Blood Lactate Concentration Research Articles

Inspiratory muscles pre-activation in young swimmers submitted to a tethered swimming test: effects on mechanical, physiological, and skin temperature parameters

Inspiratory muscles pre-activation (IMPA) has been studied to improve subsequent performance in swimming. However, the effects of IMPA on various parameters in swimmers are still unknown. Therefore, this study aimed to investigate the effects of IMPA on the mechanical parameters, physiological responses, and their possible correlations with swimming performance. A total of 14 young swimmers (aged 16 ± 0 years) underwent a 30-s all-out tethered swimming test, preceded or not by IMPA, a load of 40% of the maximal inspiratory pressure (MIP), and with a volume of 2 sets of 15 repetitions. The mechanical (strength, impulse, and fatigue index) and physiological parameters (skin temperature and lactatemia) and the assessment of perceived exertion and dyspnea were monitored in both protocols. The IMPA used did not increase the swimming force, and skin temperature, decrease blood lactate concentration, or subjective perception of exertion and dyspnea after the high-intensity tethered swimming exercises. Positive correlations were found between mean force and blood lactate (without IMPA: r = 0.62, P = 0.02; with IMPA: r = 0.65, P = 0.01). The impulse was positively correlated with blood lactate (without IMPA: r = 0.71, P < 0.01; with IMPA: r = 0.56, P = 0.03). Our results suggest that new IMPA protocols, possibly with increased volume, should be developed in order to improve the performance of young swimmers.

Use of renin versus lactic acid as tissue perfusion biomarkers for mortality prediction in hypotensive critically Ill patients

ABSTRACT Background Exploring a biomarker with enhanced sensitivity and specificity for tissue perfusion may facilitate the timely identification of circulatory collapse, and enable more precise resuscitation efforts. Objective The objective of this study was to ascertain the correlation between whole blood lactate versus plasma renin concentration being a biomarker of tissue perfusion and predictor of mortality among hypotensive critically ill patients. Methods This prospective, observational cohort study enrolled 84 hypotensive critically ill patients. Plasma renin concentration and blood lactate were measured at enrollment, 24, 48, and 72 hours. The primary outcome is the correlation between the recorded renin, lactate concentrations and mortality rate during hospitalization. Results The mean plasma renin concentration at enrollment was 61.95 pg/ml in survivors, and 104.45 pg/ml in non-survivors (p = <0.001). The non-survivors exhibited a significant boost in plasma renin concentration after 48 and 72 hours, opposed to the survivors (112 vs 40.89, and 106.64 vs 28.85 pg/ml) respectively. There was a significant positive correlation between plasma renin, blood lactate concentrations and patient mortality (r = 0.389 & 0.601) respectively. Conclusion Plasma renin and whole blood lactate had positive correlation to mortality, yet plasma renin revealed superior diagnostic accuracy over blood lactate for mortality prediction in hypotensive critically-ill patients. Trial registration The protocol of this study can be obtained on ClinicalTrials.gov with the id NCT05810415.

Physiological Responses and Performance during an Integrated High-Intensity Interval Aerobic and Power Training Protocol.

This study compared the acute physiological responses and performance changes during an integrated high-intensity interval aerobic and power protocol. Sixteen moderately trained athletes (age: 20.1 ± 2.2 years, body height: 180.0 ± 6.5 cm, body mass: 75.7 ± 6.4 kg, VO2max: 55.8 ± 4.3 mL/kg/min) performed a 2 × 6 min interval training protocol with 2 min passive recovery between sets on two different occasions in random and counterbalanced order. Each 6 min set included repeated periods of 15 s exercise interspersed with 15 s passive rest. On one occasion (RUN), all exercise periods included running at 100% of maximal aerobic speed, while on the other occasion an integrated protocol was used (INT) in which each of the two 6 min sets included 4 × 1.5 min periods of running exercise at 100% of maximal aerobic speed in combination with jumping (i.e., 2 × 15 running with 15 s rest and 1 × 15 s drop jumping with 15 s rest). Time spent above 85% HRmax was two-fold higher in INT compared to RUN (8.5 ± 3.6 vs. 4.3 ± 3.9 min, respectively, p = 0.0014). Interestingly, heart rate increased above 95% HRmax only in INT and almost no time was spent above 95% HRmax in RUN (1.4 ± 1.9 vs. 0.1 ± 0.2 min, respectively, p = 0.008). Blood lactate concentration at the end of the second set of INT was higher than RUN (7.3 ± 3.2 vs. 4.6 ± 2.7 mmol/L, p = 0.002). Countermovement jump was higher in INT after the end of second set by 6.4% (p = 0.04), 6.7% (p = 0.04), 7.8% (p < 0.01) and 7.3% (p < 0.001), at 2, 6 and 8 min after set 2. In conclusion, the comparison between INT and RUN shows that INT not only elicits higher physiological and metabolic responses, but also acutely enhances neuromuscular performance for at least 8 min after the end of exercise. The integrated running/jumping high-intensity interval exercise approach could be a very useful and time efficient method for strength and conditioning coaches, especially in team sports, in which the time available for the improvement of physical parameters is limited.

A comparison of physiological and perceptual responses to fixed‐power and perceptually regulated cycling with and without blood flow restriction in trained cyclists

AbstractThis study compared physiological and perceptual responses between cycling prescribed using fixed‐power (PWR) and fixed rating of perceived exertion (RPE), when performed with blood flow restricted (BFRPWR and BFRRPE) and unrestricted (CONPWR and CONRPE). Endurance cyclists/triathletes cycled for 10 min in four separate randomized conditions; that is, two methods of prescribed exercise intensity (power at the first ventilatory threshold or RPE matched to CONPWR) combined with two occlusion levels (with BFR or without). Cardiorespiratory and perceptual variables were recorded every 2 min. Blood lactate concentration was measured pre‐, immediately and 2‐min postexercise. Power output during BFRRPE was lower than CONRPE (−13 ± 13%). The greatest physiological and perceptual responses were achieved during BFRPWR. Heart rate during BFRRPE was not different compared with CONPWR, yet was greater than CONRPE (+4 ± 11%). Muscular discomfort during BFRRPE was greater than CONPWR (+43 ± 18%) and CONRPE (+65 ± 58%). Cuff pain was greater during BFRPWR than BFRRPE (+14 ± 21%). Blood lactate concentration was not different between BFRRPE, CONPWR, and CONRPE at any timepoint. The reduction in power (fixed‐RPE trials; BFR minus unrestricted) correlated with changes in the respiratory rate (r = 0.85, confidence intervals [CI] = 0.51, 0.96) and postexercise lactate (r = 0.75, CI = 0.27, 0.93) but not muscular discomfort (r = 0.18, CI = −0.47, 0.71). Cardiorespiratory and metabolic stress, muscular discomfort, and cuff pain likely mediated self‐regulating fixed‐RPE cycling with BFR. While cycling with BFR at a fixed‐RPE resulted in less physiological stress compared to BFRPWR, it still provided a heightened level of physiological stress, with less pain and discomfort. As such, fixed‐RPE can be a suitable alternative for prescribing BFR to trained cyclists.

Metabolic, cognitive and neuromuscular responses to different multidirectional agility-like sprint protocols in elite female soccer players – a randomised crossover study

PurposeResistance to fatigue is a key factor in injury prevention that needs to be considered in return-to-sport (RTS) scenarios, especially after severe knee ligament injuries. Fatigue should be induced under game-like conditions. The SpeedCourt (SC) is a movement platform for assessing multidirectional sprint performance, typical of game-sports, due to change-of-direction movements in response to a visual stimulus. Designing adequate fatigue protocols requires the suitable arrangement of several loading variables such as number of intervals, sprint distance or work/relief ratio (W:R). Therefore, this study analysed the acute fatigue effects of different SC protocols on metabolic load, cognitive function and neuromuscular performance.MethodsEighteen female soccer players (mean ± SD; age: 23.1 ± 4.6 years) of the 1st German Division participated in this randomised, crossover study. Using a random allocation sequence, players completed four volume-equated protocols differing in W:R and sprint distance per interval (P1:12 × 30 m, W:R = 1:2 s; P2:12 × 30 m, W:R = 1:3 s; P3:18 × 20 m, W:R = 1:2 s; P4:18 × 20 m, W:R = 1:3 s). Pre- and post-exercise, metabolic load was measured per blood lactate concentration (BLaC), cognitive function per reaction time (RT), and neuromuscular performance including multiple rebound jumps (MRJ height, primary outcome variable; Reactive Strength Index, RSI) and 5 m sprint times (SP5).ResultsRepeated-measures ANOVA revealed significant main time effects (p < .05) with improved performance post-exercise in RT (504 vs. 482 ms, d = 1.95), MRJ height (24.0 vs. 24.8 cm, d = 0.77), RSI (1.39 vs. 1.43, d = 0.52), and SP5 (1.19 vs. 1.17 s, d = 0.56). There was significant main time (p < .001) and time x protocol interaction effects in BLaC (p < .001). P1 induced higher BLaC values (4.52 ± 1.83 mmol/L) compared to P2 (3.79 ± 1.83 mmol/L; d = 0.74) and P4 (3.12 ± 1.83 mmol/L; d = 1.06), whereas P3 (4.23 ± 1.69 mmol/L) elicited higher BLaC values compared to P4 (d = 0.74).ConclusionAll protocols caused an improved cognitive function and neuromuscular performance. The former may be related to enhanced noradrenergic activation or exercise specificity which induced an improved stimulus processing. The latter may be explained by a possible post-activation performance enhancement effect on jump and sprint performance. A shorter relief duration in W:R as opposed to sprint distance per interval produced higher BLaC values. The protocols may serve as reference data for improved RTS decision-making in elite female soccer players.Trial registrationDeutsches Register Klinischer Studien (DRKS), No.: DRKS00033496, Registered 19. Februar 2024, Retrospectively Registered.

Associations between objective measures of performance-related characteristics and perceived stress in young cross-country skiers during pre-season training

ABSTRACT Monitoring performance-related characteristics of athletes can reveal changes that facilitate training adaptations. Here, we examine the relationships between submaximal running, maximal jump performance (CMJ), concentrations of blood lactate, sleep duration (SD) and latency (SL), and perceived stress (PSS) in junior cross-country skiers during pre-season training. These parameters were monitored in 15 male and 14 females (17 ± 1 years) for the 12-weeks prior to the competition season, and the data was analysed using linear and mixed-effect models. An increase in SD exerted a decrease in both PSS (B = -2.79, p ≤ 0.01) and blood lactate concentrations during submaximal running (B = -0.623, p ≤ 0.05). In addition, there was a negative relationship between SL and CMJ (B = -0.09, p = 0.08). Compared to males, females exhibited higher PSS scores and little or no change in performance-related tests. A significant interaction between time and sex was present in CMJ with males displaying an effect of time on CMJ performance. For all athletes, lower PSS appeared to be associated with longer overnight sleep. Since the females experienced higher levels of stress, monitoring of their PSS might be beneficial. These findings have implications for the preparation of young athletes’ competition season.

Feasibility Study of Exergaming Combined with High-Intensity Interval Training for Different Ages: Investigation of Aerobic Capacity and Mood State

&lt;p&gt;目的：探討體感式電玩結合高強度間歇運動對不同年齡層之血乳酸、心跳率、運動負荷量與運動情緒之效果。方法：本研究以有規律運動習慣之8位成年人與8位高齡者為研究對象，採橫斷面研究設計，並執行以任天堂switch健身環大冒險遊戲所設計之運動，進行8組20秒，強度為盡最大努力，每組間隔休息30秒，總時間為380秒。於運動前、運動中與運動後5分鐘、10分鐘檢測血乳酸、心跳率、運動自覺量表與運動情緒，計算運動負荷量，並以二因子混合設計分析收集數據，並計算效果量。結果：1. 血乳酸：兩組的血乳酸皆超過4 mmol/L，顯示運動強度達高強度，且成年人在運動中第4、8趟與運動後5、10分鐘皆顯著高於高齡者；2. 心跳率：運動期間，兩組的心跳率皆超過85%最大心跳率推估值，而成年人顯著高於高齡者；3. 運動負荷量：兩組間客觀與主觀的運動負荷量皆無顯著差異；4. 運動情緒：兩組在運動情緒之活力與疲勞分數上皆無顯著差異。結論：成年人和高齡者皆可利用體感式電玩搭配高強度間歇運動達到預期的高強度運動負荷，故可作為運動課程編排參考，以達到運動多元化。&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;&lt;p&gt;Purpose: This study aimed to investigate the effects of combining exergaming with high-intensity interval exercise (HIIE) on blood lactate levels, heart rate, exercise load, and mood state in different age groups. Methods: A cross-sectional study design was employed, and 8 young adults and 8 older adults, all with regular exercise habits, were recruited. The participants executed a HIIE program using the Nintendo Switch fitness ring adventure, comprising 8 sets of 20-second maximum-effort intervals followed by 30 second of rest, totaling 380 seconds of exercise. Blood lactate levels, heart rate, rating of perceived exertion (RPE) scale, and profile of mood states (POMS) were assessed before, during, and 5 and 10 minutes after the exercise. Exercise load was calculated based on the collected data. The data were analyzed using a two-way mixed-design analysis of variance. Results: 1. Blood lactate levels: The concentration of blood lactate in both groups showed an increase over 4 mmol/L during HIIE program, indicating the high exercise intensity. The young adult group exhibited significantly higher blood lactate levels than the older adult group at the 4th, 8th exercise bouts, and 5 and 10 minutes after exercise. 2. Heart rate: During the exercise, heart rates of both groups exceeded 85% of the estimated maximum heart rate (HRmax), with significantly higher rates observed in the young adult group compared to the older adult group. 3. Exercise load: There were no significant differences in objective (%HRmax) and subjective (RPE scores) exercise load between the groups. 4. Mood state: Both groups showed no significant differences in vigor and fatigue scores on the POMS. Conclusion: To diversify exercise options, combining exergaming with HIIE when designing an exercise program could be an option in both young and older individuals.&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

Effect of theFran CrossFit Workout on Oxygen Uptake Kinetics, Energetics, and Postexercise Muscle Function in Trained CrossFitters.

Fran is one of the most popular CrossFit benchmark workouts used to control CrossFitters' improvements. Detailed physiological characterization of Fran is needed for a more specific evaluation of CrossFitters' training performance improvements. The aim of the study was to analyze the oxygen uptake (V˙O2) kinetics and characterize the energy system contributions and the degree of postexercise fatigue of the unbroken Fran. Twenty trained CrossFitters performed Fran at maximal exertion. V˙O2 and heart-rate kinetics were assessed at baselineand during and post-Fran. Blood lactate and glucose concentrations and muscular fatigue were measured at baseline and in the recovery period. A marked increase in V˙O2 kinetics was observed at the beginning of Fran, remaining elevated until the end (V˙O2peak: 49.2 [3.7]mL·kg-1·min-1, V˙O2 amplitude: 35.8 [5.2]mL·kg-1·min-1, time delay: 4.7 [2.5]s and time constant: 23.7 [11.1]s; mean [SD]). Aerobic, anaerobic lactic, and alactic pathways accounted for 62% (4%), 26% (4%), and 12% (2%) of energy contribution. Reduction in muscle function in jumping ability (jump height: 8% [6%], peak force: 6% [4%], and maximum velocity: 4% [2%]) and plank prone test (46% [20%]) was observed in the recovery period. TheFran unbroken workout is a high-intensity effort associated with an elevated metabolic response. This pattern of energy response highlights the primary contribution of aerobic energy metabolism, even during short and very intense CrossFit workouts, and that recovery can take >24hours due to cumulative fatigue.

Acute Hemodynamic, Metabolic, and Hormonal Responses to a Boxing Exergame with and without Blood Flow Restriction in Non-Athlete Young Individuals.

This study aimed to compare acute hemodynamic, metabolic (glucose and blood lactate concentrations), hormonal (growth hormone and normetanephrine), heart rate variability (HRV), and rating of perceived exertion (RPE) responses before and after bouts of a boxing exergame with and without blood flow restriction (BFR) in non-athlete young individuals. Fourteen participants (age: 30 ± 10 y; BMI: 21 ± 3 kg.m-2) participated in two sessions of a 20 min boxing exergame. During week one, the participants were randomly divided into two groups and played against one another under normal (n = 7) and BFR (n = 7) conditions. Over the next exercise session, participants were then reallocated to the opposite condition (normal vs. BFR) for data collection. Hemodynamic, metabolic, HRV, and hormonal parameters were measured before and immediately after the exercise protocols. Playing exergame led to a significant increase in hemodynamic variables (except for diastolic blood pressure) regardless of BFR condition with no between-group differences. Regarding HRV, significant reductions in total power (TP) and low-frequency (LF) waves were identified in the non-BFR group (p < 0.0001) compared with the BFR group. Conversely, a significant increase in very LF (VLF) waves was noted for the BFR group (p = 0.050), compared with the non-BFR group. Significant increases were observed in serum concentrations of growth hormone, normetanephrine, and blood lactate concentration from pre- to post-exercise under both conditions (p ≤ 0.05), with no significant differences between the groups. Moreover, no statistically significant changes were observed in glucose levels. RPE responses were significantly greater (p ≤ 0.05) in the BFR group compared with the non-BFR group throughout the exercise session. We observed similar hemodynamic, hormonal, and metabolic responses after an acute boxing exergame session in young individuals, whether conducted with or without BFR. However, notable differences were observed in certain HRV markers and RPE. Specifically, the inclusion of BFR resulted in an elevation of VLF and a heightened perceived exertion. These findings suggest that BFR may alter cardiac autonomic and perceptual responses during exergaming. Further research is warranted to understand the long-term implications and potential benefits of incorporating BFR into exergaming routines.

Measuring the Level of Agreement for Lactate Measurements in Hispaniolan Amazon Parrots (Amazona ventralis) Among 2 Point-of-Care Analyzers and a Benchtop Analyzer.

Lactate is an important biochemistry analyte used in human and veterinary medicine to assess tissue perfusion and can be used as a prognostic indicator for certain disease conditions. Whereas lactate is commonly measured using "patient-side" handheld meters, these meters have not been validated for companion avian species. The purpose of this study was to measure the level of agreement between 2 commercially available point-of-care lactate meters and a laboratory benchtop blood analyzer in Hispaniolan Amazon parrots (Amazona ventralis). Blood samples were collected from 20 adult parrots at Louisiana State University by drawing 1.5 mL of blood from the right jugular vein. One drop of whole blood was used for the Lactate Plus analyzer and the remainder of the sample transferred into a lithium heparin microtainer. From the blood in the microtainer, 0.2 mL whole blood was analyzed using the epoc Blood Analysis System, and the remaining sample was centrifuged to obtain plasma that was immediately frozen at -80°C (-112°F) and submitted to the Texas A&M University Clinical Pathology Laboratory for analysis on the VITROS 4500 benchtop analyzer. Bland-Altman agreement plots and Passing-Bablok regression were used to measure the level of agreement between the methods. There was poor agreement between all 3 methods with mean percentage differences in lactate concentrations ≥22% (epoc and Lactate Plus: 33.6% [95% CI: 27-40]; epoc and VITROS 4500: 55% [95% CI:52-58]; VITROS 4500 and Lactate Plus: 22% [95% CI:16-28]). Based on these results, the point-of-care meters tested in this study are not interchangeable, and separate reference intervals were calculated for each method. Blood lactate concentrations may have more utility in tracing lactate trends over time in an individual rather than being able to utilize this information at 1 time point for disease diagnosis and prognosis.

Heart Rate Variability Thresholds: Agreement with Established Approaches and Reproducibility in Trained Females and Males.

To determine in trained females and males i) the agreement between the gas exchange threshold (GET), lactate threshold 1 (LT1), and heart rate variability threshold 1 (HRVT1), as well as between the respiratory compensation point (RCP), lactate threshold 2 (LT2), and heart rate variability threshold 2 (HRVT2), and ii) the reproducibility of HRVT1 and HRVT2 during 2-min incremental step protocols. Fifty-seven trained participants (24 females) completed a 2-min step incremental test to task failure. Nineteen participants (eight females) completed a second test to evaluate reproducibility. Gas exchange and ventilatory responses, blood lactate concentration, and RR time series were recorded to assess the oxygen consumption (V̇O 2 ) and heart rate (HR) associated with the GET, RCP, LT1, LT2, HRVT1, and HRVT2. V̇O 2 -GET versus V̇O 2 -HRVT1 and HR-GET versus HR-HRVT1 were statistically different for females (29.5 ± 4.0 vs 34.6 ± 6.1 mL·kg -1 ·min -1 ; 154 ± 11 vs 166 ± 12 bpm) and for males (33.9 ± 4.2 vs 42.7 ± 4.6 mL·kg -1 ·min -1 ; 145 ± 11 vs 165 ± 9 bpm; P < 0.001). V̇O 2 and HR at HRVT1 were greater than at LT1 ( P < 0.05). V̇O 2 -RCP versus V̇O 2 -HRVT2 and HR-RCP versus HR-HRVT2 were not statistically different for females (40.1 ± 4.7 vs 39.5 ± 6.7 mL·kg -1 ·min -1 ; 177 ± 9 vs 176 ± 9 bpm) and males (48.4 ± 5.4 vs 47.8 ± 4.8 mL·kg -1 ·min -1 ; 176 ± 8 vs 175 ± 9 bpm; P > 0.05). V̇O 2 and HR responses at LT2 were similar to HRVT2 ( P > 0.05). Intraclass correlation coefficient for V̇O 2 -HRVT1, HR-HRVT1, V̇O 2 -HRVT2, and HR-HRVT2 indicated good reproducibility when comparing the two different time points to standard methods. Whereas HRVT2 is a valid and reproducible estimate of the RCP/LT2, current approaches for HRVT1 estimation did not show good agreement with outcomes at GET and LT1.

Effect of hypoxic sprint interval exercise and normoxic recovery on performance and acute physiological responses

AbstractHypoxic exercise, which can induce arterial and tissue deoxygenation, promotes physiological adaptations. However, reduced oxygen availability can lower the absolute training intensity (i.e., mechanical stress). Adding normoxic recovery to sprint interval exercise (SIE) is one potential approach to strike a balance between providing a hypoxic stimulus and maintaining the absolute training intensity. However, the effects of adding normoxic recovery to SIE on performance and physiological responses are uncertain. We tested the hypothesis that hypoxic SIE with normoxic recovery enhances arterial deoxygenation and muscle deoxygenation levels without impeding performance compared to an entirely normoxic condition. On separate days, seven male sprinters performed 4 × 30‐s ‘all‐out’ cycle sprints with 4.5‐min recovery with hypoxic exposure (FiO2: 12.7%O2) applied continuously (hypoxia, HYP), intermittently during sprint periods only (intermittent, INT), or not at all (normoxia, NOR). Power output, oxygen saturation, muscle oxygenation, surface electromyography (EMG) activity, heart rate, blood lactate concentration, and ratings of perceived exertion were measured. The total work significantly decreased in HYP than NOR (p &lt; 0.05) and INT (p &lt; 0.01). The aTrterial oxygen saturation was lower during HYP than NOR (∼86% vs. ∼97%; p &lt; 0.001), while lower values were also obtained for INT than NOR during sprint periods (∼85% vs. ∼97%; p &lt; 0.001) but not during recovery periods (∼96% vs. ∼97%). The heart rate differed (p &lt; 0.05) between conditions (NOR: ∼164 bpm; INT: ∼160 bpm; HYP: ∼156 bpm). No other variables demonstrated significant differences between conditions. Adding hypoxia during exercise while recovering in normoxia did not compromise exercise capacity during SIE, despite inducing larger arterial deoxygenation levels compared to normoxia.

Correlation of detrended fluctuation analysis alpha 1 with blood lactate concentration in field standardised exercise tests in sport horses

Abstract Methods to determine exercise intensity thresholds, such as the aerobic and anaerobic threshold, that separate different exercise intensities in exercising horses in the field setting or on the treadmill often require equipment, standardised conditions and/or blood sampling. Detrended fluctuation analysis (DFA) is a heart rate variability variable proposed as a non-invasive tool for exercise intensity monitoring and with a potential association with exercise intensity thresholds and fatigue. The objectives of this study were to (1) describe the first component of DFA (DFA-α1) during standardised field incremental exercise tests in sport horses in active Eventing competition and in sport horses ridden without the goal of participating in competitions, and (2) to determine if DFA-α1 is associated with blood lactate concentration. Null hypotheses of the study were that (1) DFA-α1 is not correlated with blood lactate concentration measurements and (2) the correlation between DFA-α1 and blood lactate concentration is not stronger than the one between blood lactate concentration and heart rate or blood lactate concentration and speed. An in vivo observational study was performed analysing exercising electrocardiograms obtained in 59 standardised exercise tests in the field. DFA-α1 was significantly and moderately correlated with blood lactate concentration (, ). A strong correlation was observed between blood lactate concentration and speed (, ), as well as between blood lactate concentration and heart rate (, ). DFA-α1 correlation with blood lactate concentration was moderate but weaker than the correlation of blood lactate concentration and heart rate or blood lactate concentration and speed. DFA-α1 was not a useful surrogate of blood lactate concentration in field incremental standardised tests used for sport horses in this setting.

Ventricular arrhythmia burden during different physical activities in patients with arrhythmogenic right ventricular cardiomyopathy: Preliminary analysis

Introduction&#x0D; Patients suffering from arrhythmogenic right ventricular cardiomyopathy (ARVC) should avoid intense endurance exercise to reduce the risk of adverse cardiac events and disease progression. On the other hand, an active lifestyle might be preferable to a sedentary one, which also brings a host of complications. Evidence for safe levels of physical activity in ARVC, however, is scarce. This is study aimed to describe the ventricular arrhythmia burden - estimated as the prevalence of premature ventricular contractions (PVC) - of different exercise modalities and intensities on ARVC patients.&#x0D; Methods&#x0D; The pilot analysis includes four (1F, 33 ± 12 yrs, BMI 24 ± 4 kg/m2) ARVC patients harboring a pathogenic plakophilin-2 variant and carrying an implantable cardioverter-defibrillator performed different exercises while monitored via 12-lead ECG. The order of modalities was randomized and participants instructed to stop when surpassing perceived exertion of 15 on the Borg 6-20 scale. Resistance exercises included two-legged squats and single arm biceps curls (each with 20 repetitions and 2 min duration) while endurance exercise included 5 min of treadmill walking, 3 min cycling bouts at heart rate (HR) of 80, 100 and 120 bpm as well as cycling at 120 bpm with 2 additional min of active cool down. Blood lactate concentration was assessed at the end of the cycling bouts.&#x0D; Results&#x0D; No adverse cardiac event were noted and no exercise was terminated for medical reasons. During walking HR was 76 ± 8 bpm, whereas PVC burden was 11 ± 6% (range 4-18%). Cycling at 82 ± 4 bpm induced a PVC burden of 7 ± 5% (range 3- 14%), which increased to 13 ± 8% (range 3- 21%) at 93 ± 2 bpm and further to 16 ± 16% (range 7-37%) at 105 ± 3 bpm. In all three modalities the PVC burden was higher in the first 3 min of recovery than during the activity itself. Adding a 2 min active cool down increased the PVC burden to 25 ± 16% (range 6-45%). 2-legged squats performed at 101 ± 15 bpm had a PVC burden of 9 ± 12%, which increased to 19 ± 14% at recovery. One arm biceps curls at 75 ± 13 bpm had a PVC burden of 4 ± 3% during the activity and 9 ± 5% during recovery. Perception of effort varied widely when cycling at 80 bpm (range 6-12) or 100 bpm (range 8-14), but less so at 120 bpm (range 13-15). Blood lactate concentration when cycling at 120 bpm ranged between 2.2 and 3.5 mmol/L, typically associated with exercise in the “heavy” intensity domain.&#x0D; Discussion/Conclusion&#x0D; ARVC patients present a high, intensity-dependent PVC burden during exercise and short-term recovery. However, we observed widely different PVC burdens and perceived exertion at a given HR during different exercise modalities, which calls for personalized recommendations on physical activity. Exercises with small muscle mass seem to minimize the PVC burden and training the different muscles separately could be an interesting avenue to maintain physical fitness in ARVC patients.

The origin of the maximal lactate steady state (MLSS).

The maximal lactate steady state, abbreviated as MLSS, is the maximal exercise intensity where the concentration of earlobe capillary or arterial blood lactate remains constant over time. In the late 1970s and early 1980s, we (i.e. Hermann Heck and co-workers) developed a direct test to determine the MLSS to investigate whether it occurred at a lactate concentration of 4 mmol.L- 1, as earlier predicted by Alois Mader and colleagues. The test consisted of each participant performing several constant-intensity running bouts of ≈ 30min at intensities close to the estimated MLSS. During each run, we measured lactate every 5min. Based on the results, we defined the MLSS as the "workload where the concentration of blood lactate does not increase more than 1 mmo.L- 1during the last 20 min of a constant load exercise". This MLSS protocol is impractical for performance testing as it requires too many exercise bouts, but it is a gold standard to determine the real MLSS. It is especially useful to validate indirect tests that seek to estimate the MLSS.

Performance-Determining Variables of a Simulated Sprint Cross-Country Skiing Competition.

To investigate performance-determining variables of an on-snow sprint cross-country skiing competition and the evolvement in their relationship with performance as the competition progresses from the individual time trial (TT) to the final. Sixteen national-level male junior skiers (mean [SD] age, 18.6 [0.8]y; peak oxygen uptake [VO2peak], 67.6 [5.5]mL·min-1·kg-1) performed a simulated sprint competition (1.3km) in the skating style, comprising a TT followed by 3 finals (quarterfinals, semifinals, and final) completed by all skiers. In addition, submaximal and incremental roller-ski treadmill tests, on-snow maximal speed tests, and strength/power tests were performed. VO2peak and peak treadmill speed during incremental testing and relative heart rate, rating of perceived exertion, blood lactate concentrations, and gross efficiency during submaximal testing were all significantly correlated with performance in the TT and subsequent finals (mean [range] r values: .67 [.53-.86], all P < .05). Relative VO2peak and submaximal relative heart rate and blood lactate concentration were more strongly correlated with performance in the semifinals and final compared with the TT (r values: .74 [.60-.83] vs 0.55 [.51-.60], all P < .05). Maximal speed in uphill and flat terrain was significantly correlated with performance in the TT and subsequent finals (r values: .63 [.38-.70], all P < .05), while strength/power tests did not correlate significantly with sprint performance. VO2peak and high-speed abilities were the most important determinants of sprint cross-country skiing performance, with an increased importance of VO2peak as the competition format progressed toward the final.

Shifting the Energy Toward Los Angeles: Comparing the Energetic Contribution and Pacing Approach Between 2000- and 1500-m Maximal Ergometer Rowing.

To compare the energetic contribution and pacing in 2000- and 1500-m maximal rowing-ergometer performances. On separate visits (>48 h apart, random order), 18 trained junior (16.7 [0.4]y) male rowers completed 3 trials: a7 × 4-minute graded exercise test, a2000-m time trial (TT2000), and a1500-m TT (TT1500). Respiratory gases were continuously measured throughout each trial. The submaximal power-to-oxygen-consumption relationship from the graded exercise test was used to determine the accumulated oxygen deficit for each TT. Differences in mean power output (MPO), relative anaerobic contribution, percentage of peak oxygen uptake, pacing index, maximum heart rate, rating of perceived exertion, and blood lactate concentration were assessed using linear mixed modeling. Compared to TT2000 (324 [24]W), MPO was 5.2% (3.3%) higher in TT1500 (341 [29W]; P < .001, ηp2=.70). There was a 4.9% (3.3%) increase (P < .001, ηp2=.71) in anaerobic contribution from 17.3% (3.3%) (TT2000) to 22.2% (4.3%) (TT1500). Compared to TT1500, maximum heart rate, rating of perceived exertion, and blood lactate concentration were all greater (P < .05) in TT2000. The pacing index was not different between trials. Percentage increase in MPO from TT2000 to TT1500 was negatively associated with pacing variance in TT1500 (R2 = .269, P = .027). Maximal ergometer performance over 1500m requires a significantly greater anaerobic contribution compared with 2000m. Junior male athletes adopt a consistent pacing strategy across both distances. However, those who experienced greater percentage increases in MPO over the shorter test adopted a more even pacing strategy. To prepare for 1500-m performance, greater emphasis should be placed on developing capacity for work in thesevere domain and completing race simulations with a more even pacing strategy.

Myocardial proteome changes in aortic stenosis rats subjected to long-term aerobic exercise.

The effects of exercise training (ET) on the heart of aortic stenosis (AS) rats are controversial and the mechanisms involved in alterations induced by ET have been poorly clarified. In this study, we analyzed the myocardial proteome to identify proteins modulated by moderate-intensity aerobic ET in rats with chronic supravalvular AS. Wistar rats were divided into four groups: sedentary control (C-Sed), exercised control (C-Ex), sedentary aortic stenosis (AS-Sed), and exercised AS (AS-Ex). ET consisted of five treadmill running sessions per week for 16 weeks. Statistical analysis was performed by ANOVA or Kruskal-Wallis and Goodman tests. Results were discussed at a significance level of 5%. At the end of the experiment, AS-Ex rats had higher functional capacity, lower blood lactate concentration, and better cardiac structural and left ventricular (LV) functional parameters than the AS-Sed. Myocardial proteome analysis showed that AS-Sed had higher relative protein abundance related to the glycolytic pathway, oxidative stress, and inflammation, and lower relative protein abundance related to beta-oxidation than C-Sed. AS-Ex had higher abundance of one protein related to mitochondrial biogenesis and lower relative protein abundance associated with oxidative stress and inflammation than AS-Sed. Proteomic data were validated for proteins related to lipid and glycolytic metabolism. Chronic pressure overload changes the abundance of myocardial proteins that are mainly involved in lipid and glycolytic energy metabolism in rats. Moderate-intensity aerobic training attenuates changes in proteins related to oxidative stress and inflammation and increases the COX4I1 protein, related to mitochondrial biogenesis. Protein changes are combined with improved functional capacity, cardiac remodeling, and LV function in AS rats.

The impact of general and/or specific warm-up on power and velocity during squat and bench-press training

The study aimed to compare the effects of two warm-up strategies on mechanical force production during bench press and squat resistance training sessions. Twenty-six trained male subjects (24.37±5.83years, 75.48±12.12kg, 1.74±0.07m) performed a squat or bench press resistance training session after a specific warm-up (SWU) or general warm-up followed by a specific warm-up (GSWU). The SWU included 2x6 repetitions at 32% and 64% of the maximal load (1RM), respectively. The GSWU included 10 minutes of treadmill running (70% of heart rate reserve) followed by SWU. The resistance training session consisted of 3x6 with a load of 80% 1RM. Mechanical (mean propulsive velocity, mean propulsive power and velocity loss), physiological [heart rate (HR), blood lactate concentration], and psychophysiological variables (rating of perceived exertion) were evaluated. In the bench press and squat resistance training sessions, no differences were found in the mechanical and psychophysiological variables. When performing the bench press, the GSWU caused an increased HR response after warm-up (100.00±16.93bpm vs. 110.57±9.69bpm, p=0.03; ES=0.65, moderate effect). GSWU or SWU can both be used as preparatory activities for bench press and squat resistance training performance without related restrictions. These findings may be helpful for professionals to provide appropriate warm-up strategies to maximize resistance training. Keywords: Pre-exercise, Strength, T-Force, Velocity, Physiology, Resistance Training

Response of skin temperature, blood ammonia and lactate during incremental exercise until exhaustion in elite athletes

The study aimed to evaluate the lower limb skin temperature (Tsk) and blood concentrations of lactate (LA) and ammonia (NH3) during exercise and recovery. Eleven elite sprint athletes (25 ± 3.4 yrs) and 11 elite endurance athletes (24.45 ± 5.4 yrs) performed an incremental running test until exhaustion. Body composition was estimated using the DXA method. Thermograms of the anterior and posterior surfaces of the lower limbs were recorded at rest, before each test stage (every 3 min, starting from 10 km h−1 and increasing by 2 km h−1), and in the 5th, 10th, 15th, 20th, and 30th minute of recovery. Endurance athletes had a higher maximum oxygen uptake than sprint athletes (5.0 ± 0.7 vs 4.3 ± 0.4 l·kg−1, p = 0.018), lower percentage of lean content (79 ± 2 vs 83 ± 2%, p < 0.001), and a higher percentage of fat content in the lower limbs (17 ± 2 vs 12 ± 2%, p < 0.001). In both groups, a significant decrease in Tsk was observed compared to resting value (endurance athletes—31.5 ± 0.6 °C; sprint athletes—32.3 ± 0.6 °C), during exercise (p < 0.001) and rewarming during recovery (p < 0.001). However, endurance athletes had a lower Tsk than sprint athletes at the exhaustion point (30.0 ± 1.1 vs 31.6 ± 0.8 °C, p < 0.05) and the pattern of change in Tsk differed between groups (p < 0.001). Tsk in the endurance athletes group decreased throughout the exercise protocol and returned more rapidly to initial values during recovery, while Tsk in the sprint group stabilised between moderate intensity and exhaustion, recovering more slowly after exercise. Both LA (endurance athletes—max 10.2 ± 1.5; sprint athletes—max 10.1 ± 1.4 mmol⋅L−1, p < 0.001) and NH3 (endurance athletes—max 75.6 ± 11.5; sprint athletes—max 76.7 ± 9.0 mmol⋅L−1, p < 0.001) increased during exercise and decreased during recovery (p < 0.001). During exercise, lower levels and slower increases in LA were observed during exercise in the endurance athletes’ group (p < 0.05). A negative correlation was revealed between Tsk and fat percentage (r = −0.43 to −0.71, p < 0.05). Tsk was positively correlated with LA during recovery (r = 0.43 to 0.48, p < 0.05), and negatively during recovery (r = −0.45 to −0.54, p < 0.05). Differences between groups in maximum aerobic capacity, the pattern of change in Tsk, and the correlation between Tsk and LA suggest that individuals who decrease less Tsk during exercise and higher Tsk during recovery are those with better aerobic capacity. In addition, athletes with less body fat dissipate heat from their tissues more efficiently.