If you want to gain muscle, you can make a good start with body weight exercises, and with improvised makeshift weights. You can use a backpack full of soda bottles of water or bags of sand to make many body weight exercises harder.
If you mean to get serious about strength, then I’d recommend free weights to anyone: a set of dumbbell bars and a barbell bar, and loose weight plates to load them with. And some reference on how to use them properly, such as Mark Rippetoe’s Starting Strength. You can pirate that.
The materials can be expensive, and it takes some reading up to get the movements right (and it can be dangerous if you do it wrong), but it’s worth it.
There are a lot of nonsensical snake oil fitness gimmicks out there, but free weights are a tried and true type of equipment that has been used for centuries. It freakin’ works.
In your case, though, your main interest seems to be running, for which you won’t need a lot of strength, I suppose. I think muscle gain need not be one of your main objectives.
I’m no expert on running, but it seems obvious enough that you can become better at long distance running by running long distances regularly. Running up stairs seems like a good idea too, but not as good as just doing the thing you want to become better at.
@jazzticity
Extra protein, a myth? Not really.
Muscles are physical devices that are made of a physical substance. Without building materials, they cannot grow, not even if you torture them really badly. And that building material is protein. It’s literally indispensable to muscle development.
Imagine a Pharaoh trying to build a pyramid by whipping the slaves really hard, but not giving them enough bricks.
You don’t need protein shakes, though, there’s plenty of regular food stuffs that are high in the right proteins. Eggs, meat, fish, cottage cheese, that sort of things. But pay attention to what else is in there, too. For example, cheese is very high in protein, but also in saturated fat.
Whether regular meals gets you enough protein depends on what your meals normally look like, I suppose. But the more you demolish your body, the more protein you need in order to rebuild it stronger.
As for agony: I’m all for pushing your envelope, but there is such a thing as overexertion. Disregard your body’s warning signals at your own risk. They’re not always just nagging, sometimes things actually go wrong.