The Thorax: the Forgotten Link in Human Motion

SKELETAL AWARENESS & DEXTERITY THE THORAX: THE FORGOTTEN LINK IN HUMAN MOTION

Robert Burgess BEd, PT, PhD, Feldenkrais Practitioner Newsletter September 2007 The Feldenkrais Method: Better Body-Better Mind An immovable cage or a mobile spring? 250 300 The thorax or rib cage is cast as a rigid structure with only minimal thorax thorax movement for breathing and otherwise a immobile cage flexion protecting the heart and lungs. This is a popular myth and an extension unfortunate fallacy. Lets examine some of the evidence:

Range of motion To twist around to look over the shoulder to look directly behind, the thorax rotates 50 degrees (Buchalter et al 1988; Willems et al 1996). To bend to the side the thorax bends 26 degrees or at least 70% of the lumbar spine. In sitting, the thorax flexes 30 degrees and extends 25 degrees. Rigid? no way. Instead, in fact, with each pair of ribs moving on the next- 500 260 thorax ‘the thorax behaves like a hooped spring’. thorax rotation side bend Human gait: the reptile persists When an a young adolescent (11 year old) walks and swings the left leg forward there is 20 degrees of side bend or lengthening of picasso the left side, ten degrees of which occurs in the thorax and ten in the lumbar region (Chan et al 2006). In adults thorax side bend is 5 degrees (Stokes et al 1989). The pelvis and thorax rotate in opposing directions and together with side bending are the prime movers of human locomotion (Gracovetsky 1997). Lengthening The Thorax of the sides contributes to stride length (Inman et al 1980). Side is a bend in walking is an important evolutionary remnant from the first ‘Spring’ fish and reptilian locomotion. Without it there is more demand on not a Cage hip flexion and heel strike will be altered.

human walking

trunk side bend trunk counter rotation Increased kyphosis: the decline Rounding of the upper and middle back is called

0 kyphosis- there is a normal amount, about 30 degrees. adolescent thorax 10 Increased kyphosis in women aged 70-93 years is adult thorax 50 thorax = -50 associated with greater back and neck pain, greater

0 emotional depression and greater loss of motor lumbar spine = 10 0 lumbar = 8 function (balance and strength) compared to matched pelvis = 8-110 mildly kyphotic subjects (Balzini et al 2003). pelvis = 8-110 There is a greater risk of vertebral fracture in the elderly with increased kyphosis. This is independent of age or previous fracture (Huang et al 2006).

With elevation of the arm, there is an amount of thorax motion (4- 0 The aging thorax 5 ) (Theodoridis & Ruston 2007). Increased rounding of the With age thorax kyphosis increases (Bartynski et al thorax affects shoulder and scapular mechanics which 2005). theoretically at least contributes to increased strain in the 18-35 36-50 51-65 65+ shoulder (Kebaetse et al 1999; Finley & Lee 2003). kyphosis 280 300 360 420 OWD normal thorax kyphotic thorax elevation includes upper back elevation includes reduced range extension, rotation and side bend of motion, decreased strength & increased scapula elevation

Ten cadavers, aged 55-91 measured for range of motion, showed wide variability- extension-flexion combined = 2- 150, rotation = 6-510 & side bend = 2-260 (Watkins et al 2005).

The Bad News: A study of 1353 subjects (Mean age 70 years) over a 3 years period, there was a 1.4 times risk Briggs et al 2007 in a biomechanical analysis recently reported of death in people with increased kyphosis compared to that increased thoracic kyphosis caused increased stresses on same age without significant kyphosis of the thorax the low back and may be a factor in low back pain and lumbar (Kado et al 2004). disc degeneration. The Good News: Will an aging thorax necessarily become significantly kyphotic and contribute to the many normal mobile thorax a rigid cage thorax negative features of this spinal deterioration? In Di Bari’s even spread of spinal loads excessive lumbar loads (Di Bari et al 2006) 323 home dwelling population aged 65 and over 193 (60%) were non-kyphotic.

Anecdotal note- A female patient in her mid fifties presented for hip pain. She was a keen skier and looked athletic. Her spine was straight but seemed rigidly so. When this straightness and rigidity were mentioned to her, she said:

“Well, in my twenties, I took one look at my mother and grand mother and I said ‘No Way’!”.

‘No way’ to the advancing kyphosis of both her mother and grandmother. She had beaten the family trend of a Respiration kyphotic spine by her deliberate physical actions. Di Bari et al (2004) studied a home dwelling population aged 65 Kyphosis is not for everyone. years and older. 40% had increased kyphosis (occiput to wall distance-OWD) which increased with age to 80% for those 85 and older. 56% of those with increased kyphosis had normal Significantly increased thorax kyphosis with its many spirometry compared to 77% of the non-kyphotic group. perils may not be a necessary feature of aging, nor a genetic inevitability, but rather, it may involve reversible 50% of the kyphotic group had obstructive and restrictive lifestyle habits. ventilatory patterns compared to 20% for the non-kyphotic group. Those with significant kyphosis had twice the risk of dyspnea than the non-kyphotic. Osteoporosis The more severe the kyphosis the more likely is a loss of It seems logical enough, rigid thorax, diminished breath and it is bone density (Ettinger et al 1994; Ostrowska et al 2006). very well known what happens to persons with severe spinal Strengthening exercises are proposed to prevent spinal deformities and ventilation however thorax mobility is poorly deformity (Mika et al 2005). Mobility and spinal investigated in respiratory dysfunction. awareness exercises coupled with weight bearing is thought to enhance the effect of strengthening alone (Alon 2007).

Throwing In baseball pitching it has been estimated that 50% of ball speed originates from the action of the arm to the shoulder and 50% occurs from the action of the body. One model of interest for throwing is that of a whip action. The hand and wrist are the tip or ‘crack’ end of the whip, the shoulder is mid whip and the lumbar spine and pelvis are the stock end of the whip. The thorax is a mobile link between the arm and the lumbar spine and pelvis. This is where the spring model for thorax function matches the whip action of the arm and trunk. Not to forget, the action of the legs further contributes to the throwing action and ball speed.

This model of throwing provides a method for both a regional and global evaluation of throwing movement parameters. Throwing with just the shoulder is known to contribute to shoulder injuries in tennis and baseball. “Put your back into it” might be a valid motto for shoulder injuries. Physical therapy is just beginning to investigate thorax motion in shoulder function.

lifting a box from a bench to shelf Lifting thorax 110 T In one biomechanical study, lifting a 5kg box from a bench to shelf involved equal amounts of thorax and lumbar bending (Burgess 2002). Bench to shelf was used to replicate a regular lumbar 50L lifting task at the workplace and at home. Ten degrees of P lumbar spine and pelvic flexion was accompanied by ten pelvis 40 degrees of thorax flexion to put the box down onto the bench and similarly for extension to pick the box up.

Reaching & Balance Reaching is a major human function. We reach for a coffee cup, alarm clock, a hand shake and we reach out for help. Standing reach is used as one test for balance. With age and loss of balance the distance for standing reach is diminished. Cavanagh et al (1999) investigated trunk segment mobility during a standard reach test. The thorax, lumbar spine and pelvis- leg rotation all contributed to reach, however, only thorax rotation** was significantly reduced in the elderly. A mobile thorax allows for a combined excursion of the upper and lower body and legs to perform the task. A rigid thorax demands more of the legs and lower body and puts the person at risk of loss of balance.

thorax rotation** young: 100 elderly: 70

lumbar rotation young: 70 elderly: 70 Reaching while lying on the side is a convenient pelvis & leg rotation way to eyeball trunk segment motion. young: 110 elderly: 120

Medicine is Regional, Structually, isolated unrelated parts with pathology, Human function, however, is the thorax appears to be a cage, global skeletal linked body segments- a kinematic chain from foot to head. Functionally, it behaves as a spring

Why is the Thorax not a Hot Topic in Medicine? Seems that it should be! The title rib cage immediately suggests a rigid structure. Cages don’t move.....but springs do. Secondly, it already has two major acknowledged functions, breathing and protection. A role in protection of the heart and lungs again invites the image of an immovable structure and denies the third valid function of mobility.

We are yet to fully appreciate that the human skeleton is a global linked mechanical system- a kinematic chain- with coordinated function of body segments in a gravitational field. The old song: “the hip bone is connected to the back bone.....” implies connection and relatedness which is absolutely true.

The thorax is a direct link between the neck and lumbar spine and pelvis. The whole spine functions as a unit such that the head rests upon and moves with 24 vertebrae- neck-thorax-lumbar spine-pelvis. Not to forget the legs beneath.

Thorax rigidity is implicated in low back pain and lumbar degeneration, neck pain, shoulder pain, respiratory dysfunction, osteoporosis, balance and strength and even mortality. Not something to be ignored.

The thorax is complex with many small movements contributing to a flexible structure with three major roles- breath, protection and mobility. It deserves greater attention and recognition.

‘Thorassic-Park’

The turtle’s shell: bony plates fused with a rib cage bugs can’t roll!

Boa snake has 300 ribs & can he move turtle shell back thoracic spring bugs have a fixed =rigid kyphosis = flexibility one piece thorax

The turtle’s shell is a bony rib cage altered during development. Large bony plates envelope and absorb the ribs and then fuse together to make the shell. The vertebrae of the thorax are fused to the under surface of the shell, a mere vestige of its former function. The shoulders and pelvis are too welded to the shell. Only the neck, tail and limbs can move. Bugs have a one piece thorax and hence no movement creating the characteristic difficulty when laid on their back- bugs can’t roll. The Boa constrictor and snakes are all rib cage,! Snakes have up to 150 vertebrae from head to tail with a pair of ribs attached, yet we know these animals to be powerful and flexible and definitely not rigid. The human thorax is NOT rigid unless you make it so.

References: Bottom line Next Issue: www.efeld.com Exercise your thorax. Exercising the thorax.

Research A study or series of studies investigating the role of the thorax in basic human functions (reaching, throwing, sit to stand, walking, bending, twisting and more) across ages (adolescents, adult, elderly) and conditions (low back pain, rotator cuff tears, knee pain) would provide a data base and insight into the role of the thorax in human movement. The thorax deserves investigation in a number of domains.

References:

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