Most experienced strength trainers will tell you if you want to gain size then you need to employ higher reps (i.e. 10-12), whereas if strength gain is your primary goal then you need to be lifting more in the low rep range (i.e. 3-6).
Weight Training History
But one criticism of the studies used to form these views is many included subjects that didn’t have an extensive history of weight training. For example, studies have used previously untrained and even moderately trained populations. But the authors of this latest study argue that untrained individuals respond favourably to a wide range of training stimuli. However, this response diminishes rapidly during long-term resistance training and therefore, more scientific recommendations are needed to properly address program design in trained populations targeting strength and hypertrophy increases.
Effect of Prior Training Program
The other key criticism these authors make is that many previous studies have failed to account for the prior weight training habits of participants. For example, if participants were following a similar type of program to the one used in a given study, then one would expect fewer improvements. However, if participants were training using a very different type of program compared to the one used in the study then the change in stimulus could lead to improvements and hyper inflate the efficacy of the program.
In total, 29 subjects who had been resistance training for a minimum of two years were recruited and then randomly allocated to either the high intensity (low volume) group or high volume (moderate intensity) group. The details of each training regime are shown below as well as the types of exercises that were employed.
All participants described their training habits to be different from the training program used in the study (in terms of exercise order and how the exercises were grouped). This was important; as highlighted above, the researchers were trying to control for the effect of program habituation.
Mechanical vs Metabolic Stress
By comparing a ‘volume’-based protocol with an ‘intensity’-based protocol, the researchers were trying to assess the relative effect of metabolic stress (i.e. volume program) versus mechanical stress (i.e. intensity program) on muscle hypertrophy and strength.
The authors also completed a series of hormonal measures at the beginning and end of the study. By measuring common anabolic hormones such as growth hormone, insulin, insulin-like growth factor-1 and testosterone, the researchers could measure how changes in hormone levels correlated with change in muscle strength and size.
Running over 8 weeks, the key findings to emerge from the study were that the low-volume resistance training utilising long rest intervals stimulated significantly greater 1RM bench press and lean arm mass gains compared to moderate intensity, high-volume program utilizing short rest intervals in resistance-trained men.
To some extent, this is what the researchers were expecting, but the most novel finding to emerge from the study were the greater gains in some measures of muscle size observed in the intensity group. This came as somewhat of a surprise as high-volume (rather than high-intensity) training has traditionally been thought to provide the best stimulus for muscle hypertrophy. But the key difference with this study was the training status of the subjects, who on average had been strength training for 5.7 years!
As far as hormone measures were concerned, at week 3 of the study, growth hormone and cortisol were greater for the volume group. But by week 8, both growth hormone and cortisol had tapered off, with the cortisol levels still remaining significantly higher. The authors theorised that this might reflect an adverse effect of the increased load in the volume group.
As for differences in IGF-1, insulin and testosterone, these rose in both groups (as expected), but there were no significant differences that stood out between the two groups.
The key takeaways from the study apply to individuals who have been hitting the weights for years. Based on the results of this clever study, It seems that if you’ve been pumping iron for years using a traditional high volume (moderate intensity) type program with repetitions in the range of 10-12, it may pay to divvy up your routine a bit with some lower rep (i.e. 3-5) and high intensity (i.e. ~90% 1RM) training.
The other key paradigm this study challenged was the notion that higher growth hormone levels automatically mean more strength and bigger size. It would seem that it is the balance of opposing hormones such as growth hormone and cortisol that ultimately determine gains in strength and mass.
So what have you got to lose if you’ve been weight training for years and struggling to make new gains? Why not through in some heavy sets for a few weeks and see how the muscles respond!
Mangine GT, et al. The effect of training volume and intensity on improvements in muscular strength and size in resistance-trained men. Physiological Reports. 2015;3(8):e12472.