20 intervals · 30 s on / 15 s off · 15:00 · no equipment
Hard is the default: floor and feet-elevated push-ups, pistols, plyometrics. Easy swaps in incline and knee push-ups, box squats, supported lunges and step-back burpees. Every program is 4 rounds of 5 intervals, 30 seconds on and 15 off, no equipment beyond a couch or stair.
Elevation: "feet up" or "rear foot up" means a couch, bed edge or second stair. "Incline" means hands on a couch, table edge or the third stair. No surface available: do the floor version and slow the lowering to 4 seconds.