What is Zone 2 training, why it works, and how your current training regiment could actually be undermining your progress.
If you've been paying attention to the world of outdoor endurance sports, you've probably heard "Zone 2" training come up at least once. It's the secret of the Scandinavians that has gone mainstream, thanks to more and more data supporting it's success. In most standard zone training programs, you'll have five "zones", which are calculated as either a percentage of your maximum heart rate, or by effort level (or by lactic acid/threshold testing, but that's for another time).
% Max Heart Rate
Effort Level/Talk Test
Can Hold For?
Easy to Moderate, Talking w/ Short Sentences
Moderate, Few Words at a Time
Hard, One Word at a Time
Maximum, No Talking
Zone 2 lies right in that nice "Endurance" zone.... think a nice, easy jog at a comfortable pace, a fast hike up steady incline, swimming laps, or cycling at a decent clip. In many training programs, Zone 2 is overlooked for much more exciting, much faster Zones 4 and 5; think HIIT bootcamp classes, Crossfit, etc. Why spend a whole hour exercising when you can burn the same calories in 15 minutes? Well, that's because there's a difference between "training" and "burning calories". When we train, we prepare for our chosen endeavor.
If said endeavor is an outdoor endurance activity, such as hiking, trail running, or mountaineering, our bodies will need to be good at using fat as our primary fuel source through fat oxidation and aerobic metabolism. This is compared to using carbs as a primary food source through carbohydrate oxidation and/or anaerobic metabolism, which we use at higher effort levels, such as sprinting or playing hockey. Now, the problem is, we can't perfect both types of metabolism at the same time. After a certain fitness level, as one type of metabolic pathway improves, the other will be diminished. That means, if you're training for a half marathon, but mostly take bootcamp classes or just run 5ks at race pace, you're actually hurting your body's ability to improve it's necessary metabolic pathways. How do we translate this into training then? At least 65-75% of your overall cardiovascular training should be done at Zone 2 effort levels. If this feels like a huge change, or much slower than you're used to, good! You're not alone. Most of my clients (including myself) would much rather spend a good chunk of our training pushing ourselves to the limit. Many people complain that they don't feel like they "got a good workout" after completing Zone 2 training. That's ok. There's a time and place for maximum effort, and when it's there, go all out. However, to make real progress in your training for an endurance event, live and work for most of your time in that sweet, slow, Zone 2!