Electromyography (EMG) is an electrodiagnostic medicine technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed by using an instrument called an electromyograph. The electrical activity is measured by placing electrodes over your entire body and recording the level of muscle activity induced by certain exercises.
A study was conducted to find which exercises cause the greatest amount of activity within each muscle group and, as a consequence, determine which exercises will produce the greatest gains in mass and strength. This study was conducted by Tudor O. Bompa, PhD & Lorenzo J. Cornacchia. Both men and women were used in the study and all subjects had at least two years experience with resistance training.
EMG studies are not absolute however does provide good insight into potential muscle activity in certain exercises. As with all testing methods there are limitations and should not be regarded as the absolute baseline in muscle activity in any given exercises. In addition inter-individual variability must be taken into consideration. In addition, nor is this a recommendation of any of the exercises listed.
Below are the results of this study: (100% would signify maximum muscle fiber stimulation)
Reference: Tudor O. Bompa, PhD, Mauro Di Pasquale, MD, Lorenzo J. Cornacchia: Serious Strength Training, 3rd ed.