Advantages & Disadvantages
Good convergent press machines are ideal because they do the following:
1.Require almost no manipulation to grab and release the handles.
2.Copy the range of motion of dumbbells without having the same restrictions when using heavy weights.
3.Generally place the muscles in the correct trajectory (at least on the best machines).
4.Protect you from any loss of balance.
5.Have no weight limitations (such as those that you encounter with dumbbells).
But machines are not perfect:
Unfortunately, good convergent machines are more difficult to find than bad machines.
The exercise often begins with a positive phase (rather than a negative phase as with bar), which makes the first repetition more difficult.
Some people do not like having the trajectory completely guided, but this rigidity prevents a lot of injuries that might happen to people using bars or dumbbells.
Preparation
-Set the machine to the correct weight and adjust the seat if necessary
-Sit on the seat, with your back up against the back rest and torso erect
-Grasp the handles, and if available, push your feet down on the foot platform to help push the handles away.
Execution
-Push the handles away from your body by contracting the chest, until the arms are close to full extension
-Slowly reverse the movement back to the start position
-Repeat for the desired number of repetitions