Cramped

A few days ago, my hand cramped up while playing the bass. Was it a case of no warm up before playing? That's not it; I was playing guitar for at least 30min before switching to bass. My take here is that my hand is simply not used to the extended scale of the bass; I'm more accustomed to the guitar. Someone also said that I'm playing the bass like a guitar, sometimes I just go too fast which might contribute to the painful experience. Oh, well...