WHY ZONE 2 TRAINING WORKS - THE SCIENCE BEHIND BUILDING BASE
Togo Keynes 
Discover what is “zone 2” training, what’s the science behind it, how does it work and how much of it you should do.
It's all about the base
As an experienced cycling coach, I often get asked about the secret behind building a strong cycling base. The answer lies in zone 2 training, a scientifically proven method that forms the cornerstone of every successful cyclist’s training plan.
In this blog, I’ll cover what is “zone 2” training, what’s the science behind it, how it works and how much of it we should do.
What is Zone 2 Training?
Zone 2 training is low to moderate-intensity training where your heart rate and breathing increase, but you can still sustain the effort comfortably for an extended period of time.
It is often described as a natural endurance training pace when cycling as it lies between active recovery and tempo zones.
In terms of the percentage of your functional threshold power (FTP), your zone 2 is between 56-75% of your FTP.
What's the Science Behind Zone 2 Training?
At the heart of Zone 2 training lies the concept of aerobic metabolism. When you cycle at a low to moderate intensity (Zone 2), your body recruits type 1 muscle fibres (slow twitch) and primarily relies on aerobic metabolism, a process where oxygen fuels the production of energy in the form of adenosine triphosphate (ATP).
This type of energy production is highly efficient, allowing your muscles to work for extended periods without fatigue setting in quickly.
Scientific studies have shown that consistent Zone 2 training leads to mitochondrial biogenesis (an increase in mitochondria). Mitochondria, often referred to as the powerhouse of the cell, are responsible for generating ATP.
Both images show a type 1 muscle fibre. Left image: No zone 2 training, Right image: The effects of zone 2 training.
Image of a mitochondria - The energy powerhouse of every cell.
How Does Zone 2 Training Work?
How Does Zone 2 Training Work Cont.
In the big picture of improving overall cycling performance, the goal is to stave off the accumulation of lactate that occurs when we ride at higher intensities. You may associate this as the point where you start to get that painful feeling in your legs from oxygen not being able to get to the muscles fast enough i.e. not long after working at threshold or above intensity (mid zone 4 / FTP score and above).
In order to achieve this ultimate goal, I need my riders to follow a prescribed zone 2 plan at the beginning of their periodised training plan – The Base Phase. This plan stimulates mitochondrial growth and density to ultimately delay the onset of fatigue as the plan moves through the build, strength and pre-event phases.
These adaptations from all the training in Zone 2 allow my riders to become super efficient, recover faster from harder efforts later in the plan and train at higher volumes while lowering their chance of fatigue and injury.
The phases of a periodised training plan.
How much of Zone 2 Training Should I do?
Given you’re not a professional cyclist who can dedicate months in the off-season and during the season to long daily hours in zone 2 then it all depends on the following:
The above will determine how much zone 2 training you can do depending on what your primary objectives are. (See recommendations below).
Training Recommendations Based on Objectives
- Build a solid cycling fitness base and have time on your side in the build-up to your event – I’d recommend 45-60 minutes a day for a minimum of 8-12 weeks. I refer to this as the pyramid effect where the wider the base you build, the greater the potential to build the pyramid in a periodised training plan. This is the gold standard approach to any cycling training plan where a rider has an extended lead time to their event and can dedicate a minimum of 6-7 hours a week. If a rider can dedicate more time a week then I would add 1 to 2 longer sessions of 2-3 hours so ideally 9-13 hours a week. Weather permitting, I get riders to do at least 1-2 longer rides outdoors on their bike.
- Maintenance mode - If you want to maintain your cycling fitness and not lose some of the gains you have already made from an earlier training block, then I'd introduce 3-4 x 45-60 minute zone 2 sessions into a rider's training plan, with 1-2 tougher interval sessions in zone 4-5 for 30-45 minutes.
- Best Gains with only 3-4 hours to spare a week – If you are time-pressed I’d do 3 x 45 minutes and 1 x 90 minutes in zone 2 or 3 x 45 minutes and 2 x 60 minutes or 3 x 60 minutes and 1 x 90 minutes in zone 2.
- Coming back from injury or no event planned yet and you can dedicate 5 hours a week – I’d recommend 3 x 45 minutes, 1 x 60 minutes indoors, 1 x 2 hours outdoors in zone 2.
- Weight loss to improve power to weight - I’d introduce 4 x 60-minute fasted sessions in strictly zone 2 first thing in the morning and 2-3 x 45-minute sessions later in the day or after some food intake. You can also do elements of this later on in a periodised training plan.
Example Training Session Structures
Example Session 1
Image Above: Example structure of a 60-minute zone 2 session. You will remain in zone 2 for the entire session apart from a short acceleration in the final minute.
Example Session 2
Image Above: Example structure of a 60-minute zone 2 session. You will remain at mid-zone 2 for the entire session.
Example Session 3
Image Above: Example structure of a 60-minute zone 2 session. You will remain in zone 2 for the entire session apart from a 1-minute effort at the top of zone 2 every 10 minutes.
How do I get my Zone 2 Training Zones?
Before you even start a zone 2 training phase or a base training plan, you need to work out your training zones for your current fitness level. I recommend all the riders I train to either perform a 20-minute FTP test (or a RAMP test to exhaustion) ideally on an indoor bike or indoor trainer that projects power, cadence and speed to get their accurate zone 2 training zone.
Your FTP score is 95% of your 20-minute average power or 75% of your final RAMP score. Once you know your FTP score then 56-75% of that is your zone 2 power.
Too often many riders don’t test and use old FTP training zones which are often inflated and as a result riders often end up working outside zone 2 and having little or no proper zone 2 adaptation.
When I work with my 1-1 VIP coaching clients, I ensure they prepare properly before a 20-minute FTP Test and use a heart rate (HR) monitor as we want to see what their threshold HR is for the 20 minutes as well. This is essentially your average HR for the 20-minute test only. This allows me to work out their heart rate training zones as well which is an outstanding metric to track alongside your power when doing zone 2 training.
Coach Tips
- Try to do the shorter sessions (up to 60 minutes) indoors as the quality is magnified by not having to worry about everything around you like when on a ride out e.g. traffic lights, cars, potholes, etc. See an independent guide for the best-rated indoor trainers for every budget.
- The perfect time to start base phase training is from mid-October to mid-January in the Northern Hemisphere as we move into winter or in the Southern Hemisphere it would be mid-June to mid-August.
- When doing zone 2 training I recommend training to both power and heart rate to accurately measure how hard you are working and your body’s response. Therefore I recommend always wearing a heart rate monitor that uses Bluetooth or ANT+.
Whether you're striving to enhance your endurance, improve fat adaptation, or increase your heart's efficiency, zone 2 training is a science-backed approach that can take your cycling performance to the next level.
Hear from some of our riders who have benefited from Zone 2 Training:
"Since starting Zone 2 training, I’ve been amazed at how my recovery has bettered between efforts. The Z2 training plan has helped my on-bike performance massively. Having recently re-ridden a route I completed a year ago in Spain, I bettered the time by 25 minutes…brilliant results." Luke King
"It took me a while to embrace, but now I love zone 2 training. No more endless cycles of pushing hard every day until I burn out physically and mentally and have to take a week or longer to recover. It's honestly transformed my training. My performance on the days I push hard has reached new levels and 30-60 minutes of zone 2 on my off days are a joy. They are amazing for my recovery and longer-term increased endurance." Monie Lindsey
"Since starting my training with Togo at Njinga Cycling in late 2021 riding indoors and out at Zone 2 has become an important part of my training routine. Houses have to be built on strong foundations and the same is true of cycling.” Miles Flint
"Zone 2 is at the heart of all my training and I do at least 3 hours a week. Its impact has been transformational, using longer blocks in the off-season to build a base on which I’ve seen big gains in FTP. Beyond building base, it’s really helped me manage my heart rate to become more efficient and I’m now using this to bring focus to better breathing." Simon Hathaway
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