Week three of Super Strength has you doing prefatigue before sets of 10. Can anyone tell me what biological effect prefatigue has on training? Is it the same benefit of forced reps, but at lower risk (less weight)? Is it lactic threshold? Please.

I hate to bump. Someone’s read his book, right? Please, just a quick answer. Feed my brain.

Just do it.

I don’t believe it has anything to do with ‘biological effects’, as in biochemical. As far as I know there are two interpretations of pre-fatigue. One says that if you do an isolation exercise e.g. flyers before a compound exercise, let’s say the bench press, the secondary muscle groups have to work harder in the compound exercise since the main muscle group is already exhausted and the secondaries have to make up for that. The other interpretation says that, since the main muscle group is already fatigued, this muscle group will be the weak link in the compound exercise and therefor will have to work harder. The secondary muscle groups, since they are not fatigued and are exposed to a less-than-normal load have to work less. Obviously both interpretations are total opposites.
Reading his super strenght articles in T-Mag Ian King seems to favor the first interpretation.

Specific Adaption man. You’re training your body to readjust it’s priorities. Instead of training to handle fresh 1 rep maxes you are instead training to bench more for more reps in a local muscle fatiqued state. As far as hypertrophy I don’t see why it would help much. Since you’ve caused a lactic Acid buildup (which will hamper the ability to forcibley contract) on a inferior isolation exercise you will now be weaker when you move to the compound exercise. The heavy compound exercise is the one that recruits the most muscle fiber and causes the greatest hormonal response. So, why would you want to hamper the weight used by causing lactic Acid buildup with an inferior exercise?

Per Ian King in ‘Get Buffed’, the goal of super-sets or pre-fatigue (seen in phase III of Super Strenth by combining a single-joint exercise followed immediately by a multi-joint exercise) is “to cause total fatigue in the area being trained.” Basically, it is a great method to increase TUT.
Ian also states that pre-fatigue methods can be used to limit the load in the multi-joint movement “due to the presence or risk of injury or poor technique.”