EXERCISE PHYSIOLOGY - RESPONSE AND ADAPTATION

RESPONSES TO EXCERICE

CARDIOVASCULAR 

  1. increased heart rate 

  • may include anticipatory increase in HR due to a release of epinephrine 

  • the resting HR is 60-70 BPM at rest but can go up to 200 BPM during very intense work

this is all caused by the medulla oblongata responding to the CO2 in the blood causing the SA node to increase the impulse frequency 

  1. increased stroke volume 

  • SV increasing with exercise intensity up to 40-60% of VO2 max

  • further increase in cardiac output at high intensities are achieved mainly through increases in HR

at maximal intensities SV may decline slightly due to the fact very high HR shorten diastolic filling time which limits end-diastolic volume 

  1. blood pressure 

blood pressure (BP) - mmHg= cardiac output (Q) - L-min-1x total peripheral resistance (TPR) - mmHg-min-L-1 

  • systolic blood pressure rises proportionally with exercise due to increased cardiac output

  • diastolic pressure shows little or no change and may slightly decrease which reflects the vasodilation in active muscles which will lower peripheral resistance 

  • with endurance training, resting and submaximal exercise blood pressure are often reduced but blood pressure responses at maximal intensity are similar as cardiac output and total peripheral resistance still reach high physiological limits 

  1. redistribution of blood flow 

  • most of the blood is directed to areas of greatest primary need

    • nerve cells in the brain 

    • contracting muscles

    • skin to release heat produced 

  1. vasodilation and vasoconstriction 

  • increased activity stimulates the contraction of the smooth muscle cells (vasoconstriction) which decrease blood flow to organs and

  • in the contracting muscles, substances such as nitric oxide and adenosine are released and produce an opposite effect 

  1. cardiac hypertrophy 

= increase in size and strength of myocardium 

  • endurance training causes eccentric hypertrophy

    • increased chamber size and wall thickness 

  • strength training causes concentric hypertrophy 

    • less change in chamber size compared to endurance training but increased wall thickness 

  1. decrease in resting heart rate 

  1. increase in blood volume 

  • blood plasma volume expansion 

  • red blood cell production 

  • enhanced heat dissipation 

VENTILATORY AND RESPIRATORY 

OXYGEN UPTAKE (L/min) = volume (L) of oxygen taken up by the body per minute 

there is a rapid increase in VO2 at onset of exercise however there is O2 deficit due to lag in O2 uptake with anaerobic systems contributing to total ATP supply 

there is steady state VO2 in 1-4 minutes

O2 demand by tissues are met by O2 delivery by muscle blood flow 

the ATP requirement is fully met by aerobic energy system 

VO2 MAX - MAXIMAL OXYGEN UPTAKE 

the maximal rate at which an individual can take up and utilise oxygen while breathing air at sea-level 

males = 30-55ml-kg-min-1

females = 25-40ml-kg-min-1

training increases VO2max and active older people can have a higher VO2max then inactive younger people 

training slows the decline in VO2max that inevitably occurs with age 

A-V O2 DIFFERENCE = ARTERIO-VENOUS OXYGEN DIFFERENCE 

the amount of oxygen extracted by tissues from the blood as it passes through the capillaries = difference in oxygen content in arterial blood and venous blood 

higher A-V O2 difference = more extraction of oxygen which is common during intense exercise 

MUSCULAR 

  • hypertrophy 

  • metabolic adaptations 

  • increased strength increased capillarisation 

  • increased mitochondrial density and size 

  • increased myoglobin 

  • increased glycogen and triglyceride stores

  • increased coordination and motor unit recruitment

  • increased connective tissue strength 

untrained individuals 

  • have relatively even distribution of type I and II fibres 

with endurance training 

  • some type IIx fibres show greater oxidative capacity and become more like type IIa

  • there may be an relative increase in type I characteristics due to enhanced mitochondrial density and capillarisation 

  • potential trade off as - improved endurance but slight reduction in maximal power output  

with power or sprint training 

  • muscles adapt towards type II dominance

  • contract quickly and generate high force but fatigue rapidly 

  • low proportion of type I fibres 

ENERGY SYSTEMS

energy turnover = the process by which energy is produced, utilised and replenished within cells and tissues in the body 

  1. aerobic / oxidative system 

  • gradually increased ATP production to meet the demands of sustained, moderate-to-high intensity activity 

  • relies on oxygen and primarily uses carbohydrates and fats as fuel 

  • during prolonged exercise the body begins to rely more on fats as a fuel source

  1. anaerobic glycolytic / lactic acid system 

  • after the ATP-PC system is depleted the anaerobic glycolytic system then supplies ATP at a faster rate than the aerobic system but produces less ATP per glucose molecule 

  • lactate build up raises H ions which lowers cell pH, increasing acidity and leading to muscle fatigue 

  • sustain intense exercise for up to 2 minutes 

  1. ATP-PC / phosphagen energy system 

  • the bodies immediate need for ATP is met by the phosphagen system 

  • uses the stored amount of ATP in the muscles which only lasts for 1-2 seconds

  • when the ATP is depleted the body converts creatine phosphate into additional ATP which can sustain high-intensity activity for approximately 8-10 seconds

  • once PCR (phosphocreatine) stores are depleted the body shifts to the other energy systems 

  • full recovery of creatine phosphate stores take about 2-3 minutes