## 4 Discussion  
The results of the current study suggest that the IKE test is a sensitive evaluation to detect changes in the lower-limb strength of institutionalized older adults produced by training and inactivity periods. This finding supports the inclusion of the IKE test as a valid and practical evaluation in nursing homes and clinical settings. Before including a test in an evaluation battery, practitioners should first analyze its sensitivity. Certainly, a change in any physical capacity should only be considered a real change if it is larger than the variability of the protocol implemented [46], which in turn includes the biological variability of the participant and the error of the device used [47]. The current study found that the IKE test was sensitive enough to detect the group changes generated in institutionalized older adults over 70 years old after both the 4-week training and the 14-week inactive period. However, when individual changes were  
Figure 3: Individual (bars) and group (horizontal black line) changes in the IKE test after the Vivifrail program. The yellow-shaded range represents the SEM of the IKE test recently reported for older adults. The individual changes that the IKE test was able to detect are represented by green (increase) and red (decrease) bars, while blue bars mean cases whose increase/decrease in performance did not exceed the SEM of the test. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Outcome** & **N (\%)** & \
\begin{tabular}{c} **Pre-Inactive** \\ **Period (T1)** \\ \end{tabular} &
\begin{tabular}{c} **Post-Inactive** \\ **Period (T2)** \\ \end{tabular} & **ES (T1-T2)** \\ \hline
**Functional capacity** & & & & \\ SPPB (score) & 15 (100) & 7.10 (3.60) & 6.1 (3.8) & 0.26 \({}^{*}\) \\
5 rep STS (s) & 9 (60) & 12.47 (2.92) & 16.61 (7.13) & 0.72 \\ Relative power STS (W/kg) & 9 (60) & 2.54 (0.81) & 2.12 (1.04) & 0.43 \\
4m gait speed (s) & 14 (93) & 6.30 (6.59) & 8.84 (9.08) & 0.36 \\ TUG (s) & 14 (93) & 19.00 (9.74) & 24.66 (17.53) & 0.39 \({}^{*}\) \\
**Handgrip strength** & & & & \\ Dominant (kg/kg) & 15 (100) & 0.23 (0.10) & 0.23 (0.09) & 0.01 \\ Non-dominant (kg/kg) & 15 (100) & 0.24 (0.09) & 0.24 (0.09) & 0.02 \\ \hline \hline \end{tabular}  
* N, number of participants; STS, sit-to-stand; SFPB, Short Physical Performance Battery; TUG, Timed Up and Go; ES, effect size expressed as Hedge’s g; significant changes at \(p<0.05\)\({}^{*}\).  
\end{table} 
Table 3: Changes in physical assessment after the 14-week inactive period. interpreted, we detected a superior sensitivity of the IKE test when conducted for the non-dominant leg (\(\geq\)73% individual changes detected) compared to the dominant one (\(\geq\)40% individual changes detected) (Figures 2 and 3). Since the changes in the lower-limb strength generated after the training and inactive periods were similar for both legs (difference of \(\leq\)0.03 N/kg), the higher sensitivity of this IKE evaluation for the non-dominant leg could be explained by its lower variability when implemented for this leg (\(\pm\)0.15 N/kg) compared to the dominant one (\(\pm\)0.26 N/kg) [22]. Considering these findings, future investigations implementing the IKE test for determining changes in lower-limb strength should use the specific variability threshold for each leg instead of a common one to adequately interpret the effects of the intervention conducted. Importantly, a strength of the current study was the use of a previously determined variability threshold [22] in older adults with an age (<2.6 years difference), BMI (<0.8 difference), and physical level (<1.7 points difference in the SPPB) similar to those included in both periods of this study (Table 1). Nevertheless, future studies implementing the IKE test for evaluating older adults with characteristics far from those described above (e.g., healthy community-dwelling older adults or people with Alzheimer's disease) should use the variability threshold specific to that population and then apply it in practice [48].