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• Performance measurement is essential for:

  • Performance assessment/evaluation
  • Motor learning and control research
• Two general categories of performance measures:

  • Performance outcome measures:
  • Indicates the outcome or result of performing a motor skill (e.g., how far did a person throw the ball)
  • Does not provide info about the activity of various muscles involved
  • Measures time, error, distance
  • Performance production measures:
  • Indicates the performance of specific aspects
  • Measures displacement, velocity, angles, torques, EMG, EEG, fMRI
• Error measures:

  • Allow evaluation of performance for skills with spatial or temporal accuracy action goals
  • Show how well performance is against a criterion/goal
• Assessing error for skills with one-dimensional accuracy goals:

  • Absolute error: magnitude of the error, scalar, absolute value
  • Constant error: magnitude and direction of error, vector
  • Variable error: consistency of the error, SD
• Assessing error for two-dimensional movement goals:

  • Radial error: calculate the hypotenuse of the error
  • Qualitative assessment of bias and consistency
• Assessing error for continuous skills:

  • Root mean squared error: amount of error between performance curve produced and the criterion performance curve for a specific amount of time during which the performance is sampled
• Kinematics:

  • Description of motion without regards to force or mass
  • Displacement: spatial position of a limb or joint over a period of time
  • Velocity: rate of change in an object’s position with respect to time
  • Acceleration: change in velocity over change in time
• Kinetics:

  • Study of the role of force as a cause of motion
  • Human movements involve both internal and external sources of force
  • Newton's laws (inertia, f=ma, opp/equal) apply to force
  • Force measurement: direct (force plates, strain gauges, force transducers) and indirect (calculations)
  • Measuring kinetics: internal/external forces, force plates, strain gauges, force transducers
• Measuring muscle activity:

  • Electromyography (EMG): measurement of the electrical activity of muscle
  • Whole muscle mechanomyography (wMMG)
  • Near infrared spectroscopy (NIRS)
• Brain activity measures:

  • Electroencephalography (EEG): detection of cortical activity via scalp electrodes
  • Positron emission topography (PET): detection of metabolic brain activity
  • Functional magnetic resonance imaging (fMRI): brain activity detected by changes in blood oxygenation
  • Magnetoencephalography (MEG): measures magnetic fields first created by neuronal activity
  • Transcranial magnetic stimulation (TMS): magnetic pulse delivered to brain either excites or inhibits brain activity
  • Microneurography: measures impulses in peripheral nerves
• Electroencephalography (EEG):

  • Detects cortical activity via scalp electrodes
  • Active brain regions produce electrical activity
  • Limitations:
  • Doesn't show which anatomical structures are active
  • Only records surface activity
  • Brain computer interfaces use EEG to measure brain activity and transform it into motion (robots, wheelchairs, etc.)
• Positron emission topography (PET):

  • Detects metabolic brain activity
  • Radioactive positrons interact with blood
  • Scans detect activity in various locations
  • Limitations:
  • Subjects must be stationary (cannot use for motor skills)
  • Requires injection of isotope
• Functional magnetic resonance imaging (fMRI):

  • Brain activity detected by changes in blood oxygenation
  • Blood oxygenation level dependent (BOLD) amplitudes
  • Limitation:
  • Subject must be stationary
• Magnetoencephalography (MEG):

  • Measures magnetic fields created by neuronal activity
  • Higher temporal resolution than fMRI and PET
  • Increased accuracy of activity location compared to EEG
  • Limitations:
  • Subject must be stationary
  • Doesn't show which structures are metabolically active
• Transcranial magnetic stimulation (TMS):

  • Magnetic pulse delivered to brain either excites or inhibits brain activity
  • Causes temporary movement artificially through stimulation
  • Limitations:
  • Must estimate location of stimulus
  • May cause discomfort at stimulation site
• Microneurography:

  • Measures impulses in peripheral nerves
  • Used to understand function of various nerves
  • Limitations:
  • Fine wire needle must be inserted
  • Only small movements tested