Stand lunge-length in front of a bench making sure your knee does not extend past your toes. Hold a dumbbell in each hand and rest the top of your left foot on the bench behind you. Lower your body until your rear knee nearly touches the floor and your front thigh is parallel to the floor. Then push through the heel of your front foot to return to standing, keeping the back foot on the bench. Repeat for required reps then switch legs.
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.