Motor Learning - PHYL 4518 Fall 2024 Wk 4 PDF

PHYL 4518 Motor Learning F2024 – Wk 4 Zoe Chan, PhD [email protected] Review of in-class quiz Physical abilities – Highly modifiable through training (e.g., muscle strength, muscle mass, flexibility, maximal oxygen uptake) – Static abilities with limited potenti...

PHYL 4518 Motor Learning F2024 – Wk 4 Zoe Chan, PhD [email protected] Review of in-class quiz Physical abilities – Highly modifiable through training (e.g., muscle strength, muscle mass, flexibility, maximal oxygen uptake) – Static abilities with limited potential to change (e.g., muscle fiber type, height, lung size) Largely genetic – Not to be confused with static vs. dynamic exercises Review of in-class quiz Movement continuity Discrete Serial Continuo us Throwing a punch Steering a car Playing a piano composition Triple jump  Review of in-class quiz Triple jump https://www.tdk.com/en/tech-mag/athletic/003 Review of in-class quiz Simple vs. complex reaction time – Simple: one stimulus, one response 1 Stimulu s A Response Review of in-class quiz Simple vs. complex reaction time – Complex (choice): two or more stimuli, specific response 1 2 for each 3 Stimulu s A B C Response  Review of in-class quiz Simple vs. complex reaction time – Complex (discrimination): two or more stimuli, only 1one is 2relevant 3 Stimulu s and paired with a response “Only press the button when the red light is lit up” A Response  Review of relative age effect Relative age effect: preference for selecting athletes born earlier in the year Example: January 15, 2024 selection for 9-year-olds Born on Born on 16 15 January January 2014 2015 https://talentdevelopmentinirishfootball.com/2017/06/27/relative-age-effect-in-irish-elite-youth-football/  Review of relative age effect Relative age effect: preference for selecting athletes born earlier in the year Example: age cut-off on April 1, 2014 Who has the most advantage? 2014, March 2014, 2015, March Not in same age April category https://talentdevelopmentinirishfootball.com/2017/06/27/relative-age-effect-in-irish-elite-youth-football/ Unit 3 Peripheral neuromuscular mechanisms in executing movement PHYL 4518 Motor learning F2024 – Wk 4  Understand the basic mechanical properties of muscles. Identify how they contribute to and enhance movement. Describe the organization of the central and peripheral nervous system contributing to movement Today’s Explain the basic functions of neurons and how they communicate learning objectives Describe the basic physiology and organization of the motor units Muscle properties Skeletal muscles – Central area of muscle tissue – Tendons on both ends Three mechanical properties Contractility: shorten Extensibility: stretch to produce force Muscle tissue only and Elasticity: recoil from stretch Muscle tissue Connective tissues (runs longitudinally throughout the muscle Muscle properties A simplified model – Contractile element (CE): produce force – Elastic elements (PE + SE): stores and releases force through recoil SE Contractile element Muscle CE PE SE Elastic elements Parallel (PE) – Connective tissues Serial/series (SE) - Tendons Muscle properties Stretch and recoil properties – Vary greatly – Depend on: shortening or lengthening velocity, tissue length and thickness, and health of tissue Nervous system regulates mechanical properties (stiffness, force absorption and recoil) – By changing timing and amount of muscle contraction – Changes the flow of forces or energy Muscle properties External forces (body weight) Stretch muscle- tendon complex Force stored in the EE (tendon) Released Muscle work is reduced through recoil Muscle properties Muscle contract Build up force Transfer and stored in tendon Released rapidly Concentric contraction Muscle properties External force Stretched tendon Energy stored in the EE Transferred to muscle Force absorbed by Eccentric contraction muscle  Force-length relationship Passive force – Resistance of relaxed muscle to stretch (EE) Resting length – Length at which passive force begins to develop Muscle Bundle Stretching by Ddara. Force-length relationship rce Force (max) e fo siv Pas ‘Resting’ length 0 Short Long Muscle Length Force-length relationship Active force – Produced by active cross-bridges during contraction (CE) – Sarcomere: basic contractile force generating unit Two protein filaments: actin and myosin Muscle is Muscle at optimal overstretched length Too little overlap Full cross-bridge Few actin-myosin formation  Force-length relationship rce Force (max) e fo Ac tiv siv e fo Pas rc e ‘Resting’ Muscle is length understretched 0 Too much overlap Short Long Few actin-myosin Muscle Length binding  Force-length relationship rce Force (max) e fo Ac tiv siv e fo Pas rc e Lo ‘Resting’ length 0 Short Long Muscle Length Optimal length (Lo): Length at which greatest active  Force-length relationship Tota l force rce Force (max) e fo Ac tiv siv e fo Pas rc e Lo ‘Resting’ length 0 Short Long Muscle Length Total force: active + passive force  Force-length relationship Passive force Resting length – Resistance of – Length at which relaxed muscle to passive force stretch (EE) begins to develop Active force Optimal length – Produced by – Length at which active cross- greatest active bridges during force occurs contraction (CE) Total force – Active + passive  Stretch-shorten cycle (SSC) Concentric vs. eccentric contraction Concentric Length of muscle shortens Force generated Eccentric Muscle lengthens/stretched Muscle force < resistance https://www.superfituk.co.uk/blog/eccentric-muscle-contraction/  Stretch-shorten cycle (SSC) Concentric contraction – Squat jump – Start at squat position – Quadriceps (anterior thigh muscles) Concentric contraction – Knee extension  Stretch-shorten cycle (SSC) Eccentric-concentric contraction – Counter-movement jump – Start at standing position then squat (descent) – Quadriceps eccentrically contact to stop downward movement Eccentric contraction – Quadriceps (anterior thigh No pause! muscles) Concentric contraction – Knee extension  Stretch-shorten cycle (SSC) Eccentric-concentric contraction or stretch-shorten Musclesmovement stretched rapidly prior to concentric contraction More force is produced Mechanism of SSC: not fully known – Preload effect: more time for contraction, muscle already activated Preloaded muscle with force Eccentric + Concentric = More time!  Stretch-shorten cycle (SSC) Eccentric-concentric contraction or stretch-shorten Musclesmovement stretched rapidly prior to concentric contraction More force is produced Mechanism of SSC: not fully known – Preload effect – Buildup of stored elastic energy in the elastic tissues during eccentric phase, released at recoil during concentric phase https://medium.com/@ameypatil/the-rubber-band-theory-3c7272e02102  Stretch-shorten cycle (SSC) Eccentric-concentric contraction or stretch-shorten Musclesmovement stretched rapidly prior to concentric contraction More force is produced Mechanism of SSC: not fully known – Preload effect – Buildup of stored elastic energy in the elastic tissues during eccentric phase, released at recoil during concentric phase – Optimal length: muscle stretched at eccentric phase Force-length relationship Tota l force rce Force (max) e fo Ac tiv siv e fo Pas rc e Lo ‘Resting’ length 0 Short Long Muscle Length Stretched during the eccentric phase  Stretch-shorten cycle (SSC) Eccentric-concentric contraction or stretch-shorten Musclesmovement stretched rapidly prior to concentric contraction More force is produced Mechanism of SSC: not fully known – Preload effect – Buildup of stored elastic energy in the elastic tissues during eccentric phase, released at recoil during concentric phase – Optimal length – Excite reflex mechanisms  Stretch-shorten cycle (SSC) SE Stiffer SE = more SSC CE PE Less Stiff SE Stiff But: Stiff SEC SE SE 2 Same force during F Can store more energy during ECC Similar energy return during CON ECC More energy return during CON  Exercise training and neuromechanics Flexibility training (static stretching) Strength training Plyometric training – May alter muscle-tendon properties https://www.sportsperformancebulletin.com/training/plyometric-training-increase-your-speed-and-power Flexibility training and neuromechanics Flexibility training (static stretching) – May alter muscle-tendon properties Acute flexibility exercises – Transient increase in joint range of motion (ROM) Long-term flexibility training  chronic increases in joint ROM – Reduced stiffness of the muscle-tendon complex – More pain tolerance to stretching – A longer muscle tendon complex (added How might this impact SSC? sarcomeres) Flexibility training and neuromechanics Stretching before strength and power performance may reduce performance – “Stress-induced strength loss”: loss of strength resulting in acute static stretching Stretching reduced stiffness – More compliant Reduced – Absorb and dissipate force stiffness – Reduce transmission of force – Changes to length-force relationship Flexibility training and neuromechanics Tota l force rce Force (max) e fo Ac tiv siv e fo Pas rc e ‘Resting’ length 0 Short Long Muscle Length Flexibility training and neuromechanics Tota l force rce Force (max) e fo Ac tiv siv e fo Pas rc e ‘Resting’ length 0 Short Long Muscle Length  Flexibility training Data on flexibility training and injury prevention is varied and inconclusive – Little/inconclusive evidence  stretching before or after exercise help reduce muscle–tendon injuries or muscle soreness Used as a tool to maintain muscle health, particularly in aging populations Strength training and neuromechanics Resistance training Strength training may increase muscle- tendon stiffness – Increase tissue thickness (hypertrophy) – Increase tissue density Plyometric training and neuromechanics Increasing stretch force, targeting SSC High-effort power training (forceful eccentric followed by an explosive rapid reversal concentric) Box jump: Rapid concentric Taller box: more forceful eccentric Plyometric training and neuromechanics Ballistic training – Light-load weight-lifting – Maximal speed of concentric phase Plyometric training are designed to: – Increase muscle stiffness How would that change the force-length relationshi – Maximize elastic recoil (energy return) – Develop neural coordination mechanisms that maximize rapid contractions (increased neural drive and improved intermuscular coordination) Plyometric training and neuromechanics How would that change the force-length relationship? Tota l force rce Force (max) e fo Ac tiv siv e fo Pas rc e ‘Resting’ length 0 Short Long Muscle Length Organization of the nervous system Central nervous system – Brain and spinal cord – Integration and command centre for the entire nervous system https://www.technologynetworks.com/neuroscience/articles/gray-matter-vs-white-matter-322973 Organization of the nervous system Direction of information Involuntary vs. voluntary  Neuron structure Neurons have: −cell bodies (Soma) Signals are electrical −dendrites (signal in)impulses −axons (signals out) Dendrite SOMA Axon  Neuron structure Neurons classified as sensory (afferent) motor (efferent) Interneurons Action potentials Bioelectric signal called an action potential (AP) − Neuron to neuron(s) − Neuron to muscles Spread through synapses Neurons communicate via changes in the charges across membrane − Sodium and potassium ions (Na+ and K+) − Depolarization − Repolarization − Hyperpolarization AP moves down neuron  Action potentials Starts with influx of Na+ ions Depolarization − Occurs when cell depolarized on to threshold depolarizati (-55 mV) − Voltage gated Na+ channels open − Out to In  Action potentials Starts with influx of Na+ ions Depolarization Repolarization − Voltage gated K+ channels on Repo open depolarizati lariz − In to Out n atio  Action potentials Starts with influx of Na+ ions Depolarization Repolarization Hyperpolarizatio n on Repo − Overshoot depolarizati lariz and closing of atio K+ channels n After-hyperpolarization  Neuron function Neurotransmitters released from presynaptic neuron may depolarize the postsynaptic neuron, generating an excitatory postsynaptic potential (EPSP) Facilitated AP Membrane potential 0 (EPSP ) -55 EPSP -70  Neuron function Some neurotransmitters may block depolarization, generating an inhibitory postsynaptic potential (IPSP) Less likely to generate an action potential (inhibited) AP Membrane potential 0 (IPSP ) -55 IPSP -70  Neuron function Multiple EPSPs in the postsynaptic neuron may summate to a threshold level to generate AP Summation may be temporal or spatial Ratio of EPSPs to IPSPs Summation reach threshold > Action potential  Motor neurons Axons of each motor neurons branch off Motor neurons activate a number of muscle fibers Motor unit (MU): Lower muscle neuron (found in the spinal cord) and all muscle fibers it innervates  Motor unit Innervation ratio: number of fibers controlled by one neuron All-or-none principle: all muscle fibers within one motor unit contract or none contract in response to the neuron’s action potential Fine movement: lower innervation ratio (e.g., hand muscles have 130 motor neurons and average innervation ratio of 1:110) Gross movement (e.g., gastrocnemius 1:1500)  Motor unit Spread out within the muscle MU’s force distributed over a larger area – “smoother” contraction – Equal force on tendon May help delay fatigue – Active and inactive fibres Fibres of one motor unit sharing metabolites and Fibres of another motor unit capillaries