This is shared by an 85 years old healthy man who is active and is a chi kung teacher. Today he drives around and is very mobile and active after taking up chi kung.
According to him, the best time to exercise is during 7am to 10am.
He said that many people may think that exercising very early in the morning is good- but in the early hours, the body may absorb moisture and dew from the air during workouts. It causes excess ‘wind-dampness’ that would eventually lead to arthritis. Of course, between open air and air conditioned, it is better to exercise in open air too.
And night time, it is not advisable as most of us would want to bathe after workout- and bathing right after workout or at night is no good for our health. Furthermore, the night air is more “yin” / cooling and exercising with open pores (worst if done in air conditioned places) would cause the pores to absorb the moisture from the air or the coldness from the air-con. Years down the line, it will result in joint pain and arthritis.