Browse all expert articles, guides, and tools related to Fitness.
Sleep science is clear: most adults need 7–9 hours. But the exact amount depends on your age — and more important than hours is timing your wake-up to the end of a 90-minute sleep cycle. Here is what the research says and how to use a sleep calculator.
Your maximum heart rate determines your five training zones — from fat-burning to peak performance. The old 220-minus-age formula is outdated. Here is the more accurate Tanaka formula, a zone table for every age, and how to use each zone.
"Drink 8 glasses a day" is everywhere — but it has no scientific basis. Your actual water needs depend on your body weight, activity level, climate, and diet. Here is the formula and a table that tells you your exact target.
Body fat percentage is a more accurate measure of health than BMI. But how is it calculated, what is a healthy range for men and women, and which measurement method is most accessible? This guide covers everything.
