What’s the “core”? Huxel Bliven et al
The “core,” also referred to as the lumbopelvic-hip complex, is a 3-dimensional space with muscular boundaries: diaphragm (superior), abdominal and oblique muscles (anterior-lateral), paraspinal and gluteal muscles (posterior), and pelvic floor and hip girdle (inferior).The inherent nature of these muscular boundaries produces a corset-like stabilization effect on the trunk and spine.
Core stability is the capacity to maintain equilibrium of the vertebral column within its physiologic limits by reducing displacement from perturbations and maintaining structural integrity
Should I train my core muscles?
There is vast literature focusing on the benefits of core strength and endurance. Mainly in two fields:
Chronic low back pain
In a review by Wang et al which looked at papers that compared general exercise with core strengthening exercise for chronic low back pain, they concluded:
Injury prevention
For example, Abdallah et al compared core muscle endurance and hip muscle strength between soccer players who experienced non-contact lower extremity sprain and/or strain injury during their season and those who did not. They conclude:
The rationale for this is well stated by Coulombe et al:
How should I train them?
The most common exercises are, of course, planks. There is some science focusing on them. Here is some interesting stuff:
Influence of Scapular Position on Musculature Activation
Cortell-Tormo, et al, 2019 used electromyography (EMG) to compare muscular activation during prone plank with posterior vs anterior pelvic tilt and scapula adducted vs abducted.
They showed greater activation of core muscles with Scapula adducted (image for reference) and pelvis tilted posteriorly (example).
They attribute the findings regarding scapula position to a change in trunk inclination and disabling the fascia system tension (which connects the lower limbs to the upper limbs).
Plank progression
Calatayud et al, 2017 tried to rank different plank positions on the abdominal muscles activation.
They showed higher lower abs activation using the suspended roll-out plank. Upper abs and Obliquous were more activated also using suspended roll-out plank but also suspended prone plank. For lumbar activity, side planks showed the most activation.
Suspension exercises
Mok et al, 2017 compared 4 suspension exercises (on TRX) using EMG: hip abduction in plank, chest press, 45◦ row, and hamstring curl.
They showed higher activation of core muscles with the lower limb exercises (hip abduction and hamstring curl), being that Hip Abduction activated the external and internal oblique the most and Hamstring curl activated Lumbar multifidus the most.
Cugliari et al, 2017 also used EMG to assess core muscle activation in 4 different exercises: Rollout, Bodysay, Pike, Knee-tuck.
The rollout showed significantly higher activation of abdominal muscles compared with the other exercises.
They also conclude (although based on extrapolation from other studies) that these exercises are more challenging than an isometric plank performed under stable conditions.
My personal conclusions
I can only see upsides in having strong core muscles, obviously. There are numerous articles showing benefits for improving and preventing low back pain and preventing injuries. Also, the stronger your limbs become, the harder it gets to stabilize your trunk and core muscles become more important.
However, is it really necessary to do specific core exercises (like planks or rollouts)? That’s hard to say, because when we do compound exercises, especially under unstable circumstances, our core muscles are being trained as well, and will become stronger. For example, Snarr et al showed an increased activation of the rectus abdominis when doing push-ups using a suspension device compared with the traditional push-up, similar to the activation seen doing crunches.
So, most people doing compound exercises, and using rings, should have a strong enough core, but if you feel like doing specific training, there are most likely only benefits to it.
References
Abdallah AA, Mohamed NA, Hegazy MA. A COMPARATIVE STUDY OF CORE MUSCULATURE ENDURANCE AND STRENGTH BETWEEN SOCCER PLAYERS WITH AND WITHOUT LOWER EXTREMITY SPRAIN AND STRAIN INJURY. Int J Sports Phys Ther. 2019;14(4):525–536.
Calatayud, J., Casaña, J., Martín, F., Jakobsen, M. D., Colado, J. C., & Andersen, L. L. (2017). Progression of Core Stability Exercises Based on the Extent of Muscle Activity. American Journal of Physical Medicine & Rehabilitation, 96(10), 694–699.
Cortell-Tormo, J. M., García-Jaén, M., Chulvi-Medrano, I., Hernández-Sánchez, S., Lucas-Cuevas, Á. G., & Tortosa-Martínez, J. (2017). Influence of Scapular Position on the Core Musculature Activation in the Prone Plank Exercise. Journal of Strength and Conditioning Research, 31(8), 2255–2262.
Coulombe BJ, Games KE, Neil ER, Eberman LE. Core Stability Exercise Versus General Exercise for Chronic Low Back Pain. J Athl Train. 2017;52(1):71–72. doi:10.4085/1062-6050-51.11.16
Cugliari G, Boccia G. Core Muscle Activation in Suspension Training Exercises. J Hum Kinet. 2017;56:61-71. Published 2017 Mar 15. doi:10.1515/hukin-2017-0023
Huxel Bliven KC, Anderson BE. Core stability training for injury prevention. Sports Health. 2013;5(6):514–522. doi:10.1177/1941738113481200
Mok, N. W., Yeung, E. W., Cho, J. C., Hui, S. C., Liu, K. C., & Pang, C. H. (2015). Core muscle activity during suspension exercises. Journal of Science and Medicine in Sport, 18(2), 189–194.
Snarr RL Esco MR Witte EV Jenkins CT Brannan RM. Electromyographic activity of rectus abdominis during a suspension push-up compared to traditional exercises. J Exer Phys online. 2013;16(3):1-8.
Wang XQ, Zheng JJ, Yu ZW, et al. A meta-analysis of core stability exercise versus general exercise for chronic low back pain. PLoS One. 2012;7(12):e52082. doi:10.1371/journal.pone.0052082