I am doing 100 push ups program and I have reached a plateau at around 65. The program suggests to have a day off between training days, but since I don't get desired results I would like to increase frequency. Is it the right move or should I think about something else?
Frequency, weight to use, sets/reps are all point-in-time individual specific settings. What works for you today many not work tomorrow or for anyone else. What I would recommend is:
Specific to plateauing - there are different methods to get over your current max:
to provide specific advice we would need to know what happens after 65 - are you sore? hands numb? just tired?
Your muscles only build while they are resting. Exercise breaks them down and works them hard. When you are not working your muscles, they start rebuilding themselves and making them strong.
In short, rest is an important aspect of building strength. If you can't go past the 65 barrier, it's possibly because they aren't getting enough rest in between. At a certain point, your muscles may need more rest than the one day in between. Your two choices are then:
In free weights, you can sometimes break through a plateau by a process called deloading. Essentially it is taking 10% of the weight off the barbell, and then slowly increasing back to where you were. Many times you can get through the plateau because you gave your muscles some more recovery time. If the deloading doesn't work a couple times in a row, you have to resort to cutting the number of sets.
Applying the same principle to you, I would recommend that you:
You might feel like you are going backwards, but you are putting your body back into a place where it can rebuild its muscle in time for the next workout. The hope is that it has spare capacity when you hit the limit.
I wish I could produce a direct link to the source of this information, but it is contained in the Stronglifts 5x5 special report. The report is free, has some pretty good information, but you have to register to get it.