With a leg press (all leg exercises really) you should never lock out the joint even with regular joints. Always stop with slight flex in the knee.
Biomechanically, joints are made to lock out. It is in this locked out position when they're in the most stable position to support loads and contributes the most towards the strengthening of the connective tissue at the joint - which is why isometric holds are sometimes prescribed to hypermobile people to help them strengthen these end ranges where they're more vulnerable than the regular person.
If you never train to lockout (i.e. you're shortening the range of motion) then you're not strengthening your joint, be it the knee or elbow, in the end range position and can often put more stress on it than if you locked out. In
powerlifting and
weightlifting if you're not locked out, the lift isn't passed. Doing any sort of straight limb isometric holds in things like
gymnastics you have to lock out to hold the position. And so on. 'Locking out is bad' as an absolute statement is just as much nonsense as all the advice not to squat deep or allow the knees to come forward because it's 'bad',
despite being thoroughly disproven scientifically.
There are contexts when you shouldn't lock out:
- when you come down on a fully locked joint with no movement to absorb the shock e.g. if you're jumping up and down, you don't want to land on locked knees
- if you have an acute knee joint injury such as a meniscus tear or a degenerative joint disease and knee extension causes pain.
- immediately following knee surgery
- if you go into significant, visible or painful hyper-extension in a tall-knee position (hence the advice to stop at normal end ranges)
The other thing is that if you're loading silly amounts of weight onto a leg press, the chances are overwhelmingly that you're likely using a tiny range of motion to stroke your ego, and the kind of loads 95% of people will be using for a
good range of motion leg press is such that locking out simply won't compromise joint safety in any way.
. I only play intermittently/at most once a week and at a pretty low level. Regardless of the condition, I need to build my strength across the board any way. Wonder if it's worth using a PT for the first few hours who knows about hypermobility as the only machines I have used a gym is the rowing machine and treadmill.
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