## 4 Discussion
The values for that study are much lower (62 \(\pm\) 42 N vs. 980 \(\pm\) 348 N) than our values. This difference could lie in the fact that [PERSON] et al. calculated by methodological differences using different instruments (gravitational force of body weight vs. force plate) and populations (predominantly female older adults vs. both sexes). However, when considering other knee-hip extension movements (i.e., leg press, Nottingham power rig), our results are similar to those found in the literature (females: 751 N vs. 785 N, males: 1859 vs. 2145 N) [8; 29]. The F0 between the 5 STS and ISO tests showed a significant difference (\(p<0.001\)) and bias (bias= 670 N, \(p<0.001\)) with a high limit of agreement (L.O.A.= [87 to 1300 N]) and yet a high correlation between measures (r = 0.71). We speculate that the difference between the expression of lower limbs' maximum muscle strength between tests is due to the difference in muscle action (in terms of neuromuscular and biomechanical characteristics, e.g., muscle coordination of single vs. multi-joint movements and different contraction lengths) [8] required by the two movements (single-joint vs. multi-joint), and difference in the applied load (weight-bearing versus non-weight-bearing) between tests [13]. These discrepancies could have affected the slope of the force-velocity relationships and consequently the computation of F0. Moreover, our results differ from the only previous study that compared F0 values from these tests [8; 29] and found no difference and a low correlation between tests. Again, this discrepancy could be related to methodological differences cited in the previous paragraph (i.e., methodological differences, indirect force estimation based on body mass) as well as to the high variability of measures in [PERSON] et al. [12]. In summary, the measures of F0 as derived from 5 STS, while highly correlated with ISO, are not an accurate and precise surrogate of the maximum isokinetic strength of the unilateral lower limb. As previously mentioned regarding F0 measures, ISO maximum power (Pmax) data are typically computed based on peak rather than mean force data [5; 26; 27]. Therefore, it is not surprising that our Pmax values are lower than those reported in the literature in a comparable population [5; 26; 27]. Interestingly, the results derived from our ISO test and calculated from mean force (194 \(\pm\) 54 W) (Figure 4) were similar to those computed using mean force values in young females [20]. The bilateral STS Pmax found in this study (333 \(\pm\) 104 W) was closer to that found by other authors in bipedal multi-joint exercises (e.g., leg press) (\(\sim\)350 W) [2; 11] in a comparable population. In comparison with the only other study that computed unilateral STS Pmax in young women (187 \(\pm\) 147 W) [12], we found similar values with a considerably lower variability (200 \(\pm\) 63 W). The comparison of Pmax between the ISO and 5 STS tests showed a non-significant difference and a high correlation (\(p\) = 0.259, r = 0.84). Bland-Altman analysis reported a non-significant and constant bias (bias = 5.7 W, \(p\) = 0.259) with small limits of agreement (L.O.A. = [\(-\)60 to 71 W]). Our correlation results between 5 STS- and ISO-derived Pmax are in contrast with those found in the literature (r = 0.31) [12]. This discrepancy may lie in the factors discussed above for F0 and in the high variability (CV \(>\) 75%) of the 5 STS-derived maximal power [12]. In summary, the F-v profiling of 5 STS appears an accurate and precise alternative to ISO for the measurement of the maximum power of the lower limbs. Maximum (V0, 7.5 \(\pm\) 0.9 rad \(\times\) s\({}^{-1}\)) and optimal (Vopt, 3.8 \(\pm\) 0.4 rad \(\times\) s\({}^{-1}\)) angular velocities for the isokinetic test are considered, and these values are similar to [PERSON] et al. (7.1 \(\pm\) 2.1 and 3.6 \(\pm\) 0.8 rad \(\times\) s\({}^{-1}\), respectively) who, like us, used a linear F-v profiling.