Question

how to build muscle strength

Answer 1

Strength leads to size. Temporarily set aside your bodybuilding workout in exchange for this two-month strength phase, and watch your muscle gains soar!
Crack open an exercise-science textbook and you'll see that the optimal rep range for building muscle is 8-12 reps. But even if you're looking to build maximal muscle size, training for periods of time like a powerlifter—that is, training for strength—rather than a bodybuilder can have greater long-term benefits on muscle size. You may not want to build a powerlifter's physique, but having the strength of the strongest man in your gym is going to have some serious hypertrophic consequences.

You don't have to take my word for it. A number of top bodybuilders from yesterday and today—guys like Tom Platz, Franco Columbu, Ronnie Coleman, Ben White, Johnnie Jackson, Stan Efferding, and even Arnold Schwarzenegger—started their careers as powerlifters. These men first trained for strength before becoming bodybuilders.

Why does powerlifting training give you a long-term muscle-building advantage? The answer is simple: The stronger you are, the more weight you can lift.

Answer 2

Increase the weight, drop the reps. Moderate-rep sets are important when training for muscle size, which directly pumps up training volume. However, to build strength, you're going to have to train with heavier weights, meaning you'll do fewer reps. Your first exercise of each training day is your main lift.