Alex Welburn is currently studying for a PhD in critical power and coaching riders including privateer bike racer Joe Laverick. Prior to returning to academia, he rode for Great Britain in mountain biking and cyclocross before making the move to road where he rather rapidly graduated from third to first cat. Welburn’s high-performing palmarès came off the back of 14 to 20 hours of training each week. Riding was consistent and progressive, until the metaphorical wheels rolled off.
“As Covid restrictions eased, I decided to go on a bike-packing adventure that comprised around 24-30 hours of riding in four days,” he reflects. “Unfortunately, my knee just didn’t agree with my choice. I had a leg spasm, intense knee pain and couldn’t cycle. It was not fun!”
Welburn had two months of no, or very little, training. “I felt sluggish, lazy and irritable. Thankfully, I didn’t really put on weight but I did lose around 40 watts from my FTP. It was all very frustrating.”
Time off the bike is the road cyclist’s nemesis, but whether it’s through injury, life, the universe or everything, at times it simply can’t be avoided. Which doesn’t make it any easier as you stand there, facing the full-length mirror dressed only in a cloak of melancholy, a tear drifting down your cheek, while listening to Joni Mitchell, “Don’t know what you’ve got till it’s gone…” It’s a physical and mental battle. But one you can win by arming yourself with knowledge.
Fitness matters
“The start of the detraining process varies depending on the rider’s fitness level,” says Team TotalEnergies coach Luca Filipas, who has a PhD in sport science and co-authored a detraining meta-analysis in 2024. “The more trained a rider is, the higher their fitness level and the earlier the detraining process will begin. In fact, for professional riders, detraining can begin after just three days of inactivity. That’s because their training volume is high and their bodies are accustomed to receiving frequent stimuli. As a result, the body remains in that specific physiological state due to the consistent workload. Once that stimulus is removed, the rider’s fitness level declines almost immediately.”
“Conversely, for riders who train less frequently and are further from their genetic and physiological performance peak, the detraining process starts much later,” adds Filipas. “For someone training twice a week, even after five to six days of inactivity, there’s virtually no loss of fitness.”
So, there you have it: if you want to delay the detraining process, simply ride very little in the first place. Feature finished…
…or maybe not. “In the long term, someone who’s well-conditioned would ultimately expect fitness losses to be fewer than a rider who’s new to the sport,” says James Hopker, professor of sport science at the University of Kent, England, and an expert on endurance training. “Either way, fitness losses are similar to fitness gains in that they follow a linear response. You might lose fitness quite quickly but they plateau over time. It’s just that fitter individuals hold onto a good level of fitness for longer.”
Experience fights the ageing process
It’s not just your fitness that impacts how steep or shallow a fall you endure from periods off the bike. “Age is a determining factor, too,” says Filipas. “As the years roll by, detraining tends to occur more rapidly.”
Depressing news, for the 40-year-old-plussers at least. But resist placing the needle back on Joni. There is good news. Filipas’ far-reaching paper revealed that there’s evidence that in younger riders, detraining leads to a swift decline in VO2max and a reduction in endurance capacity, whereas older riders “display diminished glycation and mechanical stress in their connective tissue, potentially playing a role in their capacity to sustain endurance levels despite experiencing detraining”.
In other words, while older riders sadly endure “notable declines in cardiovascular function and endurance capacity following detraining”, they sustain certain physiological adaptations acquired through lifelong riding, “which could mitigate the effects of detraining”. But maybe not if they’re built like André Greipel.
“A rider’s anthropometric characteristics can influence the detraining process,” says Filipas. “Evidence suggests that athletes with greater muscle mass tend to experience greater losses during detraining and also take longer to recover during retraining compared to athletes with smaller muscle mass.”
Physiological downfall of detraining
It’s clear that detraining impairs cycling progress. That’s obvious. But why? What’s happening beneath your physiological lid?
“As a rule of thumb, the things that are quickest to adapt when you start riding are also the quickest to ‘de-adapt’ when you stop riding,” says Hopker. “So, the quickest thing you lose is water from your blood plasma. You lose it because your body doesn’t need to deliver oxygen to the working muscles in the same way. The body likes to live in an even keel where the demands of the body are met by the body’s ability to meet those demands. When you start taking those demands away, the body doesn’t need to deliver oxygen in the same way.”
This semi-drought results in a cascade of detrimental physiological changes. Less blood plasma – the part of the blood that carries platelets, red blood cells and white blood cells – means less blood pumped out of the heart (stroke volume). That then means your heart has to beat faster for the same cardiac output as before. Cardiac output is the amount of blood the heart pumps out in one minute. From a riding perspective, on your return, if you glance at your sports watch or bike computer, you’ll see that your heart rate at respective power outputs will be higher than when you were ‘trained’. It'll be higher at rest, too.
According to 1986 research into cardiovascular responses to detraining, a period of detraining lasting between two and four weeks results in a 9% reduction of blood volume [amount of blood circulating in your system] linked to a 12% drop in plasma volume.
“The other major change that happens most quickly is losing ‘enzymatic capacity’ from your mitochondria,” says Hopker. “Your mitochondria are important in terms of shifting energy around the body and how it’s used, so as soon as you stop exercising, these enzymatic benefits of training are lost. In turn, you’re unable to process oxygen as effectively because you’re tapping into fewer mitochondria, meaning you process energy less effectively.”
Your fading mitochondria limits your ability to exercise aerobically, meaning you increasingly rely on anaerobic metabolism to generate energy. “You’ll then see your lactate threshold reduce,” says Hopker. All in all, you simply become worse at creating energy through fat and carbohydrate.
Your muscles aren’t let off, of course. A period off the bike sees a reduction in capillary density, a decrease in oxidative enzymes and a decline in enzymes involved in glycogen synthesis. All of this is bad news, especially when you assess their impact on those physiological metrics that you know equal faster cycling.
Metric downturn
“There was a meta-analysis a few years ago that reviewed about 60 detaining studies and the majority of studies reported around a five to 10% fitness drop in a four-week period, so the reductions are substantial,” says Hopker. “Your aerobic capacity, or VO2max, is one of the first metrics to be affected because of that loss in terms of blood volume and hampering of oxygen delivery. The literature says you’re looking at a four to 10% drop there.”
As mentioned above, your lactate threshold also takes a hit and, not surprisingly, so does your power output. And again there’s an age-related element to proceedings. 1998 research comparing the impact of detraining between the ages showed that while two months of detraining hit younger riders’ maximum power output by around 3.5%, that cranked up to 8.8% for older riders. Further research reveals that we all run out of steam sooner, with research showing a 9% drop in a time-to-exhaustion test after just two weeks of no training.
The good news is that several studies have concluded that you’ll still squeeze into your uber-form-fitting Italian apparel, for a short time anyway, as body weight and body composition aren’t really affected by four weeks of detraining. The bad news is that science says this changes after four weeks.
This doesn’t marry with Welburn’s experience, who didn’t ply the weight on, albeit he adapted his diet and reduced calorie intake. “That helped during the time off the bike, mentally anyway,” he says. “It probably helped on my return, too.”
Importance of muscle memory
Which brings us to the light at the end of the detraining tunnel: the retraining period. How did this look to Welburn? “After two months of very little exercise, my return to cycling started with baby steps, building longer sessions by around 30 minutes a week as I didn’t want any setbacks. It was a conservative approach, but I’d heeded the physio’s advice.
“When you return to cycling after a lay-off, be sensible with your return and, if you follow metrics, adjust your training zones accordingly. The knee healed but it took around two to three months before I felt my normal self again.”
That’s the anecdotal. How does it match the science? “We know from the literature that the retraining process is faster than the detraining process,” says Filipas. “But it’s not possible to provide a precise figure for how much faster, as this depends on numerous factors: the duration of the detraining period, what activities were maintained during detraining, individual characteristics, age…
“But, in general, we estimate that the retraining process is around 30-40% shorter than the detraining process. For example, if a certain level of fitness is lost over 10 weeks of detraining, it’s likely that the same level of fitness can be regained in about six to seven weeks of retraining.”
So, a little quicker than Welburn’s experience but, as Filipas says, recovery is an individual thing, albeit it does go against recent scientific evidence that Welburn’s body should have remembered his high level of fitness.
“There’s persuasive evidence that muscle memory is a thing,” says Hopker. “The fact that once you’ve trained your muscles, even when detrained you retain some form of ‘fitness memory’ from a genetic standpoint. That means if you’re fit and experienced, your genes will remember it; in other words, you’ll regain fitness faster than a novice.”
The truth behind the adage “use it or lose it” is down to the extra nuclei acquired by a muscle fibre during regular cycling. A 2019 study by Professor Lawrence Schwartz in the journal Frontiers in Physiology showed that those extra nuclei persist even after a muscle shrinks from disuse, meaning they can be mobilised more rapidly when returning to exercise.
That’s good news for the consistent riders amongst us, though the ideal is not to rely on your memories but, if at all possible, keep on moving.
Intensity key (if possible)
“During the detraining period, if it’s possible to maintain strength sessions or short, high-intensity sessions, research shows that this significantly slows down the detraining process,” says Filipas. “These are the two key elements to prioritise.”
Hopker agrees that intensity is key with an indoor session on the likes of Rouvy perfect. “Bent Ronnestad [professor in exercise physiology at Norway University of Applied Science, who Rouleur’s come across before when digging into the shuddering vibrations of Paris-Roubaix] undertook research comparing a long ride with a long ride featuring 30-second sprint intervals, and showed that the intervals session was a more potent session to maintain aerobic metrics,” says Hopker.
“It was more aimed at maintenance efforts for rider maintenance work during the off-season but it could be used by riders who simply can’t ride regularly for four weeks. Even if it’s just one one-hour weekly session with 30-second intervals that should maintain fitness, albeit after four weeks it’s not as effective.”
If your lay-off is injury-related but it’s still physically possible, Filipas suggests aerobic alternatives like swimming or even upper-body strength work in the gym, as long as both are high-intensity.
Pyramidal model of return
“And when you’re recovered and strong enough to return to your bike, start with an intensity distribution focused on what’s called a ‘pyramidal model’, where you emphasise low-intensity work with moderate-intensity sessions,” he says. “This should continue until the previous training volume is fully restored.
“Once the pre-detraining volume is regained, high-intensity sessions can gradually be introduced, potentially transitioning to a polarised model if deemed necessary. But the priority is to begin with a pyramidal model and gradually rebuild the training volume prior to the stop. Too much hard riding too soon would create a ‘short blanket’ effect, where performance might seem good for a few weeks but would gradually decline due to the lack of a strong aerobic foundation.”
As much as cycling courses through our veins, time off the bike is inevitable. While that makes it hard to placate your partner who questioned your latest five-grand Pinarello outlay, it’s even harder (depending on the ferocity of your partner, of course) to retain and recover your fitness, unless you arm yourself with knowledge. That means two key takeaways: if physically possible, limit the detraining process via alternate aerobic activities like swimming and high-intensity efforts. Conversely, when it comes to your full-blown recovery on the bike, it’s all about rebuilding a solid aerobic base, which means endurance work and avoiding the rapid introduction of too much high-intensity training. Do that and you can banish Joni to history…
