1 Most episodes of acute lower back pain are caused by muscle strain, such as from lifting a heavy object, a sudden movement or a fall. 2  The low back pain can be very severe and last for several hours, several days or even a few weeks.
3. Characteristics of the Normal ECG. It is important to remember that there is a wide range of normal variability in the 12 lead ECG. The following normal ECG characteristics, therefore, are not absolute. It takes considerable ECG reading experience to discover all the normal variants.
These electrical signals are sent to the ECG machine, where they are processed, and printed out as an âECG tracing.â The electrodes are then removed. The ECG test takes less than 5 minutes to perform. What Does the ECG Tracing Look Like? The picture on this page shows a typical, normal ECG. The electrical signals generated from the ten electrodes have been processed into 12 âviewsâ of the heartâs electrical activity - the so-called 12-lead ECG.