Muscles worked
The inchworm is a mobility drill and a core exercise in one. On the way down, your hamstrings and calves get a stretch. As your hands walk out, your shoulders, chest and triceps carry more of your body, and in the plank your abs work to stop your lower back from arching. The further forward your hands go, the longer the lever and the harder it gets for both your trunk and your shoulders. It is a common warm-up move, as it wakes up your shoulders, trunk and hamstrings at once.
Common mistakes
- Locking your knees to reach the floor. Rounding hard with straight legs turns the stretch into a pull on your back. Bend your knees as much as you need, and straighten them a little more over time.
- Taking long steps with your hands. Your hips then rock from side to side. Take short steps and keep your hips still, as if balancing a glass on your back.
- Walking out further than you can handle. A long plank, hands far ahead of your shoulders, is much harder than a standard one. Stop with your hands under your shoulders until you can hold the line there.
Variations and alternatives
- The plank holds the middle position still, when you want to train your trunk for time.
- The bear crawl has you crawl on hands and feet, keeping your shoulders and trunk working without a break.
- The ab wheel rollout does the same job against arching with far more load, once the long plank starts to feel easy.
Sets and reps
Before a session, 1 to 2 sets of 5 to 8 slow reps are enough as part of your warm-up. As a core exercise, you can do 2 to 3 sets of 6 to 10 reps with a two-second pause in the plank. See the guide to sets and reps for more on structure.
Make it harder by walking your hands further out, holding the plank longer or adding a push-up before you walk back. That is progressive overload in an exercise mostly used to warm up. If your back or shoulders hurt, stop the exercise and have it looked at by a doctor or physiotherapist.