It depends on what your aims are. You can definitely do gymnastics if you can find an adults class. I am 45 and took up gymnastics at 43 (having done a little bit as a child many years ago). This year I competed at NZ Masters Games. There was another lady there who also took up gymnastics in her 40s, she had been training for only one year and was doing very well. Having said that, we are not 'competitive' gymnasts as such and especially at our age it is not realistic to expect that we would progress to the higher level skills. I believe there are adult women's competitions in the US, someone posted a video here last year, the women were in their 20s and 30s and they were awesome. I love doing gymnastics because it is fun and exciting, it is artistic and there is a lot of choice and variety.