What's better: High reps with lighter weights or heavier weights with fewer reps?
As always, the answer is:
A recent study shows that when it comes to increasing your one rep maximum, it's better to focus on heavier weights and lower reps.
But when it comes to building muscle SIZE, the answers aren't so clear.
In the study "Effects of Low-Versus High-Load Resistance Training On Muscle Strength and Hypertrophy in Well-Trained Men", researchers set out to discover if there was an advantage to training with heavier or lighter weights.
Test subjects with previous weight training experience were split up into two groups.
Group 1: Trained 3x per week with a lower weights and higher reps. In short, they aimed for 25-35 reps per set.
Group 2: Trained 3x per week with heavier weights and lower reps. They aimed for 8-12 reps per set.
They all used the same exercises. Bench press, shoulder press, lat pulldown, cable row, barbell squat, leg press and leg extension.
Some of the results were unsurprising. For example, the group that trained with heavier weights saw a larger increase in their bench press 1 rep max. And the group that trained with lighter weights saw a better increase in the number of reps they could achieve using a weight equivalent to 50% of their 1 rep max.
But what IS surprising is that the heavy weight group saw a bigger increase in triceps size. Whereas the light weight/high rep group saw a bigger increase in biceps size. Of course, we're dealing with statistically insignificant increases here over a very short time period (8 weeks.)
So this isn't gospel. But it is enough to make you scratch your head. So if you're focusing on increasing your arm size, experiment with higher reps (25-35 reps per set) for your biceps exercises and lower reps (8-12 or even fewer reps) with heavier weight for your triceps exercises.
For more information on how to increase muscle size with lighter weight and higher reps, see this article:
Schoenfeld, et al. "Effects of Low- Versus High-Load Resistance Training on Muscle Strength and Hypertrophy in Well-Trained Men." Journal of Strength and Conditioning Research Publish Ahead of Print. DOI: 10.1519/JSC.0000000000000958