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NASM Certified Personal Trainer · Basic and Applied Sciences and Nutritional Concepts

NASM Certified Personal Trainer: Exercise Physiology and Energy Systems Concepts

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Written by AI. Only units that passed a separate AI check (re-reading facts and numbers) are published. Tell us if you find a mistake.

Overview

This chapter covers how the body makes energy and how the heart, lungs, and muscles respond to exercise. The exam asks which energy system fuels an activity, how muscle fiber types differ, and how training changes the heart.

The body has three energy systems. The ATP-PC system fuels very short, all-out efforts of about 10 seconds or less, such as a sprint start or a heavy lift. Glycolysis covers hard efforts lasting from a few seconds up to about two minutes. The oxidative system uses oxygen and fuels longer, steady activity.

Muscles have two main fiber types. Type I fibers are slow-twitch, resist fatigue, and suit endurance work. Type II fibers are fast-twitch, produce more force, and tire faster.

Cardiac output is the amount of blood the heart pumps each minute, found by multiplying heart rate by stroke volume. With regular aerobic training, the heart pumps more blood with each beat, so resting heart rate goes down.

Key concepts

  • ATP-PC system

    The fastest energy system. It fuels very short, maximal efforts of about 10 seconds or less, such as a sprint start or a one-rep lift, without needing oxygen.

    Memory tipATP-PC = Power for a Couple of seconds.

  • Glycolysis

    An energy system that breaks down carbohydrate without needing oxygen. It fuels hard efforts lasting from a few seconds up to about two minutes.

    Memory tipGlyco = sugar. Hard and medium-short efforts.

  • Oxidative system

    The energy system that uses oxygen. It is slower to produce energy but can keep going for a long time, fueling walking, jogging, and other steady activity.

    Memory tipOxidative = oxygen = long and steady.

  • Type I vs. Type II fibers

    Type I (slow-twitch) fibers resist fatigue and suit endurance. Type II (fast-twitch) fibers produce more force and speed but tire faster.

    Memory tipType I = 1 long marathon. Type II = 2 quick, strong bursts.

  • Cardiac output

    How much blood the heart pumps per minute. Cardiac output = heart rate x stroke volume. Stroke volume is the blood pumped with each beat.

    Memory tipBeats per minute times blood per beat.

  • Training effect on resting heart rate

    Regular aerobic training makes the heart stronger, so it pumps more blood with each beat and resting heart rate goes down.

    Memory tipBigger beat, fewer beats.

Often tested

  • A short all-out effort uses the ATP-PC system; long steady work uses the oxidative system.
  • Type I fibers resist fatigue; Type II fibers make more force.
  • Cardiac output is heart rate times stroke volume.
  • Aerobic training lowers resting heart rate, not raises it.

Easy to confuse: Energy systems

SystemNeeds oxygen?Typical activity
ATP-PCNoAll-out effort, about 10 seconds or less
GlycolysisNoHard effort, up to about 2 minutes
OxidativeYesLong, steady activity like walking or jogging

3 sample questions

Verified practice questions from this unit.

Practice questionReviewedBasic and Applied Sciences and Nutritional Concepts › Exercise Physiology and Energy Systems★★★★☆

Question 1. Which energy system fuels very short, high-effort actions of about 10 seconds or less?

  1. ① Aerobic system
  2. ② Glycolytic system
  3. ③ Fat oxidation only
  4. ④ ATP-PC system
▼ Show answer and explanation▲ Hide answer and explanation

Answer: ④ ATP-PC system

Key point: ATP-PC = very short, maximal efforts

The ATP-PC system supplies energy fast for efforts like a heavy lift or a short sprint.

Wrong choices

  • Aerobic system: This works for long, low-intensity activity.
  • Glycolytic system: This fuels efforts lasting longer than a few seconds.
  • Fat oxidation only: Fat supplies energy slowly.
Practice questionReviewedBasic and Applied Sciences and Nutritional Concepts › Exercise Physiology and Energy Systems★★★★☆

Question 2. Which muscle fiber type is the most fatigue resistant and used mainly for endurance?

  1. ① Type IIx
  2. ② Type IIa
  3. ③ Smooth muscle
  4. ④ Type I
▼ Show answer and explanation▲ Hide answer and explanation

Answer: ④ Type I

Key point: Type I = slow twitch, endurance

Type I fibers are slow twitch. They resist fatigue and are used for long, low-intensity work.

Wrong choices

  • Type IIx: These fibers make high force and tire quickly.
  • Type IIa: These are in between, but less resistant than type I.
  • Smooth muscle: This is not a skeletal muscle fiber type.
Practice questionReviewedBasic and Applied Sciences and Nutritional Concepts › Exercise Physiology and Energy Systems★★★★☆

Question 3. How is cardiac output calculated?

  1. ① Heart rate + stroke volume
  2. ② Stroke volume / heart rate
  3. ③ Blood pressure x heart rate
  4. ④ Heart rate x stroke volume
▼ Show answer and explanation▲ Hide answer and explanation

Answer: ④ Heart rate x stroke volume

Key point: Cardiac output = HR x stroke volume

Cardiac output is the amount of blood the heart pumps per minute. It equals heart rate times stroke volume.

Wrong choices

  • Heart rate + stroke volume: The two values are multiplied, not added.
  • Stroke volume / heart rate: This is not the formula.
  • Blood pressure x heart rate: This is not the formula.
Practice 5 questions from this unit →