- Watts: A measure of user power output.
- Mets: (Metabolic Equivalent Task) A measure of user power output, taking into consideration the user’s body weight.
“Watts” is a measure of power. Power is defined as a “rate of work.” Watts can be a measurement of mechanical or electrical power.
Here’s an example of the difference between work (energy) and power: two cyclists, each weighing about the same ride their bikes to the top of a hill. One rides at 8 mph, the other at 12 mph. They have both done roughly equal amounts of work. They have both spent equal amounts of energy (Calories.) Surprised? Well, they both were at the bottom, and now they both are at the top. That is work. Remember; one rider was pedaling harder, the other was pedaling longer.
The difference is in their power. The 12 mph rider produced 50% higher average Watts than the slower rider. How does this apply to exercise equipment? One question we are often asked is: how can I burn more calories? The answer is; you can either workout longer or at higher intensity (Watts.) A common misconception is that, a lot of people are told to loose more fat by working out easier. They can do this, but they must work out longer. In terms of bicycles, power is what propels the rider and bike. The greater power the rider puts out, the faster he goes.
Exercise equipment measures Watts as a way to measure the users power output. On an exercise bike, the user can increase his Watts output, by either increasing the Level of resistance, or by pedaling faster at the same Level (on a constant Torque bike.) By the way, we know that the average “Health Clubber” will average approximately 80 Watts during a workout. As the user increases his Watts output, they will immediately feel an increase in “Exercise Intensity,” followed by an increase in Heart Rate.
So, think of it this way, Heart Rate is a measure of your internal workout intensity. Watts is your actual mechanical output.
Here are some examples of what we or the user can do with Wattage information.
1. We can use Watts to develop a true speed equation. Speed on an outdoor bike is driven primarily by Watts, not just pedal RPM.
2. We can measure your Fitness Level. The more Watts (mechanical output) a user can achieve with lower heart rate (internal intensity) the greater one’s Fitness Level. As the user gets fit, they will produce more Watts at lower heart rates. This is the basis for our Fitness Tests
3. Rehabilitation Facilities need to determine the patient’s mechanical output in order to control their intensity.
4. We also use Watts to design better programs that are easy enough for less fit users, but still challenging for the Tour Cyclist.
Besides Bikes, Watts can also be measured on:
- Treadmills: by measuring user weight, speed, and % elevation.
- Steppers: by measuring user weight and “Steps per Minute.”
- Weight Machines: by measuring Weight and lifting speed.
- Rowing Machine: by measuring speed and resistance.
Mets is also a measure of Power, but it also takes into consideration the users body weight. Here are some approximate Met Levels for common activities:
- Sleeping – 0.5 Mets
- Sitting in a chair – 1.0 Met
- Standing – 1.5 Mets
- Walking slow – 2 Mets
- Running 5 mph – 7 Mets
- Running 10 mph – 16 Mets
Let me explain Mets using the following example. I have a brother and he and I are both pretty fit, but he is much bigger, and stronger than I am. Every time we walk up the stairs together, he is producing about twice the Watts (power) as I am, because he is carrying more weight. However, the intensity we both feel is about the same. Our Met level is also approximately the same. He is producing more work and more watts, but because he is bigger and stronger, our Met levels are roughly equal.
Here is another way to understand Mets. One Met represents our “activity level” when we are at rest (sleep,) and at one Met, we are burning a certain amount of Calories / Hour. As we increase our exercise intensity level, our Met output level increases, and our Calories / Hour consumption increases. If we are exercising at 10 Mets (such as a 6 mph run,) we are burning Calories at 10 times the rate as when we are at rest.
Mets are most commonly used by Rehabilitation Facilities to control exercise intensity.