Core Strengthening

Original Editor - Deborah Riczo

Top Contributors - Wanda van Niekerk  

What is Core?

In the literature, consumer as well as academic literature, there are various definitions available of what the core is and what core strengthening is. Even between various health professionals, there seems to be a wide definition of what core work is.

The core muscles are involved in maintaining spinal and pelvic stability and can be divided into two groups, according to function.[1] The first group of muscles is the inner core or deep core muscles. This group of muscles is also known as the local stabilising muscles.[1] Hodges et al (1996)[2] showed that the inner core acts in an anticipatory way and that these muscles are activated and fire before the global muscles are activated.

The inner core muscles include:[3][4]

The outer core muscles or the global muscles are also referred to as the “movers” and include:[1][3]

Integrated Model of Function

When the core muscles function normally, segmental spinal stability is maintained, the spine and pelvic area is protected and the stress or load that may influence the lumbar vertebrae and intervertebral discs are reduced.[1] In the case of dysfunction, such as a weak inner core, the outer core compensates for this weakness. Although the outer core muscles’ main function is movement and not stability it is able to contribute to stability with unexpected tasks or overload. As a result of this, splinting occurs and this leads to neuromusculoskeletal issues such as muscle spasms, neural compression and pain.[5]

Abdominal Canister

The inner core muscles all form part of the abdominal canister.

Diaphragm, transverse abdominis and pelvic floor activity during respiration. During active inhalation, the diaphragm descends as it contracts and the transversus abdominis and pelvic floor lengthen. During active exhalation, the pelvic floor and transversus abdominis contract, assisting diaphragm elevation.[6]

The abdominal canister functions similar to the action of a piston. As the diaphragm expands during inspiration, it lowers and presses down on the contents of the abdomen.[6] To allow for this pressure, the pelvic floor muscles relax and elongate. Below is a short summary of how the abdominal canister functions to facilitate breathing:[6]

Inspiration

  • Diaphragm contracts and flattens
  • Chest wall expands
  • Creates negative pressure in the thorax, drawing air into the lungs
  • Descent of diaphragm also causes expansion of abdominal wall and pelvic floor, due to increase in abdominal pressure

During quiet breathing – exhalation:

  • Diaphragm recoils to resting position
  • Passive expulsion of air from the lungs
  • The abdominal wall and pelvic floor gently contract to return to resting position

Increased respiratory demand – active exhalation:

  • Increases air expulsion efficiency to accelerate gas exchange
  • Accessory respiratory muscles contract to speed up diaphragm elevation
  • Pelvic floor and abdominal muscles are included within these accessory muscles – as they contract more forcefully – create a cranially directed increase in intra-abdominal pressure – this assists with diaphragm elevation.[6]

Activating the Core

Optimal postures

  • Rib cage
    • Ribs in location to the pelvis
      • The rib cage should be neutral over the pelvis for maximum activation of the inner core.[7]
  • Abdominal wall
    • Look out for doming in the abdominal muscles
      • This may indicate:
        • Breath-holding and creating a vacuum
        • Exercise is too difficult – rectus abdominis weak and contracting using a poor pattern
        • Be careful – pressure in the perineum area or bulging  - may aggravate pelvic organ prolapse
  • Another red flag to look out for:
    • Any type of incontinence symptoms or pelvic pain – may indicate that breathing strategy is wrong, exercise too difficult and you need to adapt or decrease the level of exercise and ensure proper breathing strategy[8]

Activating the Core in a Static Position

  • Supine position
    • Knees can be straight or bent
    • If the pelvic floor muscles are very weak, the hips can be elevated over a wedge or pillow – this way gravity is assisting and taking the weight of the pelvic floor[9]
    • Activate diaphragm with diaphragmatic breathing and using umbrella imagery
    • Exhale through pursed lips
    • Pelvic floor activation with exhale
      • Cues that can be used include:
        • Stopping flatulence or the flow of urine
    • Transversus abdominis activation
    • Cues such as:
      • zip up tight jeans
      • drawing in manoeuvre
      • blowing up a balloon
    • Static core activation can be performed in various positions, for example:[10]
      • Prone, 4-point kneeling, half-kneeling, standing[11]
Core activation prone.jpeg
Core activation 4point kneeling.jpeg

A caveat to consider when prescribing static core activation exercises to a client is if the patient is showing symptoms of an overactive pelvic floor, such as pelvic pain, pain with bowel movements, pain increasing with contraction, etc. In such cases, the patient should refrain from adding the pelvic floor contraction and rather focus on relaxing the pelvic floor.[12]

Activating the core in a Dynamic Position

  • Core strength can be challenged by adding movement[13]
  • This can be done in various positions and with various movements
  • Some examples are:
    • Supine
      • Adding alternate arm reaches
      • Adding alternate knee lifts – important to monitor if the patient’s core is able to control the weight of the leg with this movement. (A way to do this is to ask the patient to place hands on ASIS while performing an exercise. If ASIS’s are unable to remain stable with alternate knee lifts, rather prescribe an exercise such as heel slides or knee fall-outs (bent knee abduction and adduction) to start with.[9])
      • Combine opposite arm and leg
      • Adding knee extension as a progression from alternate knees in supine
      • Straight leg raise 
Core activation supine alternate arms.jpeg
Core activation knee lifts.jpeg
Core activation heel slides.jpeg
Core activation straight leg raise.jpeg
    • Prone
      • Glut sets with core activation
      • Adding hip extension – if open chain exercise is too difficult start with closed chain – keep toe on the ground and lift the knee
      • Alternate arms/legs
      • 4-point kneeling
        • Some caveats to remember with this position[9]:
          • Avoid this position in a patient with too large of a DRA
          • Avoid this position in a patient who is in the later stages of pregnancy and has a DRA
    • 4 -point kneeling
      • Adding alternate arms
      • Alternate arms and legs
Core activation 4point kneeling alternate arms.jpeg
Core activation 4point kneeling alternate legs.jpeg
    • ½ kneeling
      • This is a good position for core strengthening as it also incorporates balance training as well
      • Alternate arms reach – aim for good excursion in lattisimus dorsi
      • Trunk rotation
      • Can add light weights
    • Standing
      • Standing alternate arm raises, add exercises with Theraband
      • Make use of Bodyblade
      • Bosu
      • It is important to also focus on balance exercises, as evidence shows that pregnant women have decreased standing balance and are at a higher risk for falls, especially during the 3rd trimester.[14]
    • Higher-level Exercises
      • Plank  on elbows
        • Start off on knees, progress to on toes
Core Plank on knees.jpeg
Core Plank.jpeg
      • Side-plank
Core Side plank on knees.jpeg
Core Side plank.jpeg
    • Progress to whole-body movements, agility and balance
      • Lunges
      • Stepping
      • Stepping to the side
      • Side squats
      • High stepping, hand to opposite heel while moving

Conclusion

Core strengthening is effective from the inside (inner core first) to the outside. Modifications of the level of difficulty of exercises and breathing strategies can help avoid symptoms of doming, bulging, leaking and pain. It also motivates the patient when improvements are evident and challenges the patient in small incremental steps.

References

  1. 1.0 1.1 1.2 1.3 Chang WD, Lin HY, Lai PT. Core strength training for patients with chronic low back pain. Journal of physical therapy science. 2015;27(3):619-22.
  2. Hodges PW, Richardson CA. Inefficient muscular stabilization of the lumbar spine associated with low back pain: a motor control evaluation of transversus abdominis. Spine. 1996 Nov 15;21(22):2640-50.
  3. 3.0 3.1 Akuthota V, Ferreiro A, Moore T, Fredericson M. Core stability exercise principles. Current sports medicine reports. 2008 Jan 1;7(1):39-44.
  4. Saiklang P, Puntumetakul R, Swangnetr Neubert M, Boucaut R. The immediate effect of the abdominal drawing-in maneuver technique on stature change in seated sedentary workers with chronic low back pain. Ergonomics. 2021 Jan 2;64(1):55-68.
  5. Key J. ‘The core’: understanding it, and retraining its dysfunction. Journal of bodywork and movement therapies. 2013 Oct 1;17(4):541-59.
  6. 6.0 6.1 6.2 6.3 Siracusa C, Gray A. Pelvic Floor Considerations in COVID-19. Journal of Women's Health Physical Therapy. 2020 Oct;44(4):144.
  7. Lee DG. The Pelvic Girdle E-Book: An integration of clinical expertise and research. Elsevier Health Sciences; 2011 Oct 28.
  8. Casey EK, Temme K. Pelvic floor muscle function and urinary incontinence in the female athlete. The Physician and sportsmedicine. 2017 Oct 2;45(4):399-407.
  9. 9.0 9.1 9.2 Deborah Riczo. Core Strengthening. Physioplus, Course. 2021.
  10. Moghadam N, Ghaffari MS, Noormohammadpour P, Rostami M, Zarei M, Moosavi M, Kordi R. Comparison of the recruitment of transverse abdominis through drawing-in and bracing in different core stability training positions. Journal of exercise rehabilitation. 2019 Dec;15(6):819.
  11. Escamilla RF, Lewis C, Pecson A, Imamura R, Andrews JR. Muscle activation among supine, prone, and side position exercises with and without a Swiss ball. Sports health. 2016 Jul;8(4):372-9.
  12. Stein A, Hughes M. A classical physical therapy approach to the overactive pelvic floor. The overactive pelvic floor. 2016:265-74.
  13. Escriche-Escuder A, Calatayud J, Aiguadé R, Andersen LL, Ezzatvar Y, Casaña J. Core Muscle Activity Assessed by Electromyography During Exercises for Chronic Low Back Pain: A Systematic Review. Strength & Conditioning Journal. 2019 Aug 1;41(4):55-69.
  14. Cakmak B, Ribeiro AP, Inanir A. Postural balance and the risk of falling during pregnancy. The Journal of Maternal-Fetal & Neonatal Medicine. 2016 May 18;29(10):1623-5.
  15. Rehab my patient. Core control 7. Available from https://www.youtube.com/watch?v=MAzd-kxnH18 (last accessed 8 April 2021)
  16. Rehab my patient. How to improve lower abdominal strength 2. Available from https://www.youtube.com/watch?v=I665l7U4oOA&t=34s. (last accessed 8 April 2021)
  17. Rehab my patient. BOSU balance catching a ball. Available from https://www.youtube.com/watch?v=T69RBvA5Jek&t=14s. (last accessed 8 April 2021)