Some of us have the idea that the people sitting in the stands are just watching the runners and cheering them on. While that's true, the idea behind the word "witness" is someone who bears testimony to what he or she personally knows about. In short, the people watching the runners are runners themselves. Think of the famous Bolder Boulder 10K race in Colorado. Here's what I saw when I entered the stadium last May.
Eventually the stadium was filled with 50,000 people, all of whom had run the race. So when we think of the witnesses in Heb. 12:1, let's understand them as not just an audience!
Just something to consider.