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

Introduction & Purpose: Cardiorespiratory fitness (V̇O2,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 (HRmax), age and sex, with V̇O2,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, V̇O2,max 113 ± 22 %pred.; 150 females, 42 ± 13 yrs [18-77 yrs], BMI 23 ± 3 kg∙m-2, V̇O2,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. V̇O2,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