Popsugar Health & Fitness Crossfit 30-Minute CrossFit HIIT Workout Build Strength and Endurance With This Heart-Pumping 30-Minute CrossFit HIIT Workout 21 September 2019 by Jenny Sugar View On One Page Photo 3 of 6 ADVERTISEMENT () Start Slideshow Share This Link Copy ← Use Arrow Keys → 3 Box Jumps Stand with your feet slightly wider than hips-width distance apart in front of a sturdy box that's six to 24 (or more!) inches tall. Bend your knees and swing your arms back. Jump onto the top of the box with both feet, swinging your arms forward to give you a little momentum. Step one foot at a time back to the floor, or jump down softly with both feet. This counts as one rep. Do as many box jumps as you can for 40 seconds, followed by a 20-second rest. Previous Next Start Slideshow CrossFitWorkouts