Obesity is a major public health concern worldwide. According to the World Health Organization, the global prevalence of obesity tripled over the past three decades.¹ In Korea, obesity prevalence has steadily increased in all age groups.² Specially, between 2009 and 2018, the increase in obesity rates was more pronounced in individuals in their 20s.² Given that obesity is a major risk factor for numerous cardiometabolic conditions (e.g., dyslipidemia, insulin resistance, type 2 diabetes mellitus, hypertension, and others),^3-5 improved strategies are needed to reverse the rising obesity rates in young adults.

It is well documented that low cardiorespiratory fitness (CRF) is an independent predictor of all-cause and cardiovascular disease (CVD) related mortality.^6-9 Having a high CRF is associated with lower CVD risks and all-cause and CVD-related mortality, independent of body mass index (BMI) or abdominal obesity in adults.^7-11 Regular physical activity is an effective means of improving CRF12 and reducing total adiposity, even in the absence of calorie restriction.^13,14 Despite the–well-known health benefits of regular physical activity, currently 66% of Korean adults do not achieve the sufficient amount of physical activity recommended by public health guidelines.¹⁵ According to the 2021 Korea National Sports Participation Survey, the most common barrier to physical activity participation identified in Korean adults is “lack of time.”¹⁶

Recently, Allison et al.¹⁷ proposed “brief intense stair climbing” as a practical and time-efficient mode of exercise to improve CRF. They reported that 10 minutes of vigorous stair climbing exercise (three bouts of 20 seconds of “all-out” effort stair climbing interspersed with 2 minutes of recovery), performed 3 days/week for

6 weeks, significantly improved CRF in healthy young women.¹⁷ Other studies examined the effects of brief stair climbing on CRF, glycemic control, and cognitive function in healthy individuals and individuals with type 2 diabetes mellitus and coronary artery disease (CAD).^18-22 To date, it is unclear whether this type of short bursts of intense stair climbing is a feasible exercise strategy to improve CRF in individuals with overweight and obesity. Therefore, we conducted a randomized study to examine the effect of 4 weeks of a brief intense stair climbing exercise on CRF and body composition in previously sedentary, young women with overweight and obesity.

Participants

Twenty-six healthy women were recruited in Suwon City and Yongin City, Korea between June and August 2022 via flyers posted at university campuses and community centers, on social media, and by word-of-mouth. Inclusion criteria included that the participants be healthy, 20 to 39 years of age, overweight or class I obesity (23.0≤BMI<30.0 kg/m²) based on the 2018 Korean Society for the Study of Obesity Guideline for the Management of Obesity in Korea,²³ and physically inactive (no participation in structured exercise programs for past 3 months before study entry). Exclusion criteria included participation in structured regular exercise programs, the presence of CVD and psychiatric disorders, and/or the use of chronic medications related to cardiometabolic conditions (hypertension, angina, myocardial infarction, arrhythmia, diabetes etc.). Only women were included in this research, as it was a pilot feasibility study to evaluate whether this form of stair climbing exercise could be a useful strategy to improve CRF in individuals with overweight and obesity. A men’s study including cardiometabolic markers is currently ongoing. All participants in the present study provided written informed consent before study participation. Baseline and post-intervention evaluations were completed in the Obesity and Physical Activity Research Laboratory at Kyung Hee University. This study was approved by the Kyung Hee University Institutional Review Board (KHGIRB-22-264).

Randomization

This is a randomized study including two groups with two measurement time points (pre- vs. post-intervention). Participants were randomly assigned to either a stair climbing exercise group (n=13) or a non-exercising control group (n=13) by drawing lots. Randomization was performed after completing all baseline evaluations.

Anthropometric and body composition measurements

Body weight and height were measured to the nearest 0.1 kg and 0.1 cm, respectively using a mechanical column scale with stadiometer (Seca 711; Seca), with participants wearing light clothing without shoes. Waist circumference was measured to the nearest 0.1 cm at the inferior border of the last rib, and the average of two measurements was used in the analyses. Percent body fat (%), fat mass (kg) and lean body mass (kg) were determined by bioelectrical impedance analysis (InBody 430; Biospace Co. Ltd.).

Cardiorespiratory fitness

Peak oxygen uptake (VO_2peak) was determined by using a graded maximal treadmill test with the use of standard open-circuit spirometry technique (Quark CPET; COSMED). Using a constant treadmill speed, the grade was set at 0% during the first 2 minutes and at the start of the 3rd minute, the grade was increased to 2% and increased by 1% increments every minute thereafter.²⁴ VO_2peak was determined when at least two of the following three criteria were obtained:¹⁴ (1) no changes in VO₂ despite increases in exercise intensity; (2) a respiratory exchange ratio in excess of 1.1; and/or (3) heart rate >90% of the age-predicted maximum heart rate (MHR, 220-age). All subjects wore a heart rate monitor (Polar H10; Polar Electro Oy) during the test.

A 4-week brief intense stair climbing exercise regimen

Participants randomized to the stair climbing exercise group attended supervised stair climbing exercise sessions, 5 days per week (Mondays-Fridays) for 4 weeks at Kyung Hee University. In this study, we employed the brief intense stair climbing protocol suggested by Allison et al.¹⁷ Briefly, the stair climbing exercise began with a 3-minute warm-up followed by three bouts of 20 seconds of vigorously ascending stairs (≥80% of age-predicted MHR) interspersed with 2-minute recovery periods (e.g., self-paced descending stairs) (Fig. 1). The total exercise protocol including warm-up lasted 10 minutes per session. During each stair climbing interval, participants were instructed to ascend six flights of stairs (a total of 77 steps, step height=16 cm), as quickly as possible, one step at a time. Participants were asked to safely climb the stairs and use the railings as necessary. During each exercise session, heart rate was measured by the Polar H10 sensor chest strap device (Polar Electro Oy) to access exercise intensity, and the heart rate data was downloaded on a computer using the Polar Beat application version 3.5.5 (Polar Electro Oy). On the weekends, participants were asked to perform the vigorous stair climbing exercise at home or the workplace using public access staircases (data not available). Participants in the non-exercising control group were asked to maintain their current leisure time activity during a 4-week intervention period. All subjects were advised to maintain their usual diet during the study.

Statistical analysis

Statistical analyses were performed using IBM SPSS Statistics software version 26.0 (IBM). The power calculations using G*Power 3.1 were based on the changes in CRF (VO_2peak) observed in the previous study.¹⁷ Using an alpha of 0.05 with an expected effect size 1.163, the sample size was calculated as such with 13 subjects in each group (totaling 26 subjects), with 80% power. Differences in participant characteristics between groups at baseline were examined using independent t-tests. A one-way repeated-measures analysis of variance (ANOVA) was employed to test for differences in the mean heart rate and peak heart rate between bouts. A two-way repeated measures ANOVA was used to examine main treatment effects (group, time) and interactions (group×time) for all dependent variables. Paired t-tests were conducted to evaluate within group changes for all dependent variables. All data are presented as mean±standard deviation. The level of significance for all analyses was set at P≤0.05.

Baseline characteristics are shown in Table 1. There were no differences (P>0.05) between groups with respect to age, anthropometric measurements, body composition, and VO_2peak at baseline.

Four weeks of stair climbing exercise summary

Of the 26 participants randomized, 25 completed their assigned treatment group. One participant in the stair climbing exercise group did not complete the study due to coronavirus disease 2019 (COVID-19) infection. Twelve participants in the exercise group completed all supervised exercise sessions without incident (100% attendance).

Heart rate responses during the supervised stair climbing exercise sessions were shown in Fig. 2. Both mean heart rate (136.7±10.2, 145.8±11.0, 150.0±11.1 beats/minute, P<0.01), and peak heart rate (158.6±10.0, 167.0±8.7, 169.8±7.7 beats/minute, P<0.01) significantly increased with each subsequent bout. Mean heart rate during the 10-minute exercise session was 131.0±9.5 beats/minute, corresponding to 68% of age-predicted MHR, and peak heart rate reached 170.0±7.7 beats/minute, corresponding to 88% of age-predicted MHR.

Changes in CRF and body composition following 4 weeks of stair climbing exercise

There were significant interaction effects (group×time) for body weight, BMI, and waist circumference, indicating that these measurements were significantly reduced (P<0.05) in the stair climbing exercise group versus control group (Table 1). Compared with controls, VO_2peak significantly increased by 10% (31.6±2.5 to 34.9±2.6 mL/kg/min, P<0.01) in the stair climbing exercise group (Fig. 3).

The purpose of this study was to examine whether “brief vigorous stair climbing” is an effective exercise strategy for improving CRF and body composition in previously sedentary, young women with overweight or obesity. We observed that 4 weeks of brief intermittent stair climbing exercise, which involved three bouts of 20 seconds of high intensity stair climbing exercise interspersed with 2-minute recovery periods (total exercise duration of 10 minutes/day, 5 days/week), resulted in significant improvements in VO_2peak, and modest but significant reductions in body weight, BMI, and waist circumference. These findings provide evidence that young women with overweight or obesity can tolerate 20 seconds of vigorous continuous stair climbing without incident, and that stair climbing is an effective and time-efficient mode of exercise to improve cardiovascular health.

Using a randomized study design, our findings extend the previous observations by Allison et al.¹⁷ who demonstrated significant improvements in VO_2peak (12%) following 6 weeks of high-intensity stair climbing exercise in healthy young women (n=12). These findings are also in line with the study by Dunford et al.¹⁸ who reported that a 12-week brief vigorous stair climbing exercise (three bouts of climbing 72 stairs separated by 90-second of recovery) significantly improved VO_2peak in older patients with CAD. Although the mechanisms by which stair climbing is associated with improvement in VO_2peak remains unclear, it has been suggested that brief intermittent stair climbing exercise is associated with skeletal muscle adaptations.^17,19 Taken together, these findings suggest that short bouts of vigorous stair climbing may provide health benefits in individuals with obesity or CAD.

Low-volume high-intensity interval training (HIT) has received considerable attention in the literature as a strategy to promote health. Despite low time-commitment, a number of studies have shown comparable or greater improvements in CRF and cardiometabolic risk factors in response to low-volume HIT as compared to traditional continuous moderate-intensity aerobic exercise.^25-28 However, the vast majority of HIT studies have been conducted in laboratory settings using expensive exercise equipment (e.g., cycle ergometers and treadmills) that are not transferable to real-world settings. Given that “lack of time” and “lack of access to exercise facilities” are commonly cited barriers to exercise participation in adults,²⁹ stair climbing exercises offer a low-cost and practical form of HIT that can be easily integrated at home and at the workplace.

In this study, we did not observe increases in lean body mass after the stair climbing exercise. This may be due to the relatively short duration of the exercise intervention period or the methodology employed. Using muscle biopsy, Lim et al.¹⁹ recently have shown that 12 weeks of a stair climbing-based exercise program (3 days per week, average exercise time, 5±2 minutes/session) resulted in significant improvements in skeletal muscle characteristics, such as increasing the number of satellite cells, myonuclei, and capillary-related perfusion capacity, similar to those observed in a traditional moderate-intensity continuous exercise program (3 days per week, average exercise time, 33±8 minutes/session) in CAD patients. These findings suggest that a brief intense stair climbing exercise confers health benefits and may be a practical alternative to traditional cardiac rehabilitation exercise programs despite a lower exercise volume and time commitment.¹⁹

The strengths of the present study include (1) the randomized study design; (2) excellent attendance at the exercise sessions (100% attendance rates); and (3) direct supervision of the stair climbing exercise sessions (5 days/week over 4 weeks) with automated monitoring of the heart rate. The limitations of this study also warrant mention. Study participants were healthy Asian women with overweight and obesity. Whether our findings would remain true in men, different races and age groups, or individuals with metabolic conditions is unclear. In this study, we did not evaluate changes in cardiometabolic risk factors. Prospective studies with comprehensive assessments of obesity-related risk factors are needed to examine the metabolic effects of a brief intense stair climbing exercise in individuals with obesity. Although subjects were asked to log their energy intake before and in the last week of intervention, this was done poorly.

In conclusion, brief vigorous stair climbing is a feasible and time-efficient exercise strategy for improving CRF and body composition in previously sedentary, young women with overweight and obesity. Stair climbing is an easily accessible and practical mode of exercise that can be incorporated into daily activities.

The authors declare no conflict of interest.

The authors would like to express their gratitude to the study participants.

Study concept and design: SL; acquisition of data: JEY, XW, MH, and SC; analysis and interpretation of data: JEY, XW, MH, SC, JLK, and SL; drafting of the manuscript: JEY and SL; critical revision of the manuscript: XW, MH, SC, and JLK; statistical analysis: JEY, XW, MH, SC, and SL; administrative, technical, or material support: JEY, XW, MH, and SC; and study supervision: SL.