Getting to your threshold
going to the max is good - just do it safely
One essential element of getting out of your comfort zone is understanding that it's OK to exercise in an extreme way, as long as you are safe. We recommend Rate of Perceived Exertion (RPE) and heart rate training to explore your limits without working in a dangerous manner. Know that for generally healthy people, a high heart rate or difficulty breathing is fine during high-intensity interval work.
"The good thing about your Rate of Perceived Exertion is that it is entirely personal," group-fitness instructor Laurie Gold says. "There is not a right or a wrong -- it is about how you are feeling when you exercise. It is a way of measuring your activity intensity level without something like a heart rate monitor."
And although RPE is subjective, it has been shown to be a pretty accurate measurement of heart rate exertion during exercise. The things you consider when gauging your own RPE are your levels or increases in breathing rate, heart rate, sweating and muscle fatigue.
There are a bunch of different scales about how to give yourself an RPE rating as you exercise. For simplicity's sake, we use just five numbers that correlate with heart rate training zones.
Zone 1: Rest or really easy, usually warm-up and cool down only.
Zone 2: Easy to moderate, like you could exercise in this zone for a long time. You can easily carry on a conversation. Use this zone to recover after a difficult interval.
Zone 3: Hard: your breathing has increased but is not labored. You can talk, but it is getting breathy. This zone can help you build endurance.
Zone 4: Very hard, at your sustainable limit: your breathing has increased to heavy, and conversation is limited to short sentences or just a few words. You are uncomfortable, but could sustain this level for up to 60 minutes at most.
Zone 5: Past your sustainable limit, max effort; you are panting and cannot talk to others. You cannot stay in this zone for longer than 30-60 seconds.
What is the aerobic threshold?
The idea of aerobic threshold is a way to evaluate the factors that go into the highest level of intensity an individual can sustain. Sustain is the key word -- once you go over your threshold you go from using aerobic energy production and fat for fuel to anaerobic energy and primarily using carbohydrates for fuel.
Working out of your comfort zone is training yourself to be in this zone, at your maximum sustainable power. When you first start working this way, your ability to stay here will be limited to short durations. As you develop mental and physical toughness, you will find yourself able to stay in this zone for longer intervals.
"If you haven't ever used an RPE rating when you exercise, pay attention to how you feel," Laurie says. "The beauty of it is it's simplicity. You don't need to do any math or invest in any special monitoring equipment to find your zone."