Athletic capacity: strength, power, endurance and sex differences
- Concept
- Exam priority: medium
Sprints run on stored phosphocreatine, middle distances on fast glycolysis, and long events on aerobic metabolism of glycogen and fat.
Also called: Energy systems in sport, Phosphagen, glycolytic and aerobic systems, VO₂max
What it is
Muscle strength depends mainly on its cross-sectional area, power on force times speed of contraction, and endurance on fuel stores, fibre type and the O₂ supply. Three energy systems resupply ATP: the phosphagen system (ATP plus phosphocreatine) gives the highest power for seconds, anaerobic glycolysis gives high power for about a minute or two, and the aerobic system gives lower power for as long as fuel lasts. On average men outperform women by about 10% in running and swimming, mainly because of testosterone-driven differences in muscle mass, hemoglobin and heart size; strength per unit of muscle area is similar.
Key facts
- Strength is the maximal force a muscle can produce; power is the rate of work (force × velocity) and peaks at intermediate loads.
- Endurance correlates with muscle glycogen: a high-carbohydrate diet before an event roughly doubles time to exhaustion compared with a high-fat diet.
- Fast (type II) fibres give power, slow (type I) fibres give endurance; the proportion is largely inherited and only partly trainable.
- Elite endurance athletes have large hearts and stroke volumes and higher capillary and mitochondrial density in muscle.
- Women have on average lower hemoglobin and smaller hearts, but similar fatigue resistance and often better fat oxidation in long events.
Typical VO₂max values in adults (wide individual variation)
| Parameter | Value |
|---|---|
| Sedentary men | ≈ 35–45 mL·kg⁻¹·min⁻¹ |
| Sedentary women | ≈ 27–38 mL·kg⁻¹·min⁻¹ |
| Elite endurance men | ≈ 70–85 mL·kg⁻¹·min⁻¹ |
| Elite endurance women | ≈ 60–75 mL·kg⁻¹·min⁻¹ |
Approximate values for a healthy adult at rest; each laboratory sets its own ranges.
Energy systems by event (dominant system; all contribute in every effort)
| Event | Duration | Dominant system | Main fuel |
|---|---|---|---|
| Shot put, jump, 100 m | < 10 s | Phosphagen | ATP and phosphocreatine |
| 200–400 m run, 100 m swim | 20–60 s | Phosphagen + anaerobic glycolysis | Muscle glycogen to lactate |
| 800–1500 m run | 2–4 min | Glycolysis + aerobic | Glycogen |
| 10 km run | 30–60 min | Aerobic | Glycogen, then fat |
| Marathon, long cycling | > 2 h | Aerobic | Fat and glycogen; glucose from the liver |
| Football, basketball | Intermittent | All three in turns | Phosphocreatine refilled aerobically between sprints |
Test yourself
Think of the answer, then tap the question to see it.
Which energy system supplies most ATP in a 100 m sprint, and why can it not last longer?
The phosphagen system: it regenerates ATP fastest but phosphocreatine stores are small and are largely used up in about 10 s.
Why does a 400 m runner feel intense muscle burning at the finish?
Anaerobic glycolysis supplies much of the ATP; lactate and H⁺ accumulate, acidifying the muscle and causing pain and fatigue.
Is a woman's muscle weaker per unit of cross-sectional area than a man's?
No. Force per cm² is similar; men are stronger on average because they have more muscle mass, driven by testosterone.
What limits pace in a marathon more than VO₂max itself?
The fraction of VO₂max that can be held without lactate accumulation (lactate threshold), running economy and glycogen stores.
Connections
Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.
Sources: Circulating Testosterone as the Hormonal Basis of Sex Differences in Athletic Performance (Endocrine Reviews (PMC), 2018); Lactate Test: MedlinePlus Medical Test (MedlinePlus, US National Library of Medicine, 2024); Benefits of Exercise: MedlinePlus (MedlinePlus, US National Library of Medicine, 2024).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.