Investigating the relationship between aerobic fitness and lower-limb resistance vessel function before and after a bout of uninterrupted sitting.

Abstract

Prolonged sitting reduces lower-limb resistance vessel function (RVF), whereas increasing aerobic fitness levels enhance lower-limb RVF. However, it is unknown if having higher aerobic fitness offers protection against prolonged sitting-induced declines in RVF. This study investigated the relationships between aerobic fitness versus reductions in lower-limb RVF following a 3-hour bout of uninterrupted sitting. In 30 healthy young to middle aged adults (19♀, 24±6 years), aerobic fitness was assessed during a graded, maximal cycling test. Relative peak oxygen consumption (V̇O2peak) was determined via indirect calorimetry [37.5±8.6 (24.7-60.7 mlO2/kg/min]. Popliteal blood flow (PBF) was recorded via duplex ultrasonography. Lower-limb RVF was assessed in the seated posture and quantified as the peak PBF and area under the curve (PBFAUC, first minute of hyperemia) responses to 5-min of distal cuff-induced ischemia. The lower-limb RVF assessment was performed before and after a sitting. Peak PBF decreased following sitting (473±254 to 387±199 mL/min, P=0.024), while PBFAUC remained unchanged (6145±3063 versus 6446±3826 mL, P=0.758). Relative V̇O2peak was not associated with Pre-Sitting Peak PBF (R=0.236, P=0.210) or PBFAUC (R=-0.026, P=0.889). Furthermore, relative V̇O2peak was also not associated with sitting-induced reductions in Peak PBF (R=-0.145, P=0.444). The reductions in Peak PBF following sitting support previous work demonstrating that prolonged uninterrupted sitting negatively impacts lower-limb RVF. In contrast, prolonged sitting did not alter the PBFAUC response, suggesting that Peak PBF responses may provide a more sensitive index of sitting-induced declines in RVF. In young to middle-aged, healthy adults, aerobic fitness did not impact baseline or sitting-induced reductions in lower-limb RVF.