I want to highlight the article for the way in which it is good science. The author doesn't simply look at one or two studies that may support his thesis. Instead he looked up as many studies specific to the question as he could find. The article then summarizes the findings of these 10 studies. Strong conclusions cannot be made from a single study, replication is a key to proper science.
The Results?The ten studies compared heavy (1-5 RM) with moderate (6-15 RM) and/or light (15+ RM) loads, as well as lower reps done very slowly which require lower weight. Of the 10 studies, 3 found that heavy training produces more increase in muscle size. The other 7 were equivocal, with no particular weight category providing superior results.
The evidence that training heavy provides superior muscle size growth is weak but still slanted towards the thesis being correct.
All of the studies were limited by being relatively short, most were only a few months. And by using only untrained athletes. Other research already establishes the expectation that almost any resistance training will produce a reasonably broad response from the subjects. That is, any of the load categories would be expected to produce at least modest gains in size, as well as absolute strength, muscular endurance and similar measures.
However, once an athlete moves past this initial training period specificity starts to matter much more. In the long-term heavy training is needed to maintain gaining in strength or high-reps for endurance. The present studies have not addressed trained athletes or long-term training. So our conclusions must be limited.
Frankly, I would not expect that lifting heavy is actually the best strategy when measuring hypertrophy alone. It's not what bodybuilders do to win their competitions after all. Real strength training is not the same as bodybuilding.
Emphasis on Hypertrophy?The other half, of course, is do we need to emphasize hypertrophy? Increases in muscle strength, for an individual muscle, results from two factors alone: 1) the cross-sectional area of the muscle, and; 2) the neural coordination of the many motor units in the muscle. Obviously, in discussing fighting with all our strength we are not only concerned with each muscle's strength, we are concerned with focusing our entire body into the strike. Hence the need for strength training with large compound movements like squats and Olympic lifts.
That being said, muscle growth is clearly useful for our purposes. It is one of the elements to maximizing our strength. Furthermore, since we practice a contact sport muscle mass is useful for it's ability to absorb hits with minimal detriment.