Posture and breathing.
Poor posture, in particular stooping, prevents the lungs from fully expanding when inhaling, and less air enters them. In addition, with poor posture, the diaphragm - the main respiratory muscle - contracts and cannot move freely. This also reduces the amount of oxygen entering the body. The so-called vital capacity of the lungs also depends on the position of the head. When it is strongly tilted forward (protraction), the biomechanics of breathing changes, and lung capacity decreases by a third. All this means that insufficient oxygen enters the body - first of all, this will affect the functioning of the brain, and will manifest itself with symptoms such as fatigue, drowsiness, impaired concentration and memory.