{"schemaVersion":1,"id":"en-hub-energie","type":"hub","pillar":"energy","locale":"en","translationGroupId":"hub-energie","slugPath":"energy","title":"Energy: producing and using fuel","shortTitle":"Energy","summary":"The Energy pillar answers one question: where does the energy for a muscle contraction come from? Two mechanisms and two videos describe ATP, phosphocreatine and the glycogen stored in muscle.","level":"intermediate","estimatedMinutes":4,"synonyms":["energy","ATP","phosphocreatine","glycogen","energy pathways","fuel"],"blocks":[{"id":"b1","type":"paragraph","content":[{"kind":"text","value":"The Energy pillar answers the question: where does the energy that lets a muscle contract come from?"}]},{"id":"b2","type":"paragraph","content":[{"kind":"text","value":"Every contraction consumes the same molecule, "},{"kind":"term","value":"ATP","definition":"adenosine triphosphate, the molecule cells use directly as a source of energy"},{"kind":"text","value":". The immediate ATP reserve in muscle is very small: the body rebuilds it continuously, through several routes that differ in both speed and staying power. Understanding those routes means understanding why a sprint and a long walk do not tire you in the same way."}]},{"id":"b3","type":"heading","level":2,"text":"What this pillar explains","anchor":"what-this-pillar-explains"},{"id":"b4","type":"list","ordered":false,"items":[[{"kind":"text","value":"Why ATP is the only fuel the muscle fibre can use directly."}],[{"kind":"text","value":"The role of phosphocreatine as a stopgap store for very short efforts."}],[{"kind":"text","value":"What glycogen is, where it is stored and when it becomes the dominant source."}],[{"kind":"text","value":"Why storing glycogen brings water with it, and what that changes on a scale."}],[{"kind":"text","value":"What \"running out of energy\" means at cell level, and what the phrase covers day to day."}],[{"kind":"text","value":"What becomes of the carbohydrate and the fat you eat, from the gut to the store and on to muscle."}]]},{"id":"b5","type":"heading","level":2,"text":"How to work through the pillar","anchor":"how-to-work-through-the-pillar"},{"id":"b6","type":"paragraph","content":[{"kind":"text","value":"Six written pages, two videos, one recommended reading order."}]},{"id":"b7","type":"list","ordered":true,"items":[[{"kind":"strong","value":"ATP and phosphocreatine"},{"kind":"text","value":" describes what fuels the shortest and most intense efforts."}],[{"kind":"strong","value":"The aerobic system"},{"kind":"text","value":" takes over as soon as an effort lasts, and never stops."}],[{"kind":"strong","value":"Muscle glycogen and water"},{"kind":"text","value":" describes the muscle's carbohydrate store and weight swings across a few days."}],[{"kind":"strong","value":"What happens to dietary carbohydrate"},{"kind":"text","value":" works upstream: what goes on between the plate and that store."}],[{"kind":"strong","value":"What happens to dietary fat"},{"kind":"text","value":" does the same for the second fuel, whose route and store follow different rules."}],[{"kind":"strong","value":"Fatigue"},{"kind":"text","value":" closes the pillar on what \"not being able to go on\" really covers."}]]},{"id":"b8","type":"paragraph","content":[{"kind":"text","value":"The videos animate the same mechanisms. They are there to make a cycle visible that is hard to picture from text alone, and they always point back to the matching written page, which carries the sources and the limits."}]},{"id":"b9","type":"paragraph","content":[{"kind":"text","value":"This pillar reads well straight after the "},{"kind":"link","value":"Body","href":"/en/body","external":false},{"kind":"text","value":" pillar: once a muscle has been identified, the next question is what it consumes in order to contract. It also prepares the "},{"kind":"link","value":"Recovery","href":"/en/recovery","external":false},{"kind":"text","value":" pillar, since rebuilding stores is part of returning to balance after an effort."}]},{"id":"b10","type":"callout","tone":"note","title":"Three routes, not three switches","content":[[{"kind":"text","value":"Energy pathways are often presented as systems that hand over to one another in turn. It is a convenient teaching simplification, but an inaccurate one: they all run at the same time, and what changes with the intensity and duration of the effort is their relative contribution."}],[{"kind":"text","value":"The pages in the pillar flag this kind of simplification explicitly, with the matching level of certainty."}]]},{"id":"b11","type":"heading","level":2,"text":"What this pillar does not do","anchor":"what-this-pillar-does-not-do"},{"id":"b12","type":"paragraph","content":[{"kind":"text","value":"These pages describe a general physiology. They calculate no individual requirement, recommend no carbohydrate intake and propose no eating plan. Questions of applied nutrition belong to Shapier, and medical situations — diabetes, metabolic disorders, ongoing treatment — belong to a healthcare professional."}]},{"id":"b13","type":"paragraph","content":[{"kind":"text","value":"A worrying sign during effort, such as faintness, chest pain or unusual breathlessness, warrants medical advice and is not covered anywhere on this site."}]},{"id":"b14","type":"heading","level":2,"text":"The pages in the pillar","anchor":"the-pages-in-the-pillar"},{"id":"b15","type":"shapierAction","actionId":"pathway-energy-recovery","label":"Follow the Energy and recovery pathway","description":"The pathway that organises this content on the practical side is followed in Shapier; Body Lab only explains where the energy for a contraction comes from.","webTarget":"https://shapier.app/en/parcours/energie-recuperation","appTarget":"shapier://parcours/energie-recuperation"},{"id":"b16","type":"relatedContent","title":"The whole Energy pillar","targetIds":["en-mechanism-atp-phosphocreatine","en-mechanism-aerobic-system","en-mechanism-muscle-glycogen","en-mechanism-dietary-carbohydrate","en-mechanism-dietary-fat","en-mechanism-fatigue","en-video-atp-system","en-video-glycogen-water"]}],"relations":[],"authors":["equipe-editoriale-shapier"],"reviewers":["Thanh Chau"],"references":[],"review":{"publishedAt":"2026-08-02","reviewedAt":"2026-08-02","reviewDueAt":"2027-08-02"},"limitations":["This entry page describes how the pillar is organised; the energy mechanisms, their sources and their limits are set out on the detailed pages."],"seo":{"title":"Energy — ATP, phosphocreatine and muscle glycogen","description":"The entry point to the Energy pillar of Body Lab: how muscle produces and renews its fuel, and how to work through the pages in the pillar.","canonicalPath":"/en/energy","image":"/og/en/hub-energie.png"},"app":{"offlineEligible":true},"version":1}