Physical activity, sedentary time, and fitness parameters of cardiopulmonary exercise testing: a compositional data analysis among a population-based adult sample
Authors: Roosz A , Bahls M , Ulbricht S , Ullrich A , Obst A , Stubbe B , Ewert R , Kaczmarek S , Ittermann T , Doerr M , Voigt L 
Published: June 2024

Abstract

Background
While physical activity and cardiorespiratory fitness are often considered as surrogates, their exact relationship remains unclear. Besides cardiorespiratory fitness (i.e., maximal oxygen consumption; VO2peak), other parameters can be measured by cardiopulmonary exercise testing (CPET). Information from these may lead to a better understanding of the systemic response to physical activity. Compositional data analysis is a novel method that accounts for the relative contribution of different movement behaviours to the overall time budget of the waking day.

Purpose
The aim was to investigate associations of moderate-vigorous physical activity (MVPA), light physical activity (LPA), and sedentary time (ST) with the following parameters: VO2 at rest, VO2 at the anaerobic threshold (VO2VT1), VO2peak, VO2 recovery 60s, predicted VO2peak, change of VO2 with increasing work (VO2/work), O2 pulse, and maximum heart rate.

Methods
In total, complete data was used from 1396 participants of the population-based Study of Health in Pomerania (SHIP-TREND-1) who wore ActiGraph GT3X+ accelerometers (Pensacola, FL) on the hip for seven consecutive days and performed CPET on a cycle ergometer. Linear regression models were used to examine associations of movement behaviours with CPET parameters, normalized for body weight and stratified by sex. Models were adjusted for age, smoking, education, and living in a partnership. According to compositional data analysis, MVPA, LPA, and ST were expressed as proportions of total accelerometer wear time and transformed into isometric log-ratios. Because regression coefficients and confidence intervals are not directly interpretable, they are omitted in the results section.

Results
Participants were on average 57.1 years old (SD 13.2) and 51 % were men. The mean accelerometer wear time was 14.4 hours/day (SD 1.5). The mean proportion of time spent in MVPA, LPA, and ST was 5 %, 24 %, and 71 %, respectively. In both men and women, the proportion of time spent in MVPA was positively associated with VO2VT1, VO2peak, predicted VO2peak, and VO2 recovery 60s. Higher MVPA was also related to higher maximum heart rate in men and to higher VO2/work in women. In both sexes, the proportion of time spent sedentary was inversely associated with predicted VO2peak. Higher ST was also related to lower VO2VT1, VO2peak, and VO2/work in men and to lower VO2 recovery 60s and O2 pulse in women. The proportion of time spent in LPA was inversely associated to VO2/work in women, only. All other associations were not statistically significant (p values &gt; 0.05).

Conclusion
Proportions of MVPA, LPA, and ST were differently associated with various CPET parameters and these relations differed by sex. Our findings suggest that the relative amount of time spent in different movement behaviours contribute differently to systemic response to physical activity and ST.