Biomechanics Blog Post #5: Posture and Body Mechanics

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The above photograph is my mother sitting in her chair, working tirelessly in her Office Manager class. Geaux Mom! 

The position she is in is referred to as Middle Sitting, which is also a static posture. There is no rotation regarding her hips, but she is anteriorly tilting her pelvis into the purple cushion. Both of her femurs are flexed at the hip close to 90°. Due to her posture, she has multiple spinal curves that consist of the following: slight lumbar lordosis, excessive thoracic kyphosis, and a forward head posture (cervical flexion). Lastly, her scapulas are in protraction with slight depression.

This position is efficient in stability, but not for mobility. It is not efficient for mobility, since it is a harder to get out of this position. This difficulty is due to her transmitting 25% of her body weight through her feet, and she has 3/4 thigh support. She has a large base of support (BOS) since her feet are flat on the floor, her elbow is resting on the chair arm, and the chair itself is supporting her weight as well. Her upper extremities (UE) are fairly free for movement. In this specific case, she is keeping her left elbow and forearm to keep her writing board stationary, and her right elbow is flexed, so she can use her right hand to write. The left elbow is the only portion of her UE that is being used for support, since she has it rested on the arm chair. This posture does not ideally support joint alignment. It adds gravity as an additional force on her cervical and thoracic spine. Excessive forward cervical flexion can double the weight of the head, and lead to joint or muscle issues in the future. Excessive thoracic kyphosis can naturally create a 'hunchback' and impair respiration.

Sitting duration is dependent on the individual; however, I know for a fact she can sit in this position for at least an hour. Due to the severity of her cervical and thoracic spine in flexion, I would suggest re-adjusting her position every 15 minutes. If she prefers to stay in this position, then every now and then she needs to stand up and fully extend her spine to relieve some pressure. Therefore, I suggest re-adjusting her sitting position and include slight stretching every 15 minutes.

There are multiple reasons to correct this posture, because it can drastically influence her pain management for the future. Her thoracic spine is in a kyphotic curvature, which if stayed flexed in that position for a certain amount of times and duration, it can cause multiple issues. The thoracic kyphotic curvature can add pressure to the lungs and create respiration issues, and it can potentially tear the Posterior Longitudinal ligament due to hyper-flexion. The hunchback posture can lead to a weaken core by forcing the back muscles to overcompensate. This overcompensation of back muscles can cause lower back pain.

Teaching proper body posture and body mechanics can truly be life saving. Changing one's posture and mechanics can save an individual money and pain in the future. The occupational therapist would intervene by educating this client on proper body posture while sitting. Proper body posture while sitting can prevent the client from developing herniated discs, it can decrease muscular pain in the back by activating core muscles, and it can prevent unnatural bone adaptations due to Wolf's Law. 

There are many interventions an occupational therapist (OT) can use to teach proper body posture and body mechanics. In this specific example, the OT would find the correct sitting posture by using the slouch-overcorrect technique. This can be used to figure out the 'just right' position for the specific client. Some posture cues would be to activate the core muscles to help extend the spine in an erect position, keep the head in line with the shoulders (ear lobe in line with acromion),  and to get out of the seated position in multiple intervals. Some adaptive techniques the OT could consider would to add more pillows behind her back for better support and using an elevated writing board to decrease cervical and thoracic flexion.