The warm-up classic that still gets the blood pumping.
Land soft on the balls of your feet and keep your knees slightly bent throughout.
The jumping jack is rhythmic full-body cardio, every rep bounces you off the balls of the feet while the arms sweep overhead, so the heart rate climbs fast with the shoulders and calves doing continuous work to drive and absorb each cycle. Nothing to set up, nowhere to hide, just steady effort for time. It earns its place as the fastest way to raise body temperature at the start of a session or keep the pulse up between strength sets.
One of the best all-rounders. A minute or two raises your heart rate, warms the shoulders through a full overhead sweep, and primes the calves and ankles for anything explosive coming later in the session.
For a warm-up, 30 to 60 seconds at an easy rhythm does the job. As a conditioning tool, try intervals, something like 40 seconds on and 20 off, repeated for several rounds, scaling the pace to your fitness.
Step jacks are the standard swap, step one foot out at a time while the arms do the full overhead sweep. You keep the rhythm and most of the heart-rate benefit with almost no impact.
