Monday, September 22, 2003 - Physiology
Powering Up The Core (Part 5 of 6)

- By: Ross McKinnon, PT

The tests and exercises described should be performed with the help of a physiotherapist to achieve maximal benefit.
Emphasizing strength training is not effective to improve performance if there is existing muscle imbalance and poor stability in the musculoskeletal system. Strength exercises target the power/mover muscles. Focusing on strengthening the mover/power muscles will typically not correct muscle imbalance, rather it will result in further compensation. While strengthening exercises require a certain degree of stabilization, it is commonly the incorrect muscles that try to provide the stability when muscle imbalance exists. Strengthening the power muscles is very important once the stability system is working optimally. In this section we will review two tests that athletes can use to assess their progress in core strength. Further tests should also be performed similar to the testing the National and National Development team use – check the archives on Skifaster.net. These tests have very specific protocols which must be closely followed to reliably track improvement.

Upper abdominal Strength
Test procedure: The athlete lays on their back with the spine and pelvis in neutral alignment. Both legs are extended. There are two phases to the trunk curl movement. The first component is trunk flexion and posterior tilt of the pelvis and spine. The second component is hip flexion. Ideally, the abdominals should flex the trunk first and then the hip flexors should be able to lift the trunk over the pelvis to come up to a sitting position. The abdominals must maintain the posterior tilt of the pelvis during raising and lowering of the trunk. Avoid extension of the lumbar spine or lifting the feet off the floor. Avoid using momentum and ‘jerking’ during raising. See Table 1 below for grading.

100% Upper abdominal strength
(From Commerford 2001)
Double leg lowering Strength
Test procedure: The athlete lays on their back with the spine and pelvis in neutral alignment. Both legs are extended. Forearms are folded on the chest to ensure the elbows are not resting on the table for support. The tester assists lifting the legs to a vertical position. The athlete must posteriorly tilt the pelvis by contracting the abdominal muscles. The back must be held flat against the floor throughout the test. The athlete is then asked to lower the legs. The tester monitors the angle at which the pelvis and spine tilt away from the floor. Avoid excessive rectus abdominus bulging, breath holding and extension of the head and neck. See Table 1 below for grading.

80% (30°) Lower Abdominal Strength
(Modified from Kendall)


TABLE 1 – Interpretation of abdominal tests
Grade Lower abdominals Upper Abdominals
50% 75 degrees keeps spine flexed but cannot sit up with forearms extended
60% 60 degrees keeps spine flexed and sits up with forearms extended
70% 45 degrees
80% 30 degrees keeps spine flexed and sits up with forearms folded on chest
90% 15 degrees
100% 0 degrees keeps spine flexed and sits ups with hands touching ears

CROSS COUNTRY SKI SPECIFIC CORE STRENGTH PROGRAM
This program has been updated from the original version

Remember to use a correct breathing pattern with these exercises

Lateral Abdominals
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. To properly recruit and isolate the inner unit the advice of a physiotherapist or other professional may be required.

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
(From Comerford 2001)

HUNDREDS
The athlete should lie on their back with their arms at the side palm down and legs extended. The athlete should then bend their knees towards their chest. The athlete will then tension their inner unit as in level 0 above while flattening their spine to the floor. The athlete will then simultaneously lift their chin and shoulders off the floor (the bottoms of the shoulder blades should stay in contact with the ground) while extending the legs, the legs will be at an angle that the athlete can maintain without arching their back. The athlete will then inhale slowly through the nose while counting with each inhalation. With each count the athlete will pump their hands (by moving their shoulders only) down to the floor using the Lats. The athlete will then perform five breaths out through the mouth again pushing the hands towards the floor with each breath. In Pilates the goal is 10 sets of 10 breaths in a row hence the name Hundreds. With the other exercise this can be performed for one minute. This is an exercise taken from Pilates which I think is excellent to improve the function of the oblique abdominal muscles and the lats – which are crucial to poling.



Sidelying Hip Abduction
The athlete is positioned side lying 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 it straight. Avoid allowing the hip to flex forward (this is the most common source of error), hitching the pelvis, rotating the spine or pelvis backwards, or using the outside hamstring muscles to lift. This exercise is best performed with the athlete’s back, hips and heel to a wall.

Lower Abdominal Leg Raises
The athlete lies on their back. Keep the lower back and head on the floor at all times. Avoid turning the toes in, and excessive rectus abdominus bulging. Ideally there should be a balance between all abdominal muscles. The athlete should try to maintain the belly button into the spine as per the rotation stability exercises – this will balance the abdominal muscles. Maintain proper rib cage breathing while maintaining abdominal control. This exercise is similar to the lower abdominal test above.

Level 1 Bend one leg. Raise the other leg straight 3 seconds up, 3 second hold, 3 seconds down.
Level 2 Raise both legs to 75°, hold for 1 minute, and bend knees as fatiguing
Level 3 Same as level 2, hold legs straight for the entire minute
Level 4 Raise both legs to 60°, hold 1 minute with legs straight
Level 5 Raise both legs to 45°, hold 1 minute with legs straight
Level 6 Raise both legs to 45°; perform small scissor kicks and circles hold 1 minute with legs straight
Level 7 Raise both legs to 30°, mix static and dynamic movements hold 1 minute with legs straight
Level 6 Raise both legs to 15°, mix static and dynamic movements for 1 minute with legs straight.


Lower Back – Alternating arms and legs prone pointer
The athlete lies on their stomach with a pillow under the hips. Lift opposite arms and legs with the hips and head down. Ensure the thumb of the raising arm is pointed upwards. Ensure the gluteus maximus is performing the leg lift and that the movement is not initiated by the hamstrings or spine muscles. Avoid spinal rotations or extension of the spine. Excessive arching increases compressive loads to the spine to very high levels.

Trunk Curl with Straight Legs
Remember that a straight leg curl up is potentially damaging if done incorrectly. If no proper instruction is available the athlete is best to perform these exercises with the knees bent. The athlete lays on their back with the spine and pelvis in neutral alignment. Both legs are extended. There are two phases to the trunk curl movement. The first component is trunk flexion and posterior tilt of the pelvis and spine. The second component is hip flexion. Ideally, the abdominals should flex the trunk first and then the hip flexors should be able to lift the trunk over the pelvis to come up to a sitting position. The abdominals must maintain the posterior tilt of the pelvis during raising and lowering. Avoid extension of the lumbar spine, lifting the feet off the floor. Avoid using momentum and ‘jerking’ during raising. The athlete should breathe in while lifting the trunk and breathe out while lowering. The trunk curl with straight legs more closely resembles the muscle strength needed for double poling than with knees bent. See the previous skifaster.net articles for further information.

Level 1 Start exercises with both knees bent, extending knees as the torso is raised.
Level 2 Curl up with both knees extended
Level 3 Hand crossed on chest
Level 4 Hands to ears
Level 5 Hands to spine between shoulder blades
Level 6 Arms straight overhead
Side Trunk Raise
The athlete lies on their side. The athlete raised their torso and legs off the floor, supported by only the feet, elbow and forearm. Avoid rotation or side bending of the trunk. During Level III as athletes tire they will tend to rotate their stomach towards the floor allowing them to use their TFL to lift their leg rather than the more important posterior glut medius. The athlete should breathe in while lifting and breathe out while lowering.
Level 1 Support the body at the knees rather than the feet
Level 2 Support the body at the feet
Level 3 Supported at the feet, trunk raise plus raising the uppermost leg to the ceiling

Bridging (Optional)
The athlete should lay on their back with both knees bent. The heels and knees should touch. The athlete will then recruit the inner unit, then isometrically contract the gluteal muscles and lift themselves from the floor. During each level of progression the athlete should maintain a stable lumbar neutral position without arching or rotating the spine.

Level I


Level II
As with Level I but with small marching steps alternating legs

Level III
As with level II but with knee extensions

Level IV
The athlete holds the position as in III as well as A) flexes the knee and hip to a 90° angle and then returns to knee extension and B) lowers the leg almost touching it to the floor


Level V
The athlete will place their feet on a physiotherapy ball or soccer ball while performing a bridge.


Level VI
As Level V but rolling the ball back and forth using both legs

Training recommendations The following are suggestions for progression of the cross country ski specific core stability and strength program. Each exercise can be made more difficult as described. Perform each exercise for 3 seconds up, 3 second hold and 3 seconds down unless otherwise described for one minute.

Level A Complete all exercises without rest, rest two minutes repeat all exercises.
Level B Complete all exercises without rest, rest one minute repeat all exercises.
Level C Complete all exercises without rest two times.
Level D Complete all exercises without rest three to five times as able.

These exercises should be performed three times weekly during the recovery, general preparation, specific preparation, pre-competitive and general competitive phases. These exercises can be performed once a week during the taper phase and eliminated if wanted during the peak phase.

Fundamental Stage – ages 12 and under. Core strength and stability exercises can be introduced to develop strength, stability and coordination. The neutral spine position can be introduced. The exercises can be reduced to 15-20 seconds and performed one time weekly during training sessions.

Midgets – ages 13-14. Up to 2-3 sets with breaks between sets. 1-2 times a week.
Juveniles - ages 15-16. Up to 2-3 sets with breaks in between sets. 3x a week during the training phases. 2x a week during the competition season.
Juniors – ages 17-20. Up to 3-4 sets without breaks. Ideally 3x week as outlined above Seniors/ Masters ages 21+ as above
It is advisable that anyone starting a core stability/strength program that is not already doing strength training start at the juvenile level.
(Adapted from Saar 1998)

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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