primary muscle: core
supporting muscles: abs, low back, hips
The plank or front hold is the most important exercise for your core as it engages all of the core muscles to build both strength and stability through your whole body. Keeping a straight line between ankles, knees, hips and shoulders promotes the type of stable strength used through those joints, and more importantly, your torso, in everyday movements like sitting, standing, walking, etc. This exercise not only makes all of the muscles in your torso have to work to maintain the alignment (abs, low back, oblique, transvers abdominus), but also involves the shoulder and hip girdle to bare the weight, the other key body parts that make up the core. Adding instability underneath either arms or feet makes the respective muscles of the hip and shoulder girdle, as well as the muscles of the torso, have to work harder to share the load and balance in order to maintain body alignment. With the addition of instability the involved muscles are forced to share the load efficiently and have all muscles fire accordingly to do so, helping work on the 'weakest links in the chain' to promote better balance.
Plank on Elbows
The basic front hold, this variation is the easiest way to get the right angles and muscle engagement in holding the straight line between ankles, knees, hips and shoulders. Use this variation as a good starting point and way to build up more time for the exercise (muscle endurance) before adding more difficulty or instability in different areas of the core (torso, shoulder and hip girdle).
Plank on Hands
Moving up to the hands for this exercise, with straight arms, adds increased engagement and difficulty for the scapula (shoulder blades or girdle), the foundation for all of your arm strength and stability. This variation is more challenging for the upper body and adds more elbow and wrist stability to the exercise. For more difficulty and balanced core engagement, place your feet on a bench so that body is parellel to the ground.
Plank with Feet on Bosu
This variation introduces mild instability to the lower body, while still maintaining the correct body position, with hips in line with knees and shoulders. The instability from the round side of the bosu forces hips, knees and ankles to work more functionally to balance and stabilize in order to hold this body line, without having to also balance the body on the horizontal plane like more difficult variations (on the flat side for example). This makes this variation a good way to work stable core endurance strength (increasing time of the hold) while also increasing hip, knee and ankle stability.
Plank with Elbows on Ball
The exercise ball adds instability and balance to the front hold, forcing all of the muscles to work together not just to hold the body line position (shoulder, hips, knees and ankles), but also to hold the body horizontal to the ground throughout the hold. This means the chains of muscles are not only working from head to toe to keep the body in line, but also working across the midline to maintain balance. This variation puts a focus on the upper body stability by placing the ball under the elbows, meaning the scapula (shoulder blades) are working to stabilize arms, while the entire core works to maintain horizontal balance. This can be made more difficult by placing feet on a bench and getting body parellel to the ground.
Plank with Feet on Ball
This is the most difficult variation of the front hold variations that can be done without introducing one arm/leg variations, dynamicism and/or super instability (multiple balls/bosus). In this variation there is major instability for the lower body and in partiuclar the hip girdle as it works not only to keep hips straight with feet on the ball, but also to keep the whole body straight as the ball wants to roll. By being in a completely parellel to the ground position and on hands with straight arms to maintain it, the scapula (shoulder girdle) also has increased engagement. With both hip upper and lower body working harder to stabilize, and being higher up off the ground, it is more difficult to keep the hips up in line with knees and shoulders, as well as parallel to the ground.
These exercises come from our exercise library at Trainer+, a web and mobile platform for personal trainers.
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