Transitioning to minimalist shoes is a popular means for improving running economy amongst runners. However, there are concerns about the potential for minimalist shoes to cause injury.
PURPOSE: To investigate the effect of transitioning to a minimalist shoe on injury incidence in runners.
METHODS: We used a prospective randomized controlled trial design. 61 trained, habitual rearfoot strike runners (age: 27 ? 7 years; body mass index: 23.3 ? 2.1 kg/m2; weekly distance: 26 ? 14 km) were randomly allocated to either a minimalist or control shoe. Runners had no previous experience with minimalist shoes and had no previous (<3 months) injuries. Runners gradually transitioned to their allocated shoe condition (5% weekly increase) over 26 weeks. Time to first injury was the primary outcome of interest. Running related pain intensity was measured weekly using a 100 mm visual analogue scale (VAS) with anchors no pain (0 mm) and worst pain (100 mm). Minimum clinically important difference (MCID) in pain was considered to be 10 mm. The effect of shoe type on injury incidence was analysed using multivariable logistic regression. Body mass (BM) was included as a continuous covariate. The effect of shoe type on pain was analysed using a fixed effects linear model with independent variables shoe and time.
RESULTS: 11/30 runners sustained an injury in the control shoe compared to 16/31 runners in the minimalist shoe. There was no effect of shoe (odds ratio[OR]=2.01, 95% confidence interval [CI] 0.68 to 6.28; p=0.21) or body mass (OR=0.92, 95%CI 0.82 to 1.00; p=0.08) on injury incidence. However, there was a significant shoe*BM interaction effect on injury incidence (OR=1.18, 95%CI 1.04 to 1.36; p<0.05). Runners that weighed one standard deviation (9.1 kg) more than the sample mean BM (74.8 kg) were 4.1 times more likely to get injured running in the minimalist shoe compared to the control shoe. Runners in the minimalist shoe group experienced increased low back (3 mm, 95%CI 1 to 5 mm), knee (6 mm, 95% CI 3 to 9mm), calf (5 mm, 95%CI 1 to 8 mm), shin (3 mm, 95%CI 1 to 5 mm) and ankle (4 mm, 95%CI 1 to 7 mm) pain (p<0.05) but not thigh (0 mm, 95%CI -2 to 2 mm) or foot (1 mm, 95%CI -1 to 3 mm) pain (p>0.38). All differences in pain were less than the MCID.
CONCLUSION: Heavier runners should exercise caution when running in minimalist shoes due to an increased risk of injury.
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