Which supplement is best for strength?

A one-rep max has two halves: the neural half that makes a lift a skill and supplies most early gains, the muscular half that grows with training age, and why a supplement can reach one and not the other

Which supplement is best for strength is answered badly whenever strength is treated as one thing, because a one-rep max is two things added together, and a supplement can reach one of them at most. The first is the neural half. A heavy lift is a skill: the nervous system has to recruit the largest motor units, fire them at a high rate, coordinate the muscles that move the bar with the muscles that stabilise it and silence the muscles that oppose them, and do all of it in the right sequence under a load that is trying to fold the lifter in half. The strength training research is clear that most of the early gains in a one-rep max come from this half, from the nervous system learning the lift, which is why a beginner adds weight to the bar every session for months with almost no visible change in muscle size, and why a lifter who switches to an unfamiliar movement is suddenly weak in it while being just as muscular. The second is the muscular half, the cross-sectional area of the tissue doing the work, which contributes a growing share of the total as training continues and the nervous system runs out of easy improvements, and which is why advanced lifters have to get bigger to get stronger when beginners do not.

The split matters for the question because the two halves respond to different inputs and because the shelf is sold to people who do not know which half they are short of. The neural half is built by practising the lift: heavy singles, doubles and triples at high intensity with full recovery between sets, the same movement repeated often enough that the pattern is grooved, and the variation kept small enough that the skill is not constantly reset. Nothing in a tub reaches it. There is no supplement that improves motor unit recruitment, firing rate or intermuscular coordination in a trained lifter, and the products that imply they do, the pre-workouts promising focus and the nootropics promising mind-muscle connection, have no strength trials to show for it. A lifter whose one-rep max is stalled because their programme has them doing sets of twelve on machines has a neural problem, and the answer is a programme that practises the lift heavy, not a cupboard.

The muscular half is where supplements can act, because tissue is built from the extra work a session can be made to contain and from the material that work is built with, and two products act there with evidence. The rest of this page is about those two, about the one product sold for strength that acts in the wrong energy system, and about the products that act nowhere, and the sorting is done by the half: a product either reaches the muscular half over a block, reaches the session's expression of strength for an hour, or reaches neither, and the shelf is read in that order.

Two halves and a sorting rule, and the two products that pass, the one in the wrong system, and the worked example, which is the next section.

The two products that reach the muscular half or the session: creatine over a block, caffeine for an hour; beta-alanine in the wrong energy system; the boosters placed nowhere; the worked example; and the verdict

Creatine monohydrate reaches the muscular half, and it is the best supplement for strength by the only measure that counts, the meta-analyses. At 3 to 5g a day every day, after the muscle store is saturated by a count of around twenty-eight daily doses or a short loading period, it lets the muscle regenerate energy faster in the first seconds of a hard effort, which buys an extra repetition on a heavy set or a slightly heavier top set, and the extra work accumulates over a block into one to two kilograms of lean mass and a few percent on strength measures compared with training alone. It has an authorised claim for physical performance in repeated short bursts of high-intensity exercise, which describes a heavy set exactly, a safety record in healthy adults at those doses that the long-term trials support, and a price in pence a day. The effect is real and modest, larger in people with low starting stores such as vegetarians, and realised only in a programme that asks for more over the block, because creatine adds capacity and the programme has to spend it. A lifter who takes creatine and lifts the same weights for the same sets gets a slightly fuller muscle and the same one-rep max.

Caffeine reaches the session rather than the tissue. At 3 to 6mg per kilogram about an hour before, it lowers perceived effort and improves strength endurance and power output in the pooled trials, and in the one-rep max trials it adds a small amount on the day, by letting the lifter express more of the strength they already have rather than by adding to it. It is a tablet for the session that matters, skipped on days when the night's sleep matters more, and it does nothing to either half between sessions; a lifter who stops taking it is exactly as strong as before and feels the sessions a little harder. Both products have authorised claims and both are commodities, which is why the best supplement for strength costs less than a coffee a day in total.

Beta-alanine is sold for strength and acts in the wrong energy system. It raises muscle carnosine, which buffers the acid that accumulates in efforts lasting roughly one to four minutes, and the meta-analyses find a small benefit in that window and none in efforts under a minute, which is where every heavy set lives; a rower or an eight-hundred-metre runner has a reason to take it and a powerlifter has none, and the tingling it produces at a full dose is the one effect a lifter will reliably feel. The boosters act nowhere. Testosterone boosters audited across dozens of products showed almost no data and no effect on the hormone; the pre-workout blends contain caffeine, which works, diluted with ingredients that do not; HMB has small effects in untrained or older people and none in trained lifters; and the nitric oxide products produce a pump, which is a sensation and not a strength. A lifter who spends on any of these for strength has bought the neural half's problem a muscular half's non-solution.

The worked example is placed on the mineral's own claim and not on this page's question: {FL}, 1500mg magnesium bisglycinate stated as 300mg elemental at 80% NRV, two capsules with the evening meal, with authorised claims for normal muscle function, normal protein synthesis and electrolyte balance, which describe the mineral's role in a working muscle and are not a strength claim, batch tested for lead, mercury, arsenic and cadmium, UK made, 180 capsules for £19.99 at 22p a day, taken by a lifter whose plate is short of the mineral for the plate. The full label breakdown is here.

The verdict: the best supplement for strength is creatine, because it is the only one that reaches the muscular half of a one-rep max over a block, and a caffeine tablet before the session that matters reaches the session. The neural half, which supplies most of the gains a lifter will ever make, is reached by practising the lift heavy and often, and no tub touches it. Beta-alanine is for a different energy system, the boosters are for nobody, and the mineral is for the plate.

What to check on the label

Questions people also ask

What is the single best supplement for strength?

Creatine monohydrate, at 3 to 5g a day every day after the store is saturated, because it is the only supplement that reaches the muscular half of a one-rep max over a training block, adding a few percent to strength measures and one to two kilograms of lean mass in the meta-analyses on top of training, with an authorised claim for physical performance in repeated short bursts of high-intensity exercise and a price in pence; a caffeine tablet before the session that matters adds a small amount on the day by lowering perceived effort, and nothing else on the shelf reaches either half.

Why does a beginner get stronger without getting bigger?

Because most early strength gains come from the neural half of the lift: the nervous system learning to recruit the largest motor units, fire them at a high rate and coordinate the muscles that move the bar with those that stabilise it, which is why weight goes on the bar every session for months with little visible size change and why a lifter is suddenly weak in an unfamiliar movement while just as muscular; the muscular half contributes more as training continues, which is when creatine and protein have their effect and when advanced lifters have to get bigger to get stronger.

Does caffeine actually make you stronger?

It lets you express more of the strength you already have for about an hour: at 3 to 6mg per kilogram before a session it lowers perceived effort and improves strength endurance and power output in the pooled trials, with a small one-rep max effect on the day, and it adds nothing to either half between sessions, so a lifter who stops taking it is exactly as strong and feels the sessions a little harder; it is a tablet for the session that matters, skipped when the night's sleep matters more, and it is the one thing in a pre-workout blend that works.

Is beta-alanine good for strength?

No; it raises muscle carnosine, which buffers the acid that accumulates in efforts lasting roughly one to four minutes, and the meta-analyses find a small benefit in that window and none in efforts under a minute, which is where every heavy set lives, so a rower or middle-distance runner has a reason to take it and a powerlifter or bodybuilder has none; the tingling at a full dose is the one effect a lifter will reliably feel, and the money is better spent on creatine, food and sleep.

Does magnesium help with strength?

Magnesium has authorised claims for normal muscle function, normal protein synthesis and electrolyte balance, which describe the mineral's role in a working muscle and are not a claim about strength, and the trials of magnesium for strength in people who are not deficient are small and inconsistent; the worked example is 300mg elemental at 80% NRV in two capsules with the evening meal for 22p a day, batch tested for four metals and UK made, taken by a lifter whose plate is short of the mineral for the plate and not for the bar.

Sources

1. The neural adaptations to strength training literature: early strength gains come largely from the nervous system, improved motor unit recruitment, firing rate and coordination between muscles, with muscle size contributing more as training continues, so that a one-repetition maximum is part skill and part tissue and the two halves respond to different inputs. PubMed record
2. Rawson ES, Volek JS. Effects of creatine supplementation and resistance training on muscle strength and weightlifting performance. Journal of Strength and Conditioning Research 2003;17(4):822-831: creatine with resistance training produced around 8 per cent greater gains in maximal strength and around 14 per cent greater gains in repetitions at a given load than training alone. PubMed record
3. The caffeine and strength literature: meta-analyses report small but consistent improvements in maximal strength and power after caffeine doses in the range studied, typically 3 to 6mg per kilogram, with individual response varying. PubMed record
4. EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on the substantiation of health claims related to creatine and increase in physical performance during short-term, high intensity, repeated exercise bouts. EFSA Journal 2011;9(7):2303. https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2011.2303

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