I completely agree with the one set to failure protocol, however, something plays on my mind. I’ve always read and been lead to believe that a certain amount of muscle fibres contract maximally to lift a weight – as apposed to fewer muscle fibres all contracting sub maximally. Therefore when I’ve finished my one all out set to failure, I’ve stimulated those fibres that contracted maximally. If I was then to reduce the weight I could keep going which suggests there were fibres that were not used in the first set. Therefore one all-out set followed by a descending set would guarantee all fibres being stimulated. Then again, I don’t want to use anymore reps than necessary to trigger adaptation. Is a descending set or other set extension technique necessary for maximum muscle fiber recruitment?
A muscle fiber either contracts maximally or not at all. Muscle fibers are grouped into motor units of different sizes, and are recruited in order from the smallest to the largest depending on how much force the muscle needs to produce. During an exercise as some motor units fatigue and the combined force they are capable of producing decreases your body recruits more motor units to continue to produce the level of force required to overcome the resistance. As these newly recruited motor units fatigue more are recruited, until eventually every motor unit thus every fiber in the targeted muscles has been recruited. When you reach momentary muscular failure it means all of the motor units in the targeted muscles have been recruited and fatigued to the point where they are unable to produce the required level of force, and effectively stimulated to grow larger and stronger.
It is not necessary to extend the set by reducing the weight or performing other set-extension techniques like forced reps or negatives to recruit all of the motor units in the targeted muscles. Doing so just retraces the same motor unit recruitment pattern which increases the stress on your body without significantly improving the stimulus for muscular strength and size increases. The only time I use or recommend set-extension techniques is if a trainee falls a rep or two short of their lower target repetition number, and this is usually for the purpose of increasing metabolic stress or to help acclimate them to greater exertional discomfort so they can learn to continue to contract intensely despite the burn. Depending on the person and the exercise or equipment being used I may have them extend the set to reach a time under load equivalent to their lower target rep number by performing a static hold or timed static contraction instead. Isometric holds and rest-pause repetitions are often more practical set extenders when performing bodyweight exercises or when training alone.