Day 3 goes to the floor and works the middle of your body. The card returns to the layout you met on Day 1 - one instruction at the top, 3 sets in total, five exercises to work through in order - so you already know the drill: run the whole list, rest two minutes, repeat, three rounds altogether. What is new is the last item. Four of the exercises are measured in reps, but the fifth reads 5-count hold, and a count is simply a steady second ticked off in your head. A hold means precisely what it says: you get into the position shown and stay there without moving until the count runs out. It lands at the end of the circuit because it is part of the circuit, and by then you will feel exactly why it was put there.

Your core is not one muscle and it is not just the part you can see. It is the whole belt of muscle wrapping your middle, and its actual job in daily life is to hold your spine steady while your arms and legs get on with things. Today's five exercises approach it from different directions on purpose. Crunches curl the upper body toward the hips and work the abs at the front. Sitting twists rotate the torso and bring in the muscles at the sides of your waist. Flutter kicks, leg raises and the hold all work from below - the legs move or hang while the lower abs hold the position, which is where most beginners discover they have lower abs at all. Notice the numbers drop for the last two exercises, down to 5 reps and a 5-count: that is not a printing slip, it is because those are the hardest items on the card and they arrive when you are already tired.

Crunches: lie on your back with knees bent and feet flat, hands beside your head rather than laced behind it, and curl your shoulders off the floor a few inches - your lower back stays down and your neck stays relaxed, so do not pull on your head. Sitting twists: sit with knees bent and both feet on the floor, lean back slightly, bring your hands together in front of your chest and rotate your torso from one side to the other. Flutter kicks: lying on your back with your head and shoulders slightly lifted, hold both legs straight and off the floor and alternate them up and down in small scissoring movements. Leg raises: from the same position, keep both legs straight and lift them together, then lower them slowly without letting your heels touch down. The 5-count hold finishes it - legs straight and held partway, somewhere in the middle of that range, arms by your sides, and the only instruction is do not move.

Your abs are not a decorative panel bolted to your front - today is the first time you have asked them to do the job they were actually built for.

Make it Harder: Stretch the 5-count hold to a 15-count on all three rounds and keep everything else exactly as written.

Make it Easier: Slide your hands palm-down under your hips for the flutter kicks, the leg raises and the hold - it supports your lower back and takes the strain straight out of it.