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Stress fractures: it’s not how hard you hit the ground, but how fast you hit it

updated

Tags: etiology, running, chronic pain, biomechanics, shin pain, plantar fasciitis, patellar pain, foot, pro, exercise, self-treatment, treatment, pain problems, leg, limbs, overuse injury, injury, tendinosis, arthritis, aging, knee

Four articles on PainSci cite Zadpoor 2011: (1) Is Running on Pavement Risky?(2) The Complete Guide to IT Band Syndrome(3) The Complete Guide to Shin Splints(4) Does barefoot running prevent injuries?

PainSci notes on Zadpoor 2011:

This study of studies tries to determine 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). They 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 it’s not how hard you hit the ground, but how fast you hit it. However, the science was murky on something important: the correlation identified is statistically “significant,” but the size of the correlation is not impressive. 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.

original abstract Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

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.

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