I used to think planks were just something fitness influencers did for Instagram. Then I threw out my back moving a box of books and my physical therapist told me my core was essentially nonexistent. He prescribed planks. I rolled my eyes. Three months later, my back has not hurt since and I can hold a plank for two minutes without wanting to die. Here is the plan.

Why Planks Beat Crunches

Crunches only work your rectus abdominis — the six-pack muscle. Planks work everything: deep transverse abdominis, obliques, lower back, shoulders, glutes. That deep abdominal muscle is what actually stabilizes your spine. A strong six-pack with a weak deep core is like a car with a nice paint job and no engine. The plank builds the engine.

The 30-Day Progression

This takes three minutes total per day. Not three minutes straight — three minutes broken into sets. You can do this. I did this. I am not athletic.

• Week 1: 20-second hold, 40-second rest. Repeat 3 times. Total plank time: 60 seconds.
• Week 2: 30-second hold, 30-second rest. Repeat 3 times. Total plank time: 90 seconds.
• Week 3: 45-second hold, 15-second rest. Repeat 3 times. Total plank time: 2 minutes 15 seconds.
• Week 4: 60-second hold, three times with 30-second rests. Total plank time: 3 minutes.

Form Is Everything

A bad plank is worse than no plank. Elbows directly under shoulders. Body in one straight line from head to heels. Squeeze your glutes and thighs — this takes pressure off your lower back. If your lower back hurts, your hips are sagging. Raise them slightly and engage your abs harder.

Breathe. Most people hold their breath during planks and then wonder why they feel like they are dying after 20 seconds. Slow inhale through the nose, slow exhale through the mouth.

Do the plank first thing in the morning before your brain has time to talk you out of it. Roll out of bed, three minutes on the floor, done. The hardest part is starting. After week two it becomes automatic.