Would someone have a different fast/slow twitch muscle ratio in their chest versus their legs?
In short yes, the percentage of slow/fast fibres will vary with muscle group. Pectoralis major tends to be about 60% fast-twitch fibres. "Legs" is a bit of a generalisation - your soleus, in common with other postural muscles, is predominantly slow-twitch fibres, other leg muscles contain more fast-twitch fibres (taken from this study):
- Soleus 70% slow-twitch
- Vastus intermedius 47%
- Gastrocnemius 50%
- Vastus lateralis 32%