One of the things I've noticed with people trying to do a 5 X 5 program is a tendency to try incorporate exercises that can be done high rep into this kind of workout scheme. The 5 x 5 routine is designed to be a strength building program and though I can't be sure he was the first to do it, it was made popular by Bill Starr's "The Strongest Shall Survive: Strength Training for Football", written in 1976. The original routine made use of the "Big Three" exercises: Bench Press, Squats, and Power Cleans. There have been several variations of the routine, and sometimes Deadlifts are substituted for Power Cleans. Here is an example of Starr's Beginner Routine:
Bill Starr’s Beginner 5×5
Monday (Heavy Day – 85%)
Back Squats: 5 x 5 Ramping weight to top set of 5 reps across 5 sets
Bench Press: 5 x 5 Ramping weight to top set of 5 reps across 5 sets
Deadlifts: 5 x 5 Ramping weight to top set of 5 reps across 5 sets
Wednesday (Light Day – 65-70%)
Back Squats: 5 x 5 using 60% of Monday’s weight
Bench Press: 5 x 5 using 60% of Monday’s weight
Pullups: 5 x 5 Ramping weight to top set of 5 reps across 5 sets
Friday (Medium Day – 70-85%)
Back Squats: 5 x 5 using 80% of Monday’s weight
Bench Press: 5 x 5 using 80% of Monday’s weight
Rows: 5 x 5 Ramping weight to top set of 5 reps across 5 sets
One thing to keep in mind using 5 x 5 routines is that all 5 reps should be smooth and high quality. You don't want to lift so heavy that it is a struggle to get the weight up. You also don't want to lift so light that you can end up doing 10 reps. This usually means working at about 80% of your one rep maximum for that particular exercise.
As I also mentioned above, where I see people running into problems is they try to apply the 5 x 5 to exercises that are typically assistance exercises - lateral raises, chest flyes, bicep curls. Using such a heavy weight for these exercises is asking for an injury.
