A Generalized Resistance Resource like Antonovsky describes it can only be something you had experienced. Yes, it can be fitness and good nutrition, when you learned it and it is now your resource. It depends strongly on your experiences as a child.

May I add a view from Chinese medicine? In Chinese medicine, if the spleen is not healthy, nutrition absorption rate is low. western exercises cannot activate the spleen function except the Chinese exercise (qigong) or get Chinese medicine treatments of acupuncture, herbs, magnet therapy or the whole body healing system,

https://universaltcm.com/the-differences-between-chinese-exercises-and-western-exercises-chart/

https://universaltcm.com/the-chinese-vs-western-exercises/

http://universalenergyhealing.us/whole-body-healing-system/