Answer:
When we are training muscular strength, our routines must have fewer sets with weight repetitions and low speed, because we want to reach the peak point of muscles and cause them stress, that way, after recovery, muscles will grow and support more pressure.
The opposite method is when we train for muscle toning or fat loss, in this case a higher number of sets is needed, and repetitions must be done faster.
Therefore, according to the National Health Service, a proper strength training program could include 8 to 12 repetitions with 2 sets, or 3 sets as much.