Interlimb Asymmetries in Swimming and Their Impact on Performance: Evidence From a Scoping Review

Abstract

The objectives of this review were to (a) map the studies analyzing bilateral asymmetries in specific (in-water tests) and nonspecific (dry-land tests) swimming contexts and (b) investigate the effects of interlimb asymmetries on swimming performance. Searches were systematically conducted on 4 databases. Of 768 studies examined, 60 were eligible for the final selection (https://osf.io/46gya). Twenty-eight studies analyzed asymmetries during in-water tests, with asymmetry values ranging from 2.7 to 60.0%, and most studies (n = 18) reported significant between-limb differences (p < 0.05). Asymmetries were also analyzed during dry-land tests in 24 studies, with asymmetry values ranging from 1.1 to 16.6%. Interestingly, most of these studies (n = 12) did not verify any significant between-limb differences (p > 0.05). Eight studies measured asymmetries in both contexts and reported asymmetry values from −24.1–17.4%, with 4 studies finding significant differences between body sides (p < 0.05). Seven of the 60 studies selected investigated the relationship between asymmetries and swimming performance, with 5 reporting no meaningful associations. In conclusion, significant asymmetries in swimming are more evident during in-water than during dry-land tests. In addition, the few studies investigating asymmetries' influence on swimming performance reported that asymmetries rarely impact swimming performance.

Inter-limb differences in upper quarter mobility/stability are not associated with performance in competitive swimmers

“…Consequently, the observed LSI values of ≈ 3.4%–6.1%, ≈ 3.6%–7.6%, and ≈ 4.1%–7.5% in A-, B-, and C-squad swimmers respectively that were below injury-related cut-off values (≥7.75%), did not have a negative effect on swimming performance. This finding supports previous research ( 6 , 9 ) also reporting no or rarely impact of inter-limb asymmetry on swimming performance. However, we observed negative correlations between YBT–UQ performance (i.e., inferolateral reach direction and composite score for both arms and medial reach direction for the non-dominant arm) and swimming performance in B-squad swimmers.…”

“…This is consistent with a previous study ( 5 ) also stating no statistical differences in reach asymmetries between competition levels (i.e., collegiate vs. high school swimmers). The lack of significant differences in LSI values between the groups can rely on the high variability of inter-limb asymmetries ( 9 ), which can be seen in the relatively large standard deviations shown in Table 2 . According to Maloney ( 22 ), inter-limb asymmetry can vary depending on the practised type of sport, the volume of exposure, and the assessed physical performance, which makes comparative analyses difficult.…”

“…Usually, the YBT-UQ is recorded for both sides, thus inter-limb differences (i.e., asymmetry) can be detected as well as their association with athletic performance (7). In the first case, most of the available studies did not detect side differences in swimming (5,8,9) or in other sports like baseball (10, 11) and softball (10, 12). However, these studies were almost exclusively performed with adult athletes, which limits the transferability of the findings to young athletes due to growth, maturation, and development processes (13).…”