Fatigue Presentation

FATIGUE • Feeling of tiredness & lack of strength due to physical / mental strain or illness , which can be ameliorated through additional rest

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MUSCLE FATIGUE • Any exercise induced reduction in the ability of muscle to generate force or power regardless of whether or not the task can be sustained

Gandevia , 2001

SC 09/19/09

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NORMAL FATIGUE • A state of general tiredness which is the result of overexertion & can be reversed by rest

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PATHOLOGICAL FATIGUE

• A state characterized by weariness unrelated to previous exertion levels & is usually not reversible by rest

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• Normal fatigue

• Pathological fatigue

• Rapid onset

• Gradual onset

• Short duration

• Long duration

• Single identifiable cause

• Multiple unknown causes

• Protective

• Abnormal 09/19/09

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CHRONIC FATIGUE SYNDROME • Abnormally excessive • Unexplained • Persistent for six months or more

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NEUROLOGICAL FATIGUE • Subjective lack of physical or mental energy which is perceived by the individual or caregiver to interfere with usual & desired activities MS council clinical practice guidelines ,1998 09/19/09

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Types of fatigue

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2 types : 3.Physical fatigue 5.Mental fatigue

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PHYSICAL FATIGUE • Inability to exert force within one’s muscles to the degree that would be expected given the individual’s general physical fitness

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Muscle weakness

True weakness Perceived weakness

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 Objective

weakness

A

condition where the instantaneus force exerted by the muscle is less than that would be expected

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 Subjective

weakness

A

condition where it seems to the patient that more than normal effort is required to exert a given amount of force

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 Enhanced

perception of limited endurance of sustained mental activities

 Manifests

as somnolence or just decrease of attention 09/19/09

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 Mental  Lack

stress

of sleep

 Depression  Chemical

causes 09/19/09

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 Reduction

in the ability of muscle to perform work because of impairment anywhere along the command from neuromuscular transmission to the actin – myosin cross bridging

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 Peripheral

model assumes fatigue at one or more sites which initiates muscle contraction

 Therefore

dependent on the localized chemical conditions of the muscles

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 Depletion

of energy substrates Aerobic metabolism Anaerobic metabolism

 Change

in intracellular ion levels leak of calcium 09/19/09

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 Decline

in force output due to reduction in the neural drive or nerve based motor commands to the working muscles

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 Protective

phenomenon

 Works

to preserve the integrity of system by initiating muscle fatigue through muscle decruitment

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

Failure in integration of limbic input & the motor functions within basal ganglia

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 TNF-ALPHA  INTERLEUKIN

–6

Metabolic abnormalities of frontal cortex & basal ganglia

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 Hypofunctioning  Reduced

Cortisol secretion

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 Increased

level of serotonin in brain during exercise , peak at fatigue

 Effects

on arousal , lethargy , sleepiness & mood 09/19/09

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 Change

in the force response to electric stimulation during rest following exercise relative to pre stimulation force

 Reveals

any loss of force in the muscle tissue after constant activation

 Decline

fatigue

in force reflects the severity of 09/19/09

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 Rest

twitches before & after MVC

 Attenuation

of post stimulation twitches indicate peripheral fatigue

 Dominant

slowing of the relaxation

phase 09/19/09

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 Changes

in sarcolemma

Variables :  Amplitude  Frequency  Muscle fiber conduction velocity 09/19/09

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 Amplitude

increases during submaximal exercise

 During

high contraction , amplitude declines

 Change

in frequency spectrum & MFCV 09/19/09

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

MVC + Electrical stimulation to motor end plate



Increased exertion of force demonstrates Central Activation Failure



The technique allows quantification of CAF



Can’t differentiate between various central causes 09/19/09

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 Magnetic

& electrical stimulation of motor cortex

 Artificially

activates CNS

 Response

is measured at output site

 Studies

reported diminished output after fatiguing contraction 09/19/09

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 Responses

following magnetic stimulation are often submaximal

 Any

change in motor output is interpreted as change in excitability of motor cortex as induced by stimulus

 Not

the actual diminished voluntary drive 09/19/09

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 Negative

movement related cortical EMG potential over the scalp 1 sec before a self paced motor act

 Generated

by supplementary motor area & primary motor cortex 09/19/09

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 During

high force voluntary contraction , RP increases

 Provides

measure to determine changes at the motor cortex level instead at the output site

 Does

not require artificial stimulation

 Prominent

tool to study central changes during natural repetitive contractions 09/19/09

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 70

% of patients with MS

 Present

even at rest

 Both

physical & cognitive components 09/19/09

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 Worsened

by stress & increase in temperature

 No

correlation with age, neurological impairment , sleep disturbance

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 25

% - 92 % of stroke survivors

 Persists

despite excellent neurological recovery

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 Tends

to decrease with time

 Independent

of stroke severity, localization or functional impairment

 Correlation

with brainstem or thalamic

stroke

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 Incidence  Related

– 40%

to Dopamine deficiency

 Levodopa

normalizes cortical motor neuron excitability

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

Muscle weakness – the commonest symptom



Metabolic / mitochondrial disorders : Fatigue



Exercise intolerance



Weak atrophic muscles functioning at their limits metabolically



Energy supply fails because of metabolic compromise 09/19/09

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 Abnormal

rise in sEMG potential

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

Reported by 25- 40 %



Post encephalitic damage



Reticular Activating System



Dopaminergic neurons in Substantia Nigra 09/19/09

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 Manifests

at the onset

 Persists

for months regardless of full recovery of PNS

 Central

fatigue component

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 To

ascertain whether normal or pathological

 To

identify possible predisposing factors

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

Onset



Duration



Severity



Daily pattern



Aggravating / Relieving factors



Impact on daily living 09/19/09

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9

item measure

7

point likert scale format

 Ranges

from : 1 ( strongly disagree) 7 ( strongly agree) 09/19/09

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1. 2. 3. 4. 5. 6. 7. 8. 9.

My motivation is lower when I am fatigued. Exercise brings on my fatigue. I am easily fatigued. Fatigue interferes with my physical functioning. Fatigue causes frequent problems for me. My fatigue prevents sustained physical functioning. Fatigue interferes with carrying out certain duties and responsibilities. Fatigue is among my three most disabling symptoms. Fatigue interferes with my work, family or social life

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 Total

score - Mean score across the 9 statements

 FSS

score > 4 :

Severe fatigue

 Most

widely used measure in neurological conditions

 Able

to differentiate between patients & healthy subjects 09/19/09

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 High

validity

 Internal

consistency ( cronbach alpha = 0.81 – 0.95 )

 Test

retest reliability ( 0.8 ) in patients with MS & Polyneuropathies

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 Modification

of VAS for pain

 Scores

range from : to

0 (no fatigue) 10

( worst fatigue )  VAS

score > 4.4 fatigue

: 09/19/09

Severe 60

 Simple

, practical , reproducible & fast to apply

 Used

to measure fatigue changes over time intervals (minutes, hours )

 To

closely estimate average intensity changes over longer time period ( weeks , months ) 09/19/09

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

4 statements



7 point likert scale



Total score = mean score of the 4 statements



Able to differentiate between patients & healthy subjects



Internal consistency ( cronbech alpha = 0.81) 62 09/19/09



Developed for patients with MS



40 independent symptom based questions



Scale of : to

“ 0 (no problem )” “ 4 ( extreme problem)”



63 Total score = Sum of responses to all 40 09/19/09

 Minimum  Maximum

score =

0 ( No fatigue)

score = 160 ( Extreme

fatigue)  FIS

score of 80 or higher correlates with moderate to severe fatigue

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 Energy

category - one of the 6 categories of NHP

 Consists

of 3 yes / no questions

 Total

score = no. of questions answered with yes 100 total no. of questions 09/19/09

* 65

0 ( No complaints )  100 ( Answered yes to all complaints ) 

 Internal

consistency ( Cronbach α =

0.71)  Test

retest reliability (Spearman ρ = 0.77 – 0.86) in patients with stroke 09/19/09

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 Fatigue

scores are not interchangeable

 Structure

& attributes of questionnaire differ remarkably

 Weight

of individual components of fatigue contribute to significant interscale score deviation 09/19/09

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 FSS

: Asseses neuromuscular fatigue

 VAS

:

No identifiable domains

 FIS

: Less emphasis on physical fatigue More on emotional, cognitive 09/19/09

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 Identification

& optimum management of potential factors

 Nutrition

counselling

 Drugs

Antidepressants Amantadine Modafinil

:

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 Combination

of cognitive & behaviour therapy approaches

 Identification

of unhelpful, anxiety provoking thoughts & challenges

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Stress management techniques :  Relaxation  Hypnosis  Guided

imagery  Distraction

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

Moderate intensity : Aerobic training Strength training Flexibility training



Group therapy



Level II evidence 09/19/09

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 Fatigue

dairy

 Restricting

timing of daily activities

 Prioritizing

tasks 09/19/09

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 Imp

to make the patient aware that fatigue is real

 Recognition

by patients, caregivers & family members

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Goals : 

To improve understanding in patients care giving

 To

involve patient, caregivers in setting goals, directing & evaluating the intervention 09/19/09

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 Relaxation

training

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 Chinese

technique of inserting needles into the body

 Strengthen

the vital essence of human body

 Removes

the blockage of channels 09/19/09

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

S C Gandevia : Spinal and Supraspinal Factors in Human Muscle Fatigue .Physiological Reviews , 2001 ; 81 : 4



Abhijit Chaudhuri, Peter O Behan :Fatigue in neurological disorders ; The Lancet ; 2004 ; 363, 20



Marloon groot et al : Fatigue associated with stroke and other neurologic conditions: implications for stroke rehabilitation Arc hives of Physical Medicine and Rehabilitation Volume 84, Issue 11, November 2003, Pages 1714-1720 09/19/09

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M

J Zwartz : Clinical neurophysiology of fatigue ; Clinical neurology , 119 , (2008), 2-10

 William

s, B Krupp : Multiple sclerosis related fatigue ; Phys Med Rehab Clin N Am , 16 (2005) , 483

 Physiolological

Latash

Basis Of Movement : 09/19/09

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