Let's have a look at the Janusirasana or head-to-knee pose.
Sit it down on your mat. Start with the left leg straight. When sitting down at 90 degrees, Always try to sit tall so it helps engage postural muscles, muscles of the abdominals, not so much that you can't breathe. Breathing is important in yoga, when you sit like this, flex your feet as well, this engages your quadriceps, and your legs are working and active.
Sitting like this already like working out. Now take the right foot, and place one of the feet on the inside of the thigh. You want to be facing straight. To extend another leg, the left leg is the parallel length of the mat, Facing the left foot, flexed quadriceps engaged! Lengthens through the spine. That's very important. Anytime you move the spine forward before doing a backbend or the side bend, you have to lengthen through the spine. Lift your arms up. lifting your arms up also helps lengthen the spine. Exhale, Forward Fold. Release your hands on either side of your feet. Leave your forehead where it can rest. Stay there for five long breaths. Inhale, rise up. And exhale, release.
Here is how you can instruct your students
Let's extend the right leg, flex your foot and place a soul of the left foot against the inner right thigh. Let your hips face the front and lengthen through the spine, lift your arms up, exhale, and bend forward. Keep lengthening your spine, as you breathe in. Relax and lower them as you exhale. Stay here for five long breaths. So that's Janusirasana.
You might have problems with knees, or very tight hamstring. Bend your knees a little bit, and keep you spine straight. This also keeps you from unduly compressing the bones in your lower back. Inhale moving through the spine, Exhale to lean forward.
Some people, when they bend forward, they round out the back. This means they are bending from the lumbar spine and not from the hip. When that happens, it's really a lot of pressure on the lumbar spine. And they end up hurting themselves. Simply bend the knees slightly and try to be conscious of bending from the hip.
There is a variation of Janusirasana called parivrtta Janusirasana.
Parivrtta means on the side or twisting. vrtti means turning your back.
Patanjali the master of Yoga When explains what yoga means yoga is the stopping of the turning of the mind and turning off the mind.
Now you are going to do Parivrta Janusirasana which just means you are gonna do it Janusirasana sideways.
So this time hips will be facing the side. And now this is a side bend so you inhale through the spine, and just bend that directly to the side. You don't want to curl down, you want to keep stretching with your arms up and turn your head up towards the sky, palms facing down, Inhale to come up and exhale to release.
If you cannot open your legs very wide, try to reach for the side instead of trying to reach for your foot. It makes it for a more effective side bend.
Congratulations you've done janusirasana.