90/90 hamstring stretch (active knee extension)
Lying on your back with the hip and knee bent to right angles, you hold the thigh still and slowly straighten the knee toward the ceiling, then bend it back. Your own thigh muscles straighten the knee, so no strap is needed. It is the Extender, one of three lengthening exercises in Askling's protocol, which returned footballers with hamstring strains to full training in 28 days rather than 51.
Movement guide
90/90 hamstring stretch (active knee extension)
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Easier option
3D demoSupine hamstring stretch with a strapBeginner · No equipmentSuggested next step, beginner grade.
This move
3D demo90/90 hamstring stretch (active knee extension)Beginner · No equipmentBeginner grade.
Harder option
3D demoContract-relax hamstring stretch (PNF)Intermediate · No equipmentSimilar move, intermediate grade.
Source-researched guide. Clinical review is pending.
How to move
- Lie on your back with one leg long on the floor.
- Bend the other hip and knee to right angles, so the thigh points at the ceiling, and hold the back of that thigh with one or both hands to keep it still.
- Slowly straighten the knee, sending the foot up toward the ceiling, until the back of the thigh pulls, stopping just before it hurts.
- Pause for a moment, then bend the knee back to a right angle. Repeat, then change legs.
Form cues
- Keep the thigh still; only the lower leg moves.
- Take about 2 seconds up and 2 seconds down.
- Avoid: kicking the leg up fast or forcing the knee straight.
Practice and cautions
3 sets of 12 slow straightenings each leg, stopping just before pain: the Extender's dose in Askling's protocol, done twice a day there. Once a day is our editorial starting point for general flexibility.
Tingling or burning down the leg is a nerve signal rather than a stretch: bend the knee and ease off. This is movement education, not an assessment or treatment prescription. Stop for sharp or increasing pain, dizziness, numbness or tingling; seek individual guidance for symptoms, injury or restrictions.
Sources and review status
Sources support the educational description; they do not establish that this exercise is suitable for you.
- Askling 2013 · After a hamstring strain, a programme of three lengthening exercises returned elite footballers to full training in 28 days, against 51 with conventional exercises (RCT of 75 players, BJSM) ↗
- Physiotutors · The Askling protocol (a secondary description of the Extender: the thigh held at about 90°, slow knee straightening to just before pain, 3 sets of 12 twice a day) ↗
- Webright 1997 · Repeated active knee straightening, done sitting, gained as much hamstring range as a static stretch over 6 weeks (RCT of 40 adults, JOSPT) ↗
- Free Exercise DB · community text ↗
Unlicense · Free Exercise DB contributors; derived from wrkout/exercises.json. Text import; no photographs or media. · Revision f00c92c7dcf1216a928a52c3706c7ce8e2f71ed5
No variation is labeled clinically validated.
What it works
Equipment
None: body weight and floor space.
Level
Beginner. See the easier and harder options above.
Workouts that use it
- Yoga after a hamstring strain: a 25-minute class with the lengthening exercises built in, and no deep forward folds · 25 min
- Off-track Pilates for sprinters: a 25-minute class for trunk control while the legs move, the front and back of the hip, and one-leg balance · 25 min
- Pilates after a hamstring strain: a 25-minute class with the hamstrings working, not stretching · 25 min
- Hamstring Pilates: a 25-minute class that works the backs of your legs, then stretches them · 25 min
Pain guides that use it
Part of a staged plan, with when to get help first.
- Hamstring strain exercises: from first days to sprinting
- Hamstring pain when running: strain, sitting-bone tendon or back, and the way back to speed
- Thigh pain: a strain or dead leg, the hip and back, a burning nerve, a clot and how to build back
- Back of thigh pain: a hamstring strain or tendon, sciatica, cramp or a clot, and how to build back
Guides that use it
- Pilates for sprinters guide
- Pilates for a hamstring injury guide
- Pilates for tight hamstrings guide
- Yoga for tight hamstrings guide
- Yoga for a hamstring injury guide
- Yoga for sprinters guide
- Assisted stretching guide
- Bowen therapy guide
Show all 12 guidesShow fewer guides
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Questions people ask
What muscles does the 90/90 hamstring stretch (active knee extension) work?
Mainly the hamstrings, with help from the calves.
What equipment do I need for the 90/90 hamstring stretch (active knee extension)?
No equipment: your body weight and a little floor space.
Is the 90/90 hamstring stretch (active knee extension) good for beginners?
It is graded beginner, so it suits most people starting out. When it feels easy, try the Contract-relax hamstring stretch (PNF).
What is an easier alternative to the 90/90 hamstring stretch (active knee extension)?
Try the Supine hamstring stretch with a strap. It is the suggested step down from this move.
How do I make the 90/90 hamstring stretch (active knee extension) harder?
Progress to the Contract-relax hamstring stretch (PNF) or the Pyramid pose (Parsvottanasana). Follow that guide’s technique and any stated timing.