Your body is a dumbbell: Anti-Rotational Plank
Considering the timing of this post, it seems appropriate to give it a Star Wars theme…
The role of the core is to produce force, transfer force, and mitigate force. As the core region is situated between the limbs of the upper and lower body, it rarely produces force. Much of the time, the core is transferring force from/to the limbs or mitigating force from the limbs. For the purpose of this discussion, let’s focus on the two primary roles during sport: force transfer and mitigation.
Your body pushes, pulls, rotates, and bends. There are three dimensions of movement that the body moves through to manipulate the environment when grasping, reaching, throwing, walking, kicking, etc. The movements that dominate the throwing and kicking sports are pushing, pulling, and rotating.
A throw begins at the foot as a pushing force is exerted to the ground (ground contact force). The proximal joints (closer to the core), coalesce behind the initial force of the foot in various ways depending on the ultimate throwing target’s position. The stiffness that is created joint by joint allows for the most optimal transfer of force or lowest potential loss of force transfer. Consider using a pool noodle for a light saber duel vs. a light saber (my children own both). The impact of a pool noodle will never hurt anybody regardless of Jedi Knight training (but will likely irritate them), whereas a [plastic] light saber will make an impact that annoying sibling even with Padawan capacity. Despite the hardness factor, the pool noodle does not maintain stiffness for the end to move through space as quickly as intended—it bends.
Why should our body be any different? Sure we need to fine tune our motions for intended targets. But if we are optimally positioned, the force transfer will be the greatest. When appropriately aligned, the stiffness of our joints transfer the greatest force and lose the least force capacity.
Now let’s examine the task of an anti-rotational plank. There is pushing through opposing extremities (right arm, left leg), pulling through opposing extremities (left arm, right leg), and a potential to rotate the trunk. The rotation potential is the key ingredient for the anti-rotational plank. The role of the core in this case is transfer and mitigation. The body does not produce force, it is force (mass times acceleration). Considering the foot print of the legs and arms, we can increase or lower the rotation potential. Note the position in the video—wide base for legs and narrow for arms. The wider base that is established for a bilateral activity, the more stable that body will be. However, the wider base that is established for a unilateral activity, the less stable that body will be. Try this out. Stand up with feet narrow and proceed to a single limb stance with pelvis and shoulders level. Now stand with feet wide apart and proceed to a single limb stance with pelvis and shoulders level. Aha! There is a greater moment arm or more mass is placed outside the balance point, requiring the body to work much harder to maintain a level position.
Now move to the plank position and repeat. This is the nature of an anti-rotational plank. To progress force, add load such as the dumbbell in the video. Or move the unilateral base to a wider position such as the Halo Trainer anti-rotational plank displays.