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Munro Ground Reaction Forces in Running

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Munro Ground Reaction Forces in Running Powered By Docstoc
					Ground Reaction Forces in
Running: A Reexamination

   C F Munro, D I Miller & A J
          Fuglevand
                             Methods
   20 male subjects ran at speeds 2.5 – 5.5 m/s
   Kistler force plate interfaced to PDP 11/34 computer 1000 Hz
   Photocells positioned 5 m apart to monitor average velocity
   Subjects wore their own shoes
   Trials where the change in Vy was greater than ± .10 m/s were
    rejected (Ant/Pos force was integrated)
   Stance time was defined as Fz > 16 N
   Loading rate was defined as the time to from 50 N to BW + 50 N
   Decay rate was defined as the time from BW + 50 N to 50 N
    following Thrust Max
   Impulses and Forces were normalized by dividing by body weight in
    Newtons
   Right and Left foot trials were averaged
                                         Loading Rate Calculation

                        1800   Loading Rate Calculation
                                                 Fz
                        1600
                                                                           Loading Rate
                        1400

                        1200
Vertical Force Fz (N)




                                            Loading Rate = 1/(.028-.014)
                        1000                Loading Rate = 71.4 BW/s

                        800
                                   time at BW+50 N =.028
                        600

                        400

                        200
                                   time at 50 N = .014
                          0
                               0    50        100          150       200        250       300
                                                         Time (ms)
Anterior – Posterior
   Force Curves



Increasing running
speed increases the
magnitude of A/P
forces and decreases
stance time.
    Variability in Braking
          Patterns



Rearfoot have a single peak
braking pattern.
Midfoot runners have two or
more peaks during braking.
    Vertical GRF as
     a function of
    running speed




Increasing running
   speed:
1. Increases impact
2. Increases loading
   rate
3. Increases thrust
   max
4. Decreases stance
   time
  Medial –
Lateral Force
   Curves


Stance time
decreases and
magnitude of
peaks
increases with
increasing
running speed.
 Impulse



Braking and
Propulsion
increases
with
increasing
running
speed.
Vertical Force Variables as a Function of Running Speed

				
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posted:12/11/2011
language:English
pages:9