“For bodily exercise profiteth little: but godliness is profitable unto all things, having promise of the life that now is, and of that which is to come.” 1 Timothy 4:8.
There are many benefits to being active exercising. Bible says that exercise “profits for a little while,” meaning in this physical life. Exercise is secondary in importance to developing a godly, spiritual character, which will profit for eternity. Physical exercise will keep the body in a healthy condition for a longer period of time. Exercise s indispensable to the health of every organ. If one set of muscles is used to the neglect of others the living machinery is not being worked intelligently. When physical exercise is taken the circulation is quickened. The heart receives blood faster and sends it to the lungs faster. The lungs work more vigorously, furnishing a greater amount of blood, which is sent with stronger power through the entire being. Exercise gives new life and strength to every part of the body. The nerves gain or lose strength in accordance with the way in which they are treated. If used too long and too severely, they are overtaxed and weakened. If used properly, they gain strength.
In order to have health, equilibrium of action must be maintained. The mind must harmonize with this or the benefits are not realized. If physical exercise is regarded as drudgery, if the mind takes no interest in the exercise of the different parts of the body (the benefits will not be realized). The mind must be interested in the exercise of the muscles. 
What you need is conditioning exercise. This is the type of exercise that will gradually increase your endurance. Use the following three guidelines to help you gauge your personal exercise intensity:
#1: Learn what your safe ten-second pulse rate for your age should be during exercise. Learn how to count your ten-second-pulse beat and exercise up to that degree.
# 2: Exercise to the intensity that you are barely able to carry on a conversation with someone as you exercise.
#3: If you should develop chest pain during exercise, stop at that point. Follow the advice of your physician. Exercise a minimum of 20-30 minutes at the peak of endurance daily if at all possible, at least every other day. The body forces seem to “escape” from good condition rather easily. 
How to start a walking routine: 
First of all, start out slow and easy. Just walk out the door. For most people this means head out the door, walk for 10 minutes, and walk back. That’s it? Yes, that’s it. Do this every day for a week. If this was easy for you, add five minutes to your walks next week (total walking time 25 minutes). Keep adding 5 minutes until you are walking as long as desired.
WATCH your posture. Walk tall. Think of elongating your body. Hold your head up and eyes forward. Your shoulders should be down, back and relaxed. Tighten your abdominal muscles and buttocks and fall into a natural stride.
Be sure to drink plenty of water before, during, and after walking. Incorporate a warm up, cool down and stretches into your routine. Start your walk at a slow warm up pace, stop and do a few warm up / flexibility drills. Then walk for the desired length of time. End your walk with the slower cool down pace and stretch well after your walk. Stretching will make you feel great and assist in injury prevention.
The toughest thing about starting a fitness program is developing a habit. Walking daily will help (a minimum of 5 days a week is a good goal). You should walk fast enough to reach your target heart rate , but you should not be gasping for air.
After you have formed the habit you will want to evaluate your program and your goals. Here are some general guidelines:
If you are walking for the general health benefits try to walk 30 minutes a day, most days of the week, at a “talking” pace. (Talking pace means you have elevated breathing, but you can still carry a conversation.)
To improve cardiovascular fitness you should walk 3 to 4 days a week, 20 to 30 minutes at a very fast pace. At this pace you are breathing hard but not gasping for air.
If you are walking for weight loss you should walk a minimum of five days a week, 45 to 60 minutes at a brisk pace.
- Manuscript Releases, Vol. 10, E.G. White p. 57
- Medical Evangelist John R. Cofer of Gospel of Health Ministry
- Extracted from The Walking Site: http://www.thewalkingsite.com/beginner.html
- to determine your target heart rate, please visit: http://www.thewalkingsite.com/thr.html