Zone 2 Training Wasn't Designed For Women

Lower-intensity cardio has been getting more attention with recent trends like "cozy cardio" attracting those who want gentler exercise. Now, a similar workout is catching on in women's fitness: Zone 2 training. It’s long been popular among biohacker bros and elite athletes, but it's actually a lot harder to get in the zone — and benefit from it — than fitness enthusiasts make it out to be.

Back up. How does zone 2 cardio work? 

Exercise scientists and elite athletes measure cardio workouts based on five heart rate zones, starting with zone 1 (a brisk stroll) and ending with zone 5 (running for your life). Any aerobic exercise you can do for a long time with a relatively low heart rate (about 60 to 70% of your maximum heart rate, according to some experts) qualifies as zone 2. 

Some experts think this is the sweet spot: zone 2 comes with the benefits of cardio while being sustainable enough to increase endurance. In zones 1 and 2, your body mostly relies on fat — but once you reach zone 3 and above, carbs enter the picture and start to eclipse that. Carbs provide a quick boost, but fat is an efficient and more durable energy source.

Plus, its effects on mental health could go beyond endorphins: “There is a real value mentally to some of those easier days,“ says Shawn Arent, PhD, a professor and chair of exercise science at the University of South Carolina.

Sounds good. So what’s the problem? 

The research on this type of workout has primarily focused on men — like most sports science research, says Megan Roche, MD, PhD, a research lead at Stanford Female Athlete Science and Translational Research Program. So, experts may not know everything there is to know about how zone 2 affects women. However, Arent and Roche note that the female body is naturally effective at burning fat for fuel (what zone 2 promotes), which means women may benefit less. 

Arent also worries that the trend will make people think they only need low-intensity cardio. “It's not that there's no value in zone 2, it's just that it is not a magic bullet,” he says. To truly strengthen your heart and lungs, for example, you generally need to push your body beyond its comfort zone. “High intensity is still going to improve aerobic fitness more than the lower intensities will,” he says. 

So…which zone should I be in?  

Any movement in any zone is better than none. But Arent and Roche agree that the ideal routine includes a mix of zones. Roche recommends an 80/20 breakdown, with 80% of your cardio in zone 2 or lower and the other 20% in zones 3, 4, or 5. But it all depends on your individual needs. For example, if you prefer high-intensity cardio, “then maybe you don't spend as much time doing zone 2 because you're getting aerobic benefits anyway,” says Arent. Plus, because of the makeup of the female body, “women might need more time in higher zones,” says Roche. 

theSkimm 

As zone 2 training becomes more prevalent in women’s fitness, it’s often positioned as an easy fitness hack. But like most things in life, it doesn’t work for everyone — and the benefits don’t come without hard work.