The best time to exercise is the time when it is most convenient for you.
Some early risers find that the early morning is the time they most enjoy their workout.
It can be a great start to your day. Others may find that rising out of bed at the crack of dawn is more of a hardship than an enjoyment and may have the tendency to stop their program altogether. The body will adapt to physical activity at any time of the day as long as it is performed on a regular basis. It is not dangerous to your health to exercise immediately after waking up but it may take a few minutes of activity for your muscles to warm-up and feel as loose as you might later in the day. A slow aerobic warm-up is recommended before stretching or getting into higher intensity activity.