Physical Fitness is important, and probably - if we knew the lifestyles and eating habits of many of the people on this forum, they are statistically more likely to die of cardiac arrest than ever be acosted let alone killed by a criminal, yet they'll spend thousands of dollars on firearms under the pretense of it being for survival and self-protection, but they won't exercise, or stop eating the bacon cheeseburgers.
On the other hand, the firearm is the great equalizer, giving a frail old woman the ability to defend herself from the even the most physically fit young, would-be mugger. Meaning, she doesn't have to out-wrestle or duke it out with an 18 year old homocidal maniac, she just has to deploy her firearm and shoot him.
Yes there are circumstances that govern any situation, a frail old woman is not going to be able to deploy her firearm easily if the mugger already has her in his clutches.
One of the reasons physical fitness is important to me is that it improves my grip, stance, helps me maintain better sight picture and sight alignment longer, and just generally improves my performance. I also can shoot well for longer periods of time without getting fatigued.