Transcript Fast vs slow running loads - UNC 2015

FASTER VS SLOWER RUNNING REDUCES TOTAL ACCUMULATED LOADS
Kayla L. Murphy, Sidney M. Chadwick, Patrick Rider, Paul DeVita
Department of Kinesiology, East Carolina University
Introduction
Running is common for exercise and recreational activity; however it is also associated with many injuries. Previous
studies on running have shown that speed has a positive correlation with load: faster running has higher ground
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reaction (GRF), muscle, and joint forces on a per-step basis . Thus reducing stride length and running speed are
interventions used to reduce the risk of running injury. Newer work however has shown that due to using fewer steps,
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total accumulated loads in running can be equal to that in walking over a unit distance . Since fewer steps are needed
per unit distance at faster vs slower running, the following hypothesis can be developed.
Hypothesis
Step length increases with running speed thus reducing the
total number of steps taken per unit distance therefore, one
can hypothesize that running at faster speeds will reduce
total accumulated loads per unit distance.
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Purpose
The purpose of this study was to investigate the effects of
running speed on ground reaction forces and knee joint
forces summed over 1 km of running.
* All means sig diff, p<0.05
Methods
3D motion-capture and force platform data were
obtained on 16 participants (7 males, 9 females;
age 22; mass 65 kg) running at 2.68, 3.35 and
4.46 m/s. Inverse dynamics and a musculoskeletal
model were used to calculate patellofemoral (PF)
force per step. Step length was used to find total
steps per kilometer at each speed. Total
accumulated maximum GRF and PF force were
computed per km as the product of their per step
values and the number of steps per km and
compared across speeds with 1-way ANOVA,
p < 0.05.
Faster running had longer steps
Results
Conclusion
Step length was significantly longer (2.77 v 2.41 v 2.06 m) and
number of steps were significantly lower (372 v 420 v 491) as speed
increased (all p<0.05). Total load per kilometer assessed as summed
maximum GRFs and PF forces were significantly lower at the faster
vs slower speed, p<0.05
Data supported the hypothesis
that as speed increased, total
load was reduced per unit
distance. We suggest that if
running injuries occur due to total
accumulated loads vs peak loads
per step, running at faster speeds
may reduce injury rate.
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References
1. Hamill et al. GRFs at Diff Speeds 1983
2. Miller et al. Per Unit Distance loads 2014
* All means sig diff, p<0.05