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 reaction (GRF), muscle, and joint forces on a per-step basis 1 . 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, total accumulated loads in running can be equal to that in walking over a unit distance 2 . Since fewer steps are needed per unit distance at faster vs slower running, the following hypothesis can be developed.
Hypothesis
Methods
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All means sig diff, p<0.05
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.
* 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.
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.
Results
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
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Faster running had longer steps
Conclusion
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.
References
1. Hamill et al. GRFs at Diff Speeds 1983
2. Miller et al. Per Unit Distance loads 2014
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