first published May 29, 2008

I suppose it’s human nature to look for obscure things that might affect our health. “Chemicals” are always an easy target because they allow us to blame outside forces that are often beyond our control, and in turn, exonerate ourselves from blame.

Unfortunately, it doesn’t take a lot of reading between the lines of health articles to realize that our sedentary lifestyle is the number one threat to a long and healthy life. Fortunately, part of the solution is in your own backyard—literally.

Gardening ranks high on the list of activities that can not only help keep our cardiovascular systems in great shape, but also help keep our muscles strong and our joints flexible.

So the question is just how good a workout is gardening? Well, from a caloric burn standpoint, gardening has an excellent track record. The scientific way of measuring how good an activity is for burning calories is to note its METs. MET stands for metabolic equivalent, and by using METs you can compare any activity to the energy cost of resting quietly. For example, if you were sitting on the couch with the remote firmly in hand, your body would be burning one MET worth of energy. So a 1-MET activity for a 60-kg person who’s doing nothing more than contemplating his or her existence would burn about 60 kilocalories per hour (the term calorie is often mistakenly used in conversation). Now if that same person would rise from the couch, head to the yard and water the lawn, the MET level would rise to 1.5. Better yet, picking fruit from a tree would bring the MET level up to a 3, and general gardening would raise it to a 4. Using a power mower (not the riding, or self-propelled type) moves the METs up to a whopping 6!

To walk you through the equation, our 60-kg friend in couch-potato mode would burn about 1,392 kilocalories per day (sleeping is a .9 MET activity). That equates to approximately two and a half Big Macs. Now if that person were to engage in a couple hours of general yard work every day, the kilocaloric-burn picture would change substantially. Working at that 4-MET level would burn an extra 360 kilocalories. Subtract the couch potato MET value of 1 from the general yardwork MET of 4 and you end up with what equates to a whopping five Big Mac’s worth of kilocalories burned per week!

Of course, kilocaloric burn is only one of the benefits of gardening. Any time you lift a pot or plant a tree, the very act is part of a good old-fashioned weight lifting program that keeps our muscles strong and promotes bone density. Joint flexibility is also improved by gardening simply because of the variety of movements required. Lunging, stretching, pushing, pulling, bending and balancing can all occur within an hour’s work. But like any activity, gardening should be done safely. Change tasks frequently; don’t lift objects that are too heavy; don’t overdo; protect your knees; use the right equipment—and in the way it’s intended to be used.

One final thing to remember is that although the physical health benefits from gardening are reasonably easy to measure, the mental health benefits are equally important to acknowledge. But just how does one ascribe an equivalent mental MET value to picking a crisp apple off a tree or seeing tulips in full bloom? Well, my heart skips a beat just thinking about it.