I recently added long Stair Climb runs to my workout routine and regardless of how good your baseline of fitness is you learn quickly that if you are pushing yourself in another activity that involves different motions and muscle groups and pace, there is not a 1:1 translation on the cardio or endurance front.
Just because you run Triathlons of marathons does not mean you should expect to be able to keep pace with a top tennis player playing marathon sessions.
This is what I just stated in the
MMA V Boxing Cardio thread and the below article fleshes it out even more.
Why climbing stairs is always a killer, no matter how fit you are
We run to work. We dutifully attend spin classes. We lift, bro. We’re fit. And yet, give us a flight of stairs to run up and suddenly, we turn into panting puddles. Climbing stairs is ridiculously hard, no matter how much exercise you do...
But why? Why are stairs such a nightmare, and can you ever get better at them?...
Our bodies run on something called Adenosine triphospahte (ATP) – the petrol that keeps us alive and functioning. How much we produce and how quickly, depends on which energy system we use to produce it. When you exercise, your body burns through fuel and it’s clever enough to know when to switch between certain sources of energy. When you’re running a marathon or doing any kind of slow, steady, long workout, you use your aerobic system – burning through carbs and fat. If, say, you’re doing a 400m run, chances are that you’re using your lactic system – not quite a sprint but going at a good lick. That lactic system produces ATP without oxygen and is manufactured from the breakdown of glucose to pyruvic acid in the muscle cells...
The final energy system is our phosphocreatine system – our fastest source and most quickly expendable source of ATP. We access this first and rely on it for sprints, strength weight training and other explosive movements. It’s the system that give us that burst of energy, that raw power. When we climb stairs, we’re tapping into that system first – but it only lasts for 10 seconds (approximately) and comes from the glycogen already in our muscles. So once that 10 seconds is up, we start to transition into our next energy system and after some time, into our aerobic one which is the most sustainable and, arguably, least painful...
Climbing stairs is the ultimate functional fitness test – you teach the body to become more efficient in how it operates. That’s why boxers use running up stairs as a training tool; they’re constantly having to push their lactic threshold with sustained, explosive movements...