Can we “build muscle with light weights?”
This is the question that many people seem to assume they’ve found a definitive answer to in the past month. That’s because it was in April 2012 that the Journal of Applied Physiology published findings of a study that basically claims we can. The study showed that a ten-week comparison between lifting heavy weights for low repetitions and lifting light weights for high repetitions produced no difference in muscle mass gains. And ever since the fitness media discovered so much as the abstract to this study, they’ve fallen all over themselves to report it.
Whether this effusiveness of reporting is because the idea that we can ‘build muscle with light weights’ is “good for older people” – or that it’s just fun to ‘stick it’ to those muscle heads who insist on ‘mindlessly’ grunting with and slamming those heavy weights at the gym – is anyone’s guess. I just find it funny that many will unquestioningly take the results of any study that fits a template they favor and make uncritical generalizations based on findings of rather limited research.
Of course not; if I’m critical of a generalization made by this study’s findings, I’d be amiss in making my own generalizations in the other direction. I just think the study and accompanying question ‘can we “build muscle with light weights”’ deserve a bit more detailed analysis.
‘Build Muscle with Light Weight’: The research study
Let’s look at the basic structure of the study that’s become the conclusive evidence for so many that we can ‘build muscle with light weights.’
The experiment was done on eighteen healthy young men at McMaster University, Hamilton, Ontario, Canada. The subjects were all around 21 years of age (21 ± 0.8 years). The group averaged 1.76 meters in height (± 0.04 m) and 73.3 kg. in weight (± 1.4 kg.). The subjects were “recreationally active”, but had no formal weight lifting experience or regular weight-lifting activity over the year prior to the experiment.
The 10-week study was done using a unilateral protocol of weighted leg extensions. This means that each of the men’s legs was worked separately on a leg extension machine (“single-leg” leg extensions). The subjects were randomly assigned, in “counterbalance fashion”, to one of the three possible unilateral training conditions for each leg. The following were the three different conditions of weight volumes/set protocols that were performed three times per week for the 10-week period (1RM = single-repetition maximum):
- 80% of 1RM (1 set)
- 80% of 1RM (3 sets)
- 30% of 1RM (3 sets)
The researchers were performing this study as further investigation into their earlier findings that showed greater acute protein synthesis activity in muscles worked at higher volumes with lower loads than at lower volumes with higher loads. The abstract for that earlier study can be found right here. In that experiment, the only factor being measured was post-exercise protein synthesis; not measurements of muscle hypertrophy. But the findings of the study showed that training to failure with 30% of 1RM resulted in more post-workout protein synthesis, for a longer period, than did training with 90% of 1RM. This finding seemed worthy of further testing to determine if hypertrophy (muscle size) is affected. Thus, this latest study was more in direct alignment with determining if we can ‘build muscle with light weight’ as effectively (or more) as we can with heavier loads.
Before and after the 10-week study, the men’s leg muscles were measured using MRI (magnetic resonance imaging). In addition, muscle tissue biopsies were taken before the training began, after the first training session, and again at the end of the ten weeks. These muscle tissue samples were quantified using ATPase histochemistry and Western blotting analysis.
The performance strength of the men’s leg extension capabilities was also measured. Both before and after the training program, the researchers recorded the subject’s 1RM, maximal voluntary isometric contraction (MVC), rate of isometric force development (RFD), and ‘peak power’ output.
So what were the findings; is “building muscle with light weights” a go… or a no-go?
‘Build Muscle with Light Weights’: The study results
In essence, what did the researchers discover in the ‘build muscle with light weights’ versus heavy weights study?
In both thigh measurements and muscle biopsies, there was no statistical difference in hypertrophy between the muscles that were worked for three sets at 80% of 1RM and those worked for three sets at 30% of 1RM. However, there was a more than double degree of average muscle volume increase between each of those respective workout loads compared to the group of 80% of 1RM done for a single set. This suggests that training volume – at least in terms of ‘multiple sets’ versus a single set – might produce more muscle size.
Another major finding of the study was in the context of max strength gain. ‘Voluntary isotonic strength gains’ were significantly greater in the 80%-1 and 80%-3 groups than they were in the 30%-3 group. This was not so surprising to the researchers since it corroborates findings of earlier studies.
The study also bolstered earlier findings showing a possible connection between acute post-workout muscle protein synthesis and short-term muscle size gains. There was discernibly more protein synthesis activity among the two groups of muscles that were worked for three sets versus the 80% of 1RM worked for one set. Since those two groups obtained over double the muscle size of the single-set group, the connection between degree and longevity of post-workout protein synthesis activity and muscle volume increases seems clear.
What’s not so clear, in my opinion, is whether this means we can ‘build muscle with light weights’ beyond a relatively tiny 10-week period of time.
‘Build Muscle with Light Weights’: Only two ways to continue ‘overload’
Personally, I think this study’s findings are compelling, but hardly conclusive. The most glaring drawbacks are both its short duration and the inexperience of the subjects involved. Many experienced bodybuilders will regularly comment on the anecdotal observation that “rank beginners make progress on ANY workout routine.” Thus, one has to wonder whether the sameness in outcomes between workout weight-loads used in the study would remain beyond ten weeks, or even exist among just slightly more experienced bodybuilders.
During the study, subjects pushed their repetitions to the maximum and, apparently, increased workload only through increases in these repetitions. Obviously, there are only two methods of increasing volume workload on a muscle – by augmenting the workout weight or upping the repetitions performed with the current weight. If continued hypertrophy were desired beyond the 10-week study, an increase in resistance would eventually be required for all three weight-load groups. This raises a pertinent question:
Would there be a greater long-term capacity for resistance increases in either of the two 80% workload groups over the 30% workload groups?
If so, then I’d say that the “build muscle with light weights” rah-rah by the fitness media was premature.
If not… well, then “Yay-hey” for ‘building muscle with light weights’ – especially given its implications for reducing the risk of injury. But I’ll at least bet, based on experience, that even if this is the case, there’s probably a sweet spot somewhere between the 30% and 80% of 1RM loads that were used in the study.
Your opinions are encouraged and welcomed in the comment section.