You gotta go with heavy weights for gains, bro! No, you gotta go high reps for gains, bro! Bro! You may have heard this argument before (maybe it played out slightly differently), or were curious which one was best for your routine. There are certainly recommendations for both, with programs like Westside, Starting Strength etc. preferring to load the weight on while routines like German Volume Training push the volume to extreme levels. So which one is good for you if you are looking to gain muscle? Turns out, either will do.
A recent study confirmed the fact that using high weight loads or high reps with low weights lead to similar results when the goal is to gain muscle. The authors of the study put untrained men into four groups, repetition to failure with low load (LL-RF), repetitions to failure with high load (HL-RF), repetitions not to failure with low load (LL-RNF), and repetitions not to failure with high load (HL-RNF). The high load group used 80% of 1RM (one rep max), and the low load used 30% of 1RM. To translate, if your bench is 300, the high load group was benching 240 to failure and the low load was benching 90 to failure.
The weight load between the failure groups was significant, but the muscle gains were the same; how? We have mentioned that time under tension is one of the most important factors to stimulate muscle growth, and this study confirms that, but something that it adds is that you ultimately have to tax your muscles to the point of failure. Failure shouldn’t be your goal, but you should feel like you have very little left in the tank. If that happens, then the amount of weight you are lifting doesn’t matter, your body will adapt to lift that weight more effectively, which means it will gain muscle.
If your goal is to gain muscle, then it seems that you have options. Either heavy weight or high reps will get you to look better in the mirror, as long as your workouts are pushing you to the point of failure. The groups that did not go to failure did not make significant gains in this area. However, if your goal is to get stronger, heavy weight is still your best bet, but for now, the bro argument about mass can be put to rest.