I've been a marathon runner for 15 years and coached a couple of running clubs. Now days nearly all of our club runners do distance training wearing a running belt of some sort (some also use an arm strap for their phone in addition). In the belts, we often carry a phone, earbuds, 2-4 gel packs, a car key, emergency taxi/bus fare, and a small water bottle or two. I've known runners to carry mace as well. That's quite a bit of stuff but easily manageable not only for training but also in the actual timed events (though our faster experienced runners often carry much less).
I very rarely have a need to carry a "running knife" unless in certain areas; and it's for self defense against animals not people. In my years of running I've been attacked twice by dogs. To me bearing the additional weight of a small knife for training runs is negligible relative to the rest of the stuff I sometimes carry. I just don't like carrying large knives, and I don't like carrying anything in my shorts or clipped to the waistband. Main thing is having the belt to carry the knife, preferably in a quick access pouch, but clipped to it works ok too. I like the Benchmade 417 Fact. Here it is with my Nathan Zipster Lite (the label peeled off) running belt which I also highly recommend. It's so light and breathable I often forget I'm wearing it.
Either of these would do fine . The Cold Steel is a far better SD knife , but the Spyderco is much lighter and more rust proof .
