Muscle mass and ageing: sarcopenia, protein, the training minimum and creatine

What happens to muscle after thirty

Muscle mass peaks in the late twenties or early thirties and then declines by roughly 3–8% per decade, accelerating after sixty to something closer to 1–2% a year. Strength falls faster than mass, because the fast-twitch fibres that produce force are the ones lost first and the motor neurons that drive them die off. By seventy, a sedentary adult has lost a quarter to a third of the muscle they had at thirty and considerably more of the power.

When the loss crosses a clinical threshold it is called sarcopenia: low muscle strength, confirmed by low muscle quantity, with or without poor physical performance (the EWGSOP2 definition, 2019). It affects around 10% of adults over sixty and most people over eighty, and it is the common pathway to the fall, the fracture, the hospital stay and the loss of independence that ends healthspan. The usual cut-offs are grip strength under 27 kg in men and 16 kg in women, and appendicular lean mass index under 7.0 and 5.5 kg/m² respectively on DEXA.

Why it matters for how long you live

The strongest evidence is for strength rather than size. In the PURE study (Leong et al. 2015, Lancet), 139,691 adults in 17 countries had their grip measured and were followed for four years: each 5 kg lower grip was associated with a 16% higher risk of death from any cause, 17% higher cardiovascular mortality and higher rates of stroke and heart attack — and grip was a better predictor of mortality than systolic blood pressure. A 2018 UK Biobank analysis of half a million people found the same gradient across every cause of death, including cancer.

Muscle mass matters through different routes. Skeletal muscle disposes of about 80% of the glucose from a meal, so losing it is one of the mechanisms behind insulin resistance after fifty. It is the body's amino-acid reserve during illness — a hospital stay burns it fast, and people who go in with more come out better. And it is the only tissue that gets you off the floor.

Protein: how much and when

The recommended dietary allowance of 0.8 g per kilogram per day was set to prevent deficiency in sedentary adults, not to maintain muscle in people who train or age. The best synthesis is the Morton 2018 meta-analysis in the British Journal of Sports Medicine: 49 trials, 1,863 participants, protein supplementation on top of resistance training. The benefit to lean mass rose with intake and plateaued at about 1.6 g/kg/day, with the upper confidence limit at 2.2. That is the range we use: 1.6 as the floor, up to 2.2 during a fat-loss phase or for people over sixty, whose muscle responds less to each gram ("anabolic resistance").

The per-meal figure matters because muscle-protein synthesis is switched on by a dose, not an average: about 2.5–3 g of leucine, which is 25–40 g of a good-quality protein, three or four times a day. A day of 30 g at breakfast and 100 g at dinner does less than the same total split evenly. Protein timing around training is far less important than hitting the daily and per-meal numbers.

Resistance training: the minimum that works

The dose-response for hypertrophy is well mapped. Schoenfeld's meta-analyses put the minimum effective dose at roughly four hard sets per muscle group per week and a sensible target at 10 or more; frequency of two sessions per muscle per week beats one for the same volume. "Hard" means within two or three reps of failure. Load is flexible — 30% to 85% of a maximum builds muscle similarly if the set is taken close enough to failure — which matters for joints, older adults and home training.

• Two full-body sessions a week of 45–60 minutes is the floor. Three is better; four is not much better than three for most people.
• Six movements: a squat or leg press, a hinge (deadlift, hip thrust), a horizontal push and pull, a vertical push and pull. Add calves, grip and loaded carries after sixty.
• Progress something every week — load, reps or sets. Muscle adapts to what it has already done.
• Power, not just strength, after fifty: fast concentric movement on light loads, step-ups, medicine-ball throws. Power is what prevents the fall.

The LIFTMOR trial (Watson 2018) is the proof that this is safe late: postmenopausal women with low bone density did heavy deadlifts, squats and overhead presses twice a week for eight months and gained spine bone density while the control group lost it, with no fractures.

Creatine

Creatine monohydrate is the most studied supplement in sports science and one of very few with evidence in older adults. A 2017 meta-analysis (Chilibeck et al., Open Access Journal of Sports Medicine; 22 trials, 721 adults over 55) found that adding creatine to resistance training produced about 1.4 kg more lean mass and greater gains in upper- and lower-body strength than training alone. The dose is 3–5 g a day, every day, no loading phase needed, no cycling. It is cheap, safe in healthy kidneys, and the early cognitive data in sleep deprivation are interesting if not yet decisive.

Two lab notes. Creatine raises serum creatinine slightly without harming the kidney, which is one more reason kidney function is measured as cystatin C. And it adds about a kilogram of water inside the muscle in the first weeks — the scale moves, the DEXA will show it as lean.

What to measure

• DEXA once a year: appendicular lean mass index, total lean mass and visceral fat. The only honest way to know whether a year of work, or a fat-loss phase, built or cost muscle.
• Grip strength twice a year, and a 30-second chair-stand count. Both are validated against the cohorts above.
• Training log: load × reps on the six movements. If it has not risen in eight weeks, something in protein, sleep or programming is wrong.
• Protein tracked for one ordinary week a quarter. Most people who think they eat enough are at 1.0–1.2 g/kg.
• Labs: cystatin C, ferritin, vitamin D, testosterone and estradiol (both sexes) and IGF-1 — the hormonal floor muscle is built on.

Where peptides and therapies fit

The lean-mass goal page describes the protocol we write for this: protein and training first, then — where IGF-1 and HbA1c allow — the growth-hormone-axis pairing CJC-1295 / ipamorelin, which is studied for raising pulsatile GH and IGF-1 and is the compound layer most people ask about. For anyone losing muscle on a GLP-1 medicine, the transition guide and the metabolic-health article cover how to protect lean mass through the deficit. Testosterone is the hormone that decides most of this after fifty and has its own article in hormones after 40.

Common mistakes

• Cardio only. Running does not maintain muscle, and endurance training alone can accelerate the loss after fifty.
• Protein back-loaded to dinner. Breakfast with 10 g of protein wastes a synthesis window every day.
• Training to a plan, not to failure. Sets stopped eight reps short of failure do little whatever the programme says.
• Losing weight fast without protein and lifting. Up to 40% of rapid weight loss is lean mass. A DEXA before and after is the only way to know.
• Judging the kidney by creatinine in anyone muscular or on creatine.
• Stopping after sixty because it feels risky. The trials show heavy training is safe and effective at every age; stopping is the risk.