['To evaluate the activity of neck extensor muscles during different extension exercises with muscle functional magnetic resonance imaging (mfMRI).', 'Cross-sectional.', 'University laboratory.', 'Healthy subjects (N=11; 7 men, mean age +/- SD, 34+/-5.6y; 4 women, mean age +/- SD, 23.3+/-5.2y; group mean age +/- SD, 30.1+/-7.5y).', 'Not applicable.', 'mfMRI measures of T2 relaxation were made for the multifidus (Mul), the semispinalis cervicis (SCe), the semispinalis capitis (SCa), and the splenius capitis (SpC) at C2-3, C5-6, and C7-T1 in response to 2 head/neck orientations: craniocervical neutral (CCN) and craniocervical extension (CCE). Subjects performed three 1-minute repetitions of each condition at 20% maximum voluntary contraction.', 'Significant shifts were observed in all muscle groups at the C5-6 and C7-T1 levels after both conditions (P=.04) except the SpC muscle at C5-6 with CCN (P=.17). T2 shifts in the SCa were significantly greater in response to CCE than CCN at C2-3 (P=.03) and C5-6 (P=.02). Similarly, CCE resulted in larger shifts than CCN in the Mul/SCe at C7-T1 (P=.003). No segmental differences were observed between exercises for SpC (P=.25).'] Does craniocervical orientation affect muscle activation when exercising the cervical extensors in healthy subjects?