Ground Reaction Forces in Running: A Reexamination
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Transcript of Ground Reaction Forces in Running: A Reexamination
Ground Reaction Forces in Ground Reaction Forces in Running: A ReexaminationRunning: A Reexamination
C F Munro, D I Miller & A J C F Munro, D I Miller & A J FuglevandFuglevand
MethodsMethods 20 male subjects ran at speeds 2.5 – 5.5 m/s20 male subjects ran at speeds 2.5 – 5.5 m/s Kistler force plate interfaced to PDP 11/34 computer 1000 Kistler force plate interfaced to PDP 11/34 computer 1000
HzHz Photocells positioned 5 m apart to monitor average velocityPhotocells positioned 5 m apart to monitor average velocity Subjects wore their own shoesSubjects wore their own shoes Trials where the change in Vy was greater than Trials where the change in Vy was greater than ±± .10 m/s .10 m/s
were rejected (Ant/Pos force was integrated)were rejected (Ant/Pos force was integrated) Stance time was defined as Fz > 16 NStance time was defined as Fz > 16 N Loading rate was defined as the time to from 50 N to BW + Loading rate was defined as the time to from 50 N to BW +
50 N50 N Decay rate was defined as the time from BW + 50 N to 50 N Decay rate was defined as the time from BW + 50 N to 50 N
following Thrust Maxfollowing Thrust Max Impulses and Forces were normalized by dividing by body Impulses and Forces were normalized by dividing by body
weight in Newtonsweight in Newtons Right and Left foot trials were averagedRight and Left foot trials were averaged
Loading Rate CalculationLoading Rate CalculationLoading Rate Calculation
0
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0 50 100 150 200 250 300Time (ms)
Ve
rtic
al F
orc
e F
z (N
)
Fz
Loading Rate
time at 50 N = .014
time at BW+50 N =.028
Loading Rate = 1/(.028-.014)Loading Rate = 71.4 BW/s
Anterior – Posterior Anterior – Posterior Force CurvesForce Curves
Increasing running speed increases the magnitude of A/P forces and decreases stance time.
Variability in Variability in Braking PatternsBraking Patterns
Rearfoot have a single peak braking pattern.
Midfoot runners have two or more peaks during braking.
Vertical GRF Vertical GRF as a function as a function
of running of running speedspeed
Increasing running speed:
1. Increases impact
2. Increases loading rate
3. Increases thrust max
4. Decreases stance time
Medial – Medial – Lateral Force Lateral Force
CurvesCurves
Stance time decreases and magnitude of peaks increases with increasing running speed.
ImpulseImpulse
Braking and Propulsion increases with increasing running speed.
Vertical Force Variables as a Function of Running SpeedVertical Force Variables as a Function of Running Speed