Slowing down reps for growth?

Hey T-dudes, I was just wondering if slowng down a rep by like one or two seconds on the concentric contraction would be effective for building muscle size.Basically i ask this because on exercises such as the side sit up,pull ups,etc
i find it much more difficult to hold weights when doing them.
So would this be effective or is it comparable to doing lots of reps in terms of muscle-building effectiveness?
Thanks for your help

The eccentric is what’s important, not concentric (for the most part from a hypertrophy perspective). Read TC’s current article on the topic.