How Fast Does Fitness Fade

Everyone knows that fitness takes consistency and self-discipline, with weeks or months of hard work needed before the benefits of exercise are recognised. What's not so clear, however, is just how long these benefits stick around once you've taken your foot off the fitness pedal. How fast does fitness fade? Can you have large gaps and still benefit from past work? What is the point in doing all this cardio if it just goes away in time?

Whether you're an ultra-marathon runner, a regular gym-goer, or someone who walks a few times a week, you're likely to lose half of your fitness if you don't train for a week. That's right, while it takes weeks to feel the benefits of regular exercise, according to sports scientist Tony Boutagy, "You're only as good as your last training session, [meaning] you only get health benefits from a session for up to about 48 hours afterwards." Nigel Stepto, associate professor in exercise physiology at Victoria University, agrees, saying "Of course the marathon runner's fitness would still be greater than someone whose main exercise is walking - they were fitter in the first place. But after a week of no training, both would be half as fit as they were the last time they worked out."

However, while no-one is immune to this deconditioning effect, it's not time to give up hope just yet. There is some evidence suggesting that fitter people who have been exercising for longer hold onto their fitness longer than those just starting out, with some forms of fitness more immune to fading than others. For example, while cardio fitness levels drop off very quickly when you take a break, aerobic fitness is only one component of overall fitness along with flexibility/balance and musculoskeletal strength.

Aerobic fitness describes the ability of your lungs, heart, and blood vessels to take in oxygen and transport it to your muscles. This is necessary to produce energy for body movement, with the heart needing to work harder when you lose fitness in order to get enough blood and oxygen to your deconditioned muscles. After a prolonged break, there is a higher demand for the blood to bring oxygen and remove carbon dioxide, meaning it's much harder to perform the exact same exercise session as before.

Muscle strength is also compromised after a long break, although it fades slower than aerobic fitness. According to Dr Boutagy, "You lose the cross-sectional surface area of your type two muscle fibres... Muscle fibres have a genetic size to them. If you go below that size, they self-destruct and turn into connective tissue... within two weeks you'll probably start to show a 7-10% loss in strength levels... Most data suggests that you'll lose at least 70% of the adaptation you've built through exercise after about three months." Balance and flexibility also stick around much longer than cardio fitness, although once again, nothing is immune to inactivity.

If you're starting from scratch when it comes to fitness, there is some good news. "The further you are from your fitness potential , the more profound your results will be in the first 12 weeks," Dr Boutagy said, adding "Studies are unanimous that beginners can pretty much double their strength within this time... In terms of cardio, most studies show that within three to four weeks you can improve your VO2 [your maximum rate of oxygen consumption] somewhere between 20% and 30% using interval training,"


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