B Y D A N I E L M E T Z

Excessive pronation, lower leg muscle fatigue, and recreational runners

Purpose

The purpose of this study is to examine the relationship between lower extremity muscle fatigue and the resulting change in degree of foot pronation in recreational runners.

The results will shed light onto possible effective training techniques to reduce excessive pronation in recreational runners.

Why so Important?

Overuse injuries are associated with excessive pronation

Murphy and Connors (2009) state “the foot is a hugely important area for a runner, because it is the first point of contact with the ground and directs all the forces through the body.”

Kinetic Chain Theory Injury concentration?

Foot Structure

The main components of the foot 26 bones 31 major synovial joints 20 intrinsic muscles

The foot has two axes One axes runs horizontally through the talus The other axis runs diagonally The movements the foot makes around this diagonal

axis are pronation and supination

Subtalar Joint and Talocrural Joint

Talocrural Joint

Excessive Pronation

Pronation can also be defined as…The movement of the subtalar joint

articulating around the calcaneous Eversion

(turning the sole outwards) Dorsiflexion

(pointing the toes upwards) Abduction

(pointing the toes out to the side)

How much muscular activity is involved?

Effects of Muscle Fatigue

Muscles that play a role? Extrinsic and Intrinsic

Extrinsic muscles “originate from the tibia, fibula, or femur and act on the ankle as well as joints within the foot

Intrinsic muscles are “small ones which originate on other foot or ankle bones and act only on joints within the foot”

Recreational Runners

Highly Individual as opposed to team sportsEssentially the sum of one’s individual effort.

Motivations to run include… Weight lose Increasing muscle tone Strengthening the heart Increasing aerobic capacity Lowering blood pressure Reducing depression among a number of other reasons.

Recreational Runners

Typical Runner Demographic Higher economic class (93% college educated), Married (74% and 62% for males and females respectively) A frequency of about an average of twenty miles a week

spread across an average of four runs (2008: state of the Sport: Part II, 2009).

Road Race Finishers

Men Women

1997 3 million 800,000

2007 4.5 million 4.4 million

My Population

Three to six Junior or Senior SPU students

Represents a larger scale sample of young college aged individuals

A recreational runner for this study will be a male or female college aged runner who runs between three and twelve miles a week

Methodology

Experimental Design using a video analysisThree protocols of barefoot run

1st recording Fatigue protocol 2nd recording

Markers will be placed on foot and ankle

Exposing participant to fatigueMeasure the change in biomechanics using

coordinates

Marker Locations

Protocol #1

Shoes and socks will be removedHeight and Weight will be takenMarkers set in place

the posterior aspect of the calcaneous, the medial aspect of the calcaneous, the medial aspect of the tibia, the medial aspect of the navicular bone, the medial aspect of the talus

Vertical line drawn on calcaneous tendonRecord 30 sec. run at 6.5 mph

Protocol #2

The maximum distance between the plantar surface of the heel and the ground during will be measured. This will serve as a reference point to

measure the amount of fatigue in the intrinsic and extrinsic muscles of the foot and ankle.

Follow this by completing one leg standing calf raises barefoot on the right foot with audible encouragement. Continue to complete repetitions until the distance

between the plantar surface of the heel and the ground is less than 50% of the maximum distance originally measured for that participant (fatigue).

Protocol #3

Markers will already be in place the posterior aspect of the calcaneous, the medial aspect of the calcaneous, the medial aspect of the tibia, the medial aspect of the navicular bone, the medial aspect of the talus

Vertical line will be in placeRecord barefoot run for 30sec. At 6.5mphWith both videos, variances will be measured

recording the change in (X, Y) locations

Results

Hoping there will be a difference in coordinate location

The posterior calcaneous markerwill be used as the reference coordinate (0, 0)

Use this to calculate change in location of coordinates of the x and y points

This change due to a hypothesized movement in the medial and inferior direction, and these differences will show the change in degree of pronation

Results

Three participants filmed

All three male and all mildly to moderately overpronated

Calculated the differences in the x and y coordinates in a frame where pronation peaked

For each of the two videos, non-fatigued and fatigued, I calculated the coordinates twice using two consecutive strikes taking for each of the three participants

I Compared…

Results for each Participant

    Partcipant 1   Participant 2   Participant 3 Coordinate Mean Diff 

NF XMean Diff F X

 

Mean Diff NF X

Mean Diff F X

 

Mean Diff NF X

Mean Diff F X

 Posterior Heel 0 0 Ref  0 0 Ref  0 0 Ref 

Posterior Calf -3.5 -6.5 right 3 -9.5 -9.5 no change -4 -3.5 left .5Upper Calf -9 -14 right 5 -18 -19 right 1 -10 -10.5 left .5

Medial Tibia 30.5 23.5 right 7 18 19.5 right 1.5 33 30.5 right 2.5

Medial Ankle 31 27 right 4 16 19.5 right 3.5 35 30.5 right 4.5

Medial Talus 27 26.5 right .5 15 15.5 right .5 27 24 right 3

Medial Heel 24.5 21 right 3.5 18 20.5 right 2.5 22 21 right 1

Mean X Coordinates Results

RED= Not Fatigued BLUE = Fatigued

Measured in pixels or mm 47 mm = 47.2 pixels

Mean Y Coordinates Results

RED= Not Fatigued BLUE = Fatigued

Measured in pixels or mm 47 mm = 47.2 pixels

Discussion

Results were not consistent with hypothesis Measurable change indicated measurability error One pixel equals one mm Biomechanics measured through coordinates

indicated no change in foot pronation

Extrinsic and intrinsic muscle fatigue indicated little measurable change

Changes were averaging around 1 to 2 mm

Discussion

Why? The fatigue protocol was not effective

Level of difficulty Insufficient intrinsic foot muscle fatigue More than one set to measured fatigue

Recovery Fast muscle recovery

Speed not fast enough to recruit significant muscle involvement Not enough force

Scale in software coordinate analysis too small Foot pronation limited range of movement in joint

Limitations

Limited testing equipment For the small amount of movement, my video

measurements were not accurate enough to give results. ImageJ limitations - zoom If there was a measurable change, it needs higher

accuracy equipment for the analysis. Software can do more complex analysis

Limited population Only males Limited age range Smaller population Similar biomechanics Variability in stride

Conclusion

This fatigue protocol seemed to have little to no effect on the degree of overpronation in the predicted way Lower leg muscular fatigue had no measurable change in foot

pronation Variation in coordinates from non-fatigued to fatigued had

mean differences only slightly different More accurate medical equipment is needed with multiple

angle camera views and a smaller scale Future studies

Include more intricate fatigue protocol Increase zoom in camera More advanced zoom in software Other camera angles