"To lengthen the spine" means to straighten or stretch out the spine, making it taller and more aligned. It is often used in certain exercises or practices to improve posture and relieve tension or discomfort in the back. Full definition
Plough is such an effective move as it extends and stretches the muscles in the shoulders, upper back and neck, as well as lengthening the spine. (sportsinjuryclinic.net)
As you both inhale reach your arms up to the sky and concentrate on lengthening the spine upwards as well. (fitbodyhq.com)
Beginners can place a blanket roll at the top of their thighs, lightly resting their thighs on the roll as they and actively lengthen their spine forward and up. (yogauonline.com)