## 3 Results
### Maximum Inspiratory and Expiratory Pressure  
Results appear in Table 5. In certain groups, significant differences in values measured between the 1 st and the 2 nd attempts and between the 4 th and the 5 th attempts emerged (data not shown). The mean of the values measured at the 2 nd to 4 th attempt was, therefore, calculated. In the course of measurements of maximum inspiratory pressure, men were able to attain on average 91.0% and women 95.8% of the predicted value. For the maximum expiratory pressure, men reached an average at 70.9% and women 81.3% of the expected value. There was a statistically significant difference in absolute values measured in men and women, where men reached higher maximum inspiratory and expiratory pressure than women. There was no significant difference seen between age subgroups in either MIP or MEP.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Variable** & **Sex** & **Total** & **18–29 Years** & **30–49 Years** & \(\geq\)**50 Years** & **\(p\)-Value Age** & **\(p\)-Value Sex** \\ \hline \multirow{3}{*}{Prone position \({}^{\dagger}\)} & Male & 25.7 \(\pm\) 5.0 & 28.5 \(\pm\) 4.1 & 25.6 \(\pm\) 3.9 & 20.5 \(\pm\) 6.0 & \multirow{3}{*}{0.002} & \multirow{3}{*}{0.319} \\  & Female & 24.4 \(\pm\) 5.6 & 26.1 \(\pm\) 5.8 & 24.8 \(\pm\) 5.5 & 20.2 \(\pm\) 3.5 & & \\  & Post-hoc test (age) & b & b & a & & \\ \hline \multirow{3}{*}{Sitting position \({}^{\dagger}\)} & Male & 80.0 \(\pm\) 18.0 & 78.9 \(\pm\) 23.1 & 83.4 \(\pm\) 15.8 & 72.1 \(\pm\) 12.5 & \multirow{3}{*}{0.066} & \multirow{3}{*}{<0.001} \\  & Female & 55.9 \(\pm\) 17.8 & 62.2 \(\pm\) 18.3 & 57.0 \(\pm\) 16.2 & 39.9 \(\pm\) 14.0 & & \\ \hline \multirow{3}{*}{Standing position \({}^{\dagger}\)} & Male & 62.0 \(\pm\) 13.9 & 61.9 \(\pm\) 13.4 & 64.6 \(\pm\) 15.2 & 54.6 \(\pm\) 9.0 & \multirow{3}{*}{0.074} & \multirow{3}{*}{<0.001} \\  & Female & 43.1 \(\pm\) 12.6 & 47.9 \(\pm\) 12.2 & 43.1 \(\pm\) 11.6 & 33.3 \(\pm\) 13.0 & & \\ \hline \multicolumn{7}{l}{Data are expressed as mean \(\pm\) standard deviation. Post-hoc tests: a, b—same letters marking values of categories within given row denote mutually statistically not different groups. \({}^{\dagger}\) Maximal isometric lower back extensor strength (calculated from the mean value of the 2 nd to 5 th attempts), results expressed in kilograms.} \\ \multicolumn{7}{l}{The consistency of the data, expressed as the repeatability of measurements in one session, was excellent (ICC 0.975-0.996) for all six successive attempts and the 2 nd to 5 th attempts in all three postural positions (Table 3).} \\ \end{tabular}
\end{table}
Table 2: Maximal isometric lower back extensor strength: results.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Characteristics** & **All Attempts \({}^{\ddagger}\)** & **2 nd–5 th Attempt \({}^{\ddagger}\)\({}^{\ddagger}\)** \\ \hline \multicolumn{3}{l}{Number of participants} \\ \multicolumn{3}{l}{evaluated} & \(n\) & 60 & 60 \\ \hline \multirow{3}{*}{Prone position} & ICC (95\% CI) & 0.978 (0.968–0.986) & 0.975 (0.963–0.984) \\  & \(p\)-value & \textless{}0.001 & \textless{}0.001 \\ \hline \multirow{3}{*}{Sitting position} & ICC (95\% CI) & 0.995 (0.992–0.997) & 0.995 (0.992–0.997) \\  & \(p\)-value & \textless{}0.001 & \textless{}0.001 \\ \hline \multirow{3}{*}{Standing position} & ICC (95\% CI) & 0.996 (0.994–0.997) & 0.996 (0.994–0.997) \\  & \(p\)-value & \textless{}0.001 & \textless{}0.001 \\ \hline \hline \end{tabular} \(n\): number of individuals; ICC: intraclass correlation coefficient; CI: confidence interval. \({}^{\ddagger}\) repeatability of measurements at the first visit for all 6 attempts. \({}^{\ddagger}\) repeatability of measurements at the first visit for the 2 nd to 5 th attempts.  
\end{table}
Table 3: Maximal isometric lower back extensor strength: repeatability.