Tom Venuto argues the merits of the “the pump” in body building: Is ‘THE PUMP’ Necessary for Muscle Growth?

The pump is the short-term sensation you get during training when your muscles fill up with blood faster than the blood can leave the area, making the muscles appear fuller and larger. It’s a tight, swelled feeling, often accompanied by an increase in vascularity.

Basically he says that for physique-orientated weight lifters the pump is very important, but it is less important for strength training.

The pump usually results from superset workouts or lifting with very brief rest intervals between sets. A superset is an advanced training method in which you do two exercises, one after that other, with no rest in between. This can be done with two different muscle groups, but for a good pump it would focus on only one muscle group.

Most bodybuilders 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. This comes from sarcoplasmic and mitochondrial hypertrophy and increased capillarization. Sarcoplasmic hypertrophy looks good and is beneficial to bodybuilders, but you do tend to lose it more quickly with de-training.

The pump has virtually nothing to do with increased myofibrillar hypertrophy – the actual fiber growth that’s responsible for 75-80% of the increase in muscle size. That type of fiber growth comes only from heavy training, which produces much less, if any pump.

Tom also mentions the psychological benefits of the pump, referencing Arnold Schwarzenegger’s book The Encyclopedia of Modern Bodybuilding. 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.

Even if you realize that the pump is only temporary while your muscles are gorged with blood, it can still be very motivating to see your muscles swollen to their max.