The tendency of many macho guys to brush off pain from serious injuries in day-to-day life, while behaving like complete blubbering weenies when receiving routine medical care. This allows them to appear to have a (manly) high pain threshold, and yet still get copious sympathy from loved ones at the hospital.
Jenna's husband didn't flinch when he sliced his hand open while renovating their kitchen. But he sobbed inconsolably when they put in an IV at the ER. Jenna coddled him and yelled at the nurse, but it was a clear case of Action Hero Pain Syndrome.