One of the potential shortcomings of kinematic, kinetic and metabolic studies of barefoot or minimalist running versus traditional shod running is that acute interventions are often used, rather than a prolonged period of habituation to the different conditions under study. It is not known if what is found in these acute intervention studies will still have the same findings after neuromotor adaptation has taken place to different running forms over a period of time. A new study published last week in the International Journal of Sports Medicine set out to look at those kinematic changes after 12 weeks of a controlled transition program to minimalist running:
12 Weeks of Simulated Barefoot Running Changes Foot-Strike Patterns in Female Runners.
McCarthy C, Fleming N, Donne B, Blanksby B.
Int J Sports Med. 2013 Sep 18.
To investigate the effect of a transition program of simulated barefoot running (SBR) on running kinematics and foot-strike patterns, female recreational athletes (n=9, age 29±3 yrs) without SBR experience gradually increased running distance in Vibram FiveFingers SBR footwear over 12 weeks. Matched controls (n=10, age 30±4 yrs) continued running in standard footwear. A 3-D motion analysis of treadmill running at 12 km/h-1 was performed by both groups, barefoot and shod, pre- and post-intervention. Post-intervention data indicated a more-forefoot strike pattern in the SBR group compared to controls; both running barefoot (P>0.05), and shod (P<0.001). When assessed barefoot, there were significant kinematic differences across time in the SBR group for ankle flexion angle at toe-off (P<0.01). When assessed shod, significant kinematic changes occurred across time, for ankle flexion angles at foot-strike (P<0.001) and toe-off (P<0.01), and for range of motion (ROM) in the absorptive phase of stance (P<0.01). A knee effect was recorded in the SBR group for flexion ROM in the absorptive phase of stance (P<0.05). No significant changes occurred in controls. Therefore, a 12-week transition program in SBR could assist athletes seeking a more-forefoot strike pattern and “barefoot” kinematics, regardless of preferred footwear.
Basically they took 30 female runners, randomized them to a control group that kept running in their traditional shoes or to a group that was transitioned to Vibram FiveFingers over a 12 week period. They looked at number of kinematic variables in each condition while running on a treadmill. The main findings on barefoot kinematics at baseline were consistent with all the previous studies:
- shorter ground contact time
- more of a midfoot and forefoot strike pattern
- more plantarflexed ankle at foot strike
- lower peak knee flexion
- lower knee range of motion
After the 12 week intervention the only further change in these differences was greater ankle plantarflexion at toe-off. This means that there are differences between the ‘acute intervention’ of barefoot/minimalist running vs a 12 week period of adaptation, but this was the only variable that they found a difference in. So they concluded that changes in the motor pattern can be made in the 12 week period used for the study:
The findings of this study indicate that changes in motor patterns in previously habitually shod runners are possible and can be accomplished within 12 weeks
There are a number of shortcomings of the study and contexts that the results need to be interpreted in:
- the data was collected on a treadmill, so this may or may not be an issue, depending on how close you want to believe that treadmill running mimics overground running.
- it was a study on kinematics and not kinetics. Kinematics is all about the motion. Kinetics is about the forces driving those motions and it is the loads associated with kinetics that are responsible for injury risk, so we do not know from this study what happened to the kinetics (ie loads in the tissues).
- almost a third of the original participants dropped out of the study which is unusually high. Dropouts happen in studies, but not normally this many. However, the characteristics of the dropouts were similar in each group, so its not necessarily an issue.
- Those fan boys who objected to the results of the bone stress study in those wearing Vibrams on the grounds that the 12 weeks was not long enough will of course be objecting to the results of this study on the same grounds (even though it was exactly what Vibram were recommending).
- this was NOT a study on which of the two (minimalist vs traditional shod) was better than the other. It was just describing the differences after the 12 week transition.
While I have no problem with the conclusion of the study, I do have a problem with some of the unsubstantiated broad statements made by the authors, such as:
There is emerging evidence that a FFS [forefoot strike] pattern such as developed over time by SBR [simulated barefoot running] could have performance benefits [ 16 , 17 , 24 ] and perhaps lead to lower injury rates [ 8 , 13 ]
References 16 and 17 had nothing to do with performance or economy! Reference 24 was cherry picked to make a point, when the preponderance of studies are showing that this is NOT the case. References 8 and 13 on injury rates are really another poor example of cherry picking at its worse. The preponderance of evidence says the opposite, so the authors cherry picked two studies to support their point. They ignored all the other studies that contradicted their point. This shoddy poor use of references should not happen in an academic publication (my students would have been severely marked down for this if they did this in an essay). The editor and reviewers should not have let this through.
As always, I go where the evidence takes me until convinced otherwise, and this study tells us that neuromotor adaptation to minimalist running can occur over a 12 week period. Its just a shame that the paper gets ruined by their cherry picking, misinterpreting, misquoting and misuse of references.
McCarthy C, Fleming N, Donne B, & Blanksby B (2013). 12 Weeks of Simulated Barefoot Running Changes Foot-Strike Patterns in Female Runners. International journal of sports medicine PMID: 24048910