{"schemaVersion":1,"id":"en-video-protein-synthesis","type":"video","pillar":"adaptation","locale":"en","translationGroupId":"video-protein-synthesis","slugPath":"videos/protein-synthesis-visualised","title":"Protein synthesis visualised — the video","shortTitle":"Protein synthesis","summary":"An animation that shows muscle as a permanent building site: proteins are broken down while others are assembled, and it is the difference between the two, repeated day after day, that decides whether the fibre gets bigger.","level":"intermediate","estimatedMinutes":8,"synonyms":["protein synthesis","muscle proteins","amino acids","leucine","protein balance"],"blocks":[{"id":"b1","type":"paragraph","content":[{"kind":"text","value":"A muscle is not a fixed structure that training simply thickens. It is a permanent building site, where proteins are dismantled while others are put together. The video shows that back-and-forth and what tips it one way."}]},{"id":"b2","type":"videoLesson","videoId":"synthese-proteique-video","title":"Protein synthesis visualised"},{"id":"b3","type":"heading","level":2,"text":"What the video shows","anchor":"what-the-video-shows"},{"id":"b4","type":"paragraph","content":[{"kind":"text","value":"The animation opens on a muscle fibre seen from the inside, with two flows drawn side by side. On the left, worn contractile proteins are broken down into amino acids: this is breakdown. On the right, amino acids are assembled into new proteins: this is "},{"kind":"term","value":"muscle protein synthesis","definition":"the assembly of new proteins inside the muscle fibre, from the amino acids available"},{"kind":"text","value":". Both flows run continuously, even at rest."}]},{"id":"b5","type":"paragraph","content":[{"kind":"text","value":"A pair of scales then appears in the middle of the frame. As long as the two flows balance out, the fibre keeps the same size. That is the main message of the video: growth does not come from breakdown stopping, but from a repeated imbalance in favour of building."}]},{"id":"b6","type":"paragraph","content":[{"kind":"text","value":"Two events then tip the scales. A meal containing protein sends a wave of amino acids into the cell, and the building flow speeds up noticeably. The video then shows the effect of a resistance session: the same wave of amino acids produces a stronger, longer-lasting response when the muscle has just been worked."}]},{"id":"b7","type":"paragraph","content":[{"kind":"text","value":"The closing shot widens the time scale. Peaks of building follow one another over several days, and the animation traces the curve of the fibre's size: it does not rise at every peak, it rises by accumulation."}]},{"id":"b8","type":"timeline","title":"The sequence of events shown in the video","steps":[{"id":"t0","label":"Rest, fasted","timing":"Baseline state","description":"Building and breakdown both tick over slowly and roughly balance each other."},{"id":"t1","label":"After protein is taken in","timing":"Short response","description":"Amino acids flood in, building speeds up, then returns towards baseline even while amino acids remain available."},{"id":"t2","label":"After a resistance session","timing":"Extended response","description":"The muscle that has been worked responds more strongly to the same intake, and for longer than a meal on its own."},{"id":"t3","label":"Across several days","timing":"Accumulation","description":"The sum of successive imbalances, rather than any single peak, shows up as a change in the size of the fibre."}]},{"id":"b9","type":"heading","level":2,"text":"A short response, not a switch","anchor":"a-short-response-not-a-switch"},{"id":"b10","type":"paragraph","content":[{"kind":"text","value":"The least intuitive sequence in the video is the return to baseline: the building flow drops back while amino acids are still present. The cell does not keep building indefinitely just because it is being supplied."}]},{"id":"b11","type":"evidence","level":"established","statement":"Muscle protein synthesis rises briefly after amino acids are taken in, then falls back even when amino acid availability is maintained.","detail":"Reviews of how muscle responds to nutrition and exercise describe a short-lived rise after protein is eaten, followed by a return towards baseline, and a larger, longer response when the intake follows a bout of resistance exercise. Those measurements rest on isotope tracers used over a few hours, in small groups of healthy adults: they illuminate the mechanism without predicting the outcome of a whole programme.","referenceIds":["atherton2012"]},{"id":"b12","type":"heading","level":2,"text":"From a one-off response to a visible result","anchor":"from-a-one-off-response-to-a-visible-result"},{"id":"b13","type":"paragraph","content":[{"kind":"text","value":"A rise measured in a laboratory is not a gain in muscle. What links the two is repetition, and conditions where intake is sufficient."}]},{"id":"b14","type":"evidence","level":"probable","statement":"Sufficient protein intake, combined with repeated resistance training, is associated with larger gains in muscle mass.","detail":"A meta-analysis carried out in healthy adults reports a favourable effect of additional protein intake on the mass and strength gained through resistance training, with an effect that stops rising beyond roughly 1.6 grams of protein per kilogram of body weight per day. Reviews on hypertrophy point out that food intake does not replace the mechanical stimulus. Those results are group averages and are not a personal instruction.","referenceIds":["morton2018","schoenfeld2010"]},{"id":"b15","type":"heading","level":2,"text":"The linked scene","anchor":"the-linked-scene"},{"id":"b16","type":"scene3d","sceneId":"synthese-proteique","title":"Protein synthesis simplified","intro":"The scene takes the two flows from the video — breakdown and building — and lets you explore them step by step, at rest and then after protein is taken in. Every step is described in text below the scene and stays understandable without displaying the model.","accessibility":{"textAlternative":"Flow diagram read from left to right. On the left, a dozen scattered small dark spheres stand for the available amino acids; a short arrow leads them toward the centre. In the middle, two stacked rounded volumes — the two subunits of the ribosome — receive a slanted arrow from above representing the signal left by training. To their right, nine terracotta spheres strung along a curve that rises and then falls form the growing peptide chain, each sphere a link added after the previous one. At the far right, an arrow leads to a pale capsule, the muscle fibre, in which three parallel terracotta filaments represent the contractile protein once it is built in. Proportions and counts are symbolic: the diagram deliberately merges several molecular steps.","structures":[{"label":"Amino acids","description":"Amino acids are the building blocks of proteins. They come from food and from the constant recycling of the body's own proteins; without them available, nothing can be assembled.","href":"/en/adaptations/muscle-protein-synthesis"},{"label":"Ribosome","description":"The ribosome is the cell's assembly machine. Made of two subunits, it reads a message and joins amino acids to one another in the order it specifies.","href":"/en/adaptations/muscle-protein-synthesis"},{"label":"Peptide chain","description":"Amino acids joined end to end form a chain that grows one link at a time. The chain then folds to become a working protein.","href":"/en/adaptations/muscle-protein-synthesis"},{"label":"Contractile protein","description":"Once folded, the protein is built into the filaments that produce force. It is this incorporation, repeated over and over, that gradually changes the structure of the fibre.","href":"/en/adaptations/how-muscle-grows"},{"label":"Training signal","description":"Training temporarily raises the rate of synthesis. It supplies no material: it acts as an instruction sent to the assembly machine.","href":"/en/adaptations/how-muscle-grows"}],"steps":[{"id":"signal","title":"1. The training signal","body":"The arrow coming down from the left stands for the signal left by the session. It supplies no raw material: it temporarily raises the rate at which the fibre assembles proteins."},{"id":"acides-amines","title":"2. The available amino acids","body":"On the left, the cluster of small spheres stands for the amino acids circulating in the cell. They are the building blocks: the signal is useless if they are missing."},{"id":"ribosome","title":"3. The ribosome assembles","body":"The ribosome, drawn as two stacked volumes, reads a message and joins the amino acids in exactly the order it specifies. This is where material and information meet."},{"id":"chaine","title":"4. The chain grows","body":"The links appear one after another along the curve: the growing peptide chain. It will then fold on itself to become a working protein."},{"id":"integration","title":"5. The protein joins the fibre","body":"On the right, the finished protein is built into the contractile filaments of the fibre. Repeated relentlessly, this incorporation is what eventually changes the structure of the muscle."}],"license":"Shapier — Propriétaire — usage interne ShapierLab"}},{"id":"b17","type":"callout","tone":"limit","title":"What the video simplifies","content":[[{"kind":"text","value":"Amino acids are drawn as identical, interchangeable bricks; in reality their roles differ, and some of them act as signals as well."}],[{"kind":"text","value":"The animation leaves out the signalling pathways named in the literature, the turnover of the other proteins in the cell, and the exchanges with the rest of the body."}]]},{"id":"b18","type":"sourceList","title":"Sources for this video","referenceIds":["atherton2012","morton2018","schoenfeld2010"]},{"id":"b19","type":"relatedContent","title":"Read next","targetIds":["en-mechanism-muscle-protein-synthesis","en-mechanism-how-muscle-grows","en-pathway-muscle-growth-path"]},{"id":"b20","type":"shapierAction","actionId":"nutrition-protein","label":"Read the guide on everyday protein intake","description":"Find in Shapier the guide that follows protein intake across training days.","webTarget":"https://shapier.app/en/dossiers/proteines-au-quotidien","appTarget":"shapier://dossiers/proteines-au-quotidien"}],"relations":[{"type":"explains","targetId":"en-mechanism-muscle-protein-synthesis"},{"type":"next-step","targetId":"en-mechanism-how-muscle-grows"},{"type":"shapier-action","targetId":"nutrition-protein"}],"authors":["equipe-editoriale-shapier"],"reviewers":["Thanh Chau"],"references":[{"id":"atherton2012","authors":"Atherton PJ, Smith K","year":2012,"title":"Muscle protein synthesis in response to nutrition and exercise","source":"The Journal of Physiology","kind":"review","doi":"10.1113/jphysiol.2011.225003"},{"id":"morton2018","authors":"Morton RW, Murphy KT, McKellar SR, Schoenfeld BJ, Henselmans M, Helms E, Aragon AA, Devries MC, Banfield L, Krieger JW, Phillips SM","year":2018,"title":"A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults","source":"British Journal of Sports Medicine","kind":"meta-analysis","doi":"10.1136/bjsports-2017-097608"},{"id":"schoenfeld2010","authors":"Schoenfeld BJ","year":2010,"title":"The mechanisms of muscle hypertrophy and their application to resistance training","source":"Journal of Strength and Conditioning Research","kind":"review","doi":"10.1519/jsc.0b013e3181e840f3"}],"review":{"publishedAt":"2026-08-02","reviewedAt":"2026-08-02","reviewDueAt":"2027-08-02","evidenceLevel":"established"},"limitations":["Protein synthesis is measured with isotope tracer methods covering a few hours: they describe a one-off response, not directly the result of several months of training.","The work cited mostly involves small samples of healthy adults studied in a laboratory; the values vary with age, training level and nutritional state.","The animation shows a single fibre: it leaves out the differences between fibre types and the other tissues renewing themselves at the same time."],"seo":{"title":"Protein synthesis visualised — building and breaking down","description":"Video and text explanation of muscle protein synthesis: the balance between building and breakdown, the effect of a meal and of a session, and measurement limits.","canonicalPath":"/en/videos/protein-synthesis-visualised","image":"/og/en/video-protein-synthesis.png"},"app":{"offlineEligible":true},"version":1}