Diurnal variation and reliability of the urine lactate concentration after maximal exercise

Effects of Different Caffeine Dosages on Maximal Physical Performance and Potential Side Effects in Low-Consumer Female Athletes: Morning vs. Evening Administration

While previous studies have explored a range of factors governing the optimal use of caffeine (CAF) in athletes, limited research has explored how time of day (TOD) affects the ergogenic effects of various CAF dosages on physical performance. This study aimed to increase knowledge about how different recommended CAF doses (3 mg/kg vs. 6 mg/kg) ingested at different TODs affected maximal high-intensity physical performance and the perception of potential side effects in female athletes. In this double-blind, randomized, and counterbalanced study, 15 low CAF consumer athletes (aged 18.3 ± 0.5 y) underwent six trials, including three testing conditions assessed across two TODs: one in the morning (08:00 a.m.) and one in the evening (06:00 p.m.). During each condition, the participants ingested either a placebo, 3 mg/kg CAF (CAF (3 mg)), or 6 mg/kg CAF (CAF (6 mg)) capsules 60 min before each test with an in-between washout period of at least 72 h. In each trial, the participants performed a countermovement jumps test (CMJ), a modified agility t test (MATT), a repeated sprint ability (RSA), a rating of perceived exertion (RPE), and finally, a CAF side effects questionnaire. Our findings indicate the absence of an ergogenic effect on CMJ, MAT, and RSA performance in the evening after administering CAF (3 mg) or CAF (6 mg) compared to a placebo. Likewise, when CAF was ingested in the morning, there was an improvement in these performances with both CAF (3 mg) and CAF (6 mg), with greater improvement observed after CAF (6 mg). Additionally, neither the CAF dosage nor the TOD had a significant effect on the RPE. The occurrence of side effects increased significantly after the evening ingestion of CAF, particularly with a moderate dose of CAF (6 mg). Our findings indicate that the effectiveness of CAF depends on the TOD and CAF dosage. When ingested in the morning, a moderate dose of CAF (6 mg), rather than CAF (3 mg), is more effective in improving short-term physical performance without affecting CAF side effects in female athletes. Nevertheless, when ingested in the evening, neither dose was sufficient to enhance short-term physical performance, and both dosages increased the incidence of CAF side effects, particularly at a moderate dose.

Ramadan Fasting and Short-Term Maximal Physical Performance: Searching for Optimal Timing of the Last Meal "Suhoor" in Female Pre-University Handball Players

Aiming to identify the ideal suhoor timing for maintaining optimal physical performance and health indicators during Ramadan intermittent fasting, the present study compares the effects of early vs. late Suhoor on short-term high-intensity physical exercise while controlling the body mass index (BMI) oral temperature (OT), dietary intake, and sleep patterns. In a randomized design, 19 female pre-university handball players (age: 16.8 ± 0.4 y; height: 1.70 ± 0.9 m; and body mass: 61.5 ± 6.9 kg) underwent two test sessions (at 08:00 a.m. and 05:00 p.m.) at four different conditions: ten days prior to Ramadan (R - 10), the final ten days of Ramadan (R) including both Early Suhoor R(ES) and Late Suhoor R(LS) conditions, and the ten days immediately following Ramadan (R + 10). A recovery period of at least 48 h has been set between successive test sessions at each period. Outcome measures included the Countermovement Jumps Test (CMJ), Modified Agility t-Test (MATT), Repeated Sprint Ability (RSA), and Rating of Perceived Exertion (RPE). The Pittsburgh Sleep Quality Index (PSQI), OT, BMI, and daily diary intake were assessed across the three periods. The total scores of PSQI decreased significantly during R and R + 10 compared to R - 10. When performed in the afternoon, CMJ, MATT, and RSA performance decreased significantly at R(ES) and R(LS) conditions compared to R - 10. However, these performances decreased only after R(ES) when performed in the morning. Furthermore, performances were lower during R(ES) compared to R(LS) in the afternoon for all tests and the morning for MATT and RSA tests. These findings support prior research showing a deterioration of physical performance during Ramadan fasting and indicate a more pronounced impact following early Suhoor condition. Therefore, consuming a late suhoor, closer to pre-dawn time, could be suggested as an effective strategy to minimize physical performance decline during short-term high-intensity exercise.

Pre-Exercise Caffeine Intake Attenuates the Negative Effects of Ramadan Fasting on Several Aspects of High-Intensity Short-Term Maximal Performances in Adolescent Female Handball Players

The aim of this investigation was to determine whether, after Ramadan, pre-exercise caffeine intake can reduce any possible negative effects of this month on short-term maximal performances in young female handball players. A randomized study involved thirteen young female handball players. Participants performed a squat jump (SJ), Illinois agility test (AG), and 5 m run shuttles test (total (TD) and peak (PD) distances) at 08:00 AM and 06:00 PM on three different occasions: one week before Ramadan (Pre-R), the last week of Ramadan (R), and the week after Ramadan (Post-R). A placebo (Pla) or caffeine (Caff) (6 mg·kg-1) was administered 60 min before exercise test sessions at two distinct times of day (08:00 AM and 06:00 PM) during the two periods: Pre and Post-R. The PSQI and dietary intake were assessed during all testing periods. The results revealed that Pre-R, (SJ, AG, TD, and PD) test performances were greater in the evening (PM) than in the morning (AM) (all p < 0.001). However, compared with Pre-R, PM performances declined significantly during R (all p < 0.001) and Post-R (p < 0.05, p < 0.01, p < 0.01 and p < 0.001, respectively). In addition, Pre-R, AM Caff produced moderate significant improvements compared with AM Pla, with small-to-no beneficial effects observed with PM Caff in SJ (4.8% vs. 1%), AG (1.8% vs. 0.8%), TD (2.8% vs. 0.3%), and PD (6% vs. 0.9%). Nevertheless, Caff produced moderate ergogenic effects during both AM and PM sessions during Post-R in SJ (4.4% vs. 2.4%), AG (1.7% vs. 1.5%), TD (2.9% vs. 1.3%), and PD (5.8% vs. 3%) with values approaching those of Pre-R Pla within the same time of day (p > 0.05, p > 0.05, p < 0.05, and p < 0.05, respectively). In summary, pre-exercise Caff intake with a dose equivalent to 6 mg·kg-1 reduced the negative effects of Ramadan fasting in several aspects of short-term maximal performances in young female handball players at both times of the day.

Electrodeposited copper nanoparticles for creatinine detection via the in situ formation of copper-creatinine complexes

Creatinine is an important biomarker of kidney diseases. In this work, a fast and facile electrochemical sensor was developed for creatinine detection based on the use of copper nanoparticle-modified screen-printed electrodes. The copper electrodes were prepared by simple electrodeposition of Cu²⁺ (aq). The electrochemically inactive creatinine was detected reductively via the in situ formation of copper-creatinine complexes. Two linear detection ranges, 0.28-3.0 mM and 3.0-20.0 mM, were achieved using differential pulse voltammetry, with the sensitivities of 0.824 ± 0.053 μA mM^-1 and 0.132 ± 0.003 μA mM^-1, respectively. The limit of detection was determined to be 0.084 mM. The sensor was validated in synthetic urine samples to yield 99.3% recovery (%RSD = 2.8), demonstrating high tolerance to possible interfering species. Finally, the stability of creatinine and its degradation kinetics at different temperatures were evaluated using our developed sensor. The loss of creatinine was found to be a first-order reaction with the activation energy of 64.7 kJ mol^-1.

Effects of serial and acute enteric-coated sodium bicarbonate supplementation on anaerobic performance, physiological profile, and metabolomics in healthy young men

Background

Previous studies have reported that sodium bicarbonate ingestion may enhance high-intensity exercise performance and cause severe gastrointestinal distress. However, enteric-coated sodium bicarbonate may reduce gastrointestinal symptoms of sodium bicarbonate after oral administration. This remains to be confirmed. This study aimed to verify the effects of serial and acute enteric-coated sodium bicarbonate supplementation on anaerobic performance, physiological profile, and metabolomics in healthy young men.

Methods

Healthy young males (n = 12) ingested 0.2 g/kg body mass of enteric-coated sodium bicarbonate (ES) in serial enteric-coated sodium bicarbonate (SES, continuous ES supplementation for 5 days) and acute enteric-coated sodium bicarbonate (AES, acute ES supplementation before exercise) or a placebo (PL) in a randomized crossover design. After each supplement protocol, the participants completed four Wingate anaerobic tests (WAT). The first three Wingate tests (testing anaerobic capacity) were performed with a 5-min passive recovery between each. After the third Wingate test, participants were required to complete a 50-min recovery followed by a fourth WAT test (testing the recovery of anaerobic capacity after 50-min intervals). Blood lactate (BLA), heart rate (HR), and ratings of perceived exertion (RPE) were measured in all conditions during the test, as was the subjective gastrointestinal–symptoms assessment questionnaire (GSAQ). Mean power (MP) and peak power (PP) were recorded after four WATs. Urine samples were collected before the test and 50 min after the 3rd WAT.

Results

Serial enteric-coated sodium bicarbonate supplementation improved anaerobic capacity in the third bout of WATs, as observed based on an increase in mean power (SES vs. PL (613 ± 57 vs. 542 ± 64 W), P = 0.024) and peak power (SES vs. PL (1,071 ± 149 vs. 905 ± 150 W), P = 0.016). Acute ES supplementation did not affect anaerobic capacity. The occurrence of gastrointestinal symptoms after enteric-coated sodium bicarbonate supplementation was minimal and no difference compared to placebo in the current study. In particular, serial enteric-coated sodium bicarbonate supplementation had no gastrointestinal side effects before the test. The AES and SES groups had a trivial effect on blood lactate compared to the PLA group. There was no significant difference in HR and RPE among the three groups. Based on targeted metabolomics analysis, the 50 min after the third WAT, the levels of lactate (P &lt; 0.001), L-Malic acid (P &lt; 0.05), and oxaloacetate (P &lt; 0.05) were significantly higher in the SES group than in the PL group. Compared with the AES group, the levels of lactate and fumarate in the SES group were significantly increased (P &lt; 0.05).

Conclusions

Our study indicates that serial enteric-coated sodium bicarbonate supplementation positively improves anaerobic performance among healthy young men. However, acute ingestion of enteric-coated sodium bicarbonate did not improve anaerobic exercise performance. Either with serial or acute supplementation doses, enteric-coated sodium bicarbonate produced fewer gastrointestinal symptoms and no difference compared to placebo, especially with no gastrointestinal side effects after serial supplementation. Serial and acute supplementation of enteric-coated sodium bicarbonate might tend to promote lactate clearance. Furthermore, serial enteric-coated sodium bicarbonate ingestion may cause changes in the metabolism of lactate, L-Malic acid, oxaloacetate, and fumarate 50 min after exercise, which presumably may promote the tricarboxylic acid cycle and lactate clearance.

Bout duration in high-intensity interval exercise modifies hematologic, metabolic and antioxidant responses

Objective

This study compared hematologic, metabolic and antioxidant responses between three high-intensity interval exercise (HIIE) trials of different bout duration and a continuous exercise trial (CON), all with equal average intensity, total work, and duration.

Methods

Eleven healthy young males performed four trials involving 20 min of cycling, either continuously (49% of power at VO₂max, PPO), or intermittently with 48 10-s bouts (HIIE10), 16 30-s bouts (HIIE30) or 8 60-s bouts (HIIE60) at 100% PPO, with a 1:1.5 work-to-recovery ratio at 15% PPO. Venous blood was obtained before, immediately after, and 1 h post-exercise to evaluate hematologic, metabolic and antioxidant responses. Blood lactate concentration was measured in capillary blood during exercise, while urine lactate was measured before and 1 h post-exercise.

Results

Post-exercise leukocyte count (mean ± SD; 9.7 ± 2.8 k μL^-1), uric acid concentration (0.35 ± 0.10 mmol L^-1), glucose concentration (6.56 ± 1.44 mmol L^-1), and plasma volume change (-13.5 ± 4.4%) were greater in HIIE60 compared to all other trials (p < 0.05). One-hour post-exercise, lymphocytes decreased below pre-exercise values in all HIIE trials, and uric acid increased in the HIIE60 trial (p < 0.05). Urine lactate concentration 1 h post-exercise increased compared to pre-exercise only in HIIE60 (19-fold, p < 0.001), and this was related with the higher blood lactate concentration during exercise in that trial.

Conclusions

These findings highlight the importance of bout duration, given that shorter bouts of HIIE (30 s or 10 s) induce lower blood cell perturbations, metabolic stress, and antioxidant responses compared to the commonly used 1-min bouts, despite equal total work, duration, and work-to-recovery ratio.

Lonicera caerulea Berry Polyphenols Extract Alleviates Exercise Fatigue in Mice by Reducing Oxidative Stress, Inflammation, Skeletal Muscle Cell Apoptosis, and by Increasing Cell Proliferation

Exercise fatigue can exert deleterious effects on the body. This study evaluated the effects and mechanisms by which Lonicera caerulea berry polyphenols extract (LCBP) improved the treadmill endurance of mice. Comparison was performed between the effects at 25°C and low temperatures (-5°C). Energy storage, product metabolism, and other biochemical indices were determined using vitamin C (VC) as a positive control. Co-immunoprecipitation was performed to detect the interaction between different proteins. Dietary supplementation with LCBP significantly prolonged the exhaustion time during treadmill exercise by 20.4% (25 °C) and 27.4% (-5 °C). LCBP significantly regulated the expression of antioxidant and inflammatory proteins, Bcl-2 /Bax apoptosis proteins, and the PKCα -NOx2 / Nox4 pathway proteins, and activated the expression of AMPK-PGC1α -NRF1-TFAM proteins in skeletal muscle mitochondria. The gene and protein expression of miRNA-133a/IGF-1/PI3K/Akt/mTOR in skeletal muscle cells was also activated. Molecular docking confirmed that the main components of LCBP such as cyanidin-3-glucoside, catechin, and chlorogenic acid, have strong binding affinity toward AMPKα. LCBP alleviates exercise fatigue in mice by reducing oxidative stress, inflammation, and apoptosis of skeletal muscle cells, enhances mitochondrial biosynthesis and cell proliferation, reduces fatigue, and enhances performance. These effects are also significant in a low-temperature environment (Graphical Abstract). Consequently, these results provide novel insights into the anti- fatigue roles of LCBP in exercise fatigue.

Daily variation in performance measures related to anaerobic power and capacity: A systematic review

Numerous functional measures related to anaerobic performance display daily variation. The diversity of tests and protocols used to assess anaerobic performance related to diurnal effects and the lack of a standardized approach have hindered agreement in the literature. Therefore, the aim of the present study was to investigate and systematically review the evidence relating to time-of-day differences in anaerobic performance measures. The entire content of PubMed (MEDLINE), Scopus, SPORTDiscus® (via EBSCOhost) and Web of Science and multiple electronic libraries were searched. Only experimental research studies conducted in male adult participants aged ≥ 18 yrs before May 2021 were included. Studies assessing tests related to anaerobic capacity or anaerobic power between a minimum of two time-points during the day (morning vs evening) were deemed eligible. The primary search revealed that a total of 55 out of 145 articles were considered eligible and subsequently included. Thirty-nine studies assessed anaerobic power and twenty-five anaerobic capacity using different modes of exercise and test protocols. Forty-eight studies found several of their performance variables to display time-of-day effects, with higher values in the evening than the morning, while seven studies did not find any time-of-day significance in any variables which were assessed. The magnitude of difference is dependent on the modality and the exercise protocol used. Performance measures for anaerobic power found jump tests displayed 2.7 to 12.3% differences, force velocity tests ~8% differences, sprint tests 2.7 to 11.3% differences and 5-m multiple shuttle run tests 3.7 to 13.1% differences in favour of the evening. Performance measures for anaerobic capacity found Wingate test to display 1.8 to 11.7% differences and repeated sprint tests to display 3.4 to 10.2% differences. The only test not to display time-of-day differences was the running based anaerobic sprint test (RAST). Time-of-day variations in anaerobic performance has previously been partially explained by higher core-body and/or muscle temperature and better muscle contractile properties in the afternoon, although recent findings suggest that differences in methodology, motivation/arousal, habitual training times and chronotypes could provide additional explanations. There is a clear demand for a rigorous, standardised approach to be adopted by future investigations which control factors that specifically relate to investigations of time-of-day.

Relevance of a Sprint Interval Swim Training Set to the 100-Meter Freestyle Event Based on Blood Lactate and Kinematic Variables

Sprint interval training (SIT) sets are commonly used by coaches in the training routine of swimmers competing in short-distance events; however, data regarding their relevance to competitive events are scarce. The aim of this study was to examine whether performance variables differed or correlated between a 4 × 50-m maximal swimming set (with a work-to-rest ratio of 1:4) and the 100-m freestyle event. Eleven male and 16 female competitive swimmers aged 16.1 ± 1.1 years participated in the study. All swimmers trained at least six times a week and had training experience of more than 4 years. They completed the two freestyle tests on different days, in random and counterbalanced order. In each test, speed, blood lactate, stroke rate (SR), and stroke index (SI) were measured. Speed, blood lactate, and SR were higher at the 4 × 50 m compared to the 100 m and were positively correlated between tests (p < 0.001). The SI did not differ significantly, but was positively correlated between tests. Males were faster and had a higher SI than females, but genders did not differ in lactate. Since performance variables were better in the SIT set and correlated with those in the 100-m bout, we suggest that the 4 × 50-m set can be used to improve performance in the 100-m freestyle event. Moreover, this set can help coaches identify which swimmers will swim fastest in the event.

Supplementation of nano-bubble curcumin extract improves gut microbiota composition and exercise performance in mice

BACKGROUND

In a previous study, we evaluated the potential beneficial effect of nano-bubble curcumin extract (NCE) in reducing exercise-related injuries and improving performance.

METHODS

In this study, we seek to investigate changes in the gut microbiota composition upon NCE supplementation in relation to health and exercise performance. Male ICR mice were divided into 3 groups (n = 8 per group) and orally administered NCE once daily for six weeks at 0 (vehicle), 3.075 (NCE-1X) and 15.375 g kg^-1 day^-1 (NCE-5X). The gut microbiota from the mice was analyzed using 16S rRNA gene sequencing.

RESULTS

NCE-5X did not appear to obviously cluster with the vehicle group, although NCE-5X groups showed an increased Firmicutes/Bacteroidetes ratio compared with the vehicle group. In addition, anti-fatigue activity and exercise performance were evaluated by investigating the exhaustive swimming time, forelimb grip strength and serum levels of lactate, ammonia, glucose, blood urea nitrogen (BUN), creatine kinase (CK) and lactate dehydrogenase (LDH) after swimming. The NCE-1X and NCE-5X groups showed a significantly longer exhaustive swimming time and higher relative forelimb grip strength than the vehicle group. Tissue glycogen content, an important energy source for exercise, increased significantly with NCE supplementation.

CONCLUSION

Taken together, our results indicate that NCE supplementation alters the gut microbiota composition and aids in overcoming physical fatigue. Curcumin may be acting on the gut microbiome to modulate the gut system towards improving exercise performance.

Daily, weekly and annual patterns in children's accidental sport injuries

Details of serious injuries to children ≤16 yrs. of age that necessitated urgent surgical intervention by the Department of Pediatric Surgery of the University Hospital of Lausanne, Switzerland were recorded into a database registry. Some 15 110 entries listed the precise time of injury, and 3114 (20.6%) of these resulted from participating in sport-associated activities. Time-of-day, day-of-week and month-of-year differences in the total number of children's accidental sport injuries (CASI) were validated. Time-of-day patterns were substantiated for "All Sports", for both boys and girls 5-16 yrs. of age, with more boys than girls experiencing incidents at almost every clock hour. Moreover, they were substantiated for this age group for each of the six different considered individual and team CASI categories - Physical Exercises at School; Bicycle Riding; Roller Skating and Skateboarding; Snow Skiing, Sledding, and Tobogganing; Soccer; and Basketball - for which sample sizes were sufficiently large (n > 230) to perform statistical assessment by ANOVA, t-test and/or cosinor analyses. CASI happened primarily between 06:00 and 17:00 h and rarely evening or overnight. Features - specific clock-time and number of peaks and troughs - of the CASI daily curve pattern of the individual six sport categories differed somewhat; nonetheless, excess or greatest number of CASI typically happened between 12:00 and 14:00 h, even when summertime and other scheduled school and family vacation periods were taken into account. Time-of-day and day-of-week patterns in the boy/girl sex ratio were also validated, with midday and Friday/Saturday peaks, respectively. We hypothesize the prominent 24 h patterns of CASI of 5-16 yr. olds, in particular, are representative of a combination of several determinants. These include exogenous periodic and cyclic environmental and sociocultural phenomena, genetic sex-related traits, plus endogenous circadian cognitive and physiologic rhythms, with the common midday injury excess of many sport categories, at least in part, the consequence of the well-documented midday dip in attention and vigilance of children.