Neuromuscular Performance

muscle

fatiguability has to be initiated by a _____ contraction and is reversible with rest

central fatigue

spinal and supraspinal mechanisms

- within SC and brainstem

peripheral fatigue

mechanisms that occur at or distal to the NMJ

- this typically occurs more often

central

mechanisms of _____ fatigue

- inhibition of the motor cortex (feedback from afferents)

- inhibition of the alpha motor neuron at SC level

- alterations in motor neurons

- psychological factors

- pain

peripheral

mechanisms of _____ fatigue

- failure of neuromuscular transmission (not able to depolarize)

- impaired calcium release

- impaired binding of calcium to troponin

- depletion of ATP

- depletion of PC

- depletion of glycogen

- accumulation of lactate, H+, PO4-, Pi, etc. (affects pH/enzymes)

group I

____ ___ muscle afferents

thickly myelinated

communicates with motor neurons and interneurons in SC

- Ia= muscle spindle

- Ib= GTOs

group II

____ ____ muscle afferents

thickly myelinated

muscle spindle (slower conduction velocity than Ia)

group III

____ ____ muscle afferents

thinly myelinated

free nerve endings in CT of skeletal and cardiac muscle

primarily mechanical receptors

group IV

_____ ____ muscle afferents

unmyelinated

free nerve endings in CT of skeletal and cardiac muscle and within small vessels of muscle

primarily responsive to metabolic stimuli

groups III and IV

which two groups of muscle afferents are pain receptors that are also involved in the cardioventilatory response to exercise?

SO

during long term moderate to heavy submax exercise which muscle fibers are primarily used?

all 3

during incremental to maximal aerobic exercise which fiber types are used?

contraction

during static exercise muscle fiber types used are dependent on ______ intensity

- dictates level of occlusion

lactate; H+

_____ and ____ effects on contractile process

- decreased calcium release

- interferes with calcium/troponin binding

- disrupts Na+/K+ pumps

- inhibition of enzymes (PFK and Myosin ATPase)

neural

steadiness of muscle contraction gives an idea of ____ control

fine motor performance

what is the steadiness of muscle contraction's functional relevance?

steadiness

____ of muscle contraction influence by:

- sex of individual

- age

- stress

- disease processes

immediate muscle soreness

pain during and immediately after exercise

may persist for several hours after cessation of exercise

pain receptors likely stimulated by metabolic byproducts

DOMS

characterized by muscle tenderness, pain on palpation, and mechanical stiffness that appears approximately 8 hours after exercise

increases and peaks over the next 24-48 hours

usually subsides within 96 hours

mechanisms of DOMS

- damage to muscle fiber structural proteins and to connective tissue at muscle-tendon junction

- damage to sarcolemma = accumulation of Ca2+ = inhibition of ATP production = disruption in Ca2+ homeostasis

- tissue damage --> inflammation --> immune mediators --> edema

- pain receptors activated by pressure from swelling, accumulation of byproducts from tissue death, and immune system response

function

muscle soreness effect on muscle _____

- decreased strength/power/performance (even after pain subsides)

- neural activation impaired

- joint mechanics/ROM altered

can last several days to weeks

treatment of muscular soreness

- NSAIDS

- BCAA supplementation before heavy resistance exercise

- acute exercise (flush out metabolites)

- compression

- massage/stretching/cold water immersion???

- supplemental protein consumption

repeated bout effect

single bout of eccentric exercise protects against DOMS during subsequent bouts for several weeks to around 6 months

no

is there a sex difference for lower extremity exercise?

yes

is there a sex difference for upper extremity exercise?

stronger

men are ____ than women in general

fatigable

women are less ____ than men

stress

women have greater deficits in time-task failure with ____ when compared to men

- although this is likely mediated by strength rather than a sex difference

neural, metabolic, and ANS

what type of factors influence a sex difference and fatigability between men and women?

puberty

after ____ there is a significant sex difference in grip strength, pull strength, biceps strength, quadriceps strength, and flexed arm hang

children

____ have different relationships/responses with fatigability compared to adults

aging

_____ influence on neuromuscular performance

- sarcopenia (loss of muscle mass)

- loss of cortical gray matter (primary motor cortex)

- loss of cortical inhibition

- slower cross bridge mechanics and slower rates of Ca2+ uptake into the SR

fewer; larger

older adults have ____ motor units but they are _____

neuromuscular

_____ deficits observed with aging

- decreased strength and power

- decreased contraction speed/rate of force development

- increased variability

- voluntary activation (CNS drive to muscle)

- steadiness of muscle contraction (larger force fluctuations)

- more fatigable with dynamic contractions

less

under age 75, people tend to be ____ fatigable during isometric contractions due to slower CB cycling and Ca2+ kinetics

yes

in older adults is there a significant sex difference with UE exercise?

active; inactive

there is a greater difference in the male population between ___ and ___ individuals

active; lower leg

there is a greater difference in the female population between ___ and inactive individuals w/ ____ ____ lifts

women; less

___ are typically ____ fatigable during isometric contractions besides ankle dorsiflexors and knee extensors

sustained; weaker

during ____ isometric contractions there is not statistical difference between male and female but ____ individuals are less fatigable in general

sustained; more

during ____ isometric contractions women are ____ fatigue resistant

force, position supported, and position unsupported

what is the order of most fatigue resistant to least fatigue resistant between force, position supported, and position unsupported isometric contractions?

variable

fatigability between sexes during dynamic contractions is more ____ compared to isometric contractions

stress; increases

____ impacts neuromuscular performance ____ fatigability and impairs force control (steadiness)

decreased

older adults have ___ steadiness of muscle contraction when stress occurs

muscle mass mechanisms

number of CBs available to bind and thus produce force

fiber type distribution (more type II = more power)

occlusion of feed arteries (more muscle mass = more occlusion)

CB cycling mechanisms

Ca2+ kinetics

enzyme activity

fiber type distribution

task demands mechanisms

static or dynamic

stress

neural factors mechanisms

integrity of NMJ (transmission of AP)

voluntary activation

MU recruitment and discharge rate

muscle pain/soreness mechanisms

ROM issues

decreased strength/power/performance

neural impairments

EMG

the sum of all action potentials occuring within the recording area of an electrode

electrical

EMG estimates the amount of ____ activity (neural drive) occuring within a muscle

degree; rate

EMG can measure timing of muscle activation, ____ of muscle activation, and ____ of muscle fatigue

type; speed

EMG responses vary based on the ___ of contraction, ___ of contraction, and duration of contraction

0-5 mV

what is a normal surface EMG voltage?

5-10 mV

what is a normal indwelling EMG voltage?

- not sure this answer is correct

anatomic

____ factors that influence surface EMG (nonphysiological)

- subcutaneous tissue (adipose/CT)

- distribution/size of MU territories in the muscle

- distribution and number of muscle fibers in the MU territories

- length of the fibers

- spread of the endplates and tendon junctions within the MUs

- spread of innervation zones

- heterogeneity of fiber orientation

detection

____ system factors that influence surface EMG (nonphysiological)

- skin-electrode contact

- spatial filler for signal detection

- interelectrode distance

- electrode size and shape

- inclination of the detection system relative to muscle fiber orientation

- location of electrodes over the muscle

geometrical

_____ factors that influence surface EMG (nonphysiological)

- muscle fiber shortening

- shift of the muscle relative to the detection system

physical

____ factors that influence surface EMG (nonphysiological)

- conductivities of the tissues (dehydrated= less)

- amount of crosstalk from nearby muscles (standardized placements to prevent excessive)

physiological

____ factors that influence surface EMG

fiber membrane properties

- average muscle fiber conduction velocity

- distribution of MU conduction velocities

- distribution of conduction velocities of the fibers w/in the MUs

MU properties

- number of recruited motor units

- distribution of MU discharge rates

- statistics and coefficient of variation for discharge rate

- motor unit synchronization

2

there are ___ common methods to normalizing EMG:

- comparison to EMG amplitude during a MVC

- comparison to electrically evoked response (M wave)

excitability

we can use EMG to determine ____ of :

- skeletal muscle (M-wave)

- spinal pathways (H-reflex)

- supraspinal pathways (voluntary activation

as well as assessing fatigability of the neuromuscular system

M; peak; area

the ___ wave can be measured from ___ to peak or ___ under the curve

voluntary activation

supraspinal pathways

H-reflex

spinal pathways

M wave and twitch

muscle