The impact of physical activity level, degree of dyspnoea and pulmonary function on the performance of healthy young adults during exercise

Abstract

Background

In addition to being simple and requiring minimal technology, the 6-min walk test (6MWT) has been found to be reproducible and well tolerated since its first use. However, the impact of non-anthropometric factors on functional capacity is less clear in healthy young adults because the majority experience no age-related changes in the locomotor system or associated comorbidities.

Aim

To identify the effect of physical activity level, degree of dyspnoea and pulmonary function on functional capacity, evaluated through the 6-min walking distance (6MWD) of healthy young adults, in order to prevent clinical abnormalities.

Method

This is a cross-sectional study including 190 healthy young adults who were subjected to the 6MWT to assess walking distance and degree of dyspnoea using the Borg scale. Furthermore, pulmonary function using spirometry and physical activity level using the International Physical Activity Questionnaire (IPAQ) were assessed. According to the IPAQ, the subjects were categorised as sedentary, irregularly active or active.

Results

The 6MWD was positively correlated with pulmonary function parameters (P ≤ 0.002 for all parameters). There was a marginally significant correlation between the 6MWD and the difference between the scores assessed before and after the test using the Borg scale. There was a trend towards significant differences in 6MWD according to the IPAQ categories. Furthermore, forced vital capacity was the only pulmonary function parameter with significant differences between IPAQ categories (P = 0.02).

Conclusion

In healthy young adults, greater pulmonary function indicates a greater 6MWD. In these subjects, physical activity level based on the IPAQ categories clearly affects pulmonary function. However, the IPAQ category and degree of dyspnoea are poorly related to the 6MWD of these subjects.

Introduction

The act of walking is considered one of the five main activities of daily living (ADLs), along with the acts of breathing, hearing, seeing and speaking (Ambrosino, 1999). Accordingly, functional walking tests have been proposed to measure the functional capacity of individuals with various health conditions. The 6-min walk test (6MWT) is used to evaluate the response of an individual to exercise and provides a general analysis of the respiratory, cardiac and metabolic systems (ATS Committee on Proficiency Standards for Clinical Pulmonary Function Laboratories, 2002). It assesses the distance a person is able to travel on a flat, rigid surface in 6 min and primarily aims to determine exercise tolerance during a submaximal exercise. The 6MWT has been used worldwide as a predictor of mortality in various conditions, including heart failure, chronic obstructive pulmonary disease (COPD) and pulmonary hypertension (Reibis et al., 2010; Golpe et al., 2013). The variability in the 6-min walking distance (6MWD) has been explained, at least partly, by gender, age, height and weight differences (Morales-Blanhir et al., 2011). However, predictive equations have, at best, coefficients of determination of 0.4, which means that 60% of the 6MWD variability amongst healthy individuals remains undetermined (Neder, 2011).

Several studies have shown the efficacy of regular physical activity in preventing chronic diseases, such as cardiovascular diseases, obesity, diabetes, cancer and osteoporosis. It has been suggested that the level of physical activity and health status are significantly associated; thus, increased physical fitness may result in additional health benefits (Warburton et al., 2006). In some clinical conditions, the 6MWD is correlated with performance in ADLs because functional capacity is closely linked with the energy expenditure required for physical activities and an increased ADL ability (Westerterp, 2013). In patients with COPD, for example, a higher 6MWD has been associated with a greater level of physical activity in daily life (Hernandes et al., 2009). Thus, the interest in assessing the effects of a sedentary lifestyle has been increasing due to its association with risk factors such as low aerobic capacity and peripheral vascular endothelial dysfunction (Riess et al., 2006).

Dyspnoea, which is usually described by patients as “shortness of breath”, is a common, albeit unspecific, symptom and is associated with exercise performance and, therefore, with health-related quality of life (HRQoL). Population-based studies suggest a 9–35% prevalence of unexplained exertional dyspnoea amongst community-residing adults (Parshall et al., 2012; Huang et al., 2017). Measuring dyspnoea provides an independent dimension not given by pulmonary function tests (PFTs). Therefore, assessing dyspnoea affects and predicts HRQoL and survival more broadly than physiological measures (Camargo and Pereira, 2010). In recent years, numerous studies have suggested that the sensation of dyspnoea does not involve a single perception but rather a set of diverse sensations (Parshall et al., 2012; Mendonca et al., 2014). Despite these advances in the understanding of mechanisms involved in dyspnoea, little is known about the variability of the perception of dyspnoea amongst healthy individuals, whether at rest or under effort (Ziegler et al., 2015).

The association between pulmonary function and exercise performance has been previously studied in several clinical conditions, showing contradictory results between groups of patients with different diseases and even between different groups of patients with the same disease (Rodrigues and Viegas, 2002; Pimenta et al., 2010; Ho et al., 2015). The hypothesis that 6MWT contributes to the classical assessment of pulmonary function and is thus able to provide a more complete profile of the functional capacity of healthy individuals has been previously postulated (Zenteno et al., 2007). However, to our knowledge, the relationship between pulmonary function and 6MWD has been examined only in patients and elderly people, indicating a gap in this type of assessment in healthy young individuals.

In recent years, exercise tests have been recognised as a convenient tool to determine the functional capacity dynamically because the reserves of the various body systems must be known to assess in greater detail the functional capacity of individuals. In addition to anthropometric and demographic data, differences in functional status may be statistically significant and yet lower than the threshold at which individuals notice a difference between their performance and that of others (Redelmeier et al.,1997). Thus, the objective of the present study was to identify the effect of physical activity level, degree of dyspnoea and pulmonary function on functional capacity, evaluated through the 6MWD of healthy young adults, in order to prevent clinical abnormalities.