new study guide nasm domain 1

Sagittal Plane

An imaginary vertical line that divides the body into left and right halves. Movements in this plane go forward and backward — like squats, bicep curls, lunges, and running.

Frontal Plane

Divides the body into front and back halves. Movements go side to side — like lateral raises, side shuffles, and jumping jacks.

Transverse Plane

Divides the body into top and bottom halves. Movements are rotational — like a cable rotation, golf swing, or trunk twist.

Flexion

Decreasing the angle between two body segments. Example: bending your elbow (bicep curl) or bending your knee.

Extension

Increasing the angle between two body segments, straightening the joint. Example: standing up from a squat, straightening your arm.

Abduction

Moving a limb AWAY from the midline of the body. Example: raising your arm out to the side (lateral raise), or spreading your legs apart.

Adduction

Moving a limb TOWARD the midline of the body. Example: bringing your arm back down from a lateral raise, or closing your legs together.

Agonist (Prime Mover)

The muscle doing the primary work to create a movement. Example: the biceps brachii is the agonist during a bicep curl.

Antagonist

The muscle that opposes the agonist. It lengthens while the agonist contracts. Example: the triceps is the antagonist during a bicep curl.

Synergist

A muscle that assists the agonist in creating a movement. Example: the brachialis helps the biceps during a curl.

Stabilizer

A muscle that holds a body part steady while another part moves. Example: core muscles stabilize the spine during a squat.

Muscle Spindle

A sensory receptor inside the muscle that detects changes in muscle LENGTH (stretch). When stretched too quickly, it triggers a reflex contraction to protect the muscle. This is why you shouldn't bounce during a stretch.

Golgi Tendon Organ (GTO)

A sensory receptor located in the tendons (where muscle meets bone) that detects changes in muscle TENSION. When tension is too high, it causes the muscle to relax to prevent injury. This is what happens when foam rolling works — it activates the GTO to release tension.

Motor Unit

One motor neuron plus all the muscle fibers it controls. When a motor neuron fires, ALL fibers in that motor unit contract at once (all-or-nothing principle).

Type I Muscle Fibers (Slow-Twitch)

Fatigue-resistant muscle fibers that rely on the aerobic (oxidative) energy system. Best for endurance activities like long-distance running, cycling, and low-intensity, high-rep training.

Type II Muscle Fibers (Fast-Twitch)

Powerful but fatigue quickly. Used for high-intensity, short-duration activities like sprinting, heavy lifting, and plyometrics. Type IIa = moderate power, some endurance. Type IIb = maximum power, fatigues fastest.

ATP-PC System (Phosphagen System)

The immediate energy system. Uses stored ATP and phosphocreatine. Powers maximal effort activities lasting 0–10 seconds. Example: a 40-yard sprint, a max deadlift, or a shot put throw. Requires very little oxygen.

Glycolytic System (Anaerobic Glycolysis)

Breaks down carbohydrates (glucose/glycogen) for energy without oxygen. Powers activities lasting 10 seconds to 2 minutes. Example: a 400-meter run, a 2-minute workout circuit. Produces lactic acid as a byproduct.

Oxidative System (Aerobic)

Uses oxygen to produce energy from carbohydrates, fats, and protein. Powers activities lasting 2+ minutes. Example: jogging, cycling, swimming laps. Most efficient energy system — produces the most ATP total.

Macronutrients

The three main nutrient categories the body needs in large amounts: Carbohydrates (4 cal/gram — primary fuel source), Protein (4 cal/gram — muscle repair and building), Fat (9 cal/gram — hormones, vitamin absorption, long-term energy).

Basal Metabolic Rate (BMR)

The number of calories your body burns at complete rest just to stay alive (breathing, heartbeat, organ function). It does NOT include activity. Most people's BMR is 1,200–2,000 calories per day.

Central Nervous System (CNS)

The brain and spinal cord. It receives sensory information from the body, processes it, and sends out motor commands to muscles.

Peripheral Nervous System (PNS)

All the nerves outside the brain and spinal cord. Carries signals between the CNS and the rest of the body (muscles, organs, skin).

Hypertrophy

An increase in the SIZE of muscle fibers (not number). Happens when muscles are repeatedly stressed beyond their capacity. Requires adequate protein intake and progressive overload.

Pronation

Rotating the forearm so the palm faces DOWN. Also used to describe inward rolling of the foot/ankle (flat feet). Pronation distortion syndrome = feet turn out + knees cave in.

Supination

Rotating the forearm so the palm faces UP. Also describes outward rolling of the foot (high arch). Think of supination as holding a bowl of soup.