Most CrossFitters want to be stronger, and could probably stand to be stronger too. There's only so strong you can get through traditional CrossFit programming. Most days you'll see a strength component between 1-5 reps and a metabolic component with 90 reps or more. This is fantastic for overall fitness, but if you have hit a plateau on your strength gains, it may be time to add in some targeted hypertrophy work.
There are three basic types of strength training, maximal strength, strength endurance, and hypertrophy. Yes I know there are more, but today we are going to keep it simple for today.
Maximal strength is just like it sounds. The goal is to lift the largest weight that a muscle will allow. Typically it is trained using 1-5 rep sets with 85 - 100% of 1 rep max. Maximal strength training trains the nervous system to be more efficient when firing muscles and motor units, but doesn't necessarily create a larger muscle.
Strength endurance training is a CrossFit staple. It involves completing numerous reps of a single or multiple movements. It improves the work capacity and ability of muscles, but doesn't create an appreciable increase in muscle mass. A workout such as "Cindy" - 20 minutes 5 pull ups, 10 push ups, 15 squats, trains strength endurance as a typical score is over 500 reps.
The last type of training is hypertrophy. This is designed to increase muscle mass and overall size. It's done with submaximal weights in reps that bring you to near failure. Usually it will be sets of 10-15 reps with the last 2 reps being extremely difficult to complete. This type of training will create muscle adaptation designed to grow the muscle.
Because in CrossFit we generally train maximal strength and strength endurance, we tend to reach an upper limit of how much weight we can lift. Once we've trained the nervous system to max out our 1-5 rep lifts, we have a hard time lifting much heavier without adding more muscle mass.
There's a reason that people who weigh more tend to lift more, they have more muscle mass to move the weight. The 77 KG lifters at the Olympics didn't lift as much as the 105+ guys.
So, back to the main point. If you have reached a plateau in strength gains, some targeted hypertrophy work can help you break through. 3 sets of 12-15 reps with a controlled time under tension a couple times per week can do the trick.
If your squat is struggling, drop the weight and do 3 x 15 a few days a week, yes your legs will get bigger, then we can train them to fire efficiently and lift heavier weight. Same goes for presses, pulls, etc. Add a little bit of muscle mass and the strength will improve as well.