"Now that I hit 30, I can tell my metabolism is slowing down," or "I'm just not as strong as I used to be!"-these are examples of comments about the effects of aging that we frequently hear from clients. Getting older is tough business, for sure.

According to the Encyclopedia of Sports Medicine, men tend to maintain their peak levels of muscular strength, endurance and cardio respiratory fitness until around age 30. Then after 30 there is a gradual decline throughout life. Women tend to reach their peak in physical capability shortly after puberty and then undergo a progressive decline. Translation ... we are one big mass of decaying cells.

Here's the good news for those of us who stay physically active: The decline in our physical performance is much slower than for those who are intimately connected to their couch. The take-home message? You may not be able to stop aging in its tracks, but with exercise you can stay young and vibrant a lot longer.

Over the next two weeks we'll outline what happens to many physiological body systems as we age. This week let's take a look at your metabolism and your cardiovascular system.

Basal metabolic rate: The number of calories you burn at rest, or your basal metabolic rate, decreases two percent per decade after age 20. That means at age 30 it's down two percent, at age 40 it's down four percent and so on. This also depends on the individual and some people could see as much as a 10% decline by age 65.

Cardiovascular system: With each passing decade your maximum heart rate drops, which translates to a reduced training capacity for older adults. Aging typically leads to lower oxygen consumption and less capacity to generate energy and perform work.

But you don't have to take this lying down. Fight back with EXERCISE. Next Monday we'll look at the effects of aging on your skeletal, respiratory, muscular and nervous systems.