Just sitting upright properly can be challenging if you try to hold the position for a period of time. It requires both strength and flexibility in the muscles of your legs and back. Think of forming a 90-degree angle with your body with a hinge at your hips.
1 Start by sitting on a flat surface with your legs extended in front of you in line with your hips. Place your palms or fingertips on the floor next to your hips. Focus on lifting up through the crown of your head. Activate your legs by lifting your kneecaps up toward your thighs and moving the backs of your thighs toward the floor. Press down with your hands to help lift the torso. Hold for 10 to 15 seconds.
2 To further challenge yourself, maintain this position and lift your arms overhead. Your hands should be shoulder-width apart with your palms turned inward. Reach upward with your fingertips and thumbs. Keep your elbows straight and your upper arms next to your ears. (As you move your arms back, don't allow your lower ribs to pop out.) Hold for 10 to 15 seconds.
— Karen Voight