Medicine Ball Plank Jack
What Is the Medicine Ball Plank Jack?
Medicine Ball Plank Jack is a compound exercise that primarily targets the core and also engages the shoulders, chest, and hips. It is an intermediate-level movement performed in a high plank with both hands stacked on top of a medicine ball while the feet jump out wide and back together.
The ball is what raises the difficulty. Placing both hands on a single rounded surface narrows the base of support and forces the shoulders, serratus, and trunk to work continuously just to keep the torso from tipping. Adding the jack means the hips must resist rotation and sagging while the legs move, so the abdominals never get a chance to switch off between reps.
The rectus abdominis and obliques hold the spine still against the pull of the moving legs, the glutes keep the pelvis level as the feet travel out and back, and the shoulders and chest carry the upper-body load on an unstable point. Because the legs create a small amount of impact each rep, this also nudges the heart rate up, which is why it appears in conditioning circuits as often as it does in core work.
If holding the ball feels unstable at first, build up with a standard Plank or Exercise Ball Plank to get used to an unsteady base, then add the jacks. For more challenge, slow the return so the legs come together under control, or move to a Mountain Climber or Up-Down Plank for a different demand on the same positions.
This suits lifters who want a core drill with a conditioning element, athletes training anti-rotation strength, and anyone who has outgrown static planks. The intent should be to keep the hips as quiet as possible while the feet move, not to jump as fast as you can.
Muscles Worked
- Rectus Abdominis
- Primary
- External Oblique
- High
- Deltoid
- Medium
- Gluteus Medius
- Medium
- Serratus Anterior
- Medium
Instructions
- Place a medicine ball on the floor and set both hands on top of it, one beside the other.
- Walk your feet back into a high plank with your arms straight and your shoulders stacked over the ball.
- Set your body in a straight line from head to heels, ribs down and glutes squeezed.
- Brace your abdominals and press firmly into the ball to keep your shoulder blades stable.
- Jump both feet out wide, landing softly on the balls of your feet.
- Jump both feet back together, keeping your hips level throughout.
- Keep your head in line with your spine and avoid letting your hips pike or sag.
- Continue for the prescribed number of reps, then step your hands off the ball to finish.
Common Mistakes
Hips sagging toward the floor
Letting the pelvis drop shifts the load off the abdominals and compresses the lower back.
Piking the hips upward
Lifting the hips high makes the jacks easier but removes most of the anti-extension work the drill is meant to train.
Bouncing the feet too fast
Rushing the jumps causes the hips to rock side to side and turns a core exercise into uncontrolled hopping.
Shoulders drifting behind the hands
If the shoulders are not stacked over the ball, the arms carry the load at a poor angle and the ball is more likely to roll.
Using a ball that rolls
A slick or overinflated ball on a hard floor can slide out from under the hands and drop you onto your chest.
Holding the breath
Bracing without breathing raises blood pressure and shortens the set well before the core is actually fatigued.
Injuries
Medicine Ball Plank Jack is a medium risk exercise when performed with proper technique. The unstable hand position and the repeated foot impact make it more demanding on the wrists, shoulders, and lower back than a standard plank.
The lower back is the first area to complain, usually because the hips drop as fatigue sets in and the lumbar spine takes over the job of holding the body up. The wrists are next, since resting weight on a curved ball puts them in a compressed position, and a ball that rolls unexpectedly can load a shoulder at an awkward angle. Choose a ball that will not roll on your surface, keep the reps well short of failure, and stop the moment the hips start sagging.
If the wrists hurt, place your forearms or hands on the floor and perform regular plank jacks, or regress further to a Plank hold until you can keep a rigid line for 30 to 45 seconds. To progress, slow each rep down, pause briefly with the feet wide, or add reps rather than speed.
Stop the set if you feel your lower back arching, sharp wrist pain, or any shoulder pinching. This is a quality-over-quantity drill, and there is no benefit to grinding out extra reps in a broken position.
- Primary Focus
- Core
- Equipment
- Medicine ball
- Modality
- Cardio
- Difficulty
- Intermediate
Alternative Exercises
Frequently Asked Questions
- Q: What size medicine ball works best?
A firm ball around 8 to 12 inches across is easiest to control, since both hands need to sit on top comfortably. Avoid soft or slick balls that flatten or slide under pressure.
- Q: Should I count each jack as one rep?
Yes. One rep is feet out and back together. Sets of 10 to 20 reps are typical, done with control rather than for speed.
- Q: Is this a core exercise or a cardio exercise?
It is primarily a core exercise, though the repeated jumping does raise the heart rate. If you want a conditioning effect, use it inside a circuit rather than lengthening individual sets.
- Q: What can I do if my wrists hurt on the ball?
- Q: How do I make it harder without adding reps?
Slow the tempo, pause for a second with the feet wide, or elevate the feet slightly to shift more weight onto the ball.