Categories: Health Training
Tags: fitness

How long does it take to start losing fitness?

July 25, 2017

Your goal race is just two months away, and you’ve been crushing your training all season long. You’re feeling strong, fast, and fit – not to mention more confident than you’ve felt in years.

But then life happens. Maybe you get sick and sidelined for a while, or perhaps an injury decides to knock you off your plan. Or maybe work deadlines, family obligations, and other commitments start to take precedence over your precious training time. What does that mean for your training, your fitness, and your rapidly approaching race day? 

Read on for the lowdown on losing fitness – and how to regain your strength.

If you’re generally fit, don’t panic about missing a few days of training

Even if they’re crucial ones, like tempo days or long run days. But if you start missing more, your fitness will eventually begin to dwindle. (Muscle memory doesn’t last forever, after all.) “It’s safe to say that within two weeks, an endurance athlete can see a significant degradation in fitness,” says Jonathan Cane, exercise physiologist and founder of City Coach Multisport in New York City.

So beyond your workouts feeling a little harder once you get back at it, how do you know that you’ve lost aerobic fitness? “There are some variables you can easily measure,” says Cane. “Resting heart rate is one good indicator.” If your resting heart rate has significantly increased during your time off, there’s a good chance the fitness you worked hard to build has started to fade.

After a day of missed workouts, not much will change, Cane says. But after two weeks, you may experience a decrease in VO2 max and lactate threshold, as well as changes in blood enzymes associated with cardiovascular fitness. Go a month sans fitness and you can expect significantly decreased glycogen storage – “if not sooner,” Cane adds. (Studies have shown that after four weeks of inactivity, endurance cyclists saw a 20 percent decrease in their VO2 max. After 12 days of inactivity their blood enzymes associated with endurance performance decreased by 50 percent.)

If you’ve been sidelined for a year, Cane says your blood volume will likely have returned to “normal, pre-training levels”. Capillary density appears to be pretty resilient with detraining, but it will likely show significant losses over that much time.

as much as it may hurt trying to get back in shape, it’s easier for once-fit people to bounce back

The good news for regular exercisers is that as much as it may hurt trying to get back in shape, it’s easier for once-fit people to bounce back into shape than it is for people who rarely work out. “It’s definitely harder to start from scratch,” Cane says. “Even months of detraining won’t take you back to the levels of a sedentary person.”

Age is a factor, too: Older people lose fitness faster, and younger people generally regain it quicker.

So what can you do to avoid being totally sedentary during forced time off? “Cross-train if possible when you’re injured,” Cane advises. When you can’t run, ask your doctor if you can swim, bike, or strength train. If cycling is out, ask about yoga or Pilates.

“If you’re simply too busy to commit to normal training time, try to at least slow the losses with short, intense bouts of exercise,” Cane suggests. “Depending on your sport and your goals that may not be enough to maintain your fitness, but it will at least help stem the tide.”

In the spotlight

Jonathan Cane

Jonathan Cane

Jonathan Cane is an exercise physiologist and is the founder of City Coach Multisport in New York City.