Correlation between 10-meter walking speed and exercise capacity in patients with surgical resection for lung cancer

Abstract

Surgical resection for lung cancer adversely impacts exercise capacity. The 6-minute walk test (6MinWT) and cardiopulmonary exercise test (CPET) are commonly used to assess exercise capacity. However, these tests are difficult to use clinically because they must be performed by a trained technician using specialized equipment according to a prescribed method. This study aims to analyze correlations between walking speed in a 10-meter walk test and exercise capacity measured by the 6MinWT or CPET in patients with lung resection for lung cancer. A total of 50 patients who were diagnosed with lung cancer and underwent lung resection were included in the analysis. The 6MinWT and CPET were performed to measure exercise capacity, and the 10-meter walk test was used to evaluate the short-duration walking speed. The population was divided into 2 groups –low and high exercise capacity – based on threshold values (6MinWT, 500 m; CPET, 20 mL·kg⁻¹·min⁻¹); we analyzed the correlation according to the level of exercise capacity. In the correlation analysis between the 10-meter walking speed and exercise capacity, the 10-meter walking speed showed a strong correlation (R = 0.70, P < .001) with the 6MinWT and a moderate correlation (R = 0.47, P < .001) with the CPET, respectively. The low exercise capacity group showed a significant correlation (6MinWT, ρ = 0.70; CPET, ρ = 0.54) between the 10-meter walking speed and exercise capacity, while the high exercise capacity group did not. In patients who underwent lung resection for lung cancer, the 10-meter walking speed was significantly correlated with exercise capacity, especially in subjects with low exercise capacity that require pulmonary rehabilitation.

1. Introduction

Globally, lung cancer has the second highest incidence rate of all cancers combined (14.3% in males and 8.4% in females) and is a leading cause of cancer-related mortality (of all cancer death: 21.5% in males and 13.7% in females).^[1] Due to the increasing use of computed tomographic screening for the early detection of lung cancer and advancements in surgical techniques such as video-assisted thoracoscopic surgery (VATS), the mortality rates and postoperative complications associated with lung cancer have been decreasing.^[2,3] Despite these advances, lung cancer survivors experience a variety of long-term health impairments and reduced quality of life due to surgical resection of the lung and adjuvant treatments such as chemotherapy and radiotherapy, which adversely affect multiple organs, including the lung, heart, and musculoskeletal system.^[4,5] This combination of multifactorial causes leads survivors to have decreased exercise capacity.^[6]

Pulmonary rehabilitation is recommended for lung cancer patients at all time points, including pre- and postoperatively, to reduce the incidence of lung cancer-related impairments and improve exercise capacity in survivors.^[7,8] The cardiopulmonary exercise test (CPET) and 6-minute walk test (6MinWT) are commonly used in clinical practice to evaluate the physical function of lung cancer patients for risk stratification to select candidates for pulmonary rehabilitation and apply an individualized pulmonary rehabilitation program to the patient’s condition.^[9] Previous studies have reported that patients with maximal oxygen consumption (VO₂max) < 15 mL·kg⁻¹·min⁻¹ on preoperative CPET may benefit from pulmonary rehabilitation,^[10] and a decline in the distance of the 6MinWT is used as a criterion for determining deterioration in exercise capacity after lung cancer surgery.^[11]

However, the CPET requires exercise-testing equipment such as a treadmill or cycle ergometer, gas analyzer, and electrocardiogram, and the test must be performed by a trained technician with basic knowledge of exercise responses.^[12] Additionally, the 6MinWT requires a 30-meter walking course and must be evaluated by a trained technician using a standard protocol.^[13] Furthermore, both exercise tests are difficult to perform in subjects with conditions such as severe arthritis or other musculoskeletal disorders and neurological deficits.^[14]

In contrast, the 10-meter walk test (10mWT) is a common and simple method of assessing walking speed that can be performed by anyone and is used to assess mobility in patients with neurological impairments such as stroke and Parkinson disease, as well as in healthy older adults.^[15,16] Previous studies have reported a strong correlation between the walking speed in the 10mWT and exercise capacity measured at the 6MinWT in patients with neurological impairments such as stroke, multiple sclerosis, and Parkinson disease, as well as in patients with head and neck cancer or older adults with dementia.^[17–20] However, in our review of previous studies, we found no studies on the correlation between the 10-meter walking speed and exercise capacity in the 6MinWT or CPET in patients undergoing lung resection for lung cancer.

This study aims to analyze the correlation between the walking speed in the 10mWT and exercise capacity measured by the CPET or 6MinWT in patients who have undergone lung resection for lung cancer.

2. Methods

2.1. Study design and subjects

In this single-center, cross-sectional study, we recruited a total of 65 patients who visited the rehabilitation department for outpatient pulmonary rehabilitation after undergoing VATS or open thoracotomy for histologically confirmed lung cancer between March 2019 and August 2022. Of these, we included the following patients: those who consented to perform physical function testing for pulmonary rehabilitation prescription, and those who had no contraindications to performing physical function tests such as the 6MinWT and CPET.^[12,13] In contrast, we excluded the following patients from the analyses: those who refused to perform physical function tests (n = 3), those who did not perform all physical function tests required for the analysis (n = 3), and those who had insufficient medical records for the analysis (n = 9) (Fig. 1). Ethical approval was obtained from the Institutional Review Board of Chungbuk National University Hospital (IRB number: 2022-08-009-001).

Figure 1.

Flow chart of patient selection.

2.2. Outcome measures

The 6MinWT and CPET were performed to assess the subjects’ exercise capacity. The 6MinWT was evaluated by trained technicians according to American Thoracic Society guidelines. In this test, subjects were instructed to walk “as far as possible (don’t run or jog)” for 6 minutes on a 30-meter walking course with turning points marked by orange traffic cones and marked on the ground every 3 m, with no words of encouragement from the technician to speed up the subjects. The total distance walked in 6 minutes was then recorded in meters (m).^[13]

The CPET was performed by a trained technician as a symptom-limited treadmill test (using the modified Bruce protocol) using the COSMED CPET® (COSMED Inc., Pavona di Albano, Italy).^[21] During the test, heart rate was monitored by electrocardiogram and blood pressure was measured every 3 minutes. Exercise capacity was assessed by measuring oxygen consumption (VO₂, mL·kg⁻¹·min⁻¹), and VO₂max was defined as the state where VO2 reaches a plateau despite the increasing workload.^[12]

Furthermore, the 10mWT was conducted by measuring the time taken to walk the middle 10 m of a 14-meter walkway “as fast as possible (running not allowed),” with 2 m each of acceleration and deceleration. The subject’s walking speed (m/s) was defined as the maximum walking speed taken from 3 trials.^[20]

2.3. Groups based on exercise capacity levels

To analyze the correlation between 10-meter waking speed and exercise capacity on exercise testing according to the exercise capacity level, we divided patients undergoing surgical resection for lung cancer into 2 groups based on cutoff values (6MinWT, 500 m; CPET, 20 mL·kg⁻¹·min⁻¹) that predict survival and various complications.^[9,22,23]

2.4. Statistical analysis

Continuous variables are presented as means and standard variances, while categorical variables are presented as numbers and proportions. We used Pearson correlation or Spearman correlation to analyze the correlation between the 10mWT and the exercise tests, and the correlation coefficients were interpreted as negligible (<0.10), weak (0.10–0.39), moderate (0.40–0.69), or strong (0.70–0.89) correlations.^[24] Using GPower 3.1 software (Universitat Kiel, Kiel, Germany), the sample size calculation required a minimum of 46 individuals to detect at least a moderate correlation (R ≥ 0.40) with 80% power and 95% confidence. To compare the 10-meter walking speed with the walking speed from the 6MinWT, we performed paired t-test or the Wilcoxon signed-rank test. All statistical analyses were performed using SPSS version 25.0 (IBM Corporation, Chicago, IL), and analyses with P-values < .05 were considered statistically significant.

3. Results

3.1. Baseline characteristics

Table 1 shows the baseline sociodemographic and clinical characteristics of the subjects. A total of 50 subjects (mean age, 63.0 ± 9.2 years) were included in the analysis, of whom 28 (56%) were men. The most common cancer stage among the participants was stage I (n = 29, 58%), followed by stages II (n = 12, 24%), III (n = 4, 8%), and IV (n = 5, 10%). Most subjects underwent VATS (n = 41, 82%) and the extent of lung resection was mostly lobectomy (n = 44, 88%). Moreover, 7 subjects (14%) had received chemotherapy prior to the exercise test. The average time from surgery to the exercise testing was 30.5 ± 19.4 days. In the exercise tests, the subjects’ average walking distance in the 6MinWT was 506.0 ± 99.3 meters and their average VO₂max in the CPET was 21.3 ± 4.8 mL·kg⁻¹·min⁻¹. Furthermore, the average walking speed of the subjects at 10mWT was 1.34 ± 0.26 m/s (Table 1).

Table 1.

Patient characteristics (N = 50)

Variable	Data
Age, years	63.0 ± 9.2
Sex, males	28 (56%)
BMI, kg/m2	23.6 ± 2.3
Smoking
Nonsmoker	22 (44%)
Current or ex-smoker	28 (56%)
Cancer stage
IA/IB	26 (52%)/3 (6%)
IIA/IIB	6 (12%)/6 (12%)
IIIA	4 (8%)
IVA	5 (10%)
Type of surgery
Open thoracotomy	9 (18%)
VATS	41 (82%)
Extent of resection
Lobectomy	44 (88%)
Bilobectomy	6 (12%)
Adjuvant treatments
Chemotherapy	7 (14%)
Radiotherapy	0 (0%)
Assessment time, days from surgery	30.5 ± 19.4
6-minute walk test, m	506.0 ± 99.3
VO2max, mL·kg−1·min−1	21.3 ± 4.8
10-meter walk test, m/s	1.34 ± 0.26

Data are presented as mean ± standard deviation and n (%)

BMI = body mass index, VATS = video-assisted thoracoscopic surgery, VO₂max = maximal oxygen consumption.

3.2. Correlation between the 10-meter walking speed and exercise capacity

Table 2 shows the correlation between the walking speed in the 10mWT and exercise capacity as measured by exercise tests (6MinWT, distance; CPET, VO₂max). There was a strong correlation between the 10-meter walking speed and the distance of the 6MinWT (R = 0.70, P < .001) and a moderate correlation between the 10-meter walking speed and the VO₂max from the CPET (R = 0.47, P < .001). In addition, there was a significant correlation (R = 0.68, P < .001) between the distance of the 6MinWT and the VO₂max from the CPET (Table 2 and Fig. 2).

Table 2.

Correlations between the results of the 10-meter walk test and the exercise tests

	10mWT	6MinWT	CPET
10mWT		R = 0.70 P < .001	R = 0.47 P < .001
6MinWT			R = 0.68 P < .001

10mWT = 10-meter walk test, 6MinWT = 6-minute walk test, CPET = cardiopulmonary exercise test.

Figure 2.

Correlations between data of (A) the 10mWT and 6MinWT (R = 0.70, P < .001), and (B) the 10mWT and cardiopulmonary exercise test (R = 0.47, P < .001). 6MinWT = 6-minute walk test, 10mWT = 10-meter walk test, VO₂max = maximal oxygen consumption.

3.3. Analysis of the correlation between the 10-meter walking speed and exercise capacity according to the exercise capacity level

Table 3 shows the correlation between the results of the 10mWT and the exercise tests according to the level of exercise capacity (cutoff point: 6MinWT, 500 m; CPET (VO2max), 20 mL·kg⁻¹·min⁻¹).^[9,22,23] The low exercise capacity group had a significant correlation between the 10-meter walking speed and exercise capacity in the 6MinWT, while the high exercise capacity group did not (ρ = 0.70, P < .001 vs ρ = 0.20, P = .320). The same trend was observed between the results of the 10mWT and the CPET (ρ = 0.54, P = .020 vs. R = 0.22, P = .224).

Table 3.

Analysis of the correlation between the 10-meter walking speed and exercise capacity according to the exercise capacity level

	6MinWT (distance, m)		CPET (VO2max, mL·kg−1·min−1)
	<500 (N = 22)	≥500 (N = 28)	<20 (N = 18)	≥20 (N = 32)
Correlation	ρ = 0.70	ρ = 0.20	ρ = 0.54	R = 0.22
Coefficient	P < .001	P = .320	P = .020	P = .224
Walking speed
10mWT (m/s)	1.16 ± 0.19	1.48 ± 0.23	1.22 ± 0.26	1.41 ± 0.24
6MinWT (m/s)	1.15 ± 0.19*	1.61 ± 0.11**	1.21 ± 0.27***	1.51 ± 0.21****

6MinWT = 6-meter walk test, 10mWT = 10-meter walk test, CPET = cardiopulmonary exercise test, r = Pearson correlation coefficient, VO₂max = maximal oxygen consumption, ρ = Spearman’s rank correlation coefficient.

^*P = .355.

^**P = .013.

^***P = .744.

^**** P = .038.

In addition, the correlation between the 10-meter walking speed and the walking speed of the 6MinWT (distance covered during the 6MinWT (m)/360 s)^[25] was analyzed according to the exercise capacity level. We found no significant difference between the 10-meter walking speed (1.16 ± 0.19 m/s) and the walking speed of the 6MinWT (1.15 ± 0.19 m/s) in the low exercise capacity group (P = .355); however, in the high exercise capacity group, the walking speed of the 6MinWT (1.61 ± 0.11 m/s) was significantly faster than the 10-meter walking speed (1.48 ± 0.23 m/s) (P = .013). This trend was also observed when the analysis was performed according to the level of exercise capacity from the CPET (Table 3 and Fig. 3).

Figure 3.

Correlations between data of (A) the 10mWT and 6MinWT (white dot: 6minWT < 500 m, ρ = 0.70, P < .001; black dot: 6minWT ≥ 500 m, ρ = 0.20, P = .320), and (B) the 10mWT and CPET (VO₂max) (white dot: VO₂max < 20 mL·kg^-1·min^-1, ρ = 0.54, P = .020; black dot: VO₂max ≥ 20 mL·kg⁻¹·min⁻¹, R = 0.22, P = .224). 6MinWT = 6-minute walk test, 10mWT = 10-meter walk test, CPET = cardiopulmonary exercise test; VO₂max = maximal oxygen consumption.

4. Discussion

In the correlation analysis between the 10-meter walking speed and exercise capacity, the 6MinWT had a strong correlation, while the CPET had a moderate correlation. Additionally, in the correlation analysis according to the level of exercise capacity, the group with a low exercise capacity showed a significant correlation between the 10-meter walking speed and exercise capacity in the exercise tests (6MinWT and CPET). And there was no significant difference between the 10-meter walking speed and the walking speed of the 6MinWT in the low exercise capacity group.

There was a strong correlation (R = 0.70) between the 10-meter walking speed and exercise capacity as measured by the 6MinWT in this study. Previous studies have reported a similar correlation between the 10-meter walking speed and 6-minute walking distance in healthy subjects (R = 0.69),^[20] as well as similar results in patients with head and neck cancer (R = 0.68).^[17] The 10mWT is commonly used in clinical practice to measure walking speed,^[15] while the 6MinWT is commonly used to measure functional exercise capacity.^[13] Since the 6MinWT is performed for 6 minutes, the test results reflect not only walking speed but also walking endurance in terms of walking capacity.^[20] Therefore, both the 10mWT and the 6MinWT share the component of measuring walking speed among the physical functions, which may explain the high correlation between these 2 tests in our study. However, while the 6MinWT requires that the test be performed by a trained technician according to established guidelines to ensure that the results are reliable, the 10mWT can be easily performed on an outpatient basis without this limitation. This makes it a simple screening marker for recommending exercise testing to assess exercise capacity in patients who have undergone lung cancer surgery.

Notably, there was a significant correlation (moderate, R = 0.47) between the 10-meter walking speed and the VO₂max from the CPET in this study. Previous studies have shown the correlation between a short walking speed with VO₂max in healthy older adults or patients with stroke^[26,27]; however, to our knowledge, no previous studies have correlated the 2 measures in lung cancer patients. Importantly, rather than representing the individual functions of the organ systems involved in exercise, including the pulmonary, cardiovascular, and skeletal muscle systems, the CPET provides a global assessment of the integrative exercise response of each organ involved in exercise capacity.^[12] In the same way that the walking speed in the 10mWT is a reflection of an individual’s overall health status, not just mobility, it has been called the sixth vital sign.^[28] Therefore, it was assumed that the 10-meter walking speed and exercise capacity according to the CPET would show a significant correlation in this study. However, the degree of this correlation was lower for the CPET than for the 6MinWT. The CPET is performed as a symptom-limited maximal incremental exercise using a treadmill; therefore, the level of exercise intensity required of subjects is higher than that for the 6MinWT, which is performed as a self-paced exercise and is classified as a submaximal test.^[9,12] Furthermore, while the 10mWT instructs the subject to walk “as fast as possible (don’t jog or run)” and the 6MinWT instructs the subject to walk “as far as possible (don’t jog or run),” the CPET requires running as the exercise intensity gradually increases. Therefore, we assume that this is the reason for a lower correlation than the 6MinWT showed with the 10-meter walking speed. Nevertheless, our study results are significant as they are the first to show a statistically significant correlation between VO₂max from the CPET and the 10-meter walking speed in lung cancer surgery patients.

In a subgroup analysis according to the exercise capacity levels, the low exercise capacity group had a significant correlation between the 10-meter walking speed and exercise capacity, while the high exercise capacity group did not. In addition, the low exercise capacity group did not show a significant difference between the 10-meter walking speed and the walking speed of the 6MinWT (Table 3). In previous studies, patients of stroke or multiple sclerosis with a low exercise capacity showed a higher correlation between their 10-meter walk speed and 6-minute walk distance compared to high exercise capacity group.^[20,29] Since walking capacity consists of 2 components (walking speed and endurance),^[30] it was presumed that there was no difference in walking speed between the short-walk test and the 6-minute walk test because subjects with low exercise capacity had a reduced ability to perform the submaximal exercise for 6 minutes without fatigue in the 6MinWT. Clinicians typically recommend pulmonary rehabilitation to patients who have undergone surgery for lung cancer and who are risk-stratified by the cutoff point defined in this study (6MWT, 500 m; CPET, 20 mL·kg⁻¹·min⁻¹) as the low exercise capacity group.^[9] Based on the results of this study, the 10mWT can be used as a simple marker to screen subjects with a low exercise capacity who require pulmonary rehabilitation.

The present study had some limitations. First, due to the relatively small sample size, it was difficult to perform subgroup analyses according to age, sex, and cancer stage. Furthermore, as it was a single-center study (Asian population), our results cannot be generalized to people of other races or regions. Therefore, additional multicenter, larger sample studies are required to address the present limitations. Despite these limitations, this study had several strengths. Notably, to our knowledge, this study is the first to show a significant correlation between the 10-meter walking speed and exercise capacity in patients who have undergone lung resection for lung cancer. Moreover, unlike previous studies, we have shown the correlation of the results between the 10mWT and CPET.

5. Conclusion

In patients who underwent lung resection for lung cancer, the 10-meter walking speed was significantly correlated with the exercise capacity measured by the 6MinWT or CPET, especially in subjects with a low exercise capacity that require pulmonary rehabilitation. Therefore, the use of the 10mWT as a simple marker to screen for exercise capacity in patients who have undergone lung cancer surgery may help clinicians identify patients who require pulmonary rehabilitation.

Author contributions

Conceptualization: Han Tae Kim, Joong Ho jo.

Formal analysis: Han Tae Kim, Hyun-Ho Kong.

Methodology: Han Tae Kim, Joong Ho jo.

Visualization: Han Tae Kim.

Writing – original draft: Han Tae Kim.

Data curation: Soo Jeong Jo.

Resources: Dohun Kim, Si-Wook Kim, Seung Hyuk Nam.

Investigation: Hyun-Ho Kong.

Project administration: Hyun-Ho Kong.

Supervision: Hyun-Ho Kong.

Writing—review & editing: Hyun-Ho Kong.