Short-duration High-intensity Exercise Research Articles

The kinetics of cardiac troponin T release during and after 1- and 6-h maximal cycling trials

ObjectivesIn this study, the effects of short-duration high-intensity exercise and long-duration exercise on high-sensitivity cardiac troponin T (hs-cTnT) levels were compared. MethodsTwelve male amateur cyclists performed 1- and 6-h cycling trials. In both exercise trials, hs-cTnT was assessed at rest, immediately postexercise and at 1, 3, 6, 12, and 24 h postexercise. Additionally, hs-cTnT levels were assessed every hour during the 6-h trial. ResultsExercise resulted in an increase in hs-cTnT levels in all subjects. Circulating hs-cTnT levels increased in both exercise trials (p < 0.001), with higher peak values occurring after the 1-h trial compared with those of the 6-h trial (p = 0.023). The upper reference limit (URL) exceeded 83 % of the participants in the 1-h trial and 42 % of the participants in the 6-h trial. There was substantial individual variability in peak hs-cTnT in both trials. Values of hs-cTnT were greater after exercise than during exercise for the 6-h trial. For both exercise trials, the maximum postexercise hs-cTnT values correlated with the %HRMAX (r = 0.906 for the 1-h trial, r = 0.735 for the 6-h trial). For the 1-h trial, the maximum postexercise hs-cTnT values were observed at 3 h in all subjects. No significant difference in the hs-cTnT values was observed for the 6-h trial during the first 12 h postexercise. ConclusionsOur results demonstrated greater hs-cTnT levels in young male participants after a 1-h cycling trial than after a 6-h cycling trial, despite a substantially greater energy expenditure and total external work completed in the 6-h trial. Postexercise hs-cTnT values are associated with relative exercise intensity.

Effects of 3days of citrulline malate supplementation on short-duration repeated sprint running performance in male team sport athletes.

Citrulline malate (CM) is purported to be an ergogenic aid during various types of exercise performance. However, the effects of CM on repeated sprint performance (RSP) are under-explored. In a placebo-controlled, double-blind, counterbalanced cross-over design, male university-level team sport athletes (n=13) performed two familiarization trials, after which CM or placebo (PLA) (8×1g tablets each day) were taken on the 2days prior to, and with breakfast on the morning of, each main experimental trial. The main experimental trials employed a RSP protocol consisting of 10 repetitions of 40m maximal shuttle run test (MST) with a 30s interval between the start of each sprint. Sprint times and heart rate were recorded throughout the MST, and blood lactate concentrations were measured before, immediately after, and 5min after completing the MST. CM resulted in better RSP compared to PLA, as indicated by a lower sprint performance decrement (Sdec: CM, 4.68%±1.82% vs. PLA, 6.10%±1.83%; p=0.03; ES=0.77), which was possibly influenced by the fastest sprint time being faster in CM (CM, 8.16±0.34s vs. PLA, 8.29±0.39s; p=0.011; ES=0.34). There were no differences between CM and PLA in average sprint time (p=0.54), slowest sprint time (p=0.48), blood lactate concentrations (p=0.73) or heart rate (p=0.18), nor was there a condition×time interaction effect across the 10 sprints (p=0.166). Three days of CM supplementation (8g daily) attenuated the sprint performance decrement during short-duration high-intensity exercise in the form of running RSP in male university-level team sport athletes.

A111: Relationship Between Physical Activity and Mental Toughness

Purpose: Physical activity has favorable impacts on exercisers' stress levels, psychological distress and anxiety, emotional regulation, and mental wellness. In recent years, the global outbreak of COVID-19 has subtly altered college students' lifestyles. Studies have shown that the physical and mental health of students has deteriorated dramatically, which is alarming. Mental toughness refers to the ability to adapt well in the face of major pressures, setbacks, and adversity in life. The purpose of the present study was to examine variations in mental toughness depending on the intensity, length, and frequency of physical activity. Methods: A total of 3,120 Chinese college students participated in this study. In the spring semester of 2022, participants were given the demographic questionnaire, the Physical Activity Rating Scale (PARS-3), and the Chinese version of the Mental Resilience Scale (CD-RISC). 3049 students completed the survey. Independent sample t test, one-way analysis of variance (ANOVA), correlation analysis, and regression analysis were performed using SPSS 25.0 statistical software. Results: The physical activity level differed significantly across sex (t = 14.37, p &lt; 0.001), grade (F=3.72, p &lt; 0.05), and monthly living expenses (F = 5.70, p &lt; 0.001). The mental toughness had significant differences across sex (t = 4.55, p &lt; 0.001), grade (F = 3.35, p &lt; 0.05), and monthly living expenses (F = 5.41, p &lt; 0.001). There were significant differences in mental toughness across different levels of physical activity intensity (F = 39.28, p &lt; 0.001), different length of physical activity (F = 33.35, p &lt; 0.001), different frequency of physical activity (F = 30.14, p &lt; 0.001), and different levels of physical activity (F = 91.55, p &lt; 0.001). Physical activity was significantly and positively correlated with mental toughness (r = 0.26, p &lt; 0.01). Conclusion: Male students exhibited significantly higher levels of physical activity than their female counterparts, and freshmen demonstrated greater physical activity than students in other grades. Additionally, the amount of physical activity among college students was influenced by their monthly living expenses. The mental toughness score of male students was notably higher than that of female students, with freshmen scoring significantly higher than students in other grades. In comparison to other levels of physical activity, engaging in a high quantity of exercise, high-intensity short-duration exercise, more than 60 minutes of activity time, and a daily activity frequency had the most pronounced impact on enhancing mental toughness. Moreover, there was a positive correlation between physical activity and mental toughness.

Sodium Bicarbonate Ingestion in a Fasted State Improves 16.1-km Cycling Time-Trial Performance.

The use of sodium bicarbonate (SB) as a preexercise ergogenic aid has been extensively studied in short-duration high-intensity exercise. Very few studies have considered the effects of SB ingestion before prolonged high-intensity exercise. The aim of the present study was to determine the effects of a 0.3 g·kg -1 body mass dose of SB ingested before the start of a 16.1-km cycling time trial in cyclists. Ten trained male cyclists (age, 31.1 ± 9 yr; height, 1.84 ± 0.05 m; body mass, 82.8 ± 8.5 kg; and V̇O 2peak , 60.4 ± 3.1 mL·kg -1 ·min -1 ) completed this study. Participants ingested 0.3 g·kg -1 in gelatine (SB-G) and enteric capsules (SB-E) 1 wk apart to determine individualized time-to-peak alkalosis for each ingestion form. Using a randomized crossover design, participants then performed simulated 16.1-km time trials after ingestion of SB-G, SB-E, or a placebo. There were significant differences in performance between the SB and placebo ingestion strategies ( f = 5.50, P = 0.014, p η2 = 0.38). Performance time was significantly improved by SB ingestion (mean improvement: 34.4 ± 42.6 s ( P = 0.031) and 40.4 ± 45.5 s ( P = 0.020) for SB-G and SB-E, respectively) compared with the placebo. Gastrointestinal symptoms were lower after SB-E compared with SB-G (36.3 ± 4.5 vs 5.6 ± 3.1 AU, P < 0.001, g = 7.09). This study demonstrates that increased buffering capacity after acute preexercise SB ingestion can improve endurance cycling time-trial performances. The use of SB could be considered for use in 16.1-km cycling time trials, but further work is required to establish these effects after a preexercise meal.

Effects of Dietary Nitrate Supplementation on Performance during Single and Repeated Bouts of Short-Duration High-Intensity Exercise: A Systematic Review and Meta-Analysis of Randomised Controlled Trials.

Inorganic nitrate (NO3-) has emerged as a potential ergogenic aid over the last couple of decades. While recent systematic reviews and meta-analyses have suggested some small positive effects of NO3- supplementation on performance across a range of exercise tasks, the effect of NO3- supplementation on performance during single and repeated bouts of short-duration, high-intensity exercise is unclear. This review was conducted following PRISMA guidelines. MEDLINE and SPORTDiscus were searched from inception to January 2023. A paired analysis model for cross-over trials was incorporated to perform a random effects meta-analysis for each performance outcome and to generate standardized mean differences (SMD) between the NO3- and placebo supplementation conditions. The systematic review and meta-analysis included 27 and 23 studies, respectively. Time to reach peak power (SMD: 0.75, p = 0.02), mean power output (SMD: 0.20, p = 0.02), and total distance covered in the Yo-Yo intermittent recovery level 1 test (SMD: 0.17, p < 0.0001) were all improved after NO3- supplementation. Dietary NO3- supplementation had small positive effects on some performance outcomes during single and repeated bouts of high-intensity exercise. Therefore, athletes competing in sports requiring single or repeated bouts of high-intensity exercise may benefit from NO3- supplementation.

Applying a muscle fatigue model when optimizing load-sharing between muscles for short-duration high-intensity exercise: A preliminary study.

Introduction: Multiple different mathematical models have been developed to represent muscle force, to represent multiple muscles in the musculoskeletal system, and to represent muscle fatigue. However, incorporating these different models together to describe the behavior of a high-intensity exercise has not been well described. Methods: In this work, we adapted the three-compartment controller (3CCr) muscle fatigue model to be implemented with an inverse-dynamics based optimization algorithm for the muscle recruitment problem for 7 elbow muscles to model a benchmark case: elbow flexion/extension moments. We highlight the difficulties in achieving an accurate subject-specific approach for this multi-level modeling problem, considering different muscular models, compared with experimental measurements. Both an isometric effort and a dynamic bicep curl were considered, where muscle activity and resting periods were simulated to obtain the fatigue behavior. Muscle parameter correction, scaling and calibration are addressed in this study. Moreover, fiber-type recruitment hierarchy in force generation was added to the optimization problem, thus offering an additional novel muscle modeling criterion. Results: It was observed that: i) the results were most accurate for the static case; ii) insufficient torque was predicted by the model at some time points for the dynamic case, which benefitted from a more precise calibration of muscle parameters; iii) modeling the effects of muscular potentiation may be important; and iv) for this multilevel model approach, the 3CCr model had to be modified to avoid reaching situations of unrealistic constant fatigue in high intensity exercise-resting cycles. Discussion: All the methods yield reasonable estimations, but the complexity of obtaining accurate subject-specific human models is highlighted in this study. The proposed novel muscle modeling and force recruitment criterion, which consider the muscular fiber-type distinction, show interesting preliminary results.

Effects of Resveratrol on Muscle Inflammation, Energy Utilisation, and Exercise Performance in an Eccentric Contraction Exercise Mouse Model.

Eccentric contraction can easily cause muscle damage and an inflammatory response, which reduces the efficiency of muscle contraction. Resveratrol causes anti-inflammatory effects in muscles, accelerates muscle repair, and promotes exercise performance after contusion recovery. However, whether resveratrol provides the same benefits for sports injuries caused by eccentric contraction is unknown. Thus, we explored the effects of resveratrol on inflammation and energy metabolism. In this study, mice were divided into four groups: a control group, an exercise group (EX), an exercise with low-dose resveratrol group (EX + RES25), and an exercise with high-dose resveratrol group (EX + RES150). The results of an exhaustion test showed that the time before exhaustion of the EX + RES150 group was greater than that of the EX group. Tumour necrosis factor-α (Tnfα) mRNA expression was lower in the EX + RES150 group than in the EX group. The energy utilisation of the EX + RES150 group was greater than that of the EX + RES25 group in different muscles. High-dose resveratrol intervention decreased Tnfα mRNA expression and enhanced the mRNA expressions of sirtuin 1, glucose transporter 4, AMP-activated protein kinase α1, and AMP-activated protein kinase α2 in muscles. These results revealed that high-dose resveratrol supplementation can reduce inflammation and oxidation and improve energy utilisation during short-duration high-intensity exercise.

Effects of ventilation design on thermal comfort performance and breast displacement for sports bras

Most of the research on the thermal comfort of sports bras has focused on fabric differences, whereas the effect of ventilation has yet to be investigated. This study aimed to investigate the effects of ventilation design on the thermal comfort performance and breast displacement. Based on the physiological nature of breast movement and airflow in exercising women, four sports bras with different necklines and ventilation holes were designed. The thermal comfort performance and the reduction of breast displacement of these four bras were compared. Nine healthy women exercised in random order with four sports bras, and then performed a 20-min short duration high-intensity exercise and rest to recover under thermoneutral conditions. Skin temperature and humidity, body core temperature, the reduction of breast displacement and thermal psychological subjective sensations were investigated during the whole experiment. The results indicated that deepening and widening the neckline could effectively increase the airflow pumped in from the neckline, while the ventilation holes could effectively direct the airflow from the neckline to the middle and bottom area of the breasts, significantly reducing the skin temperature, skin humidity and body core temperature ( P &lt; 0.05). In addition, widening the neckline would significantly reduce the reduction of breast displacement, whereas deepening would not. A slightly but not significant increase of the psychological subjective sensation during exercise was observed. These results provide novel information that appropriate application of ventilation design in sports bras could effectively improve the thermal comfort performance without reducing the function of support to benefit exercising women.

Menthol Mouth Rinsing Maintains Relative Power Production during Three-Minute Maximal Cycling Performance in the Heat Compared to Cold Water and Placebo Rinsing.

Previous menthol studies have demonstrated ergogenic effects in endurance-based activity. However, there is a need for research in sports whose physiological requirements exceed maximal aerobic capacity. This study assessed the effects of 0.1% menthol mouth-rinsing upon a modified three-minute maximal test in the heat (33.0 ± 3.0 °C; RH 46.0 ± 5.0%). In a randomised crossover single blind placebo-controlled study, 11 participants completed three modified maximal tests, where each trial included a different mouth rinse: either menthol (MEN), cold water (WAT) or placebo (PLA). Participants were asked to rate their thermal comfort (TC), thermal sensation (TS) and rating of perceived exertion (RPE) throughout the test. Heart rate, core temperature, oxygen uptake (VO2), ventilation (VE) and respiratory exchange ratio (RER) were monitored continuously throughout the test, alongside cycling power variables (W; W/kg). A blood lactate (BLa) level was taken pre- and post- test. Small to moderate effects (Cohen’s d and accompanying 90% confidence intervals) between solutions MEN, WAT and PLA were observed towards the end of the test in relation to relative power. Specifically, from 75–105 s between solutions MEN and WAT (ES: 0.795; 90% CI: 0.204 to 1.352) and MEN and PLA (ES: 1.059; 90% CI: 0.412 to 1.666), this continued between MEN and WAT (ES: 0.729; 90% CI: 0.152 to 1.276) and MEN and PLA (ES: 0.791; 90% CI: 0.202 to 1.348) from 105–135 s. Between 135–165 s there was a moderate difference between solutions MEN and WAT (ES: 1.058; 90% CI: 0.411 to 1.665). This indicates participants produced higher relative power for longer durations with the addition of the menthol mouth rinse, compared to cold water or placebo. The use of menthol (0.1%) as a mouth rinse showed small performance benefits for short duration high intensity exercise in the heat.

Delayed Rebound of Glycemia During Recovery Following Short-Duration High-Intensity Exercise: Are There Lactate and Glucose Metabolism Interactions?

Lactate constitutes the primary gluconeogenic precursor in healthy humans at rest and during low-intensity exercise. Data on the interactions between lactate and glucose metabolisms during recovery after short-duration high-intensity exercise are sparse. The aim of the present study was to describe blood glucose ([glucose]b) and lactate ([lactate]b) concentration curves during recovery following short-duration high-intensity exercise. Fifteen healthy Cameroonian subjects took part in the study and performed successively (i) an incremental exercise to exhaustion to determine maximal work rate (Pmax) and (ii) a 2-min 110% Pmax exercise after which blood lactate and glucose concentrations were measured during the 80-min passive recovery. In response to the 2-min 110% Pmax exercise, [glucose]b remained stable (from 4.93 ± 1.13 to 4.65 ± 0.74 mmol.L−1, NS) while [lactate]b increased (from 1.35 ± 0.36 to 7.87 ± 1.66 mmol.L−1, p < 0.0001). During recovery, blood lactate concentrations displayed the classic biphasic curve while blood glucose concentrations displayed a singular shape including a delayed and transitory rebound of glycemia. This rebound began at 27.7 ± 6.2 min and peaked at 6.78 ± 0.53 mmol.L−1 at 56.3 ± 9.7 min into recovery. The area under the curve (AUC) of [lactate]b during the rebound of glycemia was positively correlated with the peak value of glycemia and the AUC of [glucose]b during the rebound. In conclusion, the delayed rebound of glycemia observed in the present study was associated with lactate availability during this period.

Nutrition and Exercise in a Case of Carnitine Palmitoyl-Transferase II Deficiency.

In the mild subtype of inherited carnitine palmitoyltransferase II (CPTII) deficiency, muscular mitochondrial fatty acid β-oxidation is impaired. In this condition, interventions involve daily dietary restriction of fats and increase of carbohydrates, whereas physical exercise is commonly contraindicated due to the risk of muscle pain and rhabdomyolysis. We present the case of a 14-year-old female with CPTII deficiency who underwent a 1-h session of unsupervised exercise training for 6 months, 3 days per week, including interval and resistance exercises, after diet assessment and correction. Before and after intervention, the resting metabolic rate (RMR) and respiratory quotient (RQ) were measured by indirect calorimetry, and a cardiopulmonary exercise test (CPET, 10 W/30 s to exhaustion) was performed. Interval training consisted of a 1 min run and a 5 min walk (for 15 min progressively increased to 30 min). During these efforts, the heart rate was maintained over 70% HR max corresponding to respiratory exchange ratio (RER) of 0.98. Resistance training included upper/lower split workouts (3 sets of 8 repetitions each, with 2 min rest between sets). Blood CK was checked before and 36 h after two training sessions chosen randomly without significant difference. After training, RMR increased (+8.1%) and RQ lowered into the physiological range (from 1.0 to 0.85). CPET highlighted an increase of peak power output (+16.7%), aerobic performance (VO2 peak, 8.3%) and anaerobic threshold (+5.7%), oxygen pulse (+4.5%) and a much longer isocapnic buffering duration (+335%). No muscle pain or rhabdomyolysis was reported. Results from our study highlight that training based on short-duration high-intensity exercise improves overall metabolism and aerobic fitness, thus being feasible, at least in a case of CPTII deficiency.

Effects of a single bout of short-duration high-intensity and long-duration low-intensity exercise on insulin resistance and adiponectin/leptin ratio

ObjectivesModerate-intensity exercise improves insulin sensitivity, which may depend on the intensity, duration, and frequency of exercise. We examined the effects of a single bout of short-duration high-intensity exercise (HIE) and long-duration lowintensity exercise (LIE) on insulin sensitivity and the adiponectin/leptin ratio in individuals with different body mass indices (BMIs) who do not exercise regularly. MethodsWe enrolled 42 healthy volunteers aged 20–64 years and divided them into two groups based on BMI: BMI <24 kg/m2 and BMI ≥27 kg/m2. They were randomly assigned to either the short-duration (20 min) HIE (70%–80% heart rate reserve, HRR) or long-duration (60 min) LIE training groups (30%–40% HRR). Glucose, insulin, adiponectin, and leptin levels were assessed before training and at 0, 30, 60, and 120 min after training. ResultsWe finally analyzed 27 normal weight and 9 obese individuals. No significant differences were observed in the baseline information of both BMI groups. Homeostatic model assessment for insulin resistance significantly improved for both exercise patterns in the normal weight group and for the HIE pattern in the obese group (P < 0.01), whereas the adiponectin/leptin ratio increased significantly only among normal weight participants with the LIE intervention. ConclusionBoth exercise patterns in BMI <24 kg/m2 and BMI ≥27 kg/m2 benefit on insulin resistance. Therefore, people can choose the way they can fit to improve insulin resistance both short-duration high-intensity exercise and long-duration low-intensity exercise.

No Improvement in Running Time to Exhaustion at 100% VO2max in Recreationally Active Male Runners With a Preexercise Single-Carbohydrate Mouth Rinse.

Carbohydrate (CHO) mouth rinse has been used as an ergogenic strategy due to its central effect; however, the effects of this intervention during short-duration high-intensity exercises are not fully understood. To investigate the effect of CHO mouth rinse on time to exhaustion in a short-duration high-intensity exercise performed on a treadmill. A randomized double-blind, placebo-controlled, crossover study was conducted with 10 (24.1 [4.3]y) recreationally active male runners. The protocol consisted of a warm-up at 65% of VO2max for 5min followed by 3min passive rest. At the end of this rest period, the individuals performed their mouth rinse either with CHO (maltodextrin, 6%) or with placebo (industrialized noncaloric juice with the same taste). Immediately after mouth rinse, the subjects ran at velocity equivalent to 100% of individual VO2max until voluntary exhaustion. The perceived effort was obtained through a Borg scale. Blood lactate was quantified before and after the protocol, and heart rate was evaluated during the protocol. No difference was found (P = .90) in time to exhaustion between placebo (193.9 [46.5]s) and CHO mouth rinse (195.1 [51.8]s). Blood lactate, heart rate, and perception of effort increased in both groups, but with no differences (all variables, P > .05) between groups. The findings showed that a preexercise single-CHO mouth rinse was ineffective to improve running time to exhaustion at velocity equivalent to 100% VO2max on a treadmill in recreationally active male runners.

Short-Duration High-Intensity Interval Exercise Training Is More Effective Than Long Duration for Blood Pressure and Arterial Stiffness But Not for Inflammatory Markers and Lipid Profiles in Patients With Stage 1 Hypertension.

The present study compared the effects of 2 different high-intensity interval training (HIIT) protocols on arterial stiffness, lipid profiles, and inflammatory markers in hypertensive patients. Thirty hypertensive (stage 1) patients, aged 48.0 ± 3.2 yr, were randomly allocated to the short-duration HIIT (SDHIIT, n = 10), long-duration HIIT (LDHIIT, n = 10), and control (n = 10) groups. After a 2-wk preparatory phase of continuous mild training, patients in the SDHIIT group performed 8 wk of HIIT including 27 repetitions of 30-sec activity at 80% to 100% of (Equation is included in full-text article.)O2peak interspersed with 30-sec passive/active (10%-20% of (Equation is included in full-text article.)O2peak) recovery. Patients in the LDHIIT group performed 8 wk of HIIT, 32 min/session including 4 repetitions of 4-min activity at 75% to 90% of (Equation is included in full-text article.)O2peak interspersed with 4-min passive/active (15%-30% of (Equation is included in full-text article.)O2peak) recovery. Blood pressure (BP), pulse wave velocity (PWV), inflammatory markers, and lipid profiles were measured before and after training. Significant (P < .05) reductions in systolic blood pressure and PWV were found following 2 training protocols, though, only the changes in PWV following the SDHIIT were significantly different than those in the LDHIIT and control groups. Interleukin-6 and triglycerides decreased and interleukin-10 increased significantly (P < .01) following both HIIT programs, whereas the differences between the 2 training protocols were not statistically significant. C-reactive protein and lipids did not change significantly following HIIT. Performing HIIT improves systolic blood pressure and inflammatory markers in patients with stage 1 hypertension irrespective of the HIIT intensity and duration, and PWV improvement is intensity related.

The Effects Of A Six-week Ketogenic Diet On The Performance Of Short-duration, High-intensity Exercise

There is much controversy surrounding the use of very high fat, low carbohydrate ketogenic diets and athletic performance. Specifically, it has been hypothesized that anaerobic activity, which is primarily fueled by ATP that is formed through the metabolism of carbohydrate sources, may be hindered when utilizing a ketogenic dietary approach. PURPOSE: The current study was designed to investigate how switching from a habitual diet to a ketogenic diet for 6 weeks would affect the performance of short-duration, high-intensity exercise. METHODS: Eight men and seven women (N = 15; 30.2 yr ± 4.11) were randomly assigned to either the ketogenic diet (KETO; n = 8) or the control group (CON; n = 7). All subjects were trained in CrossFit for at least 3 months prior to the study. Several measures of anaerobic performance were assessed at baseline and following 6 weeks utilizing the following series of standardized exercise tests: timed 500m row, Wingate Anaerobic Test, and 3-repetition maximum (3RM) deadlift. Aerobic capacity was also assessed by measuring VO2peak. Subjects continued their regular CrossFit training during the 6 week period and dietary intake was recorded. RESULTS: A significant increase (p < .05) in mean power output (MPO; W/kg) from baseline (M = 8.24 ± 1.15) to 6 weeks (M = 8.70 ± .82) was found the CON group. No significant interactions (p > .05) were found between diet and test time for any of the other measured exercise variables. No significant differences (p > .05) were found in the KETO group from baseline to 6 weeks in any of the measured exercise variables. No significant differences in body weight (lbs) were found from baseline to 6 weeks in either group (KETO; 183.8 ± 31.71 vs. 181.03 ± 30.28, CON; 166.38 ± 35.77 vs. 166.88 ±37.28). Attrition rate was 33% in the KETO group and 30% in the CON group. CONCLUSION: A 6-week ketogenic diet did not affect the performance of short-duration high-intensity exercise. Our data does not support the hypothesis that ketogenic diets induce detriments in the performance of activity that is anaerobic in nature. The current study took place over a 6 week period, allowing for keto-adaptation to occur; results may be different if a shorter time period were utilized.

The Effects of Pre-Exercise Blood Glucose on Responses to Short Duration High Intensity Exercise

Carbohydrate ingestion prior to exercise has been the subject of much debate over the last few decades with a range of individual responses observed with different carbohydrate loads, across a time period of 15-75 minutes pre-exercise.

Time of day and short-duration high-intensity exercise influences on coagulation and fibrinolysis

Exercise has been demonstrated to have considerable effects upon haemostasis, with activation dependent upon the duration and intensity of the exercise bout. In addition, markers of coagulation and fibrinolysis have been shown to possess circadian rhythms, peaking within the morning (0600–1200 h). Therefore, the time of day in which exercise is performed may influence the activation of the coagulation and fibrinolytic systems. This study aimed to examine coagulation and fibrinolytic responses to short-duration high-intensity exercise when completed at different times of the day. Fifteen male cyclists (VO2max: 60.3 ± 8.1 ml kg−1 min−1) completed a 4-km cycling time trial (TT) on five separate occasions at 0830, 1130, 1430, 1730 and 2030. Venous blood samples were obtained pre- and immediately post-exercise, and analysed for tissue factor (TF), tissue factor pathway inhibitor (TFPI), thrombin–anti-thrombin complexes (TAT) and D-Dimer. Exercise significantly increased plasma concentrations of TF (p < .0005), TFPI (p < .0006), TAT complexes (p < .0012) and D-Dimer (p < .0003). There was a time-of-day effect in pre-exercise TF (p = .004) and TFPI (p = .031), with 0830 greater than 1730 (p .001), while 1730 was less than 2030 h (p = .008), respectively. There was no significant effect of time of day for TAT (p = .364) and D-Dimer (p = .228). Power output, TT time and heart rate were not significantly different between TTs (p > .05); however, percentage VO2max was greater at 1730 when compared to 2030 (p = .04). Due to a time-of-day effect present within TF, peaking at 0830, caution should be applied when prescribing short-duration high-intensity exercise bout within the morning in populations predisposed to hypercoagulability.

Does time of day and short-duration high-intensity exercise effect haemostasis?

Does time of day and short-duration high-intensity exercise effect haemostasis?

Effect of water-based recovery on blood lactate removal after high-intensity exercise.

This study assessed the effectiveness of water immersion to the shoulders in enhancing blood lactate removal during active and passive recovery after short-duration high-intensity exercise. Seventeen cyclists underwent active water- and land-based recoveries and passive water and land-based recoveries. The recovery conditions lasted 31 minutes each and started after the identification of each cyclist’s blood lactate accumulation peak, induced by a 30-second all-out sprint on a cycle ergometer. Active recoveries were performed on a cycle ergometer at 70% of the oxygen consumption corresponding to the lactate threshold (the control for the intensity was oxygen consumption), while passive recoveries were performed with subjects at rest and seated on the cycle ergometer. Blood lactate concentration was measured 8 times during each recovery condition and lactate clearance was modeled over a negative exponential function using non-linear regression. Actual active recovery intensity was compared to the target intensity (one sample t-test) and passive recovery intensities were compared between environments (paired sample t-tests). Non-linear regression parameters (coefficients of the exponential decay of lactate; predicted resting lactates; predicted delta decreases in lactate) were compared between environments (linear mixed model analyses for repeated measures) separately for the active and passive recovery modes. Active recovery intensities did not differ significantly from the target oxygen consumption, whereas passive recovery resulted in a slightly lower oxygen consumption when performed while immersed in water rather than on land. The exponential decay of blood lactate was not significantly different in water- or land-based recoveries in either active or passive recovery conditions. In conclusion, water immersion at 29°C would not appear to be an effective practice for improving post-exercise lactate removal in either the active or passive recovery modes.

The Influence of Short Duration Exercise on the Concentration of C-Reactive Protein and Selected Haematological and Biochemical Parameters in the Blood of German Shepherd Dogs

Abstract Short-term intensive exercise may be associated with many short-lasting metabolic changes. These changes depend on the duration and intensity of the exercise. The aim of our study was to determine potential changes in C-reactive protein (CRP) and selected haematological and biochemical parameters in clinically healthy German shepherd dogs before short duration high-intensity exercise and 6 hours after the exercise. During the study, the dogs were subjected to the following defensive training: detaining a figurant running away from a dog (2×) and detaining with a counterattack (2×). The running distance was 200 m at a mean speed of 28 km.h-1. The investigation of haematological parameters revealed a significant decrease in the mean values of platelet haematocrit (PCT) 6 hours after the training. Significant differences in the levels determined before and after exercise were observed also for phosphorus (P) and for iron (Fe). At the same time, we observed a significant increase in the mean calcium (Ca) level and a significant decrease in sodium (Na) and chlorides (Cl). The activity of aspartate aminotransferase (AST) significantly increased after exercise. Concentrations of acute phase C-reactive proteins were increased 6 hours after exercise in comparison to those before exercise but the difference was insignificant. Although the concentration of CRP was increased insignificantly after the exercise, when interpreting concentrations of this nonspecific indicator of inflammation, one should keep in mind that intensive exercise may also affect its concentrations.