This article is rubbish. REAL gym attire:

Many trainers recommend Chucks specifically for squats. They're fine. If someone can't wear Chucks while squatting, it probably means they're a) leaning forward and/or b) not going down far enough. Basically it means their squats suck.

There is zero problem with Chucks at the gym. None what so ever.

Consider doing deadlifts instead of crunches. They're much more efficient!

1. Spotters- look around you; if you see someone taking a break, ask them if they can spot you quick. The vast majority of people are happy to oblige. Men or women, it doesn't matter.