I remember a conversation I had with this wonderfully strong and competent climber I have the pleasure of knowing. She and her husband would allow my partner and I to stay in their home while we offered our training program at the gym they trained and worked in. This climber also happened to have past experience as a ballerina, having performed and taught at a high level before settling into family and teaching. In one of our many conversations about what makes someone a great rock climber, she explained how in ballet, the top schools could tell from a candidates anatomy whether they would make it in the world of ballet. 

At the time, I was completing my masters in kinesiology. My research was focused on determining the physical characteristics of elite sport climbers. I had collected data on grip strength, back and shoulder strength, flexibility, core strength and body fat. 

In the many years since that early research - before bouldering became a sport in it's own right - I have changed my idea about what makes one great. 
In my view, teachability and GRIT will make or break one's career as an athlete. 
Or, defined another way, one's curiosity and willingness to learn and apply, combined with the willingness to be uncomfortable, willingness to fail and willingness to persist.

Angela Duckworth states, "grit is passion and sustained persistence applied toward long-term achievement, with no particular concern for rewards or recognition along the way.
Grit requires courage, conscientiousness,  resilience, persistence and passion.