ornoth-cycling (ornoth_cycling) wrote,

Ya Gotta Have Heart

I’ve wanted a heart rate monitor (HRM) for many, many years. They’ve been the gold standard for cyclist training tools for a long time, notwithstanding the recent trend toward power meters.

However, they’re somewhat expensive, and I never felt justified in spending the money. Plus I feared it would be like the cadence sensor: useful only for a short period of time, enough to calibrate one’s own internal sense, and extreaneous thereafter.

However, prices have come down, and an HRM would have been handy indeed for my wintertime indoor trainer workouts. So I finally picked up a cheap Sigma Sport PC14 on sale at the Noshbar.

Cheap is the word. Any electrical field will cause the unit to either register a pulse of zero or over 200: a near impossibility for someone my age. So I can’t really trust it to record the max heart rate I hit during any given workout. Unfortunately, your max is what all the training heart rate zones are based off, so I’m fiddling with it to find my true max.

Here’s my initial observations. They’re based on only two days’ worth of use, so they’re highly provisional.

heart rate monitor

Resting heart rate, taken before getting out of bed in the morning, is a good indicator of general fitness. A sedentary person might have an RHR in the range of 60-80 beats per minute, while a trained cyclist would be closer to 45-55, so lower is usually better. I’ve seen a low of 51 bpm, and a sustained reading of 53, so that’s in line with my expectations. I remember taking my pulse in high school when I was bored and getting resting rates below 48.

Max heart rate is largely a function of age, and the standard formula for estimating it is to subtract your age from 220, but that will then vary based on your fitness level, with higher numbers being better. A 45 year-old’s expected values range from 164 to 186 bpm, and although I predicted I’d max out at 165, I’ve seen readings as high as 171. That’s in line with the base formula, although again that’s preliminary and more testing is required.

Using that as a base, I derived several additional numbers. My aerobic limit is around 120 bpm (70% MHR), and recovery rides should stay below 140 bpm (80% MHR). My lactate threshold should be somewhere between 140 and 155 (80-90% MHR).

The most interesting thing I’ve learned so far is that you can do easy aerobic training or you can do hard, painful interval training, but you derive very little training benefit in the middle ground between them. Below 70% MHR you’re burning mostly fat and can go all day; above 85% MHR you’re burning glycogen and building up lactic acid and need to rest and recover every few minutes; but in that grey area between 80-85% MHR, you’re working way too hard to burn any fat, but not hard enough to exercise your VO2 and ability to buffer and clear lactic acid. So that’s a dead zone you should avoid training in; for me, that area is from about 137-145 bpm. In short: go easy or go hard, but don’t go halfway.

For anyone trying to lose weight, that information is incredibly important. You’re always drilled with the value of exercise— particularly aerobic exercise—in losing weight, but there’s a huge mental trap there. Although aerobic exercise raises your heart rate, it doesn’t raise it enough for it to feel hard. Since most people think “harder is better”, they’ll often push themselves and work out in this middle ground, where they’re working hard, but not all-out. Unfortunately, at that level you’re only burning glycogen, not fat, and you’ll just crave sugar to replenish your blood and liver glucose levels. To lose weight, you have to do gentle exercise for very long periods of time, and it shouldn’t feel very difficult at all.

It’s similar to one of the problems I observe in novice cyclists. They get on a bike and mash down on the pedals at a knee-shattering 60 rpm. They think you have to work hard to make the bike go, or that you’re not exercising unless it’s hard work. It’s counterintuitive to a new rider, but selecting a very light gear that you can turn over easily is not only less effort and better aerobic exercise, but it’s also more efficient, and will save your knees, which harder efforts will damage.

So that’s the report on this year’s new toy. I’ll be curious to get more data from it over time, and particularly to see whether it provides me with useful information that will help me marshal my physical resources during longer rides.

Tags: analytics, fitness, heart rate, hrm, purchases, shifting, weight
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