**2.1 Prevalence of low physical performance**

In the same definition of sarcopenia suggested by the European working group of Cruz-Jentoft et al. in 2010 (EWGSOP) [8], the prevalence of sarcopenia is already expected to be highly dependent on the method used to measure the diagnostic parameters of this disease and although there are several studies that have used the model proposed by the EWGSOP to determine the prevalence of sarcopenia and at least one from Beaudart et al. from 2015 [39], in which, using two different methods for both muscle mass and strength determination, significant differences were found in the prevalence of sarcopenia, as far as it has been found only the study of Sáez et al. de 2020 [40] compared the prevalence of sarcopenia, using three different methods for assessing physical performance, the usual gain speed (UGS), the time up and go test (TUG), and the short physical performance battery (SPPB), with the cut-off points recommended by the EWGSOP (**Table 1**).

According to this study, the prevalence of a low level of physical performance evaluated by these three different measurement methods, ranged globally, between 20.9 and 45.9%, increasing to 68.8% in the case of women [40]. The highest prevalence of low physical performance was obtained when evaluated by the UGS test, and it was lower for the TUG test (**Figure 2**). The prevalence of low physical performance was always higher in women than in men for any of the methods used for its determination [41]. These results are consistent with the fact that the average results of all physical performance tests were also lower for women [40].

Regarding the association and the concordance between the three tests used to assess physical performance, a significant association was found for all of them, with a low concordance, the overall concordance being between 71.1 and 78.6% [41]. These results show that the three tests used to determine physical performance are not interchangeable with each other and that the choice of one or the other would give significantly different results in the prevalence of physical performance [40].

## **2.2 Prevalence sarcopenia**

According to these results of the study by Sáez et al. [40] that show a discordance in the prevalence of physical performance, and while this parameter is used for the diagnosis of sarcopenia, in the same way, we could expect discordant results on the prevalence of sarcopenia depending on the method used to determine physical performance, even applying the same diagnostic algorithm for all of them and defining sarcopenia as low muscle mass and low muscle function (muscle strength or physical performance) (**Table 2**) [8].

However, the results found showed similar sarcopenia prevalence values regardless of the method used for physical performance (6.0 vs. 63.9 vs. 67.0%) (**Table 3**) and with a concordance almost perfect [40].


#### **Table 1.**

*Physical performance tests and cut points recommended by the EWGSOP.*

#### **Figure 2.**

*Prevalence of physical performance using three different methods: Usual gait speed (UGS); get-up-go test (TUG); short physical performance battery (SPPB) (Sáez et al., 2020).*


#### **Table 2.**

*Criteria for the diagnosis of sarcopenia according to the EWGSOP.*


#### **Table 3.**

*Sarcopenia prevalence comparing three different methods for the determination of physical performance (Sáez et al., 2020).*

#### *Prevalence of Sarcopenia According to the Method Used to Determine Physical Performance DOI: http://dx.doi.org/10.5772/intechopen.100467*

That is, an excellent concordance was found between the prevalence of sarcopenia regardless of the method used to assess physical performance, but at the same time with low concordance between the methods used to determine this parameter [40].

This finding allows us to hypothesize that possibly the diagnostic model used could not be dependent on the method used to determine physical performance and that therefore, the choice of one or another measurement technique for this parameter would not affect or influence the prevalence and the final diagnosis of sarcopenia [41].

These prevalence results are what would be expected and would be consistent with the definition of Cruz-Jentoft et al. of 2010 [8], suggesting that it is possible to choose any of the three methods of physical performance proposed by this group, which should be equally valid, and therefore give similar results for the prevalence of sarcopenia.

However, at this point, the following reflection could be made: *How is it possible that there is a significant difference in the prevalence of physical performance depending on the method chosen and a low concordance between the three methods used for its determination, and that the prevalence of sarcopenia has a near-perfect match? Could it be that physical performance was not a determining parameter for the diagnosis of sarcopenia?*

To answer these questions, it was proposed to apply a new model (**Table 4**), defining sarcopenia as low muscle strength plus low muscle mass and without taking physical performance into account, and comparing and assessing the concordance of the prevalence between this new algorithm and the one proposed by the EWGSOP in 2010 [40] for three different methods of assessing physical performance.

The prevalence of sarcopenia found according to this new algorithm was 63.9%, the association with the previous results, where physical performance was taken into account, was significant, and the agreement between them was excellent (**Figure 3**) [41].

These findings would indicate that indeed, being the agreement between the four cases almost perfect, physical performance does not seem to be determining or necessary for the diagnosis of sarcopenia [41].

The justification for these results is that for at least 95.4% of the cases in which the diagnosis is sarcopenia, muscle mass and strength have a low value, and according to the definition used for the diagnosis of sarcopenia (**Table 2**), this condition would be sufficient to confirm a positive case. In this way, the value, whether normal or low, of physical performance would no longer change the result of the diagnosis, and therefore for this 95.4% of cases, the method used to determine this parameter would no longer be relevant.

That is, most of the patients with low values of physical performance for any of the three tests (more than 82.4%) also had low values of muscle mass and strength [41], and thus when determining sarcopenia, the assessment of physical performance was indifferent.

Therefore, if the objectives were to find sarcopenia cases in a chosen population, a new diagnostic model, where sarcopenia was defined only by a low value of muscle strength plus a low value of muscle mass without having to assess physical performance [40], would be sufficient, to obtain the same results as with the model proposed by Cruz-Jentoft et al. in 2010 [8] where physical performance was taken into account.

The results found are also consistent and could in this way reinforce the proposal made by other authors such as Studenski et al. in 2014 [14] or Cruz-Jentoft et al. in 2019 [16] who proposed new diagnostic models, where sarcopenia was defined and


**Table 4.**

*New criteria proposal for the diagnosis of sarcopenia (Sáez et al., 2020).*

#### **Figure 3.**

*Prevalence of sarcopenia using three different methods: Usual gait speed (UGS); get-up-go test (TUG); short physical performance battery (SPPB) and without physical performance (Sáez et al., 2020).*

determined only taking into account these two properties of the muscle (strength and mass), without taking into account physical performance.

#### *2.2.1 Older than 80 years*

When the prevalence of sarcopenia was analyzed according to these four options, three taking into account physical performance and another without taking it into account, but for patients over 80 years of age, the results were even more conclusive, since the prevalence was the same in all cases (73.2%) and the agreement between them was perfect [41].

These results could mean two important things, first that sarcopenia is highly prevalent among the population over 65 years of age [42], but it could also mean that by increasing the age range from which sarcopenia is assessed, and the differences in the prevalence of this disease are reduced until identical results are found regardless of the method which is chosen to assess physical performance. This statement is consistent with that of other authors such as Petermann-Rocha et al. [43] who in a 2019 study in which they compared the prevalence between two diagnostic models, stated that the differences between the different results found in prevalence also decreased with increasing the age range considered. In other words, the greater the age range of the population studied, the less relevant it is to measure physical performance for the detection of cases of sarcopenia.

It has been found that concordance between these two diagnostic models remains perfect for patients 77 years of age or older and excellent for patients 75 years of age or older [41].

*Prevalence of Sarcopenia According to the Method Used to Determine Physical Performance DOI: http://dx.doi.org/10.5772/intechopen.100467*

#### *2.2.2 Sarcopenia staging*

If the staging of sarcopenia in its different categories is taken into account (presarcopenia, sarcopenia, or severe sarcopenia), according to the model proposed by the EWGSOP in 2010, the results show that the prevalence of the state of presarcopenia and sarcopenia was higher for the physical performance measured with the TUG test, but for the severe sarcopenia state, the prevalence is higher with the UGS test [41].

Regarding the prevalence of absence of sarcopenia, it is observed that it is the same regardless of the method used for physical performance [41]. This is consistent since according to the EWGSOP definition, the absence of sarcopenia is determined only by a normal value of muscle mass, regardless of the value of the other two diagnostic parameters.

Regarding the association and concordance between the prevalence of sarcopenia states according to the method used for physical performance, a significant association was found and a global concordance percentage was greater than 76.0% in all cases, being the best 86.6% between the TUG and SPPB tests [41].

As mentioned above, a low concordance was found between the methods used to assess physical performance, and although on the other hand, it seems that the prevalence of sarcopenia would be independent of the method used to assess physical performance when assessing sarcopenia according to its states, it is observed that, although for the case of absence of sarcopenia, there are no variations in prevalence (17.5% for the three methods), for the state of presarcopenia, the greatest variation was 3.1% between the TUG test and the SPPB test, but these differences increased up to 16.5% points for the case of the severe sarcopenia state, between the UGS test and the TUG test [41]. The TUG test is the one that shows the greatest difference with respect to the other two in both sarcopenia and severe sarcopenia states.

These differences are due, on the one hand, to the fact that, as already mentioned, the three physical performance tests are not concordant with each other, and although it was found that this aspect did not influence the prevalence of sarcopenia, however, the severity of sarcopenia is influenced by physical performance, since according to the EWGSOP definition, the three diagnostic parameters must be low (**Table 2**).

When the prevalence of a low value of physical performance was assessed, precisely the TUG test was the one with the lowest prevalence (20.9%) with a difference of 25.0% points compared to the UGS test and 16.6% points regarding the SPPB, which is why the lowest value of severe sarcopenia was also obtained with this test [41].

On the other hand, it was the UGS test that had the highest prevalence of a low value for physical performance, which is why it was also the test that obtained the highest prevalence of severe sarcopenia. In fact, the higher the prevalence of the low value of physical performance, the higher the prevalence of severe sarcopenia [41].

This result was consistent with the definition of severe sarcopenia, for which this state only occurred with the low values of the three diagnostic parameters of this disease (**Table 2**), and therefore, physical performance is a necessary parameter if we want to determine the severity of sarcopenia.

### **3. Conclusions**

The prevalence of sarcopenia obtained by applying the diagnostic algorithm proposed by the EWGSOP in 2010 [8] was very similar regardless of the method, which was used to determine physical performance. However, we also found that the prevalence of poor physical performance was dependent on the method used to measure it. The apparent incongruity between these two conclusions could be explained by a third; that is, physical performance might not be a necessary parameter for the diagnosis of sarcopenia and therefore, it might be sufficient to use a simplified diagnostic algorithm that takes into account only strength and muscle mass but not the physical performance and obtain the same diagnostic results for sarcopenia. Finally, we conclude that the results found are consistent and reinforce the proposal made by the EWGSOP in 2018 [16] where physical performance is no longer a necessary parameter for determining sarcopenia, although it could be to determine the severity of this disease.
