FINAL EXAM Flashcards
Define Neuromuscular fatigue
A failure to maintain the required force during a given task;
An exercise-induced decline in maximal muscle force or power production capacity
Perceived vs. performance fatiguability
Fatigue is used to describe a non-specific but debilitating symptom in a range of chronic diseases and disorders such as cancer
Perceived fatiguability
- homeostasis
- psychological state
Performance fatiguability
- contractile function
- muscle activation
Components of the neuromuscular system
Central NS:
- Motor planning
- Motor ‘cortical’ output
- corticospinal conduction
- motoneurone pool output
Peripheral NS:
- motor axon conduction
- Neuromuscular junction
- sarcolemma and T-tubule conduction
- E-C coupling and calcium release/reuptake
- Cross bridge force and ATP hydrolysis
Motor unit
Makes up the functional unit of the movements
Consists of an alpha motoneurone and the specific muscle fibers that it innervates
Difference in muscle fiber-motor unit ratio (e.g. 1:5 or 1:800) contributes to variation in motor skills
All or None principle: All of the muscle fibers innervated in a motor neuron are stimulated to contract
Neuromuscular junction (Motor endplate)
Presynaptic terminal
Synaptic cleft
Postsynaptic terminal
Synaptic vesicles
Acetylcholine
Process of sliding filament theory
- Myosin heads split ATP and become reoriented and energized
- Myosin heads bind to actin, forming cross bridges
- Myosin cross bridges rotate toward centre of the sarcomere (power stroke)
- As myosin heads bind ATP, the cross bridges detach from actin
contraction cycle continues if ATP is available and Ca2+ level in the sarcoplasm is high
Process of muscle contraction
Motor unit sizes and characteristics
Large motor neurones with fast conduction velocity innervate fast-fatigable (FF) and fast fatigue-resistant (FR) muscle fibers.
Smaller motor neurones with slow conduction velocity innervate slow (S) muscle fibers
FF – type IIx muscle fibers
FR – type IIa muscle fibers
S–Type I
Surgically innervating FF muscle fibers with the neurons from a slow-twitch muscle fiber eventually alters the twitch characteristics of FF motor unit.
Central vs Peripheral fatigue
Central fatigue:
With exercise, metabolites activate sensory afferent neurones (group III/IV afferent) which in return convey pain- and fatigue-related sensory signals to the brain
- The brain region related to fatigue and pain sensations will be activated and the brain sends fewer voluntary motor signals to the skeletal muscles
Peripheral fatigue:
- muscle fatigue after exercise
Higher intensity exercises (short duration) result in more peripheral fatigue
Lower intensity exercise (longer duration) result in more central fatigue
Components of maximal voluntary activation (MVC):
SIT (Superimposed twitch)
= relies on the twitch force added by a supramaximal motor nerve stimulus during a voluntary contraction
Resting Twitch
= A first stimulus delivered with the muscle fully relaxed
How do we measure MVC?
Twitch Interpolation technique
The amount (grams) of glycogen and glucose in the liver, muscle and blood
Liver glycogen - 110g
Muscle glycogen - 500g
Glucose in the blood and cell - 15g
The process of oxygen delivery
The respiratory system ensures the delivery of oxygen from the environment into the alveoli and the bloodstream and the elimination of carbon dioxide from the blood into the alveoli and the environment (gas exchange).
The oxygenated arterial blood is pumped by the heart to the mitochondria of the skeletal muscles.
The process of oxygen diffusion
Gas exchange between the alveoli in the lung and the pulmonary capillary blood and the capillary blood and the mitochondria of the skeletal muscles is driven by gas (oxygen and carbon dioxide) pressure differences (diffusion)
The process of oxygen perfusion
Functionally, the heart is two separate pumps:
Right side:
— Atrium receives deoxygenated blood from body
— Ventricle pumps deoxygenated blood to lungs
Left side:
— Atrium receives oxygenated blood from lungs
— Ventricle pumps oxygenated blood to body
The process of oxygen of gas exchange
Exchange of gases (O2 and CO2):
— O2 is moved from the environment to the mitochondria
— CO2 is moved from the mitochondria to the environment
What is the contribution of hemoglobin in oxygen transfer?
Oxygen is carried in two forms
- Dissolved in the fluid of blood
— Very little O2 is transported in solution (Poor solubility)
~4% of O2 consumption at rest
Oxygen transport in blood - Bound to hemoglobin
— Responsible for majority of blood transport
- Each hemoglobin can bind 4 O2 molecules
~96% of O2 consumption at rest
Oxygen-carrying capacity of hemoglobin (mL O2/L blood)
— Hemoglobin concentration (g/L blood)
— Oxygen capacity of hemoglobin (mL O2/g)
- 1.34 mL O2/g
The effect of training on mitochondrial content and volume density
Mitochondria density is increased by training:
1 month of training
— 2 hours/day, every day
— Increased mitochondrial volume density (electron microscopy)
What is cardiorespiratory fitness?
The measure of an individual’s peak/maximal capacity to perform
CR fitness depends on the synergistic working of organ systems that deliver oxygen from the ambient air to the mitochondria, while effectively removing metabolic byproducts.
How do we measure cardiorespiratory fitness?
Graded exercise tests (GXTs)
— Laboratory or clinical tests
— Field test
What are the parameters determining cardiac output and VO2max?
Heart rate
— Maximal heart rate: Highest heart rate for a person, related primarily to age
Stroke volume: The volume of blood pumped during one beat of the heart
— Increases significantly with endurance training
Amount of oxygen removed from the blood
— Arterial-venous oxygen difference: Amount of oxygen removed from the vascular system
What is the effect of aging on cardiorespiratory fitness?
After 30 years of age, VO2 max progressively decreases with age at a rate of about 10% per decade
What is the effect of exercise on the prevention of VO2max decline?
Aerobic exercise decelerate aging effect on VO2Max:
VO2max can improve at any age with regular endurance training by approximately 15– 20%, depending on exercise intensity.
Accordingly, it is possible that a trained 70- year-old can exhibit the biological age of an untrained 50-year
— Despite declines at about 7% (women) to 10% (men) per decade from the age of 30
Men demonstrate a greater absolute decline in VO2 max with age compared with women
Endurance-trained adults reveal less decline in VO2 max with advancing age compared with healthy sedentary adults.
CSEP exercise prescription guidelines based on HRR, RPE, talk test
Knowing the approximate range of each exercise intensity for HRR and RPE column in slide 18 could be helpful
Approximate range of HRR for each exercise intensity:
very light = < 30 HRR
light = 30-39 HRR
moderate = 40-59 HRR
vigorous = 60-89 HRR
near maximal to maximal = >/= 90 HRR
What is the difference between HRR and HRmax
Heart rate reserve (HRR):
HRR = HR max – resting HR
- e.g., 179 – 54 = 125
HRmax
HRmax = [220 - Age]
What are the exercise intensity thresholds?
Gas exchange threshold (GET)
Respiratory compensation point (RCP)
What are the exercise intensity domains?
Severe:
- [La] and VO2 are unstable and project to maximal values (Above RCP)
Heavy:
- increased but stable [La] and VO2. Development of VO2 (Above GET but below RCP)
Moderate:
- no increase in [La] and stable VO2 (below GET)
*La = lactate
How do we determine exercise intensity thresholds?
The rate of blood lactate/H+ production vs. clearance and associated cardiopulmonary responses determine the thresholds
The three phases of exercise are determined based on the two thresholds (GET and RCP)
What is the energy supply in each domain?
Predominant pathways for producing ATP in each phase (domain)
Phase 1: Fat oxidation
Phase 2: A combination of fat oxidation, aerobic glycolysis and glycogenolysis
Phase 3: Anaerobic glycolysis and glycogenolysis
Physiological characteristics of each domain (i.e., slide 5). You just need to know the appropriate range of values such as lactate, RPE and HRR
Phase I: very light exercise
- 1st lactate threshold, “aerobic threshold” 40-60% of VO2max
- Borg scale 6-9 RPE
- 45-55% of VO2max or HRR
Phase II: light & moderate exercise
- light exercise = 1st lactate threshold
- moderate exercise = 2nd lactate threshold
- Borg scale 10-12 RPE
- 55-70% of VO2max or HRR
Phase III: heavy exercise
- 2nd lactate threshold, “anaerobic threshold” 60-90% of VO2max
- Borg scale >14 RPE
- >80% of VO2max or HRR
What is the importance of knowing the exercise intensity domains?
The concept of thresholds is applicable to exercising prescription
How long can we sustain exercise in each intensity domain (approximately though)?
Exercise tolerance across the domains
Moderate
- >2 hours
Heavy
- 45 min to >2 hours
Severe
- seconds to ~45 min
- hyperbolic relationship
What are the different types of stretching?
Static stretching (SS)
Dynamic stretching (DS)
Ballistic (bouncing) stretching (BS)
Proprioceptive Neuromuscular Facilitation (PNF)
The contribution of the muscle spindle in the determination of acute (short-term) and chronic (long-term) flexibility
Short-term flexibility:
- Static stretching (SS)
- Activation of muscle spindle = increased muscle activation
Stretching muscle spindles increases the firing frequency of alpha motor neurones innervating the muscle. This reflexive loop will increase tension (i.e., contraction intensity) in the muscle
However, if a muscle is stretching to the point of discomfort, then activation of muscle spindles will decrease to reduce tension in the muscle. This is a protective mechanism to prevent muscle damage.
Reduced muscle spindle activation occurred after every single flexibility exercise session can provide an acute increase in flexibility.
Some researchers say:
that reduced muscle spindle activation can become chronic and this will facilitate long-term improvement in flexibility.
The contribution of the Golgi tendon organ (GTO) in the determination of acute (short-term) and chronic (long-term) flexibility
Long-term flexibility:
- Activation of GTO = decreased muscle activation
The sequence of stretch-contraction-stretch activates a cascade of phenomena that improves flexibility significantly:
- 1st Stretch: deactivates muscle spindles, improves viscoelastic deformation, and increases pain tolerance
- Contraction: activates GTOs and reduces tension in the muscle
- 2nd stretch: further deactivates muscle spindles, improves viscoelastic deformation, and increases pain tolerance
What are the most and least effective modes of stretching and why?
Ballistic (bouncing) stretching (BS) is the least effective flexibility exercise mode:
- Bouncing is using momentum in an attempt to exceed the normal ROM which can induce bouncing motions at the end of ROM
Proprioceptive Neuromuscular Facilitation (PNF) is one of the most effective methods of improving flexibility:
- PNF incorporates an isometric contraction followed by a SS.
- Stretch - contract - stretch (SCS)
What are the components of endurance exercise prescription: (i.e., FITT-VP principle)
FITT-VP principle:
Frequency
Intensity
Time
Type
Volume
Progression
How much is the volume of exercise prescribed for the general population?
20 to 60 min per session
— Depends on intensity
Minimum single bout duration = 10 min continuous
Accumulate 30 min MIPA per day or 20 min VIPA per day
Combination of MIPA and VIPA for 3 to 5 days per wk recommended
What is the relationship between exercise frequency and VO2max improvement?
As frequency increases so does VO2max
(graph with an upward slope)
How much is optimal endurance exercise duration?
20 to 60 min continuous or intermittent activity per day recommended
Cardiorespiratory function improves with MIPA lasting 30-60 min
Can add 5-10 min to session duration every other week until goal met
What is the relationship between exercise intensity and duration?
Exercise duration is inversely related to the intensity
What factors determine the volume of endurance exercise?
Volume = frequency * duration
The difference between HIIT and constant load exercise
HIIT is characterized by brief, intermittent bursts of vigorous activity, interspersed by periods of rest or low- intensity exercise
The benefits of HIIIT for general population?
Similar adaptations were found between the two modes of exercise for:
— Increased skeletal muscle oxidative capacity
— Increased resting glycogen content,
— Reduced rate of glycogen utilization and lactate production
— Increased capacity for whole-body and skeletal muscle lipid oxidation,
— Enhanced peripheral vascular structure and function,
— Improved exercise performance as measured by time-to-exhaustion tests
— Increased maximal oxygen uptake
The benefits of HIIIT for people with cardiovascular diseases?
Interval training provides an effective means to improve the cardiovascular fitness and health status of highly functional patients with coronary artery disease
interval training improves anaerobic tolerance to a greater extent than the traditional exercise training model without increasing the risk to the patient
The benefits of HIIIT for people with metabolic diseases?
Increased maximal activity of citrate synthase (CS) measured in skeletal muscles before and after 2 wk of training
Increased GLUT4 protein content in skeletal muscles obtained before and after training.
