I agree with the others - it def sounds like Braxton hicks. I also started getting them at around 23 weeks, and also after exercise.

I get them quite often now, and they're more intense after any kind of physical activity (including house work!).

Just remember that BH are perfectly normal and its your body's way of preparing itself. Your baby also gets an extra boost of blood supply when they occur.

Keep an eye on it though and note down how often they occur and whether anything in particular sets them off. I would then tell your care provider when you see them next, so they are aware of them.

HTH