Time for the next virtue! For purposes of this, I'm considering "strength" and "prowess" to essentially be the same thing. Prowess of course has always been one of the most important of the knightly virtues. A knight who gets killed on his first skirmish isn't much use in the long run, for instance.
Geffroi de Charney, in his book of knighthood, spends an enormous amount of time on ranking "men of worth" by how much worth they have. Obviously prowess factors into this greatly, but also what men
choose to do. For instance, a successful knight of war is more worthy than one who only does tournaments, even though both are "men of worth". (and remember, in his time, tournaments were not sport or games as we know them, but rather full battles, though the evolution had already begun I think).
In a modern context, obviously we have less use for skill with the sword, horse, or lance. It's unlikely that we'll get mugged in a dark alley and only have a full jousting kit at hand.
So I think we need to think of strength and prowess in broader terms. I think of it as a desire to excel in whatever undertakings you choose. To be good at your job, and not do anything half-assed if you can help it.
What do you think?