Exercise Physiology 2

Fatigue and Recovery

Fatigue is a temporary loss of strength and energy resulting from hard physical or mental work.

Causes of fatigue• Depletion of energy stores

o ATP/PC stores depleted rapidly – muscle switches to lactic acid system

o Depletion of glycogen stores (approx. 2 hours) – fats become predominate fuel and require more oxygen

• Accumulation of lactic acido During high intensity activities the accumulation of lactic acid to

high levels interferes with the contractile mechanisms within the muscle fibres

• Restricted blood flowo Reduces oxygen supply to working muscles

• Dehydrationo Reduces blood volume, restricts blood flow, reducing fuel and

oxygen supply to working muscles• Rising body temperature

o If body temperature not controlled, body will begin to shut down• Psychological factors

o Physiological influences may cause person to cease exercise before they reach physiological limits

Fatigue and Recovery

Recovery Recovery commences once exercise has ceased. Initially in recovery ventilation remains elevated, which is identified through an increased rate and depth of breathing. EPOC

The oxygen consumed in recovery above resting levels

 Phase 1 – Alactacid Debt• Oxygen consumed is used to replenish CP stores• 50% replenishment in 30 seconds• 100% replenishment in 3 minutes

 Phase 2• Oxygen consumed is used to breakdown lactic acid (2

hours)• Size of debt is dependent on the intensity and duration

of the exercise

Fatigue and Recovery

Active RecoveryPromotes removal of accumulated lactic acidPrevents venous pooling of blood Replenish glycogen storesConsume complex carbohydratesRestoration of stores can take up to 48 hours Replenish fluidsWater provides adequate rehydration Include rest daysEnables recovery and replenishment of energy stores

Re-establish Body Temperature

Muscle Soreness

Acute• Occurs after intense anaerobic exercise• Associated with accumulation of lactic acid in the

muscles – toxic waste not able to be removed until recovery• Removal of lactic acid takes about one hour –

active recovery promotes the breakdown• Cold Water immersion increases lactic acid

removal Delayed onset of muscle soreness (DOMS)• Felt as muscle discomfort often after participating

in unaccustomed physical activities• Soreness intensifies in first 24 hours, peaks up to

three days, generally subsides after a week• Associated with unfamiliar explosive efforts –

particularly eccentric contractions (require actin-myosin crossbridges to be forcibly separated)

Muscle Soreness

Causes• Connective tissue damage – tension develops

during eccentric contractions and can cause mechanical strain due to overstretching of the muscles elastic components• Muscle damage• Inflammation – disruption of the Z band leads to

swelling, exerting pressure on the muscle fibres Prevention / Treatment• Stretching – delay or alleviate pain – hold for 30

seconds plus• Cold treatment – decreases inflammation, pain and

spasm associated with stretch reflex• Ultrasound• Pharmacological agents – anti-inflammatory, drugs

(aspirin) reduce DOMS.

Temperature RegulationNormal Body temperature is 37°C. The core

of the body remains at this temperature due to a balance between heat entering and heat leaving the body.

HEAT GAIN = HEAT LOSS

Skin temperature is different to body temperature. It is a product of:• Environment• Clothing• Quantity of body fluid• Whether at rest or exercise

Thermal Death Point

Thermal death point is only 7°C either side of the body’s “reference” temperature.

Temperature Regulation Control

The hypothalamus is the body’s thermostat. If the body’s temperature goes above or below 37°C it will react.

The hypothalamus acts as a thermometer inside of the body. It sends messages to the heating and cooling systems of the body, which react to re-establish the normal internal temperature.

Heat balanceHEAT BALANCE

HEAT PRODUCTION HEAT LOSS

Metabolism

Voluntary Exercise

Involuntary Exercise

(shivering)

Radiation

Conduction

Convection

Evaporation

The body loses and gains heat in order to maintain a heat balance.

Heat Loss

Radiation – Heat loss through infrared rays. The greater the difference between the body’s heat and the environment, the greater the radiated heat loss.

Conduction – Transfer of heat through contact

Convection – Transfer of heat by a moving fluid (hot air rises)

Evaporation – Sweating

Exercise in the heatWhen at rest the core body temperature is

37°C. Muscle temperature however, changes between 25°C and 33°C depending on environmental temperature. Muscle temperature increases during exercise.

Exercise in the heat makes it difficult for the body to maintain it’s heat balance, and the body’s water requirement greatly increases.

Through perspiration, the body loses its major cooling aid being water (0.5L to 4.2 L per hour may be lost.)

Sweating is a result of increased muscle temperature. Continuous exercise and inadequate fluid replacement results in rises in core temperature.

For every 1% loss of body weight there is a 0.1°C increase in core temperature.

Symptoms of water loss

1% loss causes thirst 5% loss causes discomfort 7% loss is dangerous 10% loss results in the breakdown of

coordination and all movements are difficult.

15% loss results in the athlete becoming delirious

20% loss is the upper limit of dehydration before death.

DEHYDRATION

Increase in pulse rate

Decrease in blood pressure

Decline in circulatory function Increase in core body temperature

Decrease in blood pressure

Heat disorders1. Dehydration – Excessive loss of water which results

in thirst to circulatory problems to muscle meltdown to death

2. Heat Cramps – Involuntary cramping of muscle groups as a result of dehydration

3. Heat Exhaustion – Caused by the inability of the circulatory system to function properly in the absence of sufficient water

Warning signs are:• Profuse sweating• Paleness• Fast and shallowing breathing• Rapid and weak pulse• Cool and moist skin• Faintness• Disorientation

What to do:– Help person to cool off– Use cool, non-alcoholic beverages– Rest– Cool shower, bath or sponge bath– Lightweight clothing– Air conditioned room– If symptoms worsen or last longer than 1 hour seek medical attention

4. Heat Stroke – the temperature regulatory system breaks down and the core body temperature rises over 41°C within ten to fifteen minutes

Warning signs are:– Confusion– Little or no sweat with red, hot dry skin– Rapid, strong pulse– Throbbing headache– Unconsciousness– Nausea

What to do:– Get person to shady or air-conditioned area– Cool person immediately using whatever methods you can. For example,

immerse in a tub of cool water, cool shower, spray with garden hose or if humidity is low wrap person in a cool wet sheet and fan them.

– Seek medical assistance as soon as possible

Methods for dealing with heat during exercise

• Drink plenty of water• Replace salt and minerals• Wear appropriate clothing and

sunscreen• Schedule outdoor and indoor

activities carefully• Acclimatisation• Train with others• Stay cool indoors• Monitor those at high risk: infants

and children up to 4 years, people 65 years of age or older, overweight people, the ill or those who take medications and people who overexert during work or exercise.

Exercise in the cold

Dangers of exercising in the cold are greater than those for exercising in the heat.

There are only limited means of short-term acclimatisation to reduce the impact of cold on exercise performance.

This includes vasoconstriction, which limits the blood flow to the skin to avoid cold injury.

Shivering is also a form of gaining heat, but it can hinder performance as it fatigues muscle activity and reduces motor skill level.

Methods to reduce the effects of cold while exercising are:

Multiple layers of thin, wind / waterproof, breathable clothing, which may be adjusted to the level of activity. Remove outside layers before sweating commences into thin layers. Cover the head, as it is a very high area of heat loss. Make sure the extremities are covered to prevent frostbite.

If possible train indoors or in areas away from the wind and cold temperatures.

Food increases metabolism and digestion increases heat production. Eat foods containing protein, as it has a high specific dynamic index (SDA) and makes you warmest out of all of the types of food.

Must keep the intake of fluids up, as cold air cannot hold moisture.

Respiration – try to cover the mouth and nose, as cold / dry air must be warmed / humidified eg wear a scarf

Try to exercise in the middle of the day when the air temperature is at its highest and when there is the greatest radiant heat.

If it doesn’t compromise performance, putting on extra fat acts as insulation against the cold conditions eg Susie Maroney

Hypothermia – occurs when the core body temperature is below 35°C. It is characterised by the ‘stumbles and mumbles’.

Results in low blood sugar levels, hypoventilation, acid / base disturbances, loss of protein from damaged cells and eventually cardiac failure

Treatment:• Remove from cold environment and use dry

clothing• Slow re-warming – use body heat, drinks and

pre-warmed air• No hot showers or baths, warm from inside

out and do not massage hands and feet vigorously.

Exercise at altitude

Exercise at altitude can have a major effect on performance

Endurance performance is usually diminished and anaerobic performance unaffected. This is because ascent to altitude results in lower oxygen in inspired air, and therefore less oxygen delivery to active muscles.

The percentage of oxygen in the air is at the same at sea level, but the total amount of air is less.

A moderate altitude around 15oom can start to affect the athlete, and over 5000m can be extreme.

An increase of altitude results in a decrease of 2°C per 300m, so the cold also has to be dealt with.

Physiological responses to exercise:

Decreased arterial oxygen content Increased ventilation Increased CO2 output Increased stroke volume Decreased sub-max HR Decreased VO2 max Progressive dehydration – increased

breathing of colder / dryer air and increased urine.

Overcoming the effects of altitude

Live high / train low – maximise the resting adaptations to altitude and minimise the disruption to training caused by altitude

Daily transit – between high and low altitude Nitrogen houses – decreases O2 in the air by increasing

nitrogen. Mimic high altitude conditions and you can set the height you require

Altitude tents – portable and have a decreased O2.

Acclimatisation at Altitude

Adaptations occur over 2 – 3 weeks:Increased red blood cell concentration – over days due to dehydration and weeks / months due to increased cell production

Partial restoration of plasma volume Increased muscle capillarisation Increased muscle enzyme activity

Altitude SicknessThis generally occurs above 3000m and is most likely to happen in:

– Unacclimatised individuals– After rapid ascent– In combination with exercise

Symptoms:– Headache– Dizziness– Nausea– Sleep disturbances due to cardiovascular responses to

hyperventilation

* Pulmonary / cerebral edema may occur in extreme circumstances and requires immediate return to lower altitudes.

Exercise Under Water

Effects of Pollution on Exercise

Many cities in the world have severe pollution problems, which have a negative effect on performance – there is little you can do. However, try:Exercise in large parks away from major traffic areas where possibleExercise at times that correspond to low traffic periods

Travel and Sports Performance

Additional stress may be placed on athletes and their bodies because of the effects of travel and different environmental conditions at the destination. Jet LagYour body has a normal rhythm of sleep and wake which is often disrupted when you travel across many time zones – this can have a negative effect on performance.Ways to prevent the negative effects of jet lag:• If possible plan your trip so that you have several shorter legs of

the journey – once you have adjusted to one place move on to the next. This is obviously time consuming and expensive and may outweigh the negative effects.

• When travelling by air drink plenty of water and avoid alcohol and caffeine. Dehydration is a symptom of jet lag due to the air conditioned planes.

• Before you leave or when you arrive at your destination try and adjust your sleep-wake patterns to match your destination.

• Try and plan to arrive at your destination in the morning and then stay awake for the remainder of the day, sleeping in the dark. Avoid napping as it will prolong your adjustment to the time zone.

• Expose yourself to sunlight as the chemicals in the body that effect sleep are affected by sunlight.

• If possible exercise lightly for the first few days until your body has adjusted.

Travel and Sports Performance

Overseas trips, international competitions or training camps often provide nutritional challenges for athletes – poor planning often results in poor performance. The following tips can help you prepare:• pack a small supply of your favourite convenient foods, they are

not often available overseas• organise meals in advance• be sure to make nutritious CHO rich choices when travelling• airlines often have ‘athlete’ meals – organise in advance to have

extra bread rolls and fruit juice and take along your own water bottle

• when travelling by road do not rely on petrol station food• avoid or minimise alcohol intake when travelling (particularly on

long flights or in air-conditioned buses or trains)• when travelling overseas be prepared to try different CHO foods

as traditional ones are not always available• when travelling to exotic locations drink bottled water• ‘Travellers trot’ is common in athletes when they travel to

countries with suspect water supplies. In this case it is imperative to maintain adequate fluid intake (bottled water is best), avoid milk and cheese and gradually introduce foods once symptoms settle. Suitable food choices include; white bread (toast) or rice, broth, low fibre cereals with low fat milk, dilute fruit juice, soft drinks, cordial or sports drinks