivalents of morning and afternoon (they’re nocturnal). Exercise improved the functioning of the internal clock in all of the mice, but in the mice with “broken” clocks, the effect was more pronounced in the afternoon.


Lead author Christopher Colwell, Ph.D., who has studied circadian rhythms for 30 years, says that our brain’s internal clock governs most aspects of our behavior and physiology by telling our cells what time it is and what they should be doing, like maintaining organ function (daytime) or going into repair
mode (nighttime). Aging, nervous system diseases, and exposure to artificial light at night can all disrupt our circadian rhythm and, he says, “disruption of the clock has profound influence throughout the whole body.”


Colwell says this study raises the possibility that there may be a difference in how exercise in the morning versus the afternoon affects the clock in humans, but he’s not aware of any literature on that premise.


“I’ve been getting some emails from people who exercise in the morning and they feel great and they’re saying ‘Well, should I change that?’ Absolutely not,” he says.


“Right now, we feel comfortable saying that exercise during a human’s daytime would be beneficial, while the same exercise during the normal sleep time would be disruptive to these rhythms.”


This study, which appears in the Journal of Physiology, did not
examine the effects of late-night exercise, but unpublished results from Colwell’s lab show that working out at the equivalent of 11pm disrupts the clock.


Colwell says that sweating in the morning and late afternoon and maybe even the early evening are perfectly fine, but he says, “I would caution, as I have observed anecdotally, that if your only option is exercising at midnight, you might want to skip it that day.” It can affect your sleep and throw off the
clock: We get sleepy when our internal body temperature starts to decline and vigorous exercise causes a spike in core temperature, which delays the process.

via Women's Health Magazine

Question:
Are elliptical machines better than treadmills for basic aerobic workouts?

You can get an effective aerobic workout with both an elliptical machine and a treadmill. In general, you can let your fitness goals determine whether you choose an elliptical machine or a treadmill — or a different piece of exercise equipment.
However, elliptical machines might offer some advantages over treadmills. For example: 

• Using an elliptical machine can be less stressful on your knees, hips and back than is running on a treadmill. Walking on a treadmill, however, exerts about the same force as using an elliptical machine.


• Unlike treadmills, some elliptical machines are equipped with movable upper body handles or poles, similar to ski poles. These allow you to exercise both your arms and your legs.


• Most elliptical machines can be pedaled in reverse, which allows you to work your calf and hamstring muscles a bit more than does forward motion.

Using an elliptical machine is generally considered low impact. An elliptical machine might be a good alternative to jogging, whether on a treadmill or outside. An elliptical trainer shouldn't cause knee pain if you're using it correctly. You may experience knee pain, though, if you have an underlying knee problem, such as degenerative arthritis. With certain knee injuries, using a stationary bike might be a better option than using an elliptical machine. Talk to your doctor about what exercise is right for you if you have any injuries or health concerns.


And what if you're training for a 5K run or other road race? A treadmill is probably a better tool to prepare you for running events. But even if running is your main aerobic fitness activity, cross-training with an elliptical machine or other low-impact exercise equipment can help keep you fresh and prevent overload injuries.


If you use an elliptical machine, remember to maintain good posture to help ensure the most effective workout. Keep your shoulders back, your head up and your abdominal muscles tight. Look forward, not down at your feet. And don't lean on the handles — let your lower body support your weight.

from Edward R. Laskowski, M.D.