**3. Results**

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

sLT calculated after the 7 × 200 m test was similar with s-T30 (sLT: 1.317 (0.078) vs. s-T30: 1.316 (0.082) <sup>m</sup>·s<sup>−</sup>1, mean di fference (*SD*): −0.002 (0.010) <sup>m</sup>·s<sup>−</sup>1, 95% CL: −0.008, 0.005·m·s<sup>−</sup>1, *d* = −0.02, *p* = 0.634). A significant correlation was observed between sLT and s-T30 ( *R*<sup>2</sup> = 0.97, *r* = 0.98, *p* = 0.001).

#### *3.2. Comparison of Physiological Variables between Tests*

Measured BL-T30 was higher compared to BL-sLT (BL-T30: 4.7 (2.3) vs. BL-sLT: 3.4 (0.8) mmol·L−1, mean di fference (*SD*): 1.3 (2.4) mmol·L−1, 95% CL: 0.00, 2.35 mmol·L−1, *d* = 0.83, *p* = 0.05; Figure 2), and these variables were not correlated ( *R*<sup>2</sup> = 0.001, *r* = 0.03, *p* = 0.92). A Bland and Altman plot indicated agreemen<sup>t</sup> between calculated and measured values (Figure 2). During continuous swimming, HR-T30 was higher compared to HR-sLT (HR-T30: 173 (8) vs. HR-sLT: 161 (10) b·min−1, mean di fference (*SD*): 11 (11) b·min−1, 95% CL: 6, 18 b·min−1, *d* = 1.24, *p* = 0.02; Figure 2), and these variables were not correlated ( *R*<sup>2</sup> = 0.06, *r* = 0.25, *p* = 0.39). Agreement between calculated HR-sLT and measured HR-T30 values was observed (Figure 2). Moreover, VO2-T30 was not di fferent compared to VO2-sLT (VO2-T30: 41.7 (6.8) vs. VO2-sLT: 42.8 (6.2) ml·kg−1·min−1, mean di fference (*SD*): −0.88 (4.5) ml·kg−1·min−1, 95% CL: −3.22, 1.45 ml·kg−1·min−1, *d* = −0.16, *p* = 0.43) and these parameters were correlated (*R*<sup>2</sup> = 0.53, *r* = 0.73, *p* = 0.00). A Bland and Altman plot showed agreemen<sup>t</sup> between calculated VO2-sLT and measured VO2-T30 values (Figure 2).

**Figure 2.** Comparison between calculated and measured parameters in the two tests, (**a**) blood lactate concentration (BL), (**b**) oxygen uptake (VO2) (*N* = 12), (**c**) heart rate (HR). Individual values corresponding to BL-sLT, VO2-sLT, and HR-sLT are compared with BL-T30, VO2-T30, and HR-T30, respectively. Bland and Altman plots of mean vs. difference of two tests is presented in (**d**) BL-sLT and BL-T30, (**e**) VO2-sLT and VO2-T30, (*N* = 12), and (**f**) HR-sLT and HR-T30. Units of measure in (**d**), (**e**), and (**f**) are not shown for clarity and are the same as in the corresponding figure (**a**), (**b**), and (**c**) panels. \* *p* < 0.05 between BL-sLT and BL-T30, VO2-sLT and VO2-T30, and between HR-sLT and HR-T30. sLT: corresponding to speed at lactate threshold; T30: 30 min of continuous swimming.

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

During T30, the measured SR-T30 was higher compared to SR-sLT (SR-T30: 33.8 (2.9) vs. SR-sLT: 29.7 (4.1) cycles·min−1, mean difference (*SD*): 4.0 (3.9) cycles·min−1, 95% CL: 1.97, 6.07 cycles·min−1, *d* = 1.15, *p* = 0.002; Figure 3). SR-T30 and SR-sLT were not correlated (*R*<sup>2</sup> = 0.16, *r* = 0.41, *p* = 0.15). A Bland and Altman plot indicated agreemen<sup>t</sup> between calculated SR-sLT and measured SR-T30 values (Figure 3). Measured SL-T30 was lower compared to SL-sLT (SL-T30: 2.3 (0.3) vs. SL-sLT: 2.6 (0.4) <sup>m</sup>·cycles−1, mean difference (SD): −0.3 (0.2) <sup>m</sup>·cycles−1, 95% CL: −0.40, −0.14 <sup>m</sup>·cycles−1, *d* = −0.88, *p* = 0.001; Figure 3) and these parameters were correlated (*R*<sup>2</sup> = 0.55, *r* = 0.74, *p* = 0.003). A Bland and Altman plot showed agreemen<sup>t</sup> between calculated SL-sLT and measured SL-T30 values (Figure 3).

**Figure 3.** Comparison between calculated and measured parameters in the two tests, (**a**) comparison of arm-stroke rate (SR), (**b**) comparison of arm-stroke length (SL). Individual values corresponding to SR-sLT and SL-sLT are compared with SR-T30 and SL-T30, respectively. Bland and Altman plots of mean vs. difference of the two tests is presented in (**c**) SR-sLT vs. SR-T30, (**d**) SL-sLT vs. SL-T30. Units of measure in (**c**) and (**d**) are not shown for clarity and are the same as in the corresponding (**a**) and (**b**) panel. \* *p* < 0.05 between SR-sLT and SR-T30 and between SL-sLT and SL-T30. sLT: corresponding to speed at lactate threshold; T30: 30 min of continuous swimming.
