Increased sedentary time and decreased physical activity increases lipoprotein associated phospholipase A2 in obese individuals.

BACKGROUND AND AIMS: Lipoprotein-associated Phospholipase A2 (Lp-PLA2) is a protein produced by inflammatory cells in circulation and is associated with cardiovascular disease (CVD) risk. Physical activity (PA) is known to reduce inflammation and risk for CVD. However, Lp-PLA2 has yet to be examined in relation to PA and sedentary time. The purpose of this study was to determine if PA and sedentary time impacts Lp-PLA2 mass. A total of 25 subjects with an average BMI of 30.6 ± 5.7 were included in the data analysis. METHODS AND RESULTS: Data collected included anthropometric data, Lp-PLA2 mass, peak oxygen uptake (VO2peak), resting heart rate and blood pressure, obstructive sleep apnea (OSA) risk, and assessment of PA using an accelerometer. Sedentary minutes per day was positively associated with Lp-PLA2 (r = 0.41, P < 0.05). Light intensity PA was negatively associated (r = -0.51. P = 0.01) with Lp-PLA2. When subjects were divided into 2-quantiles by Lp-PLA2, the group with the higher Lp-PLA2 mass accumulated more sedentary time per day (P < 0.001) and less light intensity PA per day (P = 0.001). OSA risk and Lp-PLA2 showed no relationship. Sedentary behavior was higher, and light intensity PA was lower in subjects with hiLp-PLA2 mass. No difference was seen in moderate-to-vigorous intensity PA or steps per day. CONCLUSIONS: This suggests that, total PA habits, including time spent sedentary and lower intensity PA, impacts the levels of Lp-PLA2, an important inflammatory marker and marker of CVD risk.

Obstructive sleep apnea negatively impacts objectively measured physical activity.

PURPOSE: Obesity and obstructive sleep apnea (OSA) are frequent comorbid conditions. The impact of OSA on objectively measured physical activity (PA), independent of obesity, is not clear. The purpose of this study is to examine the effect of OSA on PA measured via accelerometer. METHODS: Overweight-to-obese individuals were recruited and screened for the presence of OSA via portable diagnostic device and divided into an OSA (n = 35) and control group (n = 24). Daytime sleepiness was assessed with the Epworth Sleepiness Scale. Body composition was assessed with dual-energy X-ray absorptiometry. Subjects wore an accelerometer (Actigraph GT3X+, Actigraph Corp., Pensacola, FL) for a minimum of 4 and maximum of 7 days, including at least one weekend day. RESULTS: There were no group differences in body mass index (BMI) or daytime sleepiness. Waist and neck circumference were higher in the OSA group. The OSA group was significantly older than the control group. The OSA group had fewer steps, moderate intensity minutes, moderate-to-vigorous minutes, number of PA bouts per day (≥ moderate intensity PA for ≥ 10 consecutive minutes), and total number of PA bouts. When adjusted for age, the PA bout data was no longer significant. CONCLUSION: Individuals screened as likely possessing OSA were less physically active than individuals without OSA when measured through objective means. We found no group differences in daytime sleepiness, BMI, or percent fat, suggesting other mechanisms than obesity and sleepiness for this difference.

Carbohydrate hydrogel beverage provides no additional cycling performance benefit versus carbohydrate alone.

PURPOSE: This study examined the effects of a novel maltodextrin-fructose hydrogel supplement (MF-H) on cycling performance and gastrointestinal distress symptoms. METHODS: Nine endurance-trained male cyclists (age = 26.1 ± 6.6, mass = 80.9 ± 10.4 kg, VO2max = 55.5 ± 3.6 mL·kg·min-1) completed three experimental trials consisting of a 98-min varied-intensity cycling protocol followed by a performance test of ten consecutive sprint intervals. In a cross-over design, subjects consumed 250 mL of a treatment beverage every 15 min of cycling. Treatments consisted of 78 g·hr-1 of either (a) MF-H, (b) isocaloric maltodextrin-fructose (ratio-matched 2:1; MF), and (c) isocaloric maltodextrin only (MD). RESULTS: There were no differences in average sprint power between treatments (MF-H, 284 ± 51 W; MF, 281 ± 46 W; and MD, 277 ± 48 W), or power output for any individual sprint. Subjective ratings of gastrointestinal distress symptoms (nausea, fullness, and abdominal cramping) increased significantly over time during the cycling trials, but few individuals exceeded moderate levels in any trial with no systematic differences in gastrointestinal discomfort symptoms observed between treatments. CONCLUSIONS: In conclusion, ingestion of a maltodextrin/fructose hydrogel beverage during high-intensity cycling does not improve gastrointestinal comfort or performance compared to MF or MD beverages.

The effect of acute aerobic exercise on hemostasis in obstructive sleep apnea.

PURPOSE: Individuals with obstructive sleep apnea (OSA) have an altered hemostatic balance; however, the exercise response is less described. The purpose of this study is to determine the hemostatic response after acute aerobic exercise in obstructive sleep apnea. METHODS: Eighteen males (nine OSA vs. nine controls) were recruited from the university and local community. Individuals with evidence of cardiovascular, pulmonary, or metabolic disease were excluded. An apnea-hypopnea index (AHI) of >5 was a criterion for OSA. Subjects performed a treadmill exercise test at 35 and 70% predicted VO2 reserve during the morning hours. Pre-exercise blood samples were obtained after 15 min supine rest and within 2 min following exercise. Repeated measures ANOVA were performed for factor VIII antigen, tissue plasminogen activator (tPA) antigen, tPA activity, and PAI-1 activity. Correlational analysis compared resting and post-exercise hemostatic factors with age, BMI, and AHI. RESULTS: Mean AHI was 13.00 ± 12.6. No exercise × condition interactions were observed for hemostatic markers. There was a main effect for exercise in factor VIII, tPA antigen, and tPA activity in both groups. PAI-1 activity tended to be elevated in OSA (145%) compared to controls which remained after exercise (205%) (P = 0.05). Post-exercise FVIII/Ag correlated with BMI (r = 0.52), while resting tPA/Ag correlated with AHI (r = 0.49) and age (r = 0.50). CONCLUSION: The hemostatic response after acute aerobic exercise is unaffected in mild OSA, although PAI-1 activity seems to be elevated, reducing fibrinolytic potential. BMI seems to correlate with FVIII/Ag, while tPA/Ag is associated with AHI and age.

Arterial adaptations to training among first time marathoners.

BACKGROUND: Exercise training favorably alters arterial anatomy in trained limbs, though the simultaneous effects on passively trained arteries are unclear. Thus, brachial (non-trained limb), popliteal (trained limb) and carotid total wall thickness (TWT), wall-to-lumen ratios (W:L), intima-media thickness (IMT) and lumen diameters (LD) were compared between experimental (n = 14) and control (n = 11) participants before and after the experimental participants participated in marathon training. METHODS: Arterial dimensions were measured with B-mode ultrasonography. Initial and final testing of VO2max and running speed at 3.5 mmol lactate were measured in the experimental group. RESULTS: VO2max was unchanged by training, but running speed at 3.5 mmol lactate increased by 5 % (p = .008). Time by group interactions were observed for the brachial and popliteal measures (p < 0.05), but not the carotid. No changes were observed in the control group. Prior to the intervention the experimental group had larger LD in the brachial (p = .002) and popliteal arteries (p = .007) than controls; no other pre-testing differences were found. Following training, TWT declined in the brachial (pre = .99 ± .16 mm; post = .84 ± .10 mm; p = .007) and popliteal (pre = .96 ± .09 mm; post = .86 ± .11 mm; p = .005) arteries, characterized by a 0.07 mm decrease in brachial IMT (p = .032) and a non-significant 0.03 mm reduction in popliteal IMT. LD increased in the brachial (pre = 3.38 ± .35 mm; post = 3.57 ± .41 mm; p = .015) and popliteal (pre = 4.73 ± .48 mm; post = 5.11 ± .72 mm; p = .002) arteries. CONCLUSIONS: These data suggest that exercise-induced alterations in arterial dimensions occur in trained and non-trained limbs, and that adaptations may be dose dependent.

A matrix approach to guide IHC-based tissue biomarker development in oncology drug discovery.

Immunohistochemistry (IHC) is a core platform for the analysis of tissue samples, and there is an increasing demand for reliable and quantitative IHC-based tissue biomarkers in oncology clinical research and development (R&D) environments. Biomarker assay and drug development proceed in parallel. Furthermore, biomarker assay requirements change with each phase of drug development. We have therefore developed a matrix tool to enable researchers to evaluate whether a particular IHC biomarker assay is fit for purpose. Experience gained from the development of 130 IHC biomarkers, supporting a large number of oncology drug projects, was used to formulate a practical approach to IHC assay development. The resultant matrix grid and accompanying work flow incorporates 16 core decision points that link antibody and assay specificity and sensitivity, and assay performance in preclinical and clinical samples, with stages of drug development. The matrix provides a means to ensure that relevant information on an IHC assay in development is recorded and communicated consistently and that minimum assay validation requirements are met.

Human biological sample biobanking to support tissue biomarkers in pharmaceutical research and development.

Advances in the understanding of molecular pathology and thereby the mechanisms that could be amenable to therapeutic manipulation are the reason that pharmaceutical research and development is focused increasingly on measurement of molecular biomarkers in human biological samples. Obtaining direct or indirect access to sufficient samples that are fit for research purposes can be a major challenge. A biobanking infrastructure has a significant role in the acquisition, storage and usage of human biological samples and here we review some key requirements for establishing a biobank. These include ensuring; that appropriate governance mechanisms are in place, that samples available are appropriate and fit for the intended research purposes that the infrastructure is sustainable in the future and that use of the biobank assets meets the strategic aims of the host organisation. Finally we present a case study--the STRATUM project which has recently completed and through a collaborative approach involving six industry and public partners drawing on a network of experts, examined biobank policies, public attitudes to biobanking, donor consent, sample and data standards, technical requirements for a register and biobanking financial models, albeit from a UK perspective.

Age and aerobic training status effects on plasma and skeletal muscle tPA and PAI-1.

INTRODUCTION: Reductions in fibrinolytic potential occur with both aging and physical inactivity and are associated with an increased cardiovascular disease risk. Plasmin, the enzyme responsible for the enzymatic degradation of fibrin clots, is activated by tissue plasminogen activator (tPA), while plasminogen activator inhibitor-1 (PAI-1) inhibits its activation. Currently, fibrinolysis research focuses almost exclusively on changes within the plasma. However, tPA and PAI-1 are expressed by human skeletal muscle (SM). Currently, no studies have focused on changes in SM fibrinolytic activity with regard to aging and aerobic fitness. PURPOSE: The purpose of this study was to cross-sectionally evaluate effects of age and aerobic fitness on tPA and PAI-1 expressions and activity in SM. METHODS: Twenty-six male subjects were categorized into the following groups: (1) young aerobically trained (n = 8); (2) older aerobically trained (n = 6); (3) young aerobically untrained (n = 7); and (4) older aerobically untrained (n = 5). Muscle biopsies were obtained from each subject. SM tPA activity was assessed using gel zymography and SM tPA and PAI-1 expressions were assessed using RT-PCR. RESULTS: Trained subjects had higher SM tPA activity compared to untrained (25.3 ± 2.4 × 10(3) vs. 21.5 ± 5.6 × 10(3) pixels, respectively; p = 0.03) with no effect observed for age. VO2 max and SM tPA activity were also significantly correlated (r = 0.42; p < 0.04). SM tPA expression was higher in older participants, but no effect of fitness level was observed. No differences were observed for PAI-1 expression in SM. CONCLUSIONS: Higher levels of aerobic fitness are associated with increased fibrinolytic activity in SM.

Cycling time trial performance may be impaired by whey protein and L-alanine intake during prolonged exercise.

Previous studies reported that adding protein (PRO) to carbohydrate (CHO) solutions enhances endurance performance. The ergogenic effect may be a function of additional protein/amino acid calories, but this has not been examined. In addition, although supplemental L-alanine (ALA) is readily oxidized during exercise, the subsequent impact on metabolism and prolonged endurance performance is unknown. The purpose of this investigation was to independently gauge the impact of whey PRO hydrolysate and ALA supplementation on performance and various physiological parameters. Eight cyclists (age: 22.3 ± 5.6 yr, weight: 70.0 ± 8.0 kg, VO2max: 59.4 ± 4.9 ml · kg(-1) · min(-1)) performed 120 min of constant-load cycling (55% of peak power) followed by a 30-km time trial (TT) under placebo (PLA), PRO, and ALA conditions. Magnitude-based qualitative inferences were applied to evaluate treatment differences and data are presented as percent difference between treatments ± 90% confidence limit. Both ALA (2.1 ± 2.7%) and PRO intake (-2.1 ± 2.2%) possibly harmed performance compared with PLA. Of interest, heart rate was possibly lower with ALA than PLA at 20- (-2.7 ± 3.4%) and 120-min (-1.7 ± 2.9%) of constant-load cycling and the serum interleukin-6 (IL-6) response to 120 min of cycling was likely attenuated with PRO compared with PLA (PLA, 6.6 ± 3.7 fold vs. PRO, 2.9 ± 1.8 fold). In addition, blood glucose levels were lower with PRO than PLA at 20- (-8.8 ± 2.3%; very likely) and 120-min (-4.9 ± 4.6%; likely) of constant-load cycling. Although ALA intake appears to lower HR and PRO ingestion dampens the IL-6 response to exercise, the ingestion of PRO (without CHO) or ALA does not enhance, and may actually impair, performance following prolonged cycling.

Strength training increases endurance time to exhaustion during high-intensity exercise despite no change in critical power.

The purpose of this study was to determine whether improvements in endurance exercise performance elicited by strength training were accurately reflected by changes in parameters of the power-duration hyperbola for high-intensity exercise. Before and after 8 weeks of strength training (N = 14) or no exercise, control (N = 5), 19 males (age: 20.6 ± 2.0 years; weight: 78.2 ± 15.9 kg) performed a maximal incremental exercise test on a cycle ergometer and also cycled to exhaustion during 4 constant-power exercise bouts. Critical power (CP) and anaerobic work capacity (W') were estimated using nonlinear and linear models. Subjects in the strength training group improved significantly more than controls (p < 0.05) for strength (~30%), power at V[Combining Dot Above]O2peak (7.9%), and time to exhaustion (TTE) for all 4 constant-power tests (~39%). Contrary to our hypothesis, CP did not change significantly after strength training (p > 0.05 for all models). Strength training improved W' (mean range of improvement = +5.8 to +10.0 kJ; p < 0.05) for both linear models. Increases in W' were consistently positively correlated with improvements in TTE, whereas changes in CP were not. Our findings indicate that strength training alters the power-duration hyperbola such that W' is enhanced without any improvement in CP. Consequently, CP may not be robust enough to track changes in endurance capacity elicited by strength training, and we do not recommend it to be used for this purpose. Conversely, W' may be the better indicator of improvement in endurance performance elicited by strength training.

Concordance of ATM (ataxia telangiectasia mutated) immunohistochemistry between biopsy or metastatic tumor samples and primary tumors in gastric cancer patients.

ATM (ataxia telangiectasia mutated) is one of several DNA repair proteins that are suggested to sensitize tumor cells to the poly(ADP-ribose) polymerase inhibitor olaparib when deficient. The aim of this study was to assess the spatiotemporal concordance of ATM immunohistochemistry (IHC) in gastric cancer in order to determine if measurements made at the level of various sample types and times could be inferred as having the potential to be relevant to treatment decisions made at the patient level. Two independent cohorts composed of 591 gastric cancer patients divided into a gastrectomy cohort (n = 450) and a metastasis cohort (n = 141) were used in this study. A total of 2,705 ATM IHC samples were examined, including 450 whole tissue, 3 sets of 450 tissue microarray (TMA), 301 biopsy, 222 metastatic tumor and 2 additional whole tissue samples of 50 cases from the gastrectomy cohort, and 141 pairs of primary and metastatic tumors from the metastasis cohort. The prevalence of ATM negativity was 13.1% in biopsies, 13.9, 15.1, and 16.0% in TMAs and 15.9% in whole tissue samples of the gastrectomy cohort, and 21.4% in primary tumor and 21.5% in metastatic tumor samples of the metastasis cohort. coefficients were 0.341 for biopsy, 0.572 as the average of 3 TMAs and 0.415 for the largely synchronous metastatic tumors of the gastrectomy cohort, and 0.153 for the largely asynchronous metastatic tumors of the metastasis cohort. Using whole tissue sections from tumor resections or primary tumor, respectively, as the reference standards, specificity and sensitivity were 91.6 and 41.0% for biopsy, 93.9 and 61.9% as the average of 3 TMAs, and 86.6 and 58.8% for metastatic tumors of the gastrectomy cohort and 81.7 and 33.3% for metastatic tumors of the metastasis cohort, respectively. Although we have demonstrated that the IHC assay for ATM was robust and reproducible in gastric tumor samples, we have also found that measurements were subject to significant discordance across multiple sample types from the same patient. Further work will be necessary to determine if classification may be made more consistent by multiple sampling. However, the lack of agreement between primary and asynchronous metastatic samples suggests that such sampling would need to be performed at the time of any treatment decision.

The efficacy of a verification stage for determining V˙O2max and the impact of sampling intervals.

It is unknown whether oxygen uptake (V̇O2) sampling intervals influence the efficacy of a verification stage following a graded exercise test (GXT). Fifteen females and 14 males (18-25 years) completed a maximal treadmill GXT. After a 5 â€‹min recovery, the verification stage began at the speed and grade corresponding with the penultimate stage from the GXT. Maximal oxygen consumption (V̇O2max) from the incremental GXT (iV̇O2max) and V̇O2max from the verification stage (verV̇O2max) were determined using 10 seconds (s), 30 â€‹s, and 60 â€‹s from breath â€‹× â€‹breath averages. There was no main effect for V̇O2max measure (iV̇O2maxvs. verV̇O2max) 10 â€‹s ([47.9 â€‹± â€‹8.31] ml∙kg-1∙min-1 vs [48.85 â€‹± â€‹7.97] ml∙kg-1∙min-1), 30 â€‹s ([46.94 â€‹± â€‹8.62] ml∙kg-1∙min-1 vs [47.28 â€‹± â€‹7.97] ml∙kg-1∙min-1), and 60 â€‹s ([46.17 â€‹± â€‹8.62] ml∙kg-1∙min-1 vs [46.00 â€‹± â€‹8.00] ml∙kg-1∙min-1]. There was a stage â€‹× â€‹sampling interval interaction as the difference between (verV̇O2max-iV̇O2max) was greater for 10-s than 60-s sampling intervals. The verV̇O2max was > 4% higher than iV̇O2maxin 31%, 31%, and 17% of the tests for the 10-s, 30-s, and 60-s sampling intervals respectively. Sensitivity for the plateau was < 30% for 10-s, 30-s, and 60-s sampling intervals. Specificity ranged from 44% to 60% for all sampling intervals. Sensitivity for heart rate â€‹+ â€‹respiratory exchange ratio was > 90% for all sampling intervals; while specificity was < 25%. Findings from the present study suggest that the efficacy of verification stages for eliciting a higher V̇O2max may be influenced by the sampling interval utilized.

Body composition measured by multi-frequency bioelectrical impedance following creatine supplementation.

BACKGROUND: Acute fluid ingestion increases estimated body fat percentage (BF%) measurements by single frequency (SF-BIA) and multi-frequency bioelectrical impedance (MF-BIA). It is unknown if MF-BIA accurately measures total BF% and total body water (TBW) after creatine supplementation, which causes fluid retention, and resultant increases in fat-free mass and TBW. The purpose of this study was to analyze the effect of creatine supplementation on body composition and TBW measured through a popular MF-BIA device (InBody 770). METHODS: Thirteen male and 14 female subjects (18-22 years) completed one week of creatine monohydrate (0.3 g/kg body weight) or maltodextrin. Pre- and post-supplementation body composition measurements included dual-energy X-ray absorptiometry (DEXA), SF-BIA measured by an Omron HBF-306C device, and MF-BIA measured by an InBody 770 device to measure BF%, fat free mass (FFM), and fat mass (FM). Additionally, intracellular water (ICW), extracellular water (ECW), and TBW were estimated by MF- BIA. RESULTS: FFM increased more in the creatine group than the placebo group measured by all body composition modes (1.2 kg, 1.9 kg, and 1.1 kg increase for SF-BIA, MF-BIA, and DEXA respectively, P<0.05). Creatine supplementation resulted in a 2% increase (P<0.05) in TBW measured by MF-BIA (40.4±9.5 to 41.2±9.6 kg). CONCLUSIONS: One week of creatine supplementation increased TBW as detected by the InBody 770 device. Changes in body composition that occurred due to the increase in TBW were detected as an increase in FFM measured by SF-BIA, MF-BIA, and DEXA.

Caffeine Enhances 10-km Cycling Performance in Habitual Users Only When Preceded by Caffeine Abstinence.

PURPOSE: The primary objective was to assess the performance benefits of caffeine (CAF) supplementation in habitual users. Importantly, this investigation was designed to account for the potential confounding effects of CAF withdrawal (CAFW), which are inherent and common in previous work. METHODS: Ten CAF-consuming (394 [146] mg·d-1) recreational cyclists (age 39.1 [14.9] y; maximum oxygen consumption 54.2 [6.2] mL·kg-1·min-1) completed four 10-km time trials (TTs) on a cycle ergometer. On each trial day, 8 hours before reporting to the laboratory, subjects consumed 1.5 mg·kg-1 CAF to prevent withdrawal (no withdrawal [N]) or a placebo (PLA; withdrawal [W]). Then, 1 hour prior to exercise, they received either 6 mg·kg-1 CAF or PLA. These protocols were repeated 4 times, employing all combinations of N/W and CAF/PLA. RESULTS: CAFW did not impair TT power output (PLAW vs PLAN P = .13). However, preexercise CAF only improved TT performance when compared to PLA in the W condition (CAFN vs PLAW P = .008, CAFW vs PLAW P = .04), not when W was mitigated (PLAN vs CAFN P = .33). CONCLUSIONS: These data indicate that preexercise CAF only improves recreational cycling performance when compared to bouts preceded by CAF abstinence, suggesting that habitual users may not benefit from 6 mg·kg-1 of CAF and that previous work may have overstated the value of CAF supplementation for habitual users. Future work should examine higher doses of CAF for habitual users.

The impact of COVID-19 on pulmonary function and airway reactivity after recovery in college-aged adults.

The purpose of this study was to determine (1) whether pulmonary function is reduced, and airway reactivity is increased after recovery from COVID-19 in individuals who did not have severe illness, and (2) whether physical activity levels had any impact on pulmonary function or airway reactivity. An exploratory aim of the study was also to assess whether number of symptoms was associated with pulmonary function outcomes. The maximal flow volume loop was used to measure pulmonary function in individuals who had previously tested positive for COVID-19 (COV; n = 20, 23.0 ± 5.4 years) and those who had not (CON; n = 20, 23.7 ± 5.5 years) before and after a hypertonic saline challenge (HSC) designed to increase airway reactivity. Self-reported symptoms and physical activity levels (MET (min/week)) were collected to examine their correlation with pulmonary outcomes. There were no significant differences in any pulmonary function outcomes between the COV and CON groups before or after the HSC. There were also no associations between physical activity and pulmonary function outcomes. However, among participants who reported greater than four symptoms, there was a larger decline in forced expiratory volume in 1 s divided by forced vital capacity following HSC (p = 0.035). Pulmonary function and airway reactivity are not impacted after recovery from COVID-19 in young individuals; however, it appears that the number of symptoms reported may be associated with increased airway reactivity even after recovery in young adults who were not hospitalized with the virus.

The effect of acute hydration on body composition assessed by multi-frequency and single-frequency bioelectrical impedance.

BACKGROUND: Multi-frequency bioelectrical impedance (MF-BIA) provides an estimate of total body water. However, it is unknown if MF-BIA detects body water increases due to acute hydration, thus affecting the validity of MF-BIA body composition measurements. The purpose of this study was to compare the effects of pre-testing fluid ingestion on body composition estimation using single-frequency bioelectrical impedance (SF-BIA) and MF-BIA. METHODS: Thirty-nine subjects (20 male, 19 female) were tested for body composition using DXA, SF-BIA and MF-BIA before and after consumption of 2 L of water. RESULTS: Hydration significantly increased fat percentage in men and women for MF-BIA (+2.1±0.7% for men, +2.6±0.7% for women) and SF-BIA (+1.3±0.7% for men, +2.1±0.9% for women). Additionally, hydration significantly increased fat-free mass (FFM) for DXA (+1.4±0.8 kg for men, +1.7±0.4 kg for women) and SF-BIA (+0.5±0.6 kg) in men. Hydration significantly increased fat mass (FM) for all modes (DXA +0.3±0.3 kg, MF-BIA +2.0±0.7 kg, SF-BIA +1.3±0.6 kg) in males, and only for MF-BIA (+2.2±0.3 kg) and SF-BIA (+1.7±0.5 kg) in females. Increases in FM were highest for MF-BIA for both males and females. Total body water was unchanged in males and significantly decreased with acute hydration in females. CONCLUSIONS: MF-BIA improperly categorizes increased mass due to acute hydration as fat mass, resulting in an increase in measured body fat percentage. These findings confirm the need to standardize hydration status for body composition measurements using MF-BIA.

The influence of the CYP1A2-163 C>A polymorphism on the hemostatic response to exercise following caffeine supplementation.

BACKGROUND: Prior work from our group suggests that caffeine increases thrombotic potential after acute exercise. The aim of this study was to determine if hemostatic responses to exercise affected by caffeine are influenced by the CYP1A2-163 C>A polymorphism. METHODS: Forty-two healthy men performed two trials in which a graded maximal exercise test was completed one hour after consuming either 6 mg/kg of caffeine or placebo. Subjects were categorized as possessing the C allele (N.=21) or being homozygous for the A allele (N.=21). RESULTS: Factor VIII increased more (265%) during exercise in the caffeinated condition than the placebo condition (178%) (P<0.05). Tissue plasminogen activator (tPA) activity also increased more following caffeine as compared to placebo (increase of 8.70±4.32 IU/mL vs. 6.77±3.79 IU/mL respectively, P<0.05). There was no treatment × genotype or treatment × time × genotype interactions. CONCLUSIONS: Although caffeine increases factor VIII and tPA responses to maximal exercise, these changes are not influenced by the CYP1A2-163 C>A polymorphism.

Reliability of the heart rate variability threshold during treadmill exercise.

The heart rate variability threshold (HRVT) is a clinical parameter used to gain insight into autonomic balance. Prior validation of the HRVT has been with cycle ergometry, with no studies examining the viability of treadmill exercise. The purpose of this study was to examine the reliability of the HRVT during treadmill exercise, and to compare the HRVT to the ventilatory threshold (VT). Ten healthy, college-aged males completed two maximal graded exercise tests on a treadmill. A Polar RS800CX watch was used for heart rate and HRVT data. The HRVT was determined from three HRV variables including the root mean square of successive differences of continuous R-R intervals (RMSSD), the standard deviation of normal R-R intervals (SDNN) and the standard deviation of instantaneous beat intervals (SD1). A metabolic cart was utilized to determine the VT. Results showed no difference between the HRVT (2.4 ± 0.6 and 2.2 ± 0.3 for RMSSD, 2.8 ± 0.5 and 2.7 ± 0.5 for SDNN and 2.4 ± 0.6 and 2.3 ± 0.6 for SD1) or the VT (3.0 ± 0.3 and 3.1 ± 0.3) between trials. When compared to the VT, averaged HRVT values for RMSSD (2.3 ± 0.3) and SD1 (2.3 ± 0.5) were lower than averaged VT (2.8 ± 0.4, p < 0.05). The averaged HRVT from SDNN (2.8 ± 0.5) did not differ from the VT. These results suggest that treadmill is a viable mode for HRVT determination, and that HRVT determined by SDNN may be a better comparison to the VT.

Physiological differences in cardiovascular hemodynamics across treadmill and cycle exercise as assessed through impedance cardiography.

Impedance cardiography (IC) is a non-invasive method for assessing cardiovascular hemodynamics, and has been utilised during exercise, exclusively on a cycle ergometer. Mode-specific differences in cardiovascular hemodynamics during exercise have previously been identified, but the ability of IC to identify these differences has not been explored. Therefore, we examined the repeatability of cardiovascular hemodynamics within and between exercise modes on the treadmill (TM) and cycle (CY) ergometer. Twenty-one men (age = 21.4 ± 0.5 yr) performed four maximal exercise, two TM and two CY. Within each test, two, five-minute stages were completed corresponding to moderate and vigorous exercise intensities, respectively. Oxygen consumption (VO2) was measured continuously during each test. Hemodynamic measures were obtained via IC, and included cardiac output (CO), heart rate (HR), stroke volume (SV), end diastolic volume (EDV), ejection fraction (EF), and systemic vascular resistance (SVR). Repeated measures ANOVA revealed that within TM exercise, there was a main effect for trial with HR only. There were no main effects for trial within CY exercise. Across exercise modes, there were significant main effects for mode with HR, EDV, and SVR. CY exercise resulted in a higher HR, lower SV and EDV, consistent with previous findings, utilising more criterion and invasive methods. Results suggest that hemodynamics, as assessed by IC, are repeatable within TM and CY exercise. In addition, it appears as though IC is capable of detecting mode-specific differences in hemodynamics, suggesting IC to be a useful assessment tool during exercise.

Caffeine added to coffee does not alter the acute testosterone response to exercise in resistance trained males.

BACKGROUND: This study investigated the effects of coffee ingestion with supplemental caffeine (CAF) on serum testosterone (T) responses to exercise in recreationally strength-trained males. METHODS: Subjects ingested 6 mg/kg body weight of caffeine via 12 ounces of coffee (CAF) supplemented with anhydrous caffeine or decaffeinated (DEC) coffee prior to exercise in a randomized, within-subject, crossover design. The exercise session consisted of 21 minutes of high-intensity interval cycling (alternating intensities at power outputs associated with 2.0 mmol/L lactate for two minutes and 4.0 mmol/L lactate for one minute) followed by resistance exercise (seven exercises, three sets of ten repetitions, 65% 1RM, one-minute rest periods). Subjects also completed repetitions to fatigue tests and soreness scales to determine muscle recovery 24 hours following the exercise. RESULTS: T was elevated immediately and 30-minutes post-exercise by 20.5% and 14.3% respectively (P<0.05). There was no main effect for treatment and no exercise x treatment interaction. There were no differences in repetitions to fatigue or soreness between treatments (P>0.05). No relationships were observed between T and any proxy of recovery. CONCLUSIONS: While past literature suggests caffeine may enhance T post-exercise, data from the current study suggest that augmented T response is not evident following anhydrous caffeine added to coffee. The duration of T elevation indicates that this protocol is beneficial to creating long-lasting increases in serum testosterone.