Heart Rate & the Bodybugg

There’s been a TON of discussion recently about Heart Rate Monitors (HRM) & the Bodybugg: The bodybugg should have one… Why doesn’t the bodybugg have one?… an HRM can do the same thing as a bodybugg at a fraction of the cost…  and so on. So, I’d like to address some of the questions about Heart Rate & the Bodybugg.

Heart Rate Monitors

HRMs can range from $60 – 400. The most basic will tell time & HR. More sophisticated ones may also track GPS location, calories burned, speed, & allow you to upload the data to a website to look at it, and may keep history of several previous "files" (or workouts). I used a HRM for years because it was the only tool available to tell me how many calories I burned when I exercised. However, I tried wearing it the entire day once had no luck as far as how many calories I had burned during the day. I can’t remember HOW it was off, but I knew it was.

I found my HRM most useful when I started running; and today if anyone asks me about how to get started running, I will tell them to buy an HRM. HRMs are fantastic for running because one problem that many beginning runners have is that they want to run fast. What happens is that if the body isn’t warmed up (by walking or running slowly), there won’t be adequate blood flow to adequately produce oxygen to the working muscles. So, by using a HRM, a new runner can ensure that they’re running slow enough by keeping their HR low enough.

Eventually, when I was trying to run longer distances, I also used my HRM. I configured it so that it would start beeping at my anaerobic threshold. [Here’s a good explanation of anaerobic threshold] Simply put, your body can only run on the anaerobic threshold for short periods of time. After about 10 seconds of being in the anaerobic threshold, your muscles start burning (from lactic acid build-up) and you can no longer continue at the same level of effort. If I was running and heard my HRM start to beep, I immediately knew to slow down; if I kept running at that same speed, I wouldn’t be able to continue for very long. By slowing down, I was able to run for a longer period of time & eventually built my endurance up to where I could run for 1 hour without stopping to walk.

For this purpose, I highly recommend Heart Rate Monitors. They’re fantastic!

Time for Some Math

One of the questions that I get a lot is, "Where should my Heart Rate be when exercising?" The most common way of finding out your Target Heart Rate is to start with the Karnoven formula:

220-age=Maximum Heart Rate
Maximum Heart Rate – Resting Heart Rate = Range
Range x .55 (minimum intensity) + Resting Heart Rate = THR zone

Or you could just use this calculator. When performing steady state cardiovascular exercise, you want your heart rate to be ~70% of Maximum.

One of the biggest problems with HR is that it’s a generic formula that much of the population won’t follow. Everyone is different.  Additionally, many things affect an individual’s heart rate: heat, stress, and medication just to name a few. The only way to truly find out what your maximum heart rate is, is to get a VO2 Max Test. Be aware that the results of this test will change as you become more fit. Folks who haven’t exercised before aren’t going to be able to exercise at the intensity that a seasoned athlete would be able to.

Rate of Perceived Exertion (RPE)

For folks who are just starting to exercise, the Rate of Perceived Exertion Scale might be a better indicator. This scale is a rating from 1-10 & relies on the individual to determine intensity. Sitting, reading a book would be a level 1, walking is about 5, and sprinting (or anything you can do for only 30 seconds) would be a level 10.

The nice thing about RPE is that it pretty much lines up with Target Heart Rates. RPE 5 = 50% Maximum Heart Rate; RPE 7 = 70% MHR and so on. As a person becomes more fit, exercise becomes easier, and physically, their heart rate is lower doing that same exercise.

The Question

Okay, so all of that to answer this simple question:

@lalady29: Always worked out with HR monitor. None on bodybugg. How do you know how many cal/min you should burn?

The Bodybugg doesn’t have a HRM. It doesn’t need one. It has 4 sensors that determine calorie burn: motion, skin temperature, skin perspiration, and air temperature. Yes, it would be nice to have a HRM on the bodybugg (just so all of us data geeks out there don’t need to exercise with a bunch of technology strapped to our bodies), but for the bodybugg to be 90% accurate, it doesn’t need HR.

Lots of things influence my calorie burn: weight, how much muscle I have, gender, age, and again level of fitness. Because my husband and I are at different fitness levels and he’s got about 90 lbs on me, we could go for a 30 minute walk & burn very different numbers of calories.

So, unfortunately @lalady29, I can’t give you a direct answer to your question. Not only don’t I have that information, but as we age, we can’t exercise at the intensity that we could when we were younger.

Math Time Again

But, what I can point you to is a new term: Metabolic Equivalent (MET). You may have seen MET on a treadmill or other exercise machine. METs are based on your metabolism; the number of calories you burn at rest. METs are similar to RPE, so sitting quietly reading a book, would produce a MET of 1, walking=5 METs, and running = 10 METs.

To revisit the walking example of myself & my husband, Gary: I burn 1.1 calories per minute at rest. Gary burns 1.8. So walking at a MET level of 5 for 30 minutes, I would burn (1.1 x 5) = 5.5 (calories per minute) for 30 minutes (5.5 x 30) = 165 total calories. Gary would burn (1.8 x 5) = 9 (calories per minute) for 30 minutes (9 x 30) = 270 total calories. (I know – it’s totally NOT fair!)

The Answer

The ultimate answer, @lalady29, depends on your aerobic capacity, and how much time you have. You probably want to exercise at a MET level of about 7 (same as your RPE), but ultimately it comes down to a question back to you: If you’re not burning enough calories per day to satisfy your daily target, kick up the intensity. If you can’t do it for very long, it’s okay; your body will eventually adapt & if you keep trying, it will get easier.

Copyright Elizabeth Sherman. Purchase a Bodybugg through Elizabeth Sherman.