Fitness

How to easily improve cardiovascular fitness

Nigel Issa | March 27, 2025

There are three types of people:

The genetically gifted - Those that are good at being cardiovascular fit and prioritise and enjoy that type of exercise over everything else.
The masochists - Those that suffer cardiovascular training and do it because they know it is meant to be good for them.
The ostriches - The majority who know that it’s good for them but avoid cardiovascular training at all costs. As it’s too difficult, uncomfortable or embarrassing to do.

The common image of cardiovascular training is going for a run, thrashing away on a rowing machine or attending an exercise class where the instructor does such intense exercises you want to faint. If you don’t go to a gym it could be doing a home HIIT workout or a Peloton cycle session in the privacy of your own home.

They are all characterised by being out of breathe, sweaty and fatigued muscles. For those that do it and get better they also know they have to keep doing it consistently to maintain and build fitness, which means it has to be part of their lifestyle.

But it does have the best chance of improving your longevity

Both the UK and US public health agencies recommend adults do at least 150 minutes of cardiovascular activity per week. They don’t define the intensity or type of activity, they are just happy if you do the 150 minutes.

This is underpinned by research that identified that people in the bottom quartile of VO2 max (measure of cardiovascular fitness) are nearly four times likelier to die earlier than expected, than someone in the top quartile. A person with moderate fitness in the mid range of VO2max still has double the risk of a top quartile person, but being moderately fit does reduce your risk of dying early by 50%!*

This post is for the masochists and the ostriches because I’m about to set out a style of cardiovascular training that is the most time efficient, easiest to do with the least risk of injury and least time to recover from. Plus the fitness benefits can be sustained, even when you miss a few sessions.

30 years ago it was called steady state cardio and now the longevity evangelists refer to it as Zone 2 Cardio.

How does Zone 2 Cardio work?

The human body relies on three main energy systems to provide the energy needed for various physical activities. For most people, the first two are what they associate with doing “cardio” - out of breathe, burning muscles and hitting that point where you can’t move any more.

These energy systems are:

Phosphagen System (Immediate Energy System):

Provides energy for short, intense bursts of activity lasting a few seconds (e.g. a single maximal-effort lift or a sprint). It is an anaerobic process that does not require oxygen and provides energy quickly but has limited energy storage capacity, sustaining effort over a few seconds.

Glycolytic Anaerobic Lactic System:

Provides energy for activities of moderate to high intensity lasting from about 30 seconds to a few minutes (e.g. a 400-meter sprint or weightlifting). It is an anaerobic process breaking down glucose without oxygen to create energy, resulting in lactate acid as a by product, which causes fatigue and that burning sensation in your muscles.

Oxidative Aerobic System:

Provides energy for activities of low to moderate intensity lasting for an extended period (e.g. long-distance running, cycling, or endurance activities). Uses oxygen to convert carbohydrates, fats, and, to a lesser extent, proteins into energy to power muscle cells.

It is a slower rate of energy conversion, so if activity intensity increases quickly the Glycolytic Anaerobic Lactic System kicks in like a turbo charger to provide additional energy required to keep going.

Zone 2 training uses only the Oxidative Aerobic Energy System which is around your 65-75% Heart Rate Max range. Your Heart Rate Max is calculated by subtracting your age from 220. You then set heart rate zones based on the percentage of that max number (there are more sophisticated heart rate range calculations but for the purposes of this post I’m using the simplest one). The Zone 2 name comes from the grading system used with heart rate monitors to categorise intensity of exercise.

Or more easy to understand and gauge, where you can talk while exercising but you are breathing heavily.

When intensity increases and not enough oxygen can be consumed the body switches to the Glycolytic Anaerobic Lactic Energy System that create a by product of lactate acid and that is the point when you hate cardio.

The aim is to exercise within an intensity range that stimulates the Oxidative Aerobic Energy System but not at an intensity that triggers the Glycolytic Anaerobic Lactic Energy System.

Or said more simply you only train at an intensity where your body gets enough oxygen to create the energy for the exercise you are doing. This means you don’t get out of breathe and don’t get the muscle burning and fatigue feeling that most people hate.

There are important longevity benefits of staying in Zone 2

It stimulates the creation of new and more efficient mitochondria. These are the power houses of human cells that play a critical role in supplying energy. The more you have and more efficient they are, enables you to create more energy in cells and do more work. They naturally decline in volume and function as we age. Therefore Zone 2 training offsets ageing and builds a more efficient endurance base.
The more mitochondria you have, the more glycogen can be stored in the cells rather than being stored as fat or in the blood which makes the body more efficient at storing and using food you consume and reduces insulin spikes. This will help you feel less tired during your working day as you have access to more easily available energy.
Sustaining this endurance base is easier as it is retained for 14-22 days while the more high intensity training benefits created by the other two energy systems are only sustained for 2-8 days. Which means you don’t loose it if you miss a week or two. If you have a work life that may involve disruptions to your training, then you can focus on this type of training and not regress due to missed sessions.

To create the stimulation required to get these benefits, a Zone 2 training session needs to be at least 45 minutes and for optimal results, sessions need to generate 150 to 180 minutes of Zone 2 activity per week. Which means 3 to 4 sessions per week.

This may sound like a big commitment but due to the low intensity of the training, you can multi-task while doing it by watching TV, listening to an audio book/podcast or attending one of those town hall conference calls we all love.