To study if a one piece body suite (T-balance, Telespro, Finland) is equally effective in maintaining peri-operative body temperature as forced air warming, during open low-back surgery of medium duration.

Inclusion Criteria:

• ASA 1-3
• Approved consent
• Expected duration of open back surgery of 60-120 min
• Prestudy core temperature (oral) of at least 36 degrees C

Exclusion Criteria:

• Known diabetes mellitus
• Any known illness or use of pre-op drugs which may interfere with normal temperature regulation
• Body mass index less than 17 or more than 35
• Pregnancy
• Any contraindication for warming device or temperature monitor