Train smarter, not harder with Zone 2 training to increase your VO2 max, decrease the risk of injury and burnout, and improve your pace and performance.


Most people think they have to go as hard as they can for as long as they can to improve their cardiovascular fitness. Not only is it not very effective, but it can often lead to overtraining: you won’t lose weight, you won’t increase your VO2 max or improve your pace or performance, and you’ll eventually burn out or get injured.


So how do you increase your VO2 max and improve your pace and performance? Zone 2 training. It’s the underused, surprisingly easy, and highly effective training zone for cardiovascular fitness.


“Go slow to get fast”


Heart rate is one of the best indicators of how hard your body is working during a workout. It is a tangible number, instead of a subjective evaluation.


Most heart rate-based training programs employ a 5-Zone HR model to classify your effort/intensity into one of five heart rate zones, ranging from HR Zone 1 which is associated with an easy recovery pace up to HR Zone 5 which is reached during a maximal effort sprint. 


Zone 2 training is a steady-state intensity effort below your aerobic threshold; it’ll feel easy — you should be able to breathe through your nose the whole time. Training at this intensity helps improve your aerobic capacity, increase efficiency, and build cardiovascular endurance. It’s highly effective for three reasons: 1) your body adapts to preferentially burn fat instead of carbs as a fuel source, 2) you develop type 1 muscle fiber recruitment, and 3) your body responds with rewarding metabolic, cardiovascular, and muscular adaptations.


Fat > carbs as a fuel source


Humans have limited stores of glycogen in their body; <3000kcal, but about ~68,250kcal of fat energy. Fat as a fuel source is effectively unlimited in the context of exercise.


Burning fat as a fuel source instead of carbs (glycogen and glucose) means you’ll be able to maintain a faster pace for a longer period of time and reduce the need to consume carbs during long-duration activities.


Zone 2 training improves your ability to use fat as a fuel source so you can run/bike/swim for longer. This will save your glycogen stores for when it’s required for higher intensity efforts — like the end of a race!


Type 1 muscle fibers mean you can be #1


Zone 2 training recruits type 1 muscle fibers whereas higher intensities recruit type 2 muscle fibers.


Type 2 muscle fibers use carbs as the fuel source instead of fat and produce lactate as a byproduct of their work. When lactate starts building up it produces muscle weakness, fatigue, and exhaustion which means you won’t be able to comfortably maintain that pace for more than a couple of minutes.


Zone 2 training recruits type 1 muscle fibers to use lactate as fuel. Developing your type 1 muscle fiber recruitment increases lactate clearance capacity which means you’ll be able to recover quicker between higher intensity efforts and maintain higher intensities for longer. Chants: “#1, #1!”


More physiological adaptations = more reward


The metabolic, cardiovascular, and muscular adaptations that occur with zone 2 training include:


  1. Increased mitochondrial density and capacity, resulting in more efficient oxygen transportation which increases the body’s capability to generate energy aerobically and allows a higher percentage of your aerobic capacity to be sustained without the buildup of lactic acid
  2. Increased capillary density which means oxygen and nutrients are transported to muscles more efficiently and waste products are cleared faster which leads to increased muscle and oxygen economy
  3. Increased strength of the left ventricle of the heart which results in increased stroke volume (the amount of blood pumped in one contraction -> more blood = more oxygen trabnsprot) and an increase in the volume of the left ventricle of the heart (which also results in higher cardiac output and a lower resting heart rate)
  4. Increased blood plasma volume which subsequently increases stroke volume, oxygen transport, and VO2 max
  5. Decreased sympathetic drive so your body is in a more parasympathetic state which allows you to rest and recover more effectively


Zone 2 training is easier intensity than you think but will give you a critical advantage in increasing your VO2 max and improving your pace and performance.

The best and most accurate way to find your heart rate for zone 2 training is a VO2 max test to determine your maximum heart rate and aerobic threshold. Book your VO2 max test here so you can train smarter, not harder to reap bigger fitness rewards than ever before while avoiding burnout and injury — and easily.