How Long Does It Take to Lose Your Running Fitness?
Whether it’s taking time off from running due to injury, taking a break to recover after a marathon, or a hectic life just getting in the way, we as runners are not great at missing training.
Sometimes we wonder if it is even okay to take a day off running when we have pain!
Not only does it remove one of the more enjoyable daily activities from your schedule, but there’s also the concern of losing fitness.
Most runners know it is important to take time off from running at the end of a season, and every runner who has spent any time injured has worried about losing their fitness while their body heals.
Or are we the only ones?
Today we will cover just how fast you lose aerobic fitness when you have to stop running. Hopefully it can put your mind at ease the next time you have to take a break.
Fortunately, as aerobic capacity and endurance are fairly easily to measure, there are some strong studies that give a good picture of the decline in fitness during time away from running.
Additionally, they also offer some insight into why you lose fitness, and from this we can help you with how to safely return to running…..without ending up back on the bench with another injury!
How Quickly Will Taking Time Off From Running Hurt Me?
One study conducted by Elizabeth Ready and Arthur Quinney, looked at the rise and fall in aerobic conditioning in a group of men who followed a cycling training program for nine weeks, then rested for nine weeks (detraining).
The twelve men in the experimental group rode hard for 30min four times a week for nine weeks, while the nine men in the control group remained sedentary.
All 21 men had their VO2 max and anaerobic threshold tested before the study and every three weeks afterwards for eighteen weeks (during the nine-week training intervention and for nine weeks of detraining).
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Interestingly, the control group had a slight increase in fitness too—perhaps because they were supplementing their sedentary lifestyle with a maximal aerobic test every three weeks!
After training ceased, anaerobic threshold and VO2 max dropped fairly rapidly.
After the first three weeks of “detraining,” the subjects’ anaerobic threshold had already dropped by almost 20%.
But don’t panic just yet:
The rate of decrease leveled off.
Even after nine weeks of (almost) no activity, the cyclists retained about 40% of their gain in fitness over their previous sedentary life.
However, Ready and Quinney did not use trained athletes, so it’s possible that the effects of detraining will be different in a trained athlete vs. a newly-trained one.
How quickly do you lose fitness when not able to run?
Edward Coyle et al. conducted a study on the topic of detraining in already-fit athletes.
Using seven endurance athletes with many years of training experience, Coyle et al. established baseline fitness levels, and measured how their fitness declined after 12, 21, 56, and 84 days off (for a total of twelve weeks).
The initial dropoff in fitness was fairly quick: after 12 days, levels of enzymes in the blood associated with endurance performance had decreased by 50%, and VO2 max had dropped by 7%.
But the reduction in fitness leveled out over the following weeks; the final level of the subjects’ VO2 max was still only 18% lower than when they’d begun.
Want the good news?
Some factors, like capillary density—the number of small blood vessels that grow deep into the muscles—did not seem to be affected at all by detraining.
These results suggest that trained athletes lose less fitness than sedentary people who have only recently started exercising.
If you rest after a marathon, what happens to running fitness?
A third study at Odense University in Denmark looked at practical implications of time away from training.
Klavs Madsen and colleagues used nine endurance athletes who regularly trained for eight hours per week.
Madsen et al. studied the effect of a four-week break from training with a ride-to-exhaustion on a stationary bike before and after the time off.
Though the study did not detect any statistically significant change in VO2 max, the subjects’ were able to cycle at 75% of VO2 max for 80 minutes before the study, and just over 60min after the study—a 20% decrease.
This is more relevant to runners in training, as it’s a closer approximation to preparing for a big race, followed by time off running to recover, like taking a week off after a marathon.
Peripheral factors in the muscles, including calcium and magnesium concentrations, and muscle glycogen storage, affected the body’s ability to exercise more than the core cardiovascular “engine.”
What’s the bottom line?
Nevertheless, a 20% change in a ride to exhaustion is fairly significant, so the effects of a month off training are going to have a big impact on performance.
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If I stop running for a few weeks, will I lose all my endurance and strength?
Combining the data from the studies results in good and bad news for runners who have to take time off.
Initial declines in fitness occur rapidly: There are measurable declines in fitness, and enzyme levels associated with performance drop by half in under two weeks.
These declines level off after several weeks of inactivity.
What if I have to take a lot of time off?
If you’ve been training for a long time, your “lifetime” aerobic conditioning is still mostly intact; long term gains in fitness are only minimally affected by time away from running.
You are likely to lose a larger portion of the more immediate gains of training: enzyme levels, glycogen storage, and muscular efficiency.
What does that mean?
Your more recent improvements are severely affected by time off.
There are few studies that have analyzed longer than three months away from activity, but an 80% retention of fitness after 12 weeks of inactivity in the Madsen study is a good sign.
How long does it take to regain fitness after time off running?
The results from Ready and Quinnely also suggest that it won’t take as long as you think to get back to your initial fitness.
Over nine weeks of training, the subjects increased their anaerobic threshold by 70%, but after nine weeks of inactivity, they had retained 40% of the initial increase.
It would not take them another nine weeks to get back to peak fitness level.
What’s the bottom line?
If you are taking some time away from running, realize that you will lose a significant portion of your fitness, and you will lose it fairly quickly, but your losses will taper off after several weeks, and you retain a portion of your initial fitness levels for a long time.
Is there anything to prevent fitness loss during time off running?
Cross-training is one way to hold off the initial drop in fitness.
Studies on aqua jogging suggest that you can maintain your conditioning for at least six weeks with a rigorous program.
But even if you don’t cross train, take comfort in knowing that your hard work is not lost, and that it won’t take nearly as much time or effort to regain your fitness level as it took to get there initially.
You can also read our study on Racing Well off Cross Training- Even if you are injured and listen to our podcast on cross training to get more reassurance that you can stay in shape through cross training.