Blood Lactate Concentration Research Articles

The effect of Megasphaera elsdenii on faecal pH and blood pH, TCO2 and blood lactate concentration in horses transitioned to a high concentrate low roughage diet

The effect of <i>Megasphaera elsdenii</i> on faecal <scp>pH</scp> and blood <scp>pH</scp>, <scp>TCO2</scp> and blood lactate concentration in horses transitioned to a high concentrate low roughage diet

Relationship of peak capillary blood lactate accumulation and body composition in determining the mechanical energy equivalent of lactate during sprint cycling

AimA 15-s all-out sprint cycle test (i.e., νLamax-test) and the post-exercise change in capillary blood lactate concentration is an emerging diagnostic tool that is used to quantify the maximal glycolytic rate. The goal of this study was to determine the relation between 15 s-work, change in capillary blood lactate concentration (∆La) and body composition in a νLamax-test.MethodFifty cyclists performed a 15 s all-out sprint test on a Cyclus2 ergometer twice after a previous familiarization trial. Capillary blood was sampled before and every minute (for 8 min) after the sprint to determine ∆La. Body composition was determined employing InBody720 eight-electrode impedance analysis.ResultSimple regression models of fat-free mass (FFM) and also the product of FFM and ∆La showed similar ability to predict 15 s-work (R2 = 0.79; 0.82). Multiple regression combining both predictors explains 93% of variance between individuals. No differences between males and females were found regarding 15 s-work relative to the product of fat-free mass and ∆La. Considering pairs of similar FFM, a change 1 mmol/l of ∆La is estimated to be equal to 12 J/kg in 15 s-work (R2 = 0.85).DiscussionFifteen s-work is both closely related to FFM and also the product of ∆La and lactate-distribution space approximated by FFM. Differences in 15 s-work between males and females disappear when total lactate production is considered. Considering interindividual differences, the mechanical energy equivalent of blood lactate accumulation seems a robust parameter displaying a clear relationship between ∆La and 15 s-work relative to FFM.

HIIT at Home: Enhancing Cardiorespiratory Fitness in Older Adults-A Randomized Controlled Trial.

This study aimed to investigate the effectiveness of a 6-month home-based high-intensity interval training (HIIT) intervention to improve peak oxygen consumption (V̇O2peak) and lactate threshold (LT) in older adults. Two hundred thirty-three healthy older adults (60-84 years; 54% females) were randomly assigned to either 6-month, thrice-weekly home-based HIIT (once-weekly circuit training and twice-weekly interval training) or a passive control group. Exercise sessions were monitored using a Polar watch and a logbook for objective and subjective data, respectively, and guided by a personal coach. The outcomes were assessed using a modified Balke protocol combining V̇O2peak and LT measures. General linear regression models assessed between-group differences in change and within-group changes for each outcome. There was a significant between-group difference in the pre-to-post change in V̇O2peak (difference: 1.8 [1.2; 2.3] mL/kg/min; exercise: +1.4 [1.0; 1.7] mL/kg/min [~5%]; control: -0.4 [-0.8; -0.0] mL/kg/min [approximately -1.5%]; effect size [ES]: 0.35). Compared with controls, the exercise group had lower blood lactate concentration (-0.7 [-0.9; -0.4] mmol/L, ES: 0.61), % of peak heart rate (-4.4 [-5.7; -3.0], ES: 0.64), and % of V̇O2peak (-4.5 [-6.1; -2.9], ES: 0.60) at the intensity corresponding to preintervention LT and achieved a higher treadmill stage (% incline) at LT (0.6 [0.3; 0.8]; ES: 0.47), following the intervention. This study highlights the effectiveness of a home-based HIIT intervention as an accessible and equipment-minimal strategy to induce clinically meaningful improvements in cardiorespiratory fitness in older adults. Over 6 months, the exercise group showed larger improvements in all outcomes compared with the control group. Notably, the LT outcome exhibited a more pronounced magnitude of change than V̇O2peak.

The reliability and discriminant validity of physical, technical, and perceptual-physiological measures during a game-specific basketball activity simulation protocol.

Activity simulation protocols offer useful applications in research and practice; however, the specificity of such protocols to basketball game-play is currently lacking. Consequently, this study aimed to develop a game-specific basketball activity simulation protocol representative of typical playing durations and assess its reliability and discriminant validity. The simulation protocol was modified from an original version (i.e., Basketball Exercise Simulation Test) to incorporate regular breaks indicative of time-outs, free-throws, and substitutions. Twelve competitive male and female adult basketball players competing in the fourth or fifth Spanish basketball division underwent repeated trials of the simulation protocol (min. 4 to max. 14 days apart) for reliability analyses. In turn, 13 competitive male (fifth division), 9 competitive female (fourth division), and 13 recreational male adult basketball players completed the simulation protocol to assess discriminant validity via comparisons between sexes (competitive players) and playing levels (males). A range of physical, technical, and perceptual-physiological variables were collected during and following the simulation protocol. Several physical and heart rate variables displayed the strongest reliability (intraclass correlation coefficient [ICC] = 0.72-0.96; coefficient of variation [CV] = 1.78-6.75%), with physical decrement, technical, blood lactate concentration, and rating of perceived exertion (RPE) variables having the weakest (ICC = 0.52-0.75; CV = 10.34-30.85%). Regarding discriminant analyses between sexes, males demonstrated significantly greater physical outputs in several variables and lower RPE compared to females (p < 0.05, moderate-to-large effects). Comparisons between playing levels revealed competitive males had significantly greater physical outputs across many variables, alongside higher mean heart rate and lower RPE than recreational males (p < 0.05, moderate-to-large effects). This study presents a novel game-specific basketball activity simulation protocol replicating actual playing durations and game configurations that might be successfully applied for both training and research purposes. Reliability statistics are provided for several variables to inform end-users on potential measurement error when implementing the simulation protocol. Discriminant validity of the simulation protocol was supported for several variables, suggesting it may hold practical utility in benchmarking or selecting players. Future research on this topic is encouraged examining wider samples of male and female basketball players at different levels as well as additional forms of validity for the protocol.

Acute Responses to Different Velocity Loss Thresholds during Squat Exercise with Blood-Flow Restriction in Strength-Trained Men.

(1) Background: The aim of this paper is to analyze the acute effects of different velocity loss (VL) thresholds during a full squat (SQ) with blood-flow restriction (BFR) on strength performance, neuromuscular activity, metabolic response, and muscle contractile properties. (2) Methods: Twenty strength-trained men performed four protocols that differed in the VL achieved within the set (BFR0: 0% VL; BFR10: 10% VL; BFR20: 20% VL; and BFR40: 40% VL). The relative intensity (60% 1RM), recovery between sets (2 min), number of sets (3), and level of BFR (50% of arterial occlusion pressure) were matched between protocols. Tensiomyography (TMG), blood lactate, countermovement jump (CMJ), maximal voluntary isometric SQ contraction (MVIC), and performance with the absolute load required to achieve 1 m·s-1 at baseline measurements in SQ were assessed before and after the protocols. (3) Results: BFR40 resulted in higher EMG alterations during and after exercise than the other protocols (p < 0.05). BFR40 also induced greater impairments in TMG-derived variables and BFR10 decreased contraction time. Higher blood lactate concentrations were found as the VL within the set increased. BFR0 and BFR10 showed significantly increased median frequencies in post-exercise MVIC. (4) Conclusions: High VL thresholds (BFR40) accentuated metabolic and neuromuscular stress, and produced increased alterations in muscles' mechanical properties. Low VL could potentiate post-exercise neuromuscular activity and muscle contractile properties.

4-week stretching program after submaximal strength exercise affects performance but not heart rate variability and lactate clearance. An exploratory study.

Previous research has demonstrated that stretching can enhance athletic performance and induce cardiovascular adaptations. This study aims to assess whether a 4-week preventative stretching routine can enhance heart rate variability and heart rate recovery, faster blood lactate clearance, and improve performance following submaximal strength exercises. Twenty-four healthy adults were recruited and randomly allocated to either the experimental group or the control group. Both groups engaged in submaximal strength exercises (5 sets to voluntary failure at 60% of 1RM) comprising bench press and back squat exercises under baseline conditions and after stretching protocol. The experimental group followed the Stretching Protocol, while the control group adhered to their regular training routine. ANOVA analysis revealed a significant pre-post interaction effect between groups in the variable of squat repetitions, although no notable pre- or post-differences were observed in heart rate variability, heart rate recovery, blood lactate concentration, or bench repetitions in either group. A 4-week preventative stretching program does not appear adequate to enhance lactate clearance and cardiovascular adaptation after submaximal strength exercises in resistance-trained individuals compared to the control group. However, it is plausible that such a stretching routine may mitigate muscle fatigue, though further investigation is warranted to substantiate this hypothesis.

A Comparative Analysis of Acute Physiological and Perceptual Responses in Whole-Body and Ergometer-Based High-Intensity Interval Training Protocols.

The primary aim of the present investigation was to compare the acute physiological and perceptual responses between two modes of interval training using a randomized crossover design. More specifically, eleven young adult participants (23 ± 4 years, 77 ± 13 kg, 178 ± 7 cm) performed two protocols: one composed of whole-body calisthenics exercises and another on a cycle ergometer. Both protocols encompassed eight 20 s bouts at intensities equivalent to all-out (HIIT-WB) and 170% of the maximal power output (HIIT-C), respectively, interspersed with 10 s of passive rest. The peak and average heart rate, the rating of perceived effort, and blood lactate, creatine kinase, and lactate dehydrogenase concentrations were measured. Aside from blood lactate (HIIT-WB = 9.4 ± 1.8 mmo/L; HIIT-C = 12.5 ± 2.5 mmol/L, p < 0.05) and the rating of perceived exertion (HIIT-WB = 8.8 ± 0.9; HIIT-C = 9.6 ± 0.5, p < 0.05), physiological responses did not significantly differ between protocols (all p > 0.05), with high average heart rate values (HIIT-WB = 86 ± 6% HRmax; HIIT-C = 87 ± 4% HRmax) and a low magnitude of muscle damage, as inferred by CK and LDH concentrations (HIIT-WB = 205.9 ± 56.3 and 203.5 ± 72.4 U/L; HIIT-C = 234.5 ± 77.1 and 155.1 ± 65.3 U/L), respectively. It can be concluded that both protocols elicit vigorous heart rate responses and a low magnitude of muscle damage and, therefore, appear as viable alternatives to improve aerobic fitness. The inclusion of a whole-body HIIT protocol may be an interesting alternative for training prescription in relation to more common interval training protocols.

The prospective multicenter observational study of acute mesenteric ischemia (AMeSI): the results of the Arkhangelsk center

The objective was to assess the disease rate, prevalence of risk factors, diagnostic and management methods as well as outcomes in patients with acute mesenteric ischemia (AMI).Materials and methods. During 10 months in 2022-2023, the study included all patients with probable or confirmed diagnosis of AMI, in whom we recorded the presence of known risk factors, clinical and laboratory manifestations of AMI, methods of its diagnosis, management and outcomes within one year.Results. Totally, 705 patients from 32 centers were included in the work, among whom 418 patients were diagnosed with AMI. In Arkhangelsk, 39 patients (mean age – 73 years) were included into the study. According to results of the center in Arkhangelsk, the diagnosis of AMI was confirmed in 69% of patients, while the incidence among all hospitalized was 0.13%. None of the known risk factors (smoking, atrial fibrillation, atherosclerosis, arterial hypertension, previous myocardial infarction and thromboembolic complications) demonstrated a significant statistical association with the development of AMI. Among clinical manifestations, patients with confirmed AMI more likely developed signs of shock compared to patients with unconfirmed AMI (p = 0.028). Laboratory parameters did not differ significantly in both groups; however, in AMI non-survivors, we observed higher blood lactate concentrations. In most cases with confirmed AMI, the diagnosis was established during surgery. In 72% of cases, the situation was assessed as incurable; in 24% of patients, intestinal resection was performed. Mortality in patients with confirmed AMI was 78%.Conclusion. The lack of clear predictors of the disease, specific clinical signs of AMI and available laboratory tests often leads to delay in diagnosis and appropriate management, which causes significant mortality. Further analysis of the data is necessary to improve diagnosis and the results of treatment of the patients with AMI.

Rating of Perceived Exertion: A Large Cross-Sectional Study Defining Intensity Levels for Individual Physical Activity Recommendations

BackgroundPhysical inactivity is a growing risk factor worldwide, therefore getting people into sports is necessary. When prescribing physical activity, it is essential to recommend the correct training intensities. Cardiopulmonary exercise testing (CPX) enables precise determination of individuals’ training intensities but is unavailable for a broad population. Therefore, the Borg scale allows individuals to assess perceived exertion and set their intensity easily and cost-efficiently. In order to transfer CPX to rating of perceived exertion (RPE), previous studies investigated RPE on specific physiological anchors, e.g. blood lactate (bLa) concentrations, but representativeness for a broad population is questionable. Some contradictory findings regarding individual factors influencing RPE occur, whereas univariable analysis has been performed so far. Moreover, a multivariable understanding of individual factors influencing RPE is missing. This study aims to determine RPE values at the individual anaerobic threshold (LT2) and defined bLa concentrations in a large cohort and to evaluate individual factors influencing RPE with multivariable analysis.MethodsCPX with bicycle or treadmill ergometer of 6311 participants were analyzed in this cross-sectional study. RPE values at bLa concentrations 2 mmol/l, 3 mmol/l, 4 mmol/l, and LT2 (first rise in bLa over baseline + 1.5 mmol/l) were estimated by spline interpolation. Multivariable cumulative ordinal regression models were performed to assess the influence of sex, age, type of ergometry, VO2max, and duration of exercise testing on RPE.ResultsMedian values [interquartile range (IQR)] of the total population were RPE 13 [11; 14] at 2 mmol/l, RPE 15 [13; 16] at 3 mmol/l, RPE 16 [15; 17] at 4 mmol/l, and RPE 15 [14; 16] at LT2. Main influence of individual factors on RPE were seen especially at 2 mmol/l: male sex (odds ratio (OR) [95%-CI]: 0.65 [0.587; 0.719]), treadmill ergometry (OR 0.754 [0.641; 0.886]), number of stages (OR 1.345 [1.300; 1.394]), age (OR 1.015 [1.012; 1.018]), and VO2max (OR 1.023 [1.015; 1.030]). Number of stages was the only identified influencing factor on RPE at all lactate concentrations/LT2 (3 mmol/l: OR 1.290 [1.244; 1.336]; 4 mmol/l: OR 1.229 [1.187; 1.274]; LT2: OR 1.155 [1.115; 1.197]).ConclusionOur results suggest RPE ≤ 11 for light intensity, RPE 12–14 for moderate intensity, and RPE 15–17 for vigorous intensity, which slightly differs from the current American College of Sports Medicine (ACSM) recommendations. Additionally, we propose an RPE of 15 delineating heavy and severe intensity domain. Age, sex, type of ergometry, duration of exercise, and cardiopulmonary fitness should be considered when recommending individualized intensities with RPE, primarily at lower intensities. Therefore, this study can be used as a new guideline for prescribing individual RPE values in the clinical practice, predominantly for endurance type exercise.

High vs. low glycaemic index pre-exercise feeding

Carbohydrates are proven to be the most important energy source to skeletal muscle during endurance exercise. However, the glucose that carbohydrates provide the muscle with can differ in how quickly they are digested and released into the bloodstream. High glycaemic index (GI) carbohydrates are released into the bloodstream in a rapid burst following digestion whereas low GI carbohydrates are released into the bloodstream at a constant rate after consumption. The effects of low and high GI carbohydrate consumption pre-exercise on endurance exercise performance are not comprehensively understood. Therefore, the aim of this study is to identify the impact of low vs high GI pre-exercise feeding on maximal effort endurance exercise performance. With institutional ethics approval, twelve physically active, healthy males aged 18-40 years attended the laboratory on four separate occasions. On the first occasion, participants underwent a V̇O2max test to identify their maximal aerobic capacity. The final three lab visits consisted of the participants undergoing trials under three differing conditions upon arrival in the fasted state (participants were instructed to not consume food or drink other than water 6 h before arrival). The trial entailed of 20 km cycling followed by 5 km running with 2 min rest in between. Upon arrival, the participants received a carbohydrate beverage, either 40 g high GI, 40 g low GI, or a placebo, 15 min before exercising. Before consumption of the beverage, before the onset of exercise, after each 5 km during the cycle and following the run, heart rate and RPE were recorded, and a finger prick blood sample was taken to analyse for blood glucose and blood lactate concentrations throughout the exercise bout. However, the primary performance indicator was the overall time to complete the trial (bike and run minus 2 min rest). The final order of mean completion time across conditions from fastest to slowest went low GI, high GI, placebo. There was no significant difference between the mean time to completion in the low GI and high GI conditions. However, the low GI condition resulted in a faster time to completion than the placebo condition (P = 0.02) as well as the high GI condition resulting in a faster time to completion than the placebo condition (P = 0.043). Therefore, this could demonstrate that the presence of any carbohydrate type is more influential on endurance exercise performance rather than the glycaemic index of such carbohydrates.

Physiological, perceptual and neuromuscular responses to 15 vs. 30 s work durations during short high intensity interval training

High intensity interval training (HIIT) is an extremely potent stimulus for physiological adaptation offering a low volume training approach that can be easily accommodated into an individual’s training schedule. A key feature that drives physiological adaptation is the time the individual spends at or around their individual V̇O2max during HIIT. This can be influenced by several variables, including the work bout duration (Buchheit &amp; Laursen, 2013, Sports Med, 43, 318-338). The use of short duration HIIT intervals (i.e., &lt; 60 s) are popular due to their ability to facilitate a high oxygen uptake while minimising fatigue (Buchheit &amp; Laursen, 2013, Sports Med, 43, 318-338). However, the physiological response to different short duration HIIT formats has not yet been investigated. The aim of this study was to measure the physiological, perceptual and neuromuscular responses to two traditional short duration (i.e., 15 and 30 s) HIIT formats in trained athletes. With ethics approval, 10 well-trained male and female team sport players (mean + SD; age: 22 ± 1 years; body mass: 78 ± 6 kg; stature: 176 ± 4 cm) were recruited to the study and visited the laboratory on three separate occasions. After an incremental test to exhaustion on a cycle ergometer to establish V̇O2max (52.3 ± 5.7 ml·kg-1·min-1) and peak power output at V̇O2max (pV̇O2max; 313 ± 21 W), two HIIT sessions (15 s effort: 15 s passive recovery and 30 s effort: 30 s passive recovery) were completed in a randomised order. HIIT interventions comprised 15 s or 30 s at 120% pV̇O2max followed by 15 or 30 s passive recovery, repeated for 2 × 6 min with 5 min active recovery at 40% pV̇O2max. V̇O2, time &gt;90% V̇O2max, heart rate, and RPE were measured during the HIIT session and blood lactate concentration recorded 5 minutes afterwards. Measures of knee extensor maximal voluntary contraction (MVC) were measured immediately before and after each HIIT session.

Effects of Post-Activation Performance Enhancement in Kayak Sprint Competition within Same Day

The purpose of this study was to determine the post-activation performance enhancement in kayak sprint competitive simulation 2 times (S1 and S2) within the same day. This study was a crossover design, ten kayak sprint paddles national team performed different activations. All participants will be randomized crossover trials, get three interventions consisting of the Resistance program (2 x 4 x 80%1RM x Bench press and Bench row), Maximum sprint paddle (Ergometer all-out 2 x 10-sec x rest interval 2 min) and Control group (CON; Individual activity condition) followed 3-minute test (3MT). Maximum power, power average, stroke per minute, total distance, percentage of heart rate, and blood lactate concentration were recorded during the simulation competition. The main effect of the analysis showed that maximum power of the Resistance program was higher than the Control group in S1. The average power and total distance of the Resistance program in S2 were lower than in S1. Blood lactate concentration of the Resistance program and Maximum sprint paddle was higher than the Control group after the intervention, before the 3MT period, and remained rise until after 3MT, especially in S2. Also, blood lactate concentration before the intervention of the Resistance program in S2 was higher than in S1. The preconditioning by using the resistance or maximum sprint paddle improves maximum power only the first competition of the day. It seems that the resistance program leads to accumulated blood lactate concentration, and may decrease performance in the second competition of the day.

Metabolic flexibility associated with flight time among combat pilots of the Brazilian air force.

Fighter pilots must support the effects of many stressors, including physical and psychological exertion, circadian disturbance, jet lag, and environmental stress. Despite the rigorous selection of military pilots, those factors predispose to failures in physiological compensatory mechanisms and metabolic flexibility. We compared through NMR-based metabolomics the metabolic profile of Brazilian F5 fighter pilots with different flight experiences vs. the control group of non-pilots. We hypothesized that combat pilots have metabolic flexibility associated with combat flight time. We evaluated for the first time 34 Brazilian fighter pilots from Santa Cruz Air Base (Rio de Janeiro, RJ) allocated into three groups: pilots with lower total accumulated flight experience < 1,100h (PC1, n = 7); pilots with higher total accumulated flight experience ≥ 1,100h (PC2, n = 6); military non-pilots (CONT, n = 21). Data collection included anthropometric measurements, total blood count, lipidogram, markers of oxidative stress, and serum NMR-based metabolomics. In comparison with controls (p < 0.05), pilots exhibited decreased levels of white blood cells (-13%), neutrophils (-15%), lymphocytes (-20%), alfa-glucose (-13%), lactate (-26%), glutamine (-11%), histidine (-20%), and tyrosine (-11%), but higher isobutyrate (+ 10%) concentrations. Significant correlations were found between lactate vs. amino acids in CONT (r = 0.55-0.68, p < 0.001), and vs. glutamine in PC2 (r = 0.94, p = 0.01). Fighter pilots with lower experience showed a dysregulation in immune-metabolic function in comparison with controls, which seemed to be counteracted by the accumulation of flight hours. Those findings might have implications for the health preservation and operational training of fighter pilots.

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

Abstract Background Patients suffering from arrhythmogenic right ventricular cardiomyopathy (ARVC) should avoid intense endurance exercise to reduce the risk of adverse cardiac events and disease progression. While an active lifestyle would be preferable to a sedentary one, evidence for safe levels of physical activity in ARVC, however, is scarce. Purpose This study aimed to describe the ventricular arrhythmia burden experienced during exercise and immediate recovery - estimated as the prevalence of premature ventricular contractions (PVC) - of different exercise modalities and intensities on ARVC patients. Methods This preliminary 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 that 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 (20 repetitions and 2 min duration). Endurance exercise included 5 min of treadmill walking and 3-min cycling bouts at heart rates (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 after each cycling bout. Results No adverse cardiac event or early termination for medical reasons occurred. Figure 1 summarizes the relationship between HR, perceived exertion and PVC burden. During walking (HR 76 ± 8 bpm), 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 increased further to 16 ± 16% (range 7 – 37%) at 105 ± 3 bpm. In all three intensities 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 (HR 101 ± 15 bpm) had a PVC burden of 9 ± 12%, which increased to 19 ± 14% at recovery. One arm biceps curls (HR 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. Conclusions PVC burden was high and seemingly intensity-dependent during exercise and immediate recovery. The wide range of PVC burden for physiological or subjective markers of effort call for personalized recommendations on physical activity. Exercises with small muscle mass such as biceps curls seem to minimize the PVC burden, thus, training the different muscles separately could be an interesting avenue to maintain physical fitness in ARVC patients.

Acute cardiovascular and muscular response to rowing ergometer exercise in artificial gravity – a pilot trial

Prolonged immobilization and spaceflight cause cardiovascular and musculoskeletal deconditioning. Combining artificial gravity through short-arm centrifugation with rowing exercise may serve as a countermeasure. We aimed to compare the tolerability, muscle force production, cardiovascular response, and power output of rowing on a short-arm centrifuge and under terrestrial gravity. Twelve rowing athletes (4 women, aged 27.2 ± 7.4 years, height 179 ± 0.1 cm, mass 73.7 ± 9.4 kg) participated in two rowing sessions, spaced at least six weeks apart. One session used a short-arm centrifuge with +0.5 Gz, while the other inclined the rowing ergometer by 26.6° to mimic centrifugal loading. Participants started self-paced rowing at 30 W, increasing by 15 W every three minutes until exhaustion. We measured rowing performance, heart rate, blood pressure, ground reaction forces, leg muscle activation, and blood lactate concentration. Rowing on the centrifuge was well-tolerated without adverse events. No significant differences in heart rate, blood pressure, or blood lactate concentration were observed between conditions. Inclined rowing under artificial gravity resulted in lower power output (−33%, p < 0.001) compared to natural gravity, but produced higher mean and peak ground reaction forces (p < 0.0001) and increased leg muscle activation. Muscle activation and ground reaction forces varied with rotational direction. Rowing in artificial gravity shows promise as a strategy against cardiovascular and muscular deconditioning during long-term spaceflight, but further investigation is required to understand its long-term effects.

Acute Responses to Traditional and Cluster-Set Squat Training With and Without Blood Flow Restriction.

Cornejo-Daza, PJ, Sánchez-Valdepeñas, J, Páez-Maldonado, J, Rodiles-Guerrero, L, Boullosa, D, León-Prados, JA, Wernbom, M, and Pareja-Blanco, F. Acute responses to traditional and cluster-set squat training with and without blood flow restriction. J Strength Cond Res 38(8): 1401-1412, 2024-To compare the acute responses to different set configurations (cluster [CLU] vs. traditional [TRA]) under distinct blood flow conditions (free vs. restricted) in full-squat (SQ). Twenty resistance-trained males performed 4 protocols that differed in the set configuration (TRA: continuous repetitions; vs. CLU: 30 seconds of rest every 2 repetitions) and in the blood flow condition (FF: free-flow; vs. blood flow restriction [BFR]: 50% of arterial occlusion pressure). The relative intensity (60% 1RM), volume (3 sets of 8 repetitions), and resting time (2 minutes) were equated. Mean propulsive force (MPF), velocity (MPV) and power (MPP), and electromyography (EMG) parameters were recorded during each repetition. Tensiomyography (TMG), blood lactate, countermovement jump (CMJ) height, maximal voluntary isometric contraction, in SQ, and movement velocity against the load that elicited a 1 m·s -1 velocity at baseline (V1-load) in SQ were assessed at pre- and post-exercise. The CLU protocols allowed a better maintenance of MPF, MPV, MPP, and EMG median frequency during the exercise compared to TRA (clu-time interaction, p < 0.05). The TRA protocols experienced greater impairments post-exercise in TMG- and EMG-derived variables (clu-time interaction, p < 0.05) and SQ and CMJ performance (clu-time interaction, p = 0.08 and p < 0.05, respectively), as well as higher blood lactate concentrations (clu-time interaction, p < 0.001) than CLU. Moreover, BFR displayed decreases in TMG variables (bfr-time interaction, p < 0.01), but BFR-CLU resulted in the greatest reduction in twitch contraction time ( p < 0.001). Cluster sets reduced fatigue during and after the training session and BFR exacerbated impairments in muscle mechanical properties; however, the combination of both could improve contraction speed after exercise.

Physiological and Biomechanical Characteristics of Olympic and World-Class Rowers—Case Study

In this study, we quantified relevant biophysical characteristics of two elite rowers across a wide range of intensities. Two &lt;40-year-old male and female Olympic and World Championship finalists performed a 7 × 3 min protocol plus 1 min maximal effort on a rowing ergometer. The intensity increase resulted in maximum values of 79.4 ± 2.4 and 69.7 ± 1.5 mL/min/kg for oxygen uptake, 179.3 ± 5.7 and 152.5 ± 2.9 L/min for ventilation, 170 ± 1 and 173 ± 0 bpm for heart rate, 10.6 and 15.8 mmol/L for blood lactate concentration, and 38.1 ± 0.03 and 38.8 ± 0.03 °C for core temperature for the male and female rowers. The percentage of power corresponding to a previously conducted maximum 2000 m rowing ergometer test and the work at each step increased from 49 to 127 and 42 to 103% and from 226.8 to 398.9 J and 174.0 to 250.0 J, from low to extreme intensities, for the male and female. Concurrently, there was a decrease in cycle length and propulsive time, followed by an increase in maximal handle drive velocity, with the rise in rowing intensity. These world-class rowers seem capable of maintaining physiological and technical profiles (and a remarkable capacity to generate substantial power) at this phase of their careers possibly due to long-term engagement in elite-level training. Biophysical data provide valuable referential information for guiding rowers to improve their performance.

Cardiac diastolic maladaptation is associated with the severity of exercise intolerance in sickle cell anemia patients

This pilot study focusing on Sickle Cell Anemia (SCA) patients offers a comprehensive and integrative evaluation of respiratory, cardiovascular, hemodynamic, and metabolic variables during exercise. Knowing that diastolic dysfunction is frequent in this population, we hypothesize that a lack of cardiac adaptation through exercise might lead to premature increase in blood lactate concentrations in SCA patients, a potential trigger for acute disease complication. SCA patients were prospectively included in PHYSIO-EXDRE study and underwent a comprehensive stress test with a standardized incremental exercise protocol up to 4 mmol L−1 blood lactate concentration (BL4). Gas exchange, capillary lactate concentration and echocardiography were performed at baseline, during stress test (at ∼ 2 mmol L−1) and BL4. The population was divided into two groups and compared according to the median value of percentage of theoretical peak oxygen uptake (%V˙O2peakth\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\dot{\ ext{V}}\ ext{O}}_{2peakth}$$\\end{document}) at BL4. Twenty-nine patients were included (42 ± 12 years old, 48% of women). Most patients reached BL4 at low-intensity exercise [median value of predicted power output (W) was 37%], which corresponds to daily life activities. The median value of %V˙O2peakth\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\dot{\ ext{V}}\ ext{O}}_{2peakth}$$\\end{document} at BL4 was 39%. Interestingly, diastolic maladaptation using echocardiography during stress test along with hemoglobin concentration were independently associated to early occurrence of BL4. As BL4 occurs for low-intensity exercises, SCA patients may be subject to acidosis-related complications even during their daily life activities. Beyond assessing physical capacities, our study underlines that diastolic maladaptation during exercise is associated with an early increase in blood lactate concentration.

Risk assessment by acute bedside echocardiography prior to acute coronary angiography in patients with ST-elevation myocardial infarction: a feasibility study

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Novo Nordisk Foundation. Background Early risk assessment by hemodynamic measurements in patients with ST-elevation myocardial infarction (STEMI) could be useful for early detection of patients at risk of developing hemodynamic instability after primary percutaneous coronary intervention (pPCI). Anterior STEMI patients have larger infarct size and may be of particular interest. Transthoracic echocardiography (TTE) is a quick, non-invasive, and available tool, however, evidence regarding the use of acute TTE prior to acute coronary angiography (CAG) is limited. Purpose To assess the feasibility of acute bedside hemodynamic assessment in the cath. lab. by TTE in addition to clinical examination, and blood samples in STEMI patients without CS at arrival in the cath. lab. Methods STEMI patients without CS at hospital arrival and treated with pPCI were included in the study during a five week period. Clinical examination (Killip class), blood sampling (lactate, troponin T (TNT), proB-type natriuretic peptide (proBNP), and focused bedside 2D TTE with Doppler were performed prior to the acute CAG. The TTE protocol was focused (approx. 5 minutes) on hemodynamic measurements, infarction related complications, and differential diagnoses e.g. aortic dissection. The TTE was performed during preparation for the acute CAG. Patients were stratified in anterior- vs. non-anterior STEMI based on the culprit artery and prehospital ECG. Feasibility was estimated by all of the following echocardiographic parameters; left ventricular ejection fraction (LVEF), left ventricular outflow tract (LVOT) velocity time integral (VTI), and right ventricular function (tricuspid annular plane systolic excursion (TAPSE)). Results A total of 60 STEMI patients (aged mean 63 years, 18% female) were included, and 47% had an anterior STEMI. No differences in baseline characteristics between the two groups were found including comorbidities, clinical parameters, and time from cath. lab. arrival to first wire over the culprit lesion (median (IQR) 28 (23; 38) vs 32 (24; 40) minutes). Admission biomarkers of blood glucose, lactate, and proBNP plasma concentrations were similar between the two groups. Whereas admission TNT were higher for patients with anterior STEMI (median (IQR) 110 (37; 449) vs. 37 (20; 94) ng/L, p=0.01). The feasibility of TTE-study protocol was 93%. Patients with anterior STEMI had lower LVEF (mean: 36±11 vs. 48±9%, p=0.0003; missing: n=0), and a trend to lower LVOT VTI (19 (6.4) vs. 22 (5.0) cm, p=0.06; missing: n=4). No difference in parameters of diastolic function or TAPSE (missing: n=0) were found. None of the included patients had echocardiographic visible complications related to the infarction. Conclusion Acute TTE is to a high degree feasible and does not delay time to acute revascularization in STEMI patients. Patients with anterior STEMI have significantly higher admission TNT levels, lower LVEF, and a trend to lower LVOT VTI compared with non-anterior STEMI patients.

Differences in lactate metabolism between middle- and long-distance runners

It is important for runners and coaches to figure out the characteristics of lactate metabolism in terms of planning the proper training. This study investigated the differences in lactate production and oxidation capacities between middle- and long-distance runners by using blood lactate concentration. We hypothesized that long-distance runners have greater capacity to oxidize lactate and middle-distance runners have greater capacity to produce lactate. In this study, 14 middle- and 14 long-distance male runners performed a multi-stage incremental test until exhaustion. Each running stage was 3-minute with 1-minute rest between stages. Blood lactate concentration was measured at rest and after each stage, and some metrics associated with runner’s capacity to oxidative lactate during moderate intensity exercise were calculated. The changes in blood lactate concentration measured after the final state of the test were modeled as a biexponential time function to evaluate lactate productive and oxidative capacities after high-intensity exercise. During moderate-intensity exercise, long-distance runners showed significant decrease in blood lactate concentrations during the first few stages of the test compared to rest, indicating greater oxidation of lactate than production of lactate during moderate intensity exercise (p&lt;0.05), while middle distance runners showed slight increase in blood lactate concentrations even for the first several stages. Middle-distance runners showed significantly higher amount of lactate produced (p&lt;0.05) and greater lactate oxidation during high-intensity exercise than those in long-distance runners (p&lt;0.01), suggesting that both lactate production and oxidation of middle-distance runners were greater than those of long-distance runners during high-intensity exercise. These results suggest that characteristics of lactate metabolism in middle- and long-distance runners depend partly on exercise intensity. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.