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'The influence of muscular activation profiles on lower limb biomechanics during a sport-specific landing task' (ISBS 2015 - Aaron Fox)
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- 6. ± ± ±
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- 11. = 𝑖=1 𝑛 𝑃𝑃1𝑖 − 𝑃𝑃1 𝑖.𝑗 … 𝑃𝑃𝑧𝑖 − 𝑃𝑃𝑧 𝑖,𝑗 𝑖=1 𝑛 𝑃𝑃1𝑖 − 𝑃𝑃1 𝑖,𝑗 2 … 𝑃𝑃𝑧𝑖 − 𝑃𝑃𝑧 𝑖.𝑗 2 𝑐𝑜𝑟𝑟𝑀𝑎𝑡 𝑖,𝑗
- 12. • •
- 13. NormalisedEMG(%MVC)NormalisedEMG(%MVC)NormalisedEMG(%MVC) LATERAL HAMSTRINGS RECTUS FEMORIS VASTUS LATERALIS VASTUS MEDIALIS GASTROCNEMIUS Time Relative to IC (ms) Time Relative to IC (ms) MAP-1 MAP-2 MAP-3 GLUTEUS MAXIMUS GLUTEUS MEDIUS MEDIAL HAMSTRINGS
- 15. ↓↑ HIP FLEX (+) / EXT (-) HIP ADD (+) / ABD (-) HIP IR (+) / ER (-) KNEE FLEX (-) KNEE ADD (+) / ABD (-) KNEE IR (+) / ER (-) JointAngle(o)JointAngle(o) Time Post IC (ms) Time Post IC (ms) Time Post IC (ms) MAP-1 MAP-2 MAP-3
- 16. HIP FLEX (-) Moment HIP ADD (-) Moment HIP ER (+) Moment KNEE FLEX (+) Moment KNEE ABD (+) Moment KNEE ER (+) Moment JointMoment(Nm.kgm-1)JointMoment(Nm.kgm-1) Time Post IC (ms) Time Post IC (ms) Time Post IC (ms) MAP-1 MAP-2 MAP-3 ↓ ↑
- 17. ↓↑ ↑
Editor's Notes
- ACL injuries are bad Lengthy, 8 months sporting absence Increased risk of OA High number of noncontact, and potentially preventable Females
- Netball is considered one of the high-risk ACL sports; injury reputation Team based court sport High impact landings, deceleration, cutting Ankle frequent, but knee serious
- Common theme = one off phenomenon Injured during activity replicated countless times Why do these occur? No contact or perturbation > NM dysfunction or specific MAP?
- Know a lot about BM; not so much specific NM factors for ACL risk Important, as NM factors are modifiable via training Identify NM factors = target for prevention efforts Purpose of study; two-fold
- 25 sub elite netballers No injuries 6 weeks; no history
- Lab testing, 20 successful trials netball specific task Running approach incorporating side-step Single limb land on contralateral to take off Chose because it is a high risk task in sport
- Fitted with reflective markers; established lower limb 3D model 8 wireless EMG Muscles of interest were …
- Synchronous EMG data via Delsys through Nexus Vicon & AMTI to collect BM data for hip and knee rotations & moments
- EMG signal analysis = straight forward pipeline Movement artefact & rectification Linear envelope Normalisation & extraction
- Two-step PC and cluster analysis procedures Principal patterns and scores Correlation matrix Cluster validation Three clusters / MAPs INDIVIDUAL TRIALS CLUSTERED
- SPM to detect EMG and kinematic and kinetic differences Benefit = no need to pre select discrete Test for statistical differences along entire waveform
- MAP-1 = high prep activity glutes, hams & gas; moderate activity glutes and hams during landing; low peak quads MAP-2 = low prep activity of glutes and hams/delayed MHAM prep; rapid spikes / high peak activity of majority of muscles MAP-3 = moderate to high prep activity of glute and hams; but low activation of these muscles during landing; exteneded quads activation
- Kinematically; MAP-2 = most desirable (hip flexion, hip adduction, knee abduction, knee IR) High activation during landing Opposite for MAP-3
- Knee moments also play a role, potentially even more for ACL load / strain MAP-2 = worst for moments (frontal and transverse plane hip and knee) Preparatory activity, particularly of glutes and hams MAP-1 and MAP-3 opposite Better prep activity = better prepared for high landing forces Extended quads of MAP-3, maybe supporting during landing
- Good vs. bad; not quite Characteristics Target characteristics How do we do that? Are other tasks the same NM charactersitics?