(From an online Yahoo Voices interview.)

Tell me a little bit about yourself.

I am a licensed psychologist in private practice, with offices in San Francisco (in Laurel Heights) and in Mill Valley. I've been doing therapy with people in the Bay Area for over 20 years, and I've been licensed as a psychologist for over 17 years.

I've worked with many different people who have experienced a wide range of problems and issues, but I tend to focus on depression, anxiety, trauma, identity issues, and stage of life problems. One of my areas of expertise is the effect of exercise on mental health.

How does exercise improve mental health?

For low to medium levels of depression and anxiety, doing regular exercise can have the same effect at the neurotransmitter level that antidepressant and anti-anxiety medications have, without the negative side effects, and with a host of positive side effects.

Many of us know that exercise can relieve and process stress and anxiety, and can help give us a better, fresher, more alive feeling. What is not always understood is that when we get our heart rate up regularly, for long enough (generally three to four times a week, for three to four months) then, as we begin to change our body chemistry, we can create a sustained anti-depressant and anti-anxiety effect, even on the days that we don't exercise.

Along with a brighter, more positive mood, and a calmer, more relaxed feeling, we can often also experience such side benefits as improved sleep, more energy, better concentration, better gastro-intestinal processing of food, and of course, higher self-esteem. Some of these effects are logical: as we tone and trim, we feel better about ourselves, more confident. Some of these effects are less intuitively obvious and more complicated, such as the fact that regular exercise can break the cycle of craving for sugars and fatty foods, replacing it with a craving for healthier foods.

Are there certain types of mental health concerns that exercise seems to have a more positive effect on? If so what?

Yes. Exercise can have an antidepressant effect as well as an anti-anxiety benefit. For low to medium levels of depression and anxiety, lifestyle changes such as regular exercise can make a significant difference.

Regular exercise directly treats the low self-esteem and the negative symptoms of depression, such as lack of energy, poor sleep, poor appetite, poor concentration, etc. As I mentioned, it also works at the neurotransmitter level to help to rebalance us biochemically.

Regular exercise also helps to process the tension and stress of anxiety, as well as serving to facilitate proper abdominal breathing, which is one of the best antidotes to anxiety. Again, exercise can create a biochemical treatment for anxiety.

What would be a good daily exercise regime someone should get into in order to improve his or her overall mental health?

A good regular exercise regime would really vary from person to person depending on your starting point. However, the guideline would be to eventually be getting your heart rate up so that you get sweaty at least 3 times a week. The research seems to consistently indicate that if you exercise three to four times per week for long enough (which turns out to be for nine to ten weeks; long enough to ingrain the behavior as patterned), then you can begin to get the sustained positive effects even on the days that you don't exercise.

There are specific guidelines and formulas that are helpful (e.g., for the target heart rate, subtract your age from 220, then multiply that number by .65 and by .85 to get the low and high ends of the target range), but what is most critical to me is to have reasonable, realistic goals, and to go step by step.

If you are just beginning, then exercise in some form once, and see how that feels. Then, hopefully, do it again.

If you are not exercising at all, don't worry about target heart rates, times, sweating, any of that. Take a walk. Go at a steady pace, around the block, around the neighborhood, the lake, anything. Then see how that feels; literally, measure your mood before your walk, and then immediately after your walk.

If you are interested and able, a jog-walk is a good method also: Jog until you need to walk, then walk until you're able to jog, and keep alternating back and forth. Take enough jog-walks, and eventually the ratio of jog to walk will start to shift.

To me it's also critical to be very concretely pragmatic about your plan. What are you likely to actually do? Start small, and minimize the barriers. Can you do it first thing in the morning before work? Can you do it at work, on your lunch break? Saturday morning? Look at your week and find the times that could work.

Then schedule it. OK, this is critical: We must understand that we cannot wait until we feel like exercising. If you are not in the habit, you may never feel like it. It would be like waiting until you feel like doing your bills, or your taxes, or going to the dentist.

For some reason, we seem to think that motivation precedes productive behavior. So we wait until we feel the motivation. But often, it just does not work that way. Usually, we have to get ourselves to begin productive behavior. Then, we feel so relieved at having started and so good about beginning to be productive, that we feel the motivation to continue. So it's really exactly opposite from what we intuitively seem to think it is: productive behavior first, then motivation, then more productive behavior.

So how do we begin? One of the best answers is to schedule it. Find the blocks of time in your calendar and lock it in, and then make everything else work around it. Then it won't be a matter of trying to find the time to fit it in at the end of the day, or before or after everything else. And it won't be a matter of whether you feel like exercising; it will simply be the next thing on your schedule that you have to do.

This idea is similar to what we all know about good investment strategy. Sound investment strategy tells us to invest 10% of our salary regularly. But who has 10% left over, after we take care of everything that we need to pay for every month? The answer is, “pay yourself first," make the investment automatically, and make everything else work around it.

If you can make a commitment to do it with someone else, that will probably increase the likelihood of success. For many, doing it first thing in the morning gets it over and done with, and can be a great-feeling way to start the day.

But the Nike people really have it right. Just do it, one step at a time, day by day, and begin to notice the effects on your stress level, your mood, and your sense of self. It's available to all of us, it's free, and it's effective for most people!

Jonathan Mahrer, Ph.D.