## 4 Discussion  
The present study compared the neuromuscular efficiency index during concentric and eccentric phases of the biceps brachii action associated with regular breathing and Pilates breathing at varying load levels. The results showed that the neuromuscular efficiency index was lower when movement was associated with Pilates breathing than when it was associated regular breathing. The comparison between these two breathing techniques showed that Pilates breathing resulted in better neuromuscular efficiency of the biceps brachii during concentric and eccentric phases. According to previous studies, this finding can be explained by the better neuromuscular efficiency induced by Pilates breathing, which means that fewer motor units are required to produce the same level of force. Neuromuscular efficiency is calculated considering the amount of neural stimulation and the muscle's capacity to generate force. Therefore, a muscle that is able to generate greater torque with lower muscle fiber excitation is considered more efficient [15; 16]. A study carried out with 10 healthy women [17] comparing the excitation of the biceps brachii when using breathing techniques with a centralization technique showed an increase in biceps brachii motor unit recruitment, suggesting that there is greater muscle excitation when exercise is associated with centralization and breathing techniques from the Pilates method. During this study, the centering technique was associated with Pilates breathing, while the participants performed a biceps brachii isometric contraction during elbow flexion movement. The present study did not associate Pilates breathing with the centralization technique. In addition, the participants performed the biceps brachii isotonic contraction at the same time as the breathing technique. Therefore, these differences may be due to the distinct properties of concentric versus isometric contractions and to concurrent \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Right**} & \multicolumn{4}{c}{**Left**} & \multicolumn{4}{c}{**Right vs. Left**} \\ \hline  & \multicolumn{2}{c}{**Regular**} & **Pilates** & \multicolumn{1}{c}{**\(p\)**} & **ES** & **Regular** & **Filates** & \multicolumn{1}{c}{\(p\)**} & **ES** & **Regular** & **ES** & **Filates** & **ES** \\ \hline
20\% & conc & 2.9 & 3.2 & 0.03 \({}^{\ast}\) & 0.51 & 4.3 & 3.5 & 0.003 \({}^{\ast}\) & \(-\)0.71 & \(<\)0.001 \({}^{\ast}\) & 0.62 & 0.938 & 0.16 \\ of & conc & (0.5–10.5) & (0.5–19.4) & & moderate & (0.9–19.2) & (0.9–13.2) & & moderate & & moderate & & very small \\ MVIC & acc & 2.6 & 2.6 & 0.03 \({}^{\ast}\) & \(-\)0.47 & 2.9 & 2.7 & 0.036 \({}^{\ast}\) & \(-\)0.5 & & 0.16 & 0.66 & 0.15 \\  & acc & (0.3–11.5) & (0.3–7.8) & & small & (0.5–14.4) & (0.6–14.2) & & moderate & & & very small & very small \\
40\% & conc & 2.6 & 2.4 & & 0.92 & 4 & 3.4 & 0.91 & & 0.67 & & 0.62 \\ of & conc & (0.3–13.6) & (0.8–10.0) & & large & (0.1–13.7) & (0.8–17.9) & & 0.002 \({}^{\ast}\) & large & & & & 0.001 \({}^{\ast}\) & moderate \\ MVIC & acc & 2.5 & 2.3 & 0.07 \({}^{\ast}\) & 0.95 & 2.7 & 2.4 & 0.03 \({}^{\ast}\) & 0.94 & & 0.001 \({}^{\ast}\) & 0.13 & 0.579 & 0.08 \\  & acc & (0.2–10.8) & (0.7–8.2) & & large & (0.4–11.5) & (0.7–13.1) & & large & & & & very small & very small \\
60\% & conc & 2.7 & & & \(<\)0.001 \({}^{\ast}\) & \(-\)0.7 & 3.8 & 3.4 & 0.023 \({}^{\ast}\) & \(-\)0.59 & & 0.68 & \(<\)0.001 \({}^{\ast}\) & 0.63 \\ of & conc & (0.7–8.7) & (0.5–10.1) & & moderate & (1.0–22.4) & (0.9–15.3) & & moderate & & & moderate & & moderate \\ MVIC & acc & 2.6 & 2.2 & & 0.019 \({}^{\ast}\) & \(-\)0.45 & 2.4 & 2.2 & 0.03 \({}^{\ast}\) & \(-\)0.65 & & 0.787 & 0.14 & 0.66 & 0.13 \\  & acc & (0.5–7.8) & (0.4–11.3) & & small & (0.9–17.3) & (0.6–16.1) & & moderate & & & very small & very small \\ \hline \hline \end{tabular} Legend: conc = concentric; acc = eccentric; Right = right biceps brachii muscle; Left = left biceps brachii muscle; ES = effect size; \({}^{\ast}\) significant differences assigned.  
\end{table}