Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Frye’s Body Mechanics for...

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins

Frye’s Body Mechanics for Frye’s Body Mechanics for Manual TherapistsManual Therapists

Frye’s Body Mechanics for Frye’s Body Mechanics for Manual TherapistsManual Therapists

Chapter Six – Sitting


Principle OnePrinciple One

Sitting on the ischial tuberosities distributes the

body’s weight optimally throughout the pelvic region.


Aligning Your Pelvis, Legs, and Feet in a Sitting PositionAligning Your Pelvis, Legs, and Feet in a Sitting Position

• Poor sitting posture contributes to low back pain.

– Places stress on the lumbar spine, especially when sitting without back or arm supports

• Leads to a posteriorly tilted pelvis

• Decreases the lumbar curve


Impractical for Manual Therapists to Use Chairs with Back and Arm RestsImpractical for Manual Therapists to Use Chairs with Back and Arm Rests

• Must find other methods to reduce low back pain when working from a seated position


Using the Pelvis, Legs, And Feet for support and balanceUsing the Pelvis, Legs, And Feet for support and balance

• Skeletal structure of pelvis can be compared to a bowl

Figure 6.1 Pelvic bowl. This illustration compares the shape of the pelvis to a bowl.


Majority of Torso’s Weight Rests on the Ischial Tuberosities (“sit bones”) at Its Base When Sitting

Majority of Torso’s Weight Rests on the Ischial Tuberosities (“sit bones”) at Its Base When Sitting

• Ischial tuberosities are the proper points of contact, not the coccyx (tail bone).

– Coccyx is part of the spine; no weight should be placed on it.

Figure 6.2 Areas of weight bearing in proper sitting posture. The ischial tuberosities (blue), rather than the coccyx (purple), are the skeletal structures bearing the body’s weight in healthful sitting. In addition, body weight is distributed over the muscles and other soft tissues of the pelvic region (red). Notice as well the full contact of the feet in healthful sitting (green).


When properly sitting with pelvis in a neutral position…When properly sitting with pelvis in a neutral position…

• Body’s weight rests optimally on the flatter aspects of the tuberosities

• Pelvis is rolled neither backward nor forward


Weight Must Be Distributed Equally on Both TuberositiesWeight Must Be Distributed Equally on Both Tuberosities

• Provides optimal balance and stability

• Allows you to sit in a self-supported posture for longer periods of time

• Unequal distribution can cause an imbalance in the pelvis and amplify muscular holding and tension.


Along with the ischial tuberosities…Along with the ischial tuberosities…

• the muscles and soft tissues of the lower body also help bear body’s weight.

• Includes muscles of the posterior upper leg and buttocks as well as the muscles and soft tissues of the perineal area between the pubic symphysis and coccyx

Figure 6.2 Areas of weight bearing in proper sitting posture. The ischial tuberosities (blue), rather than the coccyx (purple), are the skeletal structures bearing the body’s weight in healthful sitting. In addition, body weight is distributed over the muscles and other soft tissues of the pelvic region (red). Notice as well the full contact of the feet in healthful sitting (green).


Principle TwoPrinciple Two

Sitting with the feet underneath the knees

increases stability, balance, and comfort.



• As in standing, it is important to contact the ground with your whole foot when sitting and keep your feet directly under your knees.

– Reduces muscular effort in the lower legs

– Gives body a solid connection to the ground

Figure 6.2 Areas of weight-bearing in proper sitting posture. The ischial tuberosities (blue), rather than the coccyx (purple), are the skeletal structures bearing the body’s weight in healthful sitting. In addition, body weight is distributed over the muscles and other soft tissues of the pelvic region (red). Notice as well the full contact of the feet in healthful sitting (green).


Placing both feet under you…Placing both feet under you…

• greatly increases your skeletal support and allows you to work comfortably in a sitting position.

• Other sitting positions that may appear comfortable can ultimately lead to low back stress and muscular fatigue.


Principle ThreePrinciple Three

Placing the knees at or slightly below hip height allows the best contact between the chair and

ischial bones.



• Position of pelvis influenced by height of the knees

– When knees are higher than the hips, pelvis naturally tilts backward; best contact point to the ischial bones is compromised.

• Forces body into a “slouched” position

Figure 6.3 Improper knee positions during sitting. A. Sitting with the knees too high promotes a slouched position.


When knees are more than slightly lower than the hips…When knees are more than slightly lower than the hips…

• pelvis automatically rolls forward; contact to ischial bones is compromised.

• Lumbar spine is forced into a bowed position.

Figure 6.3 Improper knee positions during sitting. B. Sitting with the knees too low promotes hyperextension of the spine.


If you are fairly flexible in your low back…If you are fairly flexible in your low back…• then sitting with the knees at the

same height will be comfortable.

• If not, then sitting with the knees slightly lower will help increase the curve in your low back, tilting your pelvis into the best position.

– Try both options and find what’s most comfortable for you.

Figure 6.4 Proper knee position. Here, the therapist is sitting with his knees at the proper height, in line with his pelvis.


Principle FourPrinciple Four

Abducting the legs wide apart allows for bending forward from

the hip joints.



• Bending forward while sitting should originate from the hips, not the spine.

• How wide you position your legs will determine how far you can bend forward at your hip joints.


Abduct legs wide enough…Abduct legs wide enough…

• so that you have enough space to bend forward from your hip joints and at the same time keep your spine in a comfortable and neutral position.

• Discomfort in the low back may indicate hyperextension from spreading legs too wide.

• Always maintain clear contact between sitting surface and ischial tuberosities.

Figure 6.5 Leg width. A. Sitting with the legs apart allows you to bend forward from your hip joints.


Holding legs too close together…Holding legs too close together…

• causes pelvis to tilt backward, creating muscular tension in hips and low back.

• This muscular holding decreases flexibility in hip joints and forces you to bend forward from your spine.

• This kind of bending causes fatigue and great discomfort.

Figure 6.5 Leg width. B. Sitting with the legs too close together forces you to bend from your spine.


Specific ApplicationSpecific Application

• Sitting with proper leg height and width allows a reflexologist to bend forward from the hip joints, keeping her low back stress free.

– Notice her balanced head position.

Figure 6.6 Specific application: Reflexology massage. Proper leg height and width allow this reflexologist to bend forward from her hip joints.


Function of the Pelvis and the Ischial BonesFunction of the Pelvis and the Ischial Bones

Figure 6.7 Pelvis as rocking chair.

Figure 6.10 Sitting on the ischial bones.


Flexing and Hyperextending the Upper BodyFlexing and Hyperextending the Upper Body

Figure 6.9 Hyperextending the upper body.

Figure 6.8 Flexing the upper body.


Principle FivePrinciple Five

Balancing the head over the spine promotes neutral alignment of the thoracic

cage, unrestricted breathing, and effective

use of the arms.


Balancing Your Head in a Sitting PositionBalancing Your Head in a Sitting Position

• Working with raised arms and, at the same time, remaining comfortable in your upper body can be challenging.

– Combined weight of the arms and head is 20% of the body’s total weight.

– Head’s center of gravity sits forward of the spine.


Properly balancing the head over the spine…Properly balancing the head over the spine…

• reduces workload of neck muscles, especially the extensor musculature in posterior neck.

• Helps reduce tension, fatigue, and pain in the low back, neck, and shoulders caused by long periods of sitting


Relationship between rib cage and thoracic spine…Relationship between rib cage and thoracic spine…

• influences not only the alignment of your head, but also your breathing and the way you raise your arms.

• Thoracic spine stabilizes the rib cage, allowing flexibility during movement, especially breathing.

– Each vertebra of the thoracic spine connects with a corresponding rib.


When thoracic spine is in a neutral position…When thoracic spine is in a neutral position…

• the rib cage is also in a more neutral position.

– Ribs remain up, rather than collapsed

– Easier to maintain a properly balanced head, raise your arms, and breathe freely and deeply

Figure 6.11 Rib cage and spine position. A. Sitting with the thoracic spine in a neutral position supports the rib cage to assume a neutral position. Breathing and movement are unrestricted.


When thoracic spine is flexed forward…When thoracic spine is flexed forward…

• the rib cage is collapsed and head has the tendency to fall forward, out of proper alignment.

• Breathing becomes restricted, and entire torso becomes seemingly heavy.

• Raising the arms to work now puts a tremendous strain on the upper body, especially the shoulders and neck.

Figure 6.11 Rib cage and spine position. B. Sitting with the thoracic spine flexed forward and the rib cage collapsed restricts both breathing and movement.


Troubleshooting Sitting DiscomfortTroubleshooting Sitting Discomfort

• Using a step or block under one foot can help relieve back tension.

– Step should be no higher than a few inches.

– The idea here is to relieve any pulling that might be caused from a normal sitting position.

– To prevent possible muscular imbalance, be sure to change from one side to the other periodically and use the step for short periods of time.



• Sitting on a wedge cushion, with the widest part under your sacrum, can help relieve low back tension by bringing the lumbar spine into a neutral position.

– Some wedge cushions have a removable coccyx pad for those with tender tailbones.



• Sitting as close as possible to your table will reduce the stress to your back.

– Access panels make sitting close easy.

– Set the height of your table so that your client’s body is at the same height as your hands.

– A table set too high can cause shoulder tension, exacerbating back pain.


Anterior Head PositionAnterior Head Position

Figure 6.12 Anterior head position.

Figure 6.13 Anterior head position with raised arms.


Posterior Head PositionPosterior Head Position

Figure 6.14 Posterior head position.

Figure 6.15 Posterior head position with raised arms.


Balanced Head PositionBalanced Head Position

Figure 6.16 Balanced head position.

Figure 6.17 Balanced head position with raised arms.

Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Frye’s Body Mechanics for...

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Transcript of Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins Frye’s Body Mechanics for...