We hypothesized that high-intensity interval training (HIIT) would be more effective than moderate-intensity continuous training (MICT) at improving endothelial function and maximum oxygen uptake (V̇o2 max) in obese adults. Eighteen participants [35.1 ± 8.1 (SD) yr; body mass index = 36.0 ± 5.0 kg/m(2)] were randomized to 8 wk (3 sessions/wk) of either HIIT [10 × 1 min, 90-95% maximum heart rate (HRmax), 1-min active recovery] or MICT (30 min, 70-75% HRmax). Brachial artery flow-mediated dilation (FMD) increased after HIIT (5.13 ± 2.80% vs. 8.98 ± 2.86%, P = 0.02) but not after MICT (5.23 ± 2.82% vs. 3.05 ± 2.76%, P = 0.16). Resting artery diameter increased after MICT (3.68 ± 0.58 mm vs. 3.86 ± 0.58 mm, P = 0.02) but not after HIIT (4.04 ± 0.70 mm vs. 4.09 ± 0.70 mm; P = 0.63). There was a significant (P = 0.02) group × time interaction in low flow-mediated constriction (L-FMC) between MICT (0.63 ± 2.00% vs. -2.79 ± 3.20%; P = 0.03) and HIIT (-1.04 ± 4.09% vs. 1.74 ± 3.46%; P = 0.29). V̇o2 max increased (P < 0.01) similarly after HIIT (2.19 ± 0.65 l/min vs. 2.64 ± 0.88 l/min) and MICT (2.24 ± 0.48 l/min vs. 2.55 ± 0.61 l/min). Biomarkers of cardiovascular risk and endothelial function were unchanged. HIIT and MICT produced different vascular adaptations in obese adults, with HIIT improving FMD and MICT increasing resting artery diameter and enhancing L-FMC. HIIT required 27.5% less total exercise time and ∼25% less energy expenditure than MICT.

A constant-load exercise bout to exhaustion after a graded exercise test to verify maximal oxygen uptake (V[Combining Dot Above]O2max) during cycle ergometry has not been evaluated in sedentary adults with obesity. Nineteen sedentary men (n = 10) and women (n = 9) with obesity (age = 35.8 ± 8.6 years; body mass index [BMI] = 35.9 ± 5.1 kg·m; body fat percentage = 44.9 ± 7.2) performed a ramp-style maximal exercise test (ramp), followed by 5-10 minutes of active recovery, and then performed a constant-load exercise bout to exhaustion (verification test) on a cycle ergometer for determination of V[Combining Dot Above]O2max and maximal heart rate (HRmax). V[Combining Dot Above]O2max did not differ between tests (ramp: 2.29 ± 0.71 L·min, verification: 2.34 ± 0.67 L·min; p = 0.38). Maximal heart rate was higher on the verification test (177 ± 13 b·min vs. 174 ± 16 b·min; p = 0.03). Thirteen subjects achieved a V[Combining Dot Above]O2max during the verification test that was ≥2% (range: 2.0-21.0%; 0.04-0.47 L·min) higher than during the ramp test, and 8 subjects achieved a HRmax during the verification test that was 4-14 b·min higher than during the ramp test. Duration of verification or ramp tests did not affect V[Combining Dot Above]O2max results, but the difference in HRmax between the tests was inversely correlated with ramp test duration (r = -0.57, p = 0.01). For both V[Combining Dot Above]O2max and HRmax, differences between ramp and verification tests were not correlated with BMI or body fat percentage. A verification test may be useful for identifying the highest V[Combining Dot Above]O2max and HRmax during cycle ergometry in sedentary adults with obesity.