Lectures 5&6 Flashcards
Health risks of obesity?
Stroke
Menstrual Irregularities
Gallbladder disease
Cancers
Obstructive pulmonary disease
Osteoarthritis
Glucose intolerance and diabetes
Dyslipidemia
Hypertension
Ischemic heart disease
Health risks of underweight
Malnutrition
Anorexia
Fluid-electrolyte imbalances
Osteoporosis
Cardiac arrhythmias
Renal and reproductive disorders
How does being active reduce the risk of death?
Being active is associated with a greater than 50% reduction in the risk of death.
1000 kcal/week additional energy expenditure = 20% reduction in Mortality rate
Leading causes of death
Heart disease - 23.4%
Cancer - 22%
Chronic lower respiratory diseases - 5.7%
Mathematics of Weight Gain and Loss
Energy balance: energy intake = energy expenditure
— Positive: weight gain
— Negative: weight loss
Kilocalorie (kcal): unit of heat energy
Total Energy Expenditure (TEE)
TEE = RMR + dietary thermogenesis + EAT + NEAT
— TEE: total energy expenditure
— RMR: resting metabolic rate
— EAT: exercise activity thermogenesis
— NEAT: non-exercise activity thermogenesis
RMR is the largest contributor to TEE
Weight Management Principles
Energy balance
— Gain weight: positive energy balance
— Lose weight: negative energy balance
Combination of proper diet and daily PA
Preliminary Steps:
— Set body weight goal
Measure body composition
Use FFM and desired %BF to set a realistic goal (target weight)
— Assess kcal intake
Food record and dietary software
— Assess kcal expenditure
Factorial or TEE method
Weight Management (based on BMI, BW, %BF, FFM)
- Determine BMI, BW
- Calculate the present %BF
- Divide present FFM by %FFM goal
Define Neuromuscular fatigue (NMF)
A failure to maintain the required force during a given task;
An exercise-induced decline in maximal muscle force or power production capacity
Why do we need to study neuromuscular fatigue?
Fatigue vs. fatigability
Fatigue is used to describe a non-specific but debilitating symptom in a range of chronic diseases and disorders such as cancer
Perceived fatigability
Homeostasis
- blood glucose
- core temperature
- hydration
- neurotransmitters
- metabolites
- oxygenation
- wakefulness
Psychological state
- arousal
- executive function
- expectations
- mood
- motivation
- pain
- performance feeback
Performance fatigability
Contractile function
- calcium kinetics
- force capacity
- blood flow
- metabolism and products
Muscle activation
- voluntary activation
- activation patterns
- motor neurons
- afferent feedback
- neuromuscular propagation
Neuromotor system organization
Central nervous system (CNS)
- Brain
- Spinal cord
Peripheral nervous system (PNS)
- muscle units
Neuromuscular system: CNS
Motor planning
Motor ‘cortical’ output
Corticospinal conduction
Motoneurone pool output
Peripheral inputs:
- Motor planning
- Motor ‘cortical’ output
- Motoneurone pool output
Neuromuscular system: PNS
Motor axon conduction
Neuromuscular junction
Sarcolemma and T-tubule conduction
E-C coupling and calcium release/reuptake
Cross bridge force and ATP hydrolysis
Blood flow - energy supply
The spinal cord
1) Motor nerves (efferent)
- Pyramidal tract (voluntary movements)
- 31 pairs of spinal motor nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal)
2) Sensory nerves (afferent)
3) Interneurons
Motor Unit
Makes up the functional unit of the movements
Consists of an alpha motoneurone and the specific muscle fibres that it innervates
Difference in muscle fibre-motor unit ratio (e.g. 1:5 or 1:800) contributes to variation in motor skills
All or None principle: All of the muscle fibres innervated in a motor neuron are stimulated to contract
Neuromuscular junction (motor endplate)
Presynaptic terminal
Synaptic cleft
Postsynaptic terminal
Synaptic vesicles
Acetylcholine
Motor Units: Large motor neurons
Large motor neurones with fast conduction velocity innervate fast-fatigable (FF) and fast fatigue-resistant (FR) muscle fibres.
Motor Units: Smaller motor neurons
Smaller motor neurones with slow conduction velocity innervate slow (S) muscle fibers
Motor Units: muscle fibres
FF – type IIx muscle fibres
FR – type IIa muscle fibres
S–TypeI
Surgically innervating FF muscle fibres with the neurons from a slow-twitch muscle fibre eventually alters the twitch characteristics of FF motor unit.
