All the Muscles That Fire Up In a Plank

Whether you’re embarking on your first weight-training plan or prepping for an Olympic weightlifting competition, there’s a good chance that planks will be a part of your strength program.

And for good reason. Planks fire up a wide swath of muscles at once — and can be executed wherever there’s space large enough to fit a body’s length on the floor, according to Chris Travis, a NASM-certified trainer. “Every client [I train] will have some form of a plank as part of their programming,” he said.

Another major reason for their effectiveness? Planks are an isometric exercise, which means that the muscle does not lengthen or shorten throughout the movement. In the case of a plank, the muscles create tension by resisting gravity, Travis explained. This can be hugely beneficial for folks who are sedentary throughout much of the day, he said.

“I find that a good amount of [my clients] and the general population sit for long periods of the day and develop some [anterior] tilting in their pelvis, which can lead to pain and tightness [in the hip flexors],” he said. “Training the core, particularly through the proper mechanics of a front plank, can significantly help [put the pelvis in a neutral position].”

Whether you’re active throughout the day or sit for prolonged periods, planking can be an effective way to train your core. That said, it’s always best to consult with a certified trainer, doctor, or physical therapist to determine if it’s a safe move for you to execute.

Read on to learn what muscles are worked in a plank, the benefits of planks, and how to do them effectively.

Travis said he prefers starting clients with a forearm plank versus a straight-arm plank, since a forearm plank often allows people to better hold tension throughout the body. A straight-arm plank, while still firing up the abdominal, back and posterior leg muscles, places more stress on the hands and wrists. For folks with existing pain or limited mobility in these areas, this can make a straight-arm plank more difficult.

When executing a forearm plank, four major muscle groups are activated:

Planks are a fairly straightforward, no-frills exercise. And while they can progress in terms of difficulty and muscles activated with a multitude of variations, mastering the forearm plank can help build a foundation for experimenting with new forms, Travis said.

1. Start on all fours. Hinge forward to lay forearms flat with the palms facing downward on the floor. Elbows should be directly under shoulders and planted onto the floor.
2. Step the feet back until the legs are fully extended. Bring the feet together, toes pointed toward the floor.
3. Using the midsection as momentum, keep forearms and elbows planted into the ground while lifting the torso, stomach and legs off of the floor. Keep the head in line with the spine and hips while squeezing the glutes, hamstrings, and quadriceps and pushing the heels toward the back of the room. Gaze gently ahead toward the fingertips.
4. Resisting any movement, hold position for desired timeframe, depending on comfort and strength level. Release, bringing the torso, stomach and legs back gently down to the floor.

Repeat 2 to 4 times.

If you’re concerned that an extra-long plank might be too challenging, and if you’re engaging all of those muscles listed above, a 20- to 30-second (or even 10- to 15-second) hold, repeated two to four times, should suffice, Travis said.

“If you’re holding a plank with sufficient tension, even a short hold should feel challenging,” he said. “I’ve seen this with clients and athletes across the board.”

Travis said that 45 seconds (or until your form falters) is generally a good baseline for holding a plank.

Words by Julia Sullivan, ACE C.P.T.