Hot on the heels of the study from last week on Barefoot vs Shod and patellofemoral joint stresses which showed that running barefoot reduced patellofemoral stress by 12%, we now have another new study that looked at patellofemoral loads and cadence:
Increasing Running Step Rate Reduces Patellofemoral Joint Forces
Lenhart, Rachel L.; Thelen, Darryl G.; Wille, Christa M.; Chumanov, Elizabeth S.; Heiderscheit, Bryan C.
Medicine & Science in Sports & Exercise: 2 August 2013
Purpose: Increasing step rate has been shown to elicit changes in joint kinematics and kinetics during running, and has been suggested as a possible rehabilitation strategy for runners with patellofemoral pain. The purpose of this study was to determine how altering step rate affects internal muscle forces and patellofemoral joint loads, and then to determine what kinematic and kinetic factors best predict changes in joint loading.
Methods: We recorded whole body kinematics of 30 healthy adults running on an instrumented treadmill at three step rate conditions (90%, 100%, and 110% of preferred step rate). We then used a 3D lower extremity musculoskeletal model to estimate muscle, patellar tendon, and patellofemoral joint forces throughout the running gait cycles. Additionally, linear regression analysis allowed us to ascertain the relative influence of limb posture and external loads on patellofemoral joint force.
Results: Increasing step rate to 110% of preferred reduced peak patellofemoral joint force by 14%. Peak muscle forces were also altered as a result of the increased step rate with hip, knee and ankle extensor forces, and hip abductor forces all reduced in mid-stance. Compared to the 90% step rate condition, there was a concomitant increase in peak rectus femoris and hamstring loads during early and late swing, respectively, at higher step rates. Peak stance phase knee flexion decreased with increasing step rate, and was found to be the most important predictor of the reduction in patellofemoral joint loading.
Conclusion: Increasing step rate is an effective strategy to reduce patellofemoral joint forces and could be effective in modulating biomechanical factors that can contribute to patellofemoral pain.
This study showed that there was a 14% decrease in peak patellofemoral joint forces when step rate increased to 110% of the participants preferred step rate. They also showed that the decrease in the stance phase knee flexion with the increased cadence was the main predictor of the decrease in load of the patellofemoral load, which is also what was suggested as the reason in the other recent study on barefoot vs shod running.
My main criticism of previous similar studies is that the authors report the decrease in load somewhere, but do not report where it went or where there was an increase. You can not decrease the load in one tissue with increasing it in another. This study did report where there was increase. They found an increase in rectus femoris and hamstring loads. This means to increase the cadence to 110% of preferred rate to decrease the peak patellofemoral load, you increase the load in other muscles. In practical terms, this is going to mean trade offs.
A couple of riders on this study:
- it was a lab based study on healthy people and was not a clinical trial on patellofemoral pain syndrome
- the study reported a decrease of 14% in peak loads, but with the increase in cadence more steps are being taken, so it does not show if the actual cumulative load in the joint is going to be decreased, which is why we need a clinical trail on patellofemoral pain syndrome to test this.
As always, I go where the evidence takes me until convinced otherwise, and this is more pretty good circumstantial evidence that we need to be looking at gait changes in those with patellofemoral pain syndrome. Just how much this should be implemented into clinical practice in the absence of an actual clinical trial is still open to debate.
Lenhart RL, Thelen DG, Wille CM, Chumanov ES, & Heiderscheit BC (2013). Increasing Running Step Rate Reduces Patellofemoral Joint Forces. Medicine and science in sports and exercise PMID: 23917470