Short-term effect of crunch exercise frequency on abdominal muscle endurance Thursday, 16 April 2015 | Biomecánica y salud Juan-Recio C., López-Vivancos A., Moya M., Sarabia J. M., y Vera-Garcia F. J. (2015). Short-term effect of crunch exercise frequency on abdominal muscle endurance. The Journal of Sports Medicine and Physical Fitness, 55(4), 280-289.