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Bro Science Vs Published Science #2: Pre-Exhaust

Bro Science Vs Published Science #2: Pre-Exhaust

Who wins the fight on using pre-exhaust?

Written By Jim Stoppani, PhD

Updated May 7, 2024

Be sure to read the Introductory article on Bro Science vs Published Science for the background to this recurring department by clicking on the link below.

https://www.jimstoppani.com/home/articles/bro-science-vs-published-science-1

Topic: Pre-Exhaust

Bro science says: Pre-exhaust is a technique where you do single joint (isolation) exercises before multijoint exercises. For example, with chest you first do flyes or cable crossovers. Then you follow with multijoint exercises, such as barbell or dumbbell bench presses. The purpose of pre-exhaust is to ensure that the target muscle receives the maximum muscle growth stimulus during the multijoint exercise. Since mulitjoint exercises involve the help from other muscle groups – for the bench press the shoulders and triceps are also major players – the target muscle group often doesn't get adequately stressed. Often you reach muscle failure on a mulitjoint exercise when one of the smaller and weaker assistance muscle groups is fatigued and not when the target muscle group is truly fatigued. This can limit the muscle growth you get in that muscle. By doing pre-exhaust you exhaust the target muscle group, in this case the pecs, so it is the weak link on the mulitjoint exercise, and you truly end the set when the target muscle group is fatigued. This can help to increase muscle growth in that muscle.

Published science says: Two studies from two different labs have investigated the benefits of pre-exhaust, one looking at pre-exhaust in the quads and the other looking at pre-exhaust in the pecs. In the leg study, Swedish researchers had subjects do the multijoint exercise the leg press either before doing the single joint exercise the leg extension or after. In the chest study, Brazilian researchers had subjects do the bench press either before or after doing the single joint exercise the pec deck. In the leg study they reported that the muscle activity of the quadriceps muscle fibers when subjects did the leg press after the leg extensions (pre-exhaust) was significantly less than when they did the leg press first. The researchers in the chest study also found similar results. They reported that the muscle activity of the pecs was significantly less when they did the bench press after doing the pec deck (pre-exhaust) than when they did the bench press first. But research groups concluded that this proves that pre-exhaust does not work. They claim that this is because it did not increase muscle activity of the target muscle group during the multijoint exercise. Hold up! Pre-exhaust is NOT used to increase the muscle fiber activity of the target muscle group on the multijoint exercise! As the name implies, pre-exhaust is used to EXHAUST the target muscle group so that it's the weak link on the multijoint exercise. That way when you fail on the set, you know that you failed because you took that target muscle group to its ultimate limit. So despite the fact that the researchers actually proved that pre-exhaust works with this study because a fatigued muscle will have less muscle fiber activity, the researchers screwed up because they had no idea about what pre-exhaust is actually used for in the gym.

Winner: Bro science

Do this: Tell the pencil-necked scientists to leave the lab every once in a while and pick up a weight. Clearly they have no idea what pre-exhaust is and therefore should not be studying it in the lab! Your best strategy is to do multijoint exercises first in your workouts for the majority of workouts. This will allow you to use the most weight on the multijoint exercises so you can place more overload on your muscle fibers for greater growth. However, using pre-exhaust from time to time is a good technique to spur some new muscle growth.

References:

Augustsson, J., R. et al. Effect of pre-exhaustion exercise on lower-extremity muscle activation during a leg press exercise. J. Strength Cond. Res. 17(2):411–416, 2003.

Gentil, P., et al. Effects of exercise order on upper-body muscle activation and exercise performance. J. Strength Cond. Res. 21(4):1082–1086, 2007.