Dharini M. Bhammar

Physiological Responses to High-Intensity Interval Exercise Differing in Interval Duration.

Abstract Tucker, WJ, Sawyer, BJ, Jarrett, CL, Bhammar, DM, and Gaesser, GA. Physiological responses to high-intensity interval exercise differing in interval duration. J Strength Cond Res 29(12): 3326–3335, 2015—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−1) 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−1) and end (10.6 ± 1.5 vs. 10.6 ± 2.4 mmol·L−1) 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.

Effects of High-intensity Interval Training and Moderate-intensity Continuous Training on Endothelial Function and Cardiometabolic Risk Markers in Obese Adults

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.

Postexercise hypotension after continuous, aerobic interval, and sprint interval exercise

Abstract Angadi, SS, Bhammar, DM, and Gaesser, GA. Postexercise hypotension after continuous, aerobic interval, and sprint interval exercise. J Strength Cond Res 29(10): 2888–2893, 2015—We examined the effects of 3 exercise bouts, differing markedly in intensity, on postexercise hypotension (PEH). Eleven young adults (age: 24.6 ± 3.7 years) completed 4 randomly assigned experimental conditions: (a) control, (b) 30-minute steady-state exercise (SSE) at 75–80% maximum heart rate (HRmax), (4) aerobic interval exercise (AIE): four 4-minute bouts at 90–95% HRmax, separated by 3 minutes of active recovery, and (d) sprint interval exercise (SIE): six 30-second Wingate sprints, separated by 4 minutes of active recovery. Exercise was performed on a cycle ergometer. Blood pressure (BP) was measured before exercise and every 15-minute postexercise for 3 hours. Linear mixed models were used to compare BP between trials. During the 3-hour postexercise, systolic BP (SBP) was lower (p < 0.001) after AIE (118 ± 10 mm Hg), SSE (121 ± 10 mm Hg), and SIE (121 ± 11 mm Hg) compared with control (124 ± 8 mm Hg). Diastolic BP (DBP) was also lower (p < 0.001) after AIE (66 ± 7 mm Hg), SSE (69 ± 6 mm Hg), and SIE (68 ± 8 mm Hg) compared with control (71 ± 7 mm Hg). Only AIE resulted in sustained (>2 hours) PEH, with SBP (120 ± 9 mm Hg) and DBP (68 ± 7 mm Hg) during the third-hour postexercise being lower (p ⩽ 0.05) than control (124 ± 8 and 70 ± 7 mm Hg). Although all exercise bouts produced similar reductions in BP at 1-hour postexercise, the duration of PEH was greatest after AIE.

Effects of Fractionized and Continuous Exercise on 24-h Ambulatory Blood Pressure

PURPOSE The objective of this study is to compare the effects of fractionized aerobic exercise (three 10-min exercise sessions) and continuous exercise (one 30-min exercise session) on 24-h ambulatory blood pressure (ABP). METHODS Eleven healthy prehypertensive subjects (28.3 ± 8.0 (SD) yr) completed three randomly assigned conditions: 1) three 10-min sessions of aerobic exercise (3 × 10 min), 2) one continuous 30-min session of aerobic exercise (1 × 30 min), and 3) a nonexercise control trial (control). The mode of exercise was walking on a motor-driven treadmill at 75%-79% of maximum heart rate (HRmax) (60%-65% V˙O2peak). Twenty-four-hour ABP was monitored with an automated ABP device (Oscar 2™; SunTech Medical, Morrisville, NC). Linear mixed models were used to compare 24-h ABP responses between trials. RESULTS The mean ± SD 24-h systolic blood pressure (SBP) was significantly lower during the 3 × 10-min trial (127 ± 15 mm Hg) compared with control (130 ± 15 mm Hg) (P < 0.001). Although both 3 × 10-min and 1 × 30-min trials reduced SBP compared with control during daytime/evening (1300-2300 h), only the 3 × 10-min trial reduced SBP during nighttime (2300-0800 h, 118 ± 16 vs 122 ± 14 mm Hg, P = 0.024) and the following morning (0800-1200 h, 127 ± 15 vs 131 ± 15 mm Hg, P = 0.016). For 24 h, 26.7% of SBP values during 3 × 10 min were normal (i.e., <120 mm Hg) compared with 18.3% for 1 × 30 min and 19.4% for control (P < 0.001). CONCLUSIONS In prehypertensive individuals, fractionized exercise (e.g., three 10-min aerobic exercise sessions spread and effective exercise alternative to continuous exercise for cardiovascular risk reduction in this population.

Walking Workstation Use Reduces Ambulatory Blood Pressure in Adults with Prehypertension

BACKGROUND The acute effect of low-intensity walking on blood pressure (BP) is unclear. PURPOSE To determine if the acute use of a walking workstation reduces ambulatory blood pressure (ABP) in prehypertensive men and women. METHODS Ten prehypertensive adults participated in a randomized, cross-over study that included a control workday and a walking workstation workday. ABP was measured for 7 hour during the workday and for 6 hour after work. RESULTS Both systolic BP (SBP) (134 ± 14 vs. 137 ± 16 mmHg; P = .027) and diastolic BP (DBP) (79 ± 10 vs. 82 ± 12 mmHg; P = .001) were lower on the walking workstation day. Postwork hours (4:00 PM-10:00 PM), SBP (129 ± 13 vs. 133 ± 14 mmHg; P = .008), and DBP (74 ± 11 vs. 78 ± 13 mmHg; P = .001) were also lower on the walking workstation day. DBP load was significantly lower during the walking workstation day, with only 14% of the readings above 90 mmHg compared with 22% of the control day readings (P = .037). CONCLUSION Accumulation of very-light-intensity physical activity (~2 METs) over the course of a single work day using a walking workstation may reduce BP burden in prehypertensive individuals.

Using a Verification Test for Determination of V[Combining Dot Above]O2max in Sedentary Adults With Obesity.

Abstract Sawyer, BJ, Tucker, WJ, Bhammar, DM, and Gaesser, GA. Using a verification test for determination of V[Combining Dot Above]O2max in sedentary adults with obesity. J Strength Cond Res 29(12): 3432–3438, 2015—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−2; 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−1, verification: 2.34 ± 0.67 L·min−1; p = 0.38). Maximal heart rate was higher on the verification test (177 ± 13 b·min−1 vs. 174 ± 16 b·min−1; 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−1) higher than during the ramp test, and 8 subjects achieved a HRmax during the verification test that was 4–14 b·min−1 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.

Validity of SenseWear® Armband v5.2 and v2.2 for estimating energy expenditure

ABSTRACT We compared SenseWear Armband versions (v) 2.2 and 5.2 for estimating energy expenditure in healthy adults. Thirty-four adults (26 women), 30.1 ± 8.7 years old, performed two trials that included light-, moderate- and vigorous-intensity activities: (1) structured routine: seven activities performed for 8-min each, with 4-min of rest between activities; (2) semi-structured routine: 12 activities performed for 5-min each, with no rest between activities. Energy expenditure was measured by indirect calorimetry and predicted using SenseWear v2.2 and v5.2. Compared to indirect calorimetry (297.8 ± 54.2 kcal), the total energy expenditure was overestimated (P < 0.05) by both SenseWear v2.2 (355.6 ± 64.3 kcal) and v5.2 (342.6 ± 63.8 kcal) during the structured routine. During the semi-structured routine, the total energy expenditure for SenseWear v5.2 (275.2 ± 63.0 kcal) was not different than indirect calorimetry (262.8 ± 52.9 kcal), and both were lower (P < 0.05) than v2.2 (312.2 ± 74.5 kcal). The average mean absolute per cent error was lower for the SenseWear v5.2 than for v2.2 (P < 0.001). SenseWear v5.2 improved energy expenditure estimation for some activities (sweeping, loading/unloading boxes, walking), but produced larger errors for others (cycling, rowing). Although both algorithms overestimated energy expenditure as well as time spent in moderate-intensity physical activity (P < 0.05), v5.2 offered better estimates than v2.2.

Effect of weight loss on operational lung volumes and oxygen cost of breathing in obese women

Background:The effects of moderate weight loss on operational lung volumes during exercise and the oxygen (O2) cost of breathing are unknown in obese women but could have important implications regarding exercise endurance.Methods:In 29 obese women (33±8 years, 97±14 kg, body mass index: 36±4 kg m−2, body fat: 45.6±4.5%; means±s.d.), body composition, fat distribution (by magnetic resonance imaging), pulmonary function, operational lung volumes during exercise and the O2 cost of breathing during eucapnic voluntary hyperpnea (([Vdot ]O2) vs ([Vdot ]E) slope) were studied before and after a 12-week diet and resistance exercise weight loss program.Results:Participants lost 7.5±3.1 kg or ≈8% of body weight (P<0.001), but fat distribution remained unchanged. After weight loss, lung volume subdivisions at rest were increased (P<0.05) and were moderately associated (P<0.05) with changes in weight. End-expiratory lung volume (percentage of total lung capacity) increased at rest and during constant load exercise (P<0.05). O2 cost of breathing was reduced by 16% (2.52±1.02–2.11±0.72 ml l−1; P=0.003). As a result, O2 uptake of the respiratory muscles ([Vdot ]O2Resp), estimated as the product of O2 cost of breathing and exercise ([Vdot ]E) during cycling at 60 W, was significantly reduced by 27±31 ml (P<0.001), accounting for 46% of the reduction in total body ([Vdot ]O2) during cycling at 60 W.Conclusions:Moderate weight loss yields important improvements in respiratory function at rest and during submaximal exercise in otherwise healthy obese women. These changes in breathing load could have positive effects on the exercise endurance and adherence to physical activity.

Predictors of fat mass changes in response to aerobic exercise training in women

Abstract Sawyer, BJ, Bhammar, DM, Angadi, SS, Ryan, DM, Ryder, JR, Sussman, EJ, Bertmann, FMW, and Gaesser, GA. Predictors of fat mass changes in response to aerobic exercise training in women. J Strength Cond Res 29(2): 297–304, 2015—Aerobic exercise training in women typically results in minimal fat loss, with considerable individual variability. We hypothesized that women with higher baseline body fat would lose more body fat in response to exercise training and that early fat loss would predict final fat loss. Eighty-one sedentary premenopausal women (age: 30.7 ± 7.8 years; height: 164.5 ± 7.4 cm; weight: 68.2 ± 16.4 kg; fat percent: 38.1 ± 8.8) underwent dual-energy x-ray absorptiometry before and after 12 weeks of supervised treadmill walking 3 days per week for 30 minutes at 70% of . Overall, women did not lose body weight or fat mass. However, considerable individual variability was observed for changes in body weight (−11.7 to +4.8 kg) and fat mass (−11.8 to +3.7 kg). Fifty-five women were classified as compensators and, as a group, gained fat mass (25.6 ± 11.1 kg to 26.1 ± 11.3 kg; p < 0.001). The strongest correlates of change in body fat at 12 weeks were change in body weight (r = 0.52) and fat mass (r = 0.48) at 4 weeks. Stepwise regression analysis that included change in body weight and body fat at 4 weeks and submaximal exercise energy expenditure yielded a prediction model that explained 37% of the variance in fat mass change (R 2 = 0.37, p < 0.001). Change in body weight and fat mass at 4 weeks were moderate predictors of fat loss and may potentially be useful for identification of individuals who achieve less than expected weight loss or experience unintended fat gain in response to exercise training.

Verification of Maximal Oxygen Uptake in Obese and Nonobese Children

Purpose The purpose of this study was to examine whether a supramaximal constant-load verification test at 105% of the highest work rate would yield a higher V˙O2max when compared with an incremental test in 10- to 12-yr-old nonobese and obese children. Methods Nine nonobese (body mass index percentile = 57.5 ± 23.2) and nine obese (body mass index percentile = 97.9 ± 1.4) children completed a two-test protocol that included an incremental test followed 15 min later by a supramaximal constant-load verification test. Results The V˙O2max achieved in verification testing (nonobese = 1.71 ± 0.31 L·min−1 and obese = 1.94 ± 0.47 L·min−1) was significantly higher than that achieved during the incremental test (nonobese = 1.57 ± 0.27 L·min−1 and obese = 1.84 ± 0.48 L·min−1; P < 0.001). There was no significant group (i.e., nonobese vs obese)–test (i.e., incremental vs verification) interaction, suggesting that there was no effect of obesity on the difference between verification and incremental V˙O2max (P = 0.747). Conclusion A verification test yielded significantly higher values of V˙O2max when compared with the incremental test in obese children. Similar results were observed in nonobese children. Supramaximal constant-load verification is a time-efficient and well-tolerated method for identifying the highest V˙O2 in nonobese and obese children.