What the strength literature agrees on
Longetic read the 2026 ACSM position stand, the WHO 2020 guidelines and the UK Chief Medical Officers' guidelines side by side, and they land on one shared minimum: work all the major muscle groups at least twice a week. Everything after that, the load on the bar, the number of sets, whether you stop short of failure, changes how big the result is, not whether there is one.
Two of those documents are new. The American College of Sports Medicine announced its resistance training position stand on 18 March 2026, for the April 2026 issue of Medicine & Science in Sports & Exercise, and it is the first update to that stand in 17 years. The UK Chief Medical Officers' guidelines carry the line Updated 10 July 2026.
One caveat about where the ACSM numbers in this article come from. We checked the ACSM announcement page and it prints no training frequency, no load range and no weekly volume at all. The position stand itself sits behind a journal paywall we could not open. Every ACSM figure below is quoted from the slide deck ACSM published alongside the stand on its own site, and that is said here rather than hidden.
| Source | Days a week | Muscle groups | Date on the document |
|---|---|---|---|
| ACSM position stand | At least 2 | All major groups | April 2026 issue |
| WHO guidelines | 2 or more | All major groups | 2020 |
| UK Chief Medical Officers | At least 2 | Upper and lower body | Updated 10 July 2026 |
| NHS England, adults 19 to 64 | At least 2 | All major groups | Reviewed 22 May 2024 |
| Ministerio de Sanidad, Spain | At least 2 | Grandes grupos musculares | Febrero 2023 |
The NHS page in that table is worth a second look. It was last reviewed on 22 May 2024 and is not due for review again until 22 May 2027, which means it has not been re-reviewed since the UK Chief Medical Officers refreshed the guidelines underneath it on 10 July 2026. What it prints is still current NHS wording. It is simply not the newest evidence review in the table.
Rule 1: any training beats none
Consistency outranks programming: the slide deck published with the 2026 ACSM position stand puts the point bluntly, and the UK Chief Medical Officers make the same point in their own words. Barbells, resistance bands and body weight all count as strengthening activity in every document checked here, and the programme you abandon in week three beats nothing, but only barely.
The ACSM deck says: "The best resistance training program is the one you will actually do." The UK Chief Medical Officers put the floor even lower: "Muscle strengthening activities should be done at least 2 days a week, but any strengthening activity is better than none."
Rule 2: work every major muscle group at least twice a week
This is the one number nobody argues about: five separate documents, written by five different bodies between 2020 and 2026, print the same minimum, all the major muscle groups at least two days a week. They disagree about load, about volume and about effort, but not about this.
The NHS tells adults aged 19 to 64 to "do strengthening activities that work all the major muscle groups (legs, hips, back, abdomen, chest, shoulders and arms)" and to do them "on at least 2 days a week". Spain's Ministerio de Sanidad prints the same instruction in its February 2023 recommendations for adults: "Actividades de fortalecimiento muscular que incluyan los grandes grupos musculares." The ACSM deck calls it the critical step: "The most critical step for health is to engage all major muscle groups at least twice a week."
There is a nuance the guidelines do not spell out, and it matters if you are deciding between two sessions and four. Two meta-analyses that matched weekly sets across groups found the frequency effect on strength disappeared. Grgic and colleagues reported in Sports Medicine in 2018 that when volume is equated, "there was no significant effect of RT frequency on muscular strength gains". Ralston and colleagues reached the same conclusion the same year. Read twice a week as a sensible way to spread your sets, not as a separate lever. If you want the one-line version of this rule alongside ten other habits, it is in our eleven health essentials for a long life; this page is the subject rather than the bullet.
Do you have to lift heavy?
Not for muscle size: light loads and heavy loads build comparable amounts of muscle when the work is taken close enough to effort. Heavy loads do win for one thing, maximal strength, the single hardest lift you can manage. So the honest answer depends on which of those two you came for, and most people came for both.
Schoenfeld and colleagues pooled the comparisons in the Journal of Strength and Conditioning Research in 2017 and found that "Changes in measures of muscle hypertrophy were similar between conditions", while "Gains in 1RM strength were significantly greater in favor of high- vs. low-load training". A network meta-analysis led by Lopez in Medicine & Science in Sports & Exercise in 2021 agreed on both halves: "Although muscle hypertrophy improvements seem to be load independent," and "increases in muscle strength are superior in high-load RT programs."
For the strength half, the ACSM deck prints a figure in its own table: "Intensity: ≥80% 1RM (dose-response)". That is what the society published for the strength goal. It is not a prescription for you, and nothing in this article is. What load suits your joints, your training history and whatever else is going on in your body is a conversation with a clinician, not a number from a slide.
Rule 4: more weekly sets, more muscle
Volume is the lever with the clearest dose-response: add sets per muscle group per week and, up to a point, you add muscle. The ACSM deck names a working figure for the growth goal, but what nobody can tell you from the evidence is where your own ceiling sits, because the studies that chased the upper end used young trained men.
The ACSM deck prints "Volume: ≥10 sets/week (dose-response)" in its hypertrophy row, and in the discussion: "Aim for higher weekly volume (~10 sets per muscle group)." The slide for the strength goal is different and smaller: "Volume: 2-3 sets/session".
Above that figure the evidence thins out fast, and the paper most often quoted for a higher range says so itself. Baz-Valle and colleagues wrote in the Journal of Human Kinetics in 2022 that a range of "12-20 weekly sets per muscle group may be an optimum" standard recommendation, but their own meta-analysis found no difference between moderate and high volume for two of the three muscles they examined, and the sentence is explicitly limited to young trained men. Treat the higher numbers as a ceiling someone else measured, not a target.
Do you have to train to failure?
No. Stopping a set a repetition or two short produces broadly the same strength and the same growth as grinding to the point where the bar stops moving. That is the finding in the pooled data, and it is one of the few places where the comfortable answer and the evidence-based answer are the same answer.
Grgic and colleagues concluded in the Journal of Sport and Health Science in 2022 that "Training to muscle failure does not seem to be required for gains in strength and muscle size." They were careful about the other direction too: "However, training in this manner does not seem to have detrimental effects on these adaptations, either." Refalo and colleagues, writing in Sports Medicine in 2023, found no evidence that training to momentary muscular failure beats stopping short for muscle growth.
Two qualifications belong with that. Grgic found a small signal favouring failure for growth in people who were already resistance trained, and every study in that analysis used young adults. The ACSM deck reaches the same practical place by a different route, reporting that training to momentary muscle failure did not consistently change outcomes for the average healthy adult.
Rule 6: protein, in the range the ISSN prints
The International Society of Sports Nutrition published a daily range in its 2017 position stand, and it is quoted here exactly as the society printed it. It is a published figure, not a recommendation from us and not a target for anyone reading. What you eat and what you take sit with the clinician who knows your kidneys, not with a sports nutrition paper.
The society's position stand, published in the Journal of the International Society of Sports Nutrition on 20 June 2017, names "an overall daily protein intake in the range of 1.4-2.0 g protein/kg body weight/day (g/kg/d)". On how to spread it, the same stand says: "General recommendations are 0.25 g of a high-quality protein per kg of body weight, or an absolute dose of 20-40 g." On timing it is deliberately loose: "The optimal time period during which to ingest protein is likely a matter of individual tolerance".
No product is named in this section and none will be. If you start taking something for training, the useful move is not to optimise it. It is to write down the name and the strength exactly as printed on the container, with the date you started, and to bring that line to your next appointment along with everything else you take.
Does it still work at 70?
Yes for strength, and emphatically so: the pooled trials in healthy older adults show large gains in muscle strength. Gains in muscle size are real but much smaller, and the honest framing matters here, because strength is what carries the shopping and keeps you off the floor. Size is a side effect people over-weight.
Borde, Hortobagyi and Granacher pooled the randomised trials in Sports Medicine in 2015, with an inclusion rule they state plainly: "Only RCTs that examined the effects of RT in adults with a mean age of 65 and older were included." Their result splits in two. "RT improved muscle strength substantially (mean SMDbs = 1.57; 25 studies)," but it "had small effects on measures of muscle morphology (mean SMDbs = 0.42; nine studies)."
One limit on that evidence, stated by its authors: it covers healthy older adults. Trials in frail and mobility-limited people were outside the review, and the authors call for more work there. The UK Chief Medical Officers describe the stakes in the same register: "A loss of muscle strength in advancing age is the primary limiting factor for functional independence."
Rule 8: keep your doctor in the loop, and keep the paperwork
England and Spain give different advice about seeing a doctor first, and knowing which one applies to you is the point of this rule. Either way, a change in training is a thing worth writing down, with the date, because it is the kind of detail that explains a number on a report six months later and nobody ever remembers it unprompted.
England is explicit. The NHS page for adults aged 19 to 64 says: "Speak to your GP first if you have not exercised for some time, or if you have medical conditions or concerns." Spain is narrower, and this is worth stating precisely rather than rounding off. We checked the Ministerio de Sanidad recommendations for adults from February 2023 and the ministry's Estilos de Vida Saludable page for adults, and neither tells a healthy adult to see a doctor before starting. The ministry page addresses a smaller group: people with a disability or a medical condition "pueden consultar con sus profesionales sanitarios de referencia". So the English instruction is broader than the Spanish one, and reading one as the other gets you the wrong answer in both countries.
| What you change | What the evidence shows | Where the evidence is thinner |
|---|---|---|
| Days per week | 2 or more is the shared minimum | Frequency adds no strength once weekly sets match |
| Load | Light and heavy build similar muscle | Heavy loads win for maximal strength |
| Weekly sets | More sets, more muscle, up to a point | Higher ranges come from young trained men |
| Going to failure | Not required for strength or size | A small signal in already trained lifters |
| Age | Large strength gains after 65 | Gains in muscle size are small |
On keeping a record, we are not hiding behind anyone. We checked the NHS guidelines page for adults, the Spanish ministry recommendations and the ministry's adult activity page, and none of the three says anything about keeping a log, a diary or a record of what you do. That advice is ours, and the reason for it is narrow: when a result shifts, the first useful question is what else changed, and a training change with a date attached answers it. Longetic keeps the surrounding record, the lab reports with each biomarker next to your own lab's reference range, the visits and the list of what you take, so the date you started lifting sits beside the numbers it might explain. For the rest of what goes into that visit, see what to write down before the appointment itself.
