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The Question of Handedness

When performing client assessments, do you ask if they are right or left handed? Handedness is not usually a standard question on assessment forms, but maybe it should be added. Handedness can have a definite impact on posture and the risk for developing musculoskeletal injuries.

Muscle imbalances can occur from habitual movement patterns, repetitive movements, injury, surgery, and incomplete rehabilitation of injuries (1). Handedness can further impact these imbalances. For someone that is right handed, they may display an inefficient posture that flows through the entire kinetic chain, from the hand all the way to the foot. Below is Kendall’s description of right handedness posture (for left handedness, the sides listed would be opposite).

The lengthened or underactive muscles would include (2):

  • left lateral trunk muscles
  • right hip abductors
  • left hip adductor
  • right peroneus brevis/longus
  • right TFL
  • left posterior tibialis
  • left flexor hallucis longus/digitorum longus

The shortened or overactive muscles (just the opposite of above)(2):

  • right lateral trunk muscles
  • left hip abductors
  • right hip adductor
  • left peroneus brevis/longus
  • left TFL
  • right posterior tibialis
  • right flexor hallucis longus/digitorum longus

Overall, when viewing the static posture of a client with right-handed posture, they would have a lower right shoulder with an adducted scapulae, lateral pelvic tilt with the right hip joint adducted with a medial rotation (left hip abducted), and even some pronation of the right foot (2). So if a client displayed this posture, recommendations could be made regarding exercise programming (inhibit and lengthen the overactive, shortened muscles and activating the lengthened, underactive muscles, followed by integration) along with possible adaptations for activities of daily living (ADLs) and the work environment, such as carrying items in the left hand, putting the purse on the left shoulder, holding a baby on the opposite hip, leg crossing when sitting, switching from a mouse to a trackball type mechanism, using a headset for phone usage, driving an automatic transmission car versus manual shift, etc. (1).

About 30% of people are lefties and many of them are at risk for developing carpal tunnel based on how they position and hold their hand to write (3). Some “overwrite” with their wrist in a hyper-flexed position while others “underwrite” with the wrist in a hypo-flexed position (3). Southpaws use these positions so that they can see what they are writing, along with not smearing their work (4). Add to this that approximately one third of work-related musculoskeletal injuries occur in the elbow, forearm and wrist, and you can see how important it is too maintain proper range of motion and strength through the wrist and elbow joints (1,5).

During a client assessment, it may be wise to include a question regarding handedness. Also consider asking which leg they are dominant on as they are not always the same side dominant as the hand. Leg dominance may become clear during single-leg balance activities with more stability typically displayed on the non-dominant leg (6).

For more information check out NASM’s Corrective Exercise Specialization at www.nasm.org/CES


  1. Clark, M., Lucett, S. NASM Essentials of Corrective Exercise Training. Baltimore, MD: Lipponcott Williams & Wilkins. 2011.
  2. Kendall, F., McCreary, E., Provance, P., et al. Muscles, Testing and Function (4th ed) Baltimore, MD: Lippincott Williams & Wilkins, 1993.
  3. Marquardt, J. Carpal Tunnel Targets Left-handed People. All Stop Carpal Tunnel News. http://allstop.com/carpal-tunnel-articles/carpal-tunnel-and-left-handed-people.html
  4. Holder, M. Teaching Left-Handers to Write Handedness.org  http://handedness.org/action/leftwrite.html
  5. Barr, A., Barbe, M., Clark, B. Work-related musculoskeletal disorders of the hand and wrist: epidemiology, pathophysiology, and sensorimotor changes. Journal of Orthopedic Sports and Physical Therapy. 2004; 34(10):610-27.
  6. Hoffman, M., Schrader, J., Applegate, T., Koceja, D. Unilateral postural control of the functionally dominant and nondominant extremities of healthy subjects. Journal of Athletic Training. 1998; 33(4):319-22.
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The Author

Stacey Penney, MS, NASM-CPT, CES, PES, FNS

Stacey Penney, MS, NASM-CPT, CES, PES, FNS

Stacey Penney is the Content Strategist with NASM and AFAA. A 20+ year veteran of the fitness industry, she's worked with the top certification and continuing education groups. At NASM and AFAA she drives the content for American Fitness Magazine, blog and the social media platforms. Stacey received her degree in Athletic Training/PE from San Diego State University and an MS in Exercise Science from CalU, plus credentials in Health Promotion Management & Consulting (UCSD), Instructional Technology (SDSU), group fitness and yoga. Previous San Diego Fall Prevention Task Force Chair, she’s developed continuing education curriculum for fitness organizations in addition to personal training, writing, and co-coaching youth rec soccer.


  1. Mike
    July 31, 2013 at 7:35 pm — Reply

    @Ben: symmetry is to avoid injury, strength imbalances, flexibility imbalances, and in some cases coordination and power imbalances. It’s not just about aesthetics. Symmetry determines your functions. I think this article displays facts that increase your awareness of the usefulness of symmetry without claiming that it also means “perfection”. Some injuries or imbalances are created from small, seemingly trivial habits we have as humans. It’s important to pay attention. Do all people care about this? No. Does it affect people whether they care or not? Yes.

    • Ben
      August 6, 2013 at 3:32 am — Reply

      You misunderstood my comment – it has nothing to do with aesthetics. Again, the article implicitly argues that any asymmetry can lead to injury, including handedness – which is a permanent part of the human condition. Don’t you understand that symmetry on the human body is impossible? We *are* handed. We do have livers on one side of our body but not the other. If these things were actually inherently injurious, why would evolution select for them? Why are only left-right asymmetries injurious? Aren’t we obviously asymmetric front-back and top-bottom? Do you really have to test a person to know they are handed and that it might make one side stronger than the other? Saying that we are handed makes us asymmetric is akin to saying that having toes on our front makes us asymmetric. As a result, saying that asymmetries can lead to injury is either trivial and pointless or shows a banal understanding of the human condition. This viewpoint suggests that we are all fragile, asymmetric, constantly in need of corrective exercises and ignores the body’s ability to adapt to progressive stimuli not just locally, but globally. Its called the *general* adaptation syndrome for a reason. You can spend years chasing asymmetries and accomplish little, or in just a matter of months you can get your whole body strong with exercises like squats and deadlifts that stress the body the most systemically and therefore produce the largest and most general adaptations.

  2. Beh Hurt
    August 3, 2013 at 12:36 am — Reply

    I agree with Mike (below) that Ben’s somewhat understandable reaction may miss the point. I know that there are very visible differences in my right and left sides. When I took dance lessons fifty years ago, we made a point to do everything in both directions, and it was shockingly hard to do. Then I get lazy and quit doing that, and ended up with injuries to the shoulders that may have been a part of this neglect.

  3. August 27, 2013 at 8:40 am — Reply

    Thanks for the article. If the right posterior tibialis is shortened wouldn’t that decrease the pronation on the right foot in relation to the left?

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