Microneurography: Traditional nerve conduction studies only detect activity in the largest nerve fibres. To record from the smallest nerve fibres the investigators may perform microneurography. This is a minimally invasive technique in which the activity of single nerve fibre is recorded from peripheral nerves and is for directly detecting the function of pain fibres in peripheral nerves in humans. In this test a thin micro-electrode is placed next to the nerve fibres. This provides the only direct means to directly record C-fibre activity in humans. J Serra a co-investigator in this study and has a long track record in using microneurography.