SLR - September 2014 - Rico M. A. Visperas

Joint Kinetics in Rearfoot Versus Forefoot Running: Implications of Switching Technique

Reference: Stearne SM, Alderson JA, Green BA, Donnelly, Cyril J, Rubenson J. Joint Kinetics in Rearfoot Versus Forefoot Running: Implications of Switching Technique. Medicine & Science in Sports Medicine and Exercise, 2014 Aug (8):1578-87.

Scientific Literature Review

Reviewed By: Rico M. A. Visperas, DPM
Residency Program: Englewood Hospital & Medical Center

Podiatric Relevance: With an increasing rate of patients seeking more active lifestyles, the foot and ankle surgeon should be well versed in understanding the biomechanics of running as it pertains to joint load, mechanical load, and injury rates. In addition, it is important to be aware of the various gait patterns and how they may affect the ankle joint. This knowledge will allow the practitioner to develop a problem-focused treatment plan in order for the athlete to resume their preferred training regimen.

Methods: Sixteen trained competitive male distance runners were recruited, eight of which who were habitual Rearfoot Strike runners and eight habitual Forefoot Strike runners. Midfoot Strike runners were excluded due to their variability in kinetic profiles. A high-speed video recording at 100 Hz positioned in the sagittal plane was used for analysis. Rearfoot Strike and Forefoot Strike patients exhibited no significant differences in the age, height or weight. Participants also did not experience lower limb injuries six months prior to testing and were without preexisting gait abnormalities.

A force-plate instrumented treadmill was used to conduct the analysis of the foot strike pattern. Subjects commenced the study period with a five minute warm-up followed by a resting phase to return their Heart Rates within 10 percent of resting value prior to measurement trials. Two running trials at a speed of 4.5 meters per second were completed at two-minute intervals in the following fashion: 1) Habitual foot strike technique (Rearfoot vs. Forefoot Strike) and 2) Imposed technique. All subjects were provided with the same lightweight footwear (Nike Lunaracer)

Via 3D segment motion and eight-camera near-infrared motion capture systems, joint kinematic and kinetic data was collected and computed for the ankle, knee, and hip. Thirty-four retro reflective markers attached to each subject’s pelvis, lower limbs, and shoes were used to collect segment kinematics. Ground reactive forces from the treadmill were captured at 2000 Hz and synchronized with the kinematic data via a Vicon MX-Net Control box. Ankle joint centers were defined as the midpoint between the medial and lateral malleoli and a six-marker pointer was used to for the lateral and medial femoral condyles. The calcaneal inversion/eversion and foot abduction/adduction was contained through use of a custom foot alignment rig.

Hip, knee, and ankle joint moments were tabulated along with peak positive and negative powers along the sagittal, frontal, and transverse planes. In addition, positive and negative work at each joint was assessed separately from the stance and swing phases.

Through various statistical techniques such as MANOVA, five strides for each subject from each trial period were selected for analysis.  
    
Results: Spatial-temporal gait parameters-Habitual Rearfoot Strike participants were on average greater in stride and stance time while generally having smaller stride frequencies. Swing times were similar between both groups. Forefoot strike runners when switched to an imposed Rearfoot strike, showed statistical difference with an increase in stride time.

Effect of habitual and imposed foot strike technique on peak joint moments and instantaneous power-Peak plantar flexion was greater in habitual and imposed Forefoot strike subjects. Ankle internal rotation moments did not differ amongst habitual Rearfoot and forefoot strike runners but increased significantly between Rearfoot Strike runners and imposed forefoot strike running. In regards to Peak instantaneous ankle power absorption, habitual Forefoot strike runners were greater versus habitual Rearfoot Strike subjects. In addition, results increased when habitual Rearfoot Strike Runners were switched to an imposed Forefoot strike and decreased when habitual Forefoot Strike runners were altered to an imposed Rearfoot Strike. In regards to the knee joint, when habitual Forefoot Strike Runners were switched to an imposed Rearfoot strike, knee extension moment increased by 29 percent and knee abduction moments were found to be smaller in habitual Forefoot Strike runners versus habitual Rearfoot Strike runners. Peak power absorption at the knee joint was greater in all Rearfoot Strike Conditions. No significant difference was found between the two groups at the hip joint.

Effect of habitual and imposed foot strike techniques on work, average power, and average moment rate at the ankle knee, and hip joints during stance- Multivariate analysis revealed significant interaction effects amongst each group. However, it was found that there was no significant main effect of foot strike or condition present in work, average power, average moment rate, or percentage contribution of each joint to total work and average power.
 
Effect of habitual and imposed foot strike techniques on total lower limb work and average power-Significant increase in total limb positive average power was found when habitual Rearfoot Strike runners switched to an imposed Forefoot Strike running style. In addition, there was a decrease in the total lower limb positive average power when habitual Forefoot Strike runners alternated for an imposed Rearfoot Strike. Total negative power average increased when habitual Rearfoot runners switched to an imposed Forefoot Strike.

Discussion: Forefoot Strike running has been found to be more prevalent among elite athletes. This has led to those recreational and high-level athletes to adopt a Forefoot running style even though they may have an inherent Rearfoot Strike running pattern. Further, previous studies exhibit that Forefoot Strike running may reduce injury rates.

The difference between habitual running technique joint mechanics-Habitual Rearfoot Strike and Forefoot Strike runners did not differ in total lower limb mechanical work or average power. No metabolic difference exists between Rearfoot Strike and Forefoot Strike. Habitual Rearfoot Strike runners place more demand on the knee joint along the sagittal and frontal planes while habitual Forefoot Strike runners experience more demand along the ankle joint in the sagittal plane. Therefore, Forefoot Strike runners are at a higher risk of ankle-related injuries such as Achilles ruptures. Forefoot Strike runners may also face cumulative overload injury to their ankle joint.

The effect of switching: Rearfoot Strike to Forefoot Strike-Habitual Rearfoot Strike runners when switched to forefoot strike, replicated sagittal plane mechanics during habitual Forefoot strike running. Imposed Forefoot strike lead to increase in variables by 33 percent of ankle internal rotation moments. Imposed Forefoot Strike increased mechanical cost by 17 percent due to increase of power primarily at hip and ankle joints and symptomatically presented as calf fatigue and delayed onset muscle soreness

The effect of switching: Forefoot Strike to Rearfoot Strike-When habitual Forefoot Strike runners were analyzed to adopt Rearfoot Strike running, it was found that they were able to replicate all of the joint motions of habitual Rearfoot strike runners with the exception of an increase in frontal plane knee loads. In addition, these subjects used 10 percent less power when switching from Forefoot to Rearfoot Strike. This might suggest that habitual Forefoot Strike athletes can use the imposed Rearfoot Strike when rehabilitating injuries to their Achilles tendon or reduce loads during activity.

Conclusion: No clear mechanical advantage was found of habitual Forefoot Strike Running over Habitual Rearfoot Strike Running. Alternating habitual running styles may have serious injury implications and overall performance for various joint and muscle groups. Forefoot Strike running requires more metabolic energy therefore, habitual Rearfoot Strike athletes should caution against adopting a Forefoot Strike pattern. In addition, habitual Forefoot Strike runners are able to produce similar joint dynamics of habitual Rearfoot Strike without replicating the high knee abduction moments while lowering positive average limb power. This finding may aid habitual Forefoot Strike athletes to adopt the Rearfoot Strike pattern when recovering from injury. The results of this study challenge the strategy of athletes switching from a Rearfoot to Forefoot Strike. 

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