Wednesday, April 9, 2003 - Physiology
Are you stable? (Part 2 of 6)

- By: Ross McKinnon, PT

The tests and exercises described should be performed with the help of a physiotherapist to achieve maximal benefit. 

Traditional strengthening and core strength programs focus on the mover/power muscles.  However it is critical that the stability muscle system must first be functioning properly for optimal sport performance and injury prevention.  Strength training is crucial to improve ski performance but an athlete must first be able to control movements through correct use of the stability system.  THE ABILITY TO CONTROL MOVEMENTS AND THEREFORE OPERATE AT MAXIMAL PERFORMANCE WILL RARELY IMPROVE WITH STRENGTHENING EXERCISES ONLY.  It is important to first assess if the stability system can control, under low load conditions, movements of the extremities and spine.  Once the local stability system can work properly a program of muscle lengthening and strengthening can be started.

Muscles are broadly divided into stabilizers and mover/power muscles (i.e. rotator cuff and deltoid).  Movers are the muscles that provide the power for sport performance.  Stabilizers are the muscles that provide the control during these movements.   All muscles provide power and stability; however each muscle is designed to be most efficient in one role.  Both systems must work together for optimal efficiency


Good Stability

Poor Stability


high performance

poor performance


pain free


Stability of the trunk or ‘core’ requires two muscle systems to work in unison.  The two systems are called the inner and outer units.  The inner unit consists of the multifidus, transverse abdominus, diaphragm, psoas major, the pelvic floor and diaphragm.

(Redrawn from Lee 1999)


The athlete should lie on their back with their hips and knees bent.  The athlete should place both their hands on their stomach approximately 3cm down and in front of the anterior crest of the pelvis.  The natural curve of the spine must be maintained. i.e. the neutral spine.  The athlete is instructed to “draw the belly button into the spine”.  The front and lateral aspects of the abdominal wall should lead the contraction.  There should be no tilting of the spine or pelvis, any upper abdominal tension, any internal oblique bulge, rib cage elevation, or breath holding.  The athlete is to maintain this position for 15 seconds 2 times with normal rib cage breathing.  This isolation requires <25% effort and is not a maximal effort.  It is very common for an athlete to try and stabilize by bulging of the rectus abdominus.  The neutral spine must be maintained throughout the testing (by step 3 it is ok to flex the spine slightly).  Check that the athlete can first perform the inner unit recruitment exercise (Level Ø) properly prior to testing higher levels.

Normal: athletes should attain level 4

Level Ø           Inner unit recruitment
Level 4 As above with heel touch
Level 1            Single leg knee lifts
Level 5 Lower both legs from 90°double leg heel slide
Level 2 Both knees to 90°.  Lower one knee at a time, then up, repeat with opposite
Level 6 Lower both legs from 90°double leg lowering
Level 3 As above with heel slide
(Commerford 2001)

Test procedure:
The athlete lays on their back with the spine and pelvis in neutral alignment.  The leg to be tested is bent, while the opposite leg is straight.  The athlete is instructed to lower the test leg out to the side. 
Normal: the athlete should be able to dissociate the movements of the hip

from the pelvis and lower back and lower the leg halfway to the floor.
Stability dysfunction:  The athlete’s spine and pelvis rotate greater than ½”.  This problem is most likely one sided.


Test procedure:  The athlete is positioned sidelying with their spine and pelvis in neutral alignment.  The lower leg is slightly flexed for support.  The uppermost leg is extended and slightly outwardly rotated (toes to the ceiling).  The athlete is asked to lift the leg to the ceiling keeping is straight.  Avoid allowing the hip to flex forward (this is the most common source of error), hitching the pelvis, or rotating the spine or pelvis backwards.

Normal:  The athlete can hold this position against maximal effort and can perform 2 leg lifts holding each for 15 seconds without tiring.


The athlete should lay on their stomach with both knees extended.  The athlete’s leg is passively bent to a point of resistance in the thigh or where the spine begins to extend and/or rotate.  The athlete is then asked to bend one knee at a time on their own.  The tester checks for full knee range of motion to 120°

and the ability to achieve this range without extending and/or rotating the spine.


The athlete should lay on their stomach with both knees extended. The athlete is then asked to bend one knee to a 90° angle.  The athlete is then asked to lift that bent leg towards the ceiling as high as possible without extending or rotating the spine.  The athlete is asked to maintain that position against the tester’s maximal resistance.  The hip should be able to achieve 10°of hip extension.   The athlete is then asked to maintain this position holding each leg up in the inner

range position of 2 x 15 seconds without fatigue or muscular compensation.  If the athlete begins to feel a cramp in their hamstrings muscles this is a sure sign of glut maximus weakness.


The athlete should position themselves in single leg standing with their knee aligned over the 2 and 3rd toes.  The athlete should be able to maintain their pelvis and shoulder level.
The athlete is then asked to maintain the position of the leg while rotating the trunk on the hip joint, both to the inside and out.  This is partly a check of balance but also the ability to stabilize the hip and spine and move each part individually.  This move is critical to the

ability to ride a flat ski and have equal weight shift bilaterally.  The athlete should be able to rotate on each leg slowly for 30 seconds.  Check for excessive loss on the arch in the foot, dropping one side of the pelvis or one shoulder or the inability to move the spine without moving the hip.


The athlete should lay on their back with their arm abducted to a 90° angle.  A pillow should be place under the athletes elbow so that the elbow is slightly higher than the athletes shoulder.  The athlete is then asked to rotate their shoulder backwards by moving the back of their hand to the pillow and forwards by moving the palm of their hand towards the pillow.  These are termed internal and external rotation of the shoulder.
Normal:  The athlete can achieve 70° of internal rotation (palm down) and 90° of external rotation without forward motion of the head of the humerus or movement of the shoulder blade.   The head of the humerus should be felt to pivot and not shift forward during the testing

Glenohumeral dysfunction: the head of the humerus will be felt by the tester to glide anteriorly during the forward motion of the arm
Shoulder blade dysfunction:  Both the head of the humerus and the shoulder blade will tilt forward during motion of the arm. 
*If either test is positive a further examination should be performed by a physiotherapist to determine if further corrective exercises are required.


Typically the power/mover muscles will become tight and short, i.e. the muscles that always feel tight and need to be stretched.  In fact they are overworked as they are trying to provide stability and power due to ineffective local stabilization.  The power/mover muscles then are less effective to generate force as they have become increasingly used for stability (the ideal length/tension relationship is altered).  Stability muscles will lengthen and become weak resulting in ineffective control as well as altered timing and recruitment.  To improve muscular efficiency and balance a proper program of muscle activation and lengthening must be undertaken.  The athlete would perform any stability test they did poorly on as part of their daily exercise program.  The goal is quality not doing the exercises mindlessly.  As the exercises are largely relearning muscle activation patterns and control concentration and focus is critical.  Each exercise should be performed for 10x10seconds.  Once an athlete can perform the exercises without fatiguing then they can continue the exercises but less frequently i.e. 2-3 x weekly.  Once the stability muscles are able to control movement muscle lengthening exercises can begin.  In the part III we will review muscle lengthening with control of the ‘give’.

Ross McKinnon is a former ski racer now working as a physiotherapist at Rutland Physical Therapy in Kelowna, BC. His interests include improving an athlete's performance through the use of specific exercise. For further questions he can be contacted at or at . Ross provides individual evaluations to help improve performance and prevent injury.


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