CSCS chapter 3: Bioenergetics of exercise and training

what is bioenergetics

The flow of energy in a biological system; the conversion of macronutrients into biologically usable forms of energy.

what are exergonic reaction

energy releasing reactions typically catabolic

what are endergonic reaction

reactions that require energy typically anabolic

what is metabolism

the sum of all catabolic and anabolic reactions in a system

how is ATP broken down in the body to yield energy

hydrolysis

how does hydrolysis of ATP occur

adenosine triphosphatase (ATPase) is an enzyme that catalyzes ATP

what does myosin ATPase do

catalyzes ATP hydrolysis for crissbridge recycling

what does calcium ATPase do

hydrolyzes ATP to pump calcium in the sarcoplasmic reticulum

what does sodium potassium ATPase do

maintains the sarcolemmal concentration gradient after deploarization

what is the reaction for ATP hydrolysis

ATP + H2O → ADP + Pi + Energy

what are anaerobic processes

processes not requiring oxygen

what are aerobic processes

process that rely on oxygen

what are the anaerobic mechanisms in the body

phosphagen and glycolytic systems

where do anaerobic processes occur

the sarcoplasm of a muscle cell

what are the aerobic mechanisms in the body

the krebs cycle. electron transport, and oxidative system

where do aerobic processes occur

in the mitochondria of muscle cells

what macronutrient can be metabolized for energy without oxygen

carbs

when is the phosphagen system used

short term high intensity activities

highly active at the tart of all exercise

how does the phosphagen system create energy

hydrolysis of ATP and the breakdown of creatine phosphate

how is ATP synthesized in the phosphagen system

creatine kinase catalyzes the synthesis of ATP from creatine phosphate and ADP

how does ADP and CP make ATP

the CP provides a phosphate group to ADP

why can the phosphagen system only work for a shortperiod of time

there are small amounts of stored CP in the body

is ATP stored in the body

yes but the stores cannot be completely depleted due to the need for basic cellular function

what muscle fibers have more CP

type II allowing individuals with more type II fibers to replenish ATP faster furing anaerobic exercise

what is the adenylate kinase reaction

2ADP -> ATP + AMP

adenylaekinase is the enzyme that allows this to happen

what is the adenylate kinase reaction for

it rapidly replenished ATP and is a powerful stimulant for glycolysis through AMP

what is glycolysis

the breakdown of carbohydrates either as muscle stored glycogen or glucose from the blood

why can glycolysis provide more ATP than the phosphagen system but at a slower rate

there are multiple reactions slowing the process down but there is a larger supply of glycogen and glucose compared to CP

what occurs to pyruvate at the end of glycolysis

it can be converted to lactate in the sarcoplasm or it can be shuttled into the mtochondria

what occurs of pyruvate is converted to lactate

ATP resynthesis occurs faster due to the rapid regeneration of NAD+ but duration is limited due to excess H+ production due to the breakdown of ATP

what is anaerobic glycolysis

the conversion of pyruvate to lactate

what occurs to pyruvate if it is shuttled into the mitochondria

it undergoes the krebs cycle which is slower at resynthesizing ATP due to numerous reactions but can occur for a longer duration

what is aerobic glycolysis

pyruvate is shuttled into the mitochondria to undergo the krebs cycle

what occurs with glycolysis at higher exercise intensities

pyruvate and NADH increase and can't be broken down leading to conversion to lactate and NAD+

how is pyruvate converted to lactate

lactate dehydrogenase

what leads to muscular fatigue during exercise

H+ accumulation decreases the pH which inhibits glycolytic reactions, inhibits calcium binding to troponin, and interferes with crossbridge recycling

what is metabolic acidosis

a decrease in pH leading to peripheral fatigue

how is lactate used for energy

it is used for type I or cardiac muscle fibers

it is also used in gluconeogenesis to form glucose

what muscle fibers have more lactate during exercise

Type II fibers likely due to more activity of glycolytic enzymes than type I

how is lactate cleared from blood

bicarbonate buffers it

how does bicarbonate buffer the blood

it accepts H+ becoming carbonic acid then dissociates into H2O and CO2 in the lungs

how can lactate be cleared from muscle

by oxidation

where does gluconeogenesis occur

in the liver

how long does it take blood lactate levels to normalize after exercise

within an hour

what can improve lactate clearance

light activity during the postexercise period

what individuals clear lactate better

athletes

what occurs to pyruvate as it enters the mitochondria with 2 NADH

it is converted to acetyl CoA resulting in carbon loss as CO2

what occurs to acetyl CoA after it is formed

it enters the krebs cycle for ATP resynthesis

what occurs to NADH in the krebs cycle

it drops H+ at the electron transport chain for ATP

what is oxidative phosphorylation

resynthesis of ATP in the ETC by adding P to another molecule

what is substate level phosphorylation

direct resynthesis of ATP from ADP during a single reaction in metabolic pathways

how many ATP molecules are resynthesized in substrate level phosphorylation

4

what is required as glucose is stored in muscle

it needs to be phosphorylated to stay in the cell requiring hydrolysis of one ATP

what occurs as muscle glycogen is broken down

an enzyme breaks it down through glycogenolysis not requiring ATP

how much ATP is made from glycolysis with blood glucose

2 ATP as 2 ATP molecules are used and 4 are resynthesized

how much ATP is made from glycolysis from muscle glycogen

3 ATP as 1 ATP is used and 4 are resynthesized

what is the lactate threshold

the exercise intensity at which blood lactate begins an abrupt increase above baseline concentration

what does the lactate threshold indicate

increased reliance on the glycolytic pathway for energy demand often sued as the marker of anaerobic threshold

what is the lactate threshold 2

the onset of blood lactate accumulation when there is a second exponential increased in the rate of lactate accumulation

what does the oxidative system use for energy

carbohydrates and fats

how much fat and carbs are used for energy at rest

70% from fats, 30% from carbs

what occurs to the use of fats and carbs for ATP as exercise increases

the body starts using more carbohydrates than fats

what occurs with carbs and fats with prolonged submaxial steady state cardio

there is a gradual shift from carbohydrate use to fats due to glycogen depletion

how much ATP does krebs cycle produce

2 ATP

how much ATP does NADH produce in the ETC

3 ATP

how much ATP does FADH2 produce in the ETC

2 ATP

how much ATP does oxidative phosphorylation produce

32 ATP from one molecule of blood glucose

24 ATP from one molecule of muscle glycogen

how are triglycerides broken down for energy from fats

they are broken down by lipase to produce free fatty acids and glycerol allowing some of the free fatty acids to go into the blood and enter muscle fibers for oxidation

what occurs as free fatty acids enter the mitochondria

they undergo beta oxidation where they are broken down and formed into acetyl CoA entering krebs cycle and ETC

what substrate depletion often results in the msot fatigue

phosphagens and glycogen

how fast does phosphagen replenish after exercise

complete ATP resynthesis within 3-5 min and CP resynthesis in 8 min with over half replenished in 30 sec to allow repeated max contractions

when is muscle glyogen mostly used

during moderate to high intensity exercise

when is liver glycogen mostly used

during low intensity exercise

what occurs to blood glucose with exercise

it decreases

what replenishes muscle glycogen after exercuse

postexercise carbohydrate intake (.7-3.0 g per kg of BW every 2 hours after exercise)

what occurs with oxygen uptake with low intensity exercise

it increased for the first few minutes until a steady state is reached

what is the oxygen deficit in oxygen uptake

there is a anaerobic contribution to energy at the start of exercise

what is EPOC

excess postexercise oxygen consumption where oxygen uptake remains elevated after exercise to restore homeostasis

what intensity should HIIT training be performed

above 90% VO2max

what is combination training

any training program including a mix of different types of exercises and activities

what is cross training

incorporating different types of exercise with the same metabolic adaptation profile without overstressing the primary activity muscles

what is concurrent training

the simultaneous training of anaerobic resistance training with aerobic endurance training at multiple times within the same training session or day