Blood Lactate Concentration Research Articles

Expanding the phenotypic and biochemical spectrum of NDUFAF3-related mitochondrial disease

Recessive variants in NDUFAF3 are a known cause of complex I (CI)-related mitochondrial disorders (MDs). The seven patients reported to date exhibited severe neurologic symptoms and lactic acidosis, followed by a fatal course and death during infancy in most cases.We present a 10-year-old patient with a neurodevelopmental disorder, progressive exercise intolerance, dystonia, basal ganglia abnormalities, and elevated lactate concentration in blood. Trio-exome sequencing revealed compound-heterozygosity for a pathogenic splice-site and a likely pathogenic missense variant in NDUFAF3. Spectrophotometric analysis of fibroblast-derived mitochondria demonstrated a relatively mild reduction of CI activity. Complexome analyses revealed severely reduced NDUFAF3 as well as CI in patient fibroblasts. Accumulation of early sub-assemblies of the membrane arm of CI associated with mitochondrial complex I intermediate assembly (MCIA) complex was observed. The most striking additional findings were both the unusual occurrence of free monomeric CI holding MCIA and other assembly factors.Here we discuss our patient in context of genotype, phenotype and metabolite data from previously reported NDUFAF3 cases. With the atypical presentation of our patient, we provide further insight into the phenotypic spectrum of NDUFAF3-related MDs. Complexome analysis in our patient confirms the previously defined role of NDUFAF3 within CI biogenesis, yet adds new aspects regarding the correct timing of both the association of soluble and membrane arm modules and CI-maturation as well as respiratory supercomplex formation.

Subtetanic neuromuscular electrical stimulation can maintain Wingate test performance but augment blood lactate accumulation.

Concentration- and time-dependent effect of lactate on physiological adaptation (i.e., glycolytic adaptation and mitochondrial biogenesis) have been reported. Subtetanic neuromuscular electrical stimulation (NMES) with voluntary exercise (VOLES) can increase blood lactate accumulation. However, whether this is also true that VOLES can enhance the blood lactate accumulation during sprint exercise is unknown. Thus, we investigated whether VOLES before the Wingate test can enhance blood lactate accumulation without compromising Wingate exercise performance. Fifteen healthy young males (mean [SD], age: 23 [4] years, body mass index: 22.0 [2.1] kg/m2) volunteered. After resting measurement, participants performed a 3-min intervention: VOLES (NMES with free-weight cycling) or voluntary cycling alone, which matched exercise intensity with VOLES (VOL, 43.6 [8.0] watt). Then, they performed the Wingate test with 30min free-weight cycling recovery. The blood lactate concentration ([La]b) was assessed at the end of resting and intervention, and recovery at 1, 3, 5, 10, 20, and 30min. [La]b during intervention was higher with VOLES than VOL (P = 0.011). The increase in [La]b after the Wingate test was maintained for longer with VOLES than VOL at 10- and 20-min recovery (P = 0.014 and 0.023, respectively). Based on the Wingate test, peak power, mean power, and the rate of decline were not significantly different between VOLES and VOL (P = 0.184, 0.201, and 0.483, respectively). The combination of subtetanic NMES with voluntary exercise before the Wingate test has the potential to enhance blood lactate accumulation. Importantly, this combined approach does not compromise Wingate exercise performance compared to voluntary exercise alone.

Are slaughterhouse-obtained livers suitable for use in ex vivo perfusion research?

The success of the ex vivo machine perfusion of pig livers used for preclinical research depends on organ quality and availability. In this study, we investigated whether livers obtained from slaughterhouses are suitable and equivalent to livers obtained from laboratory pigs. Livers were obtained from slaughterhouse pigs stunned by electrocution or CO2 inhalation and from laboratory pigs. For the latter group, 45 minutes of warm ischemia was mimicked for a subgroup, ensuring a valid comparison with slaughterhouse-derived livers. Livers from CO2-stunned pigs showed lower indocyanine green clearance and bile production, higher blood lactate and potassium concentrations, and higher alanine aminotransferase activities than electrically stunned pigs. Furthermore, livers from electrically stunned pigs, and livers from laboratory pigs, subjected or not to warm ischemia, showed similar performance in terms of perfusion and metabolism. For an ex vivo liver model generated using slaughterhouse pigs, electrical stunning is preferable to CO2 stunning. Livers from electrically stunned slaughterhouse pigs performed similarly to laboratory pig livers. These findings support the use of livers from electrically stunned slaughterhouse pigs, which may therefore provide an alternative to livers obtained from laboratory pigs, consistent with the principle of the 3Rs.

Using Multivariate Data Analysis to Project Performance in Biathletes and Cross-Country Skiers.

To determine whether competitive performance, as defined by International Biathlon Union (IBU) and International Ski Federation (FIS) points in biathlon and cross-country (XC) skiing, respectively, can be projected using a combination of anthropometric and physiological metrics. Shooting accuracy was also included in the biathlon models. Data were analyzed using multivariate methods from 45 (23 female and 22 male) biathletes and 202 (86 female and 116 male) XC skiers who were all members of senior national teams, national development teams, or ski-university or high school invite-only programs (age range: 16-36y). Anthropometric and physiological characteristics were assessed via dual-energy X-ray absorptiometry and incremental roller-ski treadmill tests, respectively. Shooting accuracy was assessed via an outdoor standardized testing protocol. Valid projective models were identified for female biathletes' IBU points (R2 = .80/Q2 = .65) and female XC skiers' FIS distance (R2 = .81/Q2 = .74) and sprint (R2 = .81/Q2 = .70) points. No valid models were identified for the men. The most important variables for the projection of IBU points were shooting accuracy, speeds at blood lactate concentrations of 4 and 2mmol·L-1, peak aerobic power, and lean mass. The most important variables for the projection of FIS distance and sprint points were speeds at blood lactate concentrations of 4 and 2mmol·L-1 and peak aerobic power. This study highlights the relative importance of specific anthropometric, physiological, and shooting-accuracy metrics in female biathletes and XC skiers. The data can help to identify the specific metrics that should be targeted when monitoring athletes' progression and designing training plans.

Improved interference control after exercise with blood flow restriction and cooling is associated with but not mediated by increased lactate

BackgroundTo evaluate the effects of recumbent sprint interval exercise with and without blood flow restriction and body cooling on interference control and whether the changes in interference control can be explained by the changes in blood lactate. Methods85 participants (22 SD 3 years old) completed 1 familiarization visit and then 5 experimental visits in a randomized order: exercise only (Ex), exercise with blood flow restriction (ExB), exercise with cooling (ExC), and exercise with blood flow restriction and cooling (ExBC), and non-exercise control (Con). Measurements of blood lactate and the Stroop Color Word Test were performed before and after exercise. Each bout began with a 15-minute low-moderate intensity warm-up, followed by five 20-second “all out” sprints separated by 40 s of active recovery. Bayes Factors (BF10) quantified evidence for or against the null hypothesis. Within-subject mediation analysis quantified the indirect effect of changes in blood lactate (mediator) on the change in interference control (each exercise condition vs. Con). Results: Bayesian pairwise comparisons found that only ExC [σ: -0.37 (-0.59, -0.15)] and ExBC [σ: -0.3 (-0.53, -0.09)] produced changes in incongruent reaction time different from that of Con. There was also evidence that all exercise conditions increased blood lactate (BF10 = 8.65e+29 – 1.9e+32) and improved congruent reaction time (BF10 = 4.01 – 15.371) compared to that of Con. There was no evidence to show that changes in lactate mediated the change in incongruent reaction time. ConclusionsBoth exercise with body cooling and when body cooling was combined with blood flow restriction presented favorable changes in incongruent reaction time (a marker of interference control), which might not be explained by the changes in systemic blood lactate concentration.

Long- and Short-Term High-Intensity Interval Training on Lipid Profile and Cardiovascular Disorders in Obese Male Adolescents.

This study investigated the effects of short-term and long-term periods (8 and 16 weeks) of high-intensity interval training (HIIT) on cardiovascular components, blood lipids, and 6-min walking test performance in obese young boys (age = 16.2 ± 0.7) with >34% body fat. The participants were split into two groups: severe obesity (SOG; n = 17) and moderate obesity (MOG; n = 16). All participants performed on a cycle ergometer for 16 weeks (3 times per week) of HIIT at 100% peak power output at the ventilatory threshold and recovered at 50% of peak power. Except for BMI, both groups improved all body composition measures after 16 weeks, with a higher percentage of change (Δ) in SOG. The 6-min walking test increased in both groups (p < 0.001). Furthermore, cardiovascular variables, blood lactate concentration at rest and after 5-min post-exercise, blood lipids, and insulin concentrations improved significantly in both groups. After 16 weeks, MOG significantly improved in HRpeak, blood glucose concentration, and rating of perceived exertion (RPE), but the percentage of change (Δ) was higher in SOG for all the other variables. SOG showed a higher (Δ) waist-to-hip ratio, maximum heart rate, resting heart rate, systolic blood pressure, blood lactate at 5-min post-exercise, and triglyceride concentrations after 8 and 16 weeks of training. In conclusion, a long-term HIIT program appears to be an appropriate training approach for obese boys with extra body fat. However, considering the RPE values, short-duration training sessions should be planned.

THE EFFECT OF FRACTIONATED RED BEETROOT JUICE ON PERFORMANCE AND OVERALL HEALTH OF A HIGH-PERFORMANCE ATHLETES

Over the past 20 years, nitric oxide has become the turning point in athlete physiology and medical research. It has been observed in scientific studies that there are very different protocols for the use of nitrates (red beetroot juice) and different research methodology and results. The most effective solutions for improving the performance of athletes are still being sought. The purpose of this research is to investigate the performance and overall health of a high-performance athlete after consuming fractionated red beetroot juice. The investigation is a one-case study. The respondent is a high-class athlete - track and field (middle and long distance), 20 years old. Three tests were performed in laboratory conditions with an interval of one week. The first test was without the use of fractionated red beetroot juice, the second test after a single dose, and the third after 7 days of use. The research used an interview of the respondent, cardio pulmonary exercise testing measuring device "Vyntus CPX" with gas analysis on a bike ergometer and determination of blood lactate concentration. In the experiment, the athlete's VO2max improved during each test, after one dose by 9%, and after 7 days of use by 13% from the first test. The physical overall health at the end of the test worsened each time, but in the previous tests, where fractionated red beetroot juice was used, a faster recovery of the athlete's working capacity after exercise was observed.

Heart Rate-Blood Lactate Profiling in World-Class Biathletes During Cross-Country Skiing: The Difference Between Laboratory and Field Tests.

To identify differences in heart rate (HR) and concentration of blood lactate ([La]) relationships between laboratory- and field-based skate-roller-skiing tests. Fourteen world-class biathletes (8 women, 6 men) completed a laboratory- and field-based roller-skiing test using the skate technique. The laboratory-based test comprised 5 to 7 submaximal steps at a fixed incline and speed on a roller-skiing treadmill. The field-based test comprised 5 steps on a course where the final hill was designed to mimic the conditions of the laboratory test. HR and [La] were measured for each step. The HR associated with 2 mmol·L-1 (HR@2 mmol) and 4 mmol·L-1 (HR@4 mmol) of [La] was calculated using an interpolation method. A 1-way analysis of variance and Bland-Altman analyses with 95% limits of agreement (LoA) were used to determine if test type influenced HR@2 mmol or HR@4 mmol. A second-order polynomial was fitted to group-level data to highlight the HR-[La] relationships for laboratory- and field-based tests. HR@2 mmol was lower for field tests than for laboratory tests (mean bias: 1.9%HRmax; 95% LoA: -4.5 to +8.3%HRmax; P < .001). HR@4 mmol was also lower for field tests compared to laboratory tests (mean bias: 2.4%HRmax; 95% LoA: -1.2 to +6.0%HRmax; P < .001). On the group level, the lactate threshold occurred at a lower HR during roller skiing in the field compared to the laboratory. The findings from this study confirm that for a given HR, [La] was greater in field- compared with laboratory-based conditions. These results might have implications for how coaches define training-intensity "zones" during skate roller skiing based on laboratory tests.

Bioenergetic Analysis and Fatigue Assessment During the Fran Workout in Experienced Crossfitters.

To quantify the physiological demands and impact of muscle function t of the Fran workout, one of the most popular CrossFit benchmarks. Twentyexperienced CrossFitters-16 male: 29 (6)years old and 4 female: 26 (5)years old- performed 3 rounds (with 30-s rests in between) of 21-21, 15-15, and 9-9 front squats to overhead press plus pull-up repetitions. Oxygen uptake and heart rate were measured at baseline, during the workout, and in the recovery period. Rating of perceived exertion, blood lactate, and glucose concentrations were assessed at rest, during the intervals, and in the recovery period. Muscular fatigue was also monitored at rest and at 5 minutes, 30 minutes, and 24 hours postexercise. Repeated-measures analysis of variancewas performed to compare time points. Aerobic (52%-29%) and anaerobic alactic (30%-23%) energy contributions decreased and the anaerobic lactic contribution increased (18%-48%) across the 3 rounds of the Fran workout. Countermovement jump height decreased by 8% (-12 to -3) mean change (95% CI), flight duration by 14% (-19 to -7), maximum velocity by 3% (-5 to -0.1), peak force 4% (-7 to -0.1), and physical performance (plank prone 47% [-54 to -38]) were observed. It appears that the Fran workout is a physically demanding activity that recruits energy from both aerobic and anaerobic systems. This severe-intensity workout evokes substantial postexercise fatigue and corresponding reduction in muscle function.

고출력 적외선 조사기를 위한 구동회로 설계와 검증에 대한 연구

This study is about a high-power infrared irradiator. In the case of athletes who perform intense exercise, muscle fatigue occurs due to blood lactate concentration and CK. In order to reduce such muscle fatigue, various methods for reducing blood lactate concentration and CK have been studied, and it has been confirmed through several papers that LEDT is effective. In order to obtain the effect through LEDT, energy of 4J/m2 must be supplied in a short time. To this end, a high-power LED driving circuit was designed to supply the necessary light energy in a short time. It was confirmed that a high light output of 102 W/m2 could be obtained by applying a high current. Through this, it seems that blood lactate concentration and CK reduction can be obtained, and experiments to verify this are also planned.

Assessing the impact of essential oil blends as antibiotic alternatives on nutritional and metabolic parameters in non-forage-based diet-fed Nellore steers

Essential oils (EO) are antimicrobials with the potential to replace conventional ones in ruminant diets. Despite the advantage of the EO serving markets that prohibit antibiotics in animal nutrition, the results that prove their effectiveness vary with the type of EO, dose, diet, etc. This study aimed to assess the effects of a blend of essential oil, based on cinnamaldehyde and diallyl disulfide, associated or not with antibiotics on nutritional and metabolic parameters for feedlot Nellore steers fed non-forage-based diet. Five Nellore steers were distributed in a 5×5 simple Latin square design. The treatments assessed were a basal no-roughage diet with the inclusion of monensin (MON), monensin + virginiamycin (MV), monensin + blend of EO (MEO25), monensin + blend of EO (MEO35), and a blend of essential oil (EO). Feed, orts, feces, ruminal fluid, blood, and urine samples were utilized to assess the intake, digestibility, ruminal pH, ruminal NH3, nitrogen balance, microbial nitrogen synthesis, fecal cortisol metabolites, blood glucose, and D and L-lactate. No difference (P &gt; 0.05) has been observed in additives in intake, nutrient digestibility, and ingestive behavior. There was a trend (P = 0.0553) of the effect of additives on ruminal pH, and the MV presented the highest value. No difference (P &gt; 0.05) for the ruminal NH3, microbial N synthesis, and nitrogen balance concentration was also verified. The blood glucose and blood lactate concentration were not affected (P &gt; 0.05) by additives. The blend of essential oils based on cinnamaldehyde and diallyl disulfide could then be indicated in replacement or association with antibiotics in a non-forage-based diet for Nellore steers.

Comparison of Norepinephrine &amp; Terlipressin vs Norepinephrine Alone for Management for Septic Shock

Introduction: Sepsis is a clinical syndrome that has physiologic, biologic, and biochemical abnormalities caused by a dysregulated inflammatory response to infection. The present study aimed to estimate the dose of injection of norepinephrine in micrograms/ kg/min after 12 hours of starting the vasopressor infusion to keep an MAP of above 65 mm Hg. Materials &amp; Method: The study was done for the period of two years. Patients who were 18 years and above; who were diagnosed with septic shock during their ICU course and whose relatives gave informed written consent were included in the study. Result: Total of 12 patients were lost during the study period and so in total 100 patients were enrolled for the study. Both the groups were comparable with respect to the MAP (p = 0.655). The norepinephrine dose in group I vs group II at 12 hours was found to be 0.163 ± 0.089 vs 0.396 ± 0.18 μg/kg/min (p &lt;0.001). Reduction in blood lactate concentration in 12 hours was significantly higher in group I [1.479 ± 1.46] than group II [0.08 ± 1.50] mmol/L (p = 0.002). Increase in the urine output of the patients in 12 hours in Group I [0.72 ± 0.44] than group II [0.47 ± 0.460] mL/kg/hour (p = 0.001). Conclusion: A low-dose continuous infusion of terlipressin may have a significant role in ensuring better organ perfusion, preventing renal injury, and improving the SOFA score of the patients when used in adjunct to norepinephrine, early in the management of septic shock.

Wheelchair rugby players maintain sprint performance but alter propulsion biomechanics after simulated match play.

The study aimed to explore the influence of a sports-specific intermittent sprint protocol (ISP) on wheelchair sprint performance and the kinetics and kinematics of sprinting in elite wheelchair rugby (WR) players with and without spinal cord injury (SCI). Fifteen international WR players (age 30.3 ± 5.5 years) performed two 10-s sprints on a dual roller wheelchair ergometer before and immediately after an ISP consisting of four 16-min quarters. Physiological measurements (heart rate, blood lactate concentration, and rating of perceived exertion) were collected. Three-dimensional thorax and bilateral glenohumeral kinematics were quantified. Following the ISP, all physiological parameters significantly increased (p ≤ 0.027), but neither sprinting peak velocity nor distance traveled changed. Players propelled with significantly reduced thorax flexion and peak glenohumeral abduction during both the acceleration (both -5°) and maximal velocity phases (-6° and 8°, respectively) of sprinting post-ISP. Moreover, players exhibited significantly larger mean contact angles (+24°), contact angle asymmetries (+4%), and glenohumeral flexion asymmetries (+10%) during the acceleration phase of sprinting post-ISP. Players displayed greater glenohumeral abduction range of motion (+17°) and asymmetries (+20%) during the maximal velocity phase of sprinting post-ISP. Players with SCI (SCI, n = 7) significantly increased asymmetries in peak power (+6%) and glenohumeral abduction (+15%) during the acceleration phase post-ISP. Our data indicates that despite inducing physiological fatigue resulting from WR match play, players can maintain sprint performance by modifying how they propel their wheelchair. Increased asymmetry post-ISP was notable, which may be specific to impairment type and warrants further investigation.

Analysis of the COVID-19 Lockdown Impact on Biological Parameters and Physical Performance in Football Players

The COVID-19 pandemic has caused significant changes in global sustainability, but specifically, this study analyses the impact of lockdown on health and behavior in the game of football. The 2020/2021 Italian football competitive season (indicated as “post-COVID”), taking place following an obliged lockdown and longer than the normal summery season break, was characterized by very short recovery times and was compared to the 2018–2019 “pre-COVID” season, which had a regular course. The comparisons were about anthropometric and hormonal responses, muscle damage, and the physical performance of players in the major league (Serie A), and were made considering two extreme points of the competitive seasons: before the preparatory period (T0) and at the end of the season (T1). Turning to the results, it is significant to note the following: (1) body fat percentage was lower at the start (T0) of the post-COVID season than at the start of the pre-COVID season. During both seasons, serum CK and LDH increased in T1 and were significantly higher in both T0 and T1 of the post-COVID season. (2) Cortisol and testosterone concentrations increased in both seasons from T0 to T1; however, in the post-COVID season, concentrations of both were higher than in the previous season. The testosterone to cortisol ratio increased at the end of the pre-COVID season, whilst strongly decreasing at T1 of the post-COVID season. (3) Blood lactate concentrations significantly decreased during the pre-COVID season but remained unchanged during the post-COVID season. We may conclude that the enforced suspension period and the consequent rapid resumption of all activities influenced the physical and physiological state of professional footballers.

Muscle oxygen saturation rates coincide with lactate-based exercise thresholds.

Monitoring muscle metabolic activity via blood lactate is a useful tool for understanding the physiological response to a given exercise intensity. Recent indications suggest that skeletal muscle oxygen saturation (SmO2), an index of the balance between local O2 supply and demand, may describe and predict endurance performance outcomes. We tested the hypothesis that SmO2 rate is tightly related to blood lactate concentration across exercise intensities, and that deflections in SmO2 rate wouldcoincide with established blood lactate thresholds (i.e., lactate thresholds 1 and 2). Ten elite male soccer players completed an incremental running protocol to exhaustion using 3-min work to 30s rest intervals. Blood lactate samples were collected during rest and SmO2 was collected continuously via near-infrared spectroscopy from the right and left vastus lateralis, left biceps femoris and the left gastrocnemius. Muscle O2 saturation rate (%/min) was quantified after the initial 60s of each 3-min segment. The SmO2 rate was significantly correlated with blood lactate concentrations for all muscle sites; RVL, r = -0.974; LVL, r = -0.969; LG, r = -0.942; LHAM, r = -0.907. Breakpoints in SmO2 rate were not significantly different from LT1 or LT2 at any muscle sites (P > 0.05). Bland-Altman analysis showed speed threshold estimates via SmO2 rate and lactate are similar at LT2, but slightly greater for SmO2 rate at LT1. Muscle O2 saturation rate appears to provide actionable information about maximal metabolic steady state and is consistent with bioenergetic reliance on oxygen and its involvement in the attainment of metabolic steady state.

Bispectral Index Monitor for Regulating Anesthetic Depth on Blood Glucose, Lactate Concentration and Intraoperative Stress Response in Patients Undergoing Craniocerebral Operation

Bispectral Index Monitor for Regulating Anesthetic Depth on Blood Glucose, Lactate Concentration and Intraoperative Stress Response in Patients Undergoing Craniocerebral Operation

Shock index is positively correlated with acute blood loss and negatively correlated with cardiac output in a canine hemorrhagic shock model.

To determine whether shock index (SI) positively correlates with percentage blood loss and negatively correlates with cardiac output (CO) in a canine hemorrhagic shock model and whether SI and metabolic markers may be used as end point targets for resuscitation. 8 healthy Beagles. Between September and December 2021, dogs underwent general anesthesia for experimental induction of hypotensive shock, with the total volume of blood removed, CO, heart rate, systolic blood pressure, base excess, blood pH, and concentrations of hemoglobin, lactate, ionized calcium recorded, and SI calculated at 4 time points (TPs): after anesthetic induction when the dog had been stable for 10 minutes (TP1), 10 minutes after the mean arterial pressure stabilized to a target of 40 mm Hg following jugular removal of up to 60% blood volume to induce hemorrhagic shock (TP2), 10 minutes after autotransfusion of 50% of the removed blood (TP3), and 10 minutes after autotransfusion of the remaining 50% of the removed blood (TP4). Mean SI increased between TP1 (1.08 ± 0.35) and TP2 (1.90 ± 0.73) and did not return to the prehemorrhage values for TP3 or TP4. SI correlated positively with percentage blood loss (r = 0.583) and negatively with CO (r = -0.543). An increase in SI may support diagnosis of hemorrhagic shock; however, SI cannot be used as the sole end point of resuscitation. Significant differences in blood pH, base excess, and lactate concentration suggested they may be useful markers of hemorrhagic shock and need for blood transfusion.

Exercise precision medicine for type 2 diabetes: Targeted benefit or risk?

Concurrent exercise and metformin administration may reduce the acute and chronic effects of exercise on glucose metabolism in the patients with type 2 diabetes (T2D). However, several studies suggest that combing metformin and exercise treatment may have neither additive effect nor even cause adverse effects in T2D patients. This case report aimed to highlight the challenges associated with prescribing exercise to type 2 diabetes patients undergoing metformin treatment. A 67-years old woman was followed-up for five months, including assessment of the acute and chronic glucose and lactate metabolism induced by concomitant exercise and metformin. The findings were four-fold: 1) During a high-intensity interval training bout, blood glucose systematically decreased, while blood lactate concentrations fluctuated randomly; 2) Basal blood lactate levels were well above 2 mmol/L on days with medication only; 3) Combined exercise and metformin administration induced additive effects on the normalization of glucose and 4) high levels of physical activity had a positive impact on the continuous glucose fluctuations, while decreased levels of physical activity induced a large fluctuation of glucose due to home confinement of an infectious disease caused by the SARS-CoV-2 virus. Our findings showed that when combined with exercise and metformin treatment for T2D patients, exercise may contribute to improving glycemic control while metformin may elevate lactate levels in the long term. The observed results underline the need to prescribe exercise and monitor lactate levels for reducing possible risks associated with metformin treatment and reinforce the importance of tailoring exercise therapy.

Stride-to-stride variability and fluctuations at intensities around lactate threshold in distance runners

Stride-to-stride variability and fluctuations in running have been widely investigated in relation to fatigue, injury, and other factors. However, no studies have examined the relationship of stride-to-stride variability and fluctuations with lactate threshold (LT), a well-known performance indicator for distance runners that represents the threshold at which fast-twitch muscle fibers are activated and the glycolytic system is hyperactivated. In this study, we examined a relationship between LT and stride-to-stride variability and fluctuations in trained middle- and long-distance runners (n = 33). All runners were asked to perform multistage graded exercise tests while wearing accelerometers on the upper surface of their shoes. The LT was determined by measuring blood lactate concentrations after each stage. Three gait parameters for each step were calculated based on the acceleration data: stride time (ST), ground contact time (CT), and peak acceleration (PA). The coefficient of variation (CV) and the long-range correlations (α) for each parameter were also calculated. The effects of the runner's group and the relative intensity for CV and α on gait parameters were evaluated using a two-way repeated measures analysis of variance. Although no significant effect was observed in the CV and α of ST, significant intensity main effects were observed for the CV and α of CT and PA. The lack of significant changes in ST might be the result of runners' adequate control of ST to minimize energy cost. All the parameters showing significant changes with increasing intensity decreased dramatically when they were close to LT. This might have been caused by an increase in physiological load near LT and be interpreted as a variation in motor control because of alternations in the mobilized muscle fibers and physiological changes around the LT. The α should be useful for non-invasive LT detection.

Cardiac Changes after Lactate-Guided Conditioning in Young Purebred Arabian Horses.

Cardiac adaptation to conditioning in horses was evaluated after empirical training based on trainers' experience. Twelve purebred Arabian horses, aged (mean ± SD) 28.42 ± 3.75 months, which did not perform any type of exercise prior to the research, were submitted to treadmill conditioning for six weeks. The conditioning program was based on the velocity run by the horse at which the blood lactate concentration, determined in an incremental exercise test (IET), reached 2 mmol/L (V2). The velocity at which the blood lactate concentration reached 4 mmol/L (V4) was also determined. The echocardiograms were performed at rest with pulsed-wave and tissue Doppler imaging in B- and M-modes. All procedures were carried out before and after the conditioning period. The results showed increases in V2 (from 5.2 ± 0.3 to 6.7 ± 0.4 m/s) and V4 (from 5.8 ± 0.4 to 7.6 ± 0.5 m/s) (p < 0.0001). There were also increases in the left ventricle internal diameter at diastole (LVIDd), left ventricle mass (LV mass), and stroke volume (SV), while no changes were observed in the LV free wall thickness and mean and relative wall thicknesses. The conditioning protocol, which was completed by all horses, proved to be safe and efficient, as it improved the aerobic capacity of the animals. Finally, the cardiac remodeling that occurred was mainly associated with the effect of physical training.