How many reps or how long should a beginner do plank jacks for?

Start with 2 to 3 rounds of 20 to 30 seconds, or about 15 to 20 total jumps, resting a full minute between rounds. Once the hips stay level and the landings stay quiet for the whole round, add 10 seconds at a time before you add a third round.

How do I make plank jacks easier or harder?

To make them easier, step the feet out and in one at a time instead of jumping, or do them from a high plank with the hands raised on a bench or step. To make them harder, put a slider or towel under each foot and slide the feet out and in under control, or wear ankle weights to load the hip movement.

What do plank jacks train, and when should I skip them?

They combine core anti-extension work with a light cardio bump, which makes them a good circuit or finisher move for conditioning rather than a pure strength builder. Skip them, or step instead of jump, if you have wrist pain in a high plank or if impact bothers your lower back, since the repeated landings add a jarring element a static plank doesn't have.

Beginner

Plank Jack

Think of it as a jumping jack for the bottom half while the core refuses to move. Each foot jump adds a small anti-extension and anti-rotation challenge, and the continuous rhythm bumps the heart rate, making it a great finisher or circuit station. It builds plank endurance while sneaking in some conditioning.

Equipment: Body Weight
Body part: Abs
Type: Cardio, Functional
Browse by muscle: Upper Rectus Abdominals, Lower Rectus Abdominals, Abdominal External Oblique
Browse by movement: Core Brace

How to do it

1
Start in a forearm or high plank with a braced trunk and a straight body line.
2
Keep the hips level and the abs tight throughout; the upper body should not bounce.
3
Jump both feet out wide, landing softly on the balls of your feet.
4
Immediately jump them back together under your hips.
5
Continue at a steady pace for the prescribed time or reps, breathing rhythmically.

Tips

Do not let the hips pike up or sag as the feet travel; the belt line stays flat.
Land light and quiet to protect the lower back from jarring.
Slow the tempo or step the feet instead of jumping if the hips start rocking.
Keep the shoulders stacked over the elbows or hands the whole set.

Variations

Common mistakes

The head drops to watch the feet jump, rounding the upper back and taking tension off the abs.
The breath gets held for the whole set instead of matching the jump rhythm, which makes the last few reps feel far harder than they should.
Racing the pace faster than the hips can control turns the last several jumps into a sloppy stumble instead of a clean plank.
The feet jump different widths from rep to rep instead of a consistent hop, making the set uneven rather than a steady rhythm.
Counting reps out loud or rushing to finish a time cap encourages shrinking the range of the foot jump to move faster.

Frequently asked

How many reps or how long should a beginner do plank jacks for?: Start with 2 to 3 rounds of 20 to 30 seconds, or about 15 to 20 total jumps, resting a full minute between rounds. Once the hips stay level and the landings stay quiet for the whole round, add 10 seconds at a time before you add a third round.
How do I make plank jacks easier or harder?: To make them easier, step the feet out and in one at a time instead of jumping, or do them from a high plank with the hands raised on a bench or step. To make them harder, put a slider or towel under each foot and slide the feet out and in under control, or wear ankle weights to load the hip movement.
What do plank jacks train, and when should I skip them?: They combine core anti-extension work with a light cardio bump, which makes them a good circuit or finisher move for conditioning rather than a pure strength builder. Skip them, or step instead of jump, if you have wrist pain in a high plank or if impact bothers your lower back, since the repeated landings add a jarring element a static plank doesn't have.

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