Health experts urge Zone 2 focus for endurance and fat burn

Health professionals are urging runners and other exercisers to tilt the balance of training toward heart rate Zone 2, a lower-intensity pace that supports aerobic endurance and fat metabolism. Dr. Morgan Busko, a sports medicine physician at NewYork-Presbyterian, and Jesse Ramos Junior, a fitness expert with BBT Fitness in New York City, say most training should occur in Zone 2 because it is sustainable and builds a strong aerobic base. Both emphasize that Zone 2 is not a universal ban on harder efforts, but rather a foundation that can support longer-term gains in fitness and health.

They say 70 to 80 percent of run time should be spent in Zone 2, roughly 60 to 70 percent of a person’s maximum heart rate, where conversation is still possible. The idea is to promote fat burning and endurance while reducing the risk of burnout. High-intensity work remains important, they add, with about 20 to 30 percent of workouts spent at a pace where talking becomes difficult or impossible. The approach, they say, can make training more sustainable and enjoyable for a broad range of athletes.

The pair also notes that the same principle applies to other aerobic workouts such as cycling, swimming or elliptical training. For beginners and seasoned runners alike, longer sessions at a comfortable pace can help to gradually improve the body’s ability to sustain effort, while shorter, higher-intensity intervals introduce the kinds of anaerobic challenges that support sprinting and sustained hard efforts. Dr. Busko told Business Insider that the concept is beneficial for everyone—from new runners to elite athletes—because longer runs at a low heart rate help build aerobic endurance, which in turn can enable faster performances in due course.

Experts say the underlying logic is simple: when you run slower for longer periods, your body becomes more efficient at using fat as a fuel source, and your cardiovascular system becomes more proficient at delivering oxygen to working muscles. That combination improves endurance and can reduce fatigue during longer events. The emphasis on Zone 2 has gained traction as a way to make exercise more approachable for people who are new to regular workouts or who have struggled with burnout from overly aggressive training routines.

The World Health Organization’s guidelines still frame exercise around weekly totals: 150 to 300 minutes of moderate-intensity activity, such as brisk walking, jogging or cycling, or 75 to 150 minutes of vigorous activity, as alternatives. Health agencies note that meeting these guidelines remains a public-health goal and that many adults in the United States do not meet them on a weekly basis. In practice, that has encouraged coaches and researchers to explore Zone 2 as a more sustainable path to regular activity, with the aim of helping people exercise more consistently rather than overexerting themselves in every session.

But researchers have not reached a consensus on every detail. A recent muscle study suggested that the biggest increases in mitochondrial content—energy factories within cells—occurred when training included higher-intensity components. Still, experts say Zone 2 training can be a valuable base, particularly for people who want to exercise more frequently without feeling crushed after each session. A sustained, lower-intensity approach may also help people maintain an elevated heart rate for longer periods, which some researchers believe offers cardio-health benefits alongside improvements in efficiency and endurance.

To calculate Zone 2, many experts recommend first determining maximum heart rate by subtracting age from 220. Zone 2 typically corresponds to about 60 to 70 percent of that maximum, though individuals can vary. For example, a 30-year-old with a maximum heart rate near 190 beats per minute would see Zone 2 roughly in the 114 to 133 beats-per-minute range. The upper end of Zone 2 is often described as the threshold where talking becomes easy but effort remains noticeable. It is important to remember that heart-rate zones are estimates and may not be accurate for everyone, which is why many athletes and patients rely on wearables or heart-rate monitors to guide training.

Proponents say Zone 2 training may also help people return to workouts more quickly after rest periods or illness because it is less exhausting than high-intensity training. While the science continues to evolve, the practical takeaway for many weekend warriors and casual exercisers is clear: building a reliable cardio base with plenty of Zone 2 work can improve long-term adherence to exercise, support weight management, and contribute to a healthier cardiovascular profile, all while offering a safer entry point for beginners who may be intimidated by more aggressive routines.

In short, Zone 2 is emerging as a widely endorsed core principle for everyday fitness. It does not replace the value of tempo runs, intervals, or sprints for performance, but it provides a sustainable framework that can help people exercise more consistently, reduce burnout, and still achieve meaningful health benefits over time. As athletes tailor plans to their own goals and capacities, the message remains consistent: start slow, build gradually, and keep a steady pace that you can sustain, then introduce higher-intensity efforts as fitness and confidence grow.