Lawn mowing as aerobic exercise?

I actually like don’t mind mowing my lawn.  I have a battery-powered push mower called a Neuton, which I push around my 1/4 acre, using one battery for the front lawn, and a second battery for the back lawn plus the “back forty”….  a rough forested patch out back. I never quite understood why so many of my neighbors ride on riding mowers when mowing their tiny lawns. But, to be fair, the Neuton will never win the Tim Allen Home Improvement Award for Rugged Manliness Woof! Woof! It has a nineteen-inch swath, and it takes a lot of back-and-forth to get the lawn done. It does a really nice job, doesn’t involve gasoline, runs really quietly and so is probably more ecological. I used to have the only one on my street, but since then a couple neighbors have bought them as well.

Occasionally I’ll wear a Polar heart rate monitor, and attempt to stay within a fat burning zone calculated any number of ways. Here’s an example for a forty year old person.

Resting Heart Rate = 60 (Taken before getting out of bed on multiple mornings)

Maximum Heart Rate = 220 – Age = 180

Heart Rate Reserve = Max – Resting = 120

The fat burning rate is 50% – 75% of the reserve; 60 – 90 beats added to the resting rate which suggests a range of 120 to 150.

Using the heart-rate monitor you can accurately modulate your heart rate by pushing faster or slower. I find that I have to usually slow down. The combination of concentrating on the heart rate and pushing slowly seems to induce a meditative state while mowing. (No really…)

Unfortunately, the fat-burning zone idea may be a myth. One argument is that if you push the lawn mower at a higher intensity, you’ll simply burn more calories, and a burned fat calorie is worth the same as burned glycogen (carb) calorie. So, maybe I should push harder, past the 75% range, which in the example would mean 150 beats or above.   Here’s another take, which is pretty convincing, which just goes to show how you can probably find a study which supports almost any point of view.

Another measurement that I take is the number of steps, with a FitBit. The back lawn plus the “back forty”, takes about 6200 steps, or a bit under three miles of walking. If I plug this into the FitBit calorie counter, as “Mowing Lawn, Walking, Power Mower” I get 490 calories for an hour and a quarter.

Then there is logging with a chain saw, one of the most strenuous and exhausting tasks that I know of, which leaves me sore for two days afterwards.  As an academic exercise, I put in an hour of chain sawing and an hour of hand-sawing. The FitBit calculator puts these in as 321 calories/hr and 499 calories/hr respectively.

This seems to make less sense… I don’t quite see how gentle lawn mowing for an hour and quarter trumps an hour of chainsawing.