How Fast Will I Lose My Swim Fitness?

Well, this is…different. Triathletes now find themselves in a strange spot—specifically, a dry spot. Training for the run and bike, strength training, core work, all continue apace for most of us, even if there are no races on the schedule. But options for swimming have abruptly dried up. Athletes who rely on pools, or even open water in many cases, are anxiously looking at months out of the water, leaving them to wonder, “How fast will I lose my swim fitness?”

There’s universal agreement among sport scientists, some swim fitness will be lost—there’s just no substitute for water. But there are ways to mitigate the decline.

Sports physiologist, triathlon coach, and Sports Science Coordinator for Spanish Aquatics Iñigo Mujika has studied swim detraining due to injury, illness, and intentional rest, but like everyone else, is now navigating uncharted waters. He has good news, bad news, and practical ideas for beached triathletes.

Swim fitness is a combination of cardiorespiratory, metabolic, and technical adaptations. The happy news? Most of the cardiorespiratory fitness required for swimming can be retained by running and biking. “Although running and cycling are dissimilar modalities (they involve different muscle groups and movement patterns), the muscle mass involved is large enough to retain such central adaptations,” Mujika explains.

As Mujika alluded, running and biking don’t do much for the upper body. “Declines in the [upper body] muscles’ respiratory capacity, mitochondrial enzyme activities, and glycogen levels are to be expected,” Mujika said. “These could probably be retained to some extent by exercising upper body muscle groups using similar-mode dryland training such as arm cranking, swim ergometer, swim bench pulling, or elastic band exercises.”

Stephen Seiler, professor of sport science at the University of Agder in Norway, suggested a bike ergometer adapted for hand cycling or a ski-poling ergometer might also use upper body muscle groups. Seiler recommended these dryland exercises three or four times/week, in addition to running and biking.

And now for the bad news, but you knew this. “Complete cessation of swim training has almost immediate negative consequences on power production in the water—around 7% drop in one week, 13% in four weeks,” Mujika said. “This is in addition to a loss in technique proficiency, as indicated by increased stroke rate and decreased stroke distance for a given submaximal swimming speed.”

The activities mentioned above—running, cycling, upper body exercises—can lessen the decline in technique, more so in age-group swimmers than elite competitors. “In elite triathletes, no amount of cycling or running is going to have a positive impact on swimming performance because of the highly specific nature of swim training, and because improvements in swimming performance require practicing swimming skills,” Mujika said. “Swim performance improvements in triathletes are more likely due to technical improvements rather than physiological adaptations.”

But there’s a happy ending. That water feel? Stephen Seiler says the neuromuscular pathways built by untold laps in the pool won’t fade that quickly, and will return quickly once dipped in water. If the infrastructure was there, it takes a lot less time to return to it than it took to build it.

Even visualizing swimming, used in the building phase, might help prevent its loss. “Strategies like imagery, visualization, and mental rehearsal may contribute to the retention of motor patterns in swimming,” Mujika said.

So, yes, your swim fitness has probably had a pretty solid decline. Luckily, there are things you can do to emerge from this as a physically and mentally stronger athlete. And as soon as we’re allowed to hop back in the pool, it should all come back pretty quickly.