Myths and Methodologies: Standardisation in human physiology research-should we control the controllables?

The premise of research in human physiology is to explore a multifaceted system whilst identifying one or a few outcomes of interest. Therefore, the control of potentially confounding variables requires careful thought regarding the extent of control and complexity of standardisation. One common factor to control prior to testing is diet, as food and fluid provision may deviate from participants' habitual diets, yet a self-report and replication method can be flawed by under-reporting. Researchers may also need to consider standardisation of physical activity, whether it be through familiarisation trials, wash-out periods, or guidance on levels of physical activity to be achieved before trials. In terms of pharmacological agents, the ethical implications of standardisation require researchers to carefully consider how medications, caffeine consumption and oral contraceptive prescriptions may affect the study. For research in females, it should be considered whether standardisation between- or within-participants in regards to menstrual cycle phase is most relevant. The timing of measurements relative to various other daily events is relevant to all physiological research and so it can be important to standardise when measurements are made. This review summarises the areas of standardisation which we hope will be considered useful to anyone involved in human physiology research, including when and how one can apply standardisation to various contexts.

Myths and Methodologies: Standardisation in Human Physiology Research-Should We Control the Controllables?

The premise of research in human physiology is to explore a multifaceted system whilst identifying one or a few outcomes of interest. Therefore, the control of potentially confounding variables requires careful thought regarding the extent of control and complexity of standardisation. One common factor to control prior to testing is diet, as food and fluid provision may deviate from participants' habitual diets, yet a self-report and replication method can be flawed by under-reporting. Researchers may also need to consider standardisation of physical activity, whether it be through familiarisation trials, wash-out periods, or guidance on levels of physical activity to be achieved before trials. In terms of pharmacological agents, the ethical implications of standardisation require researchers to carefully consider how medications, caffeine consumption and oral contraceptive prescriptions may affect the study. For research in females, it should be considered whether standardisation between- or within-participants in regards to menstrual cycle phase is most relevant. The timing of measurements relative to various other daily events is relevant to all physiological research and so it can be important to standardise when measurements are made. This review summarises the areas of standardisation which we hope will be considered useful to anyone involved in human physiology research, including when and how one can apply standardisation to various contexts.

Characterising 24-h skeletal muscle gene expression alongside metabolic & endocrine responses under diurnal conditions.

CONTEXT: Skeletal muscle plays a central role in the storage, synthesis, and breakdown of nutrients, yet little research has explored temporal responses of this human tissue, especially with concurrent measures of systemic biomarkers of metabolism. OBJECTIVE: To characterise temporal profiles in skeletal muscle expression of genes involved in carbohydrate metabolism, lipid metabolism, circadian clocks, and autophagy and descriptively relate them to systemic metabolites and hormones during a controlled laboratory protocol. METHODS: Ten healthy adults (9M/1F, mean ± SD: age: 30 ± 10 y; BMI: 24.1 ± 2.7 kg·m-2) rested in the laboratory for 37 hours with all data collected during the final 24 hours of this period (i.e., 0800-0800 h). Participants ingested hourly isocaloric liquid meal replacements alongside appetite assessments during waking before a sleep opportunity from 2200-0700 h. Blood samples were collected hourly for endocrine and metabolite analyses, with muscle biopsies occurring every 4 h from 1200 h to 0800 h the following day to quantify gene expression. RESULTS: Plasma insulin displayed diurnal rhythmicity peaking at 1804 h. Expression of skeletal muscle genes involved in carbohydrate metabolism (Name - Acrophase; GLUT4 - 1440 h; PPARGC1A -1613 h; HK2 - 1824 h) and lipid metabolism (FABP3 - 1237 h; PDK4 - 0530 h; CPT1B - 1258 h) displayed 24 h rhythmicity that reflected the temporal rhythm of insulin. Equally, circulating glucose (0019 h), NEFA (0456 h), glycerol (0432 h), triglyceride (2314 h), urea (0046 h), CTX (0507 h) and cortisol concentrations (2250 h) also all displayed diurnal rhythmicity. CONCLUSION: Diurnal rhythms were present in human skeletal muscle gene expression as well systemic metabolites and hormones under controlled diurnal conditions. The temporal patterns of genes relating to carbohydrate and lipid metabolism alongside circulating insulin are consistent with diurnal rhythms being driven in part by the diurnal influence of cyclic feeding and fasting.

Nitrate ingestion blunts the increase in blood pressure during cool air exposure: a double-blind, placebo-controlled, randomized, crossover trial.

Cold exposure increases blood pressure (BP) and salivary flow rate (SFR). Increased cold-induced SFR would be hypothesized to enhance oral nitrate delivery for reduction to nitrite by oral anaerobes and to subsequently elevate plasma [nitrite] and nitric oxide bioavailability. We tested the hypothesis that dietary nitrate supplementation would increase plasma [nitrite] and lower BP to a greater extent in cool compared with normothermic conditions. Twelve males attended the laboratory on four occasions. Baseline measurements were completed at 28°C. Subsequently, participants ingested 140 mL of concentrated nitrate-rich (BR; ∼13 mmol nitrate) or nitrate-depleted (PL) beetroot juice. Measurements were repeated over 3 h at either 28°C (Norm) or 20°C (Cool). Mean skin temperature was lowered compared with baseline in PL-Cool and BR-Cool. SFR was greater in BR-Norm, PL-Cool, and BR-Cool than PL-Norm. Plasma [nitrite] at 3 h was higher in BR-Cool (592 ± 239 nM) versus BR-Norm (410 ± 195 nM). Systolic BP (SBP) at 3 h was not different between PL-Norm (117 ± 6 mmHg) and BR-Norm (113 ± 9 mmHg). SBP increased above baseline at 1, 2, and 3 h in PL-Cool but not BR-Cool. These results suggest that BR consumption is more effective at increasing plasma [nitrite] in cool compared with normothermic conditions and blunts the rise in BP following acute cool air exposure, which might have implications for attenuating the increased cardiovascular strain in the cold.NEW & NOTEWORTHY Compared with normothermic conditions, acute nitrate ingestion increased plasma [nitrite], a substrate for oxygen-independent nitric oxide generation, to a greater extent during cool air exposure. Systolic blood pressure was increased during cool air exposure in the placebo condition with this cool-induced blood pressure increase attenuated after acute nitrate ingestion. These findings improve our understanding of environmental factors that influence nitrate metabolism and the efficacy of nitrate supplementation to lower blood pressure.

Substituting carbohydrate at lunch for added protein increases fat oxidation during subsequent exercise in healthy males.

CONTEXT: How pre-exercise meal composition influences metabolic and health responses to exercise later in the day is currently unclear. OBJECTIVE: Examine the effects of substituting carbohydrate for protein at lunch on subsequent exercise metabolism, appetite, and energy intake. METHODS: Twelve healthy males completed three trials in randomized, counterbalanced order. Following a standardized breakfast (779 ± 66 kcal; ∼08:15), participants consumed a lunch (1186 ± 140 kcal; ∼13:15) containing either 0.2 g·kg-1 carbohydrate and ∼2 g·kg-1 protein (LO-CARB), 2 g·kg-1 carbohydrate and ∼0.4 g·kg-1 protein (HI-CARB), or fasted (FAST). Participants later cycled at ∼60% V̇O2peak for 1 h (∼16:15) and post-exercise ad-libitum energy intake was measured (∼18:30). Substrate oxidation, subjective appetite, and plasma concentrations of glucose, insulin, non-esterified fatty acids (NEFA), peptide YY (PYY), glucagon-like peptide-1 (GLP-1), and acylated ghrelin (AG) were measured for 5 h post-lunch. RESULTS: Fat oxidation was greater during FAST (+11.66 ± 6.63 g) and LO-CARB (+8.00 ± 3.83 g) than HI-CARB (p < 0.001), with FAST greater than LO-CARB (+3.67 ± 5.07 g; p < 0.05). NEFA were lowest in HI-CARB and highest in FAST, with insulin demonstrating the inverse response (all p < 0.01). PYY and GLP-1 demonstrated a stepwise pattern, with LO-CARB greatest and FAST lowest (all p < 0.01). AG was lower during HI-CARB and LO-CARB versus FAST (p < 0.01). Energy intake in LO-CARB was lower than FAST (-383 ± 233 kcal; p < 0.001) and HI-CARB (-313 ± 284 kcal; p < 0.001). CONCLUSION: Substituting carbohydrate for protein in a pre-exercise lunch increased fat oxidation, suppressed subjective and hormonal appetite, and reduced post-exercise energy intake.

How Cool is That? The Effects of Menthol Mouth Rinsing on Exercise Capacity and Performance: A Systematic Review and Meta-analysis.

BACKGROUND: Menthol (MEN) mouth rinsing (MR) has gained considerable interest in the athletic population for exercise performance; however, the overall magnitude of effect is unknown. OBJECTIVE: The aim of this systematic review and meta-analysis was to determine the efficacy of menthol MEN MR and the impact it has on exercise capacity and performance. METHODS: Three databases were searched with articles screened according to the inclusion/exclusion criteria. Three-level meta-analyses were used to investigate the overall efficacy of MEN MR and the impact it has on exercise capacity and performance. Meta-regressions were then performed with 1) mean VO2peak, 2) MEN swilling duration; 3) the MEN concentration of MR solution, 4) the number of executed swills throughout a single experiment, 5) the use of flavoured sweetened, non-caloric, or non-flavoured neutral solutions as controls, 6) mean environmental temperature at the time of exercise tests, and 7) exercise type as fixed factors to evaluate their influence on the effects of MEN MR. RESULTS: Ten MEN MR studies included sufficient information pertaining to MEN MR and exercise performance and capacity. MR with MEN resulted in no significant change in capacity and performance (SMD = 0.12; 95% CI - 0.08, 0.31; p = 0.23, n = 1, tau21 < 0.0001, tau22 = < 0.0001, I2 = 0%). No significant influence was detected in meta-regressions for VO2peak, (estimate: 0.03; df = 8; 95% CI - 0.03, 0.09; p = 0.27), swilling duration (5 vs. 10 s: 0.00; df = 16; 95% CI - 0.41, 0.41; p = 1.0), MEN concentration (low [0.01%] vs. high [0.1%]: - 0.08; df = 15; 95% CI - 0.49, 0.32; p = 0.67), number of swills (estimate: 0.02; df = 13; 95% CI - 0.05, 0.09; p = 0.56), the use of flavoured sweetener or non-caloric as control (non-flavoured vs. flavoured: 0.12; df = 16; 95% CI - 0.30, 0.55; p = 0.55) or mean room temperature during exercise tests (estimate: 0.01; df = 16; 95% CI - 0.02, 0.04; p = 0.62). CONCLUSION: MEN MR did not significantly improve overall exercise capacity and performance, though those involved in endurance exercise may see benefits.

Iterative assessment of a sports rehydration beverage containing a novel amino acid formula on water uptake kinetics.

PURPOSE: Rapid gastric emptying and intestinal absorption of beverages is essential for rapid rehydration, and certain amino acids (AA) may augment fluid delivery. Three sugar-free beverages, containing differing AA concentrations (AA + PZ), were assessed for fluid absorption kinetics against commercial sugar-free (PZ, GZ) and carbohydrate-containing (GTQ) beverages. METHODS: Healthy individuals (n = 15-17 per study) completed three randomised trials. Three beverages (550-600 mL) were ingested in each study (Study 1: AA + PZ [17.51 g/L AA], PZ, GZ; Study 2: AA + PZ [6.96 g/L AA], PZ, GZ; Study 3: AA + PZ [3.48 g/L AA], PZ, GTQ), containing 3.000 g deuterium oxide (D2O). Blood samples were collected pre-, 2-min, 5-min, and every 5-min until 60-min post-ingestion to quantify maximal D2O enrichment (Cmax), time Cmax occurred (Tmax) and area under the curve (AUC). RESULTS: Study 1: AUC (AA + PZ: 15,184 ± 3532 δ‰ vs. VSMOW; PZ: 17,328 ± 3153 δ‰ vs. VSMOW; GZ: 17,749 ± 4204 δ‰ vs. VSMOW; P ≤ 0.006) and Tmax (P ≤ 0.005) were lower for AA + PZ vs. PZ/GZ. Study 2: D2O enrichment characteristics were not different amongst beverages (P ≥ 0.338). Study 3: Cmax (AA + PZ: 440 ± 94 δ‰ vs. VSMOW; PZ: 429 ± 83 δ‰ vs. VSMOW; GTQ: 398 ± 81 δ‰ vs. VSMOW) was greater (P = 0.046) for AA + PZ than GTQ, with no other differences (P ≥ 0.106). CONCLUSION: The addition of small amounts of AA (3.48 g/L) to a sugar-free beverage increased fluid delivery to the circulation compared to a carbohydrate-based beverage, but greater amounts (17.51 g/L) delayed delivery.

Perceived dehydration impairs endurance cycling performance in the heat in active males.

Dehydration of >3 % body mass impairs endurance performance irrespective of the individual's knowledge of their hydration status, but whether knowledge of hydration status influences performance at lower levels of dehydration is unknown. This study examined whether perception of hydration status influenced endurance performance. After familiarisation, nine active males (age 25 ± 2 y, V̇O2peak 52.5 ± 9.1 mL kg min-1) completed two randomised trials at 34 °C. Trials involved an intermittent exercise preload (8 × 10 min cycling/5 min rest), followed by a 15 min all-out cycling performance test. During the preload in both trials, water was ingested orally every 10 min (0.3 mL kg body mass-1), with additional water infused into the stomach via gastric feeding tube to produce dehydration of ∼1.5 % body mass pre-performance test. Participants were told intra-gastric infusion was manipulated to produce euhydration (0 % dehydration; Perceived-EUH) or dehydration (2 % dehydration; Perceived-DEH) pre-performance test, which was told to them pre-preload and confirmed after body mass measurement pre-performance test. Body mass loss during the preload (Perceived-EUH 1.6 ± 0.2 %, Perceived-DEH 1.7 ± 0.2 %; P = 0.459), heart rate, gastrointestinal temperature and RPE (P ≥ 0.110) were not different between trials. Thirst was greater at the end of the preload and performance test in Perceived-DEH (P ≤ 0.040). Work completed during the performance test was 5.6 ± 6.1 % lower in Perceived-DEH (187.4 ± 37.0 kJ vs. 176.9 ± 36.0 kJ; P = 0.038). These results suggest that at lower levels of dehydration (<2 % body mass), an individual's perception of their hydration status could impair their performance, as well as their thirst perception.

Hypohydration induced by prolonged cycling in the heat increases biomarkers of renal injury in males.

PURPOSE: Recent studies have shown that hypohydration can increase renal injury. However, the contribution of hypohydration to the extent of renal injury is often confounded by exercise induced muscle damage. Therefore, the aim of the present study was to investigate the effect of manipulating hydration status during moderate-intensity cycling in the heat on biomarkers of renal injury. METHODS: Following familiarisation, fourteen active males (age: 21 [20-22] y; BMI: 22.1 ± 1.9 kg/m2; V ˙ O2peak: 55 ± 9 mL/kg/min) completed two experimental trials, in a randomised cross-over design. Experimental trials consisted of up to 120 min of intermittent cycling (~ 50% Wpeak) in the heat (~ 35 °C, ~ 50% relative humidity). During exercise, subjects consumed either a water volume equal to 100% body mass losses (EU) or minimal water (HYP; 75-100 mL) to induce ~ 3% body mass loss. Blood and urine samples were collected at baseline, 30 min post-exercise and 24 h post-baseline, with an additional urine sample collected immediately post-exercise. RESULTS: Thirty minutes post-exercise, body mass and plasma volume were lower in HYP than EU (P < 0.001), whereas serum and urine osmolality (P < 0.001), osmolality-corrected urinary kidney injury molecule-1 concentrations (HYP: 2.74 [1.87-5.44] ng/mOsm, EU: 1.15 [0.84-2.37] ng/mOsm; P = 0.024), and percentage change in osmolality-corrected urinary neutrophil gelatinase-associated lipocalin concentrations (HYP: 61 [17-141] %, EU: 7.1 [- 4 to 24] %; P = 0.033) were greater in HYP than EU. CONCLUSION: Hypohydration produced by cycling in the heat increased renal tubular injury, compared to maintaining euhydration with water ingestion.

Influence of acute dietary nitrate supplementation timing on nitrate metabolism, central and peripheral blood pressure and exercise tolerance in young men.

PURPOSE: Dietary nitrate (NO3-) supplementation can lower systolic blood pressure (SBP) and improve exercise performance. Salivary flow rate (SFR) and pH are key determinants of oral NO3- reduction and purported to peak in the afternoon. We tested the hypotheses that NO3--rich beetroot juice (BR) would increase plasma [nitrite] ([NO2-]), lower SBP and improve exercise performance to a greater extent in the afternoon (AFT) compared to the morning (MORN) and evening (EVE). METHOD: Twelve males completed six experimental visits in a repeated-measures, crossover design. NO3--depleted beetroot juice (PL) or BR (~ 13 mmol NO3-) were ingested in the MORN, AFT and EVE. SFR and pH, salivary and plasma [NO3-] and [NO2-], brachial SBP and central SBP were measured pre and post supplementation. A severe-intensity exercise tolerance test was completed to determine cycling time to exhaustion (TTE). RESULTS: There were no between-condition differences in mean SFR or salivary pH. The elevation in plasma [NO2-] after BR ingestion was not different between BR-MORN, BR-AFT and BR-EVE. Brachial SBP was unchanged following BR supplementation in all conditions. Central SBP was reduced in BR-MORN (- 3 ± 4 mmHg), BR-AFT (- 4 ± 3 mmHg), and BR-EVE (- 2 ± 3 mmHg), with no differences between timepoints. TTE was not different between BR and PL at any timepoint. CONCLUSION: Acute BR supplementation was ineffective at improving TTE and brachial SBP and similarly effective at increasing plasma [NO2-] and lowering central SBP across the day, which may have implications for informing NO3- supplementation strategies.

A self-paced 15-minute cycling time trial is a reliable performance measure in recreationally active individuals.

Cycling time trial (TT) protocols have been shown to be reliable in trained cyclists, but their reproducibility in lesser-trained individuals is unknown. This study examined the reliability of a self-paced 15-minute cycling TT in recreationally active individuals. Twelve recreationally active males (age 27 ± 3 y; body mass 75.2 ± 8.9 kg; V˙O2peak = 51.10 ± 7.53 ml∙kg∙min-1) completed a V˙O2peak test and four experimental trials, separated by > 48 h. Experimental trials consisted of 10 min cycling at 60% Wmax, followed by a self-paced 15-min TT. Heart rate and work done were recorded every 5 min during the TT; and coefficient of variation (CV) was calculated. Work done was not different (P = 0.706) between trials (193.2 ± 45.3 kJ; 193.2 ± 43.5 kJ; 192.0 ± 42.3 kJ; 193.9 ± 42.8 kJ). Within participant CV ranged from 0.5-4.9% for the four TTs, with a mean CV of 2.1%. Mean CV decreased from 2.0% (range 0.1-5.0%) for the first two TTs to 1.7% (range 0.2-5.6%) for the second and third TTs, and further decreased to 1.0% (range 0.2-1.8%) for the third and fourth TTs. In conclusion, the use of a short-duration self-paced cycling TT in recreationally active individuals is a reliable performance measure.

Exercise-induced hypohydration impairs 3 km treadmill-running performance in temperate conditions.

Research assessing exercise-induced hypohydration on running performance in a temperate environment is scarce. Given the weight-bearing nature of running, the negative effects of hypohydration might be offset by the weight-loss associated with a negative fluid balance. Therefore, this study investigated the effect of exercise-induced hypohydration on running performance in temperate conditions. Seventeen intermittent games players (age 22 ± 1 y; VO2peak 52.5 ± 4.1 mL∙kg-1∙min-1) completed preliminary and familiarisation trials, and two experimental trials consisting of 12 blocks of 6 min of running (65% VO2peak; preload) with 1 min passive rest in-between, followed by a 3 km time trial (TT). During the preload, subjects consumed minimal fluid (60 mL) to induce hypohydration (HYP) or water to replace 95% sweat losses (1622 ± 343 mL; EUH). Body mass loss (EUH -0.5 ± 0.3%; HYP -2.2 ± 0.4%; P < 0.001), and other changes indicative of hypohydration, including increased serum osmolality, heart rate, thirst sensation, and decreased plasma volume (P ≤ 0.022), were apparent in HYP by the end of the preload. TT performance was ~6% slower in HYP (EUH 900 ± 87 s; HYP 955 ± 110 s; P < 0.001). Exercise-induced hypohydration of ~2% body mass impaired 3 km running TT performance in a temperate environment.

Cannabidiol Oil Ingested as Sublingual Drops or Within Gelatin Capsules Shows Similar Pharmacokinetic Profiles in Healthy Males.

Introduction: Cannabidiol (CBD) is a nonintoxicating phytocannabinoid used in clinical treatments and sold widely in consumer products. CBD products may be designed for sublingual or oral delivery, but it is unclear whether either is advantageous for CBD absorption. This study compared CBD pharmacokinetics after providing CBD oil as sublingual drops and within orally ingested gelatin capsules, at a dose relevant to consumer products. Materials and Methods: Eight males completed three conditions in a participant-blinded, randomized crossover design. Participants received the following combinations of placebo and CBD-containing (69 mg/mL) hemp oil in capsules and as sublingual drops: placebo capsules/placebo drops (Placebo), CBD capsules/placebo drops (CBD-Caps), and placebo capsules/CBD drops (CBD-Drops). Blood samples, blood pressure, and subjective scales were obtained/completed hourly for 6 h and at 24 h. Discussion: Plasma CBD concentrations were not different between CBD-Caps and CBD-Drops (interaction effect p=0.76). Peak CBD concentration (28.0±15.6 vs. 24.0±22.2 ng/mL), time of peak CBD concentration (4±1 vs. 4±2 h), and area under the concentration curve (45.3±20.3 vs. 41.8±23.3 ng/mL·6 h) were not different between conditions (p≥0.25). Cardiometabolic outcomes (plasma glucose/triacylglycerol, heart rate, blood pressure), liver function (plasma alanine aminotransferase/aspartate aminotransferase), kidney function (plasma creatinine), and subjective feelings/symptoms were not different between conditions (p≥0.07). Conclusions: Plasma CBD profiles were comparable between CBD-Caps and CBD-Drops, suggesting that there were not meaningful differences in routes of CBD absorption between conditions. This implies that CBD oil delivered sublingually is swallowed before oral mucosal CBD absorption occurs, which may have implications for research design, CBD product design, and consumer product choice.

The Effect of Specific Bioactive Collagen Peptides on Tendon Remodeling during 15 wk of Lower Body Resistance Training.

PURPOSE: Collagen peptide supplementation has been reported to enhance synthesis rates or growth in a range of musculoskeletal tissues and could enhance tendinous tissue adaptations to resistance training (RT). This double-blind placebo-controlled study aimed to determine if tendinous tissue adaptations, size (patellar tendon cross-sectional area (CSA) and vastus lateralis (VL) aponeurosis area), and mechanical properties (patellar tendon), after 15 wk of RT, could be augmented with collagen peptide (CP) versus placebo (PLA) supplementation. METHODS: Young healthy recreationally active men were randomized to consume either 15 g of CP ( n = 19) or PLA ( n = 20) once every day during a standardized program of lower-body RT (3 times a week). Measurements pre- and post-RT included patellar tendon CSA and VL aponeurosis area (via magnetic resonance imaging), and patellar tendon mechanical properties during isometric knee extension ramp contractions. RESULTS: No between-group differences were detected for any of the tendinous tissue adaptations to RT (ANOVA group-time, 0.365 ≤ P ≤ 0.877). There were within-group increases in VL aponeurosis area (CP, +10.0%; PLA, +9.4%), patellar tendon stiffness (CP, +17.3%; PLA, +20.9%) and Young's modulus (CP, +17.8%; PLA, +20.6%) in both groups (paired t -tests (all), P ≤ 0.007). There were also within-group decreases in patellar tendon elongation (CP, -10.8%; PLA, -9.6%) and strain (CP, -10.6%; PLA, -8.9%) in both groups (paired t -tests (all), P ≤ 0.006). Although no within-group changes in patellar tendon CSA (mean or regional) occurred for CP or PLA, a modest overall time effect ( n = 39) was observed for mean (+1.4%) and proximal region (+2.4%) patellar tendon CSA (ANOVA, 0.017 ≤ P ≤ 0.048). CONCLUSIONS: In conclusion, CP supplementation did not enhance RT-induced tendinous tissue remodeling (either size or mechanical properties) compared with PLA within a population of healthy young men.

A comparison of advertised versus actual cannabidiol (CBD) content of oils, aqueous tinctures, e-liquids and drinks purchased in the UK.

BACKGROUND: Cannabidiol (CBD)-containing products are sold widely in consumer stores, but concerns have been raised regarding their quality, with notable discrepancies between advertised and actual CBD content. Information is limited regarding how different types of CBD products may differ in their deviation from advertised CBD concentrations. Therefore, CBD concentrations were quantified and compared in aqueous tinctures, oils, e-liquids and drinks. METHODS: Products (13 aqueous tinctures, 29 oils, 10 e-liquids and 11 drinks) were purchased online in the UK. CBD concentrations were quantified in aqueous tinctures, oils and e-liquids via high performance liquid chromatography (HPLC), and in drinks via gas chromatograhy-mass spectrometry (GC-MS). RESULTS: Measured concentrations fell -25.7 ± 17.3, -6.1 ± 7.8, -6.9 ± 4.6 and - 0.03 ± 0.06 mg/mL below advertised concentrations for aqueous tinctures, oils, e-liquids and drinks, respectively (medians ± interquartile ranges; p < .05). Oils deviated relatively less (-19.0 ± 14.5%) from advertised concentrations than e-liquids (-29.2 ± 10.2%), aqueous tinctures (-51.4 ± 41.4%) and drinks (-65.6 ± 36.5%; p < .01), whilst e-liquids deviated less than aqueous tinctures and drinks (p < .05), and deviation was not different between aqueous tinctures and drinks (p = .19). Only 5/63 (8%) products had measured concentrations within 10% of advertised concentrations. DISCUSSION: Similarly to previous studies, few products had measured CBD concentrations within 10% of advertised concentrations, with most falling below advertised concentrations. All individual product types deviated from advertised concentrations, with oils deviating least. These findings may be indicative of poor manufacturing standards, or that CBD undergoes degradation in consumer products. This reinforces concerns over quality of CBD-containing consumer products and may highlight the need for improved regulation of such products.

High-impact jumping mitigates the short-term effects of low energy availability on bone resorption but not formation in regularly menstruating females: A randomized control trial.

Low energy availability (LEA) is prevalent in active individuals and negatively impacts bone turnover in young females. High-impact exercise can promote bone health in an energy efficient manner and may benefit bone during periods of LEA. Nineteen regularly menstruating females (aged 18-31 years) participated in two three-day conditions providing 15 (LEA) and 45 kcals kg fat-free mass-1 day-1 (BAL) of energy availability, each beginning 3 ± 1 days following the self-reported onset of menses. Participants either did (LEA+J, n = 10) or did not (LEA, n = 9) perform 20 high-impact jumps twice per day during LEA, with P1NP, ß-CTx (circulating biomarkers of bone formation and resorption, respectively) and other markers of LEA measured pre and post in a resting and fasted state. Data are presented as estimated marginal mean ± 95% CI. P1NP was significantly reduced in LEA (71.8 ± 6.1-60.4 ± 6.2 ng mL-1 , p < 0.001, d = 2.36) and LEA+J (93.9 ± 13.4-85.2 ± 12.3 ng mL-1 , p < 0.001, d = 1.66), and these effects were not significantly different (time by condition interaction: p = 0.269). ß-CTx was significantly increased in LEA (0.39 ± 0.09-0.46 ± 0.10 ng mL-1 , p = 0.002, d = 1.11) but not in LEA+J (0.65 ± 0.08-0.65 ± 0.08 ng mL-1 , p > 0.999, d = 0.19), and these effects were significantly different (time by condition interaction: p = 0.007). Morning basal bone formation rate is reduced following 3 days LEA, induced via dietary restriction, with or without high-impact jumping in regularly menstruating young females. However, high-impact jumping can prevent an increase in morning basal bone resorption rate and may benefit long-term bone health in individuals repeatedly exposed to such bouts.

Ad-libitum fluid intake was insufficient to achieve euhydration 20 h after intermittent running in male team sports athletes.

This study documented 20 h rehydration from intermittent running while concealing the primary outcome of rehydration from subjects. Twenty-eight male team sports athletes (age 25 ± 3 y; predicted V̇O2max 54 ± 3 mL kg-1 min-1) were pair-matched to exercise (EX) or rest (REST) groups. To determine hydration status, body mass, urine and blood samples were collected at 08:00, pre-intervention (09:30), post-intervention (12:00), 3 h post-intervention and 08:00 the following morning (20 h). The intervention was 110 min intermittent running (EX) or seated rest (REST), with ad-libitum fluid provided in both. Subjects completed a weighed diet record and collected all urine for the 24 h. Changes typical of hypohydration were apparent in EX following the intervention period (body mass: EX -2.0 ± 0.5%; REST -0.2 ± 0.3%; serum osmolality: EX 293 ± 4 mOsm∙kgH2O-1; REST 287 ± 6 mOsm∙kgH2O-1; P ≤ 0.022). Fluid intake during the intervention period (EX 704 ± 286 mL, REST 343 ± 230 mL) and fluid intake within the first 3 h post-intervention (EX 1081 ± 460 mL, REST 662 ± 230 mL) were greater (P ≤ 0.004), and 24 h urine volume lower (EX 1697 ± 824 mL, REST 2370 ± 842 mL; P = 0.039) in EX. Compared to baseline, body mass remained lower (-0.6 ± 0.5%; P = 0.030) and urine osmolality elevated (20 h: 844 ± 197 mOsm∙kgH2O-1, 08:00: 698 ± 200 mOsm∙kgH2O-1; P = 0.004) at 20 h in EX. When games players drank fluid ad-libitum during exercise and post-exercise in free-living conditions, a small degree of hypohydration remained 20 h post-exercise.

The influence of physical activity on neural responses to visual food cues in humans: A systematic review of functional magnetic resonance imaging studies.

This systematic review examined whether neural responses to visual food-cues measured by functional magnetic resonance imaging (fMRI) are influenced by physical activity. Seven databases were searched up to February 2023 for human studies evaluating visual food-cue reactivity using fMRI alongside an assessment of habitual physical activity or structured exercise exposure. Eight studies (1 exercise training, 4 acute crossover, 3 cross-sectional) were included in a qualitative synthesis. Structured acute and chronic exercise appear to lower food-cue reactivity in several brain regions, including the insula, hippocampus, orbitofrontal cortex (OFC), postcentral gyrus and putamen, particularly when viewing high-energy-density food cues. Exercise, at least acutely, may enhance appeal of low-energy-density food-cues. Cross-sectional studies show higher self-reported physical activity is associated with lower reactivity to food-cues particularly of high-energy-density in the insula, OFC, postcentral gyrus and precuneus. This review shows that physical activity may influence brain food-cue reactivity in motivational, emotional, and reward-related processing regions, possibly indicative of a hedonic appetite-suppressing effect. Conclusions should be drawn cautiously given considerable methodological variability exists across limited evidence.

Post-exercise rehydration: Comparing the efficacy of three commercial oral rehydration solutions.

Introduction: This study compared the efficacy of three commercial oral rehydration solutions (ORS) for restoring fluid and electrolyte balance, after exercise-induced dehydration. Method: Healthy, active participants (N = 20; ♀ = 3; age ∼27 y, V˙O2peak ∼52 ml/kg/min) completed three randomised, counterbalanced trials whereby intermittent exercise in the heat (∼36°C, ∼50% humidity) induced ∼2.5% dehydration. Subsequently, participants rehydrated (125% fluid loss in four equal aliquots at 0, 1, 2, 3 h) with a glucose-based (G-ORS), sugar-free (Z-ORS) or amino acid-based sugar-free (AA-ORS) ORS of varying electrolyte composition. Urine output was measured hourly and capillary blood samples collected pre-exercise, 0, 2 and 5 h post-exercise. Sodium, potassium, and chloride concentrations in urine, sweat, and blood were determined. Results: Net fluid balance peaked at 4 h and was greater in AA-ORS (141 ± 155 ml) and G-ORS (101 ± 195 ml) than Z-ORS (-47 ± 208 ml; P ≤ 0.010). Only AA-ORS achieved positive sodium and chloride balance post-exercise, which were greater for AA-ORS than G-ORS and Z-ORS (P ≤ 0.006), as well as for G-ORS than Z-ORS (P ≤ 0.007) from 1 to 5 h. Conclusion: when provided in a volume equivalent to 125% of exercise-induced fluid loss, AA-ORS produced comparable/superior fluid balance and superior sodium/chloride balance responses to popular glucose-based and sugar-free ORS.