Can stretching make a muscle grow?

Can stretching a muscle, for a long time and often, make it grow? The question sounds far-fetched; it is not. It has been asked dozens of times in humans, and the answer is yes, a little — the price to pay being the real subject of this article.

What meta-analyses find

The largest one reviewed 42 studies and 1,318 participants: long-term static stretching increases maximal strength (d = 0.30) and muscle size (d = 0.20). Both effects are real and statistically significant. Both are also small — that is the word used by the authors.

A second 2024 meta-analysis, focusing solely on hypertrophy and covering 25 studies, is even more cautious: overall effect uncertain, modest potential benefit (SMD = 0.118). Its practical conclusion is worth quoting as it is — static stretching might not be very effective for making a muscle grow, barring spending very high amounts of time on it.

On strength and power, 41 studies show effects of the same magnitude: 0.21 for strength, 0.19 for power. But this particular work finds something else, and it is the most useful result of the entire dossier.

The gains are almost three times greater in sedentary individuals, and they also increase with the participants' age. In other words: the further you start from, the more stretching pays off. For someone who already trains, the weak version of the effect applies.

The trial that truly poses the question

Six weeks, 69 active participants, and a head-to-head comparison: on one side, standard hypertrophy training, on the other, prolonged static calf stretching — one hour a day. Result: both groups increased their maximal strength and muscle thickness, with no significant difference between them.

Five minutes a day: strength goes up, size does not

At a realistic dose — five minutes a day for six weeks, in 44 participants, maximal strength increases clearly (p < 0.001)… but muscle thickness does not. The authors draw the obvious conclusion: this strength gain cannot be explained by hypertrophy, it likely comes from neural adaptations.

And the reverse also exists: six weeks of stretching five times a week thickened the gastrocnemius by 5.6% and lengthened the fascicles — without any gain in maximal voluntary contraction or activation. The muscle changed shape without becoming stronger.

Placed side by side, these two studies say something important: strength and size do not move together under the effect of stretching. Each can move without the other, depending on the protocol.

What seems to make the difference

A 2020 review counted: out of the ten human studies existing at the time, only three reported a net effect on muscle structure — and that was mainly when the stretch was performed with a device or an overload. Low-intensity passive stretching, the kind done on the floor after a training session, altered neither size nor architecture.

The two 2024 meta-analyses point in the same direction when looking for what predicts gains: longer stretch duration, longer intervention, higher frequency, and greater exercise variety and total duration. Always the same currency of exchange: time.

The honest read fits in two sentences. If you already train, stretching will not grow your muscles at a rate worth the time invested — but it doesn't prevent you from doing so either. If you cannot do resistance training, or if you are starting from scratch, it is one of the few stimuli with proven numerical evidence that it does something.

Every figure in this article comes from a study you can open: the underlined mentions lead to the summary of the work it is taken from, written solely from the abstract. The corpus here is intentionally small — seven works, including four recent reviews or meta-analyses — because that is what exists solidly on this specific question. Informative content, which does not replace the advice of a professional.