1215 Week 15

1215 Week 15

1. Lecture 1

   • Exercise
     • single bout of bodily exertion that requires energy expenditure
     • modality/mode - type of activity classified by energy demand or type of muscle action
     • training - consistent progression of exercise designed to improve physiological function for health or sport performance
     • endurance performance relies on the delivery of large amounts of oxygen to working muscles for prolonged periods of time
     • 3 tasks imposed on the CV system during exercise are: increased pulmonary blood flow and muscle blood flow and a stable BP
   • Facts and Figures
     • 3 stages: air to blood to ISF to mitochondria
     • the repiratory system isn't the limiting factor in exercise except in illness
     • 13 fold increase in oxygen consumption
     • to increase oxygen absorptionto meet the demand SV must be increased 1.5X and HR and arteriovenous difference 3X
     • CO and oxygen consumption have a linear relationship with CO increasing from 5L/min to 20-25 L/min
     • heart rate increases linearly to 180-200 bpm
     • sympathetic stimulation of the AV node decreases AV delay which increases HR
     • oxygen transport is limited by maximal CO and extracellular resistance to diffusion between the RBCs and muscle myoglobin
     • a 5X increase in CO leads to a 20X increase in muscle blood flow
     • vasodilation and constriction control where the blood is directed
     • normally only 1 out of 4 oxygen dissociates from haemoglobin but in exercise all 4 are dissociated
     • SV increases because EDV increases and ESV decreases increasing ejection fraction
     • increased maximal CO is due to increased ventricular wall thickness, enlarged ventricular cavities and increased myocardial vascularity
     • diffusion of oxygen into the mitcohondria is improved by new capillaries, increased mitochondria and a higher concentration of muscle myoglobin
     • changes in muscle vasculature are necessary to allow the increased CO to be used - increased capillarisation, increased opening of capillaries, effective redistribution of blood and increased blood volume
   • Training
     • an athletes maximum HR isn't altered but resting is much lower so there is a larger increase and along with an increased SV allows for a 7X increase in resting CO
     • training increases plasma volume so haematocrit decreases reducing viscosity and resistance enhancing oxygen delivery
     • muscle myoglobin binds oxygen for storage for use during the lag period between the start of aciviity and increased oxygen delivery
     • training increases mitochondria by 15%, their sixe by 35% and their oxidative enzyme activity
     • activities of succinate dehydrogenase and citrate synthase are influenced by training
     • optimal load is 80-95km running and 28-42km swimming
     • the volume of training that causes the best adaptations is an optimal amount of work performed both per bout and over a period of time
     • the degree of adaptation depends on intensity of training specific to the speed and duration of the effort performed
     • interval training is an effective way of performing high intensity training

2. Lecture 2

   • Muscle Fibres
     • type 1 - slow twitch - fatigue resistant, high endurance, low power, specialised for prolonged periods
     • type 2a - fast oxidative - rapid contraction, high oxidative capacity, not specialised for either form of exercise
     • type 2X - fast glycolytic - rapid powerful contractions, fatigue quickly, specialised for short high intensity bursts
     • an individuals fibre composition is genetically determined
     • high intensity exercise causes lactic acid production but muscle contraction compresses the blood vessels decreasing oxygen delivery and lactate removal decreasing pH leading to fatigue
     • low intensity exercise doesn't cause lactate build up so fatigue takes longer to set in and is caused by substrate depletion
   • 6 Principles of Training
     • 1 - specificity - muscles only adapt if they are trained
     • 2 - overload - muscles only adapt if they are trained at a level they aren't used to
     • 3 - progression - to maintain absolute stimulus the resistance must be continually modified for progressive overload
     • 4 - individuality - each person is different so training has to be based on pre-training status, genetic predisprosition, gender and age
     • 5 - diminishing returns - gains are related to pre-training status a novice will see a greater improvement than a trained athlete
     • 6 - reversibility - if training ceases the body will return to an untrained state
   • Energy Production and Use
     • 30 second bouts increase the activity of glycolytic enzymes
     • ATP can be generated by from phosphocreatine stores, anaerobic glycolysis and oxidative phosphorylation
     • intense brusts of muscle activity use ATP stores for about 5 seconds then phosphocreatine stores for the next 10-20 seconds
     • activity for longer than 20 seconds uses ATP produced anaerobically which produces lactic acid reducing pH which interferes with myosin crossbridges
     • in sustained moderate exercise aerobic repiration is used
     • maximal efforts of 6 seconds place the greatest demand on the ATP-PCr system
     • 30 seconds of maximal effort shows the greatest improvement to the 2 key enzymes involved in the ATP-PCr system
     • research suggests that improvements come from an increase in strength not anaerobic ATP production
     • training at high speed improves skill and coordination at high intensities which results in a more economical use of muscle ATP supply
     • anaerobic exercise improves muscles' capacity to tolerate H+ accumulation because intracellular buffer capacity increases which combined with extracellular buffering allows H+ to leave cells quicker
   • Running
     • long distance running
       • small and as light as possible
     • short distance running
       • tall and big muscles in the relevant muscle groups
       • hypertrophy of relavent muscle groups - type 2a and 2X fibres
       • higher proportion of fast twitch fibres
       • rapid reaction time
       • highly developed balance and agility
       • high capacity for anaerobic respiration

3. Lecture 3

   • Anabolic Steroids
     • androgenic anabolic steroids - involved in sexual characteristics and consist of the positive effects of testosterone: inhibiting urinary nitrogen loss and stimulating protein synthesis
     • steroid hormones are derived from cholesterol
     • have greater effects than testosterone - they help to restore muscles quicker but have androgenic effects
     • can be used clinically in men and women
     • may be useful in AIDS treatment, stimulation of prepubertal boys who are too small and terminal illnesses - stimulates appetite
     • any supply other than clinical is illegal if you intend to supply
   • Testosterone
     • formed in the Leydig cells of the testis and adrenal cortex - men produce 8 mg/day
     • testing for testosterone injections involves looking at the ratio to epitestosterone - 12% in plasma
     • in the blood 95% is bound to sex hormone binding protein
     • it acts the same as other steroid hormones
     • natural testosterone can't be taken orally or injected
     • 3 modifications are made: made suitable for depot injection, addition of an alkyl group to make it orally inactive which allows for oral dosing and increased potency
     • human chorionic gonadotrophin is used to restimulate natural testosterone production
   • Administration
     • cycling - use in periods of off and on, prefered by body builders and thought to reduce side effects
     • pyramiding - the does increases up to a peak and then decreases to nothing, thought to reduce withdrawal symptoms
     • stacking - use of more than one at a time, aims to avoid plateauing, the pharmacology is wrong though as people believe more receptor sites are stimulated when there is actually a stable number of sites
     • doages can be up to 100X the clinical dose
   • Side Effects
     • men
       • azoospermia
       • testicular atrophy
       • gynaecomastia
     • women
       • facial hair
       • deepening of voice
       • genital reconfiguration
     • men and women
       • excessive body hair
       • acne
       • anger
       • cancer
       • death
     • physiological side effects
       • increased blood volume
       • salt and water retention - raised osmotic pressure
       • hypertension
       • cardiac myopathy and hypertrophy
       • liver/kidney carcinomas
       • tendon damage
       • type 2 diabetes
     • long term
       • addiction
       • irreversible testicular atrophy
       • irreversible masculinisation - enlarged clitoris, deep voice, facial hair
       • death