Say you're stuck on a 120 kg benchpress for 2 reps. Can you apply "grease the groove" on the bench press so that you increase reps? Will this yield muscle gain?
more generally, can it be applied to any weighted exercise?
can it be applied to any weighted exercise
Yes and no.
When someone does a specific exercise regularly, he is “greasing” the neurological groove that allows him to fire the muscles that are involved with performing that specific exercise efficiently and effectively. Continually greasing the groove will make the exercise feel more and more natural and easier, allowing him to gradually do more reps and building his strength in that exercise(1).
It depends. If you are doing push-ups and you reached a point that more reps will do you no good, you can definitely add a weight vest and start over. Same goes for pull-ups, chin-ups, body rows and any other exercise that uses mainly your body as the form of resistance.
What about barbell/dumbbell weights etc?
Say you're stuck on a 120 kg benchpress for 2 reps. Can you apply "grease the groove" on the bench press so that you increase reps?
Not really. The purpose of GtG is not to completely exhaust or fatigue your muscles, but to make a specific "movement" feel as natural as possible by doing more and more repetitions of it. If your bench 1RM is 130kg and you try to repeat that throughout the day, it won't work and it will actually set you up for an injury.
What you could try instead:
Supposing we want to GtG on bench press and our 1RM is 130kg, one can definitely GtG by doing many sets with relatively low weight (40-60%). This will make the movement flow more naturally. However, this will mostly do nothing for your CNS. Your nervous system is getting fully triggered when you actually have a significant load to lift. Percentages less than 80% of your 1RM will hardly train your CNS. But...
Will this yield muscle gain?
Yes. Any amount of weight and repetitions will tear your muscle tissue. But you should have understood by now that muscle gain <> strength gain. You are getting stronger by progressively overloading, while you can build muscle with any kind of resistance.
It's up to you to decide whether you want to: