Running: The ninja used to run leaning front. Starting with the right foot and right hand. The samurai were also trained to run the same way believing that the weight at the belly (sword etc.) naturally helped them get faster and also forced them to run faster and faster in order to keep their balance. The Ninja used to train up in the hills to get larger lungs and some ninja could run 200km a day.
Breathing: The ninja had to quietly wait hours and hours on the rooftop or a basement of a house they are trying to sneak in. They had to learn to hold their breath for a longer period of time and breath so silently. For silent breathing practice they used to put a feather on the tip of their nose and make sure it doesn’t fall off when they are breathing their mouth shot. The ninja also learned how to control their breathe by holding it first short durations (e.g. 15 seconds) and then gradually increasing that duration to 2-3 minutes).
The Ninja walk (shinobi aruki):
Ninjas had to be very quiet when walking and often trained by walking on the sand and gravel to test their silent and trace-less walking skills. They had 3 main principles when walking
Lower your body to the ground by bending your knees, if you stand tall you are more likely to be spotted.
Start walking by simultaneously moving your right foot and right arm followed by the left foot and left arm.
Step on the floor by the outer edges (sides) of your feet. This reduces the sound. Some major stealth walking techniques require you to step on your tiptoe first or your heel first but the ninja used to step on by the outer sides of their feet first.
The ninja always followed basic stealth techniques such as
Distract the enemy (creating sounds in the opposite direction, modern day phone call)
Reduce the light and visibility for the enemy (act at night without the moonlight, turn the lights off)
Observe and take advantage of the weak points of the enemy (pretend seeking help)
Conceal the sounds you are making (use animal companions or animal sounds)