Grandsons stomach muscles are to tight

What does it mean when they say my 4 month old grandson needs physical therpy because his stomach muslces are to tight and it makes it hard for him to sit up right?  Is that anything to worry about?  What is the name for that and also what can we do to help him?   Thanks Kaysoma

[tmv]

Many people lay their babies on their stomachs for "tummy time" to stretch these muscles out and help with neck/back strength from early on (watching them carefully, of course). Is he able to do tummy time?

[AnnieBrooke]

I knew someone this happened to but she was a little older than 4 months.  They had to give her muscle relaxers.  I'm glad to hear it's something that can be handled with PT instead.