How much is enough? Exercise, that is.

Staying fit, By Anya Petersen-Frey

It started out a few years ago with the guideline of 20 minutes three times per week. Then it changed to 30 minutes most days of the week. Just last year a new guideline was released suggesting that an hour a day was optimal. And what about the three short 10-minute periods spread throughout the day? Exercise. What should you do?

It's all about the goal. If exercise is new for you, starting with short 10-minute spurts throughout the day is good. The three 10-minute sessions can also be beneficial on the days that, due to work or personal circumstances, a longer workout is not possible. Thirty minutes of physical activity most days of the week is generally the minimum needed to promote good health. This means that you receive the health benefits that may reduce the risk of early mortality by as much as 50 percent. It is best to complete 30 minutes of moderate activity to get the most gains; the 10-minute mini-sessions are meant to be a short term alternative for the beginning exerciser or for those on a tight schedule some days of the week. The key to this method is "moderate" activity -- heart rate and breathing need to increase -- a gentle stroll won't hurt, but benefit will be minimal for long-term gain.

Since there has been an alarming increase in obesity in America over the past decade, an hour a day of exercise has been suggested as the approximate time needed to help the body lose weight and become more physically fit.

The bottom line. To lose weight you need to burn more calories through physical activity than someone who is a healthy weight and just seeking health benefits. Unfortunately, 30 minutes of activity per day may not be enough for most people to maintain an ideal weight and achieve maximum benefits.

There is no magic number that defines how long everyone must exercise. Each person's personal make-up, including age, height and weight, current level of activity and caloric intake, plays a role. The intensity of the activity is also a factor. Exercising at a higher intensity -- such as jogging at six miles per hour or faster -- for 20-30 minutes most days may achieve the daily fitness allotment, whereas walking at four miles per hour would be best for 60 minutes most days.

Make a fitness plan based on levels. Assume that level 1 is 30 minutes of activity each day. Find a way to reach this number, whether through several 10- to 15-minute short sessions or one longer activity. Once you are comfortable at this level, add 15 minutes a day for a total of 45 minutes -- level 2. Then see if you can slowly add time to build it up to an hour. Also play with the intensity of the workout, as you become fit you will need to walk faster, add intervals of varying speeds or find other ways to continually challenge your body.

Every little bit helps, so even if you miss your planned workout, add in a short session to help maintain fitness -- a walk at lunch or before work is a great way to clear the mind and keep you energized throughout the day.

Anya Petersen-Frey is a local fitness instructor.