Physiological Factors

Two athletes can follow the same training programme and end up with very different levels of fitness. Much of that difference comes down to physiological factors — the internal, body-level systems that determine how much strength, endurance, speed, and flexibility a person is capable of developing. Physical Education studies three physiological factors as the foundation of physical fitness.

The Skeletal Muscle Factor

Muscle is made of two broad fibre types. Type I (slow-twitch, slow oxidative) fibres are rich in capillaries, myoglobin, and mitochondrial enzymes, giving them a red colour. They work aerobically, resist fatigue, and favour long-duration activities like distance running, swimming, and cycling. Type II (fast-twitch, fast glycolytic) fibres have fewer mitochondria, are lighter in colour, work anaerobically, and fatigue quickly — they favour short, explosive efforts like jumps, throws, and sprints. The proportion of each fibre type a person has (partly genetic) shapes which fitness components come more naturally to them: long-distance runners typically carry 70–80% slow-twitch fibres, sprinters 70–75% fast-twitch, while non-athletes sit closer to an even split.

The Energy Production Factor

Every movement needs energy, and the body produces it through metabolism — anabolism (using energy to build tissue) and catabolism (breaking down fuel stores to release energy). Three energy systems supply this, matched to how long an effort lasts: the ATP-CP (phosphagen) system for activities under 10 seconds, such as a sprint start or a weightlifting attempt; the anaerobic system for efforts under about 2 minutes, such as a 400m race; and the aerobic system for longer-duration activities such as football or a marathon, where oxygen is used continuously to release energy.

The Cardiorespiratory Factor …