There are two parts to every lift, extension and contraction. It is known that the human body is capable of "lifting" 130-140% of the concentric phase during the eccentric phase. This is a failsafe mechanism - you can always (relatively safely) lower what you can lift. You can use this to your advantage. Get into the start position and lower down on one arm. Do your one rep. Try again - lower under control. If you can't press up again, then use both arms and get back in the start position. Try again - lower under control. Repeat for x reps. I have used negatives in the past, specifically to improve my weighted pullups. Still do some occasionally and it's a good way to break plateaus. As to what sort of program to do - that's an involved question. To give you a start, I follow a program commonly referred to as PTP. 2 sets of 5 reps, 4 compound exercises, 5 mornings a week. It's a strength program. Most strength programs will focus on 5 or less reps per set and up to 5 or so sets. Most will focus on compound exercises.
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