## 3 Results  
Multicriterial repeated measures ANOVA indicated significant differences for main effects (Muscle F = 23.84, \(p<0.0001\), \(\eta\)2 = 0.20; Speed F = 537.58, \(p<0.0001\), \(\eta\)2 = 0.81; Body weight relief F = 1170.49, \(p<0.0001\), \(\eta\)2 = 0.75) and interactions (Body weight relief \(\times\) Muscle F = 7.91, \(p<0.0001\), \(\eta\)2 = 0.076; Body weight relief \(\times\) Speed F = 94.61, \(p<0.0001\), \(\eta\)2 = 0.43; Body weight relief \(\times\) Muscle \(\times\) Speed F = 3.47, \(p<0.0001\), \(\eta\)2 = 0.098). No significant differences were found for the interaction Muscle \(\times\) Speed (F = 1.56, \(p=0.099\), \(\eta\)2 = 0.047). To verify between which interactions significant differences occurred, multiple comparisons post hoc Bonferroni tests were applied. As a result of the conducted analyses, a clear trend was observed. In each of the analyzed muscles, along with the increasing relief, the muscle tension value also decreased. However, more importantly, the dynamics of the tension decrease were significantly greater at higher speeds. The observed trend is presented in Figure 1.  
For the gastrocnemius muscle, descriptive statistics are presented in Table 1. At a running speed on a treadmill of 6 km/h, significantly higher MVIC results [%] were found for 100% Body weight relief (m = 11.29 \(\pm\) 1.50) compared to 25% Body weight relief (m = 8.98 \(\pm\) 1.53; \(p=0.029\); d = 1.52). In the case of other interactions, no differences were found to be \(p>0.05\). At a running speed on a treadmill of 10 km/h, statistically significantly higher MVIC results [%] were found only for 100% Body weight relief (m = 16.75 \(\pm\) 2.73) compared to 50% Body weight relief (m = 13.45 \(\pm\) 1.02, \(p<0.0001\), d = 1.60) and compared to 25% Body weight relief (m = 12.71 \(\pm\) 1.80, \(p<0.0001\), d = 1.75). In the case of other interactions, no differences were found to be \(p>0.05\). At a running speed on a treadmill of 14 km/h, statistically significantly higher MVIC results [%] were found for 100% Body weight relief (m = 22.55 \(\pm\) 3.41) compared to 75% Body weight relief (m = 19.11 \(\pm\) 2.82, \(p<0.0001\), d = 1.10), 50% Body weight relief (m = 17.58 \(\pm\) 2.09 \(p<0.0001\) d = 1.76), and 25% Body weight relief (m = 15.99 \(\pm\) 1.85; \(p<0.0001\) d = 2.39). No significant differences were found between 75% and 50% and between 50% and 25% Body weight relief at \(p>0.05\). At a running speed on a treadmill of 18 km/h, significantly higher MVIC results [%] were found for 100% Body weight relief (m = 28.51 \(\pm\) 3.37) compared to 75% Body weight relief (m = 24.90 \(\pm\) 3.40 \(p<0.0001\); d = 1.07), 50% Body weight relief (m = 22.04 \(\pm\) 3.32 \(p<0.0001\); d = 1.93) and 25% Body weight relief (m = 19.92 \(\pm\) 2.67; \(p<0.0001\); d = 3.67). There were only no significant differences between 50% and 25% Body weight relief. For the tibialis anterior muscle, descriptive statistics are presented in Table 2. At a treadmill running speed of 6 km/h, statistically significantly higher MVIC results [%] were found for 100% Body weight relief (m = 11.87 \(\pm\) 1.65) compared to 50% Body weight relief (m = 9.58 \(\pm\) 1.62; \(p\) = 0.032; d = 1.40) and compared to 25% Body weight relief (m = 9.25 \(\pm\) 1.54; \(p\) = 0.0014; d = 1.64). In the case of other interactions, no differences were found to be \(p>0.05\). At a running speed on a treadmill of 10 km/h, statistically significantly higher MVIC results [%] were found for 100% Body weight relief (m = 18.43 \(\pm\) 2.68) compared to 75% Body weight relief (m = 15.92 \(\pm\) 2.31; \(p\) = 0.0044; d = 1.00) compared to 50% Body weight relief (m = 14.08 \(\pm\) 2.10; \(p\) < 0.0001; d = 1.81) and compared to 25% Body weight relief (m = 12.55 \(\pm\) 2.04; \(p\) < 0.0001; d = 2.47). In the case of other interactions,