Part 1: Foundations of Strength & Conditioning Chapter 3: Anatomy, Muscle Physiology & Energy Systems

Muscle

Entire muscle groups

Ex. Quadriceps

Fascicle

Bundle of muscle fibers

Muscle fiber

Individual cell that contracts

Myofibril

Thread-like strand inside each fiber

Sarcomere

Smallest functional unit of muscle

Actin

Thin filament

Myosin

Thick filament

The sliding filament theory

Explains how muscles contract to produce force and movement. It describes the interaction between two main protein filaments inside muscle fibers — actin and myosin — and how they slide past each other to shorten (contract) the muscle.

Type 1

Slow speed, high fatigue resistant fiber (slow twitch)

Ex. Marathon running, posture

Type 2a

Moderate speed, medium fatigue resistant fiber (fast oxidation)

Ex. 400m sprint

Type 2x

Very fast speed, low fatigue resistant fiber (fast glycolytic)

Ex. Max Lifts, Sprints

Neural adaptations

Increased motor unit recruitment

Improved rate coding

Better synchronization

Reduced inhibition (less safety breaks)

Concentric

Muscle shortens while producing force

Ex. Lifting phase of a bicep curl

Isometric

Muscle produces force without changing length

Ex. Holding a plank

Eccentric

Muscle lengthens under tension (creates most stretch)

Ex. Lowering bar in a squat

ATP-PC 

Energy system that provides immediate energy for high intensity, short duration activities, using stored Adenosine Triphosphate and Phosphocreatine

Ex. Sprint Start, 1RM Lift

Glycolytic

Energy system is a crucial metabolic pathway that breaks down glucose to produce ATP, primarily during moderate to high intensity activities lasting from around 10s-2min

Ex. 400m Run, Circuit Training

Oxidative

Primary method the body uses to creatine energy (ATP) during low intensity, long duration activities 

Ex. Jogging, Cycling, Endurance Sports

Strength/Power

Increased phosphagen storage-more explosive output

Anaerobic Conditioning

Improved glycolytic enzymes-higher lactate threshold

Aerobic Training

Increased mitochondria & capillaries-greater endurance & recovery

Testosterone

Hormone increases protein synthesis, muscle growth

• Released by Gonads

Growth Hormone

Hormone helps tissue repair & fat metabolism

• Released by Pituitary gland

Cortisol

Stress hormone

• Released by Adrenal gland

Epinephrine/Norepinephrine

Hormones increase heart rate & energy mobilization

• Released by Adrenal medulla