Political polarization. Economic struggles. Inequity. Climate change. War. In a world like ours, you can hardly blame people for trying to cushion themselves. From weighted blankets to “cozy” murder mystery novels to restaurants based on childhood comfort foods, the appetite for comfortable things just keeps growing. Now some are seeking comfort even in their physical exertion. They are, it seems, entering the era of “cozy cardio,” an activity that lies right at the crossroads of gym workout, self-pampering evening … and nap time.