# Evaluation of Thorax Diameter Changes through Trunk Morphology and Different Running Intensities
## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{3}{c}{**Estimated Marginal Means—MTC * Morphology Group**} \\ \hline \multirow{2}{*}{**Morphology Group**} & \multirow{2}{*}{**MTC**} & \multirow{2}{*}{**Mean**} & \multirow{2}{*}{**SE**} & \multicolumn{2}{c}{**95\% Confidence Interval**} \\ \cline{5-6}  & & & & **Lower** & **Upper** \\ \hline \multirow{3}{*}{3} & MTC\_45\% & 3.18 \(\circ\) & 0.358 & 2.43 & 3.93 \\  & MTC\_70\% & 4.29 & 0.392 & 3.47 & 5.11 \\  & MTC\_85\% & 5.07 & 0.45 & 4.13 & 6.01 \\ \hline \multirow{3}{*}{Total} & MTC\_45\% & 3.34 \(\circ\)* & 0.208 & 2.91 & 3.77 \\  & MTC\_70\% & 4.7 & 0.235 & 4.21 & 5.18 \\ \cline{1-1}  & MTC\_85\% & 5.36 & 0.263 & 4.81 & 5.91 \\ \hline \hline \end{tabular} Key: SE: standard error; MTC_45%: IP of mediolateral thorax cross-section at a running intensity of 45% HRR, MTC_70%: IP of mediolateral thorax cross-section at a running intensity of 70% HRR; MTC_85%: IP of mediolateral thorax cross-section at a running intensity of 85% HRR * Statistical difference between IP at 45% HRR and 70% HRR * Statistical difference between IP at 45% HRR and 85% HRR.  
\end{table} 
Table 5: _Cont._those obtained by other authors analysing breathing thorax deformation in still postures such as sitting or lying [28]. In the present experiment, we have observed that higher changes of IP on thorax cross-sections happened in the anteroposterior, followed by the mediolateral and the craniodal cross-sections. This is partially in agreement with the literature as it is known that bigger changes in the volume of the thorax are produced in the craniodal cross-section followed by the anteroposterior and mediolateral; all these changes are caused mainly by the diaphragm and the breathing muscles [3]. The diaphragm is a dome-shaped muscle that closes the thorax from the bottom [39]. In breathing, diaphragm contraction pushes the ribs outwards, generating an expansion of the thorax on the anteroposterior and mediolateral cross-sections, making those cross-sections longer and increasing the ribcage volume [39]. When the diaphragm is contracted, the dome's shape is flattened, increasing thorax volume for the expansion of the lungs, and enhancing the craniodal cross-section [39]. The rise in the craniodal cross-section cannot be measured completely with the technique used in the present work because the reflective markers were placed on osseous anatomic locations. This might have influenced our lower results in the crani caudal cross-section compared with the literature. The anteroposterior and the mediolateral cross-sections between maximum inspiration and expiration were evaluated by [PERSON] et al. in 2018 who mainly dismissed the craniodal cross-section, finding changes of 2.51-2.79 cm (\(\pm\)1.03 cm) on the anteroposterior cross-section and 2.08-2.36 cm (\(\pm\)0.75 cm) on the mediolateral [21]. Interestingly, our results, which have been expressed as a normalized increment, agree with the earlier data in the sense that the anteroposterior cross-section increases more than the mediolateral. However, if we express them in length units, we can see a smaller increase of 0.97-1.55 cm (\(\pm\) 0.50 cm) on the anteroposterior and 1.00-1.61 cm (\(\pm\) 0.61 cm) on the mediolateral cross-section. The expansion of the thorax increases when the demand for exercise is enhanced but does not reach an expansion similar to that produced when a maximum inspiration and exhale occur. This difference could be explained by the breathing frequency behaviour during high-intensity exercise (67-73 breaths/min at the peak) [40]. In this sense, [PERSON] et al. (2020) demonstrated that breathing frequency increases with the intensity of activity, allowing enhanced air volume and oxygen exchange during exercise [40]. When breathing frequency rises, the thoracic ROM oscillates less because inspiration and expiration times are reduced [3].