Whether you’re trying to lean down or bulk up, building muscle is no small feat. So as tempting as it is to shirk your strength-training routine while on vacation, here’s an incentive to keep at it: A new study has found that two weeks is all it takes for muscle strength to dwindle by as much as 30 percent in young adults and 25 percent in older adults. According to the researchers, those two weeks off become the equivalent of aging a staggering 40 to 50 years and requires three times the amount of time you were inactive to get your muscle mass back (how’s that for motivation?). If you can remain physically active on a consistent basis, you shouldn’t have to worry about a significant loss of muscle strength. Make it a habit to do a round of push-ups when you get out of bed, take a yoga class or swim laps in the hotel pool if you don’t have access to a gym. What are some ways you keep your muscles at work on vacation? Tell us in the comments!