You don't need a gym membership to unlock stiff joints — if you've been sitting for more than 3 hours, your spine needs this exercise

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The supine twist is a popular exercise for relieving tension in your spine and the muscles in your back. It involves lying on your back, drawing your knees toward your chest, then slowly, and with control, sweeping your legs to one side as you send your gaze in the opposite direction.For many, this move creates a gentle rinsing motion through the torso, and people credit the stretch with improving symptoms of sciatica. But, personally, I have never found a deep stretch from it. Until now.Enter the reverse supine twist. This take on the standard twist allows you to enter the stretch from your stomach — essentially a prone twist, but you'll end up in a very similar, if not the same, position.Here's how to do the reverse supine twist, the benefits, and a few tips for getting it right. One of the best yoga mats is useful to have on hand, too.How to do reverse supine twistsI’m keen to fit in "energy resets" during the day, but I don't always want to walk, so I like to unstick my joints and release tension by rolling out my yoga mat and taking a few stretches and mobility exercises through their paces. This is one of my essential go-tos.If you feel pain, stop. You could also try reducing your range of motion (how far you move into the stretch) or placing a block or cushion beneath your legs. If you have an injury, are returning to exercise, have a health condition, or are pregnant or post-partum, I strongly advise speaking with a medical professional first.Start on your stomach with your legs extendedExtend your right arm in front of you, palm down, then place your left arm beneath your body toward the right side of the room, palm facing upGently, and with control, sweep your right arm over to the left side of the room to create a twist through the upper bodyLook over your right shoulder. Focus on pressing both shoulders into the mat, even if that means your right knee hovers away from the mat. You could place something beneath your right knee. If your right knee can reach the mat, hold it there for a deeper stretchHold and breathe for 15-30 seconds, then slowly release and repeat on the other side. Try to initiate this stretch from the upper body rather than your legs or lower back.What are the benefits?Supine twists create rotation through the torso, which can relieve low back pain and tension held in the muscles surrounding and supporting your spine, especially around the mid-back.Get instant access to breaking news, the hottest reviews, great deals and helpful tips.Whether you sit for long hours, carry lots of stress, or lift heavy weights regularly, you might find your posture takes a hit over the years, so while posture-strengthening exercises are essential, so is relieving some of that pressure.When your posture is sound, your joints are stacked, creating stability and reducing muscular effort. When your alignment is off, perhaps due to slouching or hunching over, your posural muscles (especially those in your back) become weak or overworked, creating tension or aches.Proper posture practice and plenty of activity during the day can be helpful, along with resistance training and mobility exercises. The reverse supine twist can help many people reach a deeper stretch and better relief than approaching it from their backs, as you're initiating the twist with your upper body rather than swinging your legs to the side.Give it a try and let us know if you find it helps; we'd love to know!Follow Tom's Guide fitness on Instagram for more workouts, routines, tips, and tricks.