Sydney Australia SORI Efficacy of Repetitive Stepping as a Test of Quadriceps Fatigue: Comparison to Isokinetic Exercise Scholes CJ PhD 1,2,3 McDonald MD PhD 2 Coolican MRJ FRACS 1 Parker DA FRACS 1 Parker AW PhD 3 1 Sydney Orthopaedic Research Institute 2 School of Human Movement Studies, Queensland University of Technology 3 Institute of Health & Biomedical Innovation, Queensland University of Technology Australian Orthopaedic Association 70 th Annual Scientific Meeting Adelaide, 2010

Conflict of Interest There is no conflict of interest in this research project There is no conflict of interest in this research project

Quadriceps Function Strength and endurance critical to knee function Strength and endurance critical to knee function Implications of dysfunction following surgery Implications of dysfunction following surgery Quadriceps avoidance (Lewek et al 2002) Quadriceps avoidance (Lewek et al 2002) Joint loading (Shelbourne et al 2004) Joint loading (Shelbourne et al 2004) Functional instability (Hurd et al 2007) Functional instability (Hurd et al 2007) Endurance improves performance of functional activities Endurance improves performance of functional activities

Introduction Dynamometry – ‘gold standard’ Dynamometry – ‘gold standard’ Limitations Limitations Cost (~$100k) Cost (~$100k) Space Space Dedicated specialist personnel Dedicated specialist personnel Need for a clinical alternative Need for a clinical alternative

Aim Validate a functional protocol to induce and quantify quadriceps fatigue compared to isokinetic dynamometry Validate a functional protocol to induce and quantify quadriceps fatigue compared to isokinetic dynamometry

Methods Participants Participants Male undergraduates yrs m kg Repetitive Stepping Repetitive Stepping Additional Weight Step Height Start-end Postures Speed

Methods Dynamometry Dynamometry 50 Repetitions 50 Repetitions Concentric-Eccentric Concentric-Eccentric Range-of-motion 90 0 Range-of-motion 90 0 Speed 60 0 /sec Speed 60 0 /sec

Methods - Fatigue Indicators Peak power Peak power Inverse dynamics Inverse dynamics Integrated torque/time Integrated torque/time

Methods - Fatigue Indicators Surface Electromyography Surface Electromyography Wireless (Zerowire, Italy) Wireless (Zerowire, Italy) VM, VL, RF VM, VL, RF Standardised placement Standardised placement

Methods - Mean Frequency

Results - Peak Power Production

Results - Mean Frequency

Results - Protocol Comparison * * Significant difference between stepping and isokinetic ^ ^Significant difference between muscles

Discussion Stepping induced greater fatigue compared to previous studies (Coventry et al 2006; Bonato et al 2001) Stepping induced greater fatigue compared to previous studies (Coventry et al 2006; Bonato et al 2001) Isokinetic exercise also induced greater fatigue compared to previous studies (Molinari et al 2006) Isokinetic exercise also induced greater fatigue compared to previous studies (Molinari et al 2006) Combined eccentric-concentric action Combined eccentric-concentric action Differential isokinetic fatigue pattern agrees with previous studies (Molinari et al 2006) Differential isokinetic fatigue pattern agrees with previous studies (Molinari et al 2006)

Discussion Lack of studies quantifying fatigue progression in quadriceps during functional task Lack of studies quantifying fatigue progression in quadriceps during functional task Parallel fatigue could be related to joint stability and balance during stepping Parallel fatigue could be related to joint stability and balance during stepping Increased variability in power production Increased variability in power production Load sharing between hip and knee Load sharing between hip and knee

Conclusions Stepping protocol valid method to induce quadriceps fatigue Stepping protocol valid method to induce quadriceps fatigue not as effective as isokinetic exercise not as effective as isokinetic exercise Potential future model for clinic-based fatigue assessment Potential future model for clinic-based fatigue assessment

Future clinical tool Adjustments to the protocol to reduce variability Adjustments to the protocol to reduce variability Validity and reliability for surgically-repaired knees Validity and reliability for surgically-repaired knees Modify protocol for patient populations Modify protocol for patient populations Effects of rehabilitation Effects of rehabilitation Clinical measurements – fatigue indicators Clinical measurements – fatigue indicators Steps to exhaustion Steps to exhaustion Stepping frequency Stepping frequency

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