Look, I’m gonna be straight with you – those online calculators that tell you exactly how many jumping jacks you need to burn 500 calories? They’re basically making educated guesses about your body.

Look, I used to think those “100 jumping jacks = 10 calories” calculators were gospel. Then I started paying attention to real people doing real workouts, and wow – was I wrong. Those generic formulas ...

Women's Health may earn commission from the links on this page, but we only feature products we believe in. Why Trust Us? Some exercises are more common than others when it comes to building a workout ...

Exercises that combine cardio and strength training are a one-way ticket to a more efficient workout, and squat jacks are one of the best moves around, explains certified personal trainer Lisa Tanker.

FITBOOK author Nina Ponath loves challenges—this time: 10 days of jumping jacks. Photo: Getty Images / Antonio_Diaz; Collage: FITBOOK Jumping jacks in all variations—FITBOOK author Nina Ponath did at ...