90/90 Hamstring
Also works: Calves
Lying on your back with one leg flat and the other held at 90 degrees of hip and knee flexion, you repeatedly straighten the raised knee toward the ceiling and lower it back. Fixing the hip at 90 degrees is the whole trick: it removes the pelvis from the equation, so the range you gain is genuine knee extension rather than a lower back that learned to round.
Own the movement
Set up first, then execute. Every cue below is something you can check on your next set.
Before the first rep
- Lie on your back on a firm floor with one leg fully extended and its heel pressed down.
- Draw the working leg up so the hip and the knee are both bent to 90 degrees — thigh vertical, shin horizontal.
- Lace both hands behind that thigh to hold the femur exactly there, or loop a towel around it.
- Keep the back of your head and both shoulders on the floor rather than curling up toward the leg.
Every rep
Breathing & tempo — Exhale as the knee straightens, inhale as it returns. Two seconds in each direction with a one-second pause at the top; never hold your breath at end range.
How much, how often
Where to start, and what to change when it stops being hard.
Bodyweight only. 10-20 reps per leg, one or two sets, and it is safe to do daily. Progress by holding the top position for two or three seconds rather than by adding reps, and once you can fully straighten the knee with the thigh vertical, move to a leg-up hamstring stretch against a wall for more range.
What goes wrong
The errors that show up most often, and the cue that fixes each one.
Hold the femur with both hands and treat the thigh as fixed furniture. Extend only as far as you can with the thigh perfectly vertical, even if that is barely past halfway.
Press that heel down deliberately before every rep. A lifting heel means the pelvis is tilting to give you fake range on the working side.
Two seconds out, hold, two seconds back. Bouncing at end range triggers a protective contraction, which is precisely what you are trying to switch off.
Point the toes away instead of pulling them up, and reduce the knee extension by 10 degrees. Nervy sensations are nerve tension, not muscle, and pushing into them is counterproductive.
Why bother
In a standing toe touch the hamstrings, the lumbar spine and the pelvis all contribute, and most people quietly borrow range from the spine. Pinning the hip at 90 degrees against the floor locks that door — the only joint left to move is the knee, so what you feel is hamstring length and nothing else.
It is also active rather than passive. Straightening the knee under the quadriceps' own effort while the hamstring lengthens trains the nervous system to tolerate that end range under contraction, which transfers to real movement better than a limp 30-second hold does. That is why this reads as reps rather than a hold despite living in the stretching section.
Where it fits
It works as a warm-up because it is dynamic and will not blunt force production the way a long static hold can. 10-20 controlled reps per leg before deadlifts, squats or sprinting, or as a daily floor drill. Pair it with Romanian deadlifts if the goal is range you can actually use under load.
If this one isn't it
No kit, too hard, or too easy — here's where to go instead.
Same job, different kit
Start here instead
When this gets easy
Asked and answered
Is this a stretch or an exercise?
Both, and that is why it works. The quadriceps contract to straighten the knee while the hamstrings lengthen, so you are building tolerance to end range under active tension rather than just waiting in a passive position. Log it as mobility work, not as leg training — the loading is far too light to build strength.
Why can't I straighten my leg at all?
Because the 90-degree hip angle has removed every cheat you normally use. Plenty of people who can touch their toes cannot straighten the knee here, and that gap is exactly the information the drill gives you. Work in whatever range you have; the first 15-20 degrees usually come back within a few weeks of daily reps.
Should I flex my ankle or leave it relaxed?
Relaxed ankle keeps it on the hamstring. Pulling the toes toward your shin adds the calf and puts tension on the sciatic nerve, which is useful if that is your goal but is also the fastest route to a sharp, nervy sensation. Start relaxed, add the ankle flexion later.
Can I do this before deadlifts?
Yes — this is one of the few hamstring drills that belongs in a warm-up. It is dynamic and brief, so it does not carry the temporary force loss associated with long static holds. Ten reps a side before your first working set is plenty.