Some explain it through physiological conditions, where 6 to 15 reps elicit the greatest stimulation of sarcoplasmic and myofibrillar hypertrophy, the two different types of muscle growth.
On an echocardiogram, a pericardial effusion makes the heart look like it's dancing within the pericardium, whereas chronic pericarditis shows the stiff serous pericardium restricting the heart's movement.
Wherever we seem to look though, the data makes it abundantly clear that there is no clear physiological hypertrophy advantage to any specific rep range.
During the follicular phase of the menstrual cycle, the endometrium thickens in case fertilization occurs, during the luteal phase, spiral arteries emerge to bring more nutrients to support the thick endometrium.
Growth rings are thickening of the bone that indicates periods of time when the dinosaurs weren't rapidly growing. These growth rings are evidence that dinosaurs stopped growing or grew more slowly during cooler periods.
A group of scientists once presumed that five genetic variants caused a dangerous thickening of the heart, even going so far as to tell people with those variants that their DNA put them at risk for cardiac troubles.