Strength training. Why do you want to be strong? Are you feeling old before your time maybe? Have you tried before but “failed”? It doesn’t take that much effort to really make a difference to your quality of life. Click and have a look.
Kids fitness classes are enormously beneficial. Finally, it seems, outdated myths surrounding children and exercise (e.g. stunted growth etc.) are mostly gone. Participation later in life is markedly increased if you start young.