Should you add reps or weight or both to the bar when trying to maximize hypertrophy? When comparing two progression models, one prioritizing reps and the other one load, which one wins?

Overview

What did they test? The authors explored whether progressing reps versus load resulted in different increases in hypertrophy in untrained individuals. This was done by having one group train at a fixed % of their one-repetition maximum (1RM) while trying to reach failure on every set versus a group that performed 9-12 repetitions to failure and increased the load used whenever they exceeded that repetition range.
What did they find? Although both groups performed the same amount of working sets overall, the group that progressed by adding load experienced greater hypertrophy than the group that added reps over the course of the study.
What does it mean for you? Adopting a repetition-maximum progression model, where you use a predetermined repetition range (eg:9-12 repetitions), aim to reach failure and just add load whenever you manage to slightly exceed that range may be better for hypertrophy than trying to do as many repetitions as possible on a fixed %1RM load.

What’s the Problem?

When trying to make muscle gains aka increase muscle hypertrophy, training volume seems to be the main driver of adaptations 1. Studies investigating the dose response relationship between volume and hypertrophy have shown that although the majority of hypertrophic gains (roughly 65%) occur with just a handful of high intensity of effort sets, performing more volume, in the form of additional sets will lead to greater gains 1. The current literature suggests that in order to absolutely maximize hypertrophy, the optimal volume range lies somewhere between 10 to 20 sets per muscle group per week all performed at a close proximity to failure (0-3 repetitions in reserve) 2. Volume is traditionally defined as load x reps x sets, often referred to as “volume load”, something that comes with a few limitations baked “in”. The main limitation with conceptualizing volume as the total tonnage performed is that it does not account for intensity of effort and can thus be misleading.

For example:

Person A performs 10 sets of 10 reps at 20kg at 5-6 repetitions in reserve, meaning that the sets were very easy and somewhat away from the proximity to failure necessary to induce meaningful muscular adaptations (at least for trained individuals looking to grow more muscle).

Their total volume load is: 10x10x20 = 2000kg

Person B performs 5 sets of 8 reps at 30kg at 0-3 repetitions in reserve, meaning that their sets were actually quite hard, some even close or at their “limit” as far as having more reps left in the tank goes.

Their total volume load is: 5x8x30 = 1200kg

Although their volume load is 40% less than person A, the hard sets person B performed are more likely to lead to meaningful muscular adaptations, both for strength and hypertrophy and thus just looking at volume load becomes somewhat meaningless (at least in the context of muscle growth). Previous literature has looked at other ways of defining volume load while also including the intensity of effort used but a very easy way to think of volume for hypertrophy is number of hard sets over 5 repetitions. 

Another important variable in building muscle, aside from overall volume being high enough is progression aka making training somewhat harder over time. As a beginner even low training volumes at any rep range are enough to lead to significant muscle gains as you are literally starting from 0 from a stimulus-presented-to-your body standpoint. In the first few months, and in some cases year(s), of training, progression occurs almost “naturally” as you are experiencing rapid increases in strength and hypertrophy, with weekly increases of 5-20lbs on any given lift being totally normal. This phenomenon is also supported by studies exploring how strength changes over time with the first 1-2 years of training being where the biggest strength increases occur, with gains really slowing down after that point (even in powerlifters) 3 4.