Apply the above concept to your hips. When you sit, your hips are in a "flexed" position. Therefore, the muscles that flex your hips are in a shortened state. You probably spend at least a third of your day sitting down. Think about how much time those hip flexor muscles stay shortened. A lot. Over time, they become tighter and tighter until you look like the old man in the picture. So unless you want to look like that, perform the stretches shown below.
The sartorius originates at the ASIS and proceeds to traverse obliquely and laterally down the thigh to eventually insert at the anterior surface of the tibia, just inferomedial to the tibial tuberosity, as part of the pes anserinus. In addition to flexing the hip and knee, the sartorius aids in the abduction of the hip. It is innervated by the femoral nerve (i.e., the posterior division of L2 and L3).
Remember my special answer: here it is… MOUTHTAPERS exist. People out there will tape their mouth closed during sleep so that they can breathe their nose. Even during the day sometimes. Why? Because the nose is directly connected to the diaphragm while the mouth is connected to the chest. Sure, increase chest mobility and your lungs may be able to expand more which will allow more air to be held, BUT HOW CAN YOU HOLD THAT MORE AIR IF YOUR DIAPHRAGM is weak? You won’t. So everything I just talked about must be done through the nose. Notice yourself breathing with your mouth and SWITCH right away. It takes work and energy. How you breathe during the day rolls over to how you breathe during the night.