Building sexy muscle or losing body fat demands training your muscle with proper effort. People love to say that the 6-15 rep range is great for building muscle. But that is only if you train near failure within that rep range.
Imagine doing a set of 15 reps of bicep curls. Only you could have done 30 reps without stopping. Your set of 15 reps was only at about 50% effort.
The sad truth is that this won’t build muscle, but it is the way a lot of people are training out there.
We don’t promote pushing to failure all the time. But proper effort must be a priority in order get the correct stimulus for your muscles to grow. Think about trying to get within 3-5 reps from failure on all of your weight training sets. From time to time take it closer to 1-2 reps from failure. That is all you need to succeed.