MEDI258 Week 7 PDF

MEDI258 - Week 7 Control of single joint and multi-joint movements 1. Single joint movements - Triphasic pattern 2. Can elements of this basic pattern be reproduced according to the movement context? 3. How has the musculoskeletal system evolved to fulfil the movement requirements of...

MEDI258 - Week 7 Control of single joint and multi-joint movements 1. Single joint movements - Triphasic pattern 2. Can elements of this basic pattern be reproduced according to the movement context? 3. How has the musculoskeletal system evolved to fulfil the movement requirements of everyday life (multi-joint movements)? Prof Paul Stapley, MEDI258 Sensorimotor Control, Week 7 1  Patterns of muscle activation 2 Types of muscle activation: 1. Tonic: relatively long, change slowly Examples? 2. Phasic: Characterized by short bursts...Examples? Lecture will outline basic characteristics of phasic muscle activation in human movement. Will also explain how muscles have evolved to satisfy constraints of everyday life - multi-joint movements. Prof Paul Stapley, MEDI258 Sensorimotor Control, Week 7 2 Phasic activation: wrist flexor and extensor muscles - wrist flexion # velocities fast slow Basic characteristics of triphasic EMG pattern... Prof Paul Stapley, MEDI258 Sensorimotor Control, Week 7 3  Symmetry of movement = timing and amplitude of AG/ANT activity How does timing and amplitude of max velocity AG/ANT relationship affect symmetry? max velocity What is symmetry of movement? Increase in AG activation and max velocity earlier onset of ANT => acceleration shorter Decrease AG and delay ANT => lengthen acceleration Prof Paul Stapley, MEDI258 Sensorimotor Control, Week 7 4 Cooke and Brown 1990a Movements are bell-shaped. Why? How does CNS produce symmetry of movement? Triphasic pattern exists for simple arm movements: AG1 (initiation) ANT1 (braking, control) AG2 (stretch reflex-dependent damping mechanism) Controls oscillations Studied relations between EMG and temporal structure of movements What did they do? Manipulated different SR movements using phase-plane paradigm Prof Paul Stapley, MEDI258 Sensorimotor Control, Week 7 5 Results: Phase-plane exp Subject 1 Subject 2 A. Peak velocity B. Amplitude C. Duration SR = 1 SR = 1 Peak Vel 2 subjects What does it show? Amplitude Very tight relationship between distribution of 3 Duration characteristics using paradigm Prof Paul Stapley, MEDI258 Sensorimotor Control, Week 7 6 Anything else? Different SR give different patterns As SR increased, duration of AG1 increased Onset of ANT1 delayed AG1 ANT Movements with large SR’s SRs showed large AG2 AG1 Why would that occur (large AG2 with larger SR’s)? AG1 Prof Paul Stapley, MEDI258 Sensorimotor Control, Week 7 7  AG1 duration as function of SR AG1 magnitude Decreased as SR increased 0.2-0.8 What does it show? Then remained virtually Sometimes were clusters unchanged More variable for movements