Understanding Motor Skills Introduction Focus: Response mechanism of the human body as the output of information processing “input—mediation—output” Knowledge bases from: Biomechanics Kinesiology Psychology Neuroscience

Control & Acquisition of Motor Responses Skill - the ability to use the correct muscles with the exact force necessary to perform the desired response with proper sequence and timing (Jensen, Schultz, and Bangerter, 1983) Three Aspects: spatial-temporal precision “doing the right thing at the right time” adaptability to changing environmental conditions consistency of action from occasion to occasion

Types of Responses Discrete Movements — Repetitive Movements — Sequential Movements— involving a single reaching movement to a stationary target; may or may not be visually guided involving a repetition of a single movement to a stationary target(s) involving discrete movements to a number of stationary targets regularly or irregularly spaced

Continuous movements — Types of Responses Continuous movements — Static positioning — involving movements that require muscular control adjustments of some degree during the movement consisting of maintaining a specific position of a body member for a period of time

Sensory Feedback motor responses can be influenced by both internal and external feedback Close-loop servocontrol model feedback — ( high impact ) feedforward — sensory information that is available during or after the motor response sensory info that is available prior to the action that regulates and triggers coordinated responses

Sources of feedback Sensory Feedback Kinesthesis (proprioception) Receptors: Muscle spindle for muscle length and rate of change Golgi tendon organ for muscle force Vision Sound

= + Speed of Movements Total Response Time Reaction time Movement time —>the time from onset of a signal calling for a response until the beginning of the response + Movement time —>the time from the beginning of the response until its completion

Reaction Time - under ideal conditions, simple reaction time is between 150 - 200 msec Influences on reaction time : stimulus modality stimulus detectability preparedness or expectancy of a signal age spatial frequency stimulus location

Movement Time Direction of Movement Distance and Accuracy Required this affects the time to make the movement controlled arm movements that are primarily based on a pivoting of the elbow take less time than those that require a greater degree of upper-arm and shoulder action Distance and Accuracy Required Fitt’s Law

Fitt’s Law Fitt’s Law holds for : Movement Time MT = a + b log2 (2D/W) where : MT = movement time a,b = empirically derived constants, movement type dependent D = distance of mvmt from start to target center W = width of target Fitt’s Law holds for : movements of the head movements of the feet movements of the fingers and more

Accuracy of Movements Often accuracy of a response is of greater importance than the response time, within limits —Location close-in, straight-ahead, below- shoulder positions reduce error (Fig. 9-11) —Distance overshooting short distance and undershooting long distance (Fig. 9-12) —Speed of Movement Schmidt’s Law: W = a+b(D/MT)