Hrev_master [page 90] [Healthcare in Low-resource Settings 2023; 11:11332] Six-minute step test perform- ance in asymptomatic adults Riya Kalra,1 Kanu Goyal,1 Manu Goyal,1 Hina Vaish2 1Maharishi Markandeshwar Institute of Physiotherapy and Rehabilitation, Maharishi Markandeshwar (Deemed to be University), Mullana-Ambala, Haryana, India; 2Department of Physiotherapy, School of Health Sciences, CSJM University, Kanpur, Uttar Pradesh, India Abstract The objectives of this study were i) to measure a six-minute step test (6MST) in asymptomatic adults; ii) to determine the applicability of Arcuri et al.’s reference equation to Indian adults; iii) to develop a prediction equation for Indian adults. 110 adult males and females aged 18-40 years were recruited for this prospective cross- sectional study conducted in India. Participants underwent 6MST. Applicability was assessed by comparing the findings of the 6MST with the values derived from Arcuri et al.’s predicted equations using the Bland-Altman plot. A multiple regression analysis was used to develop the prediction equation. The mean±SD six-minute step count was 159.42±17.60 steps and 150.78±14.39 steps in males and females respectively. The 6MST for males can be determined by males (steps)=204.371- 1.521×age(years) and females (steps)=179.567-1.06×age (years). Arcuri et al.’s equation cannot be used to predict 6MST in Indian adults. Region-specific equations are useful to assess the values. Introduction The ability to exercise plays an impor- tant role in determining quality of life and prognosis. Despite the fact that assessing exercise capacity can provide valuable information about a population’s health, it is rarely employed in primary care.1 The step climbing activity necessary in daily life is used to assess exercise ability. Step test has been used to assess functional capability for a long time, particularly in healthy people. Six-minute step test is a quick, easy, inex- pensive method of measuring exercise tol- erance. Also, it requires the least amount of space.1 The six-minute step test (6MST) is extensively used in field testing and is linked to disease prediction, estimated oxy- gen use, and the identification of functional limitations.2 The six-minute step is more commonly used for pulmonary pathologies like chronic obstructive pulmonary disease, interstitial lung disease, etc. if there is a lack of space and the six-minute walking test (6MWT) cannot be conducted. The 6MST is found to be valid and reliable when com- pared with 6MWT.3,4 The 6MST is valid and reproducible, producing greater cardio- vascular stress than the 6MWT in cardiac pathologies.5 The 6MST has also been char- acterized as a submaximal test for the assessment of exercise tolerance in individ- uals with obstructive sleep apnea treated with continuous positive airway pressure.6 One of the earliest equations for the pre- diction of 6MST is that of Arcuri et al.1 Prediction equations that predict the expect- ed value in the absence of pathology allow the magnitude of an individual’s functional limitation to be quantified. Ethnic and geo- graphic variations have been reported as some of the factors responsible for the dis- crepancies in physical test scores.7 The pre- sent study therefore aimed to measure 6MST in Indian adults, to check the appli- cability of Arcuri et al.’s reference equation to this group and, to develop a prediction equation. Materials and Methods The sample size was calculated by using the equation, N>50+8K,8 where K represents the number of independent vari- ables. Seven variables [age, height, weight, body mass index (BMI), waist circumfer- ence, hip circumference, and waist-hip ratio] were used, resulting in at least 106 participants. 110 participants were recruited by purposive sampling for this prospective cross-sectional study. The study was approved by the Institutional Ethical Committee, Project No. IEC-11F. Participants were volunteers recruited over a period of eight months from among the students and staff of the institute, rela- tives of the patients, and nearby community dwellings. Participants were included if they were asymptomatic males and females aged 18-40 years with stable vitals, non- smokers, absence of any disease in the 6 weeks preceding the study, and were able to step up and down without using any exter- nal support. Exclusion criteria included resting heart rate (HR) > 100bpm; systolic blood pressure (BP) >139 mmHg, diastolic BP >89 mmHg; any documented health problem or use of medication such as impaired sensation or cognition, metabolic, cardiac, neurologic, or orthopedic disease; use of walking aids; pregnant females and lactating mothers. All the participants pro- vided written informed consent regarding the study. The body weight (kg) was mea- Healthcare in Low-resource Settings 2023; volume 11:11332 Correspondence: Hina Vaish, Department of Physiotherapy, School of Health Sciences, CSJM University, Kanpur, Uttar Pradesh, India. Tel.: +91.9450124758. E-mail: hina22vaish@gmail.com Key words: aerobic fitness; cardiovascular endurance; exercise; functional capacity; health. Contribution: RK, KG, MG, HV designed the experiments; RK, collected the data; RK, KG; MG wrote the manuscript; KG, MG, data syn- thesis; KG, MG, HV, data analysis, and criti- cal intellectual content. All the authors approved the final version to be published. Conflict of interest: the authors declare no potential conflict of interest, and all authors confirm accuracy. Ethical approval and consent to participate: the study was approved by the Institutional Ethical Committee, Project No. IEC-11F. Informed consent: all patients participating in this study signed a written informed consent form for participating in this study. Patient consent for publication: written informed consent was obtained from a legally authorized representative(s) for anonymized patient information to be published in this article. Availability of data and materials: all data generated or analyzed during this study are included in this published article. Acknowledgment: we greatly acknowledge the support from all participants and sincerely thank all the subjects for taking part in the study. Received for publication: 23 March 2023. Accepted for publication: 23 August 2023. Early access: 11 September 2023. This work is licensed under a Creative Commons Attribution 4.0 License (by-nc 4.0). ©Copyright: the Author(s), 2023 Licensee PAGEPress, Italy Healthcare in Low-resource Settings 2023; 11:11332 doi:10.4081/hls.2023.11332 Publisher's note: all claims expressed in this article are solely those of the authors and do not necessarily represent those of their affili- ated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guar- anteed or endorsed by the publisher. Non -co mmerc ial us e o nly [Healthcare in Low-resource Settings 2023; 11:11332] [page 91] sured with a beam balance scale. Body height (m) was measured using a height scale and BMI [weight/height2 (kg/m2)] was calculated. Using a non-elastic, flexible measuring tape, the circumference of the hips and waist were measured, and the waist-hip ratio was calculated. The 6MST was per- formed according to the guidelines of the American Thoracic Society for conducting the six-minute step test,9 the 6MST was car- ried out on a portable 20-cm-high step with a non-slip rubber surface, physiotherapist counting the steps. Participants were told to sit at rest for five minutes before the test while the physiotherapist explained the exam to them.10 Participants were given six minutes to climb up and down as many times as they could while maintaining their own rhythm. Participants were motivated using phrases like “you’re doing well” and “keep it up”.10,11 When the timer was less than 15 seconds away from finishing the test, the participants were informed. The level of exertion was quantified using the modified Borg scale. For each participant, maximum HR was estimated using HRmax=220-age in years, and submaximal HR was defined as 85 per- cent of maximal HR.The participants might also choose to take a break from the test to rest, but the timer was not halted in either scenario. The test score was recorded at the end and the total number of steps taken in the time limit of 6 minutes.9 Statistical analyses A statistical package for the social sci- ences IBM version 26 statistical software (IBM, Armonk, 97 NY, USA) was used to analyze the data. Correlations were estimat- ed using Pearson’s coefficient of correla- tion. Comparisons between males’ and females’ step count included an indepen- dent t-test. Bland-Altman comparison was performed between the measured and pre- dicted 6MST, based on Arcuri et al.’s refer- ence equation: Male 6MST= 209-[1.05 × age (years)], Female 6MST=174- [1.05 × age] (years)].1 Limits of agreement, calcu- lated as mean difference between measured and predicted 6MST±1.96 standard devia- tion (SD), were used for comparison. Comparisons between measured and pre- dicted 6MST also included paired t-test. Comparison of pre and post-test heart rate and oxyhemoglobin saturation were assessed through paired t-test. Stepwise multiple regression analysis was used to develop the gender-specific reference equa- tion for 6MST. P<0.05 was considered sig- nificant. Results All the enrolled participants (N=110) completed the test, and there were no dropouts. The baseline characteristics of the study population and results of the six- minute step test along with correlations are summarized in Table 1. The mean±SD six- minute step count was 159.42±17.60 steps and 150.78±14.39 steps in males and females respectively. The 6MST reference values determined in the study were found to overestimate the step count in Indian males by 24.84±15.75 steps and underesti- mate in females by 4.73±13.93 steps. There was a significant difference between the 6MST count between males and females (p=0.032). There was a significant differ- ence between pre- and post-6MST heart rate (p<0.0001). Also, there was a significant difference between pre- and post-6MST oxyhemoglobin saturation (p<0.0001). Figures 1 and 2 show the Bland-Altman comparison between the measured and pre- dicted 6MST between males and females. There was a systematic bias between mea- sured and predicted 6MST with Arcuri et al.’s reference equation. The 6MST refer- ence value determined in the study was found to be substantially different from pre- viously reported values.1 Hence new predic- tion equations were developed. Based on the results of the regression analysis, the 6MST for males can be deter- mined by 6MST (steps) males =204.371- 1.521×age (years), R2=0.38 and 6MST (steps) females =179.567-1.065×age (years), R2=0.23. Discussion The present study established normative values for the number of steps climbed dur- ing the 6MST in adult participants from India. Males climbed more steps than women. This study also provided gender- specific reference equation for the 6MST. The 6MST reference value determined in the study was found to be substantially different from previously reported values.1 Short Report Table 1. Baseline characteristics of the participants and results of the six-minute step test. Total (n=110) Males (n=54) Females(n=56) Variables Mean±Standard Deviation Mean±Standard Deviation Mean±Standard Deviation Age (years) 28.26±6.928** 29.56±7.19** 27.02±6.48** Height (cm) 1.65±.057 1.68±.06 1.62±.045 Weight (kg) 63.68±9.56 66.82±8.78 60.64±9.36 Body mass index (kg/m2) 23.35±3.10 23.74±2.68 22.98±3.45 Waist circumference (cm) 90.04±7.70 90.61±6.89 89.50±8.43 Hip circumference (cm) 96.67±7.027 96.17±6.48 97.16±7.54 Waist hip ratio .93±.04 .94±.03 .92±.045 Rate of perceived exertion 4.14±.97 4.33±1.05 3.96±.87 Resting heart rate (Beats per minute) 79.09±7.04 79.87±7.52 78.34±6.53 Post-test heart rate (Beats per minute) 126.25±16.47 123.50±16.15 128.91±16.47 Pre SPO2 (%) 99.00±.62 98.90±.59 99.09±.64 Post-test SPO2 (%) 98.42±.83 98.42±.77* 98.43±.89 HR max 191.74±6.93** 190.44±7.19** 192.98±6.48** Six-minute step count 155.03±16.55 159.42±17.60 150.78±14.39 Predicted six-minute step count‡ - 184.27±8.50 146.07±8.05 6MST, six-minute step test; HR, heart rate; SPO2, Oxy-haemoglobin saturation. *P<0.05; **P<0.001; ‡ Using Arcuri et al.’s equations: Male 6MST= 209-[1.05 × age (years)], Female 6MST=174- [1.05 × age] (years)]. Non -co mmerc ial us e o nly The 6MST reference values determined in the study were found to overestimate the step count in Indian males by 24.84+15.75 steps and underestimate in females by 4.73+13.93 steps. The discrepancies may have been due to geographic and ethnic variability as ethnicity influences physical fitness test performance.12 Anthropometric characteristics of participants may also dif- fer, as Asians have a higher body fat per- centage for the same age, gender, and BMI when compared to the European white pop- ulation.13 Also, the participants included in the present study were non-obese and adults of 18-40 years. We did not want to dilute the sample by merging young adults and older adults due to physiological alterations with advancing age. Age and gender were found to have an association with 6MST.14 There was a sig- nificant negative association of 6MST count with age in the total population, males as well as females in agreement with the previous study.15 Age was the predominant variable in the regression equation as well. The 6MST values decreased in a linear fashion with respect to the increase in age. This may probably be due to the reduced lower limb muscle strength. Although we included normal individuals in our study, this could be attributed to normal age-relat- ed changes in the musculoskeletal systems. Other age-related anthropometric and phys- iological changes, such as increased passive tissue stiffness, aerobic and anaerobic capacity, due to reduced cardiovascular function and alterations in oxidative capac- ity, also, skeletal muscle structure and func- tion may contribute to the decline in test performance.16,17 There was a significant difference in the 6MST values between males and females. The participants, both men and women, in our study were independent. Certain physi- ological variances between the genders, such as body composition, cardiovascular, and lung function, may affect perfor- mance.18 The participants in the present study reached an average of 65.84% of their HR max% predicted. On the contrary, there was no correlation of 6MST with weight, waist and hip circumference, BMI as all our par- ticipants were non obese and healthy.10 Thirty-eight percent and 23% of variance was explained in males and females respec- tively for 6MST, this put forth the need for future large multicenter studies with the inclusion of varied age, weight, and other anthropometric data categories. Limitations This study was limited by several fac- tors. We had a nonrandom sampling method but stringent selection criteria to prevent the risk of bias. Finally, we did not evaluate additional probable variables such as peripheral muscle strength, or body fat composition. Also, the prospective validity of the developed equation was not checked. Conclusions This study brings an important contri- bution as region-specific reference values are needed for use in clinical settings. Arcuri et al.’s equation cannot be used to predict the 6MST in Indian adults. The region-specific values will provide a better interpretability for clinicians to use for assessment and rehabilitation purposes. The new gender-specific regression equations are expected to prove useful for assessment and rehabilitation in Indian adults. References 1. Arcuri JF, Borghi-Silva A, Labadessa IG, et al. Validity and reliability of the 6-minute step test in healthy individu- als: A Cross-sectional study. Clin J Sport Med 2016;26:69-75. 2. Grosbois JM, Riquier C, Chehere B, et al. Six-minute stepper test: A valid clin- ical exercise tolerance test for COPD patients. Int J COPD 2016;11:657-63. 3. Dourado IM, Santos PB, Goulart CL, et al. Is the six-minute step test able to reflect the severity and symptoms based on cat score? Heart Lung 2023;58:28- 33. 4. Patel S, Jones SE, Walsh JA, et al. The Six-minute Step Test as an Exercise Outcome in Chronic Obstructive Pulmonary Disease. Ann Am Thorac Soc 2023;20:476-9. Short Report Figure 1. The Bland-Altman representation of measured and predicted six-minute step test using Arcuri et al.’s equation 6MST (steps) females = Female 6MST=174- [1.05 × age] (years)]. 6MST= six-minute step test. Figure 2. The Bland-Altman representation of measured and predicted six-minute step test using Arcuri et al.’s equation 6MST (steps) males =209-[1.05 × age (years). 6MST= six-minute step test. [page 92] [Healthcare in Low-resource Settings 2023; 11:11332] Non -co mmerc ial us e o nly [Healthcare in Low-resource Settings 2023; 11:11332] [page 93] 5. Marinho RS, Jürgensen SP, Arcuri JF, et al. Reliability and validity of six-minute step test in patients with heart failure. 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Rate and mech- anism of maximal oxygen consumption decline with aging: implications for exercise training. Sports Med 2003;33:877-88. 17. Wanderley FA, Silva G, Marques E, et al. Associations between objectively assessed physical activity levels and fit- ness and self-reported health-related quality of life in community-dwelling older adults. Qual Life Res 2011;20:1371-8. 18. Harms CA, Cooper D, Tanaka H. Exercise physiology of normal develop- ment, sex differences, and aging. Compr Physiol 2011;1:1649-78. Short Report Non -co mmerc ial us e o nly