Dynamics. Forward dynamics: Inverse dynamics: Biomecânica. Filipa Sousa. Areas of complex BIOMECHANICAL evaluation: Inverse dynamometry F = m * a

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1 Areas of complex BIOMECHANICAL evaluation: Biomecânica Filipa Sousa Porto Biomechanics Laboratory (LABIOMEP), Faculty of Sports, University of Porto, Porto, Portugal KINEMETRY ANTHROPOMETRY DYNAMOMETRY EMG Position Orientation (time) Movement (Displacement) Velocity Acceleration Dimensions linear surfaces volumes Inertial characteristics mass moment of inertia Inverse dynamometry F = m * a Forces internal external Moments (torques) Pressures Muscular activity (adapted from Baumann, 995) Forward dynamics: F F ma Inverse dynamics: a x x m x F F

2 Forward dynamics: Strain gauges F F ma a Force and pressure transducers: - Strain gauges - Force Plates - - Dynamometers - Isokinetic dynamometers - Isometric dynamometers - Dynamic dynamometers (Bartlett, 997) Force and torque components which act on the performer (Bartlett, 997) Force and torque components which act on the performer Vectorial expression of forces with location (and migration) of the centre of pressure No insight on force distribution along the contact surface Used for foot strike patterns, balance, input for inverse dynamics Whole-body measurements

3 They detect force and converts (transduce) it into electrical signal Force plate transducers Data examples Strain gauges Material which electrical resistance changes with its deformation (strain) - sensitive to temperature - less expensive and easier to install - more suitable for statical situations Piezoelectric They rely on the development of a electrical charge by a crystal (e.g. Quartz) when subject to a force - drift disadvantage for static analysis Different surfaces Different foot strike Different shoes Ground contact forces in running (vertical component). (Adapted from Nigg, 98, quoted by Bartlett, 997) Data examples Vertical GRF in standing vertical jump (Bartlett, 997) Gaitway System (Kystler) 3

4 GRF vertical component (Fy) st Vertical Peak Slope (gradient) Intermediate minimal force nd Vertical Peak 75 ms vertical impulse (passive) Total vertical impulse Support time Double support time Based on Soares, R. (5) Values of the first peak (PC) (bw) 8 8 Walking Running High J Long J Triple (step) Walking Running High J Long J Triple (step) Adapted from BAUMMAN & STUCKLE (98)

5 Data examples Vertical RF Resultant vector Acceleration Horizontal RF Deceleration Pronation Lateral-medial RF CP migration Supination Ground contact forces in walking (3D) (from Amadio et al., 99) Naide Gomes - componente vertical 3 passagens 3 Naide Gomes - componente médio-lateral 3 passagens Nelson Évora - componente antero-posterior passagens t (s) Naide Gomes - componente vertical 3 passagens Naide Gomes - componente antero-posterior 3 passagens 5 Nelson Évora - componente vertical passagens 3 Nelson Évora - componente médio-lateral passagens

6 Statics use for balance evaluation Stabilogrametry t apoio = paulo.7 Paulo s componente vertical paulo Paulo componente antero-posterior paulo Paulo componente médio-lateral Vertical: Máx: 5.95 * Peso =. N, aos.5 s -5 8 Antero-posterior: Máx:. * Peso = 39. N, aos. s - 8 Médio-lateral: Máx:.9 * Peso = 75. N, aos.9 s t apoio = marisa.5 Marisa s componente vertical 7 marisa Marisa componente antero-posterior.5 marisa Marisa componente médio-lateral Rambling and trembling assessment for neuro-motor balance analysis - 8 Vertical: Máx: 7. * Peso = N, aos.3 s -5 8 Antero-posterior: Máx:.38 * Peso = 37. N, aos.5 s Médio-lateral: Máx:.7 * Peso = 3. N, aos. s and pressure transducers Rear foot Midfoot Forward foot % 5% 3% % 5% 3% % 5% 3% - Foot area of contact - Qualitative assessment of pressure - Anthropometry of the foot Gait dynamometry of pre-pubertal children with different dorsal extra-loads (from Vilas-Boas et al., ) Based on Soares, R. (5)

7 Data processing - D colour coded displays - 3D wire frame displays - Force, maximal pressure and contact area - Pressure-time integral for all regions of the foot - Centre of pressure path Capacitive pressure transducers N (Bartlett et al, 99) r x c = number of capacitors 3 layer construction: A matrix of rows and columns of conducting material, which sandwich a layer of capacitive (dielectric) material EMED insoles 85, 7 or 5 sensors Hz, 5Hz and Hz Accuracy = 5%; Hysteresis = 3%; Peak up to 7 kpa 7

8 Conductive pressure transducers Also a 3 layer construction : A matrix of rows and columns of conducting material, which sandwich a layer of resistive material Piezoelectric pressure transducers Also a 3 layer construction : A matrix of rows and columns of conducting material, which sandwich a layer of resistive material - Not sensitive to temperature - Sensitive to temperature - Much thinner and inexpensive - Thick (3 to mm) and expensive - Calibration much more linear but instable - Each transducer requires individual connections AMTI conform (Derrick and Hamill, 99) - Flexible but fragile - Can be cut to foot size Developed by Henning et al, 993) - Flexible F-Scan insoles 9 sensors (5. mm ) Hz Peak up to 35 kpa not commercially available 99 sensors (3 mm ) Hz Accuracy = %; Hysteresis = %; Peak up to 5 kpa Platforms Insoles Hand grip Other transducers 8

9 Data processing 9

10 Pressure transducers