Your heart rate zones may also shift as you age because they are based, at least in part, on your maximum heart rate. Age-predicted formulas such as 220 minus your age are useful starting points, but they are estimates, not personalized measurements. The American Heart Association specifically describes these numbers as general guides because individual maximum heart rates can vary considerably.

A recent study found that lifters who completed a short strength phase before transitioning into a traditional muscle building phase gained more muscle than those who spent the entire time training only for hypertrophy.

A fascinating new study published in Nature analyzed nearly 500,000 adults and compared their sleep habits with sophisticated measures of biological aging. Instead of simply looking at birthdays, researchers measured how quickly different organs throughout the body were actually aging using MRI scans, blood proteins, and metabolic markers. Their findings revealed something surprising. The people whose bodies appeared to age the slowest consistently slept between about 6.4 and 7.8 hours each nigh