Velocity Variability and Performance in Backstroke in Elite and Good-Level Swimmers

Abstract

Backstroke swimming, a cyclic and continuous movement, displays a repeating structure due to the repeated action of the limb, presenting similar (but not identical) cycles. Some variability is generated by instabilities, but this may play a functional role in the human performance, allowing individual adaptations to constraints. The current study examined the role of velocity variability in backstroke performance, hypothesizing that this variable is associated with swimmers’ performance. Sixteen elite and fifteen good-level swimmers were video recorded in the sagittal plane when performing 25 m backstroke at maximal intensity in order to determine hip velocity and mean velocity, stroke rate, stroke length and indexes of coordination/synchronization. Lyapunov maximal exponent and sample entropy were also calculated for successive cycles. The elite swimmers’ performances were more unstable (0.1742 ± 0.1131 versus 0.0831 ± 0.0042, p < 0.001) and complex (0.9222 ± 0.4559 versus 0.3821 ± 0.3096, p < 0.001) than their good-level counterparts, but intracycle velocity variation did not differ (11.98 ± 3.47 versus 12.03 ± 3.16%, p > 0.05). Direct relationships were observed between mean velocity and stability (r = 0.40, p = 0.03), as well as with complexity (r = 0.53, p = 0.002), with intracycle velocity variation and complexity also being related (r = 0.38, p = 0.04). Backstroke performance is associated with velocity variability, with elite swimmers being able to control it through several adaptations, overcoming the high drag and inertia.

Intracycle Velocity Variation in Swimming: A Systematic Scoping Review

“…Sixty-eight trials were considered for judging risk of bias, with 20 [ 6 , 20 , 28 , 36 , 37 , 40 , 41 , 87 , 88 , 89 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 ] and 48 considered as having overall low and high risk (respectively). The selection of participants showed a low risk of bias for 79% of the trials due to the overall purpose of evaluating competitive swimmers ( Figure 2 ).…”

“…Except for front crawl, studies were mostly interested in analysing IVV when swimmers were performing at maximal intensity. IVV was not related to mean velocity in front crawl or backstroke [ 37 , 40 , 41 , 100 ], even if a non-linear relationship was also observed (with the velocity increase leading to a IVV decrease in young swimmers in the four swimming techniques [ 3 ] and in the swimmers with high-level front crawl [ 4 ]). Data gathered from so many swimmers and diverse samples should be cautiously analysed.…”

“…Conversely, IVV increased throughout paces in less skilled swimmers [ 23 ]. IVV for highly trained swimmers was lower than for trained counterparts at all front crawl swimming velocities (in both senior and youth age groups) [ 23 , 39 ] but in backstroke, IVV did not differ between elite and highly trained swimmers [ 40 ].…”

“…When applying dynamical system approaches to swimming, nonlinear properties can be observed [ 114 ], with their magnitude differing according to the swimming technique and the swimmer’s level. The breaststroke and butterfly techniques displayed more complex (but predictable) patterns [ 85 , 114 , 122 ] and elite vs. non-elite swimmers’ performances were more unstable and complex (even though their IVV did not differ) [ 40 ].…”

“…Better propulsive continuity in front crawl and lower swimming economy in breaststroke and butterfly (due to elevated resistive forces and amount of work) are the suggested explanations. In addition, when comparing competitive swimming levels for the same pace and swimming technique, better swimmers were observed to have higher [ 36 , 37 ], lower [ 10 , 21 , 23 , 33 , 34 , 38 , 39 ] or similar IVV [ 40 , 41 ] values compared to their counterparts. Regarding conventional swimming techniques, breaststroke presents the highest IVV values, followed by butterfly, backstroke and front crawl [ 3 ], although alternative techniques’ scores are very similar [ 42 ].…”