You have been good, consistent and focused in keeping to your workout schedule but suddenly find that it just does not feel the same. You do not get DOMS. You are doing all the exercises right but don’t see incremental gains. This is the condition that I refer to as hitting a plateau in your workouts.
This is the stage where your body knows exactly what is expected of it and has optimized the neural circuits and motor units to precisely execute the predictable anticipated load. Over the last 8 months you have been able to increase your capacity and are now able to bench 80 pounds but it does nothing. You look the same.
Here are some methods to break the plateau. The first and easiest one is to take a couple of weeks off from workouts and give yourself a vacation. When you return, you will quickly pick up lost mass and potentially could break the plateau and get some incremental gains.
The other method is to switch to reverse sets. For example, when you are doing bicep curls, you can increase the weight you usually curl but while bringing down your arm, you do it very slowly and concentrate on the biceps. This will introduce a new experience to the body and stimulate gains and break the plateau. You can do this technique with exercises that involve a pulley or bar that you lift.
The other thing you could do is change your reps and sets using a pyramid or reverse pyramid that I have described in earlier posts. You start with your max weight that you can perform 12 reps with and then reduce two reps with each subsequent set and perform 4 sets. Alternatively you could go the other way and start with a heavier weight with which you can perform 6 reps, then reduce it by 5 pounds and perform 8 Reps and so on until you do the 4th set with 12 reps.
Another thing you could do is research isolation exercises for the muscles and find the ones that you do not regularly do. Use these exercises to replace the ones you regularly do for those muscles and you will instantly break the plateau. This effect can also be attained by finding exercises that attack the same muscles from an angle different from the ones that you usually do.