When it comes to cardiovascular fitness and muscle strength, the adage is true: Use it or lose it. While regular exercise can improve heart health and increase strength and mobility, taking weeks or months off can reverse many of those benefits.
This is not to say that rest days are not important. In general, short breaks can help you recharge physically and mentally, but whenever possible, avoid extending your time off for too long so that jumping back on the bandwagon doesn’t feel too challenging or miserable.
“Your body adapts to the stimulus you provide,” says Dr. Kevin Stone, an orthopedic surgeon and the author of the book “Play Forever: How to Recover From Injury and Thrive.” “Your muscles get used to the stress and the testosterone, the adrenaline and endorphins – all the wonderful things that circulate through exercise. When you take it away, the body starts a muscle loss program.”
What does it mean to lose fitness?
To understand the phenomenon of fitness loss, it is helpful to think about how activity and therefore inactivity affect your cardiovascular system and muscle strength. Because regular exercise helps your body deliver oxygen and nutrients to tissues more efficiently, one of the first things to decrease when you become inactive is your cardiovascular endurance, says Edward Coyle, a professor of kinesiology and health education at the University of Texas at Austin.
After just a few days of inactivity, the volume of blood plasma circulating in your body decreases, Dr. Coyle said, leading to a series of other cardiovascular changes. After 12 days, studies show that the total amount of blood the heart pumps each minute decreases, along with the amount of oxygen-rich blood available to muscles and other cells – measured as the VO2 max.
If you return to the gym at this point, you will notice only minor differences in performance, Dr Coyle said. Your heart rate may be a little faster and your breathing may be heavier as your body works harder to pump blood and oxygen to where it is needed.
Scientists have found that it is around the three-week mark that people experience the biggest changes in their ability to get through a workout, as energy produced by mitochondria for muscle cells drops significantly. “This means that exercise will be more exhausting,” Dr. Coyle said.
Strength declines less rapidly than cardiovascular health. After eight weeks, inactivity finally begins to affect the size and strength of your muscles. For weightlifting or strength training, reduce the maximum amount you can lift, as well as the number of repetitions you can manage, Dr. Coyle said. You are also more likely to experience muscle soreness a day or two after the workout.
The degree to which different people experience a decline in fitness depends on age, genetics, lifestyle, diet and previous level of fitness. Studies show that older adults lose fitness at nearly twice the rate of 20- to 30-year-olds. And while people who train consistently for months or years can experience fitness loss at the same rate as recreational exercisers and weekend warriors, athletes who start at a higher fitness level “have more to lose in absolute terms,” Dr. Coyle said.
What can you do to curb fitness loss?
Although the cardiovascular and muscular changes that occur after a long break may sound dramatic, the good news is that most people do not cut out all activity in the same way that participants are often instructed to do in an exercise study.
If you have to travel or stay in because of bad weather, doing something is still better than nothing, Dr Coyle said. Swap dumbbells for bodyweight exercises. Try smaller “exercise bites” throughout the day, take the stairs as much as you can, or better yet, set a goal to do a few short high-intensity interval workouts.
“If you spend just a few minutes a day doing interval exercises, it is sufficient to increase the blood volume and keep mitochondria relatively high,” said Dr. Coyle said.
If you’re a competitive athlete, reducing the intensity or frequency of training just before or after a big race or game can actually be beneficial, as long as you’re intentional about it. For example, many athletes plan for a two- or three-week taper to give their bodies time to restore their glycogen fuel tank and allow muscles to recover.
Those who need to take longer breaks can try cross-training or switch to another sport, such as skating or swimming. Or perhaps focus instead on improving balance, through aerobics classes or dance to keep the same muscles active in different ways.
“Overall fitness is a combination of many factors,” Dr Stone said. “It’s not just muscle strength and cardiovascular fitness.”
How long does it take to make a return?
If you haven’t been physically active for a while, don’t lose heart. Just as off-seasons are a regular part of any sport, it is also possible – and easier – for regular exercisers to get back into shape.
Research shows that although extended breaks significantly reduce fitness, most exercisers’ levels remain above those who have been sedentary all their lives. For example, while muscle fibers may shrink during long breaks, they don’t completely disappear and retain a molecular “muscle memory” that can help them bounce back months after you stop exercising. In other words, you are already set up to regain strength and endurance much faster than when you first started.
“You can regain about half of your fitness in 10 to 14 days with moderately hard workouts,” Dr. Coyle said.
After this initial period of retraining, the amount of time it takes to get the rest of your fitness back to pre-breaking levels can vary depending on how much you have to catch up. One study found that older adults needed less than eight weeks of retraining after a 12-week break. Other evidence suggests that competitive athletes may need to train for two to three times as long as they took off.
When rebuilding your fitness, start by setting a goal to exercise for a certain amount of time each day, without worrying about your strength or intensity, Dr. Coyle said. Once you can comfortably walk or jog for 30 minutes a day for two or three weeks, you can begin to increase your pace to a jog. If you want to return to lifting weights at the gym, start with a lower load and then gradually add more.
Many personal trainers recommend increasing by no more than 10 percent each week. But rather than following an arbitrary number, adjust your routine based on how your body feels.
If you can’t afford several weeks of retraining, or simply want to get in shape faster, you can do more intense workouts or incorporate interval training to speed up the process. “The higher the intensity,” said dr. Coyle said, “the faster the rebound.”