Fatigue and the recovery process

Introduction

After a strenuous exercise the athlete needs to develop an effective recovery process to; replenishment of ATP, removal of lactic acid, replenishment of myoglobin with oxygen and replenishment of glycogen. This may take 24 hours depending upon the intensity and duration of the activity undertaken

Content

  • Recovery process

Recovery Process

The main aim of the Recovery Process is to restore the body to its pre-exercise state. This involves the removal of by-products produced during exercise and replenish the fuels used up during exercise

Excess Post-exercise Oxygen Consumption (EPOC – formerly known as Oxygen Debt).

‘This is the excess oxygen consumption, above that at a resting level, during recovery, to restore the body to its pre-exercise state’ (which is why our Respiratory Rate remains elevated after exercise).

Below is a graph that shows EPOC with two stages of recovery:

  • The initial rapid recovery stage (Alactacid Debt)
  • The slow recovery stage (Lactacid Debt)
% of maximum rate of energy production

Oxygen deficit can be thought of as the extra amount of oxygen that would be needed to complete the entire activity Aerobically

Alactacid debt (Rapid recovery stage)

  • This is also termed the Restoration of Phosphogen Stores as the elevated respiration primarily helps resynthesise the muscles’ store of ATP and PC
  • This also helps replenish the muscle stores of MYOGLOBIN and Haemoglobin
  • MYOGLOBIN
    • This is a Protein, similar to Haemoglobin (helping to transport oxygen) and is found in the muscle sarcoplasm
    • They store oxygen before transferring it to the mitochondria for aerobic respiration
    • During recovery, with elevated heart and ventilation rates, there is a surplus of O2 available for Myoglobin to be replenished with oxygen
  • It takes 3 minutes for the ATP/PC stores to fully recover (in about 30 seconds for 50% of recovery and about 75% recovery in 60 seconds)
  • This process also uses 3-4 litres of oxygen

A – Alactic component

  • This system repays the CREATINE PHOSPHTE.
  • It takes approximately 30secs to repay 50% of your CP stores with 98% getting repaid after 3mins. This information is vital to a coach or athlete when looking at recovery times for power events and exercises.

OXYGEN DEFICIT can be thought of as the extra amount of oxygen that would be needed to complete the entire activity Aerobically

Recovery Time(seconds) CP recovery (%)
15 60
30 70
45 80
1 min 85
2 min 90
4 min 97

Lactacid debt (Slow recovery stage)

  • This is primarily responsible for the removal/re-conversion of lactic acid/lactate.
  • Early research findings suggest that Lactic Acid can be converted into:
    • Pyruvic Acid, to enter the Krebs’ Cycle and used as a metabolic fuel
    • Glycogen/Glucose
    • Proteins
  • It is now thought that a significant percentage of EPOC is to support the elevated metabolism functions taking place after exercise, including:)
    • High body temperatures remain for several hours after vigorous exercise
    • Hormones, like adrenaline, remain in the blood stimulating metabolism
    • Cardiac Output remains high, helping to reduce temperature
  • This stage requires about 5-8 litres of oxygen and can remove lactic acid from between 1 and 24 hours after exercise, depending on the exercise intensity and the levels of lactic acid that have to be removed

B – Lactacid component

  • This repays the muscle glycogen in the anaerobic glycolysis energy system.
  • Oxygen also removes the lactic acid.
  • There are four possible fates Lactic acid when broken down by oxygen.
    • Excretion in urine and sweat
    • Conversion back to glucose and glycogen (this why a cool down is so important)
    • Conversion to protein
    • Conversion to carbon dioxide and water
  • The oxygen also re-saturates the myoglobin stores. (myoglobin is a concentrated form of haemoglobin, which carries the oxygenated red blood cells into the working muscles.
  • Oxygen deficit also has to be re-paid, oxygen deficit occurs as we begin to exercise. The aerobic system does not work quickly enough to supply energy at the start of physical activity, (it’s like an engine starting slowly and beginning to warm up) hence the body gets its energy anaerobically, which has to be re-paid.

General points about recovery

  • EPOC will always be present at any exercise intensity
  • Oxygen Deficit (shortage of O2 supply during exercise) and EPOC are both lower during aerobic activity than anaerobic activity
  • Aerobic exercise shows a steady state where oxygen supply (VO2) meets the requirements of the exercise and therefore has a smaller EPOC (by having only a small oxygen deficit and not producing high levels of lactic acid that require removal) – see Figure a on page 385.
  • Anaerobic exercise shows that a steady state of aerobic work cannot be maintained so the oxygen supply is lower than the exercise requirements – see Figure b on page 385.
  • This increases the oxygen deficit and OBLA, producing high levels of lactic acid requiring removal and therefore a higher EPOC as it takes longer for oxygen consumption to return to pre-exercise levels.

Removal of carbon dioxide

  • The increased concentration of CO2 (waste product) produced as a by-product of respiration during exercise. CO2 is removed in the following ways:
    • by combining with water in the blood plasma within red blood cells to form Carbonic Acid (H2CO3)
    • by combining with haemoglobin in the red blood cells to form Carbaminohaemoglobin (HbCO2)
    • Both of these are taken to the lungs to be expired
  • High metabolic functions along with chemoreceptors detecting elevated levels of CO2 stimulate the cardiac and respiratory control centres which ensures the respiration and heart rate remain elevated to help aid the removal of CO2

Replenishment of glycogen stores

  • After exercise, Glycogen stores in the Liver and Muscles will be depleted, which is a major factor in muscle fatigue
  • A large percentage of glycogen can be replaced up to 10-12 hours after exercise, but complete recovery can take up to two days in prolonged endurance exercise
  • Fast twitch muscle fibres can replenish glycogen stores quicker than slow twitch fibres
  • Glycogen restoration can be almost completely recovered if a high carbohydrate diet is consumed, especially when eaten within the first two hours of recovery
  • Many athletes replenish glycogen stores by consuming carbohydrate-rich drinks. This is thought to be quicker to break down and more easily ingested than food such as pasta immediately after exercise

Implications of recovery for planning physical activity sessions

  • We need to understand the recovery process to help provide guidelines for planning training sessions in order to take into account the work intensity and recovery intervals – this uses Interval Training
  • Having correct work-relief during interval training is more efficient as it:
    • Increases the quality/intensity of training
    • Improves energy system adaptations
  • By altering the work-relief intervals, the training can target specific energy systems appropriate to the performer.
  • For training aimed at improving speed, using the ATP/PC System
    • Work ratio = may be less than 10 seconds
    • Relief ratio = is normally longer (1 : 3; Work : Relief) e.g. work for 10 seconds, relief for 30 seconds
    • This allows time for the ATP and PC stores to fully recover (2-3 mins)
  • For training aimed at improving the body’s tolerance to lactate to improve speed endurance using the lactic acid system, could either:
    • Keep the work ratio to less than 10 seconds but decrease the duration of the relief ratio (e.g. 1 : 2 – which means only 50% ATP/PC restoration in 30 seconds)
    • Increase the duration of the work ratio, which both increases lactate production and overloads the lactic acid system
  • For training aimed at improving a performer’s VO2 max using the aerobic system
    • The work-relief ratio is normally longer in duration and intensity, just below the anaerobic threshold
    • The relief ratio is typically shorter (1 : 1), which helps reduce the OBLA and delay muscle fatigue and therefore prolong the aerobic system adaptations

General recovery training applications

  • Warm up thoroughly before training. This will help reduce Oxygen Deficit by increasing O2 supply to the working muscles and ensure myoglobin stores are full
  • Use an active cool down during recovery from anaerobic work where lactic acid is accumulated. This speeds up the removal of Lactic Acid.
  • A moderate intensity seems optimal for the active recovery to be effective. About 35-45% of VO2 max seems to be the best intensity for this to happen for cycling and 55-60% of VO2 max for running (but depends on the individual)
  • During steady state aerobic exercise where little lactic acid is produced, a more passive recovery has been shown to speed up recovery more than an active recovery. Active recovery elevates metabolism and will delay recovery in this instance
  • Anaerobic speed/lactate tolerance training will both help to increase ATP and PC muscle stores
  • Ensure that the work/rest ratio’s are correct and maintained
  • Use tactics or pacing to control/alter intensity to meet the training objectives
  • Aerobic training will help improve oxygen supply during and after recovery from exercise
  • A mix of aerobic and anaerobic training will help delay the ATP/PC and lactic acid thresholds
  • Use heart rate as an indicator of exercise intensity, OBLA threshold and recovery state, as heart rate mirrors respiratory recovery

Methods to Speed up Recovery Process

a. Cool down.

By cooling down and exercising at a low intensity (jogging etc) then more oxygen is getting taken in to the muscles. This means creatine phosphate stores will replenish at a faster rate. The more oxygen that is present then the quicker the body can remove lactic acid and turn it back into energy and re-saturate the myoglobin stores

b. Eating a high carbohydrate meal within 30 mins post exercise

The optimum time for the body to take up carbohydrate is within 30 minutes of finishing exercise. By eating High Glycaemic Index carbohydrate (carbohydrate that release energy quickly e.g. sugary foods) and Low Glycaemic Index (Carbohydrate that release energy at a slower rate e.g. fruit, wholemeal bread, wholemeal pasta and rice) Then the body is able to begin restore the glycogen used over exercise period. (See nutrition)

c. Recovery supplements

The use of recovery supplements is widely used in sport for recovery purposes. They often contain a mix of carbohydrate (to re-supply the glycogen stores), protein and amino acids, (for growth and repair of the muscle) and creatine (Help restore CP stores)

d. Ice baths

The theory behind ice baths is that when we exercise at a high intensity small micro-tears occur in the muscles. Some research believes that it is these micro-tears that cause Delayed Onset of Muscle Soreness (DOMS) or at least the swelling that takes place around the micro-tears. It is believed that Ice Baths reduce the swelling around the muscle micro-tears and reduce the pain that they cause, this means that the performer is able to train at a higher level the next day. It must be noted that research on this is not conclusive.

e. Massage

Massage can serve two purposes; the first is psychological benefits e.g. relaxing feeling of the massage and the fact that it can be invigorating, (providing it is not a deep muscle massage).

Secondly it can help physically by returning de-oxygenated blood from the muscle tissue to the heart to be re-oxygenated.

f. Compression Clothing

Recent studies have concluded that compression clothing can help recovery by maximising the pumping action of the muscles in returning blood to the heart and help with subsequent removal of lactic acid and blood lactate.

There must be an understanding in the difference between alactic and lactacid oxygen debt and specifically what each system repays/removes. The candidate must also be able to provide specific examples of how the methods to speed up recovery and why each are used.

EXample 1 Cool down keeps oxygen levels elevated and therefore this means that more lactic acid can be removed (speeds up lactacid recovery) and then converted back into glucose/glycogen. Also the cool down can speed up the re-saturation of myoglobin.

Example 2 A high carbohydrate meal including protein can help restore muscle glycogen and blood glucose levels. The optimum time for uptake of glycogen into muscles is within 30mins of ceasing exercise. Protein can help repair damaged muscle tissue and help re-growth. (See nutrition/hydration section for more details of optimising recovery)

Exam Style Questions

1. Explain the terms alactic and lactacid oxygen debt and describe the strategies you have used to speed up these recovery processes. (6)

2. High anaerobic capacity is essential to any team gamer player. Outline the physiological processes that will happen during a 5-minute recovery period after intense anaerobic exercise (5)

3. Cool down is an essential aspect of the recovery process. Provide an example of an appropriate cool down for your sporting activity and explain the physiological benefits to the performer. (5)

Quick Check

  • EPOC is the repaying of energy after anaerobic exercise
  • There are two components of oxygen debt. Alactic and Lactacid.
  • Alactic replenishes the CP stores (takes approx 4 mins to replenish 97% of the CP)
  • Lactacid primarily replenishes the stored glycogen and removes lactic acid
  • Higher levels of aerobic fitness can result in quicker repayment of oxygen debt
  • There are a number of methods to speed up the recovery process including: - cool down, ice baths, correct nutrition and hydration, compression clothing and massage.