Food and Health Rethought

You actually can get large muscles from lifting light weights. Here’s how:

It turns out that lifting a weight that’s 90% of the maximum weight you can lift until you can’t lift any more (failure) is less effective at muscle building than lifting a weight that’s 30% of the maximum weight you can lift until you can’t life any more (failure). It turns out you lift the lighter weight a lot more times and that builds more muscle. here is that study: via

We report for the first time that low-load high volume resistance exercise (30FAIL) is more effective at increasing muscle protein synthesis than high-load low volume resistance exercise (90FAIL). Specifically, the 30FAIL protocol induced similar increases in MYO protein synthesis to that induced by the 90FAIL protocol at 4 h post-exercise but this response was sustained at 24 h only in 30FAIL. …  There were three groups: 90% 1RM to failure (90FAIL), 30% 1RM which matched the external work to the 90FAIL group (30WM), and 30% 1RM to failure (30FAIL). 

The fact is that most people when lifting a light weight don’t lift it enough times to reach failure, so that’s probably why this study is a bit counter intuitive.
The reality is if you push yourself to near failure any weight and rep combination, you’ll likely get results.