Running Form Modification: When Self-selected is Not Preferred Bryan Heiderscheit, PT, PhD Department of Orthopedics and Rehabilitation Department of Biomedical Engineering University of Wisconsin-Madison
Where is the Knee Pain? 9.4 min/mile pace 172 steps/min 180 steps/min
Outline Determinants of step frequency/length Biomechanical effects of forced change in step frequency Evidence for application of step frequency change in treating runners with anterior knee pain
Step Frequency Determinants Optimized for metabolic cost minimize muscle activity External factors: Velocity Grade Footwear Surface properties Internal factors: Anthropometry Developmental status Muscle fiber composition Fatigue Injury history Cavanagh and Kram (1989) Med Sci Sports Exerc Cavanagh and Williams (1982) Med Sci Sports Exerc
Stride Frequency and O 2 Uptake Most runners naturally choose a stride length frequency combination that minimizes metabolic cost Accomplished through adjustment of leg stiffness so that optimal muscle activation is achieved Cavanagh and Williams (1982) Med Sci Sports Exerc
COM Vertical Displacement and Step Frequency Increased step frequency: Decreased contact time Decreased COM vertical displacement Slight decrease in vertical GRF Morin et al. (2007) J Biomechanics
COM Vertical Displacement and Step Frequency COM Dis splacement (cm) 12 10 8 6 4 Non-trained Well Trained Highly Trained 2.5 2.7 2.9 3.1 3.3 3.5 3.7 Step Frequency (Hz) 150 186 222 (steps/min) Increased step frequency reduces vertical displacement of COM r=-0.81 Step frequency appears to increase with training experience Similar running speed across subjects Slawinski et al. (2005) Med Sci Sports Exerc
Step Frequency and Leg Stiffness Leg stiffness increases with step frequency Minimal change if ±10% PSF Morin et al. (2007) J Biomechanics Farley and Gonzalez (1996) J Biomechanics
Metabolic Cost vs Tissue Stress Forcing a shift away from preferred may be necessary under some circumstances Cavanagh (1987) Foot Ankle Metabolic cost Local tissue stress/strain Injury Recovery and Prevention Tissue protection Load distribution
Stride Frequency and Tibial Accelerations Decreased tibial accelerations with increased stride frequency Constant speed Clarke et al. (1995) J Sports Sci More vertical leg posture at initial contact PSF +10% -10% Farley and Gonzalez (1996) J Biomechanics
Location of Injury Achilles/Calf 6.4% Hip/Pelvis 10.9% Lower Leg 12.8% Other 10.8% Foot/ankle 16.9% Knee 42.1% 5 most common injuries Patellofemoral pain syndrome Iliotibial band friction syndrome Plantar fasciitis Tibial stress fracture Knee meniscal injuries Taunton et al. (2002) Br J Sports Med
Running-related Injuries Potential benefits of increased step frequency: 1. Decrease horizontal distance of footground contact from COM Reduce braking impulse Reduce knee extensor moment 2. Increase lower extremity stiffness Reduce vertical excursion of COM Increase muscle pre-activation
Step Frequency and Joint Mechanics 50 healthy runners > 15 miles/week Run at self-selected speed constant across conditions 5 step frequencies: Preferred (PSF) PSF ± 5% PSF ± 10% Paced by metronome
Step Frequency Manipulation Preferred (160 steps/min) Preferred + 5% (168 steps/min) Preferred + 10% (176 steps/min)
COM and Forces 1.3 1.2 % PS SF 1.1 1 0.9 0.8 0.7-10 -5 PSF +5 +10 Step Frequency (% PSF) COM vertical displacement COM-heel distance GRF - braking impulse GRF - peak vertical
Knee Angle and Moment Knee Flexion Angle (deg) 60 50 40 30 20 10 0-10 -5 PSF +5 +10 Step Frequency (% PSF) 1.3 1.2 1.1 1 0.9 0.8 0.7 Knee Ex xt Moment (% %PSF) midstance Knee Flexion -IC Knee Flexion - Peak initial contact Knee Extension Moment
PSF (162) with knee pain Clinical Application Runners with anterior knee pain Trial treatment of cadence manipulation 5-10% increase in step frequency using metronome on treadmill 1-2 min period of adjustment 50+% decrease reported in symptoms during session Follow-up indicates immediate symptom improvement/resolution 172 without knee pain
Utilization of Step Frequency Manipulation Temporary form change to maintain mileage Reduce load to knee joint Strategy to promote muscle activation prior to loading mechanism to facilitate carryover of strength gains into running Consider as more permanent change to running form better to understride [length] than overstride especially in beginning runners Elliott and Blanksby (1979) Br J Sports Med
Step Frequency and Anthropometrics Anthropometrics should not be used to determine the appropriateness of a person s step length/frequency Anthropometrics are not strongly associated with step length tall or long legged runners do not necessarily have a longer stride length runners with thinner legs do not have a longer stride length Cavanagh and Kram (1989) Med Sci Sports Exerc 180 steps/min suggested as optimum for performance 145-160 steps/min is common in recreational runners Requires trial-and-error approach Fast and simple
Evidence for Training Carryover Reduce impacts by using impact as feedback 8 training sessions over 2wks new running form maintained at 4wk follow-up with no intermediate training Crowell and Davis (2006) Proceedings, Am Society Biomechanics
Metabolic Cost of Step Frequency Change 8% shift from preferred stride frequency (PSF) increased O 2 uptake by 3 ml/kg/min Hunter et al. (2007) Eur J Appl Physiol Moderate deviations in stride length had minimal effects on O 2 uptake Cavanagh and Williams (1982) Med Sci Sports Exerc
Other Potential Applications Increase step frequency: Iliotibial band syndrome Reduce knee flexion excursion Plantar heel pain Reduce foot-ground angle at initial contact Anterior compartment Reduce eccentric demand on tibialis anterior
Comprehensive Treatment Step frequency change part of treatment plan Additional interventions included as needed to target impairments strengthening and stretching
Summary Increasing step frequency reduces knee joint loading during running Preliminary evidence of symptom reduction by increasing step frequency in runners with anterior knee pain Running form modification should be considered as an adjunct to current interventions injury prevention or recovery
Acknowledgements Graduate Students Liz Chumanov, PhD Max Michalski, MS Kerry Finnegan, BS Christa Wille APTA Sports Physical Therapy Section Private Practice Section Orthopaedic Section
Thank You University of Wisconsin, Madison, WI
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