T.P.
Hi M.,
What Rachel wrote is not exactly correct. Hypotonia and muscle strength are 2 separate issues. Hypotonia is controlled by the nervous system, not the muscles. Hypotonia MIGHT go along with some other issue (such as autism, Down syndrome, etc.) or it might be an issue all by itself. You can't fix hypotonia by strengthening the muscles, but if you have stronger muscles, it can help mask the hypotonia a little.
I'm a pediatric PT, so I'm very familiar with kids with hypotonia. A lot depends on the degree of hypotonia. There's a big range from mild to severe (wheelchair-bound, can't stand up). Kids who have mild hypotonia often don't qualify for therapy in school unless the hypotonia affects some specific function at school. They tend to be very flexible. Some might benefit from some shoe insert orthotics to keep their feet in a good position as they grow and prevent back/knee pain. Sometimes these kids don't excel at athletics, and sometimes they do well in activities like gymnastics, ice skating, ballet, and martial arts, which require lots of flexibility. It is great for kids with mild hypotonia to do lots of activities like climbing, which helps keep their muscles as strong as possible.
Kids who have moderate or more severe hypotonia often qualify for school therapy to help them with specific activities like handwriting, sitting in their chairs, climbing stairs, etc. If they are too functional at school to qualify for therapy, they can usually receive private therapy at a clinic to help with any issues outside of school (balance, bike riding, etc.).
Hope this helps!