U3 VCE PE MUSCULAR FATIGUE MECHANISMS AND NUTRITION & HYDRATION STRATEGIES

fatigue, fuel depletion, accumulation of metabolic by-products, thermoregulation, nutritional and hydration strategies.

exercise-induced fatigue

dec. capacity or inability to maintain a given force production or power output.

fatigue is multifactorial

• fuel depletion, accumulation of metabolic by-products, thermoregulatory fatigue

Fatigue can be seen when:

• inc. time taken to complete distance

• dec. in distance covered in particular time

fuel depletion fatigue mechanisms

ATP

• energy demand inc. = rate of ATP breakdown inc.

• ATP depletion → dec. in power output.

CREATINE PHOSPHATE (CP)

• ATP-CP system fatigue mechanism - working maximally.

• ATP-CP sustain activity for 6-10s, CP will deplete rapidly.

  • when CP deplete → anagly system inc. contribution = slower rate of ATP being made than ATP-CP system = dec power.

• CP depletion is slower in lower intensity activities that arent maximal.

RECOVERY STRAT

• passive recovery via aerobic system. 3min 98%, 30s 70% CP

GLYCOGEN

• occurs during sustained aerobic work in endurance events.

• trained athletes can utilise fats for longer than untrained.

• glycogen stores can sustain activity for 90min-2hrs. When it depletes, fats is main source (triglyceride)

  • trigly → slower rate than glycogen = fatigue = slow down performance

accumulation of metabolic by-products

ADP+PI → ATP-CP system

• inorganic phosphate (Pi) accumulates during maximal-intensity work

• Pi comes from CP splitting. Pi slows down muscle contraction = dec. force & power output

LACTATE & H+ → anagly system

• incomplete breakdown of o2 = lactic acid → lactate & H+ ions

• lactate shuttle to be fuel again, When H+ & lactate produced at faster rate than removed during high intensity → pH muscle changes = acidic = impair glycolytic enzyme → fatigue, slow down etc.

RECOVERY STRAT

• active recovery for anagly system.

lactate inflection point (LIP)

final point where lactate production = lactate removal .

• lip is passed = aerobic system cant remove lactate fast as produced = inc. contribution from anagly system → rise in blood lactate → accumulation of metabolic by-products & fatigue

• higher LIP = Higher intensity athlete can work at aerobically

thermoregulatory fatigue

fatigue resulting from inability to maintain a stable body temp.

• body temp to be constant → heat loos must match heat gain/produced

• blood is used to regulate temp, blood redistributes heat via vasodilation to skin for radiation and evaporation.

• in cool temps & short duration redistribution of blood flow is good

• long duration, warm/high temp = large redis of blood flow to skin away from muscles → less o2 delivered to working muscles = cant do aerobic ATP = inc. contribution from anaerobic systems = accumulation metabolic by-products

• body sweats to thermoregulate, sweat come from blood plasma.

• lots of sweating = dec. blood plasma = inc viscosity of blood = dec. SV and inc. HR → heart pump harder to push thick blood = working hard no inc. in pace → fatigue.

• dehydration from water loss → core body temp inc → affect enzyme → slower performance

nutritional and hydration strats

enhance performance, delay fatigue, optimise recovery.

CHO LOADING prior and during

prior

preload CHO to maximise body glycogen stores.

• good for long duration events lasting 90min+

• eat complex carbs → pasta

• cho loading delays fatigue by extending steady state, using glycogen as fuel source → delaying the switch to fats (slower rate)

during

delays muscular fatigue

• muscles provided additional fuels, maintains oxidation of carb fuel stores.

• gels

muscles more responsive to insulin after activity and has highest glycogen uptake 30min. Take in cho to return to refuel muscle and liver glycogen stores.

protein and co-ingestion of cho and protein

protein → inc. rate of protein resynthesis, muscle rebuild & repair.

coingestion cho & protein

• ENHANCES uptake of glycogen at muscles, recovering faster rate, enhances proteins synthesis

coingestion cho & water

• enhance absorption rate of cho → faster restoration of muscle glycogen

hydration before, during, after

• drink water to maintain blood plasma levels

• drink water before to dec. thermoregulatory fatigue and amount of blood plasma lost

• drink after to rehydrate liquid that has been lost as sweat.