How we reported this: The writer, Erica Sloan, is a health journalist. She interviewed four experts for additional context on how the body responds to detraining over weeks to months. Improving your physical fitness—whether it’s to excel at a sport like running or lifting, or simply to stay active and healthy as you age—hinges on regular exercise.
So when you have to stop working out for any reason, it’s natural to wonder how, and how soon, your body will notice. But “if the pause is longer, some of the adaptations we’ve built through training can begin to diminish,” Crockford said. The timeline for detraining (aka, the loss of fitness gains such as strength or stamina with stopping exercise), is a “sliding scale,” Kevin Murach, associate professor of Nutrition and Exercise Physiology and principal investigator of the Molecular Muscle Mass Regulation Laboratory at the University of Missouri, told Outside.
Someone who cuts out all movement, for instance due to injury or illness, will have a quicker drop-off in fitness than a person who stops hitting the gym, for instance, while continuing to walk and move about their day. But overall, the trajectory follows a uniform pattern in the body, with decreases in aerobic capacity and psychological shifts occurring first, then muscular changes hitting later. Keep reading for the details on how stopping exercise affects key body systems over time.
With a week off, “we can be assured that there’s really no change in fitness,” Greg Grosicki, staff research scientist at wearable health and fitness technology brand WHOOP, told Outside. If anything, there can be “very, very minor reductions” in plasma volume, or the amount of fluid in your blood, he said. (Research shows that, in endurance athletes, plasma volume can fall by five percent with a couple of days off of exercising.) Without the strain of exercise, your heart no longer needs to shuttle as much blood to your muscles and to the surface of your skin to cool you down. This decrease in cardiac output can lead to a small drop in VO₂ max, or the amount of oxygen your body can use during exercise, Farah Hameed, medical director of Women’s Health Rehabilitation at NewYork-Presbyterian/Columbia University Irving Medical Center, told Outside.
As Outside previously reported, a study of runners and cyclists found that VO₂max can decline by seven percent 12 days after stopping training. In this window, you might find cardio exercises tougher or feel wiped out more quickly. Your muscles might appear a little smaller or less visible because of “shifts of glycogen and water stores,” Hameed explains, “but this can quickly revert once you start working out again.” Overall, strength won’t decrease yet, Murach said.
He added that many people who resistance-train only target a given muscle once a week and still gain strength. Exercise can be such a mood-booster that you might feel a little down or less joyful within even a day of stopping, Grosicki said. By this point, a loss of cardiorespiratory fitness—or how efficiently your heart, lungs, and blood vessels supply blood to your muscles—can become more noticeable.
Extract — continue reading at the source.
