Think treadmills are the ultimate home gym staple? Think again. Rowing machines deliver a joint-friendly, low-impact workout that packs just as much punch, according to Melissa Prestipino, doctor of physical therapy, certified personal trainer and owner of Maize & Blue Rehab in New Jersey. Rowing is a cardio powerhouse, but it's also a full-body workout that engages every major muscle group. Prestipino explains that rowing activates your arms, legs, core and back, builds strength and improves...