## 4 Discussion and Implications  
Results in Table 1 show that subjects fulfilled the main condition of the test: swimming speed consistently increased from the minimum at the first stage (F1--\(v_{\text{0 exp}}\) = 1.38 m\(\cdot\)s\({}^{-1}\), M3--\(v_{\text{0 exp}}\) = 1.34 m\(\cdot\)s\({}^{-1}\)) to the maximum at the last stage (F1--\(v_{\text{0 exp}}\) = 1.70 m\(\cdot\)s\({}^{-1}\), M3-- \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{3}{*}{**Subjects**} & \multicolumn{6}{c}{\(v_{\text{0 exp}}\) = \(P_{ai}\times e_{g}\times e_{p}\times F_{rf(\text{d})}\)\({}^{-1}\)} & \multicolumn{6}{c}{**Main Indicators**} \\ \cline{2-13}  & \(v_{\text{0 exp}}\) & \(P_{ai}\) & \(P_{to}\) & \(e_{g}\) & \(e_{p}\) & \(F_{rf(\text{d})}\) & \(P_{ai(\text{sa})}\) & \(C_{x(\text{m})}\) & \(S_{\text{(bs)}}\) & \multirow{2}{*}{\(\mathbf{Sh}_{v}\)} & \multirow{2}{*}{\(\mathbf{C}_{m}\)} \\  & **(m\(\cdot\)s\({}^{-1}\))** & **(W)** & **(W)** & & & & & & & & \\ \hline M1 (front crawl) & 1.84 & 3381 & 210 & 0.062 & 0.69 & 79 & 3560 & 0.335 & 0.140 & 0.225 & 36 \\ M2 (butterfly) & 1.72 & 3218 & 220 & 0.068 & 0.65 & 83 & 3400 & 0.405 & 0.142 & 0.487 & 36 \\ M3 (backstroke) & 1.69 & 3200 & 208 & 0.065 & 0.67 & 82 & 3346 & 0.395 & 0.145 & 0.444 & 37 \\ M4 (breaststroke) & 1.52 & 3211 & 211 & 0.066 & 0.71 & 99 & 3481 & 0.482 & 0.178 & 0.991 & 33 \\ \hline \hline \end{tabular} Legend: \(v_{\text{0 exp}}\)—average swimming velocity at the lap, \(P_{ai}\)—metabolic power, \(P_{iu}\)—mechanical power, \(e_{g}\)—mechanical efficiency, \(e_{p}\)—propelling efficiency, \(F_{rf(\text{d})}\)—fromtal component of active drag in the unsteady mode of body motion, \(P_{ai(\text{sa})}\)—metabolic power calculated based on the second approach, \(C_{x(\text{m})}\)—average value of the dimensionless coefficient of the frontal component of the active drag force, \(S_{\text{(bs)}}\)—average value of the characteristic hydrodynamic size of the subject’s body, Sh\({}_{v}\)—Strouhal number, \(C_{m}\)—dimensionless coefficient (\(C_{m}=P_{ai}\times P_{hi}\)\({}^{-1}\)).  
\end{table} 
Table 3: Numerical values of parameters of the mathematical model 1 and the main indicators for the male subjects in the last stage of the step-test. Figure 3: Relationships between \(v_{\text{0 exp}}\) and \(e_{g}\) in the swimming pool 8 \(\times\) 100 m step-test for different swimming techniques in female (**A**) and male (**B**) subjects. \(v_{\text{0 exp}}=1.69\) m\(\cdot\)s\({}^{-1}\)). The calculation of the average swimming speed on the test segment was carried out according to the formula \(v_{\text{0 exp}}=100\) m \(\times\) (\(t+0.75\) s)\({}^{-1}\), where 0.75 s is the standard empirical value at a distance of 100 m, used by coaches and specialists in order to exclude the positive effect of turning on this indicator [7,14]. Such an increase was naturally accompanied by a progressive increase in oxygen consumption during work (\(V\text{O}_{\text{2 tot}}\)) and during the first two minutes of recovery (\(V\text{O}_{\text{2 bor}}\)). The net capillary blood lactate concentrations in each one of the consecutive test stages (\(\Delta La\)) also escalates with swimming speed. The metabolic energy input increased as well as the metabolic power. With increasing swimming intensity (\(v_{\text{0 exp}}\)), the absolute contribution of each metabolic pathway (\(E_{ai(\text{Aer})}\), \(E_{ai(\text{AnAl})}\) and \(E_{ai(\text{AnAl})}\)) to the total energy production also increased, but the partial contributions of the three energy sources changed differently. As \(v_{\text{0 exp}}\) increases, the total external mechanical power also increases (F1--from 69 to 128 W, M3--from 103 to 208 W). Meanwhile, \(e_{g}\) was inversely related to \(v_{\text{0 exp}}\). Indeed, \(e_{g}\) decreased from 0.098 (F1) and 0.119 (M3) at the minimum \(v_{\text{0 exp}}\) to 0.050 (F1) and 0.065 (M3) at the maximum \(v_{\text{0 exp}}\).