Ok I was dissatisfied with my post.
First, Janstarblast, HIIT (High Intensity Interval Training) the most effective method of training for Cardio, Stamina like you want, improved respiration, improved blood flow, stronger heart beats and lung compressions (iunno what to refer to it as), improved reflexes, improved explosiveness and power; are all benefits of HIIT, each benefitting all areas of fitness.
Basically, you can do ratio's. You can do a 1:1, 1:2, 1:3, whatever you want. What that means is that for whatever activity you're doing, you do a period of moderate activity followed by a period of your most intense form of that activity. A simple example is running, and as an example, I'll use a 1:2 ratio: after warming up and stretching, you start at a nice jog that isn't tough, but not simple. Short of paying $100 for a heart rate monitor, imagine a scale from 1-10, one being sitting on the couch with a pizza, and 10 being running for your life from a criminal. A 5-6 should be good. If you have a heart rate monitor, 50-60% of maximum heart rate. That goes for 1 minute (or any time, as long as the numbers go in the ratio's you want.), then you sprint. A 9-9.5 is the number on the scale. You do that for 2 minutes (2x1=2) then repeat. Do that as long as you want. You can do it for any exercise really, and it applies to all areas of fitness.
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So, Cookies^^.
I don't know how old you are, but every year after 35 people lose 1% of their flexibility. Of you're not over 35, that doesn't matter to you right now, but what does matter is that some people are naturally limber, and some are naturally tight.
Tight muscles tire out faster, and you obviously can't go through your body's full range of motion. More flexibility = more power out of your muscles. When you don't stretch, inflexible tendons and ligaments, and connective tissues shrink, leading to injury (when you could've been fine if you stretched).
If you play sports, you probably know how important proper posture and a solid core are. Yoga won't work on your explosiveness; but functional fitness, right? In doing sun salutaions and whatever else you choose, you work on your balance and you're coordination. When you have better balance, you're able to react quicker and more efficuently. When combined with the posture and core work that yoga gives, all of it adds up to a juicy conundrum of progression. Simple yoga poses tire out even the strongest of people, due to their isometric nature. Isometric moves really get blood flowing, helping your stamina in sports and activities.
If you want me to help any more or have any questions, just ask.