Fatigue and Recovery Mechanism• Understanding of the

multifactorial mechanisms (including fuel depletion, metabolic by products and thermoregulation) association with muscular fatigue, as a result of varied exercise intensities and durations

• Passive and active recovery methods to assist in returning the body to pre-exercise levels

• Oxygen uptake at rest, during exercise and recovery, including oxygen deficit, steady state and excess post-exercise oxygen consumption

Fatigue-Fuel DepletionThe multifactorial mechanism of fatigue…

… record some of the key words and messages in this clip.

Fatigue…… is an exercise-induced reduction in the power-generating capacity of a muscle and an inability to continue the activity. …the onset and development of fatigue depends on the type, intensity and duration of activity, the muscle fibres being used the type of muscular contractions and the performers fitness levels.

The onset is dependant on…

Type: E.g. intermittent of continuous Intensity: E.g. Duration of activity:E.g. Muscle fibres being used:E.g. Type of muscular contractions:E.g Performers fitness levels: E.g

Classifying fatigue Fatigue can be classified as1. fuel depletion2. accumulation of metabolic by-products3. neuromuscular interruptions4. elevated body temperature. But remember it is often multifactorial

Fatigue is multifactorial (caused by a combination of many factors)

Fuel Depletion Neuromuscular Event

Metabolic By-Products Elevated Body Temperature

List as many that you know in the boxes they belong in. How many can you think of?

Fatigue is multifactorial (caused by a combination of many factors)

Fuel Depletion Neuromuscular Event

Intramuscular ATP Decrease in CNS firing (rate and intensity)

Phosphocreatine Impaired sodium (Na+) and potassium (K+) gradients

Muscle Glycogen

Blood Glucose

Metabolic By-Products Elevated Body Temperature

H+ ions in plasma and muscles Very high core temperature

Inorganic phosphate Increased rates of dehydration

Adensine diphosphate (ADP) Redistribution of blood away from muscles to assist cooling=less blood/ 0

Ca+

Methods of generating ATP during muscle activity

Table 6.3 (p.149)

Lactic Acid- Good or Bad Read page 148 Define the term DOMS, Lactate Inflection Point,

Glycolysis, NAD +, acidosis What is one benefit of lactic acid? Explain the process of glycolysis with and without oxygen How is it that triathletes have near resting levels of

fatigue despite performing for hours? How is training beneficial in accelerating lactate

clearance? How does lactate and acidosis effect muscle

performance? Passive vs active recovery. What is better?

Thinking things through…1. List the metabolic consequence of supplying ATP via the

lactic acid system?2. How is it possible for triathletes to have near-resting levels

of lactic acid despite performing for over a couple of hours?3. Explain how the accumulation of H+ is implicated in muscle

fatigue4. Why are lactate levels tested regularly during training

sessions by physiologists, fitness advisors and coaches?5. Explain how aerobic training reduces lactate accumulation

at any given workload and yet results in a greater level of lactate accumulation during maximal efforts.

6. What is lactic acid buffering?

Something else to consider…1. Study Figure 6.2. Explain the uptake of

oxygen and oxygen deficit for an athlete 800m runner during an event lasting 2 minutes

2. Study figure 6.4. Explain the oxygen debt and its two parts, fast and slow.

3. List the fast and slow process of EPOC

Oxygen uptake during STEADY STATE EXERCISE

Can you identify the location of oxygen deficit, steady state, oxygen debt (EPOC)?

Define the following key terms Oxygen Deficit Steady State and Plateaus Oxygen debt or EPOC VO2 VO2 Max Buffering MyoglobinWorksheet

LIP in terms of Steady State… The Beep Test CD comes with the ability to have students

run 5 minutes at Level 6, 8, 10 etc...... Rather than continuing with more rapidly occurring beeps.

Most people can handled level 6, this is due to LIP not having been exceeded, there is energy system interplay, abundance of fuels.

What would happen if you allow a 5 min break and then complete next 5 minute set. What does this mean in terms of LIP?

Few students could sustain 5 minutes at level 10 – Once again, what is happening to lactate and therefore hydrogen accumulation? If students can keep up with this pace it’s clear they haven’t triggered LIP.

Oxygen uptake with increasing workload

What predictions can you make regarding this individual’s performance?

Returning to a pre-exercise state High intensities = high EPOC EPOC has two stages; EPOC fast

replenishment and EPOC slow replenishment

EPOC fast is primarily restoration of PC (taking 2-3 minutes)

EPOC slow is primarily concerned with removal of lactic acid though buffering

See table 6.5 (p.154) for a summary

Likely Causes of fatiguePredominant ES

Likely causes of Fatigue

Types of recovery

ATP-PC Fuel depletion of ATP and PC

Passive recovery

Lactic Acid Accumulation of by productH+ ionsInorganic Phosphates

Non dietaryActive recoveryMassageHydo/water based therapies

Aerobic Fuel depletionGlycogen stores, then fatsElevated body temperatureCausing dehydration and blood flow away from muscles

DietaryHigh GIRehydration via sports drinksNon-dietaryActive recoveryMassageHydro/water based therapy

Depletion of Fuel Only a factor when using the ATP-PC (PC depletion) and

predominantly aerobic events lasting over 1 hour CHO is the only source of energy during maximal intensity

exercise but fats are used increasingly during prolonged endurance events

Muscle glycogen is the first fuel, as this is depleted, the muscles use glycogen stored in the liver, once this is depleted it looks towards blood-born fats and stored fats.

The rate of energy production using glycogen is 50 to 100% faster that the production using fats. This is due to a more complex chemical reaction and great amounts of oxygen required. Small amounts of glycogen is needed to actually breakdown fats.

Protein can be used but only in extreme circumstances lasting over 5 hours

Carbohydrate and Fat utilisation during endurance events

What would happen to the athletes performance once fat is the predominant energy source? Why?

Metabolic By-productsH+ ions

The negative effects on performance associated with lactate accumulation is due to the increase in hydrogen ions

The breakdown of glucose or glycogen produces lactate and H+ (1 for 1)

The hydrogen ions makes the muscle acidic

As the concentration increases the blood and muscles become more acidic

This acidic environment will slow down enzyme activity and the breakdown of glucose itself

Inorganic Phosphate During muscle contraction ATP is broken down

to ADT and P1 (inorganic phosphate) Both are released during the cross bridge cycle

of the sliding filament theory explaining muscle contractions

P1 is linked to the power stroke of the cross bridge cycle

P1 accumulation occurs rapidly during high intensity exercise resulting in decreased contractile force production

P1 reduces the amount of Ca that can be released via the sodium-potassium pump and hence slows contraction

ADP is released near the end of the cross bridge cycle after the ATP split to release energy

Accumulation of ADP causes a decrease in the maximal velocity of shortening in the cross bridge and an associated reduction in power output

Neuromuscular FactorsDecreased CNS ‘firing’ The brain detects fatigue and acidosis so

sends weaker signals to working muscles in an effort to reduce intensity and slow down the work rate of the muscles

Less electrical stimulation created by sending fewer signmald eill result in less force and less frequent muscle contractions

This is a self protection mechanism

Elevated Temperature Is only an issue while performing in environmental

conditions of high heat an humidity Normal core temperature ranges from 36.5 to 37.5

degree Celsius Hyperthermia is unusually high body temperature and

elevated core temperature and severely affects performance

Muscles produce heat as they work Our bodies must loose this heat via radiation,

conduction, convection and evaporation Once the body looses 2-3% of it’s body weight through

sweating, thermoregulation is impaired (the bodies ability to keep the core temp. within certain boundaries

Physiological result of sweat loss- see fig 6.9 (p.160)

Recovery Strategies Recovery aims to return the body to pre-exercise

conditions and reverse the effects of fatigue. Efficient recovery strategies will enhance adaptation to

exercise loads as well as preparing the athlete for future training.

Read pages 161-167. Summarise the following recovery strategies

1. Refuelling: Phosphocreatine, muscle glycogen and blood glucose

2. Metabolic by-product: Removal of H+ ions in plasma and muscles and replenishing inorganic phosphate (Pi) and Adenosine diphosphate (ADP)

3. Addressing neuromuscular factors. 4. Lowering body temperature.

Active vs PassiveActive1. Dietary refueling and

hydration2. Removal of H+ ions3. Rebounding P1 to ADP4. Addressing

nueronmuscular factors5. Strategies for cooling

Passive1. PC

Refueling

Application Tasks1. Work the Web: Review of Sports Drinks on the Market (p.166) http://www.choice.com.au/Reviews-and-Tests/Food-and-Health/Food-and-drink/Beverages/Sports-drinks-review-and-compare/Page/Introduction.aspxRecord Key Findings of the study.

2. Follow the following link http://www.ausport.gov.au/ais/sssm/fatigue_and_recovery to investigate the number of ways the AIS promotes performance recovery. Record Key findings3.Investigate Strategies for cooling . Record Key findings http://www.coolmax.invista.com/ 4. Student directed presentation on chosen fatigue management strategy E.g. Compression garments, hydration, ice baths, etc! Explain the scientific theory that underpins your chosen method