Kinetic changes with fatigue and relationship to injury in female runners.
OBJECTIVE
This research examined how ground reaction forces (GRF) changed with fatigue induced by an exhaustive treadmill run in female runners. A separate retrospective and prospective analysis correlated initial magnitude of GRF and fatigue-induced changes in GRF with lower-extremity injury.


METHODS
Ninety adult female runners had vertical GRF measured before and after an exhaustive treadmill run. Subjects initially were questioned about previous running injuries, and were contacted during the following year and asked to report any additional running injuries.


RESULTS
Fatigue induced by the exhaustive treadmill run resulted in decreased impact peak and loading rates in all runners by an average of 6 and 11%, respectively. The changes in GRF were attributed to altered running cadence, step length, and lower-extremity joint kinematics. It is unclear whether these changes were attempts by the runners to minimize impact forces and protect against injury, or represented a fatigue-induced loss of optimal performance capabilities. An interaction between injury in the previous year and change in impact loading rate with fatigue was observed, suggesting previously injured runners are exposed to relatively higher impact forces over time.


CONCLUSIONS
Habitual female runners appear to adapt their running style with fatigue, resulting in altered GRF. Changes in GRF with fatigue may be associated with lower-extremity running injuries.
Gerlach
Kristen E
KE
Department of Exercise and Nutrition Sciences, University at Buffalo, State University of New York, Buffalo, NY 14214-3079, USA.
White
Scott C
SC
Burton
Harold W
HW
Dorn
Joan M
JM
Leddy
John J
JJ
Horvath
Peter J
PJ
D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D004812:Epidemiologic Methods; D005080:Exercise Test; D005221:Fatigue / Q000503:physiopathology*; D005260:Female; D005684:Gait / Q000502:physiology; D006801:Humans; D035002:Lower Extremity / Q000293:injuries; D008875:Middle Aged; D010101:Oxygen Consumption; D012420:Running / Q000293:injuries / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology