Rebuttal - Learn About the Leg Press

[Guest guest]

In response to Dr. Siff's comments concerning this article, I would first

like to thank him for his input. His time is appreciated. The Health and

Fitness Industry desperately needs checks and balances. It must also be

stated that just as the reader needs to be aware of " misinformation " , they

must also realize that any information can be scrutinized especially when

taken out of context. With full respect for the Health and Fitness Industry

as well as Dr. Siff, I take responsibility for the lack of explanation and

clarity of the said article and wish to clarify here.

As a beginning note, the magazine guidelines that this article was written

by did not allow for references, so none could be provided.

Regarding the terms " pronation " and " supination': these terms have been

coined to refer to the tri-planar motion of the lower extremity (foot/ankle,

knee, hip joint and L5-S1) during closed chain movements.1

The article states, " Pronation is the eccentric deceleration of forces that

allows the body to store potential energy... " This was an

oversimplification and in agreement with Dr. Siff, could be misleading. The

term Pronation simply refers to the collective tri-planar joint actions of

each respective joint from the foot to the hip (Table 1) that occurs in

conjunction with " closed chain " eccentric muscle action for force

reduction/absorption such as that seen during foot contact during walking,

stepping, running, or descending during a squat and/or the leg press. Thus

the term Supination simply refers to the collective tri-planar joint actions

of each respective joint from the foot to the hip (Table 1) that occurs in

conjunction with " closed chain " concentric muscle action for force

production such as that seen in push off during walking, stepping, running,

or ascending during squatting and/or the leg press. This was expressed in

the preceding paragraphs that were not mentioned in the critique,

" Functional biomechanics consists of movements termed pronation and

supination seen in Table 1.

Traditionally, pronation and supination have been used to describe motions of

the

forearm and/or the foot and ankle complex. However, because the joints of the

body are all connected, what happens at one joint directly effects the others

and thus

these terms will be used to describe the multiplanar motion throughout the lower

extremity in

this article " Again the reader is cautioned to examine criticism with all

of the pertinent information. Therefore, while Dr. Siff spent much of his

critique on the motions of the foot, the foot is only one component of the

lower extremity discussed in this article. All major joints of the lower

extremity were collectively discussed as they are collectively used in

functional activities.

TABLE 1

PRONATION:

Foot/ankle

Dorsiflexion (sagittal)

Eversion (frontal)

Abduction (transverse)

Knee

Flexion (sagittal)

Adduction (frontal)

Internal Rotation (transverse)

Hip

Flexion (sagittal)

Adduction (frontal)

Internal rotation (transverse)

SUPINATION:

Foot/ankle

Plantarflexion (sagittal)

Inversion (frontal)

Adduction (transverse)

Knee

Extension (sagittal)

Abduction (frontal)

External Rotation (transverse)

Hip

Extension (sagittal)

Abduction (frontal)

External rotation (transverse)

With regard to transverse plane motion, Dr. Siff points out, " ...that

rotation occurs about an axis and does not take place in any plane like the

transverse plane. " Well, in general most joint motion is rotary in nature

and therefore rotates about an axis. Depending on the motion performed,

however, (Flexion/extension, Add/abduction or rotation) the orientation of

the axis will differ from a Coronal (Medial/lateral) axis, to an

Anterior/posterior axis, to a Longitudinal (Vertical) axis, respectively and

thus be positioned in a different relative plane of motion.2 Of course we

know that " planes of motion " are imaginary so this is all just semantics,

but necessary for most all readers to establish a visual representation to

aid in the learning of information.

Lastly, I respectfully disagree with Dr. Siff's comment concerning foot

motion, " ...so, the primary question arises -- how is it possible to pronate

OR supinate the foot without any lateral movement or rotation of the foot in

any direction? The knees may undergo valgus or varus tilting and hip motion

may occur, but if the soles of the feet remain fully flat on any surface,

they cannot undergo any marked degree of pronation or supination (other than

a mild tendency to attempt to do so in some individuals) " AND " the

attention paid here to the largely insignificant actions of foot pronation

and supination is unwarranted. There are far more important issues to be

addressed. "

How does the foot pronate and supinate during walking and running when the

foot is on the ground? It has to pronate in order to properly absorb and

distribute the ground reaction forces in an eccentric manner and then

supinate to stiffen and provide the proper rigid lever to allow force

production in a concentric manner.1,2,3 During the initial foot contact and

stance phases of gait (eccentric), the tibia moves anteriorly over a fixed

foot (causing dorsiflexion at the talocrural joint, eversion at the subtalar

joint and translates into internal rotation at the tibia) while the opposite

motions occur for late stance and push off phases.2,3 This is the same

manner the lower extremity functions during a leg press or squat. Anyone

who has ever watched someone squat or perform a leg press without shoes on

and knows what to look for can attest to this, I assure you.

Here is a simple exercise that anyone who reads this can try. Stand up wherever

you

are right now and simply squat up and down a few times ( if you have a

mirror this will work better). Note what is happening at your feet and

knees especially. Does the orientation of the patella deviate medially or

laterally in relation to the 2nd & 3rd toes? What does the foot and ankle

do on the descent? Just pay attention for a couple of reps and you'll be

surprised what you see. Anecdotally everyday in our (NASM) clinic, we have

video analysis and goniometric data to support the movement, over-movement

or lack of movement associated with the foot/ankle complex and how this

relates to various injuries and dysfunctions. We are more than willing to

demonstrate this to anyone whom is interested in seeing it done practically

(live!) and not just reading about it. Knowledge that is never applied can

never become wisdom.

The motion of the foot is very significant because it will dictate the

motions of the joints above it.1,2,3 If the proper foot/ankle mechanics do

not occur, than the tibia/fibula cannot have proper motion. The tibia/fibula

is connected to the femur and hip/pelvis via IT band, Hamstring muscles and

Quadriceps muscles, Sartorius, Tensor fascia lata (via IT Band) and Gracilis

(amongst other connective tissue). So, if the tibia/fibula does not move in

the appropriate fashion, how can the femur and pelvis move appropriately?

If the pelvis is attached to the lumbar spine via the sacrum and all

concerned muscles and connected tissues, then can't the motion of the foot

also affect the lumbar spine?

Any wonder there is over 80% of the American population with back pain?4

As an industry we must begin to look at the human body as a whole whereby the

muscles, connective tissues, nerves and skeleton work together synergistically

to allow for proper motion and any alteration in one of these components causes

increased stress to the others as indicative of the low back pain seen in this

country

(as an example).5

Sincerely,

Rodney Corn MA, PES, CSCS

Director of Education

National Academy of Sports Medicine

rodney@...

www.nasm.org

References:

1) Bronner S. Functional rehabilitation of the spine: The lumbopelvis as a

key point of control. Chapter 5. In Brownstein B, Bronner S (eds.).

Evaluation, treatment and outcomes: Functional movement in orthopaedic and

sports physical therapy. New York: Churchill Livingstone; 1997. p.194.

2) Neumann DA. Kinesiology of the musculoskeletal system. Foundations for

physical rehabilitation. St. Louis, MI: Mosby, Inc.; 2002.

3) Nordin M, le VH (sic). Biomechanics of the musculoskeletal system. 3rd

edition. Philedelphia: Lippincott & Wilkins; 2001.

4) Whiting WC, Zernicke RF. Biomechanics of musculoskeletal injury.

Champaign, IL: Human Kinetics; 1998.

5) Panjabi MM. The stabilizing system of the spine. Part 1: Function,

dysfunction, adaptation and enhancement. J Spinal Disord 1992;5:383-9.