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Detraining: How quickly do you lose cycling fitness?

Michael Donlevy
17 Mar 2020

You train consistently for weeks, and then take a well-earned break, but do all your gains dwindle away in the same time?

Reversing isn’t easy on a bike but there is one thing that can go backwards if you don’t ride regularly: your fitness. It’s a process called reversibility, or detraining. It’s not something to worry about if you go for three days without riding (in fact you will possibly get fitter, as that rest allows your muscles time to recover and grow, and for the glycogen stores that your muscles use as fuel to replenish).

But if you complete a gruelling race or sportive and decide you can’t face even looking at a bike for three months, it’s a different matter. 

You probably spent the previous three months training like a beast, so you may be interested to know how long it will take you – hypothetically – to return to your starting point if you opt to do nothing or, worse, are forced off the bike by illness or injury.

The answer, of course, is far from straightforward.

Detraining, let’s get physical

The first issue is an inevitable reduction in VO2 max. ‘This is the maximum amount of oxygen that you can take in and use in one minute, expressed in millilitres per minute,’ says cycling coach and personal trainer Paul Butler. 

There are three main reasons for your VO2 max to decline, all of which will have an impact on your performance: ‘Firstly blood volume reduces, so less blood is pumped around the body each minute to carry oxygen to the muscles.

'Then your heart’s muscle mass decreases, so the heart will pump less blood per beat than before, and finally there’s a decrease in the number of capillaries, which reduces your legs’ ability to absorb oxygen.

'If your muscles become less efficient at using oxygen, you’ll produce less power.’

Steve Mellor, personal trainer and exercise lead at the Centre for Health & Human Performance Cycling Clinic said, ‘This decline happens primarily in the muscles specific to your sport. For cycling, that means the leg muscles.

'After a few weeks, decreases in the amount of mitochondria – or energy factories – in the leg muscles coupled with less blood flow to the muscles mean we fatigue quicker.’

There are other implications when you stop riding.

‘You start becoming less efficient at burning fat as fuel, so you may run out of energy quicker on a ride,’ says Butler.

‘Your muscles become less efficient at “buffering” lactate, meaning you’ll experience that horrid burning sensation in your legs earlier, and an overall reduction in muscle mass will rapidly reduce your ability to produce large amounts of power over short distances.’ 

You may also gain weight if you continue to eat the same number of calories as when you were cycling regularly, plus you can lose flexibility if you’re no longer stretching, which will increase the risk of injury when you do get back on the bike.

Timing is everything

‘When you stop training the first thing to go is the ability to produce hard, short efforts,’ Butler adds ‘Next we lose strength over medium efforts, while it’s our long-term endurance that stays with us the longest.’

‘It’s not rocket science,’ adds Greg Whyte, professor of applied sport and exercise science at Liverpool John Moores University. ‘The speed at which you lose the various facets of fitness is related to the speed at which you gain them.

'The problem is that there are other factors specific to you as an individual. We all condition at different rates. One thing that even sports scientists don’t really understand is muscle memory, but we do know that the longer you do something, the longer it takes to lose the ability to do it.’

‘How long you’ve been training is known as your training age,’ says Mellor. ‘That’s important, along with your fitness level and your biological age, but other factors such as your muscle fibre type will have an influence.’

There are two basic types of muscle fibre: fast-twitch muscles, which produce power, and slow-twitch muscles, which are responsible for endurance. The former take longer to build, but also take longer to detrain. 

‘The positive changes that occur with training are very small and take years and/or huge amounts of mileage to change,’ says Mellor.

‘They also take a similar time to reverse, so changes in muscular architecture are minimal at first. During the first eight weeks the changes are mostly metabolic and are transient changes that can be altered in either direction relatively quickly.’

No simple formula to explain detraining

In short, there’s no formula for calculating how quickly you lose fitness, or how much you lose over a period of time.

A review of more than 60 studies into detraining in the journals Medicine & Science In Sports & Exercise and Sports Medicine found that after four weeks of no training your fitness could have declined by 5-10%, and muscle glycogen levels by up to 30%.

Beyond that it depends on your physiology. Our experts are agreed, however: if you are fit and have been cycling regularly for some time, it will take you longer to lose fitness than it will to gain it. 

‘You could ask 100 cyclists to stop riding for three months and the decline would be different in every one of them,’ concludes Butler. ‘There’s simply no set formula, and on top of that they’d all have very different diets and lifestyles.’

It’s all relative, and all a matter of where you started from.

Don’t stop training!

The debate raises another question: how much work do you need to put in to maintain fitness?

This one’s easier to answer, but there’s no easy way of breaking this to you: ‘Unfortunately, maintaining your race fitness still requires the perfect blend of high-intensity work, long steady aerobic work, resistance training, threshold sessions, rest and nutrition,’ says Mellor. 

If you take any sort of pleasure from riding a bike you won’t want to stop completely, and there’s encouraging news if you’re in recovery mode. 

‘Even a couple of rides a week will help you to maintain a lot of your fitness gains so that when you do plan to attack your next major goal you’ll be starting from a relatively high baseline,’ says Butler.

‘If you’re really pushed for time, even one session per week that includes some very short, hard intervals of about a minute each is a time-efficient way to maintain a reasonable fitness level.’

In fact, studies have found that when either the frequency or duration of training are reduced, aerobic conditioning is maintained for up to 15 weeks if training intensity is high. Reduce the intensity while maintaining the same volume, however, and aerobic fitness declines more quickly.

The only way to discover precisely how long it will take you to lose fitness is to carry out this hypothetical test and stop riding. Which is not something that we can, or would, advise.

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