Evaluating a novel field test for the estimation of the anaerobic threshold in swimming

The aim of this study was to assess the feasibility of undertaking a swimming protocol suitable for generating estimates from a novel physiological performance analysis software (INSCYD) in a club environment, while also evaluating its reliability. Eleven highly-trained swimmers (16.7 ± 0.9 years, 176.3 ± 5.3 cm, 70.6 ± 7.2 kg) completed the INSCYD protocol (2 × 400 m then 2 × 200 m at incremental intensities; performed twice) and 7 × 200 m incremental step test (IST) on non-consecutive days. The time taken to complete each protocol and the associated number of lactate strips were monitored in each session. Blood lactate (BLa) and swimming times were recorded as inputs for generating physiological estimates from the INSCYD software and the IST protocol. The mean differences in the estimates of the anaerobic threshold for each protocol were compared, alongside Pearson correlations. Bland-Altman plots, intraclass correlation coefficients (ICC), technical error of the mean (TEM) and coefficients of variation (CV) assessed test-retest reliability of the INSCYD software estimates. Completing the INSCYD protocol required more time and more lactate strips, with large effects (Hedge's g = 2.0–3.7). Compared to estimates from the IST protocol, mean differences of 0.001 to 0.094 m.s −1 were found of the INSCYD anaerobic threshold, however most estimates were significantly correlated ( r = 0.62–0.91, p = 0.0001–0.05). ICCs were poor to moderate (0.05–0.59), TEM and CV were low, except for maximal rate of lactate accumulation (V˙La max ). Due to the increased resources, differences in estimates, and poor to moderate reliability, it is unclear whether the INSCYD software and its estimates are suitable for widespread implementation in daily training environments.