In case you’re confused, there’s a faction of the bodybuilding community that lives by the “training obliques makes your waistline bigger” code. I never really bought into it, at worst there’d be a marginal change and I’m not even too convinced of that. Better performance, especially athletically, and better oblique definition when your body fat is low are two solid reasons to train these core muscles. And if your paranoia about a wider waist still exists.. try high reps and you’ll be just fine.