Should you lockout your knees on Leg Press?
You be the judge, Warning: The above video will make you cringe!
In all seriousness should you lock out your knees on exercises like Leg Press, or Squats? The problem when locking your knees during heavy movements like leg press is that all of the weight being lifted shifts directly from the trained muscle to the knee joint itself. Your bones and joints, with the support of your skeletal muscles, can support a tremendous amount of weight. But that doesn’t mean you should unnecessarily test them. With improper form, technique, or loss of balance your weight can unevenly shift to over accommodate one area of another.
The above video example is too low quality to critique his form. But this is clearly too much weight to be supported by his locked out knee joint. Keeping the quadriceps and hamstrings engaged throughout the exercise by stopping about 1″ before “lockout” would have prevented this. You can also see he’s self-spotting by pushing his own legs into lockout position. Due to the angle of the break, you can tell his feet are placed fairly high making locking out even more dangerous from that position.
Now there are some hypertrophy benefits from locking out on certain movements when performed properly. Let’s take TUT style (Time under tension) Pulley Push Downs, using a high rep range e.g. 15 reps with a slow tempo. When fully locked out on this exercise vs. stopping prematurely you will engage the rear triceps head to a greater degree, essentially rushing more blood into the trained muscle, expanding tissue (The is the reason you’re told to “squeeze” the bicep muscles at the end range when curling). This is considered an “advanced movement” and not recommended for most. But the reality is you will not be able to handle very heavy weight on this movement IF you can go a full 15 reps TUT style, so the amount of overall stress to the joint is minimal, although I save my final few reps for locking out.
I personally have been using this technique for around 15 years and have never experienced an injury from training in my life or experienced sore joints. But, you would never see me locking out on heavy sets with low reps, simply because the amount of weight applied would be too stressful on the joints. There is a time and a place when TO, or when NOT to lock out during training.
“Bad joints” are one of the main reasons, athletes of all sports have to take time off or even worse retire earlier than planned. So when you observe some of our strongest professional athletes train you’ll almost never see them lockout. Take Ronnie Coleman’s Leg Day for example, can you find him lockout even once? (Granted he’s lifting in the 1000+lb range often!)
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