Linda, Jenna has always been a "Stander" and has very strong legs. In fact - if her arms had been any stronger, she probably would have been crawling by about 4 months!!!
Some babies have strong legs, others have strong necks - I think they are all so different.
I didn't realise how strong her legs were until I played with another baby that had floppy legs!! She wouldn't stand in my lap at all.

BTW - that baby is now racing around just like Jenna, and pulling herslef up on everything too. I think strong legs may help them stand/crawl earlier, but that doesn't mean that weaker legs will prevent them!!

Fi