I cant say for sure it is without seeing it,but musclewood is pretty easy to identify by its distinct appearence....i have made a bow from it,which has since been retired now,but shot thousands of arrows
Heres what the back looks like,its been dyed a brown color,and i steel wooled the ridges after dying it to highlight the muscles.
And here it is braced hanging on the stump from wence the bow came from
If you look to the right limb tip there is an american hornbeam,and another one to its right