Week 9 Flashcards
(49 cards)
Factors affecting performance?
Diet:
- Carb
- Water intake
Energy production/demands:
Anaerobic: PC, Glycolysis
Aerobic: Vo2 max , CO, O2 delivery/extraction, Mitochondria, Hb, PO2
CNS Function:
- Arousal
- Motivation
Strength/skill:
- Practice
- Natural endowment such as body type and muscle fibres types.
Environment:
- Altitude
- Heat
- Humidity
Psychological components:
- Motivation and rewards
- Pressure
What is fatigue and Possible sites of fatigue?
Fatigue = Inability to maintain power output during repeated muscle contractions which is reversible with rest.
- Central fatigue (CNS involvement) - Such as neural drive or motor unit recruitment to muscles
- Peripheral fatigue - Such as neuromuscular junction, calcium release/cross bridge cycling or depletion of energy stores (neural, mechanical, and energetic factors)
Exact causes of fatigue are uncertain due to differences in context, exercises and research methods
Approaches to the study of muscle fatigue of different muscle types +/-s?
Muscle in vivo:
+ All physiological mechanisms present, all fatigue types can be studied, fatigue can be central/peripheral.
− Mixed fiber types, complex activation, hard to isolate mechanisms
Isolated muscle:
+ Central fatigue removed, simple dissection
− Mixed fibers, extracellular gradients affect fatigue(O2, CO2, K+, LA), slow drug diffusion
Isolated single fiber:
+ One fiber type, accurate ion/metabolite tracking, fast drug application
− Differs from in vivo, prone to damage, hard to analyze metabolites
Skinned fiber:
+ Precise control of solutions, study intracellular processes in isolation
− May lose key components, questionable fatigue relevance, ID metabolites externally
See diagram for more detail
What is Central fatigue? Features, factors and models?
Central fatigue is a reduction in neural drive from the CNS, leading to decreased physical performance.
Key Features:
- ↓ Motor unit activation
- ↓ Motor unit firing frequency
Influencing Factors:
- CNS arousal (e.g., music, mental focus) can delay fatigue
- Overtraining may cause chronic central fatigue
* Possibly linked to serotonin–dopamine imbalance
Theoretical Models:
- Central Governor Model (Noakes):
* Brain subconsciously limits performance to prevent harm
- Psycho-biological Model (Marcora):
* Fatigue is consciously perceived
* Effort stops when perceived exertion > motivation
Peripheral Fatigue? (Neural)
Peripheral fatigue involves neural, mechanical, and energetic factors. Neural fatigue does not originate at the neuromuscular junction.
Key neural mechanisms:
Sarcolemma and T-tubules:
- Impaired membrane excitability affects action potential conduction.
- Na⁺/K⁺ pump becomes less effective → reduced AP amplitude and frequency.
- Action potential block may occur in T-tubules.
- Leads to reduced Ca²⁺ release from the sarcoplasmic reticulum.
- Adaptable with training (improved excitability and conduction).
Note: Neuromuscular junction is not typically a limiting site in fatigue.
Peripheral Fatigue? (Mechanical)
Involves Neural, Mechanical and Energetics of contraction factors.
Cross-bridge cycling and tension development depends on:
- Arrangement of actin and myosin.
- Ca2+ binding to troponin.
- ATP availability.
High H+ Conc may contribute to fatigue:
- Reducing force per cross bridge
- Reduce the force generated at a given Ca2+ Conc
- Inhibit Ca2+ release from SR
End results in longer relaxation time, one sign of fatigue.
- Due to slower cross bridge cycling, which is importing in fast twitch fibres
Peripheral fatigue? (Energetics of contraction)
Peripheral fatigue refers to fatigue originating within the muscle itself, involving neural, mechanical, and energetic factors.
Key cause:
- An imbalance between ATP demand and supply, leading to metabolic disturbances.
Main mechanisms:
Pi (inorganic phosphate) accumulation:
- Inhibits maximal force production
- Reduces actin-myosin cross-bridge binding
- Inhibits Ca²⁺ release from the sarcoplasmic reticulum
ATP utilisation vs. generation:
- ATP use slows faster than ATP production
- Maintains ATP levels to prevent complete depletion
Muscle fibre recruitment with exercise intensity:
- Type I fibres: Up to ~40% VO₂ max
- Type IIa fibres: 40–75% VO₂ max
- Type IIx fibres: >75% VO₂ max
→ Increased lactate and H⁺ accumulation contributes to fatigue
How does free radical production during exercise contribute to muscle fatigue?
Exercise promotes production of free radicals (molecules with an unpaired electron).
These radicals can damage muscle proteins and lipids, especially during prolonged exercise (>30 minutes).
How radicals contribute to fatigue:
- Damage to contractile proteins reduces the number of cross-bridges in the strong binding state → weaker muscle contractions.
- Disrupts Na⁺/K⁺ pump activity, leading to potassium imbalance and impaired muscle excitability.
Role of antioxidants:
- Antioxidant supplements do not prevent fatigue.
- High doses can impair muscle performance and blunt training adaptations (due to reduced beneficial stress response — hormesis).
- ## N-acetyl-cysteine (a free radical scavenger) can delay but not prevent exercise-induced fatigue.
Ultra short term performances?
Events under 10 secs (high power)
Dependent on type 2 a fibres
Motivation, arousal and skill are imports at
Primary energy source is anaerobic: ATP-Pc, Glycolysis.
Creatine supplement may improve
Short term performances characteristics ? Limitation?
Duration: 10 to 180 seconds
Energy source shifts from anaerobic to aerobic:
- ~70% anaerobic at 10 sec
- ~60% aerobic at 180 sec
Primarily fueled by anaerobic glycolysis, which leads to:
- ↑ H⁺ and lactate accumulation
- H⁺ interferes with calcium (Ca²⁺) binding to troponin
- H⁺ inhibits glycolytic ATP production
Moderate Duration Performances?
Lasting 3-20 mins: 60% aerobic at 3 mins, 90% aerobic at 20.
High Vo2 max is advantageous due to high SV and O2 content (from high inspired o2 and haemoglobin)
Requires energy expenditure near Vo2 max:
Type 2x fibres recruited = high levels of lactate and H+
Intermediate duration performances? Predominant system? Important factors?
Lasting 21-60 mins
Predominantly aerobic: usually conducted at under 90% Vo2 max
High Vo2 max is important
Other important factors:
Running economy or exercise efficiency; comes from high type 1 fibre
Environment factors - heat and humidity
Hydration state
Lactate threshold
Long term performances??
Lasting 1 - 4 hours
Clearly aerobic (Vo2 max and economy is key)
Environmental factors more important than intermediate
Maintenance of carb utilisation as muscle and liver glycogen declines and ingestion of carbs to be oxidised by muscles.
Consuming fluids/electrolytes
Diet is influential to performances: high carbs
Races are not ran at 100% Vo2 max but a 2:15 marathon requires sustaining 60ml/kg/min, 75ml if at 80%
Determined by Vo2 max, running economy and lactate threshold
Ultra-endurance events?
Vary greatly, examples:
166km mountain run, Triple iron Triathlon, 24 hour run, multi day adventure races
Limit of endurance is context specific, but important factors include:
Vo2 max, %ofVo2 max sustained
Metabolic responses:
Marked increase in fat ox, consistent with exercise under 60% VO2 max
50% reduction in muscle glycogen
Potential fort hypnoatremia - only affects 4% of athletes
Non physiological factors can end performances too such as foot state management
Training principles?
Training programme should match anaerobic and aerobic demands of the sport.
- Specificity: Training must target the specific muscles and energy systems used in the sport.
- Overload: Increase workload to challenge the body, leading to adaptation. Too much causes overtraining.
- Rest and Recovery: Crucial for optimal adaptation and injury prevention.
- Reversibility: Training effects diminish without continued training.
Influence of Sex and Fitness Level?
- Males and females respond similarly to training programs
- Training should however be prescribed per individual (separate ‘training for specific populations’ video)
- Low fitness levels show greater training improvements
- VO2 max - 50% ^ in sedentary adults, 10-20% in normal active and 3-5% in athletes
Any difference can be important
Aerobic and Anaerobic Energy Systems?
- Different sports utilize varying contributions from the ATP-PC system, glycolysis, and aerobic metabolism.
- Examples: 100m sprint (98% ATP-PC), marathon (98% aerobic), Golf swing (100% ATP-PC), Field hockey (60% ATP-PC, 20% Glycolysis and Aerobic)
Laboratory Tests To Quantify Endurance Exercise Potential?
VO2 max training approaches are founded on a few key laboratory tests:
- Lactate threshold: incremental intensity test with
blood samples for lactate.- “Breakpoint” for lactate accumulation identified
- Ventilatory threshold: ventilatory response to
incremental work produces increased slope.- Ventilatory “breakpoint” identified.
- Critical power: a submaximal power output that
can be maintained for indefinite periods. - Exercise economy: metabolic and mechanical
factors influencing movement economy
Influence of Genetics on Aerboic capacity amd Training response? Responders?
- Genetic factors significantly influence aerobic capacity and training response.
- Big factor is muscle fibre types.
- 3 key elements of aerobic performance:
- High Vo2 max
- Superior exercise efficiency
- High lactate threshold and critical power
- Low responders. (i.e. genotype A”).
- Possess a relatively low untrained VO2 max.
- Often exhibit limited exercise training response, as
VO2 max improves by 5% or less.
- High responders. (i.e. “genotype E”)
- Individuals with the ideal genetic makeup required
for champion endurance athletes. - Possess a relatively high untrained VO2 max.
- Often increase VO2 max by 50% with training.
- Individuals with the ideal genetic makeup required
Training session components?
- Warm up
- Increase in CO and blood flow to muscles
- Increase in uncle temp and enzyme activity
- Reduce risk of exercise induced injury
- Workout
- Trining session: Aerobic-Power, Anaerobic-Power, Muscular strength
- Cool down
- Return blood pooled in muscles and central circulation
Measurement of peak running velocity for improved Performance?
Definition:
- Peak running velocity (V̇peak) = highest speed that can be maintained for ≥5 seconds (often assessed over 60 seconds).
Importance:
- Strong inverse correlation with endurance race finish times (i.e., higher V̇peak = faster race time).
Accounts for a large portion of training-related performance improvements:
- ~80% for shorter distances (e.g., 5 km)
- ~40% for marathons
Application:
- Useful for tailoring training intensities and improving race outcomes.
Training methods to improve Aerobic power? What does it aim to improve?
Training Types:
- Interval Training – Alternating high and low intensity efforts.
- Long, Slow Distance (LSD) – Sustained moderate-intensity exercise.
- High-Intensity Interval Training (HIIT) – Short bursts at near-max effort.
Aims to Improve:
- VO₂ max – Maximal oxygen uptake.
- Lactate Threshold – Higher intensity before lactate builds.
- Running Economy – More ATP produced per unit of oxygen
HITT/Interval training? Characterised by? Benefits?
- Popularised 70+ years ago by Roger Bannister who broke 4min mile record in 1954, now popular for health promotion: effective and time saving
- Characterised by:
- Repeated HI exercise bouts followed by brief recovery e.g. 1:1 = 60 seconds work 60 seconds rest
- Work interval
- Duration - secs
- Intensity - usually 85+ max HR
- Rest intervals (lighter activity e.g walking)
- Sets and Reps, e.g. 2 sets of 8 x 400m
- Training outcomes of HITT
- Improved VO2 max, running economy, and lactate threshold better than low-intensity intervals..
- As little as 30 seconds of high-intensity exercise promotes adaptations.
- Increases mitochondrial volume.
Long, Slow Distance (LSD)?
- Low-intensity training (60-70% max H, 50-65% Vo2 max) focused on endurance.
- Popular in 1970s
- Training duration is usually greater than event/comp duration
- Improvements are based on volume of training
- Targets the aerobic base – underpins many performance demands
- However, short-term, high-intensity training is better for improving VO2 max
