Acute Physiological Responses to Exercise

Acute Physiological Responses to Exercise

Key Concepts

• Acute physiological responses to exercise involve the cardiovascular, respiratory, and muscular systems.

• These responses include changes in oxygen uptake at rest, during physical activity, and during recovery, including oxygen deficit, steady state, and excess post-exercise oxygen consumption (EPOC).

• The body experiences acute responses to exercise to supply more fuel and oxygen to working muscles and remove waste products.

• These responses are dependent on the intensity, duration, and type of exercise being undertaken and only occur for the duration of exercise and recovery.

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Respiratory System

• Ventilation (Increases):

  • Ventilation is the amount of air breathed in and out per minute.

  • Ventilation (litres/min) = Tidal Volume (millilitres/breath) x Respiratory Rate (breaths/min).

  • Example: 6 \, \text{L/min} = 500 \, \text{ml/breath} \times 12 \, \text{breaths/min}

  • Both tidal volume (amount of inspired & expired air per breath) and respiratory rate (breaths per minute) increase.

  • This increase is due to the increased demand for ATP, which requires more oxygen.

  • During submaximal exercise, ventilation plateaus when oxygen supply equals demand.

• Diffusion (Increases):

  • Diffusion refers to the movement of gases (oxygen and carbon dioxide) from areas of high pressure to areas of low pressure.

  • Lungs: Oxygen moves from the alveoli (high concentration) into the bloodstream (low concentration); carbon dioxide moves from the blood stream (high concentration) into the alveoli (low concentration) to be exhaled.

  • Muscles: Oxygen moves from the bloodstream (high concentration) into the muscles (low concentration); carbon dioxide moves from the muscles (high concentration) into the bloodstream (low concentration) to be transported to the lungs and exhaled.

Cardiovascular System

• O2 Consumption (VO2):

  • VO_2 is the volume of oxygen consumed.

  • VO_2 increases linearly with exercise intensity.

  • VO_2 \,\text{max} is the maximal amount (volume) of oxygen that can be taken in (respiratory system), transported (cardiovascular system), and utilized (muscular system).

  • VO2 \,\text{max} = \text{Cardiac Output} \times aVO2 \,\text{difference}

• aVO2 Difference (Increases):

  • The aVO_2 difference is the difference in oxygen concentration in the arterioles compared to the venules.

  • It represents the amount of oxygen used by the muscle.

• Cardiac Output (Increases):

  • Cardiac Output (Q) is the amount of blood pumped out of the left ventricle per minute.

  • \text{Cardiac Output} \,(Q) = \text{Stroke Volume} \times \text{Heart Rate}

  • (\text{litres/min}) = (\text{millilitres/beat}) \times (\text{beats/min})

  • Example: At Rest: 5 \, \text{L/min} = 70 \, \text{ml/beat} \times 70 \, \text{beats/min}

  • Example: At Maximal exertion: 35 \, \text{L/min} = 175 \, \text{ml/beat} \times 200 \, \text{beats/min}

  • Stroke volume (amount of blood ejected by the left ventricle per beat) and heart rate (beats per minute) both increase, but stroke volume plateaus at submaximal intensity.

• Venous Return (Increases):

  • Venous return is the rate of blood flow back to the heart.

  • Muscle contractions help to return the blood to the heart

• Redistribution of Blood Flow:

  • During exercise, blood flow is redistributed to working muscles.

  • Vasoconstriction of arterioles supplying inactive muscles reduces blood flow.

  • Vasodilation of arterioles supplying active muscles increases blood flow.

• Blood Pressure:

  • Normal blood pressure is 120/80 (systolic/diastolic).

  • Systolic pressure is the pressure of blood passing out of the heart.

  • Diastolic pressure is the pressure of blood coming back into the heart.

  • In aerobic activities, systolic blood pressure increases, while diastolic remains relatively stable as intensity increases. This stability is due to the dilation of many arteries delivering blood and oxygen to muscles.

  • In weight resistance activities, both systolic and diastolic blood pressure increase.

• Blood Flow (Increases)

• Blood Volume (Decreases):

  • Blood volume decreases due to plasma loss.

  • Plasma constitutes 55% of total blood volume, erythrocytes (red blood cells) 45%, and leukocytes & platelets (buffy coat) less than 1%.

Muscular System

• aVO2 Difference (Increases):

  • The aVO_2 difference (arteriovenous oxygen difference) increases, indicating more oxygen is extracted from the blood by the muscles.

• Temperature (Increases):

  • Muscle temperature increases due to heat produced during energy production.

  • C6H{12}O6 + 6O2 \rightarrow 6CO2 + 6H2O + \text{Energy}

• Motor Unit Recruitment (Increases):

  • More motor units are recruited to generate greater force.

• Energy Substrates (Decrease):

  • Energy substrates (fuel), such as glucose, glycogen and fats, are depleted as they are used to produce energy (ATP).

• Lactate (Increases):

  • Lactate production increases, which coincides with an accumulation of H^+ ions, leading to fatigue.

Chapter 6

Chapter 6: The Interplay of Energy Systems

Key Concepts

• Resynthesizing ATP:

  • Via two anaerobic energy systems: The ATP-PC system and the anaerobic glycolysis system.

  • Via the aerobic energy system.

• Energy Systems Overview:

  • Two anaerobic energy systems: The ATP-PC system and the anaerobic glycolysis system.

  • One aerobic energy system: The aerobic system.

Fuels for Energy Systems

Anaerobic Systems

• ATP-CP System:

  • Fuel: PC (Phosphocreatine) or CP (Creatine Phosphate).

• Anaerobic Glycolysis:

  • Fuel: Glycogen.

Aerobic System

• Fuels:

  • CHO (Carbohydrates): Moderate rate of ATP production.

  • Fat: Slower rate of ATP production.

Energy System Activation

• All 3 energy systems are activated at the start of exercise (INTERPLAY).

• The contribution of each system depends on:

  • Intensity of exercise.

  • Duration of exercise.

  • Amount of oxygen available to be used by muscles.

  • Fuel availability: Depletion of chemical (ATP & PC) and food fuels (CHO, fats, & protein) during exercise.

Cell Respiration in Mitochondria

• Formula for cellular respiration (in the presence of O2):

  • Oxygen + G

  • lucose \rightarrow Energy + CO2 + H2O

• Source of glucose:

  • Glycogen (CHO carbohydrates).

  • FFAs or triglycerides (Fats).

  • Amino Acids (Protein).

The Role of ATP

• Every muscular contraction is due to ATP (Adenosine Triphosphate) being split apart and releasing energy.

• After being split, we are left with ADP (Adenosine Diphosphate) and Pi (inorganic phosphate) - these are metabolic byproducts.

• ADP & Pi must resynthesize (recharge) back to ATP to continue exercising.

• ATP resynthesis occurs through the 3 energy systems working together (interplay) to provide the energy that is required.

• ATP \rightarrow ADP + Pi + Energy

ATP Breakdown and Energy Release

• The three energy systems break down fuel stores releasing energy for the resynthesis of ATP.

• Adenosine - P - P - P \rightarrow Adenosine - P - P + Energy

Chemical Fuels

• ATP (Adenosine Triphosphate):

  • The major source for muscular contraction (no ATP = no contractions).

  • Consists of one adenosine molecule with three phosphates joined together.

  • The human body only has a small amount stored in the muscles for quick access, roughly enough for 2-3 seconds of muscular work.

  • Must continually be resynthesized from energy substrates (PC, Glycogen, Triglycerides, & Amino Acids).

• PC (Phosphocreatine) also can be referred to as CP:

  • Broken down to resynthesize ATP as part of the ATP-PC energy system.

  • Approximately 10 seconds of PC is stored in the muscle.

  • ATP \rightarrow ADP + Pi + Energy

• The breaking of ATP Gives Energy for movement

  • ATP \rightarrow ADP + Pi + Energy

• PC or CP = Phosphocreatine is used to create more ATP. we only have a small amount stored at muscles (10-15 seconds)

  • ADP + PC \rightarrow ATP + C

Food Fuels

• The food we eat refuels the three energy systems.

  • Carbohydrates (CHO): The preferred source of energy during exercise as they require less O2 to be broken down.

  • Fats: The body’s main source of fuel at rest and during prolonged submaximal exercise. Require more O2 than carbohydrates to be broken down.

  • Protein: Used mainly for growth and repair. ‘last resort’ fuel source.

Food Types, Fuel Conversions, and Storage

Nutrient Breakdown

Food as Energy Sources

• ATP stored in muscle by using

  • Chemical fuels = phosphocreatine (PC) stored in muscle or

  • Food fuels = carbohydrates, fats and proteins stored around the body

    • 1 gram = 4 calories

    • 1 gram = 4 calories

    • 1 gram = 9 calories

Capacity of Chemical and Food Fuels

Food Fuel Sources During Physical Activity

• The body has a preference for fats at rest.

• CHOs are the only fuel source utilized at max intensities.

• As CHO storage is limited (60-90mins), extended endurance events see an increased contribution from fats for ATP production, hence performance slows due to fats having a slower rate of ATP production compared with CHO.

• Fats take a lot of oxygen away from working muscles in order to rebuild ATP and they require many more chemical reactions than carbohydrates to be broken down in order to “recharge/rebuild” ATP.

PC Restoration Rates

Summary of Food Fuels (CHO, Fats, Protein)

• CHO carbohydrates are the bodies preferred fuel source rather than fats to release energy.

• CHO loading only applicable for athletes competing > 1-2 hours up to 10 days prior

• CHO loading helps to spare glycogen for higher intensity efforts

• CHO are needed to use fats for energy

• Fats can produce more ATP than carbohydrates but they require more oxygen to produce an equivalent amount of ATP.

• Fats also transport fat-soluble vitamins A, D, E and K.

• In prolonged exercise, fats becomes increasingly important energy source as glycogen becomes depleted.

• Protein forms the building blocks of tissue for growth and repair.

• All enzymes which speed up chemical reactions are proteins.

• Large amounts of oxygen is required for breaking down protein (used only in extreme extended duration exercise)

• 1 glucose molecule = 2 ATP (anaerobically)

• 1 glucose molecule = 36 ATP (aerobically)

• 1 fat molecule = 3x147 = 441 ATP

• CHO is preferred to fats because fats require more oxygen to produce the same amount of energy and the rate of ATP produced using fats is slower than that of CHO

Summary of the ATP & PC Chemical Fuels

• A limited amount of PC is stored at the muscles (about 10 seconds’ worth at maximal intensity), with larger muscles capable of storing slightly more PC than this (12 to 14 seconds at maximal intensity).

• ATP and PC are stored at the muscles and available for immediate energy release. Stores are limited – the more intense the activity, the quicker the chemical fuels are utilised to produce ATP.

• After approximately five seconds of maximal activity, the PC stores are 40 to 50 per cent depleted

• There is approximately four times as much PC stored at muscles as there is ATP.

• Once PC has been depleted, it can only be replenished when there is sufficient energy in the body, and this usually occurs through the aerobic pathway or during recovery once the activity has stopped.

• Passive recovery is the most appropriate form of recovery to maximize replenishment of PC stores

• Time to fully replenish PC stores is approximately 2 minutes.

• Once phosphocreatine has been depleted at the muscle, ATP must be resynthesised from another substance − typically glycogen, which is stored at the muscles and the liver

Characteristics of the 3 Energy Systems

• Rate

• Yield

• Fuel

• Time

Key Terms

• Rate: Refers to how quickly ATP is resynthesized

  • ATP-PC = fastest

  • Anaerobic glycolysis

  • Aerobic = slowest

• Yield: The total amount of ATP that is resynthesized

  • ATP-PC = lowest

  • Anaerobic glycolysis

  • Aerobic = highest

Characteristics of the 3 Energy Systems

Methods of Generating ATP During Muscle Activity

ATP-CP Energy System

• Anaerobic (no Oxygen required)

• Most rapidly available source of ATP as it’s stored in the muscles and simple reactions (fastest rate)

• Breaks down phosphocreatine (PC) to resynthesize ATP anaerobically.

• PC splits releasing energy and leaving Pi and C.

• Energy released is used to resynthesize ATP stores (ADP + P)

• ATP stores last max 3 secs

• PC stores last for 10 secs @max intensity activity

• After 5 seconds @max, Anerobic glycolysis ES will become dominant

• Once PC stores have depleted, can be replenished via 3 minutes of passive recovery, or an intensity low enough not to call upon PC (Oxygen required for P + C to be returned to PC)

• Intensity usually maximal, >95% HR max.

• Fastest Rate, lowest yield (0.7-1 ATP)

• Duration Around 10 seconds

• Fuel PC (Phosphate Creatine)

• Typical events – jumps, throws, short sprints, diving

• Equation: PC + ADP \rightarrow ATP + Creatine

Anaerobic Glycolysis Energy System

• How the system works:

  • Glycogen is broken down in the absence of oxygen (Anaerobic glycolysis).

  • This produces pyruvic acid which is converted to Lactic Acid.

  • A further byproduct of Lactate are hydrogen ions (H+) which make the muscle pH decrease (More acidic), reducing glycolysis and causing muscular discomfort and an inability for the to contract maximally.

  • H+ cause this by effecting the actions of enzymes needed for glycolysis to occur

  • This is a safety mechanism that prevents the cells being destroyed under extremely acidic conditions

  • In recovery, (when sufficient oxygen is available), H+ combines with pyruvate to form lactate which is reconverted to glycogen in the liver

• Supplies ATP at a slower rate than the ATP-PC system as it requires longer and more complex chemical reactions (12) however still “fast” rate

• The yield of ATP production is twice that of the ATP-PC system (2-3 ATP)

• Intensity is usually >85% HR max.

• Duration Around 30-40 seconds

• Fuel Glucose/CHO/Glycogen

• Typical events – 200-400m run, 50m swim, repeated sprints in team sport

Summary of the Anaerobic Glycolysis Energy System

• The anaerobic glycolysis system produces ATP without oxygen

• Involves more complicated and longer chemical reactions than the ATP−PC system to release energy.

• It also supplies energy from the start of intense exercise, and peak power from this system is usually reached between five and fifteen seconds and will continue to contribute to ATP production until it fatigues (two to three minutes).

• During maximal exercise, the rate of glycolysis may increase to 100 times the rate at rest.

• It produces lactic acid, which breaks down into lactate and H+ (hydrogen irons) and lactate (in the presence of O2) can be broken down to glycogen to provide further energy.

• About 12 chemical reactions take place to make ATP under this process, so it supplies ATP at a slower rate than the ATP-PC system.

• It provides energy for longer during submaximal activities when PC is depleted and lactic acid accumulation is slower. This provides a stop-gap until sufficient oxygen is transported to working muscles for the aerobic system to become the major energy contributor.

• It provides twice as much energy for ATP resynthesis as the ATP−PC system.

• It increases it’s ATP contribution if performance intensity exceeds the lactate inflection point

Aerobic Energy System

• How the system works:

  • Requires Oxygen

  • CHOs (preferred during exercise) & FFAs (preferred during rest) are broken down to release energy.

  • When using CHOs pyruvic acid is produced and further broken down producing CO2, H2O & ATP (via Kreb’s cycle)

  • Further breakdown via the electron transport chain. It requires hydrogen ions and oxygen, producing water and heat.

• Slowest rate of ATP resynthesis & requires most chemical reactions

• The yield of ATP

  • 36-38 ATP (when using CHO)

  • 147*3=441 ATP (when using FAT).

• Intensity 70-85% HR max (sub-maximal)

• Duration Anything over 2 mins is dominant “aerobic” overall

• Fuel CHO and fat

• No fatiguing by-products

• Typical events – archery, marathon, road cycling

Summary of the Aerobic System

• The aerobic system is the slowest system to contribute towards ATP resynthesis due to the complex nature of its chemical reactions.

• It is capable of producing the most energy in comparison to the other two energy systems ~ between 30- 40 times

• It requires oxygen, which can be provided (90 per cent of VO2 maximum) within 60 seconds.

• It involves many more complex chemical reactions than the anaerobic energy systems to release energy.

• It preferentially breaks down carbohydrates rather than fats to release energy.

• Fats can produce more ATP than carbohydrates but they require more oxygen to produce an equivalent amount of ATP.

• It releases no toxic/fatiguing by-products and can be used indefinitely.

• It provides 50 times as much ATP as the anaerobic systems combined.

• It contributes significant amounts of energy during high-intensity/maximal activities lasting one to two minutes.

• The aerobic system is also activated at the start of intense exercise, and peak power from this system is usually reached between one and two minutes and will continue to be the major ATP contributor as the anaerobic glycolysis system decreases its contribution.

• Any activity that lasts over 2mins will mean the aerobic system is dominant.

Key Characteristics of the Energy Systems

Determining Energy System Contribution

• Intensity

• Duration

• Availability of Oxygen

• Availability of Fuel

Energy System Interplay

• All the energy systems are contributing towards ATP production simultaneously throughout any exercise bout, but the proportional contribution of ATP from each system to the metabolic demand will shift according to exercise intensity and duration.

• The longer the activity lasts, the more likely it is that the ATP-PC system will contribute less, unless given the opportunity to recharge.

Oxygen Uptake

• At rest: The body’s need for ATP is relatively small, requiring minimal oxygen consumption.

• At Max: Oxygen uptake at Max

• When exercise begins, oxygen uptake increases as the body attempts to meet the increased oxygen demand of the working muscles that results from their need to produce more energy for ATP resynthesis

• Oxygen Deficit: A discrepancy (shortfall) between supply and demand of Oxygen to the working muscles. Occurs during the transition from rest to exercise, particularly high-intensity exercise, and at any time during exercise performance when exercise intensity increases. During these times, anaerobic sources must be involved in providing energy. In a graph, this will appear as an incline, or hill, in the line. The oxygen deficit occurs because the respiratory and circulatory systems take some time to adjust to the new oxygen demand (even at low exercise intensities)

• Steady State: When Oxygen supply meets oxygen demand. Depending on the intensity of the exercise, this may take anywhere between a few seconds or 1 minute or more to achieve. This steady state in oxygen uptake also coincides with a plateau in heart rate and ventilation. If exercise intensity is increased again after reaching a steady state, the athletes anaerobic pathways will need to supplement the gap until a steady state is again reached. A steady state can only be held up to and including the lactate inflection point. It should be noted that in trained endurance (aerobic) athletes, the oxygen deficit is reduced due to these athletes attaining steady state sooner than untrained individuals. In a graph, this will appear as plateau, or flat line.

• Excess post-exercise oxygen consumption (EPOC): The amount of oxygen consumed during the recovery period after the cessation of an exercise bout that is over and above the amount usually required during rest. This is where we ‘repay’ the oxygen needed during exercise that we were unable to provide. The higher the intensity and duration of activities, the larger the oxygen debt and the longer it takes to repay it

Factors Influencing Recovery Rates

• Energy system contribution.

• Intensity of exercise

• Duration of exercise

• Amount of oxygen available to be used by muscles

• Fuel availability

  • Depletion of chemical (ATP & PC) and food fuels (CHO, Fats & Protein) during exercise

Chapter 7

Muscular Fatigue Mechanisms

• Key Knowledge:

  • Muscular fatigue mechanisms linked to varied sport and exercise intensities and durations.

  • Nutritional and hydration strategies to enhance performance, delay fatigue, and improve recovery.

• Key Skills:

  • Explain muscular fatigue mechanisms associated with the 3 energy systems.

  • Describe nutritional and hydration strategies to enhance performance, delay fatigue and improve recovery.

Assessment

• Outcome 1:

  • Analyze primary data from physical activity to refine movement skills using biomechanical and skill-acquisition principles.

  • Marks allocated: 45

• Outcome 2:

  • Use data from practical activities to analyze body and energy systems, explain fatigue factors, and recommend recovery strategies.

  • Marks allocated: 45

• **Contribution to final assessment:

  • School-assessed Coursework for Unit 3 contributes 20% to the study score.

Fatigue Mechanisms

• Fatigue and Recovery Overview

  • Neuromuscular factors: Decreased CNS firing, impaired Na^+ and K^+ gradients

  • Fuel depletion: Intramuscular ATP, phosphocreatine, muscle glycogen, blood glucose

  • Elevated body temperature: Dehydration, redistribution of blood away from muscles

  • Metabolic by-products: H^+ ions, inorganic phosphate (P_i), ADP, Ca^{2+} ions

  • Considerations: How long until the next event or training?

• Recovery

  • Fuel restoration: High-GI vs low-GI sports drinks and gels

  • Active recovery

  • Passive recovery

  • PC restoration

What is Fatigue?

• A reduction in the ability of muscles to produce power or force.

• Fatigue varies based on:

  • Duration: Longer events increase the likelihood of fuel depletion (CHO stores last 60-90 mins).

  • Intensity: Higher intensity increases the contribution from anaerobic glycolysis (accumulation of H^+).

  • Level of physical fitness.

  • Age.

  • Diet: PC and CHO stores limit system capacity.

  • Environmental conditions: High temperatures require cooling, reducing oxygen available for aerobic ATP production.

  • Types of contractions occurring.

  • Muscle fiber type being used.

Fatiguing Factors

• Exercise physiologists believe that fatigue is multi-factorial

• Thermoregulatory Fatigue

  • Very high core temperatures.

  • Increased rates of dehydration.

  • Redistribution of blood to assist cooling.

• Fuel Depletion

  • Intramuscular ATP.

  • PC.

  • Muscle Glycogen.

  • Blood Glucose.

• Accumulation of metabolic by-products

  • H^+ in plasma and muscles.

  • Inorganic phosphates (P_i).

  • Adenosine diphosphate (ADP).

Central vs. Peripheral Fatigue

• Central Fatigue

  • Occurs in the CNS, causing a decrease in muscular function due to CNS impairment.

• Peripheral Fatigue

  • Occurs at the muscles where internal processes become disrupted.

Levels of Fatigue

• Local Fatigue

  • Causes, signs and symptoms: Fatigue experienced in a specific muscle or muscle group. Occurs when the same muscle group is repeatedly used without sufficient recovery. Muscles feel heavy, tingling pain, or cramp.

  • Fatigue indicator (out of 10): 2-4

  • Examples: After completing a weight station (e.g., eight bench presses at 80% of repetition maximum) or in biceps/triceps after a game of squash or badminton.

• General Fatigue

  • Causes, signs and symptoms: Fatigue occurs after completing a full training session or competitive game. Performers feel that all muscles are 'weakened' and may experience psychological fatigue.

  • Fatigue indicator (out of 10): 6-8

  • Examples: After completing a circuit session or a 'full-on' game of hockey.

• Chronic Fatigue

  • Causes, signs and symptoms: An unhealthy breakdown of the immune system caused by overtraining, poor training program design, inappropriate recovery strategies, and/or excessive competition demands. Often accompanied by increased susceptibility to illness/infection, persistent muscle soreness, and reduced motivation.

  • Fatigue indicator (out of 10): 10

  • Examples: Diagnosed as chronic fatigue syndrome (CFS) or sometimes glandular fever.

Fatigue and Recovery: ATP-PC System

• Fatiguing factor:

  • Fuel Depletion: ATP & PC

    • Limited stores of ATP (<2secs) & PC (around 10secs) in muscles

    • When PC depletes, the body breaks down glycogen to resynthesise ATP

    • Results in decreased contractile force and energy production rate.

• Recovery Strategy:

  • Fuel Depletion: ATP & PC

    • Facilitated by passive recovery (during the rapid part of EPOC).

    • Low pH levels (high H^+ levels) and a slow/low supply of O_2.

    • Greater aerobic power assists with speedy PC recovery; anaerobic athletes still require aerobic training.

• Recovery time:

  • 30secs - 70% PC Stored

  • 60secs - 75% PC Stored

  • 3mins - 98% PC Stored

  • 10mins - 100% PC Stored

Fatigue and Recovery: ATP-PC & Anaerobic Glycolysis

• Fatiguing factor:

  • Accumulation of metabolic by-product - P_i

    • Slows the release of calcium ions and reduces the contraction force of muscles.

    • Occurs when ATP-PC & Anaerobic Glycolysis systems contribute more to energy production.

  • Recovery:

    • Removed best during passive recovery where high levels of O_2 are available

  • Accumulation of metabolic by-product - ADP

    • Accumulates during explosive activities; reduces muscle power.

    • Occurs when ATP-PC & Anaerobic Glycolysis systems contribute more to energy production.

  • Recovery:

    • Removed best during passive recovery where high levels of O_2 are available

Fatigue and Recovery: Anaerobic Glycolysis

• Fatiguing factor:

  • Accumulation of metabolic by-product - Hydrogen Ions (H^+)

    • H^+ accumulates when the LIP is exceeded.

    • Increased muscle acidity slows glycolytic enzymes and glycogen breakdown.

    • Occurs when Anaerobic Glycolysis has a higher contribution.

• Recovery Strategy:

  • The quicker H+ can be removed, the quicker the performer can recover

  • Best removed when oxygen levels remain elevated with increased blood flow.

  • Active Recovery: Maintain elevated O_2 intake and blood flow.

  • Massage: Elevated blood flow only.

  • Contrast bathing: Elevated blood flow only.

Lactate Inflection Point (LIP)

• L.I.P. has been exceeded when lactate appearance in the blood is greater than lactate removal from the blood. (Lactate rises from a steady state)

• When L.I.P. is reached, most energy is still supplied aerobically; however, an increased reliance on the Anaerobic Glycolysis energy system due to an increased intensity results in the lactate increase

• Remember: It is not the lactate itself that causes fatigue. The rise in blood lactate is a good indicator of the amount of H^+ that is in the muscle

• When the body produces ATP via the anaerobic glycolysis system, lactic acid is produced (by product of metabolising glucose when oxygen isn’t present) thus produces METABOLIC BY PRODUCTS = LACTATE AND HYDROGEN IRONS (H^+). It is the accumulation of metabolic by products, namely H^+, that interferes with muscle contractions hence causes fatigue. In the presence of oxygen, lactate is converted back to glucose to use as fuel however it is the accumulation of H^+ that causes a drop in muscle pH which increases muscle acidosis.

• Passive Recovery:

  • Min lactate removal time: 1 hour

  • Max lactate removal time: 2 hours

• Active Recovery:

  • Min lactate removal time: 30 mins

  • Max lactate removal time: 1 hour

Fatigue and Recovery: Aerobic Energy System

• Fatiguing factor:

  • Fuel Depletion: Glycogen

    • Muscle glycogen is used first, then liver glycogen

    • Considered a fatiguing factor after 60mins of continuous exercise

    • Will ‘Hit the wall’ 2-3hrs into an endurance event

    • Energy production form glycogen is 50-100% faster than the rate from fats

• Recovery Strategy:

  • Restored through replenishment during and post exercise bout (best results with high GI in first 30mins after completing exercise)

  • Glycogen depletion can be minimised by carbohydrate loading (learn more later in the course)

    • Post event glycogen intake (High GI)

      • Within 1 hour - 55% in 5hrs, 100% in 24hrs

      • 1-2 hours - 100% in 24-48hrs

      • 5+ hours - Up to 5 days

• Fatiguing factor:

  • Thermoregulation

    • Body heats when producing ATP (you take your jumper off when you start exercising)

    • To regulate rising body temperature, body sweats leading to water evaporating from the bloodstream

    • To do this, the body redistributes blood AWAY from muscles to the skin

    • Therefore, less oxygen for ATP production (so cannot work as high “aerobically”)

    • This process also leads to dehydration meaning blood loses water so thicker (increased viscosity) so the heart has to pump harder to move blood around (leads to increased heart rate for same intensity)

• Recovery Strategy:

  • Cool body temperature by consuming fluid (as you will most likely experience dehydration)

  • Recovery in cool environment (e.g. under a tree)

Fatigue: Neuromuscular Factors

• Fatiguing factor:

  • Decreased firing of the CNS

    • Brain detects fatigue – weaker signals sent to muscles to reduce intensity (self-protection)

    • As intensity increases, Acetylcholine release slows down, resulting in less forceful contractions

• Recovery - Passive recovery is the best

  • Loss of Electrolytes- Impaired sodium and Potassium Gradient

    • Electrolytes lost due to sweat

    • Without electrolytes, nerves cannot communicate with each other or perform their essential functions

    • Impaired sodium–potassium pump function can restrict muscular contractions.

  • Recovery- Sports and electrolyte drinks can help to maintain and replenish electrolyte levels

Lactate Inflection Point (LIP)

• The highest intensity at which the body can remove lactate at the same rate it is being produced.

• OR The point beyond which lactate accumulation exceeds the removal.

• Any intensity beyond this point will see a dramatic increase in blood lactate levels, as lactate is being produced faster than it can be oxidized or broken down.

• Aerobic training improves (DELAY) LIP, so athlete can work at higher intensities for longer durations aerobically.

Recovery Rates and Strategies

• Recovery time

  • 30secs - 70% PC Stored

  • 60secs - 75% PC Stored

  • 3mins - 98% PC Stored

  • 10mins - 100% PC Stored

• Passive Recovery:

  • Min lactate removal time: 1hour

  • Max lactate removal time: 2hours

• Active Recovery:

  • Min lactate removal time: 30mins

  • Max lactate removal time: 1hour

Recovery Strategies for Energy Systems

• ATP-CP System

  • Passive recovery to replenish PC stores more rapidly than active recovery

• Anaerobic Glycolysis

  • Active recovery to remove accumulated metabolic by products - hydrogen irons (H^+)

• Aerobic

  • CHO replenishment within 30 minutes to replace lost glucose/glycogen. CHO load.

  • Active recovery to remove accumulated metabolic by products - ADP & Pi

    • Increasing blood flow assists with removal of MBP (H^+).

    • Muscle pump through active recover & massage & contrast therapy.

    • Assist body to regulate temperature by hydrating before and cooling body after.

  • A well developed aerobic system assists more rapid replenishment of ATP and PC stores

  • A well-developed aerobic system assists more rapid removal

  • Active recovery should be used to remove accumulated metabolic by products - hydrogen irons (H^+) when exercise involve increased contributions from anaerobic glycolysis.

Nutritional Needs of the Athlete

• Appropriate nutrition is vital for all of us, not only in the choice of foods we ingest, but also with timing and quantity of foods consumed.

• The essential nutrients that are required by all athletes include:

  • Carbohydrates, fats, proteins, vitamins, minerals, water and fibre.

• Athletes must develop their own individual eating plans to achieve maximum results from their training programs.

• Not only does the athlete need to take into consideration the specific nutritional requirements of the sport that they participate in, they also need to consider their individual energy expenditure, metabolism and state of health

• Good nutrition and hydration strategies should be practised for both training and competition.

• For the first 2 hours during recovery blood is being blood is still being sent to muscles in large quantities and muscles are still receptive to taking up glucose and enzymes conducive to converting glucose to glycogen.

Pre, During, and Post Training/Competition Nutrition

• Pre-training/competition

  • Aim is to keep the athlete from feeling hungry before and during exercise, and maintain optimal levels of energy stores for the activity that follows.

• During training/competition

  • Acts as an alternative fuel source and maintains fluid lost throughout the exercise bout.

  • Note: Some evidence suggests that top-up fuelling is beneficial for events lasting longer than 30 minutes, as the body preferentially uses glucose from the blood due to it being a faster fuel source.

• Post-training/competition

  • Ingested within 30 mins for 100% restored glycogen in 24 hrs for best recovery.

Nutritional Recovery Strategies: Carbohydrates

• The body uses glycogen at rate of 1 gram per minute during moderate intensity exercise and slightly higher at higher intensities

• Carbohydrates should be consumed during exercises lasting longer than 1 hour to replace the glycogen used to produce energy (roughly 60 grams/hour)

• The effects of glycogen depletion can be minimized by not only refueling during the event, but also ensuring you have adequate stored before training or competition.

• Pre-exercise

  • Carbohydrate loading which involves a higher intake of carbohydrates for 4-5 days prior to competition in combination with tapering (maintain intensity, decrease duration)

• During exercise

  • Carbohydrates should be consumed regularly throughout the activity as this is an effective way to enhance endurance and performance.

  • High glycaemic index ranked foods are recommended to be consumed during exercise as these types of foods are rapidly digested and absorbed, and therefore are more readily available as an immediate energy source.

  • Could include Hypertonic sports drinks (both carbs and rehydration), Carb gels, sports bars, etc…

• Post-exercise

  • It is critical to replenish used glycogen as quickly as possible during recovery.

  • Muscles are able to store greater amounts of carbohydrates within the initial couple of hours after exercise.

    • High GI foods should be consumed as soon as possible to ensure rapid restoration of Muscle glycogen (first) and liver glycogen (second)

      • Post-event glycogen intake (high GI)

        • Within 1 hour - 55% restored in next 5 hours, 100% restored within 24hrs (1 day)

        • 1-2 hours - 100% restored within 24-48hrs (2 days)

        • 5+ hours - Up to 5 days

Hydration Strategies

• Post exercise hydration should aim to reverse fluid loss throughout training/competition

• Athletes rarely have just water as a sports drink will aid a faster recovery

• General guidelines:

  • Consume approximately 200–600 millilitres of fluid prior to their event

  • Strive to replace approximately 500–1000 millilitres of fluid per hour during the actual event

  • Begin drinking early in exercise and consume small volumes (200–300 millilitres) every 15–20 minutes if possible.

• A fluid volume equal to 150% of the fluid deficit should be consumed within 2-4 hours after exercise to completely rehydrate the body

• Water

  • Rehydrates lost fluids due to sweating during exercise.

  • Adequate rehydration fluid for activities less than 1 hr duration

• Sports drinks

  • Rehydrates

  • CHO

  • Electrolytes

  • Encourages thirst

  • More Palatable (so less chance of dehydration)

  • Greater absorption than water

  • Decrease urine loss

Nutritional Recovery Strategies: Protein

• Protein has several important functions in the body. These include:

  • Muscle construction and repair

  • Promoting glycogen resynthesis

  • Playing an important role in the immune system

  • Facilitating the transmission of nerve impulses throughout the nervous system

  • Preventing sports anaemia (low iron) by promoting an increased synthesis of haemoglobin, myoglobin and oxidative enzymes.

• Protein is an important part of an athlete’s diet as it plays a key role in post-exercise recovery and repair.

• Nutritionists recommend that protein contributes up to 15 per cent of total daily food intake; however, strength and endurance athletes may require additional volume of protein for growth of muscle tissue

Glycaemic Index (GI)

• The glycaemic index refers to a scale that ranks carbohydrates by how much they raise blood-glucose levels over a two-hour period compared with pure glucose.

• Foods are ranked from 0 to 100.

• Foods that have a high glycaemic index (70 and above) are digested quickly, resulting in a rapid and high increase in blood-glucose levels.

• Foods with a low glycaemic index (55 and less) are digested more slowly, resulting in a more gradual and less rapid rise in blood-glucose levels

Protein Consumption for Muscle Repair

• To repair and build muscles, athletes must refuel with high-protein foods immediately after exercise, especially after resistance training.

• Recommended to consume 30-40 grams of protein that includes 3-4 grams of leucine per serving to increase protein synthesis.

• Whey is an optimal post-workout protein due to its amino acid composition.

• Athletes should also consume protein regularly throughout the day after training to stimulate protein synthesis for up to 48 hours

• Post workout shakes as they can combine carbohydrates, protein and also help rehydrate

• Protein is optimally absorbed 30-60 mins after training or competition. This is because there has been micro-trauma at the muscles, so they are more susceptible to uptake protein for repair and growth

Combining Carbohydrates and Protein

• Combining is optimal as consuming both CHO and protein means muscle construction and repair and greater promotion og glycogen resynthesis.

• A carb/protein snack provides an excellent combination and can include snacks as;

  • Yoghurt and cereal bar or banana

  • Sports protein bar

  • Liquid meal supplement

  • Cereal and milk

  • Cheese and tuna sandwich

• Only having a small amount of protein post-exercise is required to increase muscle protein synthesis

• Athletes aiming at increasing muscle mass benefit more from pre-work out snacks

• Foods containing protein should be consumed at least 45-60mins before exercise to allow for digestion and absorption

• Real foods will allow for a more sustained release which will aid repair over a longer period of time