Review of Respiratory Medicine - Volumen 25, N�mero 1 - March 2025

Original Articles

Reference Values for the One-Minute Sit-to-Stand Test in the Argentine Adult Population

Valores de referencia de la prueba de sentarse y pararse de 1 minuto para la población adulta argentina

ABSTRACT

Background: The one-minute sit-to-stand test (1min-STST) is a field test used to assess physical capacity. It is easy to use and has great clinical utility; however, no reference values are currently available for the Argentine population. The objective of this study was to establish reference values for the 1min-STST in a healthy Argentine population.

Methods: A multicenter cross-sectional study was conducted, collecting data from seven locations across Argentina. Healthy adults aged 18 to 80 were recruited. Anthropomet­ric variables, smoking status, Borg scale ratings, and number of repetitions during the 1min-STST were recorded, among other variables. Reference values were determined by sex and age range.

Results: The study included 314 healthy subjects (50.6% women, n=159; median height of 168.7 cm [9.1], weight of 75.4 kg [14.7], and an average BMI [Body Mass Index] of 22.3 ± 3.7 kg/m²). The median (and the lower limit of normality, LLN) for the 1min-STST in men ranged from 44 repetitions (LLN 22) for those aged 20-29 to 22 repetitions (LLN 19) for those aged 70-80. For women aged 20-29, the median was 46 repetitions (LLN 17), while for those aged 70-80, it was 30 (LLN 17).

Conclusions: This study established reference values for the healthy adult population of Argentina, providing a useful tool for assessing functional capacity using the 1min-STST.

Key words: Functional capacity, Field tests, Reference values, Sit-to-Stand Test, Physical performance

RESUMEN

Introducción: La prueba de sentarse y pararse en un minuto (1min-STST) es una prueba de campo utilizada para evaluar la capacidad física. Es de fácil implementación y tiene una gran utilidad clínica; sin embargo, no existen valores de referencia disponi­bles actualmente para la población argentina. El objetivo de este estudio fue establecer valores de referencia para el 1min-STST en una población argentina sana.

Métodos: Se llevó a cabo un estudio transversal multicéntrico, con recolección de datos en siete localidades de Argentina. Se reclutaron adultos sanos entre 18 y 80 años. Se registraron variables antropométricas, estado de tabaquismo, calificaciones en la escala de Borg y el número de repeticiones durante el 1min-STST, entre otras. Los valores de referencia se determinaron según sexo y rango etario.

Resultados: Se incluyeron en el estudio 314 sujetos sanos (50,6 % mujeres, n = 159; mediana de altura de 168,7 cm (9,1), peso de 75,4 kg (14,7) y un IMC promedio de 22,3 ± 3,7 kg/m². La mediana (y el límite inferior de normalidad [LIN]) para el 1min-STST en hombres varió de 44 (LIN 22) repeticiones para aquellos entre 20 y 29 años a 22 (LIN 19) repeticiones para aquellos entre 70 y 80 años. Para mujeres de 20-29 años, la mediana fue de 46 (LIN 17) repeticiones, mientras que para aquellas de 70-80, la mediana fue de 30 (LIN 17) repeticiones.

Conclusiones: Este estudio estableció valores de referencia para la población adulta sana de Argentina y proporcionó una herramienta útil para evaluar la capacidad fun­cional mediante el 1min-STST.

Palabras clave: Capacidad funcional, Pruebas de campo, Valores de referencia, Prueba de sentarse y pararse, Rendimiento físico

Received: 12/10/2024

Accepted: 02/14/2025

INTRODUCTION

Functional capacity is defined as the ability to perform daily tasks at home, school, or work with enough energy to enjoy recreational activities and to deal with periods of additional effort or illness.¹ It involves different aspects such as strength, en­durance, flexibility, and speed, all of which have a direct impact on physical performance and overall health.² This capacity is essential not only for ev­eryday activities but also to participate in sports and recreational activities.²

The assessment of functional capacity is a fun­damental process for defining the fitness level of a person.³ This assessment can be carried out in laboratories or though field tests.⁴ Each method has advantages and disadvantages: the laboratory provides more accurate and controlled measure­ments, for example gas and lactate analysis, whereas the field tests are more practical and accessible for clinical professionals, since they evaluate performance in situations that are more representative of daily life.⁵ Field tests become particularly important when there are limited resources for laboratory evaluations, because they allow a reasonable estimation of the functional capacity without requiring expensive or specialized equipment.⁶ Also, these tests are especially useful in areas where access to lab facilities is limited, providing a comprehensive view of the physical condition of the population.⁷

The 6-Minute Walk Test (6MWT) has been widely used as a standard for evaluating func­tional capacity in various population groups given its simplicity and efficacy.⁶ But, in contexts where it is not possible to perform the 6MWT, probably due to the lack of an adequate space, the One- Minute Sit-to-Stand Test (1min-STST) comes up as a viable alternative.⁹ The 1min-STST has proven to be specially valuable for evaluating and monitoring patients with respiratory or cardio­vascular diseases, providing relevant information about the functional capacity of those patients, as well as the efficacy of the therapies used.¹¹ Also, recent studies indicate that the 1min-STST can be a valid and reliable tool for measuring functional capacity in patients with chronic respiratory diseases.^12,13

The existing literature has shown the psycho­metric properties of the 1min-STST for quantify­ing functional capacity, supporting its validity and reliability.^14,15 Ensuring the validity and consisten­cy of these tests is crucial for accurately measuring the functional capacity of an individual.¹⁶

Thanks to its features, the 1min-STST has found a relevant place in the rehabilitation field, as an accessible, effective tool for monitoring patients in primary care level and telerehabilitation.17,18 This modality allows for a more convenient and accessible administration, simplifying the remote evaluation and tracking of the patients’ progress over time.¹⁹ This is beneficial for both healthcare professionals and patients, since it improves the quality of rehabilitation and care.²⁰

In order to analyze the results of the 1min- STST, it is very important to have reference values that help determine if an individual’s performance falls within the normal range according to their age group and specific conditions.²¹ Currently, the mostly used reference values come from a Swiss population.²² These values provide normative data that can be used to interpret results in different populations and different clinical contexts. Still, they were established in a population that has dif­ferent characteristics in terms of lifestyle, with less sedentary behavior, and lower prevalence of obe­sity compared to the Latin American population. This could be an overestimation of the expected performance for local subjects.²³ Also, recent stud­ies have found significant differences in terms of cardiorespiratory responses between the 6MWT and the 1min-STST in adults with advanced lung diseases, highlighting the need to adapt the refer­ence values to each clinical context.²⁴

Even though existing reference values serve as a starting point, it is crucial to consider variability across different populations and contexts. Fac­tors such as age, sex, physical activity level, and specific health conditions can affect the results.²¹ There are ethnic, anthropometric, sociocultural and dietary reasons that justify the need to set local reference values in order to evaluate func­tional capacity in a more accurate and personal­ized manner. For this reason, the objective of this study was to determine reference values of the 1min-STST for a healthy adult population aged 18 to 80 years in Argentina.

Methodology

A cross-sectional study was conducted in 7 primary care and rehabilitation centers located in differ­ent geographic regions of Argentina (Paraná, Au­tonomous City of Buenos Aires, Tandil, Ushuaia, Catamarca, Mendoza and San Fernando) between December 2022 and September 2023. The cities were intentionally selected to cover different areas of the country and increase geographic represen­tativeness. The study was approved by the IPIER Ethics Committee, CE000344. All participants provided written informed consent. This study was conducted following the guidelines of “Strength­ening the Reporting of Observational Studies in Epidemiology” (STROBE).²⁵ The participants were recruited from the general population, with a uniform strategy across all centers. Information about the study was disseminated through posters in the recruiters’ social media, physical posters placed inside and outside the evaluation centers and e-mails sent to people who voluntarily showed interest in participating and met the inclusion criteria, without meeting any of the exclusion cri­teria. Inclusion criteria: adults aged 18-80 years, self-declared as healthy,²⁶ and able to perform the sit-to-stand maneuver without assistance. Exclu­sion criteria: subjects with a BMI ≥ 35, respiratory diseases (acute or chronic within the past 30 days), limiting musculoskeletal disorders, or cardiac, neurological, or neuromuscular diseases that could interfere with the test. Also subjects who had dif­ficulty understanding or following instructions were excluded (Figure 1).

Measurements

Each participant was evaluated in a single visit following a standardized evaluation order. First, anthropometric and demographic characteristics were recorded. With regard to smoking status, the participants indicated whether they were “never smokers”, “former smokers” or “current smokers”.

The 1min-STST involved one simple movement: standing up from a chair to adopt the bipedal position with the hips and knees fully extended and without using the upper extremities for support.²⁷ The chair was standard, 46 cm high with thoracic lumbar support and no armrests.²⁸ The participants were seated upright with their back against the backrest of the chair, which was placed against the wall. Their knees and hips were flexed and their feet on the floor, shoulder-width apart. Meanwhile, their hands were placed on opposite shoulders with their elbows flexed. The participants were instructed to perform as many repetitions as possible in one minute. The evalu­ators explained and demonstrated the sit-to-stand technique to the participants. Then, the partici­pants practiced the movement under supervision. Corrections were applied when necessary to ensure the technique was properly used before making the final measurement. The number of times the participants were able to sit and stand completely was recorded as the primary variable, and a single measurement of the 1min-STST was taken.²⁹ Additionally, both before and after the test, pulse rate and SpO2 were measured with a Nonin^® 9590 pulse oximeter (Nonin Medical Inc., Plymouth, MN, USA), along with dyspnea and fatigue of the lower extremities, which were assessed using the Modified Borg Scale.³⁰

In order to ensure the standardization of the measurements, training sessions were carried out, where all the evaluators were instructed to record how they were running the test in three opportu­nities, using a volunteer as pilot subject. Those recordings were used to corroborate the proper evaluation technique and adherence to the study protocol. Once the recordings were validated, the evaluators were authorized to begin taking mea­surements at their respective centers.³¹

Statistical analysis

Descriptive analysis

Data were analyzed using the IBM SPSS statistical software, version 25.0 (IBM Corporation, Armonk, NY, USA). The Kolmogorov-Smirnov test was used to verify data distribution. Numerical variables were presented as mean and standard deviation (SD), and qualitative variables were reported as frequency and percentage. Also, a correlation analysis was performed using the Pearson or Spearman tests, according to the distribution of the data, for quantitative variables (age, weight, height, BMI, heart rate, SpO2, dyspnea and lower extremities fatigue) in relation to the results of the 1min-STST. To establish the reference values, previously defined categories were used,³² generat­ing specific normative percentiles specific to sex and age (percentiles: 2.5, 25, 50, 75 and 97.5). The lower limit of normality (LLN) and the upper limit of normality (ULN) were determined with the 2.5th and 97.5th percentiles, respectively.

Predictive analysis

To explore factors associated with performance on the 1min-STST, a multiple linear regression was used with the number of repetitions as the dependent variable. In the preliminary analysis, demographic and clinical variables were taken into account, including age, sex, height, weight and smoking history. However, only the variables that contributed significantly to the model fit were retained in the final model, prioritizing simplicity and clinical applicability. The homoscedasticity of the model was evaluated through the Breusch- Pagan Test. The Enter method was used to gener­ate the most suitable predictive model. The results of the model are presented with the coefficient of determination (R²) and the root mean square error (RMSE). Scatter plots were used to describe the relationship between age, sex, and performance on the 1min-STST.

Sample size calculation

The sample size was estimated using the Cochran formula for large populations: n = (Z² * p * (1-p)) / e², where Z corresponds to the z value for a 90% confidence level (1.645), p corresponds to the expected proportion (0.5), and e to the margin of error (0.05). The calculation assumed a simple sample design without considering a design effect, as the study tried to represent the general popula­tion through open recruitment in different regions of the country. Basing on these parameters, a mini­mum required sample size of 271 participants was determined. No additional adjustment was made for non-response rate in the calculation.

RESULTS

Of the 353 recruited individuals, 39 were excluded: 25 due to a history of heart disease and 14 due to joint disorders that prevented them from perform­ing the test. The data from 314 patients were ana­lyzed: 159 women (50.6%) and 155 men (49.4%). 15.9% of the participants reported being smokers. Table 1 below shows the demographic and clinical characteristics of the population.

Reference values for the 1min-STST were de­termined for the Argentine population, broken down by sex and age range (Table 2). The median number of repetitions varied among women from 46 repetitions in the 20-29 age group to 30 repeti­tions in the oldest age group (70-80 years). This shows a progressive decline with age. Men showed a median of 44 repetitions in the 20-29 age group, and 22 repetitions in the same oldest age group, also showing a decline with age (Figure 2).

A difference in the number of repetitions is observed basing on sex: men in the younger age groups tend to have higher values compared to women of the same age group. However, these dif­ferences tend to decrease in the groups of older age, where men and women values are more similar. Figures 3 and 4 illustrate the relationship between age and repetitions in men and women, showing the regression lines, the 95% confidence bands, and the p-value. The Breusch-Pagan Test showed sig­nificant evidence of heteroscedasticity (p < 0.001), indicating that the variance of the residuals was not constant across the prediction range.

The analysis of the correlations between the values of the 1min-STST and age revealed a moder­ate inverse relationship (Spearman’s rho = -0.485; p < 0.001). A very low inverse correlation was observed with weight (Spearman’s rho = -0.081; p = 0.152), and there was a weak inverse corre­lation with the BMI (Spearman’s rho = -0.130; p = 0.022). There was no significant correlation with height (Spearman’s rho = 0.093; p = 0.100).

Reference equation

Age, height, and sex variables were found to be significant predictors in the linear regression analysis, where age and height showed a negative association (that is to say, the greater the age and height, the fewer the number of repetitions), and being a male was associated with an increase in performance. Based on the given coefficients, the predictive equation for the number of repetitions in the 1min-STST is:

1min-STST (rep) = 80.324 – 0.372 ×

Age – 0.168 × Height + 4.075 × Sex

Where age is expressed in years, height in centimeters and sex is coded as 0 for women and 1 for men. The model presents an R² of 0.26 (p< 0.001) and a RMSE of 10.1. The development of the equation was based on an exploratory analysis that included demographic and clinical variables potentially associated with 1min-STST performance such as age, sex, height, weight and smoking history. Variables such as weight, height, BMI, and smoking history didn’t show statistically significant associations in the final model. For this reason, only the variables that showed a statisti­cally significant association were included.

DISCUSSION

This study established reference values for the 1-min STST in healthy adults aged 18 to 80 years in Argentina, providing a tool to interpret clinical results in contexts lacking local normative data. By offering these reference values, our research aims to provide valuable information and guidance for assessing performance on the 1min-STST in populations with comparable demographic charac­teristics, thereby helping healthcare professionals and researchers evaluate functional capacity in a more contextualized manner.

The importance of adapting reference values to the local population should not be underesti­mated,²¹ as the use of international standards may not accurately reflect the characteristics of our population. In this regard, one of the strengths of our study was the standardization of the protocol across all participating centers, guaranteeing that the data obtained are consistent, comparable, and representative of the geographic and demographic diversity of Argentina.

Our results showed that 1min-STST perfor­mance decreases with age, with a moderate inverse correlation (Spearman’s rho = -0.485; p < 0.001). This reflects the general trend of declining functional capacity with aging in both sexes. This is consistent with previous studies that identify age as a key factor associated with per­formance on this test.²² However, when analyzing this association separately by sex, we observed that the explanatory power of age was higher in men (R² = 0.29) compared to women (R² = 0.19), though it remained limited in both cases. Also, no significant correlations were observed with height (rho = 0.093; p = 0.100), whereas weight and BMI showed very low or weak correlations, respectively. Nevertheless, height was found to be a significant variable in the multivariable model. This can be explained by the fact that regression adjusts the effect of each variable and at the same time takes into account the others, revealing its independent contribution to performance on the 1min-STST, which is not evident in the bivariate analysis. This phenomenon has been described before, where bivariate analyses may hide latent relationships that are only apparent in more complete multivari­able models.³³ These findings reinforce the fact that, while age is the main determinant observed in our population, other anthropometric factors seem to have less influence on the performance of the 1min-STST. The multivariable equation, which included age, sex, and height as predictors, showed limited explanatory power (R² = 0.26), indicating that other factors not accounted for could affect the performance of the 1min-STST. It should be noted that the model was not subjected to additional tests for internal validation, residual normality, or multicollinearity, and that it showed heteroscedasticity, which limits the precision of its estimates. For these reasons, it should be in­terpreted as an exploratory and guiding tool, and not as a definitive predictive model for clinical use. Despite these limitations, the performance of the model is consistent with the information reported in the literature.³⁴ An equation was proposed based on age, sex and BMI with an R² of 26%, while in Chile,³⁵ age and height were included and reported an R² of 26% in women and 32% in men. Even though the included variables differ partially be­tween studies, their explanatory power is similar, and this reinforces the methodological validity of our proposal. These similarities suggest that the limited predictive capacity observed is a common characteristic in this type of model, probably due to the influence of multiple factors not considered in population-based studies.

An important aspect of these reference values is the inclusion of subjects with a BMI of up to 35 kg/m². The reasoning behind this decision lies in the fact that the Latin American population has significant overweight and obesity rates, often exceeding 25% of the whole population.²³ There­fore, from a clinical perspective, it is anticipated that two to three out of ten end users of these tests will have obesity. It is worth noting that our approach aligns with previous studies, such as that of Furlanetto et al, who also used a BMI value that was above what is considered normal weight.³⁶

Another key aspect for having specific reference values is that using standardized values from other populations could lead to misinterpretations and incorrect diagnoses, as individual variations could not be adequately accounted for.³⁷ For this reason, the ATS/ERS (American Thoracic Society/European Respiratory Society) Statement recommends using reference values of the same population in which the procedures will be applied.³⁸ This is especially relevant if we consider that, in certain populations (for example, patients with pulmonary arterial hypertension), performance on the 1min-STST has shown a strong correlation with quality of life and functional limitation. So, using reference values that don’t reflect the reality of these specific conditions could result in an underestimation or overestimation of the functional health status.¹³

An important thing to consider is how repre­sentative the sample is in the context of the Ar­gentine population. The study by Strassmann et al included around 7.000 subjects.²² Reaching such a number is a big challenge, especially in the group of subjects aged 60 years and over. Comparatively speaking, in previous Latin American studies, Fur­lanetto et al evaluated approximately 300 individu­als in Brazil, a country with a population of 215 million. Our reference values were obtained from just over 300 subjects in a population of 45 million. Even though the sample size was calculated with 90% confidence level, getting a larger sample in the group of subjects aged 60 years and over is still a challenge due to the prevalent health conditions and sedentary lifestyle within this group.

Various studies conducted in recent years in our population, especially in post-COVID-19 patients, have used the Strassman values.^20,39 Since the Swiss values are 30% higher than ours, there has been an underestimation of functional capacity. This reinforces the importance of having our own values for a proper characterization of the local population.

Our median values (p50) show similarities and differences compared to those reported in Brazilian studies regarding the 1min-STST.³⁶ It is worth noting that said studies express results as means, whereas our results are presented as medians, and this could affect direct comparisons. 30 repetitions were observed in women aged 60 to 69 years, slightly above the Brazilian average of 29 repetitions (3.4% higher). Conversely, men aged 70 to 80 years showed a lower performance, with 22 repetitions compared to the 27 repetitions reported in Brazil (18.5% lower). However, in most age groups, results were consistently higher. For example, in women aged 20 to 29 years, 46 repetitions were achieved (21% higher than the 38 reported in Brazil), and in men aged 40 to 49 years, 39 repetitions were recorded compared to 31, representing a 26% difference.

These differences can be explained by several factors, such as demographic and anthropometric characteristics. Sociocultural factors, for example higher levels of physical activity or lifestyle differ­ences, could also play an important role.

When compared to the values presented by Strassmann et al,²² significant differences were observed in several age groups. In women aged 60 to 69 years, our results (30 repetitions) were slightly lower than the 33 reported in that study. Similarly, in men aged 40 to 49 years, Strassman reported 45 repetitions, six more than the 39 rep­etitions observed in our sample. This pattern of higher performance according to Strassman was repeated in other groups, like women aged 40 to 49 years (42 versus 35 repetitions, respectively). An exception was observed in women aged 70 to 80 years, where our values exceeded those of Stras­smann (30 versus 28 repetitions). In contrast, our results in men of the same age range were lower again (22 versus 24 repetitions).

In summary, the values previously reported by Strassmann consistently showed higher perfor­mance in older men and women, while the values reported by Furlanetto tend to be more similar to ours.^22,36 Our values differ from those shown in the literature, especially with regard to male values, which are lower than those reported by Strassmann. The most probable explanation is a selection bias due to the relatively small sample size in some subgroups.

One limitation of our study is the reduced number of subjects over 60 years. This may be due to the fact that older adults tend to have sed­entary lifestyles and a higher prevalence of non-communicable diseases, making it more difficult to obtain a population considered “healthy”. The classification of apparently healthy individuals was determined on self-reporting and the absence of diagnosed medical conditions. However, it is worth noting that including individuals with un­diagnosed conditions is a prevalent characteristic in studies involving large population samples in­tended to establish reference parameters. Another limitation of this study is that the sampling didn’t have a probabilistic approach. This could have introduced a bias in the selection of participants, since those who accepted the invitation could dif­fer in characteristics from those who didn’t. One aspect that wasn’t recorded was the socioeconomic situation, which could have affected the results. Another methodological limitation is the fact that the health criteria were self-reported-an approach commonly used in population-based studies,²⁶ though we acknowledge that this strategy may not fully exclude undiagnosed conditions.

Finally, another limitation is that we conducted only one repetition of the 1min-STST. The lit­erature doesn’t clarify whether this test has a learning effect or not. However, it seems that in healthy individuals or those without substantially reduced functional capacity, there could be a learn­ing effect that Furlanetto et al estimated to be around one repetition.³⁶ Another recent article suggests that three repetitions of the 1min-STST are necessary for observing the true performance of a young individual, but, in older adults, a single attempt may be enough.⁴⁰ There is certainly no consensus on the number of tests required, and it seems that healthy individuals show a greater learning effect than those with health conditions. Therefore, future studies should explore if certain strategies such as practice of test execution reduce this learning effect.

CONCLUSION

Reference values for the 1min-STST were deter­mined for the healthy Argentine population aged 18 to 80 years. These values provided a simple and cost-effective means of measuring functional capacity. They can be really useful for evaluating and determining the effects of interventions that involve assessing the functional capacity with this test.

Conflict of interest

The authors have no conflict of interest to declare with regard to this research.

Funding

No funding was received for this research.

REFERENCES

1. Barnekow-Bergkvist M, Hedberg G, Janlert U, Jansson E. Development of muscular endurance and strength from ad­olescence to adulthood and level of physical capacity in men and women at the age of 34 years. Scand J Med Sci Sports. 1996;6:145-55. https://doi.org/10.1111/j.1600-0838.1996.tb00082.x

2. Vanhees L, Lefevre J, Philippaerts R, et al. How to assess physical activity? How to assess physical fitness? Eur J Cardiovasc Prev Rehabil. 2005;12:102-14. https://doi.org/10.1097/00149831-200504000-00004

3. American College of Sports Medicine, Liguori G, Feito Y, Fountaine CJ, Roy B, editores. ACSM’s guidelines for exercise testing and prescription. Eleventh edition. Phila­delphia Baltimore New York London Buenos Aires Hong Kong Sydney Tokyo: Wolters Kluwer; 2022. 513 p.

4. Torres-Castro R, Núñez-Cortés R, Larrateguy S, Alsina- Restoy X, Barberà JA, Gimeno-Santos E, et al. Assessment of Exercise Capacity in Post-COVID-19 Patients: How Is the Appropriate Test Chosen Life. 2023;13:621. https://doi.org/10.3390/life13030621

5. Tran D. Cardiopulmonary Exercise Testing. En: Guest PC, editor. Investigations of Early Nutrition Effects on Long-Term Health [Internet]. New York, NY: Springer New York; 2018 [citado 19 de noviembre de 2024]. p. 285- 95. (Methods in Molecular Biology; vol. 1735). https://doi.org/10.1007/978-1-4939-7614-0_18

6. Holland AE, Spruit MA, Troosters T, et al. An official European Respiratory Society/American Thoracic Society technical standard: field walking tests in chronic respira­tory disease. Eur Respir J. 2014;44:1428-46. https://doi.org/10.1183/09031936.00150314

7. Fell BL, Hanekom S, Heine M. Six-minute walk test protocol variations in low-resource settings – A scoping review. South Afr J Physiother 2021;77:1549. https://doi.org/10.4102/sajp.v77i1.1549

8. Kronberger C, Mousavi RA, Öztürk B, Willixhofer R, Dachs TM, Rettl R, et al. Functional capacity testing in patients with pulmonary hypertension (PH) using the one-minute sit-to-stand test (1-min STST). PLOS ONE. 2023;18:e0282697. https://doi.org/10.1371/journal.pone.0282697

9. Peroy-Badal R, Sevillano-Castaño A, Torres-Castro R, et al. Comparison of different field tests to assess the physical capacity of post-COVID-19 patients. Pulmonol­ogy. enero de 2024;30:17-23. https://doi.org/10.1016/j.pulmoe.2022.07.011

10. Spence JG, Brincks J, Løkke A, Neustrup L, Østergaard EB. One-minute sit-to-stand test as a quick functional test for people with COPD in general practice. Npj Prim Care Respir Med. 2023;33:11. https://doi.org/10.1038/s41533-023-00335-w

11. Kronberger C, Mousavi RA, Öztürk B, et al. Exercise capac­ity assessed with the one-minute sit-to-stand test (1-min STST) and echocardiographic findings in patients with heart failure with preserved ejection fraction (HFpEF). Heart Lung. 2022;55:134-9. https://doi.org/10.1016/j.hrtlng.2022.05.001

12. Crook S, Büsching G, Schultz K, Lehbert N, Jelusic D, Keusch S, et al. A multicentre validation of the 1-min sit-to-stand test in patients with COPD. Eur Respir J. 2017;49:1601871. https://doi.org/10.1183/13993003.01871-2016

13. Kronberger C, Willixhofer R, Mousavi RA, Grzeda MT, Litschauer B, Krall C, et al. The one-minute sit-to-stand-test performance is associated with health-related quality of life in patients with pulmonary hypertension. PLOS ONE. 2024;19:e0301483. https://doi.org/10.1371/journal.pone.0301483

14. Tanriverdi A, Kahraman BO, Ozpelit E, Savci S. Test–Re­test Reliability and Validity of 1-Minute Sit-to-Stand Test in Patients With Chronic Heart Failure. Heart Lung Circ. 2023;32:518-24. https://doi.org/10.1016/j.hlc.2023.01.008

15. Bohannon RW, Crouch R. 1-Minute Sit-to-Stand Test: SYSTEMATIC REVIEW OF PROCEDURES, PERFOR­MANCE, AND CLINIMETRIC PROPERTIES. J Cardio­pulm Rehabil Prev. 2019;39:2-8. https://doi.org/10.1097/HCR.000000000000033635

16. Souza ACD, Alexandre NMC, Guirardello EDB, Souza ACD, Alexandre NMC, Guirardello EDB. Propriedades psicométricas na avaliação de instrumentos: avaliação da confiabilidade e da validade. Epidemiol E Serviços Saúde. 2017;26:649-59. https://doi.org/10.5123/S1679-49742017000300022

17. Sisó-Almirall A, Brito-Zerón P, Conangla Ferrín L, et al. Long Covid-19: Proposed Primary Care Clinical Guidelines for Diagnosis and Disease Management. Int J Environ Res Public Health. 2021;18:4350. https://doi.org/10.3390/ijerph18084350

18. Dalbosco-Salas M, Torres-Castro R, Rojas Leyton A, et al. Effectiveness of a Primary Care Telerehabilita­tion Program for Post-COVID-19 Patients: A Feasibility Study. J Clin Med. 2021;10:4428. https://doi.org/10.3390/jcm10194428

19. Holland AE, Malaguti C, Hoffman M, et al. Home-based or remote exercise testing in chronic respiratory disease, during the COVID-19 pandemic and beyond: A rapid review. Chron Respir Dis. 2020;17:1479973120952418. https://doi.org/10.1177/1479973120952418

20. Dias JF, Oliveira VC, Borges PRT, et al. Effectiveness of exercises by telerehabilitation on pain, physical function and quality of life in people with physical disabilities: a systematic review of randomised controlled trials with GRADE recommendations. Br J Sports Med. 2021;55:155- 62. https://doi.org/10.1136/bjsports-2019-101375

21. Gräsbeck R. Reference values, why and how. Scand J Clin Lab Investig Suppl. 1990;201:45-53. https://doi.org/10.1080/00365519009085800

22. Strassmann A, Steurer-Stey C, Lana KD, et al. Population-based reference values for the 1-min sit-to-stand test. Int J Public Health. 2013;58:949-53. https://doi.org/10.1007/s00038-013-0504-z

23. Chávez-Velásquez M, Pedraza E, Montiel M. Prevalencia de obesidad: estudio sistemático de la evolución en 7 países de América Latina. Rev Chil Salud Pública. 2019;23:72. https://doi.org/10.5354/0719-5281.2019.55063

24. Watson K, Winship P, Cavalheri V, et al. In adults with advanced lung disease, the 1-minute sit-to-stand test underestimates exertional desaturation compared with the 6-minute walk test: an observational study. J Physiother. 2023;69:108-13. https://doi.org/10.1016/j.jphys.2023.02.001

25. Von Elm E, Altman DG, Egger M, Pocock SJ, Gøtzsche PC, Vandenbroucke JP. The Strengthening the Report­ing of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. J Clin Epidemiol. 2008;61:344-9. https://doi.org/10.1016/j.jclinepi.2007.11.008

26. Royal College of Physicians. Research on healthy volun­teers: a report of the Royal College of Physicians. J R Coll Physicians Lond. 1986;20:3-17. https://doi.org/10.1016/S0035-8819(25)02427-4

27. Ozalevli S, Ozden A, Itil O, Akkoclu A. Comparison of the Sit-to-Stand Test with 6min walk test in patients with chronic obstructive pulmonary disease. Respir Med. 2007;101:286- 93. https://doi.org/10.1016/j.rmed.2006.05.007

28. Bohannon RW. Reference Values for the Five-Repetition Sit-to-Stand Test: A Descriptive Meta-Analysis of Data from Elders. Percept Mot Skills. 2006;103:215-22. https://doi.org/10.2466/pms.103.1.215-222

29. Sevillano-Castaño A, Peroy-Badal R, Torres-Castro R, et al. Is there a learning effect on 1-min sit-to-stand test in post- COVID-19 patients? ERJ Open Res. 2022;8:00189-2022. https://doi.org/10.1183/23120541.00189-2022

30. Johnson MJ, Close L, Gillon SC, Molassiotis A, Lee PH, Farquhar MC. Use of the modified Borg scale and numerical rating scale to measure chronic breathlessness: a pooled data analysis. Eur Respir J. 2016;47:1861-4. https://doi.org/10.1183/13993003.02089-2015

31. Cruz-Montecinos C, Torres-Castro R, Otto-Yáñez M, Barros-Poblete M, Valencia C, Campos A, et al. Which sit-to-stand test best differentiates functional capacity in older people? Am J Phys Med Rehabil. 2024; https://doi.org/10.1097/PHM.0000000000002504

32. Cole TJ. The LMS method for constructing normalized growth standards. Eur J Clin Nutr. 1990;44:45-60.

33. Stagner WC, Jain A, Al-Achi A, Haware RV. Employing Multivariate Statistics and Latent Variable Models to Identify and Quantify Complex Relationships in Typical Compression Studies. AAPS PharmSciTech. 2020;21:186. https://doi.org/10.1208/s12249-020-01712-1

34. Vilarinho R, Montes AM, Noites A, Silva F, Melo C. Ref­erence values for the 1-minute sit-to-stand and 5 times sit-to-stand tests to assess functional capacity: a cross-sectional study. Physiotherapy. 2024;124:85-92. https://doi.org/10.1016/j.physio.2024.01.004

35. Otto-Yáñez M, Torres-Castro R, Barros-Poblete M, et al. One-minute sit-to-stand test: Reference values for the Chil­ean population. PLOS ONE. 2025;20:e0317594. https://doi.org/10.1371/journal.pone.0317594

36. Furlanetto KC, Correia NS, Mesquita R, et al. Reference Values for 7 Different Protocols of Simple Functional Tests: A Mul­ticenter Study. Arch Phys Med Rehabil. 2022;103:20-28.e5. https://doi.org/10.1016/j.apmr.2021.08.009

37. Lippi G, Blanckaert N, Bonini P, et al. Causes, conse­quences, detection, and prevention of identification errors in laboratory diagnostics. Clin Chem Lab Med. https://doi.org/10.1515/CCLM.2009.045

38. Miller MR, Crapo R, Hankinson J, et al. General consider­ations for lung function testing. Eur Respir J. 2005;26:153- 61. https://doi.org/10.1183/09031936.05.00034505

39. Núñez-Cortés R, Rivera-Lillo G, Arias-Campoverde M, et al. Use of sit-to-stand test to assess the physical capacity and exertional desaturation in patients post COVID-19. Chron Respir Dis. 2021;18:1479973121999205. https://doi.org/10.1177/1479973121999205

40. Vilarinho R, Montes AM, Melo C. Age-related influence on reliability and learning effect in the assessment of lower limb strength using sit-to-stand tests: A cross-sectional study. Health Sci Rep. 2024;7:e2064. https://doi.org/10.1002/hsr2.2064