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CSCS Exercise physiology: key points

Energy systems, muscle fiber types, and training adaptations form the foundation of the CSCS exam. Make sure you can match exercise duration to the dominant energy system and explain what drives early strength gains.

Points that often appear

Organize energy systems by duration

Maximal efforts of a few seconds up to about 10 seconds rely on the phosphagen system (ATP and creatine phosphate), about 30 seconds to 2 minutes on fast glycolysis, and beyond 3 minutes on the oxidative system. Expect questions on transition periods where systems overlap.

Type I vs Type II fibers

Type I (slow-twitch) fibers have high oxidative capacity, many capillaries and mitochondria, and resist fatigue. Type II (fast-twitch) fibers produce more force and contract faster but fatigue quickly.

Early strength gains are neural

Strength gains in roughly the first 6–8 weeks come mainly from neural adaptations such as better motor unit recruitment and firing rate. Hypertrophy contributes more later.

Anabolic vs catabolic hormones

Testosterone, growth hormone, and IGF-1 are anabolic and promote muscle protein synthesis. Cortisol is catabolic and promotes protein breakdown.

Key cardiovascular formula and responses

Cardiac output = heart rate × stroke volume. During aerobic exercise systolic pressure rises while diastolic stays about the same or drops slightly. Endurance training increases stroke volume and lowers resting heart rate.

Stimulus for bone

The minimum stimulus that triggers bone formation is the minimal essential strain (MES). The principle that bone adapts to the loads placed on it is Wolff's law.

Quick reference

Approximate duration	Primary energy system
0–6 s	Phosphagen
6–30 s	Phosphagen + fast glycolysis
30 s–2 min	Fast glycolysis
2–3 min	Fast glycolysis + oxidative
Over 3 min	Oxidative

Watch for this trap

Distractors often reverse a fact, such as "resting heart rate increases" or "Type I fibers fatigue quickly." Learning the direction of each adaptation (up or down) makes these easy to spot.