LAUSR

Abstract Our aim was to establish the determinants explaining the wetsuit advantages in middle-distance swimming efforts. Thirty-one triathletes and open water swimmers performed two 400 m front crawl bouts in a 25 m swimming pool with swim and wetsuits (with 48 h rest in-between). Anthropometric, kinematic and physiological variables were measured and Pearson correlation coefficients and stepwise linear regression analysis were used to determine their relationships. Associations observed in the 400 m front crawl included time improved using wetsuit with swimmers age (r=0.38; p =0.017), cross-sectional area (r=0.33; p =0.034), wetsuit upper limbs thickness (r=–0.49; p =0.010), ΔInternational Swimming Federation Points (r=–0.39; p =0.016), Δstroke rate (SR, r=0.48; p =0.003), Δstroke length (SL, r=-0.39; p =0.015), Δpropelling efficiency (r=–0.37; p =0.019) and Δblood lactate concentrations (r=0.30; p =0.048) in the total sample. In females, associations were found between the time improved and wetsuit upper and lower limbs thickness (both r=–0.78; p =0.011), and in males associations were found between time improved and age (r=0.43; p =0.030), ΔSR (r=0.56; p =0.005) and ΔSL (r=–0.44; p =0.026). Furthermore, 48% of the 400 m front crawl time improved was explained by wetsuit upper limbs thickness and SR changes (total sample), 62% explained by the wetsuit lower limbs thickness (females) and 48% of this enhancement was related to age and SR changes (males). Therefore, faster upper and lower limbs actions and wetsuit upper and lower limbs thickness are beneficial for 400 m front crawl performance improvement.