Tibial Accelerations in Heel and Forefoot Strikers

Many studies have now compared the biomechanics of forefoot/midfoot striking vs rearfoot strike patterns when running and some of those have looked at tibial loads with most studies showing its the usual six of one, half a dozen of the other as it was a matter of trading impact loads on the tibia (higher in heel strikers) versus bending moments (higher in forefoot strikers). For more see: Tibial strain and barefoot running and Barefoot vs shod running: Effects on tibia loads. Now we have this new study being presented at the iFab meeting in Korea this week:

Rearfoot strikers have smaller resultant tibial accelerations at foot contact than non-rearfoot strikers
Molly D Glauberman and Peter R Cavanagh
Journal of Foot and Ankle Research 2014, 7(Suppl 1):A93 doi:10.1186/1757-1146-7-S1-A93
Purpose
Overuse injuries are common in recreational runners. Recent reports have implicated the characteristics of the footstrike in the etiology of stress responses in the tibia. This has motivated efforts to modify the loading at footstrike by altering the orientation of the foot at first contact. The present study aimed to: 1) report typical magnitudes of resultant tibial acceleration (TA) in women distance runners; 2) contrast TA in rearfoot and non-rearfoot striking runners; and 3) examine TA during non-natural footstrike patterns in runners.
Method
We used a leg-mounted tri-axial acceleration monitoring unit to measure TA and angular velocities. Twenty injury-free women distance runners (age 27.8±3.7 years, height 168.1±6.2 cm, body mass 59.2±7.3 kg, weekly mileage >20) participated in the study. The sensor was positioned 5cm above the medial malleolus along the medial tibial border and tensioned to 22N with a Velcro strap. Multiple 60-second running trials at 3.13 m/s on a force-measuring treadmill (Kistler 9287 plate) were collected.
Results
The range of values for axial peak tibial acceleration (PTA) in the group was 4.6g to 10.9g. Axial PTA in 7 non-rearfoot strikers (6.3±1.1g) was not significantly different from that in rearfoot strikers (7.4± 0.8g; p=0.15). However, the anterior-posterior acceleration component and the resultant PTA in non-rearfoot strikers (10.0±1.9g) were significantly greater than that in rearfoot strikers (5.2±1.6g; p=<0.001) (Figure 1). In a second part of the study, twelve natural rearfoot runners were instructed to change their strike pattern to a non-rearfoot strike while 6 non-rearfoot strikers changed to a rearfoot pattern. The average resultant PTA for the natural rearfoot strikers increased from 9.4g to 11.3g, whereas 6 natural non-rearfoot strikers decreased to 9.5g from 13.2g when switching to rearfoot striking.
Conclusions
It is not advantageous for rearfoot strikers to transition to non-rearfoot striking if PTA is the criterion measure. Previous studies that have only examined the axial component of tibial acceleration may have reached the wrong conclusion because the A-P component is the larger component in non-rearfoot strikers. Our findings suggest that a transition away from rearfoot striking is likely to increase tibial acceleration at footstrike. Thus, if tibial stress injuries are indeed related to resultant tibial acceleration at footstrike, a change to non-rearfoot striking may increase the risk of injury

I have no more information on this study than what is in the abstract, but nothing jumps out at me as being an issue with the methods or the analysis. The conclusion was clear:

It is not advantageous for rearfoot strikers to transition to non-rearfoot striking if PTA is the criterion measure.

ie forefoot striking had higher loads in the tibia compared to rearfoot striking. Why is that important? It is important as tibial accelerations needs to be slowed down by muscular effort. If that effort is greater, then there is greater potential for injury due to higher tissue loads.

As always, I go where the evidence takes me until convinced otherwise.

Glauberman, M., & Cavanagh, P. (2014). Rearfoot strikers have smaller resultant tibial accelerations at foot contact than non-rearfoot strikers Journal of Foot and Ankle Research, 7 (Suppl 1) DOI: 10.1186/1757-1146-7-S1-A93

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2 Responses to Tibial Accelerations in Heel and Forefoot Strikers

  1. Dave Smith April 9, 2014 at 7:03 am #

    Hi Craig
    You say tibial accelertions need to be slowed by muscular effort and therefore high accelerations in non rearfoot strike = higher muscular effort = higher potential for injury.

    But since the acceleration of interest is negative, ie deceleration of the tibia, then there may not be increased muscular effort.

    So the forefoot striking requires that the rearfoot comes to the ground in an arc that effectively moves the tibia in the opposite direction to line if progression.

    My thought is that the less muscular effort from GSC will result in greater negative acceleration if the tibia.

    Whereas with rearfoot strike the rocker action of the heel allows tibial velocity in the line of progression to continue less inhibited ie less deceleration. But to keep the heel rocker effective requires the ant tib muscle to work hard to dorsilflex the ankle and so there may be increased muscle effort to achieve less tibial acceleration

    These are my first thoughts so please feel free to slay me in your reply 🙂

    • Craig Payne April 9, 2014 at 7:06 am #

      Thanks Dave; my choice of words may not be the most appropriate here! I would prefer until this is published in full. I some friends at the iFab conference (I could not make it this yr) and they following up with the authors.

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