This is adapted from the 6-12-25 protocol, which you can read about in full detail here. Whilst both 6-12-25 and 8-12-15 are fine to use, you may preference one over the other dependent on the type of trainer you are.
JE and Richie Brew love themselves an upper body 6-12-25 workout, whereas I prefer 8-12-15, or even 8-12-20 and sometimes 8-10-12. Admittedly, 6-12-25 has its benefits, but ultimately it is a very high volume, time-efficient way of hitting a muscle group, or complimentary muscle groups. However, the idea that it effectively straddles power, strength, hypertrophy and volume/endurance work is questionable.
I would opt for this kind of training to replace volume/higher rep work, or even hypertophy when short of time, and feel that the supposed GH release, and most certainly the lactate build up, would be markedly similar between both 6-12-25 and 8-12-15.
Why I prefer 8-12-15:
This causes you to lighten the load slightly, which will hopefully allow more emphasis to be placed on form and leave you in better condition to complete the following 2 exercises.
8 reps at a slightly lighter load will also accumulate to more total volume on the (most-beneficial) compound lift vs. 6 reps (weight x reps x sets = total volume).
Same rep range as 6-12-25 here so no real justification is required. However, 10-12 reps is a very common target for most trainers, so not as taxing an effort (mentally at least) arguably, compared to heavier/lower rep ranges or very high rep targets.
Perhaps not a massively high rep range, but with the accumulated volume (20 reps on a single muscle group) and the pain that goes with it, 15 reps is a feasible target in which to use a decent weight, maintain form and really push yourself!
25 reps is a very big target, and hard to select the right weight for or to maintain technique during. My clients and I have found 15 reps to be far easier to judge, and work to effectively as a target.
Chest; Bench Press, Incline Press Ups, Dumbbell Flyes
Back; Lat Pull Down, Face Pulls, Lat Push Downs
Shoulders; Dumbbell Press, Dumbbell Upright Rows, Bus Drivers
Biceps; Barbell Curls, Hammer Curls, Plate Curls
Triceps; Skull Crushers, Bench Dips, Kickbacks
Legs; Leg Press, Sumo Leg Press, Kettle Bell Swings
Quads; Narrow Leg Press, Goblet Squats, Jump Squats
Hamstrings; Stiff Leg Deads, Romanian Deads, Feet Raised Bridges
Glutes; Sumo Leg Press, Sumo Goblet Squats, Kettle Bell Swings
See various 8-12-15 and 6-12-25 workouts in our Facebook Video Archives here.