Bilateral and anterior-posterior muscular imbalances in swimmers
Ted Becker, Ph.D. and Rod Havriluk, Ph.D.
In J. P. Vilas-Boas, F. Alves, A. Marques (Eds.), Biomechanics and Medicine in Swimming X. Portuguese Journal of Sport Sciences, 6(Suppl. 2), 327-328.

Bilateral differences are common in swimmers. Anterior-posterior differences are not only common, but also related to injuries (1). The purpose of this study was to determine the relative magnitude of bilateral and anterior-posterior differences in swimmers.


The subjects were 19 competitive swimmers (12 males and 7 females) between the ages of 14 and 17. Peak hand force was measured performing two aquatic exercises (horizontal arm abduction and adduction in a standing position) and two swimming strokes (freestyle and backstroke) with Aquanex (previously described and validated in 2).


The peak force values were significantly higher (p<.05) for both exercise adduction than abduction and for the swim stroke with the arm in the adducted position (freestyle) than the abducted position (backstroke). Bilateral differences were trivial (.1σ) in comparison.

Figure1. Peak Hand Force Values for Exercise and Swimming


The magnitudes of the anterior-posterior differences were large for both exercise (1.5σ) and swimming (.8σ). A training regimen that strengthens the arm abductors may not only decrease the incidence of injuries, but also increase hand force and, therefore, performance in backstroke. Clinical evaluations can identify related structural conditions.


  1. Becker, T. (1982). Competitive swimming injuries: their cause and prevention. Paper presented at the American Swim Coaches Association World Clinic, Dallas, TX.
  2. Havriluk, R. (1988). Validation of a criterion measure for swimming technique. Journal of Swimming Research: 4(4), 11-16.