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 (V̇o_{2 max}) in obese adults. Eighteen participants [35.1 ± 8.1 (SD) yr; body mass index = 36.0 ± 5.0 kg/m²] were randomized to 8 wk (3 sessions/wk) of either HIIT [10 × 1 min, 90-95% maximum heart rate (HR_max), 1-min active recovery] or MICT (30 min, 70–75% HR_max). 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). V̇o_{2 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.

Diet and/or exercise are routinely advised as methods for weight loss in overweight/obese individuals, particularly those who are at high risk for cardiovascular disease and type 2 diabetes mellitus. However, physical activity and structured exercise programs rarely result in significant loss of body weight or body fat, and weight-loss diets have extraordinarily high recidivism rates. Despite only modest effects on body weight, exercise and ad libitum nutrient-dense diets for overweight/obese individuals have many health benefits, including skeletal muscle adaptations that improve fat and glucose metabolism, and insulin action; enhance endothelial function; have favorable changes in blood lipids, lipoproteins, and hemostatic factors; and reduce blood pressure, postprandial lipemia and glycemia, and proinflammatory markers. These lifestyle-induced adaptations occur independently of changes in body weight or body fat. Thus, overweight/obese men and women who are at increased risk for cardiovascular disease and type 2 diabetes as a result of sedentary lifestyle, poor diet, and excess body weight should be encouraged to engage in regular physical activity and improve their diet, regardless of whether the healthier lifestyle leads to weight loss.

CrossFit^® began as another exercise program to improve physical fitness and has rapidly grown into the “sport of fitness”. However, little is understood as to the physiological indicators that determine CrossFit^® sport performance. The purpose of this study was to determine which physiological performance measure was the greatest indicator of CrossFit^® workout performance. Male (n = 12) and female (n = 5) participants successfully completed a treadmill graded exercise test to measure maximal oxygen uptake (VO_2max), a 3-minute all-out running test (3MT) to determine critical speed (CS) and the finite capacity for running speeds above CS (D′), a Wingate anaerobic test (WAnT) to assess anaerobic peak and mean power, the CrossFit^® total to measure total body strength, as well as the CrossFit^® benchmark workouts: Fran, Grace, and Nancy. It was hypothesized that CS and total body strength would be the greatest indicators of CrossFit^® performance. Pearson’s r correlations were used to determine the relationship of benchmark performance data and the physiological performance measures. For each benchmark-dependent variable, a stepwise linear regression was created using significant correlative data. For the workout Fran, back squat strength explained 42% of the variance. VO_2max explained 68% of the variance for the workout Nancy. Lastly, anaerobic peak power explained 57% of the variance for performance on the CrossFit^® total. In conclusion, results demonstrated select physiological performance variables may be used to predict CrossFit^® workout performance.

We examined the effects of interrupting prolonged sitting with multiple 2-min walking breaks or one 30-min continuous walking session on glucose control and ambulatory blood pressure (ABP). Ten overweight/obese, physically inactive participants (5 men; 32±5 y, BMI 30.3±4.6 kg·m-2) participated in this randomized four-trial crossover study, with each trial performed on a separate, simulated workday lasting 9h: 1) 30 min of continuous walking at 71±4% HRmax (30min-MOD); 2) 21x2-min bouts of moderate-intensity walking at 53±5% HRmax (2min-MOD), each performed every 20 min (42 min total); 3) 8x2-min bouts of vigorous-intensity walking at 79±4% HRmax (2min-VIG), each performed every h (16 min total); 4) 9h of prolonged sitting (SIT). Participants underwent continuous interstitial glucose monitoring and ABP monitoring during and after the simulated workday spent in the laboratory, with primary data analysis from 12:30 h to 07:00 h the next morning. Compared with SIT (5.6±1.1 mmol·L-1), mean 18.7-h glucose was lower during the 2min-MOD (5.2±1.1 mmol·L-1) and 2min-VIG (5.4±0.9 mmol·L-1) trials and mean 18.7-h glucose during the 30min-MOD trial (5.1±0.8 mmol·L-1) was lower than all other trials (P<0.001). Postprandial glucose was ~7-13% lower during all trials compared to SIT (P<0.001), with 30min-MOD having the greatest effect. Only the 30min-MOD trial was effective in reducing systolic ABP from 12:30 – 07:00 h (119±15 mmHg) when compared to SIT (122±16 mmHg; P<0.05). Replacing sitting with 2 min of moderate-intensity walking every 20 min or 2 min of vigorous-intensity walking every h during a simulated workday reduced 18.7-h and postprandial glucose, but only 30 min of continuous moderate-intensity walking was effective for reducing both glucose and systolic ABP.

We determined the oxygen uptake (V[Combining Dot Above]O2), heart rate (HR), and blood lactate responses to 2 high-intensity interval exercise protocols differing in interval length. On separate days, 14 recreationally active males performed a 4 × 4 (four 4-minute intervals at 90-95% HRpeak, separated by 3-minute recovery at 50 W) and 16 × 1 (sixteen 1-minute intervals at 90-95% HRpeak, separated by 1-minute recovery at 50 W) protocol on a cycle ergometer. The 4 × 4 elicited a higher mean V[Combining Dot Above]O2 (2.44 ± 0.4 vs. 2.36 ± 0.4 L·min) and "peak" V[Combining Dot Above]O2 (90-99% vs. 76-85% V[Combining Dot Above]O2peak) and HR (95-98% HRpeak vs. 81-95% HRpeak) during the high-intensity intervals. Average power maintained was higher for the 16 × 1 (241 ± 45 vs. 204 ± 37 W), and recovery interval V[Combining Dot Above]O2 and HR were higher during the 16 × 1. No differences were observed for blood lactate concentrations at the midpoint (12.1 ± 2.2 vs. 10.8 ± 3.1 mmol·L) and end (10.6 ± 1.5 vs. 10.6 ± 2.4 mmol·L) of the protocols or ratings of perceived exertion (7.0 ± 1.6 vs. 7.0 ± 1.4) and Physical Activity Enjoyment Scale scores (91 ± 15 vs. 93 ± 12). Despite a 4-fold difference in interval duration that produced greater between-interval transitions in V[Combining Dot Above]O2 and HR and slightly higher mean V[Combining Dot Above]O2 during the 4 × 4, mean HR during each protocol was the same, and both protocols were rated similarly for perceived exertion and enjoyment. The major difference was that power output had to be reduced during the 4 × 4 protocol to maintain the desired HR.

Ight = 182.8 ± 6.9 cm, weight = 77.8 ± 12.1 kg) and four females (age = 29.0 ± 7.3 yr, height = 170.8 ± 3.2 cm, weight = 61.8 ± 8.2 kg) underwent an incremental V˙O2max test (IET) on a cycle ergometer, followed by four or five randomly assigned constant-power exercise bouts to exhaustion, on separate days. The CP for each subject was estimated using linear and nonlinear regression. Results IET V˙O2max averaged 3.55 ± 0.92 L·min−1 (RER = 1.21 ± 0.05, HR = 186 ± 10 bpm, 96.1% ± 6.3% of age-predicted maximum). Mean peak V˙O2 (range = 3.32 ± 0.88 to 3.54 ± 0.91 L·min−1) during the three highest constant-power bouts (two of which were 53 to 82 W less than peak power output attained during IET) was not significantly different from IET V˙O2max. Eleven of 13 subjects exceeded their IET V˙O2max during at least one of the constant-power exercise bouts. However, peak V˙O2 (3.11 ± 0.79 L·min−1) during the lowest constant-power exercise bout, which ranged from 10 to 36 W above CP estimated with a two-parameter nonlinear model, was significantly lower than IET V˙O2max (88.2% ± 9.4% of IET V˙O2max). Conclusions At power outputs above CP, V˙O2 does not necessarily increase to maximum during constant-power exercise to exhaustion. In addition, the highest V˙O2 values measured during a traditional V˙O2 “max” test (i.e., IET) may not reflect the highest attainable V˙O2 despite V˙O2max criteria being met....