Stress fractures: it’s not how hard you hit the ground, but how fast you hit it
PainSci summary of Zadpoor 2011 ★★★★☆?4-star ratings are for larger and better studies and reviews published in more prestigious journals, with only quibbles. Ratings are a highly subjective opinion, and subject to revision at any time. If you think this paper has been incorrectly rated, please let me know.
This study of studies — a meta review — tried to figure out if stress fractures are connected to ground reaction forces (the force of your strike) or with loading rates (how fast the force is applied, i.e. more slowly or more jarring). The authors found that the force you are striking with has no connection with stress fractures, but the “the vertical loading rate was found to be significantly different between the two groups.” So, according to this science, it’s not how hard you hit the ground, but how fast you hit it. However, science was also a little unclear on something important: the correlation identified is statistically “significant,” but the size of the correlation is probably not large (impressive numbers would be given in the abstract). So it’s how fast you hit the ground, but probably only to a modest degree. Presumably there are quite a few variables involved, which reduces the importance of even the most seemingly obvious risk factors.
BACKGROUND: Lower-limb stress fracture is one of the most common types of running injuries. There have been several studies focusing on the association between stress fractures and biomechanical factors. In the current study, the ground reaction force and loading rate are examined. There is disagreement in the literature about whether the history of stress fractures is associated with ground reaction forces (either higher or lower than control), or with loading rates.
METHODS: A systematic review of the literature was conducted on the relationship between the history of tibial and/or metatarsal stress fracture and the magnitude of the ground reaction force and loading rate. Fixed-effect meta-analysis techniques were applied to determine whether or not the ground reaction force and/or loading rate are different between the stress fracture and control groups.
FINDINGS: Thirteen articles were identified through a systematic search of the literature. About 54% of these articles reported significantly different vertical ground reaction force and/or loading rate between the stress fracture and control groups. Other studies (~46%) did not observe any significant difference between the two groups. Meta-analysis results showed no significant differences between the ground reaction force of the lower-limb stress fracture and control groups (P>0.05). However, significant differences were observed for the average and instantaneous vertical loading rates (P<0.05).
INTERPRETATION: The currently available data does not support the hypothesis that there is a significant difference between the ground reaction force of subjects experiencing lower-limb stress fracture and control groups. Instead, the vertical loading rate was found to be significantly different between the two groups.
These five articles on PainScience.com cite Zadpoor 2011 as a source:
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- PS Does barefoot running prevent injuries? — A dive into the science so far of barefoot or minimalist “natural” running