Joan's running economy, measured while running at 10 km/h, is determined to be 183.72 mL/kg/km after calculating the oxygen cost for her body weight and the speed at which she ran.
To calculate Joan's running economy, we can use the given VO₂ (volume of oxygen consumed) and her body weight. Running economy is typically expressed as the volume of oxygen consumed per kilometer and per kilogram of body weight (mL/kg/km). Since Joan's VO₂ is 1.99 L/min and she runs at 10 km/h, we first convert her VO₂ to mL/min (1.99 L/min * 1000 mL/L = 1990 mL/min). Next, we calculate the oxygen cost per kilogram of body weight by dividing by her weight (1990 mL/min / 65 kg = 30.62 mL/kg/min).
Since she runs 10 kilometers in one hour, we then convert this to per kilometer (30.62 mL/kg/min * 60 min/h / 10 km/h = 183.72 mL/kg/km). Thus, her running economy is 183.72 mL/kg/km.
Joan's running economy, calculated during a treadmill graded exercise test at 10 km/h, is 183.72 mL/kg/km.