A recent report studied how using foam pillows of three different heights affected the comfort and electromyographic (EMG) activity of the neck and mid-upper back muscles of participants. The study was performed by a team of therapists and researchers in the University of São Paulo School of Medicine in São Paulo, Brazil. Performed in 2014 and published in 2015, the study revealed the associations among pillow height, EMG activity, and perceived comfort. Twenty-one asymptomatic adults were observed using three different foam pillows of 5 cm, 10 cm and 14 cm, or approximately 2 inches, 4 inches and 5 1/2 inches. Study participants rated their comfort using a 100-mm visual analog scale, while researchers calculated EMG activity of the neck and mid-upper back muscles, called the sternocleidomastoid and upper and middle trapezius muscles. Participants considered height 1 (approximately 2 inches) to be the least comfortable and height 2 (approximately 4 inches) the most comfortable. In addition, all muscle groups showed statistical differences in EMG activity between heights 1 and 2, but not between heights 2 and 3. Individuals who prefer sleeping with a flat pillow may want to think twice, as a four-inch pillow may be the best choice for perceived comfort and back and neck support.