## 4 Discussion

Table 2: Comparison of the neuromuscular efficiency index (sEMG%/kgf) considering the effects of regular and Pilates breathing techniques during concentric (conc) and eccentric (ecc) phases of the right and left biceps brachii muscle with 20%, 40%, and 60% loads, considering the maximum voluntary isometric contraction (MVIC). Descriptive data given as median (minimum; maximum). neural influences [17], because, in the previous study, the participants needed to focus their attention on two simultaneous techniques when performing the biceps brachii contraction (breathing and centralization techniques). Another study evaluated the effects of a centralization technique and Pilates breathing on lower-limb muscle activity during squats [18]. In this study, thirteen adults with some experience in the Pilates method performed three 60\({}^{\circ}\) squats under three experimental conditions: (I) normal breathing, (II) abdominal contraction with normal breathing, and (III) abdominal contraction with Pilates breathing. The results showed that squats with abdominal contraction associated with Pilates breathing resulted in increased sEMG for the rectus femoris, biceps femoris, and tibialis anterior muscles during the flexion phase, increasing the movement stability. These findings differ from the results presented in the present study, which showed less muscle excitation when performing isotonic contractions at varying load levels. The better neuromuscular efficiency indices observed in the present study when muscle contraction was associated with Pilates breathing may reflect greater neuromuscular efficiency--despite lower electrical excitation, the muscles were able to perform the proposed exercise with the same load levels. These findings suggest that the practice of Pilates breathing leads to the more efficient recruitment of motor units, which allows force generation and joint stabilization with less neural effort, resulting in greater energy savings during exercise. The results of the present study are similar to those presented in [19], which included 15 women who practiced Pilates and 15 women who did not. The participants' right and left multifiidus muscles were evaluated with electromyography to estimate the neuromuscular efficiency. The results related that, although no difference in sEMG was observed between the groups, higher values of the peak isometric torque and neuromuscular efficiency were observed in Pilates practitioners, suggesting that the Pilates breathing practice is effective in training spinal muscles and improving the neuromuscular efficiency in women. A physiological hypothesis that justifies these results is the notion that Pilates breathing increases the volume and oxygenation levels, and it can be used to support any exercise program to provide a physiological environment that is susceptible to better muscle recruitment. This is supported by our findings and the results previously reported [6; 18; 20]. The principle of Pilates breathing is that the individual controls their breathing by performing specific force movements only during expiration, making it slower and deeper; these actions can lead to cardiometabolic and sympathetic flow changes dependent on breathing patterns [21]. A study with 27 participants aged between 20 and 27 years [22], which compared lower-limb neuromuscular responses to postural disturbances during spontaneous and slow breathing, showed that slow breathing shortened the latency of sEMG in lower-limb muscles during postural disturbances when compared to spontaneous breathing, Thus, slow breathing decreases sympathetic nervous system activity, redistributes blood circulation to the working muscles, and affects the metabolism of skeletal muscle cells and membranes, which can have a direct impact on skeletal muscle performance, such as the contraction velocity and strength. Thus, deep and slow breathing techniques can impact muscle performance. However, the observed improvements in neuromuscular efficiency may not be universally applicable.