“…eating alone will not keep a man well; he must also take exercise.” Hippocrates Circa 450 BC

So you’ve been exercising regularly and now you want to know how you’re doing. Are you walking longer than before? Have your swimming times improved? How fast did you go on your most recent bike ride? What was your heart rate?

Up until the last decade or so, monitoring activity was limited to a watch and possibly writing that in a diary or calendar to keep track of your sessions. If you wanted to know how far your regular walking or running route was, you got in your car and drove it. Nowadays there is a whole host of products that you can use to monitor your activity from simple pedometers to sophisticated phone apps and devices that can let you know your heart rate, how fast you’re going, how many calories, etc.

Which one will work for you? Some of that depends on what type of activities you want to monitor and what your goals are. If walking is your main activity, then you may want to know how far you have walked, how many steps and how long it takes. Conversely, if swimming is your main activity, you will be limited by the ability of devices to work underwater; heart rate monitoring and GPS tracking don’t work underwater, and a pedometer isn’t going to help either.

Pedometers are simple devices (no more than one square inch) that are usually attached to your pant belt just in front of your hip. Their main function is to measure the number of steps (using a mechanical swing arm). Some pedometers attach to other areas of the body but they tend not to be as accurate. The use of pedometers has been demonstrated to motivate people to be physically active. Their limitations include not being able to determine intensity of activity, are only good for stepping activities (walking, running) and the mechanics break down with frequent use.

Accelerometers are more sophisticated devices that can measure movement in multiple planes (not just moving forward) and because they can measure acceleration forces, they can be used to determine intensity such as recognizing running from walking. In the world of research, accelerometers are worn around the waist and are accurate for assessing walking/running movements but are limited in their ability to properly measure upper body activities. Some accelerometers are worn on the wrist and can measure more diverse activities, however, there are still very few studies to determine how accurate many of the commercial devices are. Like pedometers, accelerometers cannot measure activities like cycling and they are also generally not waterproof.

Heart rate monitors measure a person’s heart rate and thereby provide an indication of personal intensity. There are two main types, those that include a chest strap and those that do not. Chest straps directly measure heart rate while devices on other parts of the body measure pulse. The two are not exactly the same as indicated here, and for people with heart conditions, that may be an important consideration. In addition, monitors that measure pulse are not as accurate as monitors with a chest strap but these differences may not be of importance for most healthy individuals.

GPS trackers are used to measure distances and speeds, which can be quite useful for runners and cyclists who want to know how far they have gone and how fast. This is especially valuable when starting out with these activities or when using new routes for your exercise. Although for most of us, we usually use the same small number of routes to walk/run/cycle and after using a GPS tracker once or twice on each route, the value of continually using it diminishes (your exercise time will indicate whether you have done the same route faster or slower). In addition, there is very limited value in GPS tracking for people who do activities like tennis, team sports and water sports (the GPS signal can’t transmit through water).

Calorie counters attempt to give users the number of calories expended during an exercise session, and this may be attractive to people who are counting calories for weight management. Knowing calories can also give a sense of volume and intensity For example, a long walk may be equivalent to a short run in terms of calories. None of the devices determine calories directly and herein lies the problem as most devices are grossly inaccurate in providing calories. The simplest devices use equations based on data of external work (like most fitness machines), which themselves have error in them. The more accurate devices will ask the user to input individualized information like age, sex and weight, among other things.

When deciding on which device to use, it usually isn’t an either/or of the features listed above as many devices nowadays combine a number, if not all, of these features together along with other features such as an online diary. Yet not all devices measure each feature with the same accuracy. For example, many devices have some sort of heart rate function along with GPS tracking and acclerometry, but if measuring heart rate is important, you may want to get one using a chest strap. The bottom line is to get a device that offers the best and most accurate measures for the type of activities you commonly do.

In the next blog I will discuss the benefits between continuous and interval training.

This is Part 5 in a series of blog posts entitled Being Active While Living an Active Life.