Running Form Modification: When Self-selected is Not Preferred

Transcription

1 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

2 Where is the Knee Pain? 9.4 min/mile pace 172 steps/min 180 steps/min

3 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

4 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

5 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

6 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

7 COM Vertical Displacement and Step Frequency COM Dis splacement (cm) Non-trained Well Trained Highly Trained Step Frequency (Hz) (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

8 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

9 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

10 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

11 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

12 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

13 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

14 Step Frequency Manipulation Preferred (160 steps/min) Preferred + 5% (168 steps/min) Preferred + 10% (176 steps/min)

15 COM and Forces % PS SF PSF Step Frequency (% PSF) COM vertical displacement COM-heel distance GRF - braking impulse GRF - peak vertical

16 Knee Angle and Moment Knee Flexion Angle (deg) PSF Step Frequency (% PSF) Knee Ex xt Moment (% %PSF) midstance Knee Flexion -IC Knee Flexion - Peak initial contact Knee Extension Moment

17 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

18 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

19 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 steps/min is common in recreational runners Requires trial-and-error approach Fast and simple

20 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

21 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

22 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

23 Comprehensive Treatment Step frequency change part of treatment plan Additional interventions included as needed to target impairments strengthening and stretching

24 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

25 Acknowledgements Graduate Students Liz Chumanov, PhD Max Michalski, MS Kerry Finnegan, BS Christa Wille APTA Sports Physical Therapy Section Private Practice Section Orthopaedic Section

26 Thank You University of Wisconsin, Madison, WI

27 References 1. Cavanagh, P.R., and R. Kram. Stride length in distance running: velocity, body dimensions, and added mass effects. Med.Sci.Sports Exerc. 21:467, Cavanagh, P.R., and K.R. Williams. The effect of stride length variation on oxygen uptake during distance running. Med Sci Sports Exerc. 14:30-35, Morin, J.B., P. Samozino, K. Zameziati, and A. Belli. Effects of altered stride frequency and contact time on leg-spring behavior in human running. J Biomech. 40: , Slawinski, J.S., and V.L. Billat. Difference in mechanical and energy cost between highly, well, and nontrained runners. Med Sci Sports Exerc. 36: , Farley, C.T., and O. Gonzalez. Leg stiffness and stride frequency in human running. J.Biomech. 29:181, Cavanagh, P.R. The biomechanics of lower extremity action in distance running. Foot Ankle. 7:197, Clarke, T.E., L.B. Cooper, C.L. Hamill, and D.E. Clark. The effect of varied stride rate upon shank deceleration in running. J Sports Sci. 3:41-49, Taunton, J.E., M.B. Ryan, D.B. Clement, D.C. McKenzie, D.R. Lloyd-Smith, and B.D. Zumbo. A retrospective case-control analysis of 2002 running injuries. Br J Sports Med. 36:95-101, Elliott, B.C., and B.A. Blanksby. Optimal stride length considerations for male and female recreational runners. Br J Sports Med. 13:15-18, Hunter, I., and G.A. Smith. Preferred and optimal stride frequency, stiffness and economy: changes with fatigue during a 1-h high-intensity run. Eur.J.Appl.Physiol. 100:653, Crowell, H.P., and I. Davis. Reducing lower extremity loads through gait retraining using real-time feedback methods. In Proceedings of the Am Society Biomechanics. Blacksburg, VA, 2006.