Muscle fiber activation unaffected by load/repetition

When training to muscle failure.
https://physoc.onlinelibrary.wiley.com/doi/abs/10.1113/JP278056

Recent study showed no difference in anabolic signaling or glucose depletion in type I or type II fibers while lifting to failure with either light or heavy loads. Even though there were significant differences in surface EMG amplitude between the two types of RE.

This supports a growing body of evidence that indicates that:
A) if you are lifting to failure, and total load volume is similar, there is no difference in muscle hypertrophy whether using lighter or heavier weights

If lifting to failure, Type II fibers will be activated by lower weights.

C) Surface EMG readings have limited value when determining actual muscle work.

I am not sure in this study how they determined “light” and “heavy”.

One note: this evidence does not mean that “light weights” means “easy”. Working to failure with lighter weights (eg 20 reps) is arguably much “harder” than maxing out in 2-4 reps because of the longer time under tension.