Muscle Physiology and Energy Systems

Flashcards covering key vocabulary and definitions related to muscle physiology, contraction types, energy systems, and additional terms.

Actin and Myosin

Proteins in muscle fibers that interact to contract the muscle when energized by ATP.

Sarcomere

The functional unit of muscle contraction, a repeating unit within muscle fibers that contains actin and myosin filaments.

Isometric Contraction

muscle does not change length but is active, creating tension without movement

• sarcomeres do not shorten fully

• wall sits

Isotonic Contraction

muscle changes in length while generating force

Concentric Contraction

muscle shortens as it generates force

• sarcomere contracts and gets shorter in length 

• standing up from a deadlift or pushups 

Eccentric Contraction

muscle lengthens while maintaining tension

• sarcomere gets longer

• standing to air squat

Isometric Training

Exercise type where muscles contract without changing length, effective for strength and stability

• strengthens muscles, enhances muscular endurance 

• good for injuries or limitations

• utilized if there are ROM issues

• used for warm up muscles

eccentric training

• generates more force than concentric training

• builds muscle strength and hypertrophy

• can increase ROM, tendon strength and break up training plateaus

Delayed Onset Muscle Soreness (DOMS)

Muscle pain and stiffness that occurs after exercise due to microscopic damage to muscle fibers

• also caused by inflammation and repair process the body initiates to heal damaged fibers

Motor Unit

A motor neuron and all the muscle fibers it innervates; varies in size according to the muscle's functio

• large muscles have many motor units

motor unit= 

motor neurons + motor fibers

upper motor neuron

starts in brain, fires and causes muscle fibers to contract

lower motor neurons

connects to muscle and contracts after gettng UMN signals

Motor unit recruitments

• type 1, slow twitch activated before the type 2 fast twitch

Action potential

electrical impulse transmitted through a neuron to activate some contraction

Henneman Size Principle

The recruitment of motor units in order of size, starting with smaller slow-twitch fibers before larger fast-twitch fibers.

Henneman size principle characteristics

• small amounts of force is required for muscle with a mix of motor unit types

• the lower reps in reserve, the harder you are working, which more motor units are required

Tricarboxylic Acid (TCA) Cycle

A metabolic pathway essential for oxidative energy production, generating NADH and FADH2 for ATP production

• activity increases during exercise

type 1 (slow oxidative)

• aerobic, slow, high fatigue, function is endurance and posture 

• slow contraction speed and uses oxygen

type 2 (intermediate/fast aerobic)

• aerobic, fast, high fatigue, moderate intensity and duration

• fast contraction speed, oxidative and glycoltic, immediate fatigue resistance

• speed and endurance

• swimming, cycling

type 3 (fast anaerobic)

• anaerobic, fast, low fatigue

• very fast contraction speed, uses glycogen, highly fatiguable

• primarily used for short bursts of high intensity activities

• sprinting

Energy Systems

Mechanisms through which the body produces ATP, including ATP/PCr, glycolysis, and aerobic metabolism.

ATP/PCr

• fastest way for muscles to produce energy by using stored ATP and PCr

• provides immediate, high intensity energy for first 5-10 seconds

• quick, explosive action, short burst

• fuel source is creatine phosphate

• short power based activities 

glycolysis

• breakdown of glucose into pyruvate to generate ATP for muscle contraction

• muscles rely on this to produce ATP quickly 

• primary energy supplier ofr intense exercise

glucaneogenesis

formation of glucose

• transforms non carbohydrate substances such as lactate, amino acids and glycerol into glucose

• the raw material used in anaerobic glycolysis energy production

  • this is how we store glucose for long period of time

glycogen

• a macromolecule of many glucose molecules

• we store carbohydrate energy as glycogen and then fat

• glycogen housed mostly in the muscles and liver 

• relatively short term store of carbohydrate

carbohydrate utilization

the amount of carbohydrate use is dependent on intensity

• high intensity means high speed glycolysis

• fatigue occurs as glycogen stores depleted

glycogen storage

• muscles, 500g

• liver, 100g

• fluid, 15g

• 75-80% stored in muscles

liver glycogen

• stored int he liver, broken down and transported to muscles

• glycogen to glucose then exported into blood to tissues

NADH

• carrier molecule

• glucose to pyruvate to NADH 

• it carries electrons and protons

Aerobic Glycolysis

The process of producing ATP in the presence of oxygen, generating more energy compared to anaerobic glycolysis.

• cytoplasm and mitochondria

• pyruvate oxidized into acetyl coa entering kerebs cycle

• brisk walking, jogging and cycling

Anaerobic Glycolysis

The breakdown of glucose without oxygen, producing energy quickly but less efficiently.

• in the cytoplasm

• pyruvate into lactate

• less efficient 

• sprinting, weightlifting, and HIIT workouts 

Creatine

A naturally occurring compound that assists in regenerating ATP from ADP during short bursts of high-intensity activities.

• do not take if you have kidney complications

• acts as a reservoir of energy

creatine and ATP

ATP is used during muscle contractions, creatine phosphate donates a phosphate group to ADP to regenerate ATP

glycolysis and fate of pyruvate

• without oxygen (anaerobic), pyruvate into lactate

  • at high intensities when glycolysis is running fast

  • pH changes

• with oxygen (aerobic) pyruvate into acetyl coa, producing ATP

oxidative capacity (vo2)

the volume of oxygen transported, delivered and consumed to the working muscle

vo2 flick equation

vo2= HR MAX * SV MAX

• used ot calculate cardiac output, which is the volume of blood pumped by the heart per minute

SV stroke volume

largest volume of blood your heart can pump with a single beat during maximal exercise 

frank starling law

SV increases due to increase in L vent contraction force, caused ny increases in blood return from the heart 

• the force of the heart contraction increases as volume of blood in ventricle increases 

density of cappilaries

• takes oxygen to tissue

• more dense, we can deliver more efficiently and extract by products faster

• high power athletes increase density of capillaries 

density of mitochondria

more mitochondria= more ATP

• low, moderate endurance training improves capacity for oxidation

• HIIT improves global respiratory capacity 

• reccomendation is to alter intensity and duration in program for maximal mitochondrial function

left ventricular hypertrophy

• athletic training is associated with increases in cardiac dimenstions

• adaptation that facilitates the generation of a large and sustained cardiac output and enhave the extraction of oxygen from exercise muscle

  • cardiac output (CO) = HR * SV

enzymes

training can increase volume and activity of enxymes 

• endurance exercise increase TCA cycle enzymes

endurance

myocardial growth and chamber enlargement

strength

mostly myocardial growth

Lactate Threshold

• increased lactate, increased oxygen consumption because of increased exercise intensity

• the more fit you are, the higher intensity you can exercise, so longer the lactate increase will be 

pH in the sarcoplasms

• pyruvate when glyoclysis in anaerobic is fast and turned into lactate, which is made into new glucose and stored as glycogen and can be used in heart

• pyruvate when glycolysis is aerobic, it breaks down the sugar into acetyl coa and to the mitochondria where there is oxidative ability 

what metabolic process forms pyruvate

anaerobic glycolysis and aerobic glycolysis, depending on energy demand

where in the cell is pyruvate formed

cytosol

Triglycerides

A stored form of fat that serves as a primary energy source during rest and low-intensity exercise.

• also can be used to make lipids

Beta Oxidation

The metabolic process of breaking down fatty acids to produce Acetyl CoA.

acetyl coa in 2 diff ways

• pyruvate (slow) glycolysis, glucose to pyruvate

• b oxidation from fatty acids and triglycerices 

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