I blogged back in July about a study that showed: Increased Lower Limb Loading with use of Minimalist Running Shoes and now we have another related publication:
Short term changes in running mechanics and foot strike pattern following introduction to minimalistic footwear.
Willson JD, Bjorhus JS, Williams B 3rd, Butler RJ, Porcari JP, Kernozek TW.
PM R. 2013 Aug 30
OBJECTIVE: Minimalistic footwear has garnered widespread interest in the running community based largely on the premise that the footwear may reduce certain running-related injury risk factors through adaptations in running mechanics and foot strike pattern. The purpose of this study is to examine short term adaptations in running mechanics among runners who typically run in conventional cushioned heel running shoes as they transition to minimalistic footwear.
DESIGN: 2-week prospective observational study
SETTING: movement science laboratory
PARTICIPANTS: Nineteen female runners with a rear foot strike (RFS) pattern who usually train in conventional running shoes.
METHODS: Participants trained for 20 minutes, three times per week, for two weeks using minimalistic footwear. Three-dimensional lower extremity running mechanics were analyzed before and after this two week period.
MAIN OUTCOME MEASUREMENTS: Hip, knee, and ankle joint kinematics at initial contact, step length, stance time, peak ankle joint moment and joint work, impact peak, vertical ground reaction force loading rate, and foot strike pattern preference were evaluated before and after the intervention.
RESULTS: Knee flexion angle at initial contact increased 3.8° (p < .01), but ankle and hip flexion angle at initial contact did not change after training. No changes in ankle joint kinetics or running temporal-spatial parameters were observed. The majority (71%) of participants demonstrated a RFS pattern while running in minimalistic footwear before the intervention. The proportion of runners with a RFS pattern did not decrease after two weeks (P = .25). Those runners who chose a RFS pattern in minimalistic shoes experienced a vertical loading rate that was 3 times greater than those who chose to run with a non-RFS pattern.
CONCLUSIONS: Few systematic changes in running mechanics were observed among participants following 2 weeks of training in minimalistic footwear. The majority of participants continued to utilize a RFS pattern following training in minimalistic footwear, and these participants experienced higher vertical loading rates. Continued exposure to these greater loading rates may have detrimental effects over time.
This pretty much showed the same thing as the previous publication, in that transitioning to minimalist shoes does not mean that you automatically change from a heel or rearfoot strike pattern to a forefoot or midfoot strike pattern and that the vertical impact loads increase in the short term. Of most interest was the finding of a 3 fold increase in the vertical loading rate in those who chose to run with a rearfoot strike pattern in the minimalist shoes.
As always, I go where the evidence takes me until convinced otherwise, and as I said about the previous study: this study shows that when first using minimalist shoes, impact forces increase. It probably also says that the running form or technique must also be addressed at the same time as going to minimalist running shoes, assuming that there are good reasons for doing so.
Willson JD, Bjorhus JS, Williams B 3rd, Butler RJ, Porcari JP, & Kernozek TW (2013). Short term changes in running mechanics and foot strike pattern following introduction to minimalistic footwear. PM & R : the journal of injury, function, and rehabilitation PMID: 23999160