Treadmill Running Test Research Articles

Exercise-Induced Bronchoconstriction in Children: State of the Art from Diagnosis to Treatment.

Exercise-induced bronchoconstriction (EIB) is a common clinical entity in people with asthma. EIB is characterized by postexercise airway obstruction that results in symptoms such as coughing, dyspnea, wheezing, chest tightness, and increased fatigue. The underlying mechanism of EIB is not completely understood. "Osmotic theory" and "thermal or vascular theory" have been proposed. Initial assessment must include a specific work-up to exclude alternative diagnoses like exercise-induced laryngeal obstruction (EILO), cardiac disease, or physical deconditioning. Detailed medical history and clinical examination must be followed by basal spirometry and exercise challenge test. The standardized treadmill running (TR) test, a controlled and standardized method to assess bronchial response to exercise, is the most adopted exercise challenge test for children aged at least 8 years. In the TR test, the goal is to reach the target heart rate in a short period and maintain it for at least 6 min. The test is then followed by spirometry at specific time points (5, 10, 15, and 30 min after exercise). In addition, bronchoprovocation tests like dry air hyperpnea (exercise and eucapnic voluntary hyperpnea) or osmotic aerosols (inhaled mannitol) can be considered when the diagnosis is uncertain. Treatment options include both pharmacological and behavioral approaches. Considering medications, the use of short-acting beta-agonists (SABA) just before exercise is the commonest option strategy, but daily inhaled corticosteroids (ICS) can also be considered, especially when EIB is not controlled with SABA only or when the patients practice physical activity very often. Among the behavioral approaches, warm-up before exercise, breathing through the nose or face mask, and avoiding polluted environments are all recommended strategies to reduce EIB risk. This review summarizes the latest evidence published over the last 10 years on the pathogenesis, diagnosis using spirometry and indirect bronchoprovocation tests, and treatment strategies, including SABA and ICS, of EIB. A specific focus has been placed on EIB management in young athletes, since this condition can not only prevent them from practicing regular physical activity but also competitive sports.

Impact of Anaerobic Exercise Integrated Into Regular Training on Experienced Judo Athletes: Running Vs. Repetitive Throws.

Kamandulis, S, Dudėnienė, L, Snieckus, A, Kniubaite, A, Mickevicius, M, Lukonaitiene, I, Venckunas, T, Stasiule, L, and Stasiulis, A. Impact of anaerobic exercise integrated into regular training on experienced judo athletes: running vs. repetitive throws. J Strength Cond Res 38(9): e489-e495, 2024-Anaerobic training in high-level athletes is of considerable interest to practitioners aiming to optimize performance. This study compared the impact of interval anaerobic training (IAT) sessions consisting of either high-intensity running or throwing that were performed twice a week together with regular judo training on the anaerobic and aerobic performance of experienced judo athletes. Employing a repeated-measures, counterbalancing, research design, 12 national team judo athletes (7 women and 5 men; mean age, 20.4 ± 0.95 years; mean judo training experience, 13.4 ± 1.4 years; competitive level, black belt first and second Dan) performed each IAT modality for 6 weeks, for a full training cycle of 12 weeks. Assessments of their anaerobic fitness (Cunningham and Faulkner Anaerobic Treadmill Test), sport-specific anaerobic fitness (Special Judo Fitness Test [SJFT]), and aerobic capacity (maximal incremental treadmill running test) were performed before, after 6 weeks, and after 12 weeks of training. The uphill running performance improved by 13.1% over the 12-week period ( p = 0.047). Simultaneously, there was a 9.0% improvement in the SJFT index and a 6.9% increase in the number of throws ( p = 0.011 and p = 0.017, respectively). Although a trend for throwing drills being more effective than interval sprint running was observed, the interaction effect lacked statistical significance ( p = 0.074). Moreover, no substantial changes were noted in aerobic endurance markers. In conclusion, this study suggests that incorporating specific and nonspecific high-intensity drills into a routine training regimen may enhance anaerobic capacity among well-trained judo athletes, potentially leading to favorable competitive outcomes.

Menstrual Cycle Phase Has No Influence on Performance-Determining Variables in Endurance-Trained Athletes: The FENDURA Project.

This study aimed to investigate the effect of the MC and endogenous sex hormone concentrations on performance-determining variables in three distinct MC phases in endurance-trained females. Twenty-one eumenorrheic trained/highly trained endurance athletes completed a standardized test battery during the early follicular phase (EFP), ovulatory phase (OP), and midluteal phase (MLP) for either one ( n = 7) or two test cycles ( n = 14). MC phases were determined using calendar-based counting, urinary ovulation testing, and verified with serum hormone analysis. MCs were retrospectively classified as eumenorrheic or disturbed. Disturbed MCs were excluded from analysis. The test battery consisted of 4-6 × 5-min submaximal stages with stepwise speed increases, a 30-s all-out double-poling ski ergometer test, and a maximal incremental treadmill running test. At a group level, there was no effect of MC phase or the serum concentrations of estrogen and progesterone on peak oxygen uptake (V̇O 2peak ), oxygen uptake at 4 mmol·L -1 blood lactate concentration, time to exhaustion, running economy, or mean 30-s power output (MPO 30s ). Serum testosterone concentration was positively associated with MPO 30s ( P = 0.016). Changes in V̇O 2peak from EFP to MLP were inconsistent between individuals and across cycles. None of the measured performance-determining variables were influenced by MC phase or serum estrogen or progesterone concentrations. Although some individual patterns could be observed, there was no indication that any single MC phase is consistently associated with improved or impaired V̇O 2peak on a group level.

Reliability of Xsens inertial measurement unit in measuring trunk accelerations: a sex-based differences study during incremental treadmill running.

Inertial measurement units (IMUs) are utilized to measure trunk acceleration variables related to both running performances and rehabilitation purposes. This study examined both the reliability and sex-based differences of these variables during an incremental treadmill running test. Eighteen endurance runners performed a test-retest on different days, and 30 runners (15 females) were recruited to analyze sex-based differences. Mediolateral (ML) and vertical (VT) trunk displacement and root mean square (RMS) accelerations were analyzed at 9, 15, and 21 km·h-1. No significant differences were found between test-retests [effect size (ES)<0.50)]. Higher intraclass correlation coefficients (ICCs) were found in the trunk displacement (0.85-0.96) compared to the RMS-based variables (0.71-0.94). Male runners showed greater VT displacement (ES = 0.90-1.0), while female runners displayed greater ML displacement, RMS ML and anteroposterior (AP), and resultant euclidean scalar (RES) (ES = 0.83-1.9). The IMU was found reliable for the analysis of the studied trunk acceleration-based variables. This is the first study that reports different results concerning acceleration (RMS) and trunk displacement variables for a same axis in the analysis of sex-based differences.

Monocarboxylate transporter 4 deficiency enhances high-intensity interval training-induced metabolic adaptations in skeletal muscle.

High-intensity exercise stimulates glycolysis, subsequently leading to elevated lactate production within skeletal muscle. While lactate produced within the muscle is predominantly released into the circulation via the monocarboxylate transporter 4 (MCT4), recent research underscores lactate's function as an intercellular and intertissue signalling molecule. However, its specific intracellular roles within muscle cells remains less defined. In this study, our objective was to elucidate the effects of increased intramuscular lactate accumulation on skeletal muscle adaptation to training. To achieve this, we developed MCT4 knockout mice and confirmed that a lack of MCT4 indeed results in pronounced lactate accumulation in skeletal muscle during high-intensity exercise. A key finding was the significant enhancement in endurance exercise capacity at high intensities when MCT4 deficiency was paired with high-intensity interval training (HIIT). Furthermore, metabolic adaptations supportive of this enhanced exercise capacity were evident with the combination of MCT4 deficiency and HIIT. Specifically, we observed a substantial uptick in the activity of glycolytic enzymes, notably hexokinase, glycogen phosphorylase and pyruvate kinase. The mitochondria also exhibited heightened pyruvate oxidation capabilities, as evidenced by an increase in oxygen consumption when pyruvate served as the substrate. This mitochondrial adaptation was further substantiated by elevated pyruvate dehydrogenase activity, increased activity of isocitrate dehydrogenase - the rate-limiting enzyme in the TCA cycle - and enhanced function of cytochrome c oxidase, pivotal to the electron transport chain. Our findings provide new insights into the physiological consequences of lactate accumulation in skeletal muscle during high-intensity exercises, deepening our grasp of the molecular intricacies underpinning exercise adaptation. KEY POINTS: We pioneered a unique line of monocarboxylate transporter 4 (MCT4) knockout mice specifically tailored to the ICR strain, an optimal background for high-intensity exercise studies. A deficiency in MCT4 exacerbates the accumulation of lactate in skeletal muscle during high-intensity exercise. Pairing MCT4 deficiency with high-intensity interval training (HIIT) results in a synergistic boost in high-intensity exercise capacity, observable both at the organismal level (via a treadmill running test) and at the muscle tissue level (through an ex vivo muscle contractile function test). Coordinating MCT4 deficiency with HIIT enhances both the glycolytic enzyme activities and mitochondrial capacity to oxidize pyruvate.

The Relationship between the Change in Pelvic Alignment during Moderate-Intensity Running and the Subjective Rating of Perceived Exertion, Rating of Perceived Exertion for Legs and Gluteus Muscles Fatigue in Female Novice and Recreational Runners

Running has become 1 of the 2 most well-known exercises for health; however, running may cause injuries. The purpose of this analytical descriptive study was to examine the occurrence of pelvic drop during moderate-intensity running in female novice and recreational runners; as well as investigating the relationship between the change in pelvic alignment and Rating of Perceived Exertion (RPE), Rating of Perceived Exertion for Legs (RPElegs) and Gluteus muscles fatigue in novice and recreational runners. The participants, aged between 18 and 35 years old, comprised 27 novice runners (less than 1 year of running experience) and 27 recreational runners (2 - 4 years running experience). The participants in both groups performed the maximal oxygen uptake (VO2max) test and ran at a self-selected speed on a treadmill for 30 min at moderate-intensity within the specified heart rate range of 40 - 59 % heart rate reserve (HRR). RPE, RPElegs and sEMG were collected every 2 min and the pelvic kinematic data were also recorded every minute during the 30 min treadmill running test. The data were analyzed with a statistical significance level at p-value &lt; 0.05. The results demonstrated that the time in starting pelvic drop was 8.15 ± 5.07 and 18.37 ± 6.70 min in female novice and recreational runner groups, respectively (p &lt; 0.01). Pearson’s correlations showed relationship between the pelvic alignment and RPE in novice runners (r = 0.47, p &lt; 0.01) and recreational runners (r = 0.39, p &lt; 0.01). Besides, Pearson’s correlations showed relationship between the pelvic alignment and RPElegs in novice runners (r = 0.48, p &lt; 0.01) and recreational runners (r = 0.32, p &lt; 0.01). In both groups, there was no relationship between the pelvic alignment and Gluteus medius and Gluteus maximus muscle fatigue. According to the study, the occurrence of a pelvic drop in novice runners was faster than recreational runners. The study indicated that consideration of RPE and RPElegs variables might be beneficial for female runners and future studies. HIGHLIGHTS The occurrence of pelvic drop in novice runners was faster than recreational runners. There was a relationship between the change in pelvic alignment and RPE and also RPElegs in female novice and recreational runners. The study indicated that consideration of RPE and RPElegs variables might be beneficial for female runners and future studies. GRAPHICAL ABSTRACT

Attenuation of the increase of heart rate and oxygen consumption during progressive exercise in professional rugby players.

The response of oxygen uptake (VO<inf>2</inf>) and heart rate (HR) to continuous progressive large muscle mass exercise is not always linear. This study aimed to compare the patterns of the Speed/VO<inf>2</inf> (S/VO<inf>2</inf>) and speed/HR (S/HR) relationships during an incremental treadmill-running test in professional rugby players. Fourteen professional rugby athletes performed a maximal incremental treadmill-running test, following the Conconi test protocol. Speed, heart rate, and gas exchange parameters were recorded. The slope of the S/VO<inf>2</inf> and S/HR relationships were mathematically determined. The S/VO<inf>2</inf> and S/HR relationships were linear up to a submaximal speed and curvilinear thereafter. The speed of locomotion at which the slope of the S/VO<inf>2</inf> and S/HR relationships start to attenuate (VO<inf>2att</inf> and HR<inf>att</inf>) were coincident (12.3±1.0 and 12.4±0.9 km/h), strongly correlated and in good agreement. VO<inf>2</inf> values at VO<inf>2att</inf> (44.9±8.7 mL/kg/min) were significantly correlated with VO<inf>2</inf> values at the ventilatory threshold (43.3±6.0 mL/kg/min) (R2=0.83, P=0.001) and in good agreement. The running speed/VO<inf>2</inf> ratio (ΔS/ΔVO<inf>2</inf>) up to VO<inf>2att</inf> was significantly lower than that beyond VO<inf>2att</inf> (2.98±1.1 vs. 5.16±2.31); P<0,001). The speed/oxygen uptake and S/HR relationships during progressive exercise start to attenuate at a coincident exercise intensity, and at oxygen uptake values strongly correlated with the ventilatory threshold. These findings further support the usefulness of the attenuation of the S/HR relationship as a practical tool for exercise testing and training purposes in professional rugby players.

Physiological Variables that Contribute to Aerobic Fitness in Boys during Early Adolescence in the Context of Basketball Training and the Maturity Level.

The aim of this study was to assess physiological variables that contribute to aerobic fitness in respect to basketball training and the maturity level in adolescent boys. Our subjects were 28 basketball-trained and 22 control-group boys (average age: 11.83 ± 0.43 years). An incremental treadmill running test to exhaustion was performed twice with a 1-year interval between the sessions to determine the following peak aerobic fitness variables: oxygen uptake, stroke volume, cardiac output, minute ventilation, and others. Maturity offset was used to evaluate the maturity level. The basketball-trained group exhibited a higher peak ratio-scaled oxygen uptake (1st session: 50.55 ± 6.21 and 46.57 ± 5.68 ml/kg/min in basketball and control-group boys, respectively, p = 0.024; 2nd session: 54.50 ± 6.50 and 45.33 ± 5.99 ml/kg/min, respectively, p < 0.001) during both testing sessions. During the 2nd session, the basketball-trained group also showed a significantly higher peak arteriovenous oxygen difference (basketball-trained boys: 14.02 ± 2.17 ml/100 ml; control-group boys: 12.52 ± 2.49 ml/100 ml; p = 0.027) and peak minute ventilation (basketball-trained boys: 96.08 ± 21.71 l/min; control-group boys: 83.14 ± 17.85 l/min; p = 0.028). The maturity level among the basketball-trained boys was correlated with peak variables: oxygen uptake, stroke volume, cardiac output, and minute ventilation, but not with the ratio-scaled oxygen uptake. In conclusion, basketball training at a young age among boys improved aerobic fitness compared with sedentary boys. More mature basketball players were not superior to their less mature peers regarding aerobic fitness after adjusting for body dimensions.

Behavior of skin temperature during incremental cycling and running indoor exercises

The study of the human body's energy behavior has received more attention over the past years. The development of thermal infrared cameras brought new possibilities for evaluating physical exercise performance. This work aims to study the skin temperature distribution during treadmill running and cycle ergometer tests with a graded load exercise until exhaustion. Eight amateur athletes performed both tests. In addition, the ventilatory and metabolic data were measured by indirect calorimetry. The thermoregulatory system is highly requested to maintain the internal body temperature. Consequently, the average skin temperature decreased during running and cycling tests, although with a higher variation in running. It was observed that the lower limbs had a similar performance for both exercises; on the other hand, the upper limbs had a higher temperature decrease for running. This may be explained by increased body energy transfer to the environment due to higher degrees of freedom during the test. The main contribution is comparing the thermal behavior of the person's skin performing two different activities, constructing a basis for future energy and exergy analysis of the human body under physical activities complementary to the literature.

Effects of Endurance Training on Metabolic Enzyme Activity and Transporter Proteins in Skeletal Muscle of Ovariectomized Mice.

Estrogen deficiency or insufficiency can occur under several conditions, leading to negative health outcomes. To establish an effective countermeasure against estrogen loss, we investigated the effects of endurance training on ovariectomy (OVX)-induced metabolic disturbances. Female Institute of Cancer Research mice underwent OVX or sham operations. On day 7 of recovery, the mice were randomized to remain either sedentary or undergo 5 wk of treadmill running (15-20 m·min -1 , 60 min, 5 d·wk -1 ). During week 5 of the training, all animals performed a treadmill running test (15 m·min -1 , 60 min). After the experimental period, OVX resulted in greater gains in body mass, fat mass, and triglyceride content in the gastrocnemius muscle. OVX enhanced phosphofructokinase activity in the plantaris muscle and decreased lactate dehydrogenase activity in the plantaris and soleus muscles. OVX decreased the protein content of NDUFB8, a mitochondrial respiratory chain subunit, but did not decrease other mitochondrial proteins or enzyme activities. Endurance training significantly enhanced mitochondrial enzyme activity and protein content in the skeletal muscles. Although OVX increased the respiratory exchange ratio during the treadmill running test, and postexercise blood lactate levels, endurance training normalized these parameters. The present findings suggest that endurance training is a viable strategy to counteract the negative metabolic consequences in hypoestrogenism.

Constitutive activation of estrogen receptor α signaling in muscle prolongs exercise endurance in mice

Estrogen is a female hormone that plays a role in various tissues, although the mechanism in skeletal muscle has not been fully clarified. We previously showed that systemic administration of estrogen for 10 weeks ameliorated decreased exercise endurance in ovariectomized mice. To assess whether a long-term and muscle-specific activation of estrogen signaling modulates muscle function, we constructed an expression plasmid for a constitutively active estrogen receptor α (caERα) under the control of muscle creatine kinase (Mck) gene promoter/enhancer. In C2C12 mouse myoblastic cells, transfection of the Mck-caERα plasmid elevated the estrogen response element-driven transcription in a ligand-independent manner. Using this construct, we generated Mck-caERα transgenic mice, in which caERα is predominantly expressed in muscle. Treadmill running test revealed that female Mck-caERα mice exhibit a prolonged running time and distance compared with the wild-type mice. Moreover, microarray expression analysis revealed that the genes related to lipid metabolism, insulin signaling, and growth factor signaling were particularly upregulated in the quadriceps femoris muscle of Mck-caERα mice. These results suggest that estrogen signaling potentiates exercise endurance in skeletal muscle through modulating the expression of metabolism-associated genes.

Effects of different hydration supports on stride kinematics, comfort, and impact accelerations during running

BackgroundDifferent supports for hydration can influence total body mass and affect running biomechanics. Research questionDo different hydration supports affect the perceived exertion and comfort, stride kinematics, and impact accelerations during running? MethodsThis was a crossover study design. Thirteen trail runners completed a treadmill running test divided into four different durations and randomized hydration supports conditions, lasting 8 min each at moderate intensity: A) waist bag (0.84 kg); B) medium load backpack (0.84 kg); C) full load backpack (3.40 kg); and D) a control condition without water support. Impact accelerations were measured for 30 s in 4, 6, and 8 min. The rate of perceived exertion and heart rate were registered on minutes 4 and 8. At the last minute of each condition, comfort perception was registered Results and significanceNo condition affected the stride kinematics. Full load backpack condition reduced head acceleration peak (−0.21 g; p = 0.04; ES=0.4) and head acceleration magnitude (−0.23 g; p = 0.03; ES=0.4), and increased shock attenuation (3.08 g; p = 0.04; ES=0.3). It also elicited higher perceived exertion (p < 0.05; ES>0.8) being considered heavier (p < 0.01; ES > 1.1). The waist bag condition was more comfortable in terms of noise (p = 0.006; ES=1.3) and humidity/heat (p = 0.001; ES=0.8). The waist bag was the most comfortable support. On the other hand, the full backpack elicited lower comfort and was the only generating compensatory adjustments. These results may help to improve design of full load backpack aiming at comfort for runners.

Effects of endurance training on metabolic enzyme activity and transporter protein levels in the skeletal muscles of orchiectomized mice

This study investigated whether endurance training attenuates orchiectomy (ORX)-induced metabolic alterations. At 7 days of recovery after sham operation or ORX surgery, the mice were randomized to remain sedentary or undergo 5 weeks of treadmill running training (15–20 m/min, 60 min, 5 days/week). ORX decreased glycogen concentration in the gastrocnemius muscle, enhanced phosphofructokinase activity in the plantaris muscle, and decreased lactate dehydrogenase activity in the plantaris and soleus muscles. Mitochondrial enzyme activities and protein content in the plantaris and soleus muscles were also decreased after ORX, but preserved, in part, by endurance training. In the treadmill running test (15 m/min, 60 min) after 4 weeks of training, orchiectomized sedentary mice showed impaired exercise performance, which was restored by endurance training. Thus, endurance training could be a potential therapeutic strategy to prevent the hypoandrogenism-induced decline in muscle mitochondrial content and physical performance.

Differences between Elite Male and Female Badminton Athletes Regarding Heart Rate Variability, Arterial Stiffness, and Aerobic Capacity.

Cardiovascular health and aerobic capacity play crucial roles in determining the performance of athletes in the highly competitive sport of badminton. Few studies have directly compared heart rate variability (HRV), arterial stiffness, and aerobic capacity between male and female athletes, especially among badminton athletes. This study investigated sex differences in HRV, arterial stiffness, and aerobic capacity in badminton athletes. Elite badminton athletes were recruited and divided into male (n = 20, 21.0 ± 1.8 years old) and female (n = 16, 21.2 ± 2.3 years old) groups. Both groups performed an incremental treadmill running test for the evaluation of maximal oxygen consumption (O2max), anaerobic threshold, and time to exhaustion. They started exercising at a treadmill speed of 2.7 km/h and an inclination of 10% gradient for 3 min, and the speed and inclination were gradually increased every 3 min until they were exhausted or fatigued volitionally. HRV was examined using the Polar heart rate monitor over a period of 5 min at rest in the supine position. Subsequently, the index of arterial stiffness was examined under the same condition. Our results revealed significant differences between the male and female athletes in O2max (men: 60.38 ± 8.98 mL/kg/min, women: 48.13 ± 7.72 mL/kg/min, p < 0.05), anaerobic threshold (men: 41.50 ± 7.26 mL/kg/min, women: 32.51 ± 6.19 mL/kg/min, p < 0.05), time to exhaustion (men: 902.15 ± 120.15 s, women: 780.56 ± 67.63 s, p < 0.05), systolic blood pressure (men: 125.27 ± 7.76 mmHg, women: 107.16 ± 11.09 mmHg, p < 0.05), and arterial stiffness index (men: 63.56 ± 12.55, women: 53.83 ± 8.03, p < 0.05). However, no significant differences in HRV measures were observed between the two groups. These findings suggested that the male badminton athletes demonstrated significantly higher aerobic capacity than did the female athletes, but there were no significant differences in HRV measures. The female athletes exhibited superior arterial function, compared with their male counterparts.

Effects of different types of exercise training on angiogenic responses in the left ventricular muscle of aged rats.

We evaluated angiogenic responses in the left ventricular muscle and aerobic capacity according to exercise type (aerobic, resistance, combined) in aged rats. In total, 24 male Sprague-Dawley rats (100weeks old) were used. To investigate the effect of regular training, the rats were divided into non-exercise (NE), aerobic exercise (AE), resistance exercise (RE), and combined exercise (CE) groups (six rats per group). Regular training tailored to each exercise type was performed for 8weeks (five times a week, 1h per day). After 8weeks of training, aerobic capacity was evaluated by a treadmill running test. Left ventricular muscle tissue was collected and the protein levels of angiogenesis indicators (eNOS, HIF-1α, PGC-1α, VEGF, FLK-1, Ang-1, Ang-2) were analyzed by Western blotting. Capillaries were observed by immunohistochemical staining for CD31. Body weight, heart weight, and heart/body weight ratio showed no difference among the groups. The AE and CE groups showed higher treadmill running capacity than the NE and RE groups. The eNOS, VEGF, HIF-1α, PGC-1α, and Ang-2 protein levels were significantly higher in the AE than NE group. The PGC-1α and FLK-1 protein levels were significantly higher in the RE than NE group. In addition, in the CE group, the eNOS, FLK-1, and PGC-1α protein levels were significantly higher than in the NE group. Expression of CD31 in cardiac tissue was higher in the AE and CE groups than in the other groups. Taken together, the results suggest that regular exercise training, irrespective of exercise type, might improve cardiovascular function by inducing angiogenic responses in the aged myocardium; however, AE may be the most effective.

Comparison of the Cardiovascular Effects of Extreme Psychological and Physical Stress Tests in Male Soccer Players.

Background: The purpose of our study was to compare the physiological effects of extreme physical and psychological stress tests in male soccer players, since these two types of stress apply to athletes with high performance requirements. Methods: A total of 63 healthy male soccer players participated in this study, all of whom underwent both of the tests. A physical stress test was carried out in an exercise physiology laboratory, where subjects completed an incremental treadmill running test to full exhaustion, and a psychological test was performed in a military tactical room, where subjects met a street offence situation. Heart rate variability (HRV) and blood pressure (BP) were recorded directly before, immediately after, and 30 min after the stress tests. Results: The majority of HRV indices changed significantly in both stress protocols. Inverse, significant changes (positive for the physical test, negative for the psychological test, p < 0.001) were found when comparing the alterations of HRV indices between the tests. Significant differences were found in the changes in systolic (p = 0.003) and diastolic (p < 0.001) BP between the test protocols, and also between the baseline and post-test measurements (p < 0.001). Conclusion: Both HRV and BP are sensitive physiological parameters to measure the impact of extreme physical and/or psychological stress

Influence of Chronic Nitrate-Rich Beetroot Juice Supplementation on the Endurance Performance of Active Winter Triathletes: A Randomized Controlled Trial

Objective: The impact of high-nitrate beetroot juice (BRJ) supplementation has seen a recent explosion of interest in sports science. This study examined the potential influence of 7-day BRJ supplementation on the endurance performance of winter triathletes. Methods: Eighty young active winter triathletes (44 males, age = 21.50 ± 1.15 yrs; 36 females, age = 20.66 ± 1.45 yrs) participated in this study and were provided with either BRJ (6.5 mmol NO3 −/70 mL) or a placebo (PL, 0.065 mmol NO3 −/70 mL) for 7 days (a dose of ×3 per day) in a randomized, double-blind design. The athletes then completed a submaximal treadmill run, intraday cycling exhaustion testing, and a 10-km cross country (XC) skiing competition on the second day. Results: There was a significant decrease in the oxygen uptake, respiratory exchange ratio, and blood lactic acid level (p < 0.05) between the BRJ and PL treatment groups during V 3 speed running (males: 13.3 km·h−1, females: 11.6 km·h−1). BRJ treatment also remarkably increased the time to exhaustion (TTE) during cycling exhaustion testing (males: p = 0.02, females: p = 0.04). No significant differences were observed in medium- or low-speed submaximal treadmill runs and 10-km XC skiing performance. Conclusions: One week of daily nitrate-rich BRJ supplementation improved running economy at high speed during the submaximal treadmill running test and extended the TTE of athletes during cycling exhaustion testing. However, BRJ supplementation did not improve the performance in 10-km on-snow time trials in XC skiing. Regarding nutritional strategies to improve endurance performance in exercise training and competition, these results should be carefully considered owing to the different motor skill levels and competitive abilities of participants.

Saliva biomarkers for Alzheimer’s disease risk in a rat model of low and high intrinsic exercise capacity

AbstractBackgroundIdentifying a natural‐occurring animal model for Alzheimer's Disease (AD) and a non‐invasive early AD diagnostic are significant AD research challenges. Previously, we developed rat models by selectively breeding for low and high intrinsic exercise capacity. We found that compared to High Capacity Runners (HCR), Low Capacity Runners (LCR) have a reduced lifespan and greater risk for cardiovascular disease, diabetes, and obesity.1 LCR exhibit neurodegeneration, impaired memory, and decreased hippocampal neurogenesis. Saliva is a relatively new AD‐associated research area, and as a bioanalytic,2 is an important extension of protein changes in the autonomic nervous system and immune response. Our goal is to determine whether salivary biomarkers link with exercise capacity and brain health in LCR and HCR rats.MethodWe studied three‐generations of female rats (6 months: 9 LCR, 10 HCR), (20 months: 8 LCR, and 8 HCR), and (26 months: 7 LCR, 6 HCR). We assessed exercise capacity using a treadmill running test and cognitive function using a Y‐maze. Salivary gland weight and salivary flow rate (SFR) of a submandibular gland (SMG) were measured and compared. The acinar cells proliferation of SMG was assessed by IHC using PCNA. Biomarkers for p‐tau ser610 and amyloid‐beta were investigated in hippocampus tissue, saliva, and plasma using ELISA.ResultThe LCR and HCR groups were significantly different for maximal treadmill running distance and time spent in novel arm of the Y‐Maze. The SFR and acinar cell proliferation were higher in HCR. The size and mass of SMG were bigger in LCR rats. Levels of p‐tau in saliva and plasma were markedly greater in LCR than HCR, but no differences in the hippocampus. There was no difference between the two groups in the hippocampus or saliva regarding amyloid‐beta levels. However, it was significantly increased in plasma in the LCR group compared with the HCR group.ConclusionTaken together, the findings of this study provide experimental evidence that saliva biomarkers are significantly increased in the LCR group compared with the HCR group. This is the first study using novel and unexplored preclinical rat models that combines exercise capacity with AD risk by utilizing saliva biomarkers.

The ability of a submaximal cycle ergometer test to detect longitudinal changes in VO2max

BackgroundThe purpose of the present study was to examine the ability of a submaximal cycling test to detect longitudinal changes in maximal oxygen uptake (VO2max) and examine the conformity between changes in measured and estimated VO2max over a time span of 5–8 years.MethodsA total of 35 participants (21 men and 14 women), aged 29 to 63 years, performed the Ekblom-Bak (EB) submaximal cycle test for estimation of VO2max and a maximal treadmill running test for direct measurement of VO2max. The baseline tests were conducted between 2009 and 2012, and the follow-up tests were completed 5 to 8 years later. Pearson’s coefficient of correlation (r) and paired sample t-test were used to analyse the association between change in measured and estimated VO2max. Random and systematic errors between the measured and estimated VO2max were evaluated using Bland-Altman plots. Repeated measures ANOVA were used to test differences between changes over time.ResultsThere was no significant change in mean measured VO2max between baseline and follow-up (p = 0.91), however large individual variations were noted (− 0.78 to 0.61 L/min). The correlation between individual change in measured and estimated VO2max was r = 0.75 (p < 0.05), and the unstandardised B-coefficient from linear regression modelling was 0.88 (95% CI 0.61 to 1.15), i.e., for each litre of change in estimated VO2max, the measured value had changed 0.88 L. The correlation between baseline and follow-up errors (the difference between estimated-measured VO2max at each occasion) was r = 0.84 (p < 0.05). With regard to the testing procedure, repeated measures ANOVA revealed that there was no significant difference between the group who exercised at the same work rates at baseline and follow-up (n = 25), and those who required a change in work rate (n = 10).ConclusionsThe EB test detected a change in VO2max with reasonably good precision over a time span of 5–8 years. Further studies are needed to evaluate if the test can be used in clinical populations and in subjects with different medications.

Intrinsic aerobic capacity, sex, and brain aging: Determinants of Alzheimer's disease risk.

Low aerobic capacity (or cardiorespiratory fitness) is strongly associated with all-cause mortality and risk for Alzheimer's disease (AD). Individuals with early dementia and AD have lower aerobic capacity compared to age-matched controls. The mechanism by which low aerobic capacity influences AD are unknown but are suggestive of an impairment in mitochondrial energetics. Here we used rats selectively bred over several generations to have intrinsic low or high exercise capacity. Rats were bred based on low or high capacity to complete an aerobic treadmill running test resulting in rats with robustly different intrinsic aerobic capacity despite being maintained sedentary. We examined mitochondrial function, RNA sequencing, and markers of AD in brain tissue from 18-month-old male and female Low Capacity Runners (LCR) and High Capacity Runners (HCR) from generation 43 of selection. We found lower mitochondrial respiration in brains of female LCR rats for complex I-, ADP-, uncoupled-, and complex II-driven flux when compared to LCR males. Brain Complex I driven respiratory flux was reduced in LCR females when compared to HCR females. No differences were observed in complex I or citrate synthase (CS) Vmax but complex IV Vmax was lower in LCR males versus HCR males. Female LCR rats had higher Aβ42 while both male and female LCR rats had higher phosphorylated tau at threonine 181 in whole brain homogenates. RNAseq revealed a greater effect of sex on gene expression than strain (HCR vs. LCR). However, FOXO signaling, axonal guidance, ubiquitination, and protein phosphorylation pathways were greater in male LCR versus male HCR rats. Glutamate NMDA receptor subunit 3A (Grin3a) and Transcription factor 7-like 2 (TCF7L2) were identified as coordinating numerous downstream targets with IPA analysis in male LCR rats. RNA sequencing outcomes suggest downregulation of AMPK signaling in female LCR rats. These data support a strong relationship between intrinsic aerobic capacity, sex, and markers of brain mitochondrial function and AD in late-middle aged HCR and LCR rats.