# There Is No Cross Effect of Unstable Resistance Training on Power Produced during Stable Conditions
## 3 Results
### Pre-Post Training Changes in Upper and Lower Body Muscle Power  
Results of upper and lower body muscle power under unstable and stable conditions before and after 4 and 8 weeks of the instability resistance training are presented in Tables 1-4. There were significant improvements of mean power during chest presses on a Swiss ball at weights 20-40 kg after 4 weeks and at weights 20-50 kg after 8 weeks of the instability resistance training. However, no significant changes were observed in mean power produced during bench presses after the same training. Mean power during squats on a BOSU ball increased significantly also after 4 weeks at weights 20-60 kg but not after 8 weeks of the instability resistance training. However, its values did not change significantly when squats were performed on a stable support base after the same training. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Load** & **Pre-Training** & \
\begin{tabular}{c} **After 4** \\ **Weeks a** \\ **Mean (SD)** \\ \end{tabular} &
\begin{tabular}{c} **After 8** \\ **Weeks b** \\ **Mean (SD)** \\ \end{tabular} & \(p\)**-Values a** & **Effect Sizes a** & \(p\)**-Values b** & **Effect Sizes b** \\ \hline
20 & 299.6 (27.1) & 324.7 (32.7) & 366.1 (36.1) & 0.035 & 0.79 & 0.004 & 1.20 \\
30 & 347.8 (37.6) & 373.8 (42.0) & 409.0 (43.8) & 0.030 & 0.97 & 0.008 & 1.13 \\
40 & 381.7 (31.8) & 405.5 (33.1) & 441.8 (35.9) & 0.041 & 0.73 & 0.007 & 1.05 \\
50 & 390.9 (35.8) & 413.4 (35.4) & 455.2 (33.9) & 0.056 & 0.63 & 0.003 & 1.21 \\
60 & 384.4 (35.0) & 397.8 (38.8) & 416.9 (39.9) & 0.363 & 0.49 & 0.286 & 0.49 \\
65 & 317.6 (36.9) & 330.5 (37.6) & 347.7 (36.5) & 0.421 & 0.35 & 0.301 & 0.46 \\
70 & 222.9 (38.0) & 237.6 (42.1) & 253.7 (44.8) & 0.351 & 0.49 & 0.345 & 0.37 \\ \hline \hline \end{tabular}  
*–Changes in Mean Power before and after 4-Week Training, b–Changes in Mean Power from 4-Week to 8-Week Training.  
\end{table} 
Table 1: Mean power (W) during chest presses on a Swiss ball prior to and after 4 and 8 weeks of instability resistance training. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Load** & **Pre-Training** & \
\begin{tabular}{c} **After 4** \\ **Weeks a** \\ **Mean (SD)** \\ \end{tabular} &
\begin{tabular}{c} **After 8** \\ **Weeks b** \\ **Mean (SD)** \\ \end{tabular} & \(p\)**-Values a** & **Effect Sizes a** & \(p\)**-Values b** & **Effect Sizes b** \\ \hline
20 & 312.1 (33.7) & 327.4 (34.5) & 350.0 (43.2) & 0.341 & 0.45 & 0.004 & 0.58 \\
30 & 365.2 (35.4) & 380.6 (33.6) & 400.9 (39.5) & 0.333 & 0.45 & 0.311 & 0.55 \\
40 & 396.7 (41.8) & 421.9 (43.2) & 443.4 (42.8) & 0.254 & 0.59 & 0.276 & 0.50 \\
50 & 430.1 (37.6) & 450.9 (40.5) & 471.8 (41.6) & 0.309 & 0.53 & 0.298 & 0.51 \\
60 & 448.3 (43.5) & 470.1 (42.4) & 487.4 (45.2) & 0.263 & 0.51 & 0.293 & 0.39 \\
65 & 421.8 (36.5) & 435.3 (40.4) & 449.0 (46.3) & 0.360 & 0.35 & 0.408 & 0.32 \\
70 & 335.5 (36.0) & 348.2 (33.5) & 356.6 (32.7) & 0.414 & 0.53 & 0.570 & 0.25 \\
75 & 246.9 (34.3) & 263.1 (35.3) & 270.1 (31.9) & 0.288 & 0.47 & 0.581 & 0.21 \\ \hline \hline \end{tabular}  
*–Changes in Mean Power before and after 4-Week Training, b–Changes in Mean Power from 4-Week to 8-Week Training.  
\end{table} 
Table 2: Mean power (W) during bench presses prior to and after 4 and 8 weeks of instability resistance training.