Science of Core training

[this_dot]

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:

In comparison to general exercise, core stability exercise may be more effective in relieving pain and improving back-specific function for patients with chronic LBP in the short term. However, no significant differences were observed between core stability exercise and general exercise in pain and functional status in the long term.

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:

Soccer players with non-contact lower extremity sprain and/or strain have less core endurance than non-injured players. Reduced core endurance is associated with increased incidence of injury. Improving side-bridge hold time, specifically, may reduce the risk for injury.

The rationale for this is well stated by Coulombe et al:

Another commonly held perception about core function is that a stable base of support acts as a transfer point for powerful extremity muscles to generate forceful dynamic contractions. Poor core stability is thought to place excess force from the extremity muscles on the spinal structures, leading to earlier fatigue and a higher risk of injury.

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

 

[coconut23]

@this_dot The "How should I train them?" part is really really incomplete. You don't even talk about the importance of working the core through a range of motion. Isometrics like Planks objectively suck for both strength and hypertrophy training. The core is already worked isometrically in all the major compound exercises. At the end, I am frustrated that you wrote all this without really providing the key message from a strength programming perspective, which should be:

• Do the major compound exercises, this will naturally activate your core muscles - e.g. Pull-Ups, HSPU, Push-Ups, Rows, FL/BL/SL progressions,Back Squat, Deadlift
• Do assistance exercises that will target the stuff not covered by the compound exercises
  • Dynamic core flexion: Hanging Leg Lifts, GHD Sit-Ups
  • Dynamic core extension: Full ROM Hyperextensions, Jefferson Curl
  • Dynamic core abduction/adduction: Side Plank Lift, Standing Lateral Bend
  • Dynamic core rotation: Standing Rotation with a broomstick, Lateral Throw

 

[this_dot]

@coconut23 Fair point.

My goal was not to provide a complete guide to core training, although I see how it would be useful. I searched pubmed and tried to summarized the papers I found more interesting or with information I never found before.

 

[mph]

@coconut23 These posts are about the sciences and research findings behind certain claims, and I enjoy them above and beyond just training tips. If you have sources supporting your points please share!

 

[this_dot]

@mph Exactly right! Thanks

 

[firefnx]

@coconut23 what is HSPU, FL/BL/SL ?

 

[missymckibben]

@coconut23

working the core through a range of motion.

Many people rate hollow body holds very highly. Aren't they good enough to strenghten the core? I also heard that they are good to avoid any spinal injuries.

 

[alvinou]

@this_dot Great read! Sort of intuitive for me, although it’s nice to have that intuition confirmed!

 

[missymckibben]

@this_dot

They showed greater activation of core muscles with Scapula adducted

I have seen mostly that you have to keep the scapulas abducted (protracted) during plank. Am I getting something wrong here?

 

[this_dot]

@missymckibben It was quite an interesting conclusion. It makes sense that core activation is higher with scapulas adducted, but I always did them in protraction as you're saying. Honestly, I don't know in what is this advice based on.

 

[gothiclovesjesus]

@this_dot today i learned what "et al" means