Understanding upper limbs in-water force in young swimmers with Statistical Parametric Mapping analysis

The present study aimed to compare swimmers' in-water force according to swimming performance tiers within the same age group and compare the dominant and non-dominant upper limbs within the same tier throughout continuous and discrete analyses. Fifty-two young swimmers (girls and boys: 12.13 ± 0.71 years) were split up into two tiers based on the mean speed: Tier-1 (n = 28), low-tier; and Tier-2 (n = 24), top-tier. In-water forces of upper limbs were assessed with a differential pressure system composed of two hand sensors during 25 m front crawl swimming. Force-time curves of the underwater paths and the mean peak force (FPEAK, N) were considered for further analysis using discrete and continuous analyses (Statistical Parametric Mapping, SPM). Results showed that top-tier swimmers applied greater in-water forces in front crawl (∼61 N) when compared to the low-tier (∼51 N). With SPM, differences were found between 64-74 % and ∼60-90 % of the underwater path of the stroke cycle for the dominant and non-dominant upper limb, respectively. Both upper limbs appear to apply a similar in-water force (p > 0.05), regardless of the performance tier. Therefore, swimmers within the same age group differ in the upper limbs applied in-water force during the front crawl. The SPM analysis seems to provide more insights into the applied force during the hand path,as it allows identifying differences according to the underwater phases.