Interestingly, the science behind detraining (or ‘reversibility’ of fitness as it's sometimes known) through a decrease in training volume or a complete halt to training isn't as complete as you might expect it to be.

This is especially true when it comes to detraining in elite athletes, mainly because it's tough to find a reliable and long list of really fit athletes who are willing to deliberately lose hard-earned fitness just for the sake of a research paper!

That said, there's a reasonable amount of literature on the subject from detraining studies that have used groups of 'moderately fit' volunteers and various case studies using elite athletes who've had to take time off due to illness or injury.

Rather than dive too deeply into those studies (I recommend this well-referenced paper in Peak Performance if you did want to read more), I'm going to focus on blending key points from the science with my own experience of detraining over the years and try to offer up some practical advice.


Doing SOMETHING is infinitely better than doing NOTHING

‘Use it or lose it’ is what we’ve often been told about holding onto aspects of fitness and it's a true statement.

Even if we're super-fit to begin with, stopping training altogether will result in a pretty rapid degradation in fitness.

Image Credit: Pexels ©

Admittedly, the losses in the first week of total inactivity are small and in the first 2-4 days there may even be fitness gains as you recover fully from prior training. But you can expect up to a 15-20% reduction in VO2 max after a month of 'couch surfing', as well as a significant increase in body fat (dietary changes notwithstanding) and a host of other physical and metabolic changes that put you well behind where you were 4 weeks prior.

That said, even if you do a relatively small amount of training (around 30-50% of your previous volume) this decline can go from dramatic to almost imperceptible, which leads us to Key Point 2...

Maintenance is significantly easier than driving improvements

Maintenance of fitness can be achieved with very little training stimulus, compared with what is required to generate significant improvements in the first place.

In an excellent podcast episode on the subject, Dr Scott Trappe (an expert in detraining from Ball State University in the USA) discusses the fact that once physical adaptations in the body are made, then you only need to stimulate them 2-4 times per week to keep levels just about where they are at.

Dr Trappe feels that many athletes get too scared of losing fitness if they don’t train most, if not all, days and I’d tend to agree with that based on my own athletic experiences and from observing athletes around me over the years.

It takes confidence to accept that a pretty serious reduction (e.g. 50% or more) in training volume would result in very little measurable fitness loss and, if you want to understand the nuances of that a bit more, then I highly recommend listening to that podcast for more detail.

Some aspects of fitness are highly specific, but many are transferable

It’s true that to maintain specific conditioning for particular sports you need to practice those actual sports reasonably frequently to keep the right muscles conditioned and to maintain fluency in the movement patterns.

Many aspects of fitness are ‘shared’ across pretty much all activities and these include things like expanded blood volume, a stronger heart, the ability to effectively store and utilise glucose as a fuel.

Therefore, even if you can only run for a period when you’re actually wanting to train for the swim-bike-run of a triathlon, rest assured that a good proportion of the benefits you get from running will transfer to the pool and the bike once you get back to them in the future.

Image Credit: Tembela Bohle via Pexels ©

HIIT is perhaps a good idea if you're time-limited but still aiming to maintain fitness

It's often said that you lose ‘top end’ fitness (i.e. the ability to sprint or maintain high outputs for a short period of time) before you lose endurance and anecdotally it’s something I’d probably agree with.

This may be true if your ‘high output’ training is what's 'shelved' when you experience a significant drop in training volume, but it does not necessarily have to be the case.

Research into High Intensity Interval Training (HIIT) suggests that even very short bouts of activity (e.g. 5-10 x 30 seconds max effort with long rests in between) done 2-3 times per week can have astounding impacts on fitness if adhered to on a regular basis.

For this reason, incorporating some very short, very hard efforts into periods of reduced training volume might be a wise idea to lessen the impact that the overall reduction in volume has.

Life-long athletes can hold onto fitness for longer than newbies

The good news for anyone with a rich history of endurance training is that you're likely to hold onto fitness more effectively than newcomers to sport.

This is thought to be because some really deep, subtle and chronic adaptations to training accumulate over a long period of time and these take a long time to reverse, even if you stop completely.

As a personal example, I had over 15 years of training history behind me when I had the only long-term ‘rest’ of my adult life about 10 years ago when I had to have knee surgery. I was laid up in a straight leg brace and unable to train for many months.

When I did finally return to running, I was only able to run 2-3 times per week and rarely for more than 5 miles at a time. I still managed to run a marathon (pacing a friend who broke the World Record for running with a 40lb pack) in about 3 hours and 20 minutes within about 18 months of getting off the operating table.

Whilst it was a long way off my best time, I was pleasantly surprised how comfortable I found it. I'm convinced that I leaned on my ‘history’ as an endurance athlete to do it because my immediate build-up to the race was ridiculously light in comparison to the majority of others who would've run a similar time.

A viewpoint on the specifics of the current COVID-19 situation and my own developing plan

Given the worldwide situation we find ourselves in as I type this article, many of us are either in lockdown or dealing with restrictions in movements that are hampering our ability to train as we'd like.

I usually split my training fairly evenly between swimming and running but now, given the pools are shut and the sea is only about 9°C (48°F) in the UK, I've largely been confined to running.

We’ve been in this situation for a couple of weeks to date and it’s looking likely to go on for a while longer so I'm developing an idea of how I’m going to try to train for the foreseeable future and the rationale behind it is as follows:

  • My main activity will be running
    This is because it’s the easiest one to do while we’re still allowed outside. It gives me fresh air and sunshine (some of the time!) and I'm lucky in that it’s generally my preferred activity anyway. If you're interested in taking a look, I log all of my runs on Strava.

Image Credit: Andy Blow Strava ©

  • I’m aiming to run ‘most days’ (i.e. 5-6 times per week), but I'm reducing the intensity of almost all runs by about 20-30 sec per KM below my usual training pace and adding 1 long run at the weekend (around 90 min to 2 hours)
    The reason for the reduction in intensity is to try to avoid injury at all costs. I'm being cautious as I would hate to be sidelined right now because, coupled with a lockdown, injury might make me very miserable.
    The regular running and long run each weekend are focused on building some longer term tissue resilience in my muscles and tendons too.
    This is something I feel has been sorely lacking in recent years so I'm actually grateful to have no races to prepare for and for the opportunity to ‘turn down’ the pace for an extended period.
  • To support the running and incorporate some HIIT training, I'll be dusting off my trusty Wattbike and aiming to do 2-3 sessions of 20-30 min each week from now on
    These will include a 10-15 minute warm up and then a series of 5-10 x 30 second sprints (building the number up as I regain some bike fitness) with long 2+ minute recoveries between each rep.
    The theory behind this is to try to work on some high intensity fitness without the injury risk associated with running really hard.
  • Finally, I'm going to set up a pull-up bar and press-up station in my garden to start to work on an upper body circuit training session twice per week. This is in a bid to stop my upper body losing all conditioning for when I return to the swimming pool later this year. I therefore expect to feel some horrendous DOMS (delayed onset muscle soreness) in the coming weeks whilst adapting to this….

What's your preferred training strategy during an enforced lay-off? Let us know by emailing