*3.4. Analysis of Differences in MI Ability as Measured by the MIQ-3 Concerning Sex and Age*

The mixed factorial ANOVA indicated in the case of the comparison according to sex in the three subscales, i.e., internal visual, external visual, and kinesthetic, that there was no significant interaction between the within-subjects factor (the two measurements taken) and the between-subjects factor (sex). There was also no significant effect of the inter-subject factor, but there was a significant effect of the intra-subject factor. Both sexes behaved similarly, with significantly higher values in the second session than in the first session. There were no differences between males and females in either measurement (Table 4).

**Table 4.** The mixed factorial analysis of variance (ANOVA) results of the differences in motor imagery (MI) ability measured through the MIQ-3, according to sex.



*n*, sample size; SD, standard deviation; CI, confidence interval; *p*, statistical significance; F, Fisher; ηp2, partial eta-squared coefficient.

Regarding the differences according to MI age range (MIQ-3) in the three subscales, namely internal visual, external visual, and kinesthetic, it was found that there was a significant interaction between the within-subjects factor (the two measurements taken) and the between-subjects factor (age range). There was also a significant effect of the inter-subject and intra-subject factors. The three age ranges behaved similarly in the three subscales (internal visual, external, and kinesthetic), with significantly higher values in the second session compared to the first (Table 5).

**Table 5.** The mixed factorial ANOVA results of differences in MI ability as measured by the MIQ-3, by age range.



*n*, sample size; SD, standard deviation; CI, confidence interval; *p*, statistical significance; F, Fisher; ηp2, partial eta-squared coefficient.

On the other hand, there were statistically significant differences between the values of the three age ranges in the internal visual and kinesthetic subscales, with the 70–79 age group presenting the highest values, followed by the 80–89 age group and, finally, the 90–100 age group with the lowest values. In the external visual subscale, the group aged 70 to 79 years presented the highest values, followed by the group aged 80 to 89 years and, finally, the group aged 90 to 100 years with the lowest values, with there being significant differences between the group aged 70 to 79 years and the other two groups (80 to 89 and 90 to 100 years). However, the differences observed were not significant between the 80–89 and 90–100 age groups (Table 5).

#### *3.5. Analysis of Temporal Congruence Concerning Sex and Age*

Mixed factorial ANOVA was performed to compare, according to sex, the three movements corresponding to temporal congruency: elbow flexion-extension, knee flexionextension, and getting up and sitting down on the chair. The results obtained indicated that in the case of the first two movements (elbow and knee flexion-extension), there was no significant interaction between the intra-subject factor in the two measurements (performed and imagined) and the inter-subject factor (sex). There was also no significant effect of the intra-subject factor, but there was a significant effect of the inter-subject factor, F(1, 58) = 5.48; *p* = 0.023; η<sup>p</sup> <sup>2</sup> = 0.086 in the elbow flexion-extension movement and F(1, 58) = 10.06; *p* = 0.002; ηp <sup>2</sup> = 0.148 in the knee flexo-extension movement. Both sexes behaved differently. In men, the values of the executed measurement (elbow flexion-extension M = 3.71, SD = 0.42; knee flexion-extension M = 4.06, SD = 0.41) were higher than those of the imagined measurement in both subscales (elbow flexion-extension M = 3.64, SD= 0.33; knee flexion-extension M = 3.90, SD = 0.38). In women, the values of the executed measurement (M = 3.96, SD = 0.48) were slightly higher than those of the imagined measurement in the elbow movement (M = 3.94, SD = 0.60), and the values of the executed measurement (M = 4.06, SD = 0.41) were slightly lower than the imagined one in the knee movement. In both movements, differences (*p* < 0.05) were found between men and women in both the executed and imagined measurements, with women's values being significantly higher. In the intra-group comparison of the two movements of the two measurements carried out (the executed and the imagined), it was found that neither in men nor in women were there significant differences between the two measurements.

As for the get up and sit down on the chair movement, this mixed factorial ANOVA showed no significant interaction between the intra-subject and inter-subject (sex) factors, but there was a significant effect of the inter-subject factor F(1, 58) = 6.72; *p* = 0.012; η<sup>p</sup> <sup>2</sup> = 0.104 and the intra-subject factor F(1, 58) = 54.23; *p* < 0.001; η<sup>p</sup> <sup>2</sup> = 0.483. Both sexes behaved similarly, with higher values for the imagined measurement (male M = 5.10, SD = 0.71; female M = 5.47, SD = 0.60) than for the executed measurement (male M = 4.61, SD = 0.41; female M = 4.93, SD = 0.55). There were statistically significant differences (*p* < 0.05) between men and women in the two measurements, with women having significantly higher values. In the intra-group comparison of the two measurements carried out, we obtained that in both men and women, there were significant differences (*p* < 0.05) between the two measurements, with the imagined scores being significantly higher.

Next, the results obtained for temporal congruence were analyzed, i.e., the difference in the three movements of elbow flexion-extension, knee flexion-extension, and getting up and sitting down on the chair, comparing the two measurements (executed less imagined) concerning sex. The Mann–Whitney U-test was used for all movements. These analyses showed no gender differences in the three movements (Table 6).


**Table 6.** Temporal congruency concerning sex.

Mann–Whitney U-test was used; Q1–Q3, first through third quartiles; r, Rosenthal's "r"; *p*, statistical significance.

Mixed factorial ANOVA was performed to analyze, according to age range (intersubject factor), the two measurements (performed and imagined) of the three movements corresponding to temporal congruency: elbow flexion-extension, knee flexion-extension, and getting up and sitting down on the chair. These analyses showed a significant interaction between movement execution and imagery (intra-subject factor) and age range (inter-subject factor) in the elbow flexion-extension (F(2, 57) = 9.68, *p* < 0.001; η<sup>p</sup> <sup>2</sup> = 0.253) and knee flexion-extension (F(2, 57) = 5.97, *p* = 0.004; η<sup>p</sup> <sup>2</sup> = 0.173). There was also a significant effect of the inter-subject factor (elbow flexion-extension F(2, 57) = 10.36, *p* < 0.001; ηp <sup>2</sup> = 0.267; knee flexion-extension F(2, 57) = 6.42, *p* = 0.003; η<sup>p</sup> <sup>2</sup> = 0.184) but no significant effect of the intra-subject factor. Thus, the three age ranges did not behave similarly in both the elbow flexion-extension movement and the knee flexion-extension movement. While the values of the imagined measurement decreased compared to the executed one in the 80–89 years and 90–100 years age groups, the values increased in the 70–79 years age group. In both movements, there were significant differences (*p* < 0.05) between the value of the executed and imagined measurement in the 70–79 years (the value of the imagined measurement being higher) and 90–100 years (the value of the executed measurement being higher in this case), while in the 80–89 years group, there were no differences between the two measurements. On the other hand, in the executed measurement in both the elbow flexion-extension and knee flexion-extension movements, there were statistically significant differences (*p* < 0.05) between the three age ranges, with the 70–79 age group showing the lowest values, followed by the 80–89 age group and, finally, the 90–100 age group showing the highest values. However, in the imagined measurement of the elbow flexion-extension movement, there were only significant differences (*p* < 0.05) between the 70–79 years and 90–100 years groups, with no significant differences between the other groups, and in the knee flexion-extension movement, there were no significant differences between any of the three age ranges.

Finally, in the movement of getting up and sitting down from a chair, there was a significant effect of the intra-subject factor F(1, 57) = 64.25, *p* < 0.001; η<sup>p</sup> <sup>2</sup> = 0.530 (the two measurements taken, executed, and imagined) and inter-subject factor F(2, 57) = 20.47, *p* < 0.001; η<sup>p</sup> <sup>2</sup> = 0.418 (the three age groups considered), but there was no significant interaction between the two factors. In the three age ranges, in this movement of standing up and sitting down, there were significant differences (*p* < 0.05) between the executed and imagined measurement, with higher values for the imagined measurement. On the other hand, in the executed measurement, there were significant differences (*p* < 0.05) between the three age ranges, with the 90–100 age group showing the highest values, followed by the 80–89 age group and, finally, the 70–79 age group with the lowest values of the three. Meanwhile, in the imagined measurement, there were only significant differences between the 70–79 age group and the 90–100 age group.

Next, the results obtained for temporal congruence were analyzed, i.e., the difference in the three movements of elbow flexion-extension, knee flexion-extension, and getting up and sitting down on a chair, comparing the two measurements (performed and imagined) according to age range by carrying out a Kruskal–Wallis ANOVA. There were no differences between the three age ranges compared in temporal congruence in standing and sitting. However, there were significant differences (*p* < 0.05) between the three age ranges in the temporal congruence in elbow flexion-extension and knee flexion-extension movements. Specifically, in elbow flexion-extension, there were significant differences (*p* < 0.05) between the 70–79 age group and the other two groups. In the knee flexion-extension movement, there were significant differences (*p* < 0.05) between the subjects aged 70–79 years and the group aged 90–100 years (Table 7).


**Table 7.** Temporal congruence concerning age.

Q1–Q3, first through third quartiles.

#### **4. Discussion**

The aim of this study was to test the reliability of the Spanish version of the Movement Imagery Questionnaire-3 in 60 institutionalized elderly people. The first translation, cultural adaptation, and validation of the Spanish version of the MIQ-3 [27] have recently been published. This work is focused on healthy young people. For older people, no work has been found that evaluates the reliability of this test or similar questionnaires for older people.

The descriptive analysis of the results obtained in the two measurements made with the questionnaire (test and retest) showed higher values in the second session in the three subscales, which suggests that the participants showed a better ability to imagine measured with the MIQ-3 the second time they took the questionnaire. This could be the result of the MI practice implicit in the development of the first session, in which subjects performed both the questionnaire itself and the imagery tasks related to temporal congruence. This is consistent with the results of the study by Rufino et al. [44], where it was observed that a single MI session already induces use-dependent brain plasticity.

Cronbach's alpha was acceptable for all the values obtained, and none of the items was redundant [37]. In this sense, these results are consistent with Trapero-Asenjo et al. [27] even though the value obtained was lower than in the study by the authors.

Concerning the subscales, the analysis revealed a good internal consistency for both the internal visual subscale (0.615) and the external visual subscale (0.651) and a moderate internal consistency (0.556) for the kinesthetic subscale. These results show that the values obtained were lower than those obtained in the study by Trapero-Asenjo et al. [27], which indicated a high internal consistency for the three subscales, with 0.849 for the internal visual subscale, 0.837 for the external visual subscale, and 0.615 for the kinesthetic subscale. These lower values in the study by Trapero-Asenjo et al. [27] coincide with the lower values obtained in validating the MIQ-3 in Portuguese by Mendes et al. [8].

The test-retest reliability analysis of each of the 12 items that make up the questionnaire by means of the weighted and interpreted kappa coefficient value showed medium, moderate, and substantial degrees of agreement in 8 items. Therefore, these correspond to adequate test-retest reliability values as established in the classification of Landis and Koch in 1977 [38]. These findings partially coincide with the results obtained by Trapero-Asenjo et al. [27], who found moderate to substantial agreement on all 12 items. In contrast, in the present investigation, items 1 and 3 of the internal visual subscale; items 1, 2, and 3 of the external visual subscale; and items 1, 2, and 3 of the kinesthetic subscale showed a medium degree of agreement, i.e., below the values obtained by Trapero-Asenjo et al. [27].

The results of the test-retest reliability analysis of each MIQ-3 subscale by calculating the ICC showed for the external visual subscale an ICC of 0.534 (95% confidence interval (CI) = 0.07, 0.80; *p* < 0.001), in the internal visual subscale a CCI of 0.611 (95% CI = 0.02, 0.83; *p* < 0.001), and the highest value was in the kinesthetic subscale, with a CCI of 0.691 (95% CI = 0.07, 0.90; *p* < 0.001). These values were interpreted according to Weir's criteria [41], showing internal consistency with moderate values in all subscales. These findings are consistent with the results presented by Trapero-Asenjo et al. [27]; however, the values obtained were lower, as the ICC of the three scales were high in the study by Trapero-Asenjo et al. [27], while in this study, the values were moderate.

All these results suggest that the Spanish version of the MIQ-3 is a reliable measure of MI capacity for use in institutionalized elderly people. The study by Suica et al. [29] showed that the questionnaires for assessing MI with the best psychometric properties were the Movement Imagery Questionnaire (MIQ) [45] as well as its versions Movement Imagery Questionnaire—Revised (MIQ-R) [46], MIQ-3, and the Vividness of Movement Imagery Questionnaire (VMIQ-2) [47]. The same study showed that most studies assessing MI had been conducted in a young population [29], thus highlighting the need to validate MI assessment tools in the elderly. On the other hand, of all these questionnaires, only the MIQ-3 and the VMIQ-2 assess MI ability and MI vividness, respectively, in the three subscales of internal visual, external visual, and kinesthetic imagery [26,47]. It has been shown that these three forms of imagery are separate but related constructs [26,46], so the assessment of all three is of particular importance for both research and clinical applicability. Thus, this is the first study to confirm that MI capacity can be reliably assessed in institutionalized elderly people using the Spanish version of the MIQ-3, which currently represents the most suitable questionnaire for assessing MI ability on all three subscales. In clinical applicability, it has been proven that the ability to image can be improved with practice [48]. The results of this study will allow the design of more effective MI programs in the elderly since they not only allow the evaluation of MI through these questionnaires at the beginning of programs with MI but also allow them to monitor changes in the capacity of MI that are happening along the program.

On the other hand, studies have been carried out in which the capacity and vividness of MI in elderly people has been explored through questionnaires and their temporal characteristics through temporal congruence studies. It has been seen that the study of both issues is important, as it was pointed out that the ability to imagine and the temporal congruence are separate constructs and should be evaluated separately because they are affected differently by age [32]. To explore those questions, the present study analyzed the scores of the three subscales of MIQ-3 and three tasks of time congruence according to sex and age in the elderly population.

Thus, regarding the secondary objectives, in the analysis of differences in MI ability measured through the MIQ-3, there were no differences between men and women in the two measurements. These results partially coincide with the findings reported by Campos et al. [31]. They assessed in a sample of adult subjects whether there are age and gender differences by using self-report and a performance-based test, reporting no significant differences between the sexes concerning MI ability even though males scored higher than females.

Regarding the differences according to MI age range (MIQ-3), the analysis of the results suggests that the three age ranges behaved similarly in the three subscales (internal visual, external, and kinesthetic), with significantly higher values in the second session compared to the first. This could be associated with a learning process derived from the execution of the movement.

On the other hand, there were statistically significant differences between the values of the three age ranges in the internal visual and kinesthetic subscales, with the group of septuagenarians presenting the highest values, followed by the group of octogenarians and, finally, the group of nonagenarians and centenarians with the lowest values. In the external visual subscale, the decrease in scores with increasing age was similar to the other two subscales. However, in this case, the significant differences were between the septuagenarian group with respect to octogenarians and nonagenarians to centenarians, but the differences observed were not significant between these last two groups. These results confirm the findings of Subirats et al. [32]. They found that MI ability (measured with the Vividness of Movement Imagery Questionnaire-2 and MI timing using the performances of the real Timed Up and Go (rTUG) test) is affected by age, with a tendency for MI to decrease with age in the present study, with no significant differences between the group of nonagenarians and centenarians with respect to the group of adults aged 70–79 years. They also confirm the results that Mulder et al. [49] obtained, which showed that older participants had slightly worse MI ability (measured with the Vividness of Movement Imagery Questionnaire) than younger participants.

Similarly, they corroborate the findings of Schott [50], whose study examined key characteristics of MI ability in three groups of healthy older men and women (measured with the Movement Imagery Questionnaire, the Controllability of Motor Imagery test, and two different chronometry tests) distributed across three age groups (60–69, 70–79, and ≥80 years) and 40 younger subjects aged 20–30 years. They found that MI ability was better in younger adults compared to older adults aged 70 years and older but not in older adults aged 60–69 years. However, as noted above, IM ability can be improved with practice, and low scores are not exclusive to IM programs [48].

Regarding the differences in temporal congruence, no significant differences were observed concerning the differences between gender. However, there were differences in the time used to perform and imagine the movements. Thus, both sexes took significantly longer to imagine than to execute the movement of sitting down and getting up from the chair, and on the other hand, the men took longer to execute than to imagine the less global movements of flexion-extension of the elbow and knee, whereas the women had very similar results in both moments of the task. Therefore, it seems that in the simplest movements, the imagery of the movement tends to have a shorter duration than the movement itself, while in more global movements, such as getting up and sitting down, the imagery of the movement is reproduced more slowly than the execution of the same movement in the elderly population. The previous study by Saimpont et al. [25] pointed out that temporal congruence in the elderly seems to be more reserved in simple and usual movements, so all these issues should be further explored in future studies.

Regarding the differences in temporal congruence with respect to age, differences were only observed in the elbow and knee flexo-extension movements. In both cases, it was seen that as age increased, the imagery time was significantly reduced compared to the execution time of the same movement. This again suggests that the ability to maintain temporal congruence varies with increasing age. In this sense, Schott et al. [50] observed that from the age of 79, the difference between the values of imagery and execution of the movement increased progressively, so this issue should be further explored in future studies.

#### *Limitations*

To conclude, for the analysis of the study's main objective, the sample of five people per item was adequate [51], and for the study of the characteristics of the imagery, the total sample was also adequate, with a size equal to 60 subjects. However, as a limitation of the study, the sample consisted of 26 participants in the 80–89 age group, 18 subjects in the 90–100 age group, and 16 subjects in the 70–79 age group. It would be desirable to carry out studies with a larger sample in each age range to obtain more representative results for each age group and validate the results in non-institutionalized elderly people.

In the study, the sample was selected based on the absence of cognitive impairment or dementia as well as depressive disorders, traumatic processes in the last 6 months, and treatment with central nervous system suppressant drugs. Thus far, no studies have explored how other health aspects may influence the ability to imagine in older people (high blood pressure, diabetes, vision, and hearing problems, among others). It is suggested that these data could be collected in future studies. Although it is not possible to establish relationships due to the design, this will help to understand the sample's characteristics better.

Finally, it should also be considered that the participants only belong to one center, so the results should not be extrapolated. Therefore, future studies should include larger samples and institutionalized and non-institutionalized elderly in different institutions.

#### **5. Conclusions**

The study allows us to conclude that the Spanish version of the MIQ-3 is a reliable instrument for measuring MI capacity in institutionalized elderly people.

The findings obtained did not demonstrate significant differences in MI ability measured with the MIQ-3 between women and men in this population. However, the results of this study support the hypothesis that MI ability decreases with the increasing age range.

In relation to temporal congruency, the analyses did not show differences between genders and observed that as age increases, the imagery time decreases with respect to the execution time of the same movement.

**Author Contributions:** Conceptualization, S.N.-N. and S.T.-A.; methodology, S.N.-N., S.T.-A. and T.G.-I.; software, S.T.-A. and S.F.-C.; validation, M.E.S.R., S.T.-A. and D.P.-M.; formal analysis, M.E.S.R., S.T.-A. and J.J.J.R.; investigation, M.E.S.R. and S.T.-A.; resources, M.E.S.R., S.N.-N., D.P.-M. and T.G.-I.; data curation, M.E.S.R., S.T.-A. and J.J.J.R.; writing—original draft preparation, M.E.S.R., S.T.-A. and D.P.-M.; writing—review and editing, S.T.-A., D.P.-M. and T.G.-I.; visualization, M.E.S.R., S.F.-C. and S.N.-N.; supervision, S.N.-N. and T.G.-I.; project administration, D.P.-M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** The study was conducted following the Declaration of Helsinki and was approved by the Ethical Committee for Animal Research and Experimentation of the University of Alcalá with the number CEIM2021/2/032.

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** We would like to thank the Amavir Torrejón de Ardoz nursing home for facilitating fieldwork with the center's users as well as every one of the residents who agreed to participate in this research.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

