@zapata yes, definitely the already mentioned activities can help us to raise self-confidence. Early morning exercises pump up the adrenaline level. Adding to these, what I have found is participating in anything that intrigues us helps. Just participating - without any keen desire to win or lose - succeed or fail. I think it is often the results of an activity that keep us away from it. And builds the negativity within us, which in turn pulls down our confidence.
In the beginning, it will feel a bit awkward to face other people laughing at us. But once you are able to observe what good it is doing to us, we are able to face it better. And every such incident makes you stronger - mentally as well as emotionally! In fact, it is like the saying - What doesn't kill you makes you stronger!
All the best with your efforts!!