The acute trade-off
A long static stretch held before a maximal effort can temporarily reduce strength and power. Reviews of the literature commonly report decrements in the single-digit percentage range, with the larger effects tied to holds of roughly 60 seconds or more per muscle; brief holds under about 30 seconds tend to show little or no meaningful loss. The exact figure varies by study, muscle, and protocol, so it is best treated as a small-to-moderate range rather than a fixed number.
The effect is transient and is thought to fade within tens of minutes, especially if dynamic activity follows.
Why it happens
Proposed mechanisms include reduced muscle-tendon stiffness, which can blunt force transmission, and altered neural drive to the stretched muscle. Both are temporary. This is why static stretching is generally moved out of the immediate pre-performance window rather than abandoned entirely.
Practical takeaway
For a max lift, sprint, or jump, dynamic warm-ups are usually preferred just beforehand, with longer static stretching saved for after training or separate sessions if flexibility is a goal. This is general educational information about training timing, not medical advice.