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Questions and Answers
What is the primary role of bicarbonate in buffering during intense exercise?
Which intracellular buffer is primarily responsible for buffering H+ in muscle?
In conditions of high intensity exercise, what physiological factor may limit performance for some athletes?
How much improvement in VO2max can the average person expect from appropriate training?
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Which type of genetic responder is characterized by a low, untrained VO2max and limited exercise training response?
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What factor increases the likelihood of respiratory fatigue during prolonged bouts of high-intensity exercise?
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Which extracellular buffer plays a major role in buffering H+ in the blood?
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What percentage of improvements can high responders with ideal genetic makeup expect in VO2max with training?
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Which of the following factors is NOT considered when deciding which physiological capacity to test?
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What does VO2max estimate in the context of aerobic capacity?
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Which indicator is NOT a sign of maximal effort in achieving VO2max?
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What does assessing anaerobic capacity focus on?
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In endurance sports, when may VO2max not be the best predictor of performance?
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What is the main difference between VO2max and VO2peak?
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Which of the following components is NOT considered a measure of muscle strength?
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What best describes 'work above critical power' in the context of anaerobic testing?
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What primarily contributes to differences in VO2max among individuals?
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Which training method can effectively increase VO2max?
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What can prolonged inactivity lead to regarding muscle size?
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What factor is NOT a component of the Fick Equation used to define VO2max?
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What physiological adaptation occurs with long-duration training that contributes to increased VO2max?
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Which aspect of cardiac function primarily affects afterload?
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What is the primary reason for rapid strength loss following cessation of strength training?
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Which mechanism is primarily responsible for conservation of muscle mass during training?
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Hypertrophy leads to increased cross-sectional area of a muscle fiber.
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Hyperplasia is well-documented to occur in humans as a result of training.
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Muscle antioxidant capacity increases significantly after 12 weeks of training.
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Muscle fibre type shifts from slow to fast fibres during resistance training.
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Increased muscle mass can be detected within 3 weeks after starting resistance training.
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What is the normal pH level in the body?
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How do type 2 muscle fibers affect buffering capacity during exercise?
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What effect does high intensity exercise for about 45 seconds have on H+ production?
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What is a potential side effect of supplementing with sodium bicarbonate?
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What role do the kidneys play in acid-base balance during exercise?
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What role does VO2max play in performance during moderate-length exercises?
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Explain how environmental factors affect long-term aerobic performance.
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How does the proportion of type 1 muscle fibers relate to running economy?
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What is the impact of carbohydrate ingestion during long-duration exercise?
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Describe the significance of lactate threshold in intermediate performances.
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Study Notes
Acid Base Balance
- Buffers release H+ when pH is high
- Buffers accept H+ when pH is low
Intracellular Buffers
- Proteins, phosphate groups, bicarbonate, histidine-dipeptides
- All work collectively
Extracellular Buffers
- Bicarbonate
- Supplementation has shown some improvements in some sports
- Haemoglobin
- Blood proteins
Muscle Buffering
- 60% of H+ buffered by intracellular proteins
- 20-30% of H+ buffered by muscle bicarbonate
- 10-20% of H+ buffered by intracellular phosphate groups
Lactic Acid Buffering in Blood
- Bicarbonate is the major buffer
- Increases in blood lactic acid are accompanied by decreases in bicarbonate and blood pH
- Haemoglobin and blood proteins play a minor role
Pulmonary Function and Performance
- Role of pulmonary function in exercise performance is not clear
- The pulmonary system does not limit exercise tolerance in low to moderate intensity exercise
- The pulmonary system does not limit exercise tolerance in high intensity exercise for healthy people at sea level.
- Respiratory fatigue can occur during high intensity exercise at 90-100% VO2max levels in prolonged bouts of high intensity.
- Fatigue is due to the fatigue of the respiratory muscles
- Incomplete pulmonary gas exchange can limit athletes in some performances
Genetic Limitations
- Genetics play a role in determining training response
- Some individuals are naturally more athletic than others
- 97 different genes contribute to training improvements and VO2max responses
- Average person improves VO2max by 15-20%
- High responders can improve VO2max by up to 50% with appropriate training
- Low responders may only see a 2-3% improvement
- Anaerobic capacity is more genetically determined than aerobic capacity
- Training can only improve anaerobic performance to a small degree
- Genetics play a role in high VO2max, superior exercise economy, lactate threshold and critical power
Genotypes and VO2max
- Genotype A: Low, untrained VO2max, limited exercise training response
- Genotype E: Ideal genetic make-up, high untrained VO2max, often increase VO2max by 50% with training
Physiological Capacities Tested
- Aerobic Endurance
- Max capacity
- Max sustainable aerobic power
- Anaerobic/Sprint
- Peak power
- Mean max power
- Work above critical power (total amount of anaerobic energy expenditure above max sustained aerobic)
- Repeat sprint capacity-consistency
- Muscle strength and power
- Max force production capabilities of a muscle
- Max dynamic strength
- "Speed-strength" or power (combination of force and velocity)
- Strength endurance (consistency)
Factors to Consider When Choosing Capacities to Test
- Feasibility of the test
- Availability of equipment
- Whether the test replicates the sport, or is closely related
- Repeatability of the test
Aerobic Endurance Capacity and VO2max
- Aerobic capacity is predictive of endurance capacity
- VO2max is often used to test aerobic capacity, but depends on the event
- VO2max can often predict aerobic capacity
- In elite sport VO2max is not always the best predictor of aerobic capacity
- VO2max is not the best predictor for longer duration aerobic events, where the athlete isn't hitting their VO2max
- Incremental exercise tests are not looking for a peak value, they are looking for exercise intensity where max sustainable aerobic power is achieved
- VO2max and max aerobic capacity are different
Max Aerobic Capacity
- VO2max can only be reported if evidence exists that the athlete produced max effort
- Signs of max effort: HRmax, RER, lactate above 7.0 mmol/l, plateau in oxygen consumption despite an increase in exercise intensity
- If there is no evidence of max effort, it should be reported as VO2 peak
- Incremental test to exhaustion (treadmill, bike, ramp test) are used to test VO2max
- Future testing involves letting the athlete recover after a normal test protocol, then get them to work for a minute at their highest power output
Detraining Following Strength Training
- Any RT program cessation leads to atrophy and loss of strength
- Strength losses occur slower than endurance-based adaptations
- Strength loss can be recovered quickly (within 6 weeks) upon returning to training
Muscle Memory
- A gym myth: after a prolonged period of no training, rapid gains can be made during retraining because of "muscle memory"
- Research suggests that RT induced increases in myonuclei in trained fibers are not lost during detraining, and this gives an edge in protein synthesis upon retraining
Prolonged Inactivity and Muscle Atrophy
- 20-30 days of inactivity can lead to a 20-30% reduction in muscle fiber size
- Conservation of muscle mass is dependent on the balance between MPS and MPB
- Increases in radial production promotes muscle atrophy
Training and Changes in VO2max
- VO2max: the measure of the maximal capacity of the body to transport and use oxygen during dynamic exercise using large muscle groups
- VO2max: max cardiac output x a-vO2 difference
- The primary difference in VO2max between people is stroke volume
Training to Increase VO2max
- Training large muscle groups
- Endurance based activity above 50% VO2max 3+ times per week
- HIIT can also increase VO2max
Responses to Increases in VO2max
- 15-20% increase in general population
- Smaller increases in individuals with already high VO2max
- Up to 50% increase in individuals starting with very low VO2max
- Short duration adaptations are likely due to increases in volume
- Long duration adaptations are changes to stroke volume and a-vO2 differences
Factors Influencing Stroke Volume
- TPR (afterload), contractility, EDV (preload)
- EDV is made up of plasma volume, filling time, venous return, and ventricular volume
- Preload increases and afterload decreases with changes to stroke volume
Muscle Mass Increases from Training
- Hyperplasia: increase in a total number of fibers in muscle, but there is no evidence to support this occurs in humans
- Hypertrophy: increased CSA of a muscle fiber, the dominant factor in resistance training changes in muscle mass.
Physiological Changes in Response to Resistance Training
- Increased neural drive, possible changes in ratio of agonist/antagonist activation. Adaptations occur rapidly after initiation of training program
- Increased muscle mass. Hypertrophy is detectable within 3 weeks after initiation of training. It is unclear if hyperplasia occurs in humans
- Increased specific force production in type 1 fibers only.
- Shift from fast to slow fibers. Small shift from type 2x to 2a with no evidence of % type 1 fibers increasing.
- Muscle oxidative capacity unclear. Increases in muscle oxidative capacity are possible, but depend on the type of resistance training performed
- Muscle capillary density unclear. Training adaptation is possible, but depends upon the type of training being performed
- Increased muscle antioxidant capacity. 12 weeks of training increases antioxidant enzyme activity by almost 100%.
- Increased tendon and ligament strength. Harmonised increase in tendon/ligament strength to match increases in muscle strength
- Increased bone mineral content. Results in stronger bones.
Factors Affecting Anaerobic Performance
- All-out performances fall into one of two categories: ultra short term (less than 10 seconds) and short term (10-180 seconds).
- Ultra Short Term: events are less than 10 seconds. They are dependent on type 2 muscle fibers, require a large amount of force, and are influenced by motivation, skill, and arousal. Primary energy systems are ATP-PC and glycolysis, with a focus on phosphocreatine. Creatine supplements may improve performance. Fibre type distribution and recruitment are important for performance.
- Short Term events last between 10 to 180 seconds. There is a shift to aerobic metabolism, with 70% of energy supplied anaerobically at 10 seconds and 60% supplied aerobically at 180 seconds. Primarily fueled by anaerobic glycolysis, resulting in elevated lactate and hydrogen ion levels.
Detraining Following Strength Training
- Ceasing any RT program leads to a degree of atrophy and loss of strength.
- Strength losses occur slower than endurance-based adaptations.
- Recovering strength loss can occur quite fast, within 6 weeks, of returning to training.
- Muscle memory is controversial, but research suggests it is due to RT-induced increases in myonuclei in the trained fibers that are not lost during detraining. Maintaining these myonuclei gives an edge in protein synthesis upon retraining.
Prolonged Inactivity Leads to Rapid Atrophy
- 20-30 days of inactivity can lead to a 20-30% reduction in muscle fiber size.
- Conservation of muscle mass is dependent on the balance between MPS and MPB.
- Increased radial production promotes muscle atrophy.
Training and Changes in VO2Max
- VO2max: the maximal capacity of the body to transport and use oxygen during dynamic exercise using large muscle groups.
- It is defined by the Fick Equation: VO2max = max cardiac output X a-vO2 difference.
- The primary difference in VO2max between people is stroke volume.
Training to Increase VO2Max
- Training large muscle groups.
- Working out 3+ times per week, endurance-based activity above 50% VO2 max.
- HIIT can increase VO2max as well.
Responses to Increases in VO2Max
- 15-20% increase in the general population.
- Smaller increases will occur in those with an already high VO2max.
- Up to 50% increase in those with very low VO2max.
- Short duration adaptations are likely due to increases in volume. Long duration responses are changes to stroke volume and a-vO2 differences.
Factors Influencing Stroke Volume
- TPR (afterload), contractility, and EDV (preload).
- EDV is made up of plasma volume, filling time, venous return, and ventricular volume.
- Preload will increase, and then afterload will decrease with changes.
Muscle Adaptations To Anaerobic Exercises
- Anaerobic training intensities are done above VO2max and fueled primarily by the ATP-PC and glycolysis systems. Adaptations from this system are different to that of endurance training.
- 10-30 second effort, recruits both type 1 and 2 fibers. Exercise lasting less than 10 seconds is fueled by the ATP-PC system
- Exercise that is 20-30 seconds, 80% of energy is needed anaerobically and the remaining 20% is aerobic.
- Adaptations include: better buffering capacity, hypertrophy of type 2 fibers, elevates enzymes involved in both the ATP-PC system and glycolysis.
- HIIT training greater than 30 seconds, promotes mitochondrial biogenesis.
- 4-10 weeks of anaerobic training can increase the peak anaerobic capacity by 3-25% across individuals.
Training - Muscle and Systemic Physiology
- Biochemical adaptations to training influence physical responses. Eg: changes to epinephrine/norepinephrine has an impact on HR and ventilation.
- Peripheral feedback from skeletal muscle to then go to the CNS: training leads to improved muscle homeostasis during exercise and reduced feedback from the muscle chemoreceptors to the CV control center. Less feedback from the group 3 and 4 fibers of the CV center means less work is required from the CNS = lower HR, ventilation, etc.
- Central control of the physiological response to exercise: endurance exercise training reduces the feed-forward output from the higher brain centers to the CV control center during submaximal exercise. When exercise adaptations occur there are improvements in muscle fiber oxidative capacity and reduced central command outflow during submax exercise.
Training Considerations
- Optimizing athlete training is important because they spend more time training than competing.
- Entering sessions with low glycogen promotes adaptations = increased protein synthesis and mitochondria formation.
- To induce a low muscle glycogen level: restrict dietary carbs or train twice per day every other day.
- Restricting dietary intake can lead to chronic fatigue and training impairments.
- Protein availability and MPS are very important for endurance. Ingesting protein increases MPS, can be consumed pre or post session.
Supplementation with Mega Doses of Antioxidants
- Exercise promotes formation of free radicals that may damage cells and contribute to fatigue.
- Antioxidants may help prevent/limit damage and fatigue.
- High doses of antioxidants may block training adaptations.
Common Training Mistakes
- Overtraining: workouts that are too long or strenuous, inadequate recovery, may result in injury, impair immune function, can lead to psychological staleness.
- Undertraining: not adequately stimulating the physiological responses in the body.
- Performing nonspecific exercises: won't enhance energy capacities used in the sport.
- Lack of long term training plan: misuse of training time, won't see ongoing adaptations.
- Failure to taper before a performance: athletes won't have their optimal performance levels, may have residual fatigue.
Factors Limiting All-Out Aerobic Performances
- Energy fueling bouts of exercise lasting longer than 3 minutes comes from aerobic sources. These bouts are heavily influenced by environmental and dietary factors that can cause fatigue.
- Exercise duration is categorized into three groups: Moderate (3-20 minutes), Intermediate (21-60 minutes), and Long Term (1-4 hours).
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Moderate duration exercise (3-20 minutes):
- 60% of ATP is generated aerobically at 3 minutes, increasing to 90% at 20 minutes.
- High VO2max is beneficial.
- High stroke volume and arterial oxygen content are crucial.
- Exercise near VO2max recruits type 2 fibers in addition to type 1 fibers, leading to a buildup of byproducts.
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Intermediate duration exercise (21-60 minutes):
- Primarily aerobic.
- Performed just below 90% VO2max.
- High VO2max is important.
- High percentage of type 1 fibers is advantageous for running economy.
- Environmental factors (heat, humidity, hydration status, lactate threshold) play a significant role.
- VO2max and running economy are key indicators of performance.
- Biomechanics and bioenergetics influence running economy.
- A high proportion of type 1 fibers leads to a higher lactate threshold.
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Long duration exercise (1-4 hours):
- Relies solely on aerobic fuel.
- Environmental factors are more impactful.
- Maintaining carbohydrate utilization is vital.
- Muscle and liver glycogen stores deplete, requiring carbohydrate ingestion to maintain carbohydrate oxidation.
- Fluid and electrolyte consumption are crucial.
- Dehydration can lead to hyponatremia (low blood sodium levels).
- Diet plays a role in performance.
Acid Base Balance
- pH (hydrogen ion concentration) is a measure of acidity in the body, with a normal level of 7.4.
- Abnormal pH levels can disrupt enzymatic reactions, affecting physiological function and performance.
- Acids release H+ ions, increasing their concentration (e.g., lactic acid).
- Bases combine with H+ ions, decreasing their concentration (e.g., bicarbonate).
- High-intensity exercise for 45 seconds or more produces significant amounts of H+ ions.
- Sports with intense finishes (e.g., distance/endurance events) have a higher risk of acid-base disturbance (acidosis).
- Acidosis can impair performance.
- Failure to maintain acid-base homeostasis can hinder ATP production and interfere with calcium binding.
- Type 2 fibers have a higher muscle buffering capacity, allowing for better handling of H+ ions.
- Diets low in acids can lower plasma pH but don't affect buffering capacity.
- Sodium bicarbonate supplementation can improve performance but can cause nausea, vomiting, and alkalosis (high blood pH) in large doses.
- Sodium citrate supplementation enhances extracellular buffering capacity and can improve performance during high-intensity exercise. Large doses have similar effects to bicarbonate.
- Beta-alanine supplementation, a precursor to carnosine, increases intracellular buffering capacity and can extend time to exhaustion during high-intensity exercise. Its only known side effect is skin tingling.
- H+ production during exercise is dependent on intensity, muscle mass involved, and duration.
- Blood pH decreases as exercise intensity rises, while muscle pH exhibits a greater decline and is lower than blood pH.
- While kidneys regulate acid-base balance long term, their impact during exercise is minimal.
Sources of H+ During Exercise
- CO2 production: End product of oxidative phosphorylation.
- Lactic acid production: Glucose metabolism through glycolysis.
- ATP breakdown during muscle contraction: Releases H+ ions.
Sources of H+ in Contracting Skeletal Muscles
- Aerobic metabolism: Produces carbonic acid.
- Anaerobic metabolism: Produces lactate.
Acid-Base Buffer Systems
- Bicarbonate Buffer System: Acts in the blood and extracellular fluids, rapidly binding H+ ions.
- Phosphate Buffer System: Found in the intracellular fluids, buffer pH changes within cells.
- Protein Buffer System: Proteins in the blood and muscle can act as buffers, binding H+ ions.
Resistance Training Adaptations and Performance
Resistance Training Promotes Changes in the Nervous System
- Neural adaptations play a significant role in increasing muscular strength.
- Neural adaptations are crucial in the early stages of training (2-8 weeks).
- Untrained individuals experience strength gains of 10-80% in the first 6 months of training, primarily due to neurological adaptations.
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Evidence for neural adaptations in the first 8 weeks:
- Strength increases without changes in muscle fiber size.
- Cross-education training of one limb results in increased strength in the untrained limb.
- Exact mechanisms of neural drive increase are unclear and inconclusive.
- Some studies suggest that resistance training lowers inhibition in the motor cortex and spinal cord.
- Before training, antagonist muscle contraction is high. Maximum force production is optimized when agonist muscle activation isn't paired with antagonist co-activation.
Neural Steps Leading to Muscular Contraction
- Higher brain centers initiate the muscular contraction process.
- Neural message is relayed to the motor cortex.
- Message is transmitted to the brainstem and then to the spinal cord.
- In the spinal cord, excitatory neural signals depolarize motor neurons.
- Depolarization waves travel down the axon to muscle fibers within the motor unit.
Neural Adaptations
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Increased neural drive leads to:*
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Increased number of motor units recruited.
-
Increased firing rate of motor units.
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Increased synchronization of motor unit activity.
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Improved neural transmission at the neuromuscular junction.
Resistance Training Induced Changes in Muscle Structure and Function
- RT promotes increased muscle fiber-specific tension in type 1 fibers.
- Type 2 fibers produce more force due to a higher concentration of myosin and cross-bridges.
- Increased muscle fiber-specific tension in type 1 fibers is linked to enhanced calcium sensitivity, leading to increased cross-bridge binding with actin.
Detraining Following Strength Training
- Ceasing resistance training leads to muscle atrophy and strength loss.
- Strength loss occurs more slowly than endurance-based adaptations.
- Strength recovery upon returning to training is relatively quick (within 6 weeks).
Muscle Memory
- The concept of "muscle memory" is debated.
- Research suggests that RT-induced increases in myonuclei within trained fibers are not lost during detraining.
- Preservation of these myonuclei may contribute to faster protein synthesis upon retraining.
Prolonged Inactivity and Muscle Atrophy
- 20-30 days of inactivity can lead to a 20-30% reduction in muscle fiber size.
- Maintaining muscle mass depends on the balance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB).
- Increased protein breakdown promotes muscle atrophy.
Aerobic and Anaerobic Training Adaptations and Performance
Training and Changes in VO2max
- VO2max measures the body's maximum oxygen uptake capacity during strenuous exercise using large muscle groups.
- VO2max is determined by the Fick Equation: VO2max = Maximum Cardiac Output x Arteriovenous Oxygen Difference.
- The primary difference in VO2max between individuals is stroke volume.
Training to Increase VO2max
- Training large muscle groups.
- Endurance-based activity above 50% VO2max, 3+ times per week.
- High-intensity interval training (HIIT) can also increase VO2max.
Responses to Increases in VO2max
- General population experiences a 15-20% increase.
- Smaller increases occur in individuals with already high VO2max.
- Up to 50% increase can be seen in those with very low VO2max.
- Short-term adaptations primarily involve increases in volume, while long-term adaptations focus on changes in stroke volume and arteriovenous oxygen difference.
Factors Influencing Stroke Volume
- Total peripheral resistance (afterload), contractility, and end-diastolic volume (preload).
- EDV is influenced by plasma volume, filling time, venous return, and ventricular volume.
Low Muscle Glycogen and Adaptions
- Entering training sessions with low muscle glycogen promotes adaptations (increased protein synthesis, mitochondria formation).
- Low muscle glycogen triggers higher activation of PGC-1α (mitochondrial biogenesis regulator).
- Low muscle glycogen leads to greater stimulation of AMPK and p38, upstream promoters of PGC-1α activation.
- To induce low muscle glycogen levels, either restrict dietary carbs or train twice a day, every other day.
- Restricting dietary intake can cause chronic fatigue and training limitations, making twice a day training more appropriate.
Protein Availability and Muscle Protein Synthesis
- Protein intake is vital for endurance adaptations. Ingesting protein increases MPS, contributing to gains in anaerobic power.
Supplementation with Mega Doses of Antioxidants
- Exercise produces free radicals, which may damage cells and contribute to fatigue.
- Antioxidants can help prevent or limit free radical damage and fatigue.
- High doses of antioxidants can inhibit training adaptations.
- A moderate amount of free radicals is needed to activate signaling pathways, making excessive antioxidant intake counterproductive.
Common Training Mistakes
Overtraining
- Workouts that are too long or intense.
- Inadequate recovery.
- Can lead to injury, immune system impairment, psychological staleness, and performance decline.
- Overtraining is considered a syndrome and is more common than undertraining.
- Symptoms: Higher HR and blood lactate levels at lower intensities, weight loss, chronic fatigue, psychological staleness, frequent colds, and impaired performance.*
Undertraining
- Insufficient exercise to stimulate physiological adaptations.
Performing Non-Specific Exercises
- Fails to enhance energy systems used in the sport.
- Inadequate preparation for the demands of the sport.
Lack of Long-Term Training Plan
- Improper use of training time.
- Missed opportunities for ongoing adaptations.
Failure to Taper Before Performance
- Insufficient taper can lead to suboptimal performance due to residual fatigue.
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Description
This quiz covers the critical concepts of acid-base balance, including the roles of buffers in both intracellular and extracellular settings. Participants will explore muscle buffering and the impact of lactic acid on blood pH. Additionally, the relationship between pulmonary function and exercise performance will be addressed.
