**3. Results**

#### *3.1. Swimming Speed Comparison between Tests*

Swimming speed prescribed by the 5 × 200-m test (V4) was successfully reproduced during the 5 × 400-m training set (V4 = 1.325 (0.08) <sup>m</sup>·s<sup>−</sup>1; V-5×400-m = 1.287 (0.10) <sup>m</sup>·s<sup>−</sup>1; mean difference (SD): 0.04 (0.08) <sup>m</sup>·s<sup>−</sup>1; 95% CL: 0.060, 0.017 <sup>m</sup>·<sup>s</sup>–1; *d* = −0.42, *p* = 0.122). Additionally, significant correlation was noticed between V4 and V-5×400-m (r = 0.64, *p* = 0.02) and agreemen<sup>t</sup> was indicated by Bland and Altman plot (bias (SD): −0.04 (0.08) <sup>m</sup>·s<sup>−</sup>1).

#### *3.2. Comparison of Physiological Variables and Rating of Perceived Exertion between Tests*

Following the training set, BL-5×400 was not different compared to 4 mmol·L−<sup>1</sup> (BL-V4 = 4.0 (0.0) mmol·L−1; BL-5×400 = 5.0 (2.6) mmol·L−1; mean difference (SD): −1.0 (2.6) mmol·L−1; 95% CL: −1.53, −0.42 mmol·L−1; *d* = 0.75, *p* = 0.231, Figure 2). Bland and Altman plot indicated agreemen<sup>t</sup> between calculated and measured values (bias (SD): −1.0 (2.6) mmol·L−1). Training HR-5×400 was higher compared to HR-V4 (mean difference (SD): −7.2 (10.7) b·min−1; 95% CL: −11.22, −3.11 b·min−1; *d* = 0.59, *p* = 0.04, Figure 2) and these parameters were correlated (r = 0.63, *p* = 0.03). Bland and Altman plot showed agreemen<sup>t</sup> between calculated and measured values (bias (SD): 7 (11) <sup>b</sup>·min−1).

**Figure 2.** (**a**): Comparison between blood lactate concentration corresponding to V4 calculated after a progressively increasing speed 5 × 200-m test (BL-V4) and blood lactate measured during a constant speed intermittent swimming training set of 5 × 400-m (BL-5×400). (**b**): Comparison between heart rate corresponding to V4 calculated after a progressively increasing speed 5 × 200-m test (HR-V4) and heart rate measured during a constant speed intermittent swimming training set of 5 × 400-m (HR-5×400). *\*: p* < 0.05 between HR-V4 and HR-5×400-m.

The calculated RPE values were successfully reproduced during the training set (RPE-V4 = 4.25 (2.09); RPE-5×400 = 5.17 (1.69); mean difference (SD): −1.0 (2.5); 95% CL: −1.6, −0.4; *d* = 0.52, *p* = 0.224]. Calculated and measured values were not correlated (r = 0.16, *p* = 0.60). Bland and Altman plot showed agreemen<sup>t</sup> between calculated and measured values (bias (SD): −1.0 (2.5)).

#### *3.3. Comparison of Biomechanical Variables between Tests*

Measured SR during the training set was increased compared to calculated SR and measured SL was decreased compared to calculated SL (Figure 3). Although a significant correlation was noticed between measured and calculated SR and SL values (SR, r = 0.57, *p* = 0.05; SL, r = 0.96, *p* = 0.001). Bland and Altman plot indicated agreemen<sup>t</sup> between calculated and measured for SR and SL (bias (SD): −5.6 (3.3) cycles·min−<sup>1</sup> and 0.13 (0.09) <sup>m</sup>·cycles−1; Figure 3).

**Figure 3.** (**a**): Comparison of the stroke rate. (**b**): comparison of stroke length. Values corresponding to V4 and calculated after a progressively increasing speed 5 × 200-m test (SR-V4 and SL-V4) are compared with the stroke rate and stroke length measured during an intermittent constant swimming speed 5 × 400-m training set (SR-5×400 and SL-5×400). The 95% confidence limits (95% CL) and effect size (*d*) are indicated under the figures. (**c**): Bland and Altman plots of mean vs. difference in SR-V4 and SR-5×400 and (**d**): Bland and Altman plots of mean vs. difference in SL-V4 and SL-5×400. V4: speed corresponding to a blood lactate concentration of 4 mmol·L−1. Units of measure in (c) and (d) are not shown for clarity and are the same as in the corresponding figure (**a**) and (**b**) panel. *\* p* < 0.05 between SR-V4 and SR-5×400 and between SL-V4 and SL-5×400-m.
