Adults with initial metabolic syndrome have altered muscle deoxygenation during incremental exercise

Reduced aerobic power is independently associated with metabolic syndrome (MetS) incidence and prevalence in adults. This study investigated whether muscle deoxygenation (proxy of microvascular O₂ extraction) during incremental exercise is altered in MetS and associated with reduced oxygen consumption ( V˙O_2peak ).

Twelve men with initial MetS (no overt diseases and medication-naive; mean ± SD, age 38 ± 7 years) and 12 healthy controls (HCs) (34 ± 7 years) completed an incremental cycling test to exhaustion, in which pulmonary ventilation and gas exchange (metabolic analyzer), as well as vastus lateralis deoxygenation (near infrared spectroscopy), were measured.

Subjects with MetS, in contrast to HCs, showed lower V˙O_2peak normalized to total lean mass, similar V˙O₂ response to exercise, and earlier break point (BP) in muscle deoxygenation. Consequently, deoxygenation slope from BP to peak exercise was greater. Furthermore, absolute V˙O_2peak was positively associated with BP in correlations adjusted for total lean mass.

MetS, without overt diseases, altered kinetics of muscle deoxygenation during incremental exercise, particularly at high-intensity exercise. Therefore, the balance between utilization and delivery of O₂ within skeletal muscle is impaired early in MetS natural history, which may contribute to the reduction in aerobic power.