## 3 Results  
No significant differences were found between groups during the pre-intervention measurement (\(p\geq 0.05\)) except for leg press RFD (see below). Results for body mass, 1-RM strength, isometric RFD, and isometric PF are presented in Table 1. Body mass remained unaltered after IRRG (\(p\) = 0.120, \(\eta^{2}\) = 0.160) and after TG (\(p\) = 0.556, \(\eta^{2}\) = 0.025). Leg press 1-RM was significantly increased after IRRG by 20.4 \(\pm\) 5.9% (\(p\) < 0.001, \(\eta^{2}\) = 0.814) and after TG by 20.4 \(\pm\) 10.8 (\(p\) < 0.001, \(\eta^{2}\) = 0.835), while there was no significant difference between groups (\(p\) = 0.417, \(\eta^{2}\) = 0.048). ANCOVA revealed that RFD remained unaltered after both IRRG and TG at all time frames of the force-time curve (\(p\) > 0.05). However, IRRG induced greater percentage increases during 30 ms, 50 ms, and 80 ms compared to TG (RFD\({}_{\rm 30 ms}\) IRRG: 43.6 \(\pm\) 56.8% vs. TG: \(-\)3.3 \(\pm\) 14.5%, \(p\) = 0.016, \(\eta^{2}\) = 0.360, RFD\({}_{\rm 50 ms}\) IRRG: 44.3 \(\pm\) 58.9% vs. TG: \(-\)1.1 \(\pm\) 16.6%, \(p\) = 0.023, \(\eta^{2}\) = 0.323, RFD\({}_{\rm 80 ms}\) IRRG: 33.4 \(\pm\) 47.3% vs. TG: \(-\)5.9 \(\pm\) 15.1%, \(p\) = 0.042, \(\eta^{2}\) = 0.263). Isometric PF was significantly increased over-time following IRRG by 17.4 \(\pm\) 8.5% (\(p\) < 0.001, \(\eta^{2}\) = 0.638) and TG by 12.3 \(\pm\) 8.7% (\(p\) < 0.001, \(\eta^{2}\) = 0.547), with no significant difference between groups. Results from VL muscle architecture, VI thickness and CSA of quadriceps are presented in Table 2. VL muscle thickness was increased significantly over-time following TG (from 2.6 \(\pm\) 0.4 cm to 2.7 \(\pm\) 0.4 cm, \(p\) = 0.043, \(\eta^{2}\) = 0.262), as well as after IRRG (from 2.5 \(\pm\) 0.3 cm to 2.6 \(\pm\) 0.2 cm, \(p\) = 0.048, \(\eta\)2 = 0.260). VL fascicle angle remained unchanged after IRRG (\(p\) = 0.983, \(\eta^{2}\) = 0.000) and TG (\(p\) = 0.366, \(\eta^{2}\) = 0.059); however, VL fascicle length increased only after IRRG from 8.3 \(\pm\) 0.9 cm to 8.7 \(\pm\) 1.1 cm (\(p\) = 0.044, \(\eta^{2}\) = 0.260) and the percentage increase was significant greater compared to TG (IRRG: 4.8 \(\pm\) 6.1% vs. TG: \(-\)3.9 \(\pm\) 5.4%, \(p\) = 0.009, \(\eta^{2}\) = 0.393). VI muscle thickness remained unaltered after IRRG (\(p\) = 0.442, \(\eta^{2}\) = 0.043) and TG (\(p\) = 0.813, \(\eta^{2}\) = 0.004). When VL and VI muscle thickness were combined, significant increase was found for IRRG (3.8 \(\pm\) 3.0%, \(p\) = 0.010, \(\eta^{2}\) = 0.387) and TG (3.2 \(\pm\) 4.0%, \(p\) = 0.013, \(\eta^{2}\) = 0.365), with no difference between groups (\(p\) = 0.330, \(\eta^{2}\) = 0.068). Total quadriceps CSA was increased significantly after IRRG (14.3 \(\pm\) 9.5%, \(p\) < 0.001, \(\eta^{2}\) = 0.611) and TG (12.5 \(\pm\) 7.6%, \(p\) = 0.002, \(\eta^{2}\) = 0.512), with no significant difference between groups (\(p\) = 0.690, \(\eta^{2}\) = 0.012). In addition, both groups increased VL CSA (23.4 \(\pm\) 17.9%, \(p\) < 0.001, \(\eta^{2}\)= 0.599 and 16.7 \(\pm\) 12.7%, \(p\) = 0.004, \(\eta^{2}\) = 0.458, for IRRG and TG, respectively) and VI CSA (15.7 \(\pm\) 9.6%, \(p\) < 0.001, \(\eta^{2}\) = 0.548 and 12.1 \(\pm\) 9.6%, \(p\) = 0.013, \(\eta^{2}\) = 0.367, for IRRG and TG, respectively), but only TG increased VM CSA by 19.7 \(\pm\) 11.5% (\(p\) = 0.003, \(\eta^{2}\) = 0.468). No significant change was observed for the CSA of RF for any of the groups.