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 Depletion The 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 as fuel depletion accumulation of metabolic by-products neuromuscular interruptions 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… List the metabolic consequence of supplying ATP via the lactic acid system? How is it possible for triathletes to have near-resting levels of lactic acid despite performing for over a couple of hours? Explain how the accumulation of H+ is implicated in muscle fatigue Why are lactate levels tested regularly during training sessions by physiologists, fitness advisors and coaches? Explain how aerobic training reduces lactate accumulation at any given workload and yet results in a greater level of lactate accumulation during maximal efforts. What is lactic acid buffering?

Something else to consider… Study Figure 6.2. Explain the uptake of oxygen and oxygen deficit for an athlete 800m runner during an event lasting 2 minutes Study figure 6.4. Explain the oxygen debt and its two parts, fast and slow. 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 Myoglobin Worksheet

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 fatigue Predominant ES Likely causes of Fatigue Types of recovery ATP-PC Fuel depletion of ATP and PC Passive recovery Lactic Acid Accumulation of by product H+ ions Inorganic Phosphates Non dietary Active recovery Massage Hydo/water based therapies Aerobic Fuel depletion Glycogen stores, then fats Elevated body temperature Causing dehydration and blood flow away from muscles Dietary High GI Rehydration via sports drinks Non-dietary Hydro/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-products H+ ions Inorganic Phosphate 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 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 Factors Decreased 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 Refuelling: Phosphocreatine, muscle glycogen and blood glucose Metabolic by-product: Removal of H+ ions in plasma and muscles and replenishing inorganic phosphate (Pi) and Adenosine diphosphate (ADP) Addressing neuromuscular factors. Lowering body temperature.

Active vs Passive Passive PC Active Dietary refueling and hydration Removal of H+ ions Rebounding P1 to ADP Addressing nueronmuscular factors Strategies for cooling Passive PC

Refueling

Application Tasks 1. 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.aspx Record 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 findings 3.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