TRAINING ADAPTATIONS

Lect. II

Lower heart rate during sub-maximal workloads:O Mainly a result of increased stroke volume.O The heart works more efficiently - (More

blood is pumped with each beat, and therefore the heart doesn’t have to work as hard to supply the required blood flow and oxygen supply)

O Slower increase in heart rate during exercise and a lower and faster attainment of steady state during exercise

Improved heart-rate recovery rates:O Heart rate of a trained athlete will return

to pre-exercise levels (resting rate) in a much shorter time than that of an untrained individual.

Increased cardiac output at maximum workloadsO Cardiac output – unchanged at rest and

even during sub-maximal exercise regardless of training status.

O Does increase during maximal exercise.O Maximal exercise – may increase to values

of:O · 20-22 litres per minute for untrained maleO · 15-16 litres per minute for untrainedO · 30 litres per minute or more – highly trained

athletes females

Lower blood pressure:O May lower blood pressure, especially

among people who suffer from hypertension (high blood pressure)

O Systolic and diastolic pressure levels may decrease during both rest and exercise

O Helps to reduce resistance to blood flow and reduces strain on the heart, thereby decreasing the risk of heart attack and other cardiovascular conditions

OThe arteriovenous oxygen difference, or a-vO2 diff, is the difference in the oxygen content of the blood between the arterial blood and the venous blood. It is an indication of how much oxygen is removed from the blood in capillaries as the blood circulates in the body.

Increased arterio-venous oxygen difference (a-VO2 diff):O Trained individuals are able to absorb

more oxygen from their bloodstream into their muscles during exercise performance compared to untrained subjects.

O This is due to:O · Increased muscle myoglobin storesO · Increased number and size of

mitochondria within their muscles

O As a result of this, the concentration of oxygen within the venous blood is lower

O Subsequently the arterio-venous oxygen difference is increased during both sub-max and maximal exercise

O Therefore, and increased arterio-venous oxygen difference (a-VO2 diff) indicates a greater uptake of oxygen by the muscles with trained individuals

Increased blood volume and haemoglobin levels:

O Total blood volume may rise by up to 25% (from 5.25L to 6.6L) for an average adult male with regular and sustained aerobic training.

O Red blood cells may increase in number and the haemoglobin content and oxygencarrying capacity of the blood may also rise.

Increased capillarisation of skeletal muscle:

The average number of capillaries supplying each muscle fibers is:

O · 5.9 for trained athletesO · 4.4 for untrained athletes

Changes to blood cholesterol, triglycerides, low- and high-density lipoprotein levels:

O Results may include a decrease in blood cholesterol levels, triglycerides and low density lipoprotein (LDL).

O These substances are associated with the development of coronary heart disease.

O Aerobic training increases the ratio of high-density lipo-protein (HDL) to low-density lipoprotein.

O High-density lipoprotein is thought to provide a coronary protective effect, lessening the risk of developing coronary heart disease.

SUMMARY CV adaptations

Respiratory Adaptations

B) RESPIRATORY ADAPTATIONS to aerobic training

O More efficient and improved lung ventilationO At rest and during sub-maximal exercise,

ventilation may be reduced due to improved oxygen extraction

O However, during maximal workloads, ventilation is increased because of increased tidal volume (amount of air breathed in and out in one breath) and respiratory frequency (the number of breaths taken per minute).

O Pulmonary diffusion (the ability of the blood to extract oxygen from the alveoli) is also enhanced.

Increased maximum oxygen uptake (VO2 max)O Increase in the maximum oxygen uptake

(VO2 max) during maximal exerciseO Improvement can be between 5–30%

following a regular and sustained training program

This occurs because of adaptations such · Increased cardiac output

O · Increased red blood cell numbersO · Increased a-VO2 differenceO · Increased muscle capillarisationO · Greater oxygen extraction by the

muscles as:

Increased anaerobic or lactate thresholdO As a result of the adaptations that

improve oxygen delivery and utilisation in the muscles, a higher lactate threshold (the point at which oxygen supply cannot keep up with oxygen demand) is developed.

Advantage:O The anaerobic glycolysis (lactic acid)

system is not utilised as much until higher exercise intensities are reached.

O Consequently, lactic acid and hydrogen ion accumulation will be delayed until these higher work-load intensities are attained

O The athlete can “work harder and for longer periods”

Muscle Tissue Adaptations to Aerobic (Endurance) Training:O Chronic aerobic training adaptations

within muscular tissue are best produced through continuous training or high-repetition resistance training

O The following tissue-level changes can be observed within skeletal muscles following extensive endurance training:

Increased oxygen utilisation:

O Aerobic training enhances the body’s ability to attract oxygen into the muscle cells and

O then utilise it to produce adenosine triphosphate (ATP) for muscle contraction

O This process occurs in the following ways:

O · Increased size and number of mitochondria –

O Mitochondria are the site of ATP synthesis and where glycogen and triglyceride stores are oxidised (Greater oxidisation of fuels to produce ATP)

O · Increased myoglobin stores – Myoglobin is the substance in the muscle cell that attracts oxygen from the bloodstream into the muscle. (Increase ability to extract oxygen)

Increased muscular fuel stores:O Increase in the muscular storage of

glycogen, free fatty acids and triglycerides, along with the oxidative enzymes required to metabolise these fuel stores and produce ATP.

Increased oxidation of glucose and fats:O The muscular adaptations result in an increase in

the capacity of muscle fibers to oxidate both glucose and fats

O The capacity of the aerobic system to metabolise these fuels is increased

O Increased oxidation of fats as a fuel source; due to:O · Increased storage of triglycerides and free fatty

acidsO · Increased levels of enzymes associated with fat

metabolism

Means that:O At any given exercise intensity, a trained

individual has to rely less on glycogen, thereby “sparing” glycogen stores (Glycogen sparing)

O Therefore delaying the time to exhaustion due to glycogen depletion.

Decreased utilisation of the anaerobic glycolysis (lactic acid) system:O The enhanced capacity of the muscles to

aerobically metabolise glucose and fats and other muscular level adaptations also means that there is less reliance upon the anaerobic glycolysis system to produce energy for ATP resynthesis until higher exercise intensities are reached.O · Allows athletes to work at higher intensities

without exceeding lactate threshold.O OR

O · Aerobic training results in an increase in the lactate threshold

O Eg. An athlete must run at a faster pace in order to accumulate the same amount of blood lactic acid as before training

O Muscle- fiber type adaptation:O Some research has shown evidence that

skeletal muscle switches fiber types from fast twitch to slow twitch as a result of endurance training.

O Skeletal muscle fibers are classified into three types:O Type 1 – Slow-twitch oxidative fibers:

O · Contain large amounts of myoglobin, and large numbers of mitochondria and blood capillaries.

O RedO · Split ATP at a slow rateO · Slow contraction velocityO · Very resistant to fatigueO · High capacity to generate ATP by

oxidative metabolic processes.

O Type 2A – Fast-twitch oxidative fibers:O · Contain an extremely large amount of

myoglobin, and huge numbers of mitochondria and blood capillaries.

O · RedO · Very high capacity for generating ATP by

oxidative metabolic processesO · Split ATP at a very rapid rateO · Fast contraction velocityO · Resistant to fatigue

OType 2B – Fast-twitch glycolytic fibres:O · Contain low myoglobin content, relatively few

mitochondria and blood capillaries, and large amounts of glycogen

O · WhiteO · Geared to generate ATP by anaerobic metabolic

processesO · Fatigue easilyO · Split ATP at a fast rateO · Fast contraction velocity

O Individual muscles are a mixture of the three types of muscle fibers, but their proportions vary depending on the action of the muscle and the genetic make-up of the individual

Summary of muscle tissue adaptations to aerobic (endurance) training:

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