[Purpose] This study compared the activity of trunk and hip muscles during different degrees of lumbar and hip extension. [Subjects] The study enrolled 18 participants. [Methods] Two exercises (hip and lumbar extension) and two ranges (180° and <180°) were studied. [Results] Differences in degree of extension affected the percentage maximal voluntary isometric contraction of the lumbar erector spinae and biceps femoris muscles, with significantly higher average values at >180° than at 180° lumbar extension. No significant differences were found in gluteus maximus activity according to exercise type or range. [Conclusion] Hip extension may be more effective and safer for lumbar rehabilitation than lumbar extension.