Physiological Adaptions in response to training − In response to training the body makes adaptions or adjustments to the level of stress imposed on it − These adaptions allow the body to function more comfortably at existing levels of stress and respond more efficiently to new levels of stress − Training will cause adaptions to a number of capacities, including resting heart rate, stroke volume, cardiac output, oxygen uptake, lung capacity, hemoglobin levels, muscle size and muscle recruitment

Resting Heart Rate − Resting heart rate (RHR) is the number of heartbeats per minute while the body is at rest and is a reliable indicator of how hard the heart is working − Typically a trained athlete will have a lower RHR than an untrained athlete due to the better efficiency of the cardiovascular system − Training decreases RHR. For example an inactive individual with a RHR of 72 bpm can expect a reduction of about 1 bpm each week for the first few months of training.

Stroke Volume − Stroke Volume (SV) is the amount of blood ejected from the left ventricle of the heart during a contraction – measured in mL/beat − SV is notably higher at maximal exercise following an endurance based program − There is more blood in circulation following training as a result of an increase in blood plasma volume, and this means that more blood can enter the ventricle − Training causes the ventricle walls to stretch and this enlarged ventricle enables contractions that are more powerful, resulting in less blood remaining in the ventricles following these contractions

Cardiac Output − Cardiac output (CO) is the amount of blood ejected from the heart per minute − Trained athletes will have a higher CO than those untrained − The trained athlete achieves a considerably higher CO not from heart rate, but as a result of a significant increase in stroke volume − Maximal values for CO, stroke volume and heart rate all decrease as we get older

Oxygen Uptake − Oxygen uptake (VO2) is the ability of the working muscles to use the oxygen being delivered to them and is significantly improved in response to aerobic training. − Maximal oxygen uptake is regarded as the best indicator of cardiorespiratory endurance as it indicates the amount of oxygen that the muscle can absorb and use at that level of work − A high VO2 max indicates a superior oxygen delivery system and contributes to outstanding endurance performance. − Females tend to have a lower VO2 than males as they are typically leaner and carry less muscle tissue which decreases their oxygen- carrying capacity.

Lung Capacity − Lung capacity refers to the amount of air that the lungs can hold − The volumes and capacities of the lungs change very little with training − Vital capacity – which is the amount of air that can be expelled after taking a deep breath in – increases slightly with training while residual volume – the amount of air that cannot be moved out of the lungs – decreases slightly. − Following training, tidal volume – the amount of air breathed in and out during respiration – is unchanged at rest and submaximal exercise. However it does appear to increase at maximal levels of exercise.

Haemoglobin level − Haemoglobin is the substance that bonds with oxygen and transports it around the body. It is contained in the red blood cells of the body. − Almost all oxygen is carried via haemoglobin with a small amount transported in body fluids such as plasma, but this amount is relatively low as oxygen does not readily dissolve in ordinary fluids. − Without haemoglobin we would need at least 80 litres of blood to carry enough oxygen around our bodies. − With training, haemoglobin levels increase which ultimately increases our oxygen-carrying capacity − An effective way of increasing haemoglobin levels is to train at high altitudes which can explain the freakish abilities of the Kenyan long distance runners − General endurance training programs can effectively increase haemoglobin levels by as much as 20%

Muscle hypertrophy − Muscle hypertrophy refers to muscle growth together with an increase in the size of muscle cells. − While length remains unchanged, the size of the muscle becomes larger as a result of an increase in its mass and cross-sectional area. − Hypertrophy is induced by training programs, particularly resistance training, which stimulate activity in muscle fibres causing them to grow. − Without this stimulation, muscle fibres can reduce in size, a condition known as atrophy − This increase in muscle size is a direct result of mass increases in:  actin and myosin filament – thin protein muscle filaments that produce muscle action  myofibrils – the contractile elements of skeletal muscle  connective tissue – tissue that surrounds and supports muscle

− The extent of hypertrophy depends on:  muscle type (fast-twitch or slow-twitch)  type of stimulus  regularity of training  availability of body hormones

Effect on fast-twitch and slow- twitch muscles − There are two types of muscle fibre:  Slow-twitch muscles fibres (ST) or red fibres – which contract slowly and for long periods of time. Used for endurance based activity such as marothons  Fast-twitch muscle fibres (FT) or white fibres – these reach peak tension quickly and are used in powerful and explosive movements such as weight-lifting or throwing − While most people have approximately even amounts of ST and FT fibres, some indivuals genetically have higher numbers of one or the other − Slow-twitch muscles are efficient in using oxygen to produce energy (ATP) which makes them resistant to fatigue but unable to produce the explosiveness of FT fibres

− Aerobic training causes the following adaptions to occur in ST muscle fibres:  hypertrophy  capillary supply – improves muscle efficiency  mitochondrial function – increases the number of mitochondria where ATP is manafactured  myoglobin content – responsible for transporting oxygen from the cell membrane to mitochondria to be later used when necessary  oxidative enzymes – the level of activity of these increases making the production of energy more efficient

− Fast-twitch fibres contract quickly but fatigue rapidly − There are two types of FT fibres:  FT(a) – are intermediate fast-twitch fibres that can produce a high output for lengthy periods.  FT(b) – possess high amounts of glycolytic enzymes and draw energy from anaerobic sources. − Anaerobic training causes the following adaptions in fast-twitch muscles fibres:  ATP/PC supply – is increased  Glycolytic enzymes – these increase, improving the functioning within cells  Hypertrophy – has the potential to be considerable and depends on the type of training, frequency and intensity  Lactic acid tolerance – increases the ability of FT fibres to tolerate lactic acid, allowing anaerobic performance to be sustained for longer periods