Why Zone 2 Cardio is Key for Fat Loss, Heart Health and Longevity

Zone 2 cardio training happens at a specific range of low-intensity, within 60-70% of HRmax, slightly higher than LISS, before aerobic threshold. Zone 2 cardio is geared toward improving the aerobic base, heart health, metabolic health, and mitochondria function, stimulating fat burning without excessive lactate accumulation.

Zone 2 Cardio

Zone 2 cardio is aerobic training performed at an intensity of 60/65-70% of maximal heart rate (HRmax). It is a specific range of intensity that targets fat oxidation, mitochondria function, and clears lactate.

Z2 can be trained with any repetitive activity like cycling, rowing, swimming, or running, as long as one keeps the intensity level in check. Training in Z2 involves sustaining the activity at the upper band of the zone 2 (low-intensity) spectrum, just below the aerobic threshold.

Such training can be categorized as low-intensity steady state training but slightly differs from LISS cardio. The effects of Z2 training greatly depend on precision, hence why it requires close monitoring to ensure one stays at the optimal intensity. It’s the highest level of exertion that effectively stimulates mitochondrial phosphorylation before lactate accumulates.

It is geared more toward athletes looking to achieve a specific goal, like enhancing aerobic capacity and endurance. As health importance increases and people want to expand their lifespan, this opens up a whole new population interested in Zone 2 training: non-athletes who seek various training methods to improve heart health, increase energy levels, and burn fat.

The Science Behind Zone 2 Training

Zone 2 training represents the highest intensity at which the body still uses oxygen (aerobic) and burns fat to power energy. Increasing the intensity by a small fraction can result in an increase in lactate (<2 mmol/L) and stimulate the anaerobic system, burning glycogen for fuel. This is where the aerobic threshold (AeT) lies, the point after which increasing intensity results in the shift towards anaerobic metabolism.

The adaptations to zone 2 training improve the body’s efficiency in transporting and utilizing oxygen, which facilitates recovery, improves aerobic function, and supports heart health. (1) (2)

The data shows that most endurance athletes competing in things like running, skiing, rowing, swimming, and cycling train in zone 2. They use a pyramidal, or polarized training model which defines the ratio spent in each zone. Most endurance athletes have a significant portion of their training at Z2 or Z1 intensity, so-called high-volume low-intensity training, with lower volume spent at the high-intensity range (<Z3). (3) (4) (5)

Training at slightly higher intensity than Z1, so at Z2, seems more effective at elevating VO2θ, which is the metabolic threshold or the individual’s aerobic threshold (AeT) at which lactate levels remain stable. The more one can increase VO2θ, the later (or at a higher intensity) the system shifts to anaerobic, which increases aerobic endurance. (6) (7)

Benefits of Zone 2 Cardio

Function, health, and performance are interconnected. Improving one leads to improvements in others. Intense aerobic training is beneficial both for athletes and for non-athletes seeking improved cardiovascular function, metabolic health, and energy levels.

Primarily, these effects stem from the adaptation to use more oxygen, one of the three core elements to creating energy. Elevating energy or improving heart function is beneficial both in terms of longevity and improved performance.

Here’s an overview of the potential benefits and adaptations that can occur as a result of training at zone 2.

Endurance: Zone 2 for Athletes

Most endurance athletes have structured training programs based on the 5 zones of intensity. They use pyramidal or polarized training which determines the ratio spent in each zone. The data shows most endurance athletes spend higher volumes of work at a lower-intensity band of Z1 or Z2. (3) (4) (5)

Most athletes use polarized training at 80/20, a fancy term which describes that most of one’s workload (80%) occurs at intensities of zone 2, and 20% is reserved for sprints and high-intensity bursts.

While HIIT or zone 5 training seems to be very effective in boosting vo2max, training lung capacity, and improving anaerobic function, it’s highly strenuous and requires longer recovery.

Endurance athletes often use a combination of training in zone 2 and zone 5 to enhance specific abilities that would ultimately improve their performance. Here’s a brief overview of the benefits Z2 can provide.

How to Incorporate Zone 2 Cardio

Zone 2 training can be done with any repetitive activity, be it cycling, swimming, or running. As long as the intensity is kept right before the aerobic threshold, which for most is around 65-70% Hrmax.

Using a fitness tracker that monitors heart rate makes the workout more effective and accurate. Most experts state that starting with 60-70% of HRmax for 30 minutes is close to optimal, then gradually increasing to 65-75%, extended for 45-60 minutes for additional benefits.

Depending on personal preference, zone 2 can be trained in various ways:

• 45 min. Cycling on a cycle ergometer at a 65% HRmax, once weekly.
• 30 min. Swimming at a consistent pace at 70% HRmax, once weekly.
• 60 min. Running on a treadmill, adapting speed to fit the 65-75% HRmax range, once weekly.

These are all great ways to incorporate more zone 2 training. Activities such as hiking, playing frisbee, or racket sports can all be great for heart health but aren’t as specific. It’s difficult to monitor and maintain the right intensity with less structured activities; that’s why aiming for repetitive, cyclical ones is important.