stren&cond: chapter 3 - bioenergetics of exercise training

bioenergetics

flow of energy in a biological system

• macronutrients → usable forms of energy

metabolism

total of all catabolic/exergonic and anabolic/endergonic reactions in a biological system

• catabolic/exergonic: breakdown of reactants and produces energy + byproducts

• anabolic/endergonic: reactants consume energy to produce products

ATP

skeletal muscle ___ stores are limited

• 80-100g stored — not all used for muscle contraction

• hydrolysis: few seconds of high INT exercise

• bioenergetics = provides ___ for activity beyond what is stored in skeletal muscle

  • phosphagen system

  • glycolysis

  • oxidative system

• ATP + H2O ←ATPase→ ADP + P + H+ + energy

phosphagen

system that synthesizes ATP from creatine phosphate and ADP

• ATP for short term/ high INT activities

• active at the start of ANY exercise at ANY intensity

• ADP + creatine phosphate ←creatine kinase→ ATP + creatine

glycolysis

system that breaks down carbs to resynthesize ATP

• muscle glycogen or glucose delivered in blood

• more capacity to produce ATP but slower than phosphagen system

• end product is pyruvate

  • → lactate (fast, anaerobic)

  • → mitochondria for further oxidation (slow, aerobic)

oxidative

system that breaks down carbs and fats as substrates to generate ATP

• glycolysis → krebs cycle and ETC

• PRIMARY source of ATP at rest and low INT exercise

• greatest capacity to generate ATP for a constant supply, but is slow

law of mass action

the concentration of reactants or products in solution will shift the direction of the reactions

• two way dependent on body needs

• ADP + CP ←creatine kinase→ ATP + creatine

  • rest: ATP conc increases bc of low use and shifts left to rebuild CP/inhibit glycolysis

  • exercise: ADP increases bc of ATP demand and shifts right so CP replenishes ATP/promotes glycolysis

• elevated concentrations of ATP, CP, citrate, FFA

  • inhibit glycolysis and system has plenty of energy available

allosteric regulation

molecule binds to an enzyme at a site other than the active site, changing enzyme’s activity

• inhibition: molecule binds to enzyme → decreases enzyme activity → less product

• activation: molecule binds to enzyme → increases enzyme activity → more product

glycolytic control

high glucose 6 phosphate → inhibits hexokinase → decreases glycolysis

high AMP → activates PFK → increases glycolysis/ATP production

• high AMP = low energy

oxidative control

high ATP → inhibits isocitrate dehydrogenase → decreases oxidative energy production

high AMP → activates oxidative enzymes → increases energy production

• high AMP = low energy → make more ATP!

lactate

natural energy molecule your body makes when it breaks down carbs

glycolysis → pyruvate

• → shuttle into mitochondria to krebs cycle and ETC (slow glycolysis)

• → lactate dehydrongenase → lactate (fast glycolysis)

• higher INT = increases lactate concentration

fatigue

lactate is not a cause of _____. it is a proton consumer that decreases acidosis due to H+ accumulation

• ATP hydrolysis → accumulation of H+ → reduces pH

• inhibits glycolysis

• impairs excitation-contraction coupling

• reduces enzymatic activity

• ATP breakdown → increases interstitial Pi concentrations interfere with Ca2+ release = decrease force production

lactate clearance

often used as a substrate by type 1 and cardiac muscle fibers

1) oxidized within muscle fibers: high mitochondrial content

• lactate in glycolytic type 2 fibers → MCTs to type 1/cardiac → pyruvate → oxidation

2) cori cycle

• lactate defuses out of muscle into blood → liver → gluconeogenesis → blood glucose → resynthesize muscle glycogen

LOW INT ACTIVE RECOVERY: accelerates clearance and body relies on type 1 → more lactate taken up and oxidized

lactate threshold

how lactate accumulates with higher INT

• LT/L1: lactate rises above baseline = greater reliance on glycolytic

  • 50-60% VO2max untrained, 70-80% VO2max trained

• LT2/OBLA: lactate accumulates faster than it is cleared = predominantly anaerobic systems

• training: targeting right or just below helps athletes sustain faster paces before fatigue

energy production

faster production of ATP = lower capacity

as duration increases and intensity decreases: phosphagen (0-6s, fast production, least capacity), phosphagen and fast glycolysis, fast glycolysis, fast glycolysis and oxidative system, oxidative system (>3 min, slow production, greatest capacity)

• no system is working by itself at any point, even during rest

limiting factors

as duration increases, slow rate/high capacity systems are necessary for sustaining high INT prolonged periods

• rapid-intermediate sources contribute less to fatigue as event duration increases

o2 uptake

longer activity = lower % of max power to sustain activity

• ex: 0-5s and max power output — mostly anaerobic

• ex: 200s and low power output — mostly aerobic

• % of max power and duration of intensity = how anaerobic and aerobic contribute to energy production

EPOC

elevated O2 during recovery to replenish energy stores, clear lactate, and normalize body systems

75% VO2max abt 15 min duration:

• VO2 increases to a steady state that uses aerobic systems (oxidative phosphorylation)

80% max power output:

• VO2max is surpassed and body relies on anaerobic systems

• larger and longer EPOC: elevated O2 consumption to restore balance

phosphagen repletion

needed to replenish skeletal muscle for ATP

• CP can decrease 50-75% during the first 5-30 s of high INT exercise

• CP replenishes via oxidative and glycolytic systems

  • ATP + creatine → ADP + CP

• during recovery — 8 min for substantial repletion, but 2-5 min

  • NEED MORE REST → more CP restored → more ATP for the next effort

• O2 REQUIRED for repletion: ATP rebuilding CP uses O2 from oxidative metabolism

increase CP by

• endurance training: increase efficiency in oxidative systems

• resistance training: type 2 muscle fiber hypertrophy stores greater PC

glycogen repletion

needed to replenish stores in skeletal muscle and liver for ATP

• intensity dependent: higher INT = faster depletion

• replenish by EATING CARBS → glycogen

  • 0.7 to 3.0 g/kg bw of carbs every 2 hours depending on activity

metabolic specificity

selectively training energy systems that are is needed and used in sport/activity

• body adapts at the intensity and rest periods used

• ex: 100m sprinter — needs max power and relies on phosphagen system

• ex: marathon runner — needs endurance and relies on oxidative system

• SAID principle (specific adaptations to imposed demands): body adapts to whatever demands repeatedly placed on it

interval training

type of training that targets energy systems using predetermined work-to-rest ratios

• ex: phosphagen — 1:12 to 1:20 — short work, long rest

• ex: oxidative — 1:1 to 1:3 — longer work, less rest

HIIT

training that uses repeated bouts of high INT exercise with short recovery for quicker adaptations

• short recovery = accumulate several min at >90% VO2max, MORE REPS

  • can perform the next interval at higher INT

• high INT = pushes CV and metabolic systems

• intensity, duration, mode

  • adding on top of strength training or endurance training = increases fatigue and injury

combination training

mixes exercises/activities for a training program

• varies in exercises/modalities to improve overall fitness

• ex: 800 m runner → long, slow distance (endurance) one day, 800 m pace running another day (event-specific), strength training another day

• cross training

• concurrent training

cross training

training that uses diff exercise modes that target the same metabolic adaptation

• ex: 800 m runner does running and rowing at similar aerobic intensity

• less repetitive stress

concurrent training

training that combines aerobic and anaerobic training

• develop endurance and strength/power

• anaerobic athlete adding aerobic: can help with recovery

  • too much can interfere with max strength, power, and muscle girth

• aerobic athlete adding anaerobic: can improve endurance

  • train fast twitch fibers (hills and speed), peak running velocity, protein synthess

• ex: endurance runner adds strength training + sprint intervals