From sports medicine standpoint, the best time to exercise is evening. If you are not committed as much as you think you should be, then morning sessions are good for you to put you in a discipline to exercise. Moreover, morning exercise may ease the tension and anxiety, boost your energy level, and elevate your mood. However, overall, the best time to exercise is evening for the following reasons:
1) The risk of back injury is lower in the evening sessions. The main component of an intervertebral disc is water (up to 80%). During the course of a day, physical activities reduce the height and volume of discs by about 20% by squeezing some water out of them due to compression and they lose a tiny bit of their heights. During the night, when the spine is relatively unloaded, swelling pressure of the discs sucks in water from surrounding tissues, causing them to get fully rehydrated in the morning. This is why young people are slightly taller in the morning than at night!
Since the discs are swollen with fluids in the morning (within 3 hours after waking up), exercise in the morning especially if it is associated with rapid and awkward bending movements could cause discogenic back injury. But in the evening, the discs are dehydrated, leading to loss of disc height, which slackens the intervertebral ligaments and fibers of the discs. Therefore, they resist exercise – induced bending movements less, reducing the incidence of back injury. The common experience that it is easier to touch your toes in the evening comes from the fact that intervertebral ligaments have more slack in the evening.
2) Evening sessions release more hormones than morning sessions. Exercise stimulates the release of many hormones including, but not limited to, growth hormone (GH), anabolic hormone (testosterone), and irisin. The reason that you feel so good after an exercise session is mainly due to the release of hormones. According to few studies, evening exercise stimulates the release of hormones more than morning exercise. The exact mechanism is not clear. However, it is attributed to lactate threshold. It is an exercise level at which lactic acid begins to accumulate in the blood. In other words, it is when the production of lactic acid exceeds its clearance. Subsequently, the accumulation of lactic acid in the blood triggers the release of hormones. Lactate threshold can be achieved in the evening sessions much easier than morning sessions.
Now, you know what the best time to exercise is and why.
Abazar Habibinia, MD, DFN
Executive Director of The Canadian Academy of Sports Nutrition
Updated on November 11, 2018