from the diary: “Tuesday 3/25/86
“I’ve been reading Fit or Fat, a very interesting book that says that fitness should not be based on how strong you are or how fast you can run, but on how fast your heart beats. (Mine beats very fast – I took my pulse – which means I’m not in good shape.) You’re supposed to do an aerobic exercise that makes your heart beat 80 percent of maximum heart rate and sustain that level for 12 minutes.”
Since I read Fit or Fat the target heart rate has become orthodoxy. Everybody makes sure they include aerobic exercise in their healthful routine (don’t you?). Frankly, I find most specifically aerobic routines so boring they drive me crazy. The treadmill? Please. I like to walk, however, and if I have a destination in mind I can walk at a good clip, which presumably raises my heart rate to the aerobic. I long since stopped checking my pulse because, what, I’m going to walk faster & faster if I’m not at the optimum? And I’m already walking so fast my feet hurt? When I started walking to & from work at the Claremont branch (a 2 mile jaunt) I would get sweaty and, especially climbing the hill north of UC campus on the way home, would feel some strain. Now I breeze up the hill. And it’s not like I walk all the way every day. Usually I take the bus part of the distance.
One idea I picked up from Fit or Fat: you can be thin and fat. It’s one of those nicely contradictory notions that makes sense after the explanation. Y’see, you’ve got skinny arms, right?, but the muscle, because unexercised, is permeated with fat molecules. Strength-training isn’t enough to banish that intra-muscle fat because your daily meals typically provide enough fuel for muscle growth, especially if the exercise makes you hungry, eh? But if you build your heart muscle through aerobic exercise then even when resting your metabolism is higher, requires more fuel so burns up the stored fat. Fat is the lowest quality body fuel and during exercise your body burns sugars and proteins. It’s when you are resting that your body harvests the fat.