Is it normal to wake up with bruises after sleeping on a futon?

I moved to Japan just over a week ago and I've been using a futon until Nitori deliver my bed and mattress. I've been waking up with bruises on my skin, especially on my arms. I'm wondering if this is normal, as I'm worried that it might be a symptom of some other issue. Google doesn't seem to suggest any link between new futon use and bruises. Hopefully someone can enlighten me. Thanks.