Welcome to the Podiatry Arena forums, for communication between foot health professionals about podiatry and related topics.
You are currently viewing our podiatry forum as a guest which gives you limited access to view all podiatry discussions and access our other features. By joining our free global community of Podiatrists and other interested foot health care professionals you will have access to post podiatry topics (answer and ask questions), communicate privately with other members (PM), upload content, view attachments, receive a weekly email update of new discussions, earn CPD points and access many other special features. Registered users do not get displayed the advertisments in posted messages. Registration is fast, simple and absolutely free so please, join our global Podiatry community today!
If you have any problems with the registration process or your account login, please contact contact us.
Stress fractures are a common and serious overuse injury in runners, particularly female runners. They may be related to loading characteristics of the lower extremity during running stance. Some tibial stress fractures (TSFs) are spiral in nature and, therefore, may be related to torque. Free moment (FM) is a measure of torque about a vertical axis at the interface with the shoe and ground. Increases in FM variables may be related to a history of TSF in runners. The purpose of this cross-sectional study was to investigate differences in FM between female distance runners with and without a history of TSF and, additionally, to investigate the relationship between absolute FM and the occurrence of TSF. A group of 25 currently uninjured female distance runners with a history of TSF (28+/-10 years, 46+/-15km week(-1)) and an age- and mileage-matched control group of 25 healthy runners with no previous lower extremity fractures (26+/-9 years, 46+/-19km week(-1)) participated in this study. Ground reaction forces and foot placement on the force platform were recorded during running at 3.7ms(-1) (+/-5%). Peak adduction, braking peak and absolute peak FM and impulse were compared between groups using one-tailed t-tests. The predictive value of absolute peak FM was investigated via a binary logistic regression. All variables, except impulse, were significantly greater in runners with a history of TSF. Absolute peak FM had a significant predictive relationship with history of TSF. There is a significant relationship between higher values for FM variables and a history of TSF.
Kinetic asymmetry in female runners with and without retrospective tibial stress fractures
Quote:
Gait asymmetry may be linked to the tendency for runners to sustain chronic overuse injuries. This paper compares gait asymmetry in female runners who have never sustained a running-related injury to those who have sustained unilateral tibial stress fractures. The symmetry index was used to characterize asymmetry in the kinetics of both subject groups. There were three aims to this study: (1) to report natural levels of asymmetry for healthy, never-injured female runners, (2) to compare asymmetry levels between never-injured runners and those who have sustained stress fractures, and (3) to examine the kinetics between the involved and uninvolved limbs of runners who have sustained stress fractures. In all three aims, peak medial, lateral, braking, vertical impact, and vertical ground reaction forces, average and peak instantaneous vertical loading rates, and peak shock were examined. In the never-injured runner group, natural levels of asymmetry ranged from 3.1% for peak vertical ground reaction force up to 49.8% for peak lateral ground reaction force. Symmetry indices were not significantly different in the runners who had previously sustained stress fractures. The involved limb of the previously injured runners demonstrated higher values for braking and vertical impact ground reaction force and peak shock. Interestingly, these runners appeared to have bilaterally-elevated lateral ground reaction forces and loading rates as compared to the never-injured group, although this was not statistically tested. This suggests that previously injured runners may be closer to the injury threshold and, thus, more susceptible. Asymmetry may simply influence the side on which they become injured.
What the hell
means freemoment?
I am german orthosurgeon and I (63) read this word the first time, trying out to find what ist means exactly.
Sincere Gerhard Fleischner Schliersee Germany
What the hell
means freemoment?
I am german orthosurgeon and I (63) read this word the first time, trying out to find what ist means exactly.
Sincere Gerhard Fleischner Schliersee Germany
Gerhard:
Welcome to Podiatry Arena, Gerhard.
Free moment is simply the torsional force acting on the foot and/or lower extremity that is generated by frictional forces between the foot and ground during weightbearing activities. Free moment is determined by a force plate and the direction of the moment is within the plane of the force plate (i.e. transverse plane in vertical standing). A free moment would tend to cause a torsional force along the long axis of the tibia/fibula and femur during weightbearing activities. Free moment is a relatively new term in biomechanics which I just heard for the first time last month during a presentation given by Dr. Irene Davis at the PFOLA seminar in Vancouver.
**************************************************
Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College
Kinetic asymmetry in female runners with and without retrospective tibial stress fractures
Rebecca Avrin Zifchock, Irene Davisa, and Joseph Hamill
Journal of Biomechanics Volume 39, Issue 15 , 2006, Pages 2792-2797
Quote:
Gait asymmetry may be linked to the tendency for runners to sustain chronic overuse injuries. This paper compares gait asymmetry in female runners who have never sustained a running-related injury to those who have sustained unilateral tibial stress fractures. The symmetry index was used to characterize asymmetry in the kinetics of both subject groups. There were three aims to this study: (1) to report natural levels of asymmetry for healthy, never-injured female runners, (2) to compare asymmetry levels between never-injured runners and those who have sustained stress fractures, and (3) to examine the kinetics between the involved and uninvolved limbs of runners who have sustained stress fractures. In all three aims, peak medial, lateral, braking, vertical impact, and vertical ground reaction forces, average and peak instantaneous vertical loading rates, and peak shock were examined. In the never-injured runner group, natural levels of asymmetry ranged from 3.1% for peak vertical ground reaction force up to 49.8% for peak lateral ground reaction force. Symmetry indices were not significantly different in the runners who had previously sustained stress fractures. The involved limb of the previously injured runners demonstrated higher values for braking and vertical impact ground reaction force and peak shock. Interestingly, these runners appeared to have bilaterally-elevated lateral ground reaction forces and loading rates as compared to the never-injured group, although this was not statistically tested. This suggests that previously injured runners may be closer to the injury threshold and, thus, more susceptible. Asymmetry may simply influence the side on which they become injured.
Going to take my life in my hands and try to explain freemoments.
The Free moment exists because of the unique ability of the foot to push in two direction at once by twisting about an instantaneous vertical (y) axis on the forceplate.
This causes a small moment at the centre of the force couple under the foot.
This is not possible in the horizontal axes unless the foot is adhered in some way to the foorceplate.
The freemoment is calculated as a product of the X and Z forces, the distance between strain gauge posts and the Horizontal CoP of interest (xCoP or zCoP) Typical peak values are 3 -6N/m.
This freemoment is not the same as the moment about the vertical y axis of reference of the force plate. These are produced by any force tending to rotate the force plate around its referential centre. There are no typical peak values since the moment value is determined by position and magnitude of the horizontal force on the force plate.
See attached for details.
The magnitude of the moment transmited thru the limb of interest, the Femur or Tibia for instance, is determined by the Cosine of the limb's angle of inclination to the forceplate.
So if the tibia was directly above the freemoment (magnitude 3N/m) and at an angle of 45dgs then 2.12N/m torque could be transmitted along the tibia.
If then the Femur was perpendicular to the ground then only 1.49N/m would be transmitted to the Femur. At 90dgs the transmission is zero as the Cos of 90 is zero.
Therefore freemoments probably do not have a direct correlation with torsional stress in a long bone. Rather the style of gait that produces freemoments may also produce high torsional stresses in the long bones.
So for example if you were a forefoot striking runner with a toe out gait this may produce quite high peaks of freemoments, the freemoments themselves are not pathological to the long bones but the torque that is produced by gait style IE the high posteriorly acting horizontal GRF acting on the toe out forefoot will produce a proportionatly high moment at the tibia and incidentally a twisting action under the mets, which produce a relatively high freemoment.
Cheers Dave Smith
Last edited by David Smith : 26th October 2006 at 11:54 PM.
Free moments and tibial stress fractures
Free moments and stressfracture
Linear Mode
