The relationship between heart rate variability and glucose clearance in healthy men and women.

Heart rate variability (HRV) is a non-invasive indicator of the activity of the autonomic nervous system, which regulates many physiological functions including metabolism. The purpose of this study was to quantify the relationship between resting markers of HRV and oral glucose tolerance test (OGTT) response. Eighteen healthy individuals (10 males, 8 females, (23.8±2.9 years) underwent a 10-minute resting HRV recording. The final five minutes were evaluated via Kubios HRV Standard for: root mean square of successive differences (RMSSD), standard deviation of normal-to-normal sinus beats (SDNN), high frequency (HF), and low frequency (LF). A standard 2-hour OGTT was then administered. Glucose was measured via finger stick before, 30-minutes post, 1-hour post, and 2-hours post OGTT. Pearson correlations demonstrated that RMSSD, SDNN, HF and LF were strongly correlated to fasting blood glucose (FBG) for the group (p<0.05) but not for glucose area under the curve (AUC). When analyzed by sex, only males demonstrated significant correlations between AUC and RMSSD, SDNN, and LF (p<0.05). An independent samples t-test revealed no sex differences for FBG, AUC, RMSSD, SDNN, HF and LF. These findings provide new and interesting insights into the relationship of autonomic activity and glucose uptake, highlighting sex-based relationships.

Physical Fitness Responses after Sixteen Weeks of Three Fitness Program Trainings in Untrained Subjects.

The remarkable popularity of fitness trends like high intensity functional training (HIFT), choreographed high intensity classes (CHIC) and resistance (RT) trainings raises the question on their effect on cardio-respiratory, lactate removal rate, endurance and body composition responses. The purpose of this study was to assess and compare these effects. Ninety-five participants were randomly assigned into 16 weeks of these trainings, five sessions/week. Anthropometric and fitness tests were carried out before training (PRE), after eight (8W) and sixteen weeks (16W). Body composition measures demonstrated significant decrease in body fat percentage (p<0.001, d=0.17-0.54) for all groups and fat mass (p< 0.001, d= 0.26-0.53) for HIFT and CHIC in 8W,16W and in 16W for RT (p= 0.03, d= 0.14), also significant increase in fat free mass only in HIFT (p< 0.002, d= 0.06-0.21) and RT (p< 0.001, d= 0.17-0.33) in 8W,16W. Cardio-respiratory measures demonstrated significant improvements in maximal aerobic capacity for HIFT (p< 0.001, d= 0.58-1.26) and CHIC (p< 0.001, d= 0.45-1.21) in 8W,16W. Endurance tests demonstrated significant improvements in 8W,16W in aerobic endurance among HIFT (p< 0.001, d= 1.28-3.19) and CHIC (p< 0.001, d= 1.16-1.79), in muscle absolute endurance in three groups (p< 0.002, d= 0.14-1.17)and muscle relative endurance in HIFT (p< 0.02, d= 0.13-0.2)and RT (p= 0.03, d= 0.3) in 16W. We can conclude that HIFT and CHIC are effective for cardio-respiratory and endurance improvement and all three programs are effective in reducing body fat.

The influence of sex-division, experience, and pacing strategy on performance in the 2020 CrossFit® Open.

To observe workout pacing strategies and determine which best predicted performance, this retrospective study analyzed recorded efforts from a random selection of 160 high-ranking (top 10,000) men and women (n = 80 each) in the 2020 CrossFit® Open (CFO). Video recordings submitted to the official competition leaderboard for all five tests were analyzed to quantify overall test completion rates (and tie-break time for test 5 only) and within-test repetition completion rate (repetitions × sec-1) for each exercise, as well as the quantity of failed repetitions, break strategy (count and duration), and transition times. Each variable was aggregated into first-half, last-half, and total-test averages, slopes, and coefficient of variation; except on test 5 (total-test only). Spearman's rank correlation coefficients were calculated between test completion rates, each test's respective pacing variables, competitor demographics (height and body mass) and CFO experience (i.e., past participation, consecutive competitions, and ranks). Stepwise regression using significantly (p < 0.05) correlated variables produced two prediction models for test performance (best predictor only and best overall model within 8 variables) in a validation group (50% of valid efforts) and then cross-validated against remaining athletes. When no between-group differences were seen, data were combined and used to create the final prediction models for test 1 (r2adj = 0.64-0.96, SEE = 0.4-1.2 repetitions × sec-1), test 2 (r2adj = 0.28-0.85, SEE = 2.0-4.5 repetitions × sec-1), test 3 (r2adj = 0.49-0.81, SEE = 1.1-1.7 repetitions × sec-1), test 4 (r2adj = 0.63-0.78, SEE = 0.6-0.9 repetitions × sec-1), and test 5 (rate: r2adj = 0.71-0.84, SEE = 1.2-1.6 repetitions × sec-1; tie-break time: r2adj = 0.06-0.62, SEE = 1.4-2.3 min). Across the five 2020 CFO tests, the data suggested that repetition pace, breaking strategy, and/or consistency in completing calisthenic-gymnastics components (when prescribed) was most predictive of performance. However, their influence was affected by the complexity of prescribed resistance training exercises and their relative loads. Athletes should prioritize calisthenic-gymnastics components but divert attention to more complex resistance training exercises when prescribed at higher relative intensity loads. Neither previous competition experience nor sex-division altered the hierarchal importance of these considerations.

Pacing Strategies Differ by Sex and Rank in 2020 CrossFit® Open Tests.

This retrospective study collected video recordings of a random selection of eighty men and women (n = 160) completing all five tests of the 2020 CrossFit® Open. All competitors were ranked within the top 10,000 overall but were sub-divided based on whether they ranked within the top 10% of their respective divisions. To examine the effect of sex and rank on pacing strategy, video analysis quantified the overall repetition completion rate on each test, as well as per minute (or round) repetition completion rates for each test's individual exercises, quantity of failed repetitions, break times, and transition times. All per minute (or round) data were aggregated into first- and last-half or total test average, slopes, and coefficient of variation. Sex and rank analyses of variance were performed on averages, slopes, and coefficients of variation for each variable calculated over the first and last halves of each test, except test 5 (total only). The top 10% of men were 17.5% faster (p < 0.001) than everyone else in tests 1, 3, and 5. The top 10% of women and remaining men were ~9.5% faster than remaining women in tests 1 and 3. In test 5, the remaining men were faster than top 10% of women (~11.2%, p < 0.001), and both were faster than the remaining women. In tests 2 and 4, the top 10% of athletes were 9.7% faster (p < 0.001) than remaining athletes, and at the same time, men were 7.7% faster (p < 0.001) than women. Analysis of each test's components revealed the top 10% of competitors to be faster and more consistent in most areas, while men were generally faster than women in gymnastics components and more consistent with their pace for resistance training exercises. These data provide insight into the differential factors linked to success in the men's and women's CFO divisions.

A Comparison of Anaerobic Power Tests using Cycle Ergometry and Nonmotorized Treadmill Ergometry at Optimized Loads.

The purpose of this study was to compare performance markers derived from a 30-second maximal bout on a cycle ergometer (CE) and non-motorized treadmill (NMT) under optimized loads. Recreationally active participants (n = 40) volunteered for the study. Force-velocity tests on the CE and NMT were used to determine optimal resistance for peak power (PP) production. The remaining visits were randomized and counterbalanced, with a single 30-second maximal test on CE or NMT to assess PP, mean power (MP), fatigue index (FI), over the course of the 30-second test, and maximum heart rate (HRmax) and blood lactate (BLa-) taken 1-minute post. Results were that PP and MP were higher (P<0.05) on CE compared to NMT for both sexes. FI did not differ among males (P=0.201) whereas females showed higher FI (P=0.002) on the CE. HRmax and BLa- were higher (P<0.05) after NMT for both sexes. There was no difference for optimal braking force on NMT between males (16.65±4.49%BW) and females (14.30±3.10%BW) (P=0.061). CE optimal torque factor was higher for males (0.78±0.16 Nm/kg) compared to females (0.62±0.14 Nm/kg) (P=0.001). Overall, CE produced higher power output using optimized loads in recreationally active males and females, while NMT test resulted in a higher HRmax and BLa- concentration. These tests for anaerobic power, when performed with optimized loads, produced different results for several variables, therefore these modalities should not be considered interchangeable. Practitioners should consider which modality best mimics the activities of the person being tested when selecting a protocol.

Carbohydrate Rinse Fails to Enhance Cycling Performance or Alter Metabolic and Autonomic Recovery in Recreational Cyclists.

The purpose of the study was to examine the effects of carbohydrate (CHO) mouth rinsing on autonomic and metabolic recovery as well as cycling performance. Ten male recreational cyclists (age = 30 ± 6 years, VO2peak = 54.5 ± 8.1 mL·kg-1·min-1) completed a randomized, double-blind, placebo-controlled, crossover designed study. A CHO or a placebo (PLA) rinse was administered every 12.5% of a work to completion trial (75%Wmax). Heart rate variability (lnRMSSD), the respiratory exchange ratio, and plasma epinephrine, norepinephrine, insulin, glucose, free fatty acids (FFA), and lactate were measured pre- and post-exercise. The CHO rinse did not improve time to completion of the test trial (CHO: 4108 ± 307 s, PLA: 4176 ± 374 s, p = 0.545). Further, the CHO rinse did not impact autonomic recovery, as measured by lnRMSSD (p = 0.787) and epinephrine (p = 0.132). Metabolic biomarkers were also unaffected by the CHO rinse, with no differences observed in responses of FFA (p = 0.064), lactate (p = 0.302), glucose (p = 0.113) or insulin (p = 0.408). Therefore, the CHO mouth rinse does not reduce the acute sympathetic response following strenuous exercise and does not result in improvements in cycling time to completion.

Effect of three fitness programs on strength, speed, flexibility and muscle power on sedentary subjects.

BACKGROUND: The aim of this study was to research and compare the effect of Crossfit® (CF), LesMills® (LM) and traditional resistance (TRAD) training program on short performances. METHODS: Participants were assigned randomly into three groups and followed the training sessions allocated at the rate of five sessions/week for 16 weeks. A battery of tests including anthropometric and performance measures were carried out over three sessions: before training (T0), after eight weeks (T1) and sixteen weeks of training (T2). RESULTS: Findings indicated that strength tests demonstrated a significant time effect (P<0.001, ηp2=0.6), the results showed that CF and TRAD groups improved strength every 8 weeks while LM group only at T2, The speed test demonstrated also a significant time effect (P<0.001, ηp2=0.5) the results showed an improvement in speed every 8 weeks for LM, at T2 for CF and no change for TRAD, for flexibility, all tests demonstrated a main time effect (P<0.001, ηp2. 0.46-0.7) CF was the best in shoulder range of motion and LM in trunk and lower limb flexibility, all power tests also demonstrated a significant time effect (P<0.001, ηp2: 0.76-0.9) the improvement for all groups was every 8 weeks. CONCLUSIONS: Based on these findings, we recommend TRAD and CF as valuable trainings for strength development, LM for flexibility and all three trainings for power improvement.

Steps expressed relative to body fat mass predicts body composition and cardiometabolic risk in adults eating ad libitum.

BACKGROUND: Excess body fatness is a consequence of a chronic energy surplus (energy intake is greater than energy expenditure). Given the serious health consequences of excess body fatness, factors that influence energy balance and body composition are increasingly important to understand. METHODS: A total of 34 adults between the ages of 19-40 years made a laboratory visit in which height, weight, body composition, and cardiometabolic risk (CMR) factors were quantified. Participants wore accelerometers for 21-28 days, then returned to the laboratory for a second body composition assessment. Changes in weight and body composition were used to quantify energy balance, and data derived from accelerometers provided markers of physical activity (PA) and sedentariness. RESULTS: Of the markers of PA that we measured, daily step counts expressed relative to fat mass was most strongly and consistently associated with body fatness and CMR status. CONCLUSIONS: Step counts expressed relative to fat mass were strongly associated with body composition and CMR in adults eating ad libitum. Longitudinal interventional studies are necessary to determine the efficacy of step count prescriptions expressed relative to existing and target body fatness and CMR levels for improving weight management and metabolic outcomes.

Workout Pacing Predictors of Crossfit® Open Performance: A Pilot Study.

To observe workout repetition and rest interval pacing strategies and determine which best predicted performance during the 2016 CrossFit® Open, five male (34.4 ± 3.8 years, 176 ± 5 cm, 80.3 ± 9.7 kg) and six female (35.2 ± 6.3 years, 158 ± 7 cm, 75.9 ± 19.3 kg) recreational competitors were recruited for this observational, pilot study. Exercise, round, and rest time were quantified via a stopwatch for all competitors on their first attempt of each of the five workouts. Subsequently, pacing was calculated as a repetition rate (repetitions·s-1) to determine the fastest, slowest, and average rate for each exercise, round, and rest interval, as well as how these changed (i.e., slope, Δ rate / round) across each workout. Spearman's rank correlation coefficients indicated that several pacing variables were significantly (p < 0.05) related to performance on each workout. However, stepwise regression analysis indicated that the average round rate best predicted (p < 0.001) performance on the first (R2 = 0.89), second (R2 = 0.99), and fifth (R2 = 0.94) workouts, while the competitors' rate on their slowest round best predicted workout three performance (R2 = 0.94, p < 0.001). The wall ball completion rate (R2 = 0.89, p = 0.002) was the best predictor of workout four performance, which was improved by 9.8% with the inclusion of the deadlift completion rate. These data suggest that when CrossFit® Open workouts consist of multiple rounds, competitors should employ a fast and sustainable pace to improve performance. Otherwise, focusing on one or two key exercises may be the best approach.

Acute Effect of Popular High-Intensity Functional Training Exercise on Physiologic Markers of Growth.

ABSTRACT: Kliszczewicz, B, Markert, CD, Bechke, E, Williamson, C, Clemons, KN, Snarr, RL, and McKenzie, MJ. Acute effect of popular high-intensity functional training exercise on physiologic markers of growth. J Strength Cond Res 35(6): 1677-1684, 2021-Constantly evolving, high-intensity functional training (HIFT) exercise consists of various modalities, orders, weights, and repetition schemes. High-intensity functional training has gained popularity among the general population, but lacks empirical evidence regarding acute adaptive responses. The purpose of this study was to describe the acute effects of 2 representative bouts of HIFT on physiologic markers of growth. For convenience, the bouts are designated "short" (<5 minutes) and "long" (∼15 minutes), although duration was not the only difference between bouts. Ten apparently healthy men (28.1 ± 5 years) performed 2 HIFT bouts in a randomized crossover design. Blood was collected at 5 time points (Pre, Post, 1, 3, and 6 hours) to examine growth hormone (GH), insulin-like growth factor (IGF-1), insulin-like growth factor binding proteins 1 and 2 (IGFBP-1 and IGFBP-2), and vascular endothelial growth factor (VEGF). Blood lactate concentration ([La]) was analyzed at the Pre and Post time points. A repeated-measures analysis of variance (ANOVA) revealed no trial differences among the markers (IGF-1, IGFBP-1, IGFBP-2, and VEGF) except GH at Post, where the long bout produced a greater effect (p = 0.005). Mean GH levels (pg·ml-1) in the short bout increased from 68.4 to 106.5, and in the long bout, mean GH levels increased from 38.5 to 286.4. The repeated-measures ANOVA revealed a main time effect in GH (p = 0.037), while a post hoc t-test demonstrated elevated GH at 1 hour (p = 0.018) when compared with Pre. No time-dependent change (p > 0.05) was observed in IGF-1, IGFBP-1, IGFBP-2, or VEGF. Mean blood [lactate] increased more than tenfold in both bouts. The findings of this descriptive study suggest that, other than GH, there are no acute differences in markers of skeletal muscle or vascular growth between these 2 specific HIFT bouts.

The Effects of Caffeine and Citrus Aurantium on Performance During Repeated Maximal Anaerobic Exercise Bouts in Habitual Caffeine Users.

ABSTRACT: McLester, CN, Bailey, P, Bechke, EE, Williamson, CM, McLester, JR, and Kliszczewicz, B. The effects of caffeine and Citrus aurantium on performance during repeated maximal anaerobic exercise bouts in habitual caffeine users. J Strength Cond Res 35(12): 3394-3399, 2021-The combination of caffeine (CAF) and Citrus aurantium (CA) have demonstrated the potential to improve various types of performance. To date, few studies have explored this relationship in purely anaerobic-based exercise. Therefore, the purpose of this study was to examine the influence of an acute dose of CAF + CA on peak anaerobic performance and the attenuation of power over multiple anaerobic bouts and to determine any differences in perceived effort or fatigue. Ten active men (25.1 ± 3.9 years) who habitually consumed caffeine volunteered to perform repeated anaerobic bouts on a cycle ergometer on 2 separate days, consuming either a placebo or 100 mg CAF + 100 mg CA. Significance was set at p ≤ 0.05 and repeated measures analysis of variance showed no main effects for peak power p = 0.520, mean power p = 0.926, minimum power p = 0.321, total work p = 0.924, time to peak power p = 0.536, or rate of fatigue p = 0.284. There was a time effect for all variables (p ≤ 0.05) with the exception of time to peak power (p = 0.181). There were no differences in any measures of perceived effort or fatigue between conditions (p ≥ 0.05), but there were time-dependent differences observed each day (p ≤ 0.05). Overall, an acute dosage of 100 mg CAF and 100 mg CA did not elicit any differences in anaerobic performance or in perceived measures of effort and fatigue in young males who habitually consume caffeine. Therefore, caution should be used when pairing CAF and CA for the goal of improving anaerobic performance, because no clear benefit was realized in this population at this dosage.

An examination of single day vs. multi-day heart rate variability and its relationship to heart rate recovery following maximal aerobic exercise in females.

The purpose of this study was to examine the relationship of a single day measure of heart rate variability (HRV), and the averaged baseline measures of HRV to heart rate recovery (HRR) following maximal exercise. Thirty females (22.9 ± 3.2 years, 64.8 ± 8.4 kg) completed four visits (V1-V4), where a 10-min HRV was recorded. Upon completing the V4 recording, a treadmill graded exercise test (GXT) was performed, followed by a 5-min active cool down. HRV was assessed through time domain measures [natural log of root mean square of successive R-R differences (lnRMSSD) and standard deviation of normal to normal intervals (lnSDNN)] and natural log frequency domain measures [low frequency (lnLF) and high frequency (lnHF)]. Variables collected over V1-V4 were measured as; day of (DO) GXT, 3 day (AV3), and 4 day average (AV4). HRR was calculated as the maximal HR achieved minus the HR at: 30-s (HRR30), 1-min (HRR1), 2-min (HRR2), 3-min (HRR3), 4-min (HRR4) or 5-min (HRR5) of recovery. Pearson's Product correlations revealed significant correlations (P = < 0.05) between all HRVDO measures to each HRR measure and are presented in ranges: lnSDNN (r = 0.442-0.522), lnRMSSD (r = 0.458-0.514), lnLF (r = 0.368-0.469), lnHF (r = 0.422-0.493). For HRVAV3, lnRMSSDAV3 and HRR1 were positively correlated (r = 0.390, P = 0.033). Last, HRVAV4 showed positive relationships (P = < 0.05) between lnRMSSDAV4 and HRR30 (r = 0.365, P = 0.048); and for HRR1 and lnSDNNAV4 (r = 0.400, P = 0.029), lnRMSSDAV4 (r = 0.442, P = 0.014), and lnHFAV4 (r = 0.368, P = 0.045); and lnRMSSDAV4 and HRR3 (r = 0.381, P = 0.038). Within the current study HRVDO displayed the strongest correlations to HRR therefore, averaged resting HRV measures do not strengthen the prediction of cardiovascular recovery following a GXT in this population.

Relative accuracy of anthropometric-based body fat equations in males and females with varying BMI classifications.

BACKGROUND: BMI based body fat equations developed from Womersley and Durnin (BMIWO), Jackson et al. (BMIJA), Deurenberg et al. (BMIDE), and Gallagher et al. (BMIGA) are commonly used to quantify body fat percentage (BF%). However, relative fat mass (RFM) is a new anthropometric-based method that has been proposed as an alternative. AIMS: The purpose of this study was to examine the independent and interactive effects of sex and BMI classification on the relative accuracy of BMI-based body fat equations and RFM. METHODS: Males (n = 75) and females (n = 75) were stratified and classified into three different groups; 1) normal weight (n = 50 [NW: 50% males]; BMI<25.0 kg/m2); 2) overweight (n = 50 [OW: 50% males]; BMI≥25.0-29.9 kg/m2); 3) obese (n = 50 [OB: 50% males]; BMI≥30.0 kg/m2). A criterion three-compartment model (3C model) was determined with air displacement plethysmography for body volume and multi-frequency bioimpedance analysis for total body water. Data were stratified by sex and BMI classification. Difference scores were created by subtracting estimated BF% from 3C model BF%. RESULTS: A significant SEX × BMI interaction was detected for all comparisons (all p < 0.05). Post hoc analysis indicated the differences in BF% were statistically significant between OW females and males for all equations (BMIWO:-2.99 ± 4.79% vs. 4.71 ± 5.86%, p = 0.003; BMIJA:-1.77 ± 4.83% vs. 5.77 ± 5.85%, p < 0.001; BMIDE:-3.09 ± 4.80% vs. 4.97 ± 5.98%, p < 0.001; BMIGA:0.36 ± 4.51% vs. 4.56 ± 5.55%, p = 0.018; RFM:-2.17 ± 4.84% vs. 3.01 ± 5.34%, p = 0.004, respectively). In addition, there were significant differences between females and males classified as NW (BMIJA:-2.11 ± 4.15% vs. 2.61 ± 5.98%, p = 0.008) and OB (BMIGA:2.40 ± 3.36% vs. -1.09 ± 6.40%, p = 0.006). CONCLUSIONS: The current findings highlight that RFM does not appear to overcome error commonly associated with BMI-based body fat equations when stratifying by sex and BMI classification. Nonetheless, practitioners can use BMIWO, BMIDE, and RFM in males and females classified as NW or OB, but should employ caution prior to use in OW persons.

Agreement Between 2 Segmental Bioimpedance Devices, BOD POD, and DXA in Obese Adults.

This study examined the agreement between 2 segmental bioimpedance analysis (BIA) devices, air displacement plethysmography (BOD POD), and dual energy X-ray absorptiometry (DXA) for estimating body composition in obese adults. Fifty obese adults (25 men and 25 women; age = 34.20 ± 11.19 years; BMI = 36.14 ± 5.33 kg/m2) had their body fat percentage (BF%) and fat-free mass (FFM) evaluated with 2 segmental BIA devices (InBody 230 and InBody 720), BOD POD, and DXA (Lunar iDXA). Body composition via the BOD POD was determined using the Siri equation whereas manufacturer-based equations generated metrics (ie, BF% and FFM) for the InBody devices. The effect size of the mean differences for all BF% and FFM comparisons were trivial (Cohen's d < 0.20). The standard error of estimate (SEE), total error (TE), and 95% limits of agreement (LOAs) were low for both segmental BIA devices when compared to DXA (SEE < 2.26% and 2.35 kg; TE < 2.58% and 2.66 kg; 95% LOAs < ± 4.94% and 4.86kg). The error for BOD POD was also low when compared to DXA (SEE = 2.39% and 2.57 kg; TE = 2.34% and 2.56 kg; 95% LOAs = 4.63% and 5.06 kg). Validity statistics were slightly higher, but considered acceptable, when comparing the segmental BIA devices against BOD POD (SEE < 3.37% and 3.63 kg; TE < 3.44% and 3.79 kg; 95% LOAs < ± 6.62% and 7.19 kg). Lastly, the 2 segmental BIA devices produced nearly identical validity statistics when compared to each other. However, both BIA devices revealed proportional bias for BF% and FFM when compared to the BOD POD and DXA (all p < 0.05). The current study's findings indicate the InBody 230 is interchangeable with the InBody 720 in obese adults. Also, the trivial effect size, when compared against the BOD POD and DXA, suggest the InBody devices could be used for estimating group BF% and FFM. In contrast, the significant proportional bias demonstrates the BIA devices are not acceptable for individual estimates of body composition in an obese clinical population.

Reliability and Agreement of Various InBody Body Composition Analyzers as Compared to Dual-Energy X-Ray Absorptiometry in Healthy Men and Women.

BACKGROUND: Bioelectrical impedance analysis has evolved over the years to include the use of multiple frequencies and impedance measurements to improve the accuracy and reliability of body composition estimates. The purpose of this investigation was to evaluate the reliability of the InBody230, InBody720, and InBody770 to measure body fat percent (BF%), fat mass (FM), and fat-free mass (FFM) in the general population and to compare results to dual-energy X-ray absorptiometry (DXA). METHODS: A total of 31 males and 36 females participated in 2 d of testing separated by 24-72 h. Each visit consisted of a DXA scan, and analysis with the InBody230, InBody720, and InBody770. RESULTS: All 3 bioelectrical impedance devices (InBody230, InBody720, and InBody770) were reliable in men and women as indicated by high intraclass correlation coefficients for BF% (≥0.98), FM (≥0.98), and FFM (≥0.99) and low standard error of measurement for BF% (0.77%-0.99%), FM (0.54-0.87 kg), and FFM (0.58-0.84 kg) and minimum difference for BF% (2.12%-2.73%), FM (1.49-2.39 kg), and FFM (1.60-2.32 kg), respectively. When examining the agreement between the 3 InBody analyzers with DXA, systematic bias (underestimation of BF% and FM and overestimation of FFM) was present for all comparisons (p < 0.05) while proportional bias was present for FM in women and FFM in men. However, there was small individual error for all comparisons as indicated by the standard error of estimate and 95% limits of agreement. CONCLUSION: The InBody analyzers produce small individual error, which suggest these methods can be used as a surrogate when DXA is not available; however, practitioners should be aware of the systematic bias for all comparisons and proportional bias for FM in women and FFM in men. Furthermore, findings revealed that the research grade models, InBody720 and InBody770, added minimal benefit over the portable InBody230 when assessing BF%, FM, and FFM.

Is Caffeine Recommended Before Exercise? A Systematic Review To Investigate Its Impact On Cardiac Autonomic Control Via Heart Rate And Its Variability.

Evaluating different doses of caffeine (CAF) on heart rate (HR) variability (HRV) during and following exercise in order to assess its impact on autonomic control. We intended to evaluate the influence of CAF as a supplement before exercise on HRV through a systematic review. Manuscripts were selected based on electronic searches of MEDLINE, EMBASE and CINAHL databases from 2010 to 2019 and followed the protocol Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA). Blind randomized designs and controlled trials that reported the influence of CAF on HRV during exercise and during recovery from exercise, with strength of evidence assessed using the GRADE system; the search for the studies was organized using the PICOS strategy. A total of 1797 articles were recognized, following the screening and eligibility stages, 9 studies continued to the final sample. Six studies reported that the combination of CAF supplementation with physical exercise exhibited higher HR when compared to the placebo group during post-exercise recovery; additionally, prolonged activation of sympathetic cardiac control and delayed parasympathetic reactivation following exercise was observed. However, three studies demonstrated no CAF influence when using similar doses. This review observed equivocal results in HR and HRV recovery following exercise with the presence of CAF consumption. These findings cannot confirm the cardiac autonomic changes observed where entirely due to the influence of CAF, and further studies should be performed to better understand this relationship.KEY TEACHING POINTSCAF increased HR during exercise and throughout the recovery period.CAF prolonged post exercise sympathetic activity.CAF delayed vagal reactivation.Deviations in HRV and HR are dependent on the combination of three main factors: CAF dosage, type of exercise, and cardiorespiratory fitness.

Pre-Anticipatory Anxiety and Autonomic Nervous System Response to Two Unique Fitness Competition Workouts.

To evaluate the feasibility of on-site collection of subjective anxiety, autonomic nervous system activity, and salivary catecholamines surrounding high-intensity functional training (HIFT) competition, ten experienced HIFT competitors completed baseline assessments of anxiety and heart rate variability (HRV). Then, in two consecutive weeks (Workout 1 and 2) within the competition, HRV was recorded and examined in 5-min segments prior to exercise (PRE) and across a 30-min period after competitors completed their choice of the prescribed or scaled each workout. Subjective anxiety ratings and saliva samples were collected at PRE and immediately-(IP), 30-min (30P), and 60-min post-exercise (60P). Saliva samples were analyzed for concentrations of epinephrine and norepinephrine. Generalized linear mixed models with repeated measures revealed significant (p < 0.05) differences between workouts for all measures. Compared to Workout 1, anxiety (~50%), epinephrine (173-340%), norepinephrine (29-234%) were greater in Workout 2 and various HRV-derived indices were more depressed. Additionally, some HRV-derived indices appeared to be modulated (p < 0.05) by competitive level and sex at PRE and throughout the 30-min recovery period. These data suggest that autonomic activity may differ between the competitive and laboratory settings, and that the response may be further modulated by the workout's design, the athlete's sex, and competitive level.

Autonomic responses induced by aerobic submaximal exercise in obese and overweight adolescents.

BACKGROUND: Graded exercises tests are performed in adult populations; nonetheless, the use of this type of assessment is greatly understudied in overweight and obese adolescents. OBJECTIVE: To investigate heart rate autonomic responses to submaximal aerobic exercise in obese and overweight adolescents. METHODS: We recruited 40 adolescents divided into two groups: (1) overweight group comprising 10 boys and 10 girls between Z-score +1 and +2 and (2) obese group comprising 10 boys and 10 girls above Z-score >+2. Heart rate variability was analysed before (T1) and after exercise (T2-T4) on treadmill at a slope of 0%, with 70% of the maximal estimated heart rate (220 - age) for 20 minutes. RESULTS: Heart rate in the overweight group was: 93.2±10.52 bpm versus 120.8±13.49 bpm versus 94.6±11.65 bpm versus 93.0±9.23 bpm, and in the obese group was: 92.0±15.41 bpm versus 117.6±16.31 bpm versus 92.1±12.9 bpm versus 91.8±14.33 bpm. High frequency in the overweight group was: 640±633.1 ms2 versus 84±174.66 ms2 versus 603.5±655.31 ms2 versus 762.6±807.21 ms2, and in the obese group was: 628.4±779.81 ms2 versus 65.4±119.34 ms2 versus 506.2±482.70 ms2 versus 677.9±939.05 ms2; and root mean square of successive differences in the overweight group was: 37.9±18.81 ms versus 10.9±8.41 ms versus 32.8±24.07 ms versus 36.7±21.86 ms, and in the obese group was: 38.7±23.17 ms versus 11.5±8.62 ms versus 32.3±16.74 ms versus 37.3±24.21 ms. These values significantly changed during exercise compared with resting values in overweight and obese groups. Moreover, we also reported no significant difference of resting parasympathetic control of heart rate between obese and overweight adolescents. CONCLUSION: There was no significant difference of autonomic responses elicited by submaximal aerobic exercise between overweight and obese adolescents.

Citrus Aurantium and caffeine complex versus placebo on biomarkers of metabolism: a double blind crossover design.

BACKGROUOND: The purpose of this study was to examine resting the metabolic response to the ingestion of a complex containing Citrus Aurantium + Caffeine (CA + C) and if its consumption influences metabolic recovery following a high-intensity anaerobic exercise bout in habitual caffeine users. METHODS: Ten physically active males (25.1 ± 3.9 years; weight 78.71 ± 9.53 kg; height 177.2 ± 4.6 cm; body fat 15.5 ± 3.13%) participated in this study. This study was performed in a double-blind, randomized crossover fashion consisting of two exhaustive exercise protocols. On each visit the participants consumed either a CA + C (100 mg of CA and 100 mg of C) or placebo (dextrose) capsule. After consumption, participants were monitored throughout a 45-min ingestion period, then completed a repeated Wingate protocol, and were then monitored throughout a 45-min recovery period. Metabolic function was measured through blood glucose, plasma insulin, plasma triglycerides, and plasma catecholamines: epinephrine (E) and norepinephrine (NE). Biomarkers were taken at four different time points; Ingestion period: baseline (I1), post-ingestion period (I2); Recovery period: immediately post-exercise (R1), post-recovery period (R2). RESULTS: A repeated measures ANOVA revealed significant time-dependent increases in plasma E and NE at I2 only in the CA + C trial (p < 0.05), and a significant decrease in blood glucose at I2 in the PLA trial (p < 0.05); however, no meaningful changes in glucose was observed following CA + C ingestion. No changes in insulin or triglycerides were observed during the ingestion period. No trial-dependent differences were observed in the Recovery period. All biomarkers of metabolic recovery were equivalent when evaluating R1 v R2. Participants recovered in a similar time-dependent manner in all markers of metabolism following the PLA and CA + C trials. CONCLUSION: The findings of this study suggested that normal recommended dosages of 100 mg CA + 100 mg C is sufficient to promote glucose sparing at rest, with modest increases in SNS activity; however, the individual role of CA or C in this response cannot be determined.