Thirty seconds. You release the hamstring, shake it out, and pull the other leg forward. The number was in your head before you started — carried from a coach, a fitness app, a stretching poster in a physical therapy office — and the timer decides when you’re done.
That per-hold count has dominated the stretching conversation for decades. The evidence that finally put a threshold on how long you should hold a stretch to improve flexibility didn’t answer in seconds at all.
How Long Should You Hold a Stretch to Improve Flexibility?
Flexibility gains plateau at 4 minutes of cumulative stretching per muscle group per session and 10 minutes per week. How those minutes are divided — across holds or sessions — does not matter. Neither does intensity, age, sex, or training status. Keep individual holds under 60 seconds to avoid strength loss.
— Ingram et al. 2024 · Sports Medicine · n=6,654 across 189 studies
It answered in total minutes per muscle group. Across 189 studies covering more than 6,600 adults, flexibility gains climbed as stretching time accumulated — then flattened at 4 minutes per muscle group in a single session. Beyond that point, additional time added nothing. Not 4 minutes per hold. Four minutes total, from any combination of hold lengths.
For long-term flexibility — the kind that builds over weeks and stays — the threshold was 10 minutes per muscle group each week. How those minutes were split across sessions made no difference. Three sessions or six produced the same result, provided the weekly total reached the threshold.
Per session: 4 minutes cumulative per muscle group. Beyond that, flexibility gains plateau.
Per week: 10 minutes total per muscle group. How those minutes are split across sessions does not matter.
Intensity didn’t change the picture. Stretching to mild tension produced the same flexibility gains as pushing to the edge of discomfort. The body didn’t need harder effort — it needed enough accumulated time.
Age changed nothing. A lifter in their twenties and a 65-year-old beginner gained the same flexibility from the same dose. Neither age, sex, nor training history altered the outcome. The thresholds apply to everyone.
The one constraint on how you divide those four minutes is a ceiling: holding any single stretch for 60 seconds or longer costs real strength — enough to weaken a lift performed afterward. Under 60 seconds per hold, no significant force loss. The practical split: keep each hold under a minute, accumulate enough of them to reach the total. Where stretching fits among the full ranking of recovery methods the evidence supports depends on your goal — but for flexibility, the dose now has specific numbers.
What drives the threshold is not what most people picture. Stretching does not physically lengthen muscle tissue — no study has observed a change in fiber length from acute or chronic stretching. What adapts is the nervous system’s tolerance to discomfort at end range. You are not elongating anything. You are training your body to tolerate a deeper position. That is why accumulated time matters and intensity does not: tolerance builds through total exposure, not through how hard any single hold pushes.
The evidence is not equally strong on both thresholds. The 10-minute weekly number rests on firm statistical ground. The 4-minute per-session figure was drawn from the overall shape of the data — a consistent pattern, but not as formally confirmed. The practical direction is clear. The exact per-session ceiling may sharpen as future research tests longer durations.
The dose framework is set: four minutes per session, holds under sixty seconds, ten minutes total per week. The count on your mat still runs. The target has shifted — not the seconds in a single hold, but the minutes that build across every hold.
If the tissue stays the same length and every flexibility gain is a nervous system adaptation, what stretching actually does to your body goes deeper than any timer can measure.