How to do the hamstring stretch
Sit on the floor with one leg extended and the other bent. Hinge forward from the hips, reaching toward your toes while keeping your back long. You should feel a pull along the back of the extended thigh, not behind the knee.
How long to hold it
The most common recommendation for a static hamstring stretch is 30 seconds per side, repeated 4 times, with a short break to switch sides. That is exactly how this timer is pre-configured: press start and it counts every hold, tells you when to switch sides with a distinct sound, and gives you 30 seconds of rest after the final rep. Your eyes never leave the floor.
Common mistakes
Rounding the back to reach further (hinge from the hips instead), bouncing during the hold, and locking the knee so hard the pull sits behind the joint.
Why it's worth doing
Tight hamstrings pull on the pelvis and are a common contributor to lower back discomfort. Regular holds improve forward-bend range and make squats, running and deadlifts feel smoother.
About this timer
ExtendTimer is a free stretching timer with sound cues for every phase: a steady tick while you hold, a count-in when you switch sides, and an alert on your final rep. It works offline, installs to your home screen like an app, and needs no account. Routines of up to two stretches are free forever; Pro ($4.99/month or $29.99/year) unlocks unlimited routines and the full sound studio.