I want to do this exercise which obviously puts some strain on the knee. I'm a 20-something male, 1.76 m , 65 kg.
I need to know if this exercise might cause me a injury on the knee. It seems there is a lot of load weight in it.
Edit: I confused injury with strain.
There's always strain on the knee when you use it for something. Actually this mode is probably safer than a full squat olympic style for a reason: Range of Motion is reduced and the starting point at the bottom of the movement is actually inertia free.
In cheaper words, its different from a half squat because when you are in the lowest position you sit on the box and so tension on the knee and ankle joint is heavly reduced.
So, yes, it's going to put strain on your knee, but nothing to worry about as long as you perform the movement correctly.
The reason some people say deep squats are bad for your knees is because they heard it from someone and are just blindly repeating it. Some knowledgeable people say this because the patellar tendon is in a stretched position at the bottom of a squat. However, this is not a problem if you don't have pre-existing knee problems (if you do, see a doctor): the tendon will strengthen to handle bigger and bigger loads.
If you perform any exercise without warming up you are more likely to get a strain/minor-injury. The movement is perfectly fine and as it is a unweighted (no barbell) movement, even more so.
As a side note, the bottom half of the movement that is restricted by the box is generally considered much more difficult as it requires better balance and flexibility to be able to push out of the position. Having a box means you won't do this part of the movement.
“Safe” is a somewhat relative term. There’s really no way anyone can give you a reliable answer to your question, or, this question without clarifying some things about you. For example, your propensity for injury/strain, any prior knee injuries, and, your ability to recover from each session to name a few. In all actuality, weight training/exercise is not a risk free activity. It’s designed to put stress on your muscles and joints so that growth can be accomplished. And, that’s why some clubs/gyms make their members sign waivers when they join.
You are not guaranteed to be injury/strain free even if your form is perfect. Overuse Syndrome is common for beginner weight trainers. The most you can hope for is to reduce the risk of injury by using correct form, recovering sufficiently from each session, and supporting your efforts with a nutritionally sound diet.
