[This is a guest blog by Manuel Joshua Gutierrez-Fernandez. “Manny” has an MS, CSCS, USAT-I, USATF-I,II, USAW-SPC and participated in the summer internship program at Athletic Lab]
Approximately fifty percent of recreational runners will suffer from injury due to distance running. The inability of the lower extremity joints to adequately control the loading during running is often identified as the cause of injury. The most common site of injury is the knee, with patellofemoral pain being the most frequent occurrence. Prevention and treatment of patellofemoral pain regularly focuses on strengthening the hip musculature and the quadriceps’ vastus medialis. Gait retraining is also an important component for reducing and preventing lower extremity dysfunction. A common technique for gait retraining, for the purpose of reducing the magnitude of the loading force on the patellofemoral joint during running, is the altering of step rate and, inversely, step length, with speed kept constant. The compilation of work by a group of researchers from the University of Wisconsin-Madison’s Department of Biomedical Engineering, Department of Mechanical Engineering and Department of Orthopedics and Rehabilitation provides a comprehensive study of the effects of altering step rate and step length.
The research of the University of Wisconsin group builds upon and agrees with past findings regarding step rate intervention. The work has evolved with the advancement of three-dimensional musculoskeletal and computational modeling for dynamic analysis of running and predicting how muscles and joint forces change with step rate. The models are based on the collection 3-D kinematics and kinetics of participants’ running on treadmills at increased step rates 10% above preferred cadence (and decreased step lengths) while maintaining constant speed.
The research confirmed that an increased step rate reduced the impact load on the body. This is due to less vertical center of mass velocity at landing, leading to less energy absorption required by the lower extremity joints, with the greatest effect observed at the knee. The findings showed that as step rate increased, step length was shorter, causing less center of mass vertical excursion and the heel was placed horizontally closer to the center of mass at initial contact, leading to a reduction in braking impulse. A 10% increase in step rate also decreased biomechanical demands experienced by the hip in the frontal and transverse planes of motion (Heiderscheit, 2011).
The research also attempted to determine how altering internal muscle forces and patellofemoral joint loads were affected by step rate. The findings pointed to an increase in step rate substantially diminishing patellofemoral joint loading. The reduction in joint compressive load was primarily due to an altered muscular coordination, placing the knee in a more extended posture during mid-stance. A 10% increase in step rate decreased patellofemoral force magnitude, loading rate and impulse. An additional byproduct of step rate manipulation was a decrease in stance duration (Lenhart, 20142).
Correspondingly, the researchers attempted to characterize the changes caused by a step rate intervention in hip muscle forces and powers during running. The findings provided a unique insight into the demands placed on individual hip muscles during running. The research demonstrated the largest average peak hip muscle force production occurred at the gluteus medius during the loading response of the stance phase. Increasing step rate, shortening step length, increased hamstring and gluteus maximus muscle loading during late swing, reflecting the greater limb decelerations required to position the leg for ground contact. After foot strike, the decreased step length lead to a more erect limb posture, lessening hip muscle force and powers needed in the loading response phase of stance. The increased step rate decreased peak forces from gluteal muscles by approximately 10%, with braking impulse and vertical displacement of the body’s center of mass reduced (Lenhart, 20141).
The latest published research specifically investigated the influence of step rate alteration on patellofemoral contact pressures during running. The research suggested that increasing step rate significantly decreased cartilage contact area and peak and average cartilage contact pressures during mid-stance phase (Lenhart, 2015). The findings are very important in relation to mitigating compressive cartilage stress.
All of the results of the work of this group are relevant to consider in the designing of interventions meant to prevent or treat patellofemoral pain in runners. The step rate intervention can be easily implemented with auditory cues from a metronome or with a GPS watch that measures cadence. The research supports step rate as an effective strategy that can induce notable biomechanical changes in limb loading patterns.
- Heiderscheit, B.C., Chumanov, E.S., Michalski, M.P., Wille, C.M. and Ryan, M.B. (2011). Effects of step rate manipulation on joint mechanics during running. Medicine & Science in Sports & Exercise, 43, 296-302.
- Lenhart, R., Thelen, D., and Heiderscheit, B. (20141). Hip muscle loads during running at various step rates. Journal of Orthopaedic & Sports Physical Therapy, 44, 766-774.
- Lenhart, R.L., Thelen, D.G., Wille, C.A., Chumanov, E.S. and Heiderscheit, B.C. (20142). Increasing running step rate reduces patellofemoral joint forces. Medicine & Science in Sports & Exercise, 46, 557-564.
- Lenhart, R.L., Smith, C.R., Vignos, M.F., Kaiser, J., Heiderscheit, B.C. and Thelen D.G. (2015). Influence of step rate and quadriceps load distribution on patellofemoral cartilage contact pressures during running. Journal of Biomechanics,http://dx.doi.org/10.1016/j.jbiomech.2015.04.036