Most bodybuilders like myself Tom and even most exercise physiologists would agree that workouts that produce maximum pump can provide up to  20-25% of the increase in muscle size .  In his book, The Encyclopedia of Modern Bodybuilding, Arnold Schwarzenegger pointed out another benefit of the pump, the psychological effect. It feels good and is very satisfying to watch your muscles swell up and see the veins bulge right before your eyes in a matter of minutes. 

Arnold wrote, “ When you are pumped up, you feel better and stronger, and it’s easier to motivate yourself to train hard and achieve a high level of intensity. Sometimes you will walk into the gym and feel tired and lazy but you will get a fantastic pump after a few minutes of work and suddenly feel strong and energetic.” 

As important the pump might be for bodybuilders, the criteria that’s  MUCH, MUCH more important  than pump is  PROGRESSIVE OVERLOAD. Nothing is more important in bodybuilding or strength training than progressive overload. This means you must beat your previous workouts and increase the amount of weight you use in a slow, steady and systematic fashion. 

Remember something Tom, you can get a pump by dropping down on the floor and doing a few sets of push ups, but that doesn’t mean you are going to get permanent gains in muscle size.Some of the best gains I have ever achieved came from combining heavy strength workouts using a 8-6 rep max on basic exercises, with maximum pumping methods such as supersets, short rest intervals and medium-high reps. 

I also believe that pump workouts combined with strength workouts give the muscles a more “polished” look than low rep strength workouts alone. High rep workouts alone do little more than flush blood into the area worked and contrary to popular belief, high reps do NOT get you “ripped.” The “ripped” look is mostly a matter of low body fat, but if body composition is equal, the trainee who has done both types of training will usually have a more “finished” look to his or her physique than the trainee who only does low reps with heavy weight. If you look at powerlifters and strongmen, you’ll notice that even the ones with low body fat lack the polished look that competitive bodybuilders possess. 

So bottom line Tom don’t measure your workout effectiveness based on pump. Focus on heavy weight and progressive overload and you will be sure to get the results your after .