Repeated bout effect misunderstandings

Currently, there is a tendency to say that the repeated bout effect (RBE) means that well-trained lifters do not need to worry about the various negative effects of muscle damage (and calcium ion-related fatigue in general) when doing stretched-position exercises or high workout volumes. This completely misunderstands the meaning of the term RBE.

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#1. What is the repeated bout effect (RBE)?

The RBE refers to the reduction in post-workout fatigue that occurs from an initial workout to a second workout (as a result of adaptations in resistance to calcium ion accumulation). Using it to refer to anything beyond that point is not correct. Anyone who has performed at least one workout has achieved some sort of RBE for that muscle group. So beginners, intermediate lifters, and advanced lifters have all got exactly the same RBE. Yes, I know that internet commentators do not use the term in the same way. But they are using the terminology wrongly (read more).

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#2. What is the multiple repeated bout effect (multiple RBE)?

The multiple RBE is what internet commentators really mean when they refer to the RBE. It describes the reduction in post-workout fatigue that occurs from the second workout to third, fourth, fifth and even sixth workouts (again, as a result of adaptations in resistance to calcium ion accumulation). Importantly, the multiple RBE is tiny compared to the RBE. Therefore, we would not expect advanced lifters to display substantially better recovery from a standardized workout in comparison to an intermediate lifter, and we would not expect an advanced lifter to be magically immune to the calcium ion-related fatigue produced by stretched position exercises (read more).

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#3. Are advanced lifters in fact MORE susceptible to calcium ion-related fatigue?

Advanced lifters may in fact be more susceptible to post-workout fatigue through calcium ion accumulation than intermediate lifters and beginners because of their higher levels of motor unit recruitment and their greater sensitivity to the post-workout inflammatory response (read more).

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Conclusions

Fitness industry commentators often state that the repeated bout effect (RBE) makes fatigue during and after workouts less of a problem for advanced lifters. Such problems include [1] the diminishing effects of greater workout volumes (later sets in the workout create a smaller hypertrophy stimulus by reducing mechanical tension), [2] the very muscle-damaging effects of stretched-position exercises increasing the length of post-workout recovery periods, and [3] the interference effect produced by previous workouts on later workouts due to muscle damage and the central nervous system fatigue created by the associated inflammatory response. Yet, the RBE does NOT remove these problems because it only refers to a change from the first workout for a muscle to the second workout for the same muscle. In other words, beginners who have done at least one workout, intermediate lifters, and advanced lifters will all have achieved the exact same RBE. The "multiple RBE effect" is the phenomenon that refers to changes from the second workout onwards. This involves basically the same adaptations as the RBE itself but the changes are EXTREMELY small in magnitude and after 3-4 workouts they are essentially negligible. Therefore, it is not correct to state that advanced lifters are much more resistant to the problems of calcium ion-related fatigue, whether within the workout itself or from one workout to the next. In fact, since they have the ability to achieve higher levels of motor unit recruitment and thereby access more fast twitch muscle fibers, they are most likely much more susceptible to the problems produced by calcium ion accumulation.​