The best time (for exercise) is usually in the morning when you first get up. Early exercises are least likely to become dropouts.
Measure your girth at the level of your navel with your stomach normally relaxed. Pull your stomach in as far as you can, and measure it again. Record both measurements. Do this once a month on the same date each month.
Unless you're working in a hot area, you shouldn't work up a sweat.
If you feel stiff or sore tomorrow, you did too much today.
To relieve stiffness: 1) Expose the stiffness or soreness to warm water. You can do this in a tub or shower. 2) Massage the stiff or sore area. This helps especially if done in the tub or shower.
Exercise 21: Fasten a piece of thread around your waist at the level of your navel. Fasten it so it's 2 to 4 inches smaller than your girth when you are normally relaxed. Pull your stomach in until your girth is as small as the circumference of the thread, and keep it pulled in to this size. Leave the thread there as long as possible, at least 4-5 hours.
This is a great way to remind yourself, every time you relax your stomach, to tighten your abdominals. The thread will tend to roll up and down your waist. To keep it in place, tape it to your skin at 6 to 8 spots around your waist.
This technique works best when you are wearing loose clothing.