Original article written by Sanmy Nobrega, Maıra Scarpelli, Cintia Barcelos and colleagues
Background
Periodisation, training to failure, and prescriptive tables seem to stoke wild tribalism in strength and conditioning. I don’t quite know why either. Once at a conference in 2019, I saw a senior professor shouting at another researcher because they had questioned the concept of percentage-based training. Talk about entrenched opinions… and here I am thinking that researchers were after truth and evidence! Another topic that seems to promote fierce debate is the progression of resistance training and what is the best method (answer: it depends on the athlete/person). Furthermore, the use of repetition maximum (RM) zones is always going to be topical.
In this study, Nobrega et al., [1] investigated the effects of training to concentric failure with a set load (%RM group) compared to training with a RM zone (RM zone group), on changes in muscle strength and hypertrophy. Furthermore, differences in total training volume and the progression of these volumes were assessed. It should be acknowledged that these data were the combination of data from two different studies [2,3] and therefore was a ‘secondary analysis’.
What the authors did
Two different groups (from two different studies) that had trained the leg extension exercise were compared for changes in leg extension strength and vastus lateralise cross-sectional area (CSA). Both groups had completed 24 training sessions, with the %RM group training two times per week and the RM zone group training three times per week. Additionally, the %RM group trained to concentric failure with 80% of their 1RM and the RM zone group trained to concentric failure with a load that corresponded to their 9-12RM (which means that the load was constantly readjusted across the training period).
What the authors found
Following the training intervention, the RM zone group had significantly greater improvements in CSA. Furthermore, while not significant, improvements in 1RM strength in the RM zone group tended to be greater. These differences were accompanied by greater progression in the training volume in the RM zone group and greater absolute volumes (on average).
I will admit, I was a little surprised at the absolute and relative differences in CSA between groups. While it is common knowledge that training volume is probably the biggest contributor to muscle hypertrophy, these differences tend to disappear once training is taken to failure (this is even acknowledged in one of the studies with which a group is taken from [3]) [4,5]. Furthermore, protein synthesis responses are prolonged in untrained populations (which this study was made up of) [6], therefore I was expecting the group who had the greater absolute time (i.e., 12 weeks of training for the %RM group vs 8 weeks for the RM zone group) training to have greater absolute changes in CSA. But the results don’t only show that there were indeed differences, it shows that the group with less time training (although with the same number of training sessions) had greater absolute increases in CSA. This left me with the feeling that either 1) the progression of training volume indeed has a major influence on training adaptations, or 2) there’s something that is unique to one of the groups from the different studies that is influencing the outcomes.
Limitations
Overall, the authors have done a relatively nice job bringing two studies together to provide some form of comparison. From a researcher’s standpoint, it’s actually quite commendable that a single lab was so consistent in their methodologies that they felt that they were able to directly compare groups from different studies. Although, the help strengthen the current study, several considerations could have been included to further elaborate on the story that is provided. First, I would have liked to have seen whether there were differences in ratings of perceived exertion, monotony, or strain. Additionally, seeing whether there was some small difference in enjoyment would have been interesting. However, I will acknowledge that if they are indeed actually training to concentric failure for each set in each group, differences should have been minimal. Second, I would have been interested to see whether there was some type of nutritional differences between groups which influenced the outcomes. Even a simple dietary recall before and after may have been useful. Finally, it would have been great to see the authors calculate the statistical power for this study. Strength and conditioning researchers need to get away from simply saying “we had low numbers”, to saying “we’ve calculated how many participants we need and we either had it or we didn’t”. This is important for the continued growth and proper interpretations that are made within our field.
What this means for coaches
There’s a few pros and cons of this study which the practitioner should consider prior to taking and implanting its findings. First, this study suggests that in untrained populations, there may be some benefit of using an RM zone approach to progress load. This may help to keep the loads increasing, particularly when adaptations come thick and fast (e.g., with untrained individuals). Second, this study really emphasises the issues with fixed prescriptive percentage of RM loads (particularly in untrained participants). It’s common sense that people get stronger across a training programme and we need to account for this in our programming.
On the other hand, it should be noted that this study only used a single exercise, and that exercise was an isolation exercise (i.e., the leg extension). Consequently, trying to extrapolate some of these findings to larger training programmes is probably not untenable, particularly if you are asking your athletes to train to failure on each set using major lifts (e.g., squat, deadlift). Therefore, take these findings with a pinch of salt and perhaps consider the overall message rather than trying to directly take this training programme and apply it to your athletes.
Reviewer’s comments
I’ll be honest, I’m still a little surprised by the outcomes within this study. Seeing such substantial differences between groups in CSA, despite both training to failure, is still making me a little uncertain in the findings. While progression in training volume was linked to significant improvements in CSA, I wouldn’t have expected these responses between groups due to the expectation of both groups maximally recruiting motor units within the quadriceps during this exercise. Therefore, I’m still waiting on further evidence to convince me that one group would be better than another.
Recommended resources
Article – Training for muscular strength: Methods for monitoring and adjusting training intensity – Tim Suchomel and colleagues