# Effect of Central Motor and Neuromuscular Impairments on Front Crawl Body Roll Characteristics of Para Swimmers

## TL;DR

This study examines how physical impairments affect body roll in Para swimmers, finding that their movement patterns differ from non-disabled swimmers and may impact classification criteria.

## Contribution

The first comprehensive analysis of body roll kinematics in Para swimmers with central motor and neuromuscular impairments.

## Key findings

- CMNI swimmers showed reduced shoulder roll and torso twist but increased hip roll compared to non-disabled swimmers.
- Body roll patterns varied widely among CMNI swimmers, but no differences were found between upper- or lower-limb subgroups.
- Current classification thresholds for trunk rotation may be invalid as actual torso twist during swimming is lower than the threshold.

## Abstract

Rotation of the trunk about its long axis or ‘body roll’ is essential for maximising front crawl swimming performance yet research on how physical impairment affects body roll is extremely limited. This study quantifies body roll kinematics in swimmers with and without central motor and neuromuscular impairments (CMNI). It was hypothesised that body roll kinematics differ between CMNI and non-disabled swimmers, are associated with sport class (level of impairment) and are influenced by upper and lower-limb functional levels.

Three-dimensional motion analysis of 27 CMNI (sport classes 2–9) and 13 non-disabled competitive swimmers at 100–200 m race pace provided body roll kinematics, including shoulder and hip roll ranges and torso twist. Health conditions of the CMNI group were cerebral palsy (n = 12), spinal cord injury (n = 10) and neuromuscular disorders (n = 5). CMNI swimmers were divided into three upper-limb [mild (n = 9), moderate (n = 9), severe (n = 9)] and three lower-limb function subgroups [bilateral (n = 2), unilateral (n = 6), without kick (n = 19)] based on their Froude efficiency (a measure of how effectively upper limbs contribute to propulsion) and the number of lower limbs actively kicking during trials, respectively.

The CMNI group exhibited lower shoulder roll range (104 ± 11° vs. 88 ± 21°, p < 0.05) and torso twist (58 ± 13° vs. 48 ± 22°, p < 0.05) but greater hip roll range (62 ± 10° vs. 75 ± 29°, p < 0.05) than the non-disabled group. Statistical non-parametric mapping revealed less shoulder roll from 0 to 28%, less hip roll from 0 to 10%, greater hip roll from 91 to 100%, and less torso twist from 15 to 32% and from 75 to 81% of the cycle, in the CMNI than the non-disabled group (p < 0.05). CMNI body roll patterns varied widely, but discrete and continuous variables did not differ between upper-limb subgroups or between lower-limb subgroups.

CMNI swimmers exhibit different body roll patterns to non-disabled swimmers. The study findings can be used to inform Para swimming coaches and improve the sport-specificity of land-based and water-based assessments currently used to classify CMNI swimmers.

This is the first comprehensive study of body roll in Para swimmers. It establishes the effect of central motor and neuromuscular impairment (CMNI) on front crawl body roll kinematics and how this impacts swimming performance.Para swimmers with CMNI present considerable variation in their body roll strategies due to different levels of function in the upper limbs, trunk and lower limbs, either individually or in combination, reflecting unique self-organising adaptation to their individual organism constraints.Torso twist angles during non-disabled and CMNI front crawl swimming are notably lower than the threshold angle currently applied by World Para Swimming classifiers in their land-based test to define impaired trunk rotation. This indicates that the threshold may not be valid for classifying Para swimmers as it exceeds the amount of torso twist actually required during front crawl.

This is the first comprehensive study of body roll in Para swimmers. It establishes the effect of central motor and neuromuscular impairment (CMNI) on front crawl body roll kinematics and how this impacts swimming performance.

Para swimmers with CMNI present considerable variation in their body roll strategies due to different levels of function in the upper limbs, trunk and lower limbs, either individually or in combination, reflecting unique self-organising adaptation to their individual organism constraints.

Torso twist angles during non-disabled and CMNI front crawl swimming are notably lower than the threshold angle currently applied by World Para Swimming classifiers in their land-based test to define impaired trunk rotation. This indicates that the threshold may not be valid for classifying Para swimmers as it exceeds the amount of torso twist actually required during front crawl.