THE BLOG
12/18/2014 10:22 am ET Updated Feb 17, 2015

Taking Time Off From Your Workouts During the Holidays? How Fast You Lose Fitness and Tips to Minimize the Hit

Jordan Siemens via Getty Images

So you invested a respectable amount of hours working out this year. Maybe a couple of hundred or more? Ever wonder how long you have before your hard work starts to come undone? With the holidays upon us, taking some time off may be inevitable whether it's due to travel, one of those nasty bugs going around or the myriad of obligatory time sucks (like five hours of cyber shopping a day) that happen this time of year.

The truth is it doesn't take long for the body to start losing strength, endurance and aerobic power and anaerobic capacity. In just days or weeks some of these qualities can start to decline. The adage "use it or lose it" has more scientific relevance than you may think. You work out hard and the body adapts by getting fitter, you stop and that hard work starts to deteriorate. Stop training for long enough, and you could lose it all and it might take longer to get it back depending on what level of fitness you were at before you stopped.

Three key things to know:

1. How much time will you be taking off? If you're going to lay off your workouts for more than a month (four weeks or less is considered "short term" by some research standards), don't be shocked at what happens to your body. Your metabolism will change meaning you will start to burn less fat and store more of it.

2. Are you a cardio junkie or a strength beast? If you're more about the heart rate training (steady state endurance or interval training), you'll start losing your mojo faster than if you're a pumper of iron.

Cardiovascular fitness is measured by VO2 max, which is how much of the oxygen that you take in, actually gets used. Somewhere between two and four weeks of no training, that VO2 max really starts to slide steadily downhill until it eventually levels off. In other words, the cardiovascular system detrains rapidly with inactivity. This is mainly because less blood volume is being pushed around which means the heart is pumping less blood with every beat, which lowers the VO2 max. Just like any muscle in your legs or arms will shrink with no use, so does your heart... only faster.

However, if you're all about pumping those weights or doing short sprints (read: strength training), you've got more time on your side. Detraining effects on strength are pretty minimal in the first two weeks. One study found that taking a two week break after following a strength training program, weight lifters showed only slight declines in bench press, squat and knee extension strength. When swimmers stop training there is no change in their muscle glycolytic enzymes, which affect strength, for at least four weeks. However, their aerobic energy system declines faster. That means short distance sprint times are unaffected by a brief hiatus of up to a month, but endurance performance may show a significant decline in as little as two weeks.

3. How long have you been training for? The hit your fitness will take has a lot to do with your level of fitness before you go on a training hiatus. The longer you've been fit for, the longer you'll maintain your fitness.

If you're an athlete, or at least on some kind of cardio training schedule, in four weeks or less of inactivity your VO2 max will drop between 4 percent and 14 percent. After four weeks, that drop will be between 6 percent and 20 percent.

If you're a newbie to doing cardio, taking off for up to four weeks won't do much damage to whatever cardiovascular fitness you have. VO2 max will only decline a mere 3.6 percent to 6 percent. However, if you give up on your training for longer than a month, you're looking at a total loss of any gains you made!

On the flip side, muscular strength gains stick around longer. A well-trained person may only lose up to 12% of their strength even if they don't lift a weight for more than a month! A newly trained person's strength will fare differently. In up to four weeks or less, they will only lose 2 percent to 3 percent, but after a month off, the decline in strength can be anywhere between 16 percent and 27 percent.

Here's what you can do to prevent losing what you've gained:

1. Try to fit in some short, intense workouts. If possible, just cut down the frequency of your workouts by one to two-thirds, but keep the intensity up. If you work out six days a week for example, aim for two to four workouts a week. They key is not how often or how long you work out for, but how intense. You can feasibly stave off losses to your cardiovascular fitness by doing a few short intense workouts. When I'm on vacay, it's all about the HIITs. I'll of do 20 minutes of Tabata training (four minute bouts of :20 seconds all out work followed by :10 seconds of rest for eight rounds -- there's an app for it!) or, ten minutes of doing :50 seconds of hard work followed by :10 seconds of rest. I'll pick five exercises that fatigue me in 50 seconds and go through them twice. Wham bam thank you HIITs!

2. Cross-train. It's good for the body and good for the brain! By doing workouts your body is unaccustomed to, you'll burn more calories, develop new neural pathways and new skills plus avoid burnout. It's the old principle of "muscle confusion" you've no doubt heard about by now. We all like surprises from time to time -- so does your body.

3. If you have to choose between a cardio workout and a strength-training workout while you're on vacation, go for the heart rate. Remember it's the cardio system that declines faster than your strength. While shorter and more intense is ideal, when you're traveling or not able to do your regular routine, at least get in a few moderate intensity cardio sessions for about 20 to 40 minutes. Moderate intensity is around 60 to 70 percent of your max heart rate. If you don't have a heart rate monitor or Santa didn't leave you a new one under the tree, you should feel like you're working out at a level six or seven on a scale of one to 10 (10 being the hardest).

Note: If you're taking time off to nurse an illness, check with your doctor before doing any kind of intense workouts. Under certain circumstances, you can do light to moderate exercise when you have a bug, but intense workouts can make you vulnerable to getting sicker.