It looks like an oversized inner tube is trying to swallow a treadmill—not to mention the runner—but the AlterG antigravity treadmill has become the decisive exercise tool for rehab centers, pro athletes and home-gym enthusiasts. Originally developed by NASA scientists to nullify the bone-wasting effects of zero Gs, the treadmill’s vacuums create positive buoyancy for training at 20 to 100 percent of body weight and stress reduction on joints and muscles. It also addresses any issues involving mobility and balance to prevent injury. $35,000 to $70,000. Visit the contact page at alterg.com to schedule a local demo.