Impact of aerobic fitness status, menstrual cycle phase, and oral contraceptive use on exercise substrate oxidation and metabolic flexibility in females.

The influence of menstrual cycle phase and fitness status on metabolism during high-intensity interval exercise (HIIE) was assessed. Twenty-five females (24.4 (3.6) years) were categorized by normal menstrual cycle (n = 14) vs. oral contraceptive (OC) use (n = 11) and by aerobic fitness, high-fitness females (HFF; n = 13) vs. low-fitness females (LFF; n = 12). HIIE was four sets of four repetitions with a 3 min rest between intervals on a cycle ergometer at a power output halfway between the ventilatory threshold and V̇O2peak and performed during follicular (FOL: days 2-7 or inactive pills) and luteal phases (LUT: day ∼21 or 3rd week of active pills). Substrate oxidation was assessed via indirect calorimetry, blood lactate via finger stick, and recovery of skeletal muscle oxidative metabolism (mV̇O2) via continuous-wave near-infrared spectroscopy. HFF oxidized more fat (g·kg-1) during the full session (FOL: p = 0.050, LUT: p = 0.001), high intervals (FOL: p = 0.048, LUT: p = 0.001), low intervals (FOL: p = 0.032, LUT: p = 0.024), and LUT recovery (p = 0.033). Carbohydrate oxidation area under the curve was greater in HFF during FOL (FOL: p = 0.049, LUT: p = 0.124). Blood lactate was lower in LFF in FOL (p ≤ 0.05) but not in LUT. Metabolic flexibility (Δ fat oxidation g·kg-1·min-1) was greater in HFF than LFF during intervals 2-3 in FOL and 1-4 in LUT (p ≤ 0.05). Fitness status more positively influences exercise metabolic flexibility during HIIE than cycle phase or OC use.

Training Status Impacts Metabolic Response to A High-Protein Weight Loss Diet in Recreationally Resistance-Trained Females.

This study investigated the effects of a novel high-protein diet template on postprandial metabolism and body composition (e.g., waist and hip circumference, body fat (%), fat mass, fat-free mass) in recreationally resistance-trained females. Fifteen females adhered to an eight-week high-protein dietary intervention (~1.5-1.6 g·kg-1·day-1) administered via template format. Pre- and post-intervention visits included anthropometrics, measurement of body composition, and an acute high-fat meal challenge. The high-fat meal challenge (61% fat) consisted of fasting postprandial blood glucose, resting metabolic rate (RMR), fat and carbohydrate oxidation assessed at 60-, 120-, and 180-minutes. Participants were split into high (HTF; 5-6 days·week-1 of resistance training; n = 8) and low-training frequency (LTF; 2-3 days·week-1 of resistance training; n = 7) groups. All metabolism data were assessed as absolute (kcal or g) and relative (kcal or g·kg·FFM-1·minutes-1) to fat-free mass. Post-intervention, there was a significant reduction in HTF waist circumference (p = 0.044), LTF body fat % (p = 0.012), and LTF fat mass (p = 0.014). Post-intervention, HTF females had significantly lower absolute RMR area under the curve (AUC) than LTF females (p = 0.036). LTF females had higher absolute fat oxidation AUC compared to HTF females' pre-intervention (p = 0.048) but a significant decrease in absolute (p = 0.050) and relative (p = 0.050) fat oxidation AUC post-intervention. LTF females had a significant increase in absolute (p = 0.032) and relative (p = 0.029) carbohydrate oxidation AUC pre- to post-intervention (p = 0.032). For blood glucose, no significant differences between groups were detected (p > 0.05). These findings suggest that a novel high-protein diet template elicits a metabolic shift favoring carbohydrate oxidation in females engaging in low-frequency resistance training but did not alter fat and carbohydrate metabolism in females engaging in HTF resistance training.

Comparison of aspartame- and sugar-sweetened soft drinks on postprandial metabolism.

Aim: We compared the impact of artificially- and sugar-sweetened beverages co-ingested with a mixed meal on postprandial fat and carbohydrate oxidation, blood glucose, and plasma insulin and triglyceride concentrations. Methods: Eight college-aged, healthy males completed three randomly assigned trials, which consisted of a mixed macronutrient meal test with 20oz of Diet-Coke (AS), Coca-Cola (NS), or water (CON). One week separated each trial and each participant served as his own control. Resting energy expenditure (REE) via indirect calorimetry, blood pressure, and blood samples were obtained immediately before, 5, 10, 30, 60, 120, and 180 min after meal and beverage ingestion. A two-way (treatment × time) repeated-measures ANOVA was conducted to assess REE, fat and carbohydrate oxidation rates, blood glucose, and plasma insulin and triglyceride concentrations. Results: There was a significant main effect of treatment on total fat oxidation (P = 0.006), fat oxidation was significantly higher after AS (P = 0.006) and CON (P = 0.001) compared to following NS. There was a significant main effect of treatment on total carbohydrate oxidation (P = 0.005), carbohydrate oxidation was significantly lower after AS (P = 0.014) and CON (P = 0.001) compared to following NS. Plasma insulin concentration AUC was significantly lower after AS (P = 0.019) and trended lower in CON (P = 0.054) compared to following NS. Conclusion: Ingestion of a mixed meal with an artificially-sweetened beverage does not impact postprandial metabolism, whereas a sugar-sweetened beverage suppresses fat oxidation and increases carbohydrate oxidation compared to artificially-sweetened beverage and water.

African American Females Are Less Metabolically Flexible Compared with Caucasian American Females following a Single High-Fat Meal: A Pilot Study.

The relationship between metabolic flexibility (MF) and components of metabolic disease has not been well-studied among African American (AA) females and may play a role in the higher incidence of chronic disease among them compared with Caucasian American (CA) females. This pilot study aimed to compare the metabolic response of AA and CA females after a high-fat meal. Eleven AA (25.6 (5.6) y, 27.2 (6.0) kg/m2, 27.5 (9.7) % body fat) and twelve CA (26.5 (1.5) y, 25.7 (5.3) kg/m2, 25.0 (7.4) % body fat) women free of cardiovascular and metabolic disease and underwent a high-fat meal challenge (55.9% fat). Lipid oxidation, insulin, glucose, and interleukin (IL)-8 were measured fasted, 2 and 4 h postprandial. AA females had a significantly lower increase in lipid oxidation from baseline to 2 h postprandial (p = 0.022), and trended lower at 4 h postprandial (p = 0.081) compared with CA females, indicating worse MF. No group differences in insulin, glucose or HOMA-IR were detected. IL-8 was significantly higher in AA females compared with CA females at 2 and 4 h postprandial (p = 0.016 and p = 0.015, respectively). These findings provide evidence of metabolic and inflammatory disparities among AA females compared with CA females that could serve as a predictor of chronic disease in individuals with a disproportionately higher risk of development.

Validity of the 6-Minute Walk Test and YMCA Submaximal Cycle Test During Midpregnancy.

ABSTRACT: Tinius, RA, Blankenship, M, Maples, JM, Pitts, BC, Furgal, K, Norris, ES, Hoover, DL, Olenick, A, Lambert, J, and Cade, WT. Validity of the 6-minute walk test and Young Men's Christian Association (YMCA) submaximal cycle test during midpregnancy. J Strength Cond Res 35(11): 3236-3242, 2021-Submaximal exercise testing can be a feasible alternative to maximal testing within special populations to safely predict fitness levels; however, submaximal exercise testing has not been well-validated for use during pregnancy. The purpose of this study was to determine the concurrent validity of the 6-minute walk test (6MWT) and the YMCA submaximal cycle test (YMCAT) to predict V̇o2max in physically active women during midpregnancy. Thirty-seven (n = 37) pregnant women (22.1 ± 1.4 weeks' gestation) and 10 (n = 10) nonpregnant women participated in the study. Subjects completed a graded maximal treadmill test at 1 visit to measure maximal oxygen consumption (V̇o2max), and then subjects completed the 6MWT and YMCAT in randomized order during a separate visit. The predicted V̇o2max from each submaximal test were compared with the measured V̇o2max from the treadmill test to assess the validity of these tests during pregnancy. Among pregnant women, predicted V̇o2max from the YMCAT was not correlated to the measured V̇o2max (r = 0.14, p = 0.42), and the predicted V̇o2max from the 6MWT was only moderately correlated (r = 0.40, p = 0.016) to the measured V̇o2max. Among nonpregnant women, the predicted V̇o2max values from both the YMCAT and the 6MWT had strong correlations with the measured V̇o2max values (YMCAT: r = 0.71, p = 0.02; 6MWT: r = 0.80, p = 0.006). Neither test demonstrated concurrent validity among the pregnant sample. The main finding is that the YMCAT is not a valid method to estimate V̇o2max during midpregnancy (likely due to physiological changes in heart rate [HR] during pregnancy). The 6MWT has potential to be used clinically for estimating fitness as actual and predicted values did positively correlate, and it is not dependent on HR responses to exercise. However, if a precise measure of fitness is needed, then neither test appears to have strong validity for use during midpregnancy.

High-fat meal increases peripheral blood mononuclear cell pro-inflammatory cytokine expression in African-American women.

African-American (AA) women have elevated predominance of inflammatory diseases concurrent with local inflammation resulting in compromised metabolic function. The purpose of the study was 2-fold: 1) to examine the gene and protein expression of pro- and anti-inflammatory cytokine secretion by peripheral blood mononuclear cells (PBMC) obtained from AA and Caucasian-American (CA) women in response to an acute high-fat meal; and 2) to explore the influence of race (AA vs. CA) on PBMC reactivity. Ten AA and 11 CA women consumed a high-fat meal with baseline and 4 h postprandial venous blood draws. PBMCs were incubated for 3 h then messenger RNA expression and supernatant protein concentration was used to examine inflammatory profiles. All women had a postprandial increase in interleukin (IL)-8 gene expression, IL-8 protein concentration, and tumor necrosis factor alpha (TNF-α) protein concentration (P < 0.05). AA women had a postprandial increase in IL-6, IL-8, and TNF-α protein concentration (P < 0.05). AA women had higher postprandial IL-1ß protein concentration and IL-8 gene expression compared with CA women (P < 0.05). Our data uncovers the specific impact of race and time on pro-inflammatory PBMC (IL-1ß, IL-6, IL-8, and TNF-α) expression profiles in response to an acute high-fat meal challenge. Novelty: African Americans have higher predominance of inflammatory disease. We explored the potential race impact on peripheral blood mononuclear cell reactivity in response to a meal. A pro-inflammatory response to an acute high-fat meal with race impact was observed possibly contributing to health disparities impacting African-American women.

Acute exercise effects on postprandial fat oxidation: meta-analysis and systematic review.

The purpose of this systematic review was to synthesize and evaluate current literature examining the effects of exercise on postprandial fat oxidation, as well as to provide future direction. A quantitative review was performed using meta-analytic methods. A moderator analysis was performed to investigate potential variables that could influence the effect of exercise on postprandial fat oxidation. Fifty-six effects from 26 studies were retrieved. There was a moderate effect of exercise on postprandial fat oxidation (Cohen's d = 0.58 (95% CI, 0.39 to 0.78)). Moderator analysis revealed that sex, age, weight status, training status, exercise type, exercise intensity, timing of exercise, and composition of the meal challenge significantly affected the impact of prior exercise on postprandial fat oxidation. The moderator analysis also indicated that most previous studies have investigated the impact of prior moderate-intensity endurance exercise on postprandial fat oxidation in young, healthy, lean men. Suggested priorities for future research in this area include (i) an examination of sex differences in and/or female-specific aspects of postprandial metabolism; (ii) a comprehensive evaluation of exercise modalities, intensities, and durations; and (iii) a wider variety of test meal compositions, especially those with higher fat content. Novelty A systematic review of the impact of exercise on postprandial fat oxidation was performed using meta-analytic methods. Analysis revealed a moderate effect of exercise on postprandial fat oxidation. The presented data support a need for future studies to investigate sex differences and to include comprehensive evaluations of exercise modalities, intensities, and duration.

Tabata-style functional exercise increases resting and postprandial fat oxidation but does not reduce triglyceride concentrations.

NEW FINDINGS: What is the central question of this study? What are the metabolic impacts of high intensity functional Tabata exercise? What is the main finding and its importance? Tabata exercise with high intensity functional movements causes increases in fasted and postprandial fat oxidation the day after exercise without altering postprandial triglyceride concentrations. These results support the usage of a Tabata-style high intensity functional exercise to improve postprandial fat oxidation. ABSTRACT: We evaluated the effect of a high fat meal with and without prior high intensity functional exercise executed in a Tabata-style interval pattern on resting and postprandial substrate oxidation, as well as postprandial blood glucose and triglyceride concentrations. Eleven healthy males completed two trials (Tabata exercise (TE) and non-exercise control (CON)) in random order separated by 7 days. A two-day protocol was used in which TE or CON was performed on the first day and a high fat meal was administered ∼13 h later the following morning. Power output from the TE session was quantified using a kinematic approach by calculating external work performed per unit time for each of the four exercises (rowing, dumbbell thrusters, kettlebell swings and burpees). For the meal challenge, respiratory gases and blood samples were taken fasted and at 1, 2 and 3 h postprandial. Fat oxidation was significantly higher after TE compared to CON at all time points (P < 0.05). Carbohydrate oxidation was significantly lower after TE compared to CON at 1 h postprandial (P < 0.05). There were no significant effects of TE on fasting or postprandial glucose or triglyceride concentrations. Functional exercises performed in a high intensity TE pattern enhance fasting and postprandial fat oxidation on the following day with minimal influence on blood triglycerides or glucose levels.

Assessment of endpoint criteria and perceived barriers during maximal cardiorespiratory fitness testing among pregnant women.

BACKGROUND: A plateau in volume of oxygen consumption (VO2) is the primary indicator for determining if an individual has reached their maximal aerobic capacity. However, secondary criteria can also be used to identify maximal effort (i.e. lactate level, rating of perceived exertion [RPE], percent of age-predicted maximal heart rate [HR] and respiratory exchange ratio [RER]). Age and gender-specific secondary criteria have been developed for the general population, but no secondary criteria have been established for pregnant women. The primary purpose of this study was to analyze secondary endpoint criteria during VO2max testing among pregnant women. A secondary purpose was to identify emotional and physical barriers pregnant women have that may prevent them from reaching maximal effort. METHODS: Twenty-five pregnant women (age= 30.0±3.6 years; gestation age= 22.1±1.4 weeks, pre-pregnancy BMI= 23.68±4.04 kg/m2) participated. Each participant completed a Bruce protocol treadmill test and maximal HR, RER, lactate, and RPE were assessed and compared to standards. Barriers were assessed immediately postexercise via open-ended questions. RESULTS: The mean VO2max was 32.9±8.8 mL/kg/min. Mean RPEmax was 17.6±1.8 versus the standard of RPE≥17 (P=0.12). Percent of age-predicted HRmax was 88.0±6.8% versus the standard of ≥95% (P<0.001). Immediate postexercise lactate was 6.8±2.4mM versus the standard of ≥8 mM (P=0.03). Maximal RER was 1.2±0.2 versus the standard of RERmax ≥1.1 (P=0.08). CONCLUSIONS: Our data provide preliminary evidence that secondary criteria may need to be adjusted for pregnant women. Additionally, physical and emotional barriers may be enhanced by pregnancy (e.g. pain, discomfort, anxiety, health concerns), and may limit the performance of pregnant women during maximal exercise.

Caffeine influences cadence at lower but not higher intensity RPE-regulated cycling.

Caffeine blunts RPE estimations but effects on selected cycling cadence are unclear. PURPOSE: This study examined influence of caffeine on cycling cadence with intensities prescribed at RPE 4 and 7 (OMNI Scale). METHODS: College-aged (20.5±2.0y) male and female volunteers (n=15) (VO2 peak=40.3±4.0,) completed a maximal cycling test followed by trials where they adjusted cadence (CAD) (clamped resistances) to produce overall feelings equivalent to RPE 4 (RPE4) and RPE 7 (RPE7) (10min each) following caffeine (CAF) (6mg·kg-1·min-1) and placebo (PLA) (counterbalanced) ingestion. Participants were blinded to cadence during production trials. RESULTS: Repeated measures ANOVA showed a significant main effect (trial) for CAD (CAF ~4rev·min-1 faster) for RPE4 but no significance for RPE7. Main effect for heart rate (HR) was not significant for RPE4 but significant for RPE7 (CAF ~4b·min-1 higher). Main effects showed mean VO2 significantly higher (~1.5-2ml·kg-1·min-1) for CAF for RPE4 and RPE7. Using a calculated least significant difference (5rev·min-1) positive responses were observed for five individuals (33%) for RPE4 and 3 individuals (20%) for RPE7. No negative (significantly slower cadences) responses were observed. RER in select trials suggested increased reliance on free fatty acid for CAF in responders. CONCLUSIONS: Mean results show a mild effect of CAF on cadence selection during RPE production. However, assessing individual results more effectively clarifies ergogenic responses. Future research should identify factors responsible for diverse responses to caffeine during exercise.

Caffeine effects on velocity selection and physiological responses during RPE production.

Caffeine (CAF) blunts estimated ratings of perceived exertion (RPE) but the effects on RPE production are unclear. This study examined effects of acute caffeine ingestion during treadmill exercise where participants exercised at prescribed RPE 4 and 7. Recreational runners (maximal oxygen consumption = 51.4 ± 9.8 mL·kg-1·min-1) (n = 16) completed a maximal treadmill test followed by trials where they selected treadmill velocity (VEL) (1% grade) to produce RPE 4 and RPE 7 (10 min each). RPE production trials followed CAF (6 mg·kg-1) or placebo (PLA) (counterbalanced) ingestion. Participants were blinded to treadmill VEL but the Omni RPE scale was in full view. Repeated-measures ANOVA showed a main effect (trial) for VEL (CAF ∼5 m·min-1 faster) for RPE 4 (p = 0.07) and RPE 7 (p = 0.03). Mean heart rate and oxygen consumption responses were consistently higher for CAF but failed to reach statistical significance. Individual responses to CAF were labeled positive using a criterion of 13.4 m·min-1 faster for CAF (vs. PLA). Ten of 32 trials (31%) were positive responses. In these, systematic increases were observed for heart rate (∼12 beats·min-1) and oxygen consumption (∼5.7 mL·kg-1·min-1). Blunted/stable respiratory exchange ratio values at higher VEL for positive responders suggest increased free fatty acid reliance during CAF. In conlusion, mean results show a mild effect of CAF during RPE production. However, individual responses more clearly indicate whether a true effect is possible. Trainers and individuals should consider individual responses to ensure effectively intensity regulation.