The abdominal plank is a common exercise that is prescribed both in the gym and in the rehabilitation setting following injury. A correctly performed plank challenges the athlete to maintain a neutral lumbar spine position, good neck and thoracic posture, and stable shoulder control – it is not simply an abdominal and lumbar spine exercise. In fact, I would argue that if the lumbar spine is the main source of load and fatigue, then you are performing the plank incorrectly. Maintaining this position requires a combined effort of the posterior kinetic chain of the lower limbs, the muscles of the abdominal wall (as described in a previous blog post), the scapular stabilising muscles of the upper limb and thoracic spine, and the posterior muscles of the cervical spine.

What is the goal of the plank?

Due to the long lever that is created from the two points of contact and the effect of gravity on our centre of mass, the goal of the plank is to prevent extension of the lumbar spine and hip joints. This extension control exercise is made all the more challenging by the addition of the upper limb and thoracic control required.

What is the biggest mistake I see clinically in patients who perform the plank?

Anterior pelvic tilting and lumbar extension.

This may take the appearance of “sagging” in the middle, or alternatively increased hip flexion (bottom in the air).

plank_1

plank_3
Above: increased hip flexion

Adoption of this position is often the result of overactivity of the lumbar extensors, hip flexors, and weakness of the abdominal muscles anteriorly and hip extensors posteriorly. Commonly, these overactive muscles are the ones that are already strong and used for the individual’s postural control – this is how we see planks that are held for 2-3 minutes! Clinically, I find that correction of the pelvic position can significantly increase the difficulty of the exercise and have you working harder in a shorter amount of time!

Key points when performing a plank:

  1. Find a neutral lumbar and pelvic position – more often than not, this means that we will have to posteriorly rotate our pelvis. Engage the lower glute max and lower abdominals to tilt the pelvis, while maintaining your pelvic floor contraction.
  2.  Prevent sagging of the chest toward the floor by finding neutral shoulder position – this is a gentle push downward into the floor from the upper limbs.
  3.  Retract the head (creating a double chin) which lengthens the posterior aspect of the neck without letting the head drop toward the floor.

Remember, the plank is largely a lumbar extension control exercise. If you cannot perform the exercise correctly by shortening the lever (elbows and knees), then seek an alternative lumbar control exercise until your strength improves enough to allow performance of the plank. Your physiotherapist at Complete Sports Care can help tailor an appropriate strengthening program based on your current level.

Ref:

http://www.nhs.uk/Livewell/fitness/Pages/Top-10-gym-exercises-done-incorrectly.aspx

https://strongfastfitness.com/wp/2015/07/is-online-personal-training-a-good-idea/