Body-composition-based determinants of cardiorespiratory fitness in a subset of the SwissHeart Study

Abstract

Introduction & Purpose: Cardiorespiratory fitness (V̇O_2,max) is a key determinant of health and functional status, yet the relative contributions of skeletal muscle mass (SMM), fat mass, and fat distribution to aerobic capacity remain incompletely understood. In particular, whether visceral adipose tissue (VAT), through its impact on inflammation and vascular health, could exert detrimental effects on cardiorespiratory fitness by itself. This study aimed therefore to evaluate the independent associations of SMM, VAT, maximal heart rate (HR_max), age and sex, with V̇O_2,max in a large cohort representing the healthy adult Swiss population.

Methods: A subset of 328 healthy adults (178 males, 41 ± 13 (mean ± SD) yrs [range 22-90 yrs], BMI 25 ± 3 kg∙m^-2, V̇O_2,max 113 ± 22 %pred.; 150 females, 42 ± 13 yrs [18-77 yrs], BMI 23 ± 3 kg∙m^-2, V̇O_2,max 113 ± 20 %pred) from the SwissHeart Study was analysed. All participants provided written informed consent and visited the lab on a single day. The protocol included segmental body composition analysis using dual-energy X-ray absorptiometry (DXA) and cardiopulmonary exercise testing (CPET) to volitional exhaustion on the bicycle using a ramp protocol.

V̇O_2,max (highest 30-s average) was expressed relative to body weight (BW). SMM was estimated from appendicular lean mass (ALM; sum of lean mass of both arms and legs; in kg) as provided by DXA generated limb area and published ALM-SMM association (McCarthy et al., 2023), expressed as % BW. VAT was quantified using the DXA device’s proprietary algorithm and expressed as percentiles (Ofenheimer et al., 2020). Sex differences were compared using parametric tests when data was normally distributed and non‑parametric tests otherwise. Level of significance was set at p<0.05.

Results: V̇O_2,max, SMM and VAT all showed slightly higher values in males compared to females (Figure 1). The multiple linear regression analysis of SMM, VAT, HR_max, sex, and age with V̇O_2,max was significant (F(5,321) = 115.6, P < 0.0001) and demonstrated substantial explanatory power for V̇O_2,max (R² = 0.64). Among predictors, SMM was the strongest determinant (estimate = 1.34, 95% CI = 1.11 to 1.57 , P < 0.0001), followed by HR_max (estimate = 0.12, 95% CI = 0.06 to 0.18 , P < 0.0001), age (estimate = -0.08 , 95% CI = -0.14 to -0.01 , P = 0.0208) and VAT (estimate = -0.04 , 95% CI = -0.07 to -0.01, P = 0.0052). Sex was not significantly associated with V̇O_2,max  after adjusting for these variables.

Discussion / Conclusion: In this relatively healthy and rather fit cohort, SMM emerged as the strongest independent and significant body-composition-derived predictor of V̇O_2,max, which highlights its central role for oxygen uptake and utilization during exercise. In parallel, higher HR_max was also independently associated with higher V̇O_2,max, reflecting the need for preserved cardiovascular responsiveness. The significant inverse association between VAT and V̇O_2,max (with all other factors adjusted for) suggests that VAT exerts an additional negative impact on cardiorespiratory fitness.

References

McCarthy, C., Tinsley, G. M., Bosy-Westphal, A., Muller, M. J., Shepherd, J., Gallagher, D., & Heymsfield, S. B. (2023). Total and regional appendicular skeletal muscle mass prediction from dual-energy X-ray absorptiometry body composition models. Sci Rep, 13(1), 2590. https://doi.org/10.1038/s41598-023-29827-y

Ofenheimer, A., Breyer-Kohansal, R., Hartl, S., Burghuber, O. C., Krach, F., Schrott, A., Wouters, E. F. M., Franssen, F. M. E., & Breyer, M. K. (2020). Reference values of body composition parameters and visceral adipose tissue (VAT) by DXA in adults aged 18-81 years-results from the LEAD cohort. Eur J Clin Nutr, 74(8), 1181-1191. https://doi.org/10.1038/s41430-020-0596-5