I apologize for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
It is natural for tomato vines to bend over like that. Actually it doesn't really hurt them and they'll just turn up at the ends and end up creating a mound on what ever trellis they are growing on. Even when they break the stems remain connected and sort of heal over and keep growing. If you are still concerned I suggest create a taller trellis when you plant them to provide more room to grow.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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