The American College of Sports Medicine and the United States Department of Health and Human Services recommend that healthy adults, under 65 years of age, complete a strength training routine that includes core exercises twice a week. They specifically advocate core training as a means to improve stability, reduce injury, and maintain mobility. There are countless exercises that target the primary core trunk muscles (abdominal and lumbar) with the aim of providing these benefits. However, it is unknown which exercises elicit the greatest activation thereby maximizing strength and functional gains.
PURPOSE: To determine whether core exercises that require activation of the distal trunk muscles (deltoid and gluteal) elicit greater activation of primary trunk muscles in comparison to core exercises that only require activation of the primary trunk muscles.
METHODS: Fourteen participants, 7 men and 7 women, completed 16 randomly assigned exercises (for example, traditional trunk flexion, upper locust trunk extension, unilateral standing balance, and forearm plank variations). Each exercise was performed for 10 repetitions at a cadence of 15 repetitions per minute with the exception of the balance poses, which were performed statically for 20 seconds. Therefore, all the exercises were analyzed during a 20 second period. We measured surface electromyography of the anterior deltoid, rectus abdominus, external abdominal oblique, lumbar erector spinae, and gluteus maximus. In order to determine if the muscle activation differed between exercises, we normalized the active muscle periods, performed a repeated-measures ANOVA and defined the statistical significance at p < 0.05.
RESULTS: Activation of the abdominal and lumbar muscles was greatest during the exercises that required activation of deltoid and gluteal muscles. For instance, the forearm plank variations required over two times the average activity of the rectus abdominus, external abdominal oblique, and lumbar erector spinae compared to a traditional trunk flexion and extension exercise (p = 0.02).
CONCLUSIONS: When completing the core strength guidelines, a routine that incorporates the activation of distal trunk musculature would be optimal in terms of maximizing strength, improving stability, reducing injury, and maintaining mobility.