Each year up to 70% of runners experience a musculoskeletal injury. Approximately 50% of all injuries involve the knee joint and patellofemoral pain (PFP) is the most common injury. Increased patellofemoral joint stress (PFJS) may be associated with the aetiology or exacerbation of pain and symptoms. It has been hypothesised that running technique modifications may have a beneficial effect on lower limb biomechanics. The running techniques that could potentially decrease PFJS are (1) forefoot landing, (2) step rate increase by 10%, and (3) forward trunk lean. However, a comparison of PFJS during these three techniques within a single cohort has not yet been measured. The purpose of this study was to quantify lower limb kinetics, including PFJS, across these 3 conditions as compared to a runner’s typical rearfoot strike pattern.
Methods Nine healthy runners (24.71 ± 8.18 km/week, 3.33 ± 3.03 years running experience) completed four running trials at their comfortable speed (2.88 ± 0.25 m/s) in a randomised order. Kinetic (Bertec instrumented treadmill) and kinematic (7-camera Vicon motion-capture system) data were collected and measures of hip, knee and ankle joint moments and PFJS were calculated using a previously described model1,2. The average of 10 trials during the stance phase of each condition were analysed. A repeated measures ANOVA was used for analysis (alpha = 0.05).
Results Compared to the typical rearfoot strike condition, the forefoot landing revealed a significant 36.54% reduction in PFJS (p = 0.04) (Figure 1). PFJS was also reduced by 17.73% (p = 0.39) during the step rate increase condition and decreased by 13.60% (p = 0.90) with a forward trunk lean as compared to the rearfoot strike condition but did not reach statistical significance. Additionally, the forefoot landing condition resulted in a significantly greater plantarflexion moment (p < 0.01) and reduced knee extensor moment (p = 0.02) as compared to the rearfoot strike condition. During the step rate increase condition no change in the knee extensor moment (p = 1.00) was measured despite significantly reduced (p < 0.01) knee flexion angle compared to the rearfoot strike condition. Finally, the forward trunk lean significantly (p < 0.01) increased the hip extensor moment but had no effect on PFJS (p = 0.90) or the knee extensor moment (p = 1.00) as compared to the rearfoot strike condition.
Discussion A forefoot landing, a step rate increase, and a forward trunk lean resulted in reduced PFJS in healthy runners. The techniques had differential effects on other joint kinematic and kinetic measures. Although the forefoot landing showed greater potential to reduce PFJS, and could be recommended for PFP prevention and treatment, the other techniques may also be clinically relevant considering the number of steps incurred by runners during training and competition. Future analysis involving a larger sample and those with PFP are needed to confirm these results.
Acknowledgment Project supported by Fapesp [Project number: 2015/20306-2].
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Ho KY, Blanchette MG, Powers CM. The influence of heel height on patellofemoral joint kinetics during walking. Gait and Posture 2012 Jun:36:271–275.
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