A Practical Approach to Assess the Load-Velocity Profile in Sprint Swimming: Reliability of a Portable Resistance Device.

Salerno, P, Fassone, M, Bove, M, and Bisio, A. A practical approach to assess the load-velocity profile in sprint swimming: Reliability of a portable resistance device. J Strength Cond Res XX(X): 000-000, 2026-The load-velocity (L-V) profile has recently been proposed as a practical model for describing sprint swimming performance. However, its application is often limited by the need for expensive, complex equipment, and by the lack of data on nonelite swimmers. This study examined the test-retest reliability of the L-V profile in front crawl swimming using an economical, portable isotonic resistance device. Twenty-six trained/developmental swimmers (11 females and 15 males) performed 2 identical testing sessions, with a 3-5 days interval between them. Each session consisted of 5 maximal 25-m semi-tethered front crawl sprints performed with different external loads. Swimming velocity was measured over a 5-m mid-pool section using video analysis. Individual L-V relationships were established through linear regression to estimate the following: theoretical maximal velocity (V0); theoretical maximal load (L0); relative load (rL0); and slope of the L-V relationship (Slv). Test-retest reliability ranged from good to excellent in men (ICC = 0.86-0.95) and women (ICC = 0.86-0.94). Inter-rater reliability also showed good-to-excellent agreement across all variables (ICC = 0.86-0.98). Absolute reliability was acceptable, with coefficients of variation ≤8.8% and minimal systematic bias in Bland-Altman analyses. The L-V profile obtained using a portable isotonic resistance device demonstrates good-to-excellent reliability in front crawl swimming. This approach provides a practical and accessible method for estimating sprint swimming performance that can be used in daily training settings.