Day 4 pairs jumping cardio with the standing arm block, all inside the same circuit you have been running - one lap through the card, rested and repeated to your level. The push-up-top 10-count hold opens it, then the jacks arrive in a rising family of three.
Step jacks are the low-impact version, stepping one foot out and raising the arms without a jump. Jumping jacks add the hop, feet out and arms overhead together. Seal jacks keep the jump but sweep the arms wide in front of the chest and back rather than overhead, so the chest and upper back do the work. The session then closes with the arm trio you know from Day 1 - bicep extensions, shoulder taps pressing overhead, and side shoulder taps opening wide - counts split evenly across both sides.
On the jacks, land through the whole foot and stay springy in the knees rather than stiff. Match the arms to the legs so the movement stays coordinated and continuous - the point is to keep the rhythm unbroken. In the arm block, full extension is everything: reach all the way up on the shoulder taps and all the way out on the side version, keeping the pace deliberate.
Cardio to lift the heart rate, arm work to steady the breath - one lap covers both and the next one covers them again.
Make it Harder: Turn every jack into its jumping version and drive the arms with real intent so the shoulders share the cardio load.
Make it Easier: Use the step version of each jack and keep the arm work slow and full rather than fast.
