Long before Pilates teachers began reminding Americans to tone our abdominal, lower back, and pelvic muscles, Indian yogis created poses to strengthen them. Even though yoga seems to be everywhere these days, people who haven't tried it often don't realize how well it builds strength, not just flexibility. When I talk with one of these folks, I often think I should just ask him to try Paripurna Navasana (Full Boat Pose). He'd quickly discover how much it works his quadriceps, abdominals, back muscles, and hip flexors (the muscles that draw the front of the thigh and the front of the torso toward each other). Of course, he'd discover that Navasana requires a good bit of flexibility, too.
In Paripurna Navasana, your torso and legs form a V (like the prow of a boat when you look at it head-on). Your arms reach straight across toward your knees, parallel to the floor, like the deck of a ship on calm seas.
To sustain this V-shape, your muscles must hold the weight of your torso and legs up against the pull of gravity. Strength in your iliopsoas muscle, a hip flexor, is a key to resisting gravity in this pose. The psoas portion of the iliopsoas originates on the sides of the lumbar (lower back) vertebrae, and the iliacus portion originates on the inner bowl of the pelvis; together, they run across the floor of the pelvis and attach to the inner rear surface of the upper femur (thighbone). When the iliopsoas contracts, it pulls the thigh and torso closer together. Once you're in Paripurna Navasana, the muscle continues to contract isometrically, working but not changing length. It acts like a wire cable that runs between the two sides of a ship's hull, keeping them from bulging out.
Along with the iliopsoas, your abdominal and back muscles also contract strongly in Navasana. These sets of muscles work in opposition to each other, and ideally that work holds your torso in a straight line from hip to shoulder to ear in Paripurna Navasana.
To get a sense of how your abdominals work in this pose, sit toward the front edge of a chair, drawing your posture up straight. About two to three inches on either side of your navel, press your fingers into your abdomen. Then gradually lean your torso toward the back of the chair without touching it. You should feel your abdominal muscles contract to help your hip flexors hold your torso up against gravity.
Since the abdominals flex your spine, pulling the pubic bones and the front of the rib cage closer together, they will pull the torso into a C-shaped slump unless you oppose their action with your erector spinae, the long muscles that run up each side of the back, parallel to the spine. You have to engage your erector spinae strongly in order to cancel out the slump and create the straight torso position of Paripurna Navasana.
Finally, all four quadriceps muscles must work hard to straighten your knee. In Paripurna Navasana, the challenge to the quads is so intense that some practitioners may feel them cramping. You may need even more effort from your quadriceps if you have tight hamstrings, because the hamstrings directly oppose the actions you're trying to do with your quads. Here's where the primary flexibility challenge of the pose comes into play.
Test Your Hamstrings
To see how tight hamstrings can limit your Paripurna Navasana, try Supta Padangusthasana (Reclining Hand-to-Big-Toe Pose). Lie on your back, place a yoga belt across the sole of your right foot, and hold an end in each hand. Keeping your head, torso, and left leg flat on the floor and both legs straight, lift your right leg up toward the ceiling. If you can bring your leg past vertical and easily grasp your big toe while keeping your legs straight and your shoulders on the floor, your hamstrings won't hamper you in Paripurna Navasana. If you can't get your leg at least perpendicular to the floor while keeping proper alignment, your hamstrings are too tight to allow a 90-degree angle between your torso and legs in Paripurna Navasana—and the wider the angle, the harder you'll have to work your iliopsoas and your abs. In addition, tight hamstrings will pull on the base of your pelvis, tilting it back and forcing your erector spinae to work overtime to compensate.
Ease Into It
Regular practice of Supta Padangusthasana and other hamstring stretches will help your Paripurna Navasana. In the meantime, here's how you can work on the pose even with tight hamstrings.
Sit with your knees bent and your feet on the floor and draw your spine tall. Wrap your hands around the tops of your shins and pull in with your arms to help lift and broaden your chest. Sit up on your sitting bones, not rolled back onto your tailbone. Then, keeping your spine fully lengthened and your chest lifted, release the grip on your shins and stretch your arms out parallel to the floor. Reach strongly from shoulders to fingertips without rounding your shoulders; keep your shoulder blades moving down your back.
Next, start tipping your torso back and find a balance point—still on your sitting bones and with your knees bent and spine long, but now with your feet off the floor. Begin to straighten your legs, stopping and rebending them a bit if you feel your back start to round. This bent-leg version is a good way to practicing balancing in Paripurna Navasana while also strengthening the muscles you need for the pose.
Take the Challenge
If tight hamstrings aren't an issue, you may be able to practice Paripurna Navasana with straight legs—or you may have to work with them bent while you build strength. As you get stronger and more flexible, you'll eventually be able to straighten both knees so your toes are a bit higher than your eyes.
Once you can do that, try moving back and forth between Paripurna Navasana and Ardha Navasana (Half Boat Pose). For Ardha Navasana, keep your legs and torso about six to eight inches from the floor, clasp your hands behind your head, and let your spine come into some flexion. As you lift back into Paripurna, open your chest, draw your shoulder blades down your back, and fully lengthen your spine.
For the ultimate Boat challenge, start in Dandasana (Staff Pose), sitting with your legs straight out in front of you on the floor and your spine tall. You'll need open hamstrings to achieve the 90-degree leg-to-torso angle you worked on in Supta Padangusthasana. Keeping that angle, lift your legs and tip back so you're still on your sitting bones but now in a strong V-shaped Paripurna Navasana.
Practice a Navasana version a few times each week and you'll develop core strength that improves your posture and lets you sail through Full Boat Pose with ease.
A physical therapist and Iyengar Yoga teacher, Julie Gudmestad runs a physical therapy practice and yoga studio in Portland, Oregon.