Acceleromyography (AMG) is the most wide spread used method to assess neuromuscular block during anesthesia. However AMG is known to be inaccurate when compared to the gold standard in neuromuscular transmission monitoring, electromyography (EMG). Furthermore when the patients arms require to be positioned next to the body and beneath surgical drapes, AMG measurements are often hindered and inaccurate. The TOF cuff is a new device which measures NMB at the upper arm with a blood pressure cuff. It overcomes the previously mentioned disadvantages of AMG. However, it validity compared to EMG and AMG has not yet fully been investigated.