Lower Blood Lactate Concentration Research Articles

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.

Difference in badminton-specific endurance evaluated by a newly developed on-court test between competitive levels: A pilot study of female players.

We developed a test to evaluate badminton-specific endurance. The study included 10 female badminton players. Five participants were ranked in Japan's top 100 national rankings (ranked), whereas the others were unranked (unranked). Participants reacted quickly with badminton-specific steps from the base center to the four sensors at each corner of a singles badminton court. On each set, they reacted eight times to randomized instructions at stage-specific intervals (1.2, 1.0, and 0.8 s for stages 1, 2, and 3, respectively), which were performed six times with a rest of 20 s in each stage (8 movements × 6 sets × 3 stages). On a different day, participants ran on a treadmill as a comparative test. Blood lactate concentration (BLa) was measured on each test. In the badminton-specific test, ranked participants had lower BLa (4.2 ± 1.7 mM vs. 6.3 ± 3.1 mM), with medium or large effect sizes. The average reach time to sensors was shorter in ranked participants (1.56 ± 0.03 s vs. 1.62 ± 0.07 s), with medium or large effect sizes. BLa was similar between groups, with trivial or small effect sizes in the running test. These results suggest that the newly developed test can evaluate badminton-specific endurance.

The impact of training status on firefighter task performance after acute exercise

Background: Though on-shift exercise provides firefighters structured time to maintain fitness levels needs for their job; many are concerned on-shift exercise may impair their readiness. It also remains unclear if their current fitness level is protective of potential exercise-induced decrements. Therefore, we aimed to determine if aerobic fitness and body composition impact occupational performance and physiological stress after acute exercise. Methods: 32 participants (17M/15F; 25.2 ± 4.1 yrs; 173.8 ± 9.8 cm; 75.6 ± 13.2 kg; 23.3 ± 7.4% body fat) completed 2 visits assessing fitness (VO2peak and %body fat (%BF)), and 3 experimental trials: resistance exercise (RE), aerobic exercise (AE), and rested control (CON). Each trial was followed by an occupational task assessment (OTA; 4 rounds of 10 deadlifts (set to 85 or 135lbs) and a 0.15-mile 40lb-sandbag carry) in an environmental chamber (35°C; 50% humidity). Time to complete (TTC), blood lactate concentrations (BLC), and core temperature (CT) were assessed. Participants were split into tertiles based on high, moderate, and low VO2peak and %BF. Two-way ANOVAs were used to compare fitness level by exercise condition. RESULTS: There was a main effect of VO2peak on TTC (High VO2: 1094 ± 235; Moderate VO2: 1120 ± 200; Low VO2: 1365 ± 263 sec; p < 0.01). High VO2peak participants had a shorter TTC compared to moderate or low VO2max regardless of exercise prior (ps < 0.01). There was a main effect of VO2peak on CT (High VO2: 38.1 ± 0.6; Moderate VO2: 38.2 ± 0.6; Low VO2: 38.4 ± 0.5°C; p < 0.01). High VO2peak participants had a lower CT during the OTA compared to low VO2peak regardless of exercise prior (p < 0.01). There was a main effect of %BF on TTC (High %BF: 1029 ± 150; Moderate %BF: 1098 ± 210; Low %BF: 1399 ± 259 sec; p < 0.001). High %BF participants had a longer TTC compared to average or low %BF regardless of exercise prior (ps < 0.01). There was a significant main effect of %BF on BLC (High %BF: 6.6 ± 2.8; Moderate %BF: 7.6 ± 3.0; Low %BF: 9.9 ± 3.8 mMol/L; p < 0.01). Low %BF participants had lower BLC after the OTA compared to high %BF regardless of exercise prior (p < 0.01). CT were significantly higher following AE compared to RE and CON (AE: 38.7 ± 0.3; RE: 38.5 ± 0.5; CON: 37.6 ± 0.4°C; p < 0.01). All other interaction and main effects of TTC or physiological stress variables were not significantly different based on fitness (VO2peak and %BF; ps > 0.18). CONCLUSIONS: Our findings suggest fitness (VO2peak and %BF) impacts time to complete and physiological stress during occupational tasks. However, fitness did not influence the response to occupational tasks differently based on if acute exercise (aerobic or resistance) was performed beforehand. These findings contribute to our understanding of the impact of acute on-shift exercise methods and provide relevant metrics of fitness related to firefighter occupational performance. FUNDING DISCLOSURE: There are no funding sources to disclose. 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.

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.

Steep uphill cycling using repeated transitions between seated and standing positions results in a lower blood-lactate concentration than continuous use of either seated or standing position.

This study investigated whether repeated transitions between seated and standing positions has a different physiological response compared to continuous use of either seated position or standing position during steep uphill cycling among elite cyclists. Ten elite male cyclists completed three 5-min treadmill cycling tests at an inclination of 6.8° with constant individual-based speed resulting in a work intensity close to the aerobic threshold. During the first and third test, the participants used standing position (ST test) and seated position (SE test) or vice versa, whereas in the second test, they made repeated transitions between standing and seated positions every 10 s (RT test). The last 2 min of each test was used to measure the mean values of oxygen uptake (V̇O2) and respiratory exchange ratio, which were used to calculate the metabolic rate (MR) and gross efficiency (GE). Additionally, the blood-lactate concentration before and after (Lapost) each test was determined. One-way repeated measures ANOVA was used to determine the effect of cycling position on the physiological response. No significant differences between tests were observed for the variables related to aerobic energy expenditure (i.e., V̇O2, MR and GE), whereas the RT test was associated with a significantly lower Lapost compared to the ST and SE tests. Steep uphill cycling, at an intensity close to the aerobic threshold, with repeated transitions between standing and seated positions, did not have a higher oxygen consumption; instead, the blood-lactate concentration was lower during the RT test compared to that under continuous use of either seated or standing position.

Physiological and cognitive responses to hyperoxic exercise in full water submersion

ABSTRACT The positive effects of combined hyperoxia and physical exercise on physiological parameters and cognitive functioning are established for normobaric laboratory contexts. Still, increased practicability exists in hyperbaric settings like underwater activities and SCUBA diving, where environmental and sport-specific factors might moderate effects. Improved cognition, reduced ventilation (V̇E), and lower blood lactate concentrations [Lac-] are highly relevant, especially during high-stress and rescue scenarios. Fifteen participants performed 3 × 8 min of continuous underwater fin-swimming at 25 % (low), 45 % (moderate), and 75 % (vigorous) heart rate reserve (HRR) in each test. Three separate test days differed solely by the inspiratory oxygen partial pressure (PIO2: 29 kPa, 56 kPa, and 140 kPa). V̇E was measured continuously, whereas breathing gas analysis, blood sampling, and Eriksen Flanker tasks for inhibitory control (100 stimuli) were performed post-exercise. Two-way ANOVAs with repeated measures on the factors PIO2 and exercise intensity analyzed physiological outcome variables and reactions times (RT) and accuracy (ACC) of inhibitory control. V̇E was significantly reduced for 140 kPa during moderate and vigorous and for 56 kPa during vigorous compared to 29 kPa. 56 kPa and 140 kPa showed no differences. [Lac-], post-exercise V̇CO2, and velocity were unaffected by PIO2. Faster RTs but lower ACC of inhibitory control were observed following exercise at 75 % HRR compared to rest, 25 %, and 45 % HRR, while PIO2 produced no effects. Underwater performance in hyperoxia presents reduced V̇E, possible by dampened chemoreceptor sensitivity, and effects on cognition that differ from laboratory results and emphasise the moderating role of sport-specific factors.

The Physiological and Morphological Characteristics of a Kenyan World-Class Long-Distance Runner: A Case Study*

The purpose of this study was to compare the physiological and morphological characteristics of J. Ndambiri, a Kenyan world-class long-distance runner (10,000 m personal best: 27:04.79), with runners belonging to the national corporate team (29:32.18±0:30.35). Oxygen uptake (VO2), heart rate, blood lactate concentration and stride frequency were measured during submaximal exercise on a treadmill (270, 290, 310, 330, 350 and 370 m/min velocities with 1% inclination). Peak oxygen uptake (VO2peak) was determined during the maximal exercise test. In addition, morphological parameters (length of thigh and shank, maximum circumference of thigh and shank, and cross-sectional area of the trunk, thigh and shank muscles) were determined using a tape measure and magnetic resonance imaging (MRI). Ndambiri was superior to Japanese runners in terms of not only running economy (65.0 vs 69.8 ±1.9 ml/kg/min at 330 m/min), but also blood lactate concentration (1.50 vs 2.59±0.74 mmol/l at 330 m/min), heart rate (159.8 vs 170.8±4.0 bpm at 330 m/min) during the submaximal running test and VO2peak (80.8 vs 76.3±2.4 ml/kg/min). In addition, the morphological characteristics of Ndambiri were also quite different from those of Japanese runners. In particular, Ndambiri's maximum shank circumference was much smaller than that of Japanese runners (32.0 vs 35.8±1.8 cm). Furthermore, the cross-sectional area of the gastrocnemius muscle, which composes the shank, was significantly correlated with the oxygen cost of running at 330 m/min (r=0.700). These findings indicate that the superior performance of Ndambiri is attributable to various factors such as a higher VO2peak, lower blood lactate concentration and heart rate, as well as running economy. In the future, it will be necessary to clarify the factors supporting these relationships between physiological variables and morphological characteristics.

Gastric dilatation volvulus in dogs: utility of lactate as a predictor of survival

PICO question
 In dogs presenting with gastric dilatation volvulus, is an admission or pre-operative lactate level a reliable predictor of survival to discharge?
 
 Clinical bottom line
 Category of research question
 Prognosis
 The number and type of study designs reviewed
 15 studies (12 retrospective and 3 prospective) were critically appraised
 Strength of evidence
 Moderate
 Outcomes reported
 At a population level, lower blood lactate concentration, or lactate concentration that decreases following fluid resuscitation, are associated with a better prognosis.
 At a population level, higher blood lactate concentration, or lactate concentration that fails to decrease following fluid resuscitation, is associated with a worse prognosis. However, the lower sensitivity across studies means that a high lactate, or one that does not decrease following fluid therapy, should be interpreted more cautiously than a low lactate; i.e., low lactate predicts survival better than high lactate predicts non-survival.
 In all studies, there was a significant overlap in individual blood lactate concentration between survivors and non-survivors
 Conclusion
 Blood lactate level should only be used to help guide broad, cautiously worded conversations with owners as described above. It should not be used to give a prognosis for individual patients. The overlap between survivors and non-survivors, and the high overall survival rate, means that exploratory laparotomy should be advised irrespective of the blood lactate level
 
 How to apply this evidence in practice
 The application of evidence into practice should take into account multiple factors, not limited to: individual clinical expertise, patient’s circumstances and owners’ values, country, location or clinic where you work, the individual case in front of you, the availability of therapies and resources.
 Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.

Acute Physiological Responses to Ultra Short Race-Pace Training in Competitive Swimmers.

Ultra Short Race Pace training (USRPT) is an emerging training modality devised in 2011 to deviate from high-volume swimming training that is typically prescribed. USRPT aims to replicate the exact demands of racing, through its unique prescription of race-pace velocity sets with short rest intervals. It has been surmised, with little physiological evidence, that USRPT provides swimmers with the best opportunity to optimize the conditioning, technique, and psychology aspects of racing at the most specific velocity of the relevant event, with low blood lactate concentration. The aim of this study was to examine acute physiological responses of USRPT. Fourteen swimmers were recruited to perform a USRPT set: 20 x 25 m freestyle with a 35-s rest interval. Swimmers were required to maintain the velocity of their 100 m personal best time for each sprint. Sprint performance, blood lactate, heart rate and the RPE were measured. Blood lactate was taken before, during (after every 4 sprints) and 3 minutes after the USRPT protocol. Heart rate monitors were used to profile the heart rate. Athletes reported the RPE before- and after completion of the USRPT set. Sprint times increased by 3.3-10.8% when compared to the first sprint (p < 0.01). There was high blood lactate concentration (13.6 ± 3.1mmol/l), a significant change in the RPE from 8 ± 1.6 to 18 ± 1.6 (p < 0.01) and a substantially high heart rate profile with an average HRmax of 188 ± 9 BPM. The results show the maximal intensity nature of USRPT and portray it as an anaerobic style of training.

Effect of Dark Chocolate Supplementation on Tissue Oxygenation, Metabolism, and Performance in Trained Cyclists at Altitude.

Dark chocolate (DC) is high in flavonoids and has been shown to increase nitric oxide in the blood. Increased nitric oxide has the potential to improve delivery of oxygen to muscle, especially in hypoxic conditions, such as altitude. Our aim was to assess the impact of DC supplementation on cycling performance at altitude. Twelve healthy, trained cyclists (n = 2 females, n = 10 males; age = 35 [12]years; height = 177 [7]cm; mass = 75.2 [11.0]kg; VO2max = 55 [6]ml·kg-1·min-1) were randomized to supplement with 60g of DC or placebo twice per day for 14days in a double-blind crossover study. After the 2 weeks of supplementation, the participants attended a laboratory session in which they consumed 120g of DC or placebo and then cycled for 90min at 50% peak power output, followed immediately by a 10-km time trial (TT) at simulated altitude (15% O2). The plasma concentration of blood glucose and lactate were measured before and at 15, 30, 60, and 90min during the steady-state exercise and post TT, while muscular and prefrontal cortex oxygenation was measured continuously throughout exercise using near-infrared spectroscopy. DC resulted in a higher concentration of blood glucose (5.5 [0.5] vs. 5.3 [0.9]mmol/L) throughout the trial and lower blood lactate concentration following the TT (7.7 [1.92] vs. 10.0 [4.6]mmol/L) compared with the placebo. DC had no effect on the TT performance (19.04 [2.16] vs. 19.21 ± 1.96min) or oxygenation status in either the prefrontal cortex or muscle. The authors conclude that, although it provided some metabolic benefit, DC is not effective as an ergogenic aid during TT cycling at simulated altitude.

AUTONOMIC, CARDIOVASCULAR &amp; PHYSIOLOGICAL RESPONSES IN STRENGTH TRAINING PROTOCOLS

ABSTRACT Introduction Strength training is a recurrent practice among several publics and the topic of several studies, yet there is a shortage of previous studies that analyzed these parameters in the same subjects in training sessions involving volume, interval and different repetitions maximum ranges. Objective The study was aimed at measuring and comparing the acute effect of different ST (strength training) protocols on HR (heart rate), HRV (heart rate variability), [LAC] (lactate concentration), [CK] (creatine kinase) and SPE (subjective perceived exertion). Methods Eleven individuals with previous experience were recruited and in three sessions they performed three different training models, namely: high load (4 sets at 90% of 1RM, 180s rest between sets), medium load (3 sets at 75% of 1 RM, 90s rest between sets), and low load (2 sets at 50% of 1 RM, 45s rest between sets) in free squat, bench press, deadlift and bent-over row exercises. Results There was no difference in CK between low load (resistance) and medium load (hypertrophy) (p = 0.60), between resistance and high load (strength) (p = 0.84), and between hypertrophy and strength (p = 0.91), while there was higher lactate accumulation in training with medium and low loads in comparison to training with high loads (p &lt;0.001). Conclusion It can be noted that workouts with high loads, few repetitions and longer intervals (maximum strength) generate lower blood lactate concentrations and SPE values when compared to training with lower loads and shorter intervals (resistance training and hypertrophy). Additionally, when evaluating autonomic and cardiovascular variables, it would appear that manipulating the percentage of 1RM and the interval time does not generate significant changes in HRV, blood pressure (BP) and HR when the repetitions are executed until failure. Level of evidence II; Prospective comparative study.

Greater exercise tolerance in COPD during acute interval, compared to equivalent constant-load, cycle exercise: physiological mechanisms.

Exercise intolerance is common in chronic obstructive pulmonary disease (COPD) patients. In patients with COPD, we compared an interval exercise (IE) protocol (alternating 30s at 100% peak work rate (WRpeak ) with 30s at 50% WRpeak ) with moderate-intensity constant-load exercise (CLE) at 75% WRpeak , which yielded the same work rate. Exercise endurance time and total work output were almost twice as high for IE than CLE. At exercise isotime (when work completed was the same between IE and CLE), IE was associated with less dynamic hyperinflation, lower blood lactate concentration, and greater respiratory and locomotor muscle oxygenation, but there were no differences in ventilation or cardiac output. However, at the limit of tolerance for each modality, dynamic hyperinflation was not different between IE and CLE, while blood lactate remained lower and muscle oxygenation higher with IE. Taken together, these findings suggest that dynamic hyperinflation and not muscle-based factors dictate the limits of tolerance in these COPD patients. The relative importance of ventilatory, circulatory and peripheral muscle factors in determining tolerance to exercise in patients with chronic obstructive pulmonary disease (COPD) is not known. In 12 COPD patients (forced expiratory volume in one second: 58±17%pred.) we measured ventilation, cardiac output, dynamic hyperinflation, local muscle oxygenation, blood lactate and time to exhaustion during (a) interval exercise (IE) consisting of 30s at 100% peak work rate alternating with 30s at 50%, and (b) constant-load exercise (CLE) at 75% peak work rate, designed to produce the same average work rate. Exercise time was substantially longer during IE than CLE (19.5±4.8 versus 11.4±2.1min, p=0.0001). Total work output was therefore greater during IE than CLE (81.3±27.7 versus 48.9±23.8kJ, p=0.0001). Dynamic hyperinflation (assessed by changes from baseline in inspiratory capacity, ΔIC) was less during IE than CLE at CLE exhaustion time (isotime, p=0.009), but was similar at exhaustion (ΔICCLE : -0.38±0.10 versus ΔICIE : -0.33±0.12l, p=0.102). In contrast, at isotime, minute ventilation, cardiac output and systemic oxygen delivery did not differ between protocols (P>0.05). At exhaustion in both protocols, the vastus lateralis and intercostal muscle oxygen saturation were higher in IE than CLE (p=0.014 and p=0.0002, respectively) and blood lactate concentrations were lower (4.9±2.4mmoll-1 versus 6.4±2.2mmoll-1 , p=0.039). These results suggest that (1) exercise tolerance with COPD is limited by dynamic hyperinflation; and (2) cyclically lower (50%) effort intervals in IE help to preserve muscle oxygenation and reduce metabolic acidosis compared with CLE at the same average work rate; but these factors do not appear to determine time to exhaustion.

Physiological Comparisons of Elite Male Visma Ski Classics and National Level Cross-Country Skiers During Uphill Treadmill Roller Skiing.

Longer distance cross-country ski (14–220 km) races such as the Visma Ski Classics (VSC) has recently gained attention in addition to the traditional Olympic distances (5–50 km) associated with cross-country (XC) skiing. These long-distance races are characterized by extensive use of the upper body while double poling (DP). While there is a substantial amount of research on Olympic distance XC skiing, the physiological capacities of VSC skiers has not yet been explored. We recruited seven elite male VSC skiers and seven well-trained national level male XC skiers to undergo three tests in the laboratory: (1) a one repetition maximum (1RM) strength test in a cable pulldown; (2) roller skiing tests on a treadmill (10.5% inclination) for determination of gross efficiency (GE) at submaximal speeds (8 and 10 km·h−1) in DP and diagonal stride (DS); (3) two ramp protocols to exhaustion (15% inclination, starting speed 7 km·h−1) in DP and DS for the assessment of peak and maximal oxygen uptake (O2peak and O2max), respectively. Compared with the national level XC skiers, the VSC skiers performed similar in the 1RM cable pulldown, displayed 12.2% higher GE in DP at 8 km·h−1 but did not display any difference at 10 km·h−1, and had lower blood lactate concentration and heart rate at both submaximal speeds. The VSC skiers had longer time to exhaustion compared with the national level XC skiers during the two ramp protocols in DS (18%) and in DP (29%). The O2max was 10% higher in DS compared with DP, with no differences between the groups. The O2peak/O2max-ratio of 90% did not differ between the two groups. In conclusion, the main differences were lower cardiorespiratory and metabolic responses at submaximal speeds as well as longer time to exhaustion in VSC skiers compared with national level XC skiers. This suggest efficiency to be the main difference between VSC and national level XC skiers.

Beta-Alanine Supplementation Improved 10-km Running Time Trial in Physically Active Adults.

The purpose of this study was to investigate the effects of β-alanine supplementation on a 10 km running time trial and lactate concentration in physically active adults. Sixteen healthy subjects were divided randomly into two groups: β-alanine (n = 8) and placebo group (n = 8). The experimental group ingested 5 g/day of β-alanine plus 1 g of resistant starch, and control group ingested 6 g of resistant starch, both for 23 days. Time to complete a 10-km running time trial and lactate concentration following the test were assessed at baseline and post 23 days. The running training program was performed three times per week on non-consecutive days (day 1: running 7 km; day 2: six sprints of 500 m at maximum speed with 2 min of recovery; day 3: running 12 km). The time to complete a 10-km running time trial decreased significantly only for the β-alanine group (Pre = 3441 ± 326.7, Post = 3209 ± 270.5 s, p < 0.05). When analyzing the delta (Time post minus Time at baseline value) there was a statistically significant difference between the β-alanine vs placebo group (-168.8 ± 156.6 vs. -53.60 ± 78.81 s, p = 0.007), respectively. In addition, the β-alanine group presented lower blood lactate concentration after the 10-km test (β-alanine: Pre = 8.45 ± 1.94 vs. Post = 6.95 ± 2.44 mmol/L; Placebo: Pre = 8.7 ± 3.0 vs. Post = 10.8 ± 2.5 mmol/L, p = 0.03). In conclusion, β-alanine supplementation improved the 10-km running time trial and reduced lactate concentration in physically active adults.

Effect of chronic lactate administration prior to endurance training on mitochondrial adaptations in mouse skeletal muscle

Lactate is considered as not only an oxidizable fuel, but also a signal molecule inducing mitochondrial biogenesis. In this study, we hypothesized that lactate administration prior to training augments mitochondrial adaptations. ICR male mice were randomly assigned to Con (n=9), Tr (n=7) or La+Tr (n=8) group. Mice in Tr and La+Tr were performed treadmill running (20 m/min, 60 min) immediately after administration of PBS (same volume as lactate) or sodium lactate (1 mg/g BW) via i.p. injection for 21 consecutive days. Mice in Con were administrated same volume of PBS on the same days. All the mice were performed lactate tolerance test (LTT: i.p. injection of 1 mg/g BW of sodium lactate) 24h after final training. Blood samples were collected pre, 5, 15, 30, 60 and 180 minutes after the lactate administration. Soleus and plantaris muscle were taken for the biochemical analysis 24h after LTT. As a result, some mitochondrial enzyme activities in soleus and plantaris muscle were significantly higher in La+Tr than Tr (CS: P&lt;0.05, β‐HAD: P=0.05, COX: P&lt;0.01 in soleus, CS: n.s., β‐HAD: n.s., COX: P&lt;0.05 in plantaris). However, mitochondrial OXPHOS protein content was not different between Tr and La+Tr. MCT1 protein content was significantly higher in La+Tr than Con (+18%; P&lt;0.01) in plantaris muscle, but not MCT4. As a result of LTT, blood lactate concentrations after lactate administration were significantly lower in Tr (60 min: P&lt;0.05 vs. Con) and La+Tr (30 min: p&lt;0.01, 60 min: P&lt;0.01 vs. Con) than Con. These data indicate that lactate upregulates mitochondria functionally, and that lactate administration increased MCT1 protein content leading to lower blood lactate concentration after lactate administration.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Atypical myopathy in the South‐East of England: Clinicopathological data and outcome in hospitalised horses

SummaryThis retrospective case series describes clinicopathological data and outcome of hospitalised atypical myopathy (AM) cases in the South‐East of England. The study aimed to describe the frequency of metabolic abnormalities (hyperglycaemia, hyperlactataemia, hypertriglyceridaemia) and outcome in AM cases in the South‐East of England and test the hypothesis that serum creatine kinase (CK) activity and blood glucose, lactate and triglyceride concentrations are associated with outcome. Medical records (2011–2017) from three referral hospitals were reviewed for cases with a clinical diagnosis of AM. A previously described algorithm was applied and cases were included if a diagnosis of AM was considered highly likely. In cases admitted after 2013 known or possible exposure to sycamore trees was also required for inclusion. Sixty‐four animals were included, 44% (28/64) survived. Hyperglycaemia, hyperlactataemia and hypertriglyceridaemia were present in 76%, 89% and 92% of horses on admission, respectively. Survivors had lower blood lactate concentrations (survivors: median 3.5 mmol/L; range 0.5–10.4 mmol/L vs. nonsurvivors: median 7.3 mmol/L; range 2.5–16.5 mmol/L; P = 0.011) and serum CK activities (survivors: median 38,369 U/L; range 7024–570,498 U/L vs. nonsurvivors: median 172,687 U/L; range 2036–570,953 U/L; P = 0.027) on admission when compared to nonsurvivors. Increasing CK activity (P = 0.008) and triglyceride concentrations (P = 0.038) during hospitalisation were associated with nonsurvival. More nonsurvivors required sedation (18/29; 62.1% vs. 4/22; 18.2%; P = 0.002). The prognosis for hospitalised horses with AM is guarded and outcome in this population was associated with admission CK activity and lactate concentrations, and increasing CK activity and triglyceride concentrations and need for sedation during hospitalisation.

The Activity Demands and Physiological Responses Encountered During Basketball Match-Play: A Systematic Review.

Basketball is a popular, court-based team sport that has been extensively studied over the last decade. The purpose of this article was to provide a systematic review regarding the activity demands and physiological responses experienced during basketball match-play according to playing period, playing position, playing level, geographical location, and sex. An electronic database search of relevant articles published prior to 30 September 2016 was performed with PubMed, MEDLINE, ERIC, Google Scholar, SCIndex, and ScienceDirect. Studies that measured activity demands and/or physiological responses during basketball match-play were included. Following screening, 25 articles remained for review. During live playing time across 40-min matches, male and female basketball players travel 5-6km at average physiological intensities above lactate threshold and 85% of maximal heart rate (HR). Temporal comparisons show a reduction in vigorous activities in the fourth quarter, likely contributing to lower blood lactate concentrations and HR responses evident towards the end of matches. Guards tend to perform a higher percentage of live playing time sprinting and performing high-intensity shuffling compared with forwards and centers. Guards also perform less standing and walking during match-play compared with forwards and centers. Variations in activity demands likely account for the higher blood lactate concentrations and HR responses observed for guards compared with forwards and centers. Furthermore, higher-level players perform a greater intermittent workload than lower-level players. Moreover, geographical differences may exist in the activity demands (distance and frequency) and physiological responses between Australian, African, and European basketball players, whereby Australian players sustain greater workloads. While activity demands and physiological data vary across playing positions, playing levels, and geographical locations, male and female players competing at the same level experience similar demands. The current results provide a detailed description of the specific requirements placed on basketball players during match-play according to playing period, playing level, playing position, geographical location, and sex, which may be useful in the development of individualized basketball training drills.

Oxygen saturation and lactate concentration gradient from the right atrium to the pulmonary artery in the immediate postoperative following cardiac surgery with extracorporeal circulation.

ObjectiveThis prospective study aimed to characterize the changes in blood lactate concentration and blood oxygen saturation in patients during the immediate postoperative period of cardiac surgery with extracorporeal circulation.MethodsBlood samples were collected from 35 patients in a rapid and random order from the arterial line and from the proximal and distal port of a pulmonary artery catheter.ResultsThe results showed no statistically significant differences between the blood oxygen saturation in the right atrium (72% ± 0.11%) and the blood oxygen saturation in the pulmonary artery (71% ± 0.08%). The blood lactate concentration in the right atrium was 1.7mmol/L ± 0.5mmol/L, and the blood lactate concentration in the pulmonary artery was 1.6mmol/L ± 0.5mmol/L (p < 0.0005).ConclusionThe difference between the blood lactate concentration in the right atrium and the blood lactate concentration in the pulmonary artery might be a consequence of the low blood lactate concentration in the blood from the coronary sinus, as it constitutes an important substrate for the myocardium during this period. The lack of differences between the blood oxygen saturation in the right atrium and the percentage of blood oxygen saturation in the pulmonary artery suggests a lower oxygen extraction by the myocardium given a lower oxygen consumption.

The Association Between MCT1 T1470A Polymorphism and Power-Oriented Athletic Performance.

The purpose of this study was to investigate the effects of the MCT1 T1470A polymorphism (rs1049434) on power-oriented performance and lactate concentration during or after cycling sprints in Japanese wrestlers. Participants (199 wrestlers and 649 controls) were genotyped for the MCT1 T1470A genotype (rs1049434) using the TaqMan® Assay. All wrestlers were international (n=77) or national (n=122) level athletes. Among them, 46 wrestlers performed 2 anaerobic performance tests, a 30-s Wingate Anaerobic test (WAnT) and a series of 10 maximal effort 10-s sprints on a cycle ergometer. Blood lactate levels were measured before, during, and after the tests. In the A-allele recessive model (AA vs. TA+TT), the frequency of the AA genotype was significantly higher in all wrestlers than in controls (p=0.037). Wrestlers with AA genotype had lower blood lactate concentrations than those with TA+TT genotype at 10 min after the WAnT and following the 5th and the final set of repeated cycling sprints (p<0.05). The AA genotype of the MCT1 T1470A polymorphism is over-represented in wrestlers compared with controls and is associated with lower blood lactate concentrations after 30-s WAnT and during intermittent sprint tests in Japanese wrestlers.

Betalain-Rich Concentrate Supplementation Improves Exercise Performance in Competitive Runners.

This study aimed to determine the effects of a betalain-rich concentrate (BRC) of red beets, containing antioxidant and anti-inflammatory properties, on performance and exercise-related muscle damage. Thirteen (25.3 ± 5.4 years) competitive male runners completed two double-blind, cross-over, randomized trials (BRC and control) separated by seven days. Each trial was preceded by six days of supplementation with 100 mg of BRC or control. On the seventh day, exercise trials commenced 150 min after supplementation with 50 mg BRC or control and consisted of 30 min of treadmill running (77 ± 4% VO2max) followed by a 5-km time trial (TT). During exercise at the same intensity, BRC resulted in a 3% lower heart rate, a 15% lower rate of perceived exertion (RPE) and a 14% lower blood lactate concentration compared to the control (p = 0.05). Five-kilometer TT duration (23.0 ± 4.2 versus 23.6 ± 4.0 min) was faster in 10 of the 13 subjects, and RPE was lower (p < 0.05) with the BRC treatment compared to the control. Lactate dehydrogenase, a marker of muscle damage, increased less from baseline to immediately and 30 min after the 5-km TT with the BRC treatment, despite no differences in subjective measures of muscle soreness and fatigue. In summary, BRC supplementation improved 5-km performance time in male competitive runners.