A Comparison of the Mechanical Properties of the Deltoid and Trapezius Muscles and Shoulder Range of Motion in Competitive Young Swimmers Across Different Swimming Strokes

Abstract

Background Competitive swimming is a sport that places a high level of repetitive load on the shoulder complex and requires intensive use of upper extremity movements. Different swimming strokes may demonstrate distinct differences in shoulder joint biomechanics and muscle activation patterns, which may lead to stroke-specific adaptations in shoulder joint range of motion and the neuromechanical properties of muscles. However, studies examining shoulder joint range of motion together with the biomechanical properties of shoulder girdle muscles assessed by myotonometry according to swimming strokes in young swimmers are limited. The aim of this study was to investigate whether the biomechanical properties of shoulder girdle muscles and shoulder joint range of motion differ according to swimming stroke in competitive youth swimmers. Methods A total of 32 competitive swimmers (14 females, 18 males) were included in this cross-sectional and comparative study. Participants were divided into four groups according to their dominant swimming stroke: freestyle (n=8), breaststroke (n=9), backstroke (n=8), and butterfly (n=7). Shoulder joint range of motion (flexion, extension, abduction, adduction, internal rotation, and external rotation) was assessed bilaterally using a standard goniometric method. The biomechanical properties of shoulder girdle muscles were measured using the MyotonPRO device, and oscillation frequency (muscle tone), dynamic stiffness, logarithmic decrement, relaxation time, and creep parameters were recorded. Differences in shoulder joint range of motion were analyzed using the Kruskal–Wallis test. In the evaluation of muscle biomechanical properties, analysis of covariance (ANCOVA) was applied while controlling for age, height, body mass, and training experience as covariates. Results No differences were found among swimming strokes in shoulder flexion, extension, abduction, internal rotation, and external rotation range of motion (p>0.05). In contrast, shoulder adduction range of motion differed significantly according to swimming stroke on both sides (right p=0.003; left p=0.008). Freestyle swimmers demonstrated lower adduction angles, whereas butterfly and backstroke swimmers exhibited higher values. Myotonometric assessment showed no stroke-related differences in oscillation frequency, muscle stiffness, relaxation time, or creep parameters (p>0.05). However, a stroke-related difference was observed in the decrement value of the anterior deltoid muscle (p=0.002), with freestyle swimmers demonstrating lower decrement values compared with some other stroke groups. Conclusions The findings of this study indicate that shoulder joint range of motion in competitive youth swimmers is largely independent of swimming stroke, although shoulder adduction range of motion may exhibit stroke-specific differences. In addition, while most neuromechanical properties of shoulder girdle muscles appear to be independent of swimming stroke, the elastic properties of the anterior deltoid muscle may be related to stroke mechanics. These findings provide important information for the evaluation of stroke-specific biomechanical adaptations in swimmers, performance analysis, and the planning of training programs aimed at preventing shoulder injuries. Trial registration ClinicalTrials.gov Identifier NCT07425873, registered on 27/01/2026.