Peak Blood Lactate Concentration Research Articles

Can Neuromuscular Electrical Stimulation Enhance the Effect of Sprint Interval Training?

The aim of this study was to determine the effects of subtetanic neuromuscular electrical stimulation combined with voluntary exercise between repeated Wingate tests on sprint exercise performance and blood lactate accumulation during sprint interval training. Fifteen healthy young males volunteered. After 1-min baseline, participants underwent the Wingate test twice. They performed a 4-min intervention between tests: neuromuscular electrical stimulation with free-weight cycling or voluntary cycling alone [43.6 (8.0) watts], which matched oxygen consumption with neuromuscular electrical stimulation with free-weight cycling. The blood lactate concentration was assessed at the end of the baseline, at 3-min intervention, and on recovery at 1, 3, 5, and 10 min after the second Wingate test. Peak and mean blood lactate concentration during recovery were significantly greater with neuromuscular electrical stimulation with free-weight cycling than voluntary cycling alone (P>0.036 and P=0.011, respectively). Peak power, mean power, and rate of decline (fatigue index) were not significantly different between conditions in both Wingate tests (condition/interaction all P>0.300, partial η2<0.1). Subtetanic neuromuscular electrical stimulation combined with voluntary exercise indicated similar exercise performance and fatigue levels during Wingate tests, but enhanced blood lactate accumulation compared to oxygen consumption-matched voluntary cycling during sprint interval training.

Lamax: determining the optimal test duration for maximal lactate formation rate during all-out sprint cycle ergometry.

This study aimed to ascertain the optimal test duration to elicit the highest maximal lactate formation rate ( Lamax), whilst exploring the underpinning energetics, and identifying the optimal blood lactate sampling period. Fifteen trained to well-trained males (age 27 ± 6years; peak power: 1134 ± 174W) participated in a randomised cross-over design completing three all-out sprint cycling tests of differing test durations (10, 15, and 30s). Peak and mean power output (W and W.kg-1), oxygen uptake, and blood lactate concentrations were measured. Lamax and energetic contributions (phosphagen, glycolytic, and oxidative) were determined using these parameters. The shortest test duration of 10s elicited a significantly (p = 0.003; p < 0.001) higher Lamax (0.86 ± 0.17mmol.L-1.s-1; 95% CI 0.802-0.974) compared with both 15s (0.68 ± 0.18mmol.L-1.s-1; 95% CI 0.596-0.794) and 30s (0.45 ± 0.07mmol.L-1.s-1; 95% CI 0.410-0.487). Differences in Lamax were associated with large effect sizes (d = 1.07, d = 3.15). We observed 81% of the PCr and 53% of the glycolytic work completed over the 30s sprint duration was attained after 10s. BLamaxpost were achieved at 5 ± 2min (ttest 10s), 6 ± 2min (ttest 15s), and 7 ± 2min (ttest 30s), respectively. Our findings demonstrated a 10s test duration elicited the highest Lamax. Furthermore, the 10s test duration mitigated the influence of the oxidative metabolism during all-out cycling. The optimal sample time to determine peak blood lactate concentration following 10s was 5 ± 2min.

Calculation of a conversion factor for estimating the glycolytic contribution in exercise from post-exercise blood lactate concentration.

Purpose: Often, the glycolytic contribution in a bout of heavy or severe intensity exercise is estimated by multiplying the increase in blood lactate concentration above resting levels that is engendered by the exercise (in mM) by 3.3 (or 3) mL·kg-1 per mM. Our purpose was to verify the value of this conversion factor, using methods that were completely different from those of the original studies. Methods: Six women (mean ± SD), age, 23 ± 1year; VO2max, 46 ± 4mL·kg-1·min-1) and three men (23 ± 0years; 54 ± 8mL·kg-1·min-1) completed 6min of heavy intensity exercise in conditions of normoxia and hypoxia (FIO2, ∼12%). VO2 was measured throughout the exercise and 7min of recovery. The increase in glycolytic contribution was estimated as the reduction in aerobic contribution in hypoxia, after correction for the effects of hypoxia on the oxygen demand and on the contribution from phosphocreatine. The peak post-exercise blood lactate concentration was measured in fingerstick blood samples. Results: The ratio between the increase in estimated glycolytic contribution (in mL·kg-1) in hypoxia and the increase in peak blood lactate concentration (in mM) yielded an oxygen equivalent of 3.4 ± 0.4mL·kg-1 per mM (range, 2.6mL·kg-1 per mM to 4.0mL·kg-1 per mM) for cycle ergometer exercise. Conclusion: These results generally support the use of a common conversion factor to calculate the glycolytic contribution from post-exercise blood lactate concentrations. However, there is some inter-individual variability in the conversion factor.

3-min All-out Test to Evaluate Aerobic and Anaerobic Indexes in Court Team Sports.

This study aimed to test the reproducibility of the 3-min all-out effort applied using shuttle running and compare its values to aerobic parameters. On the first day, 14 futsal players underwent an exhaustive test to determine the maximal incremental speed (MIS) and anaerobic threshold (AnT). On the second day, the participants performed the 3-min all-out effort (n=14), which was repeated after 48 h (third day) to test its reproducibility (n=11). Peak oxygen consumption (V̇ O2PEAK) and peak blood lactate concentrations ([La-]) were determined from 3-min all-out efforts performed through a 20-m shuttle run on the official court. The distance covered, mean speed, and critical speed (CS) during the 3-min all-out presented direct relationships with aerobic parameters determined through the incremental test (r>0.62). The distance covered above CS (D') presented a direct relationship with peak lactate concentrations induced by a 3-min all-out effort (r=0.81). Despite the acceptable levels of reproducibility observed for most of the 3-min all-out variables, the minimal detectable change for D' was high (72%). Our results demonstrated the potential use of mean speed to evaluate aerobic fitness. However, the applicability of the 3-min all-out shuttle run test to monitor training adaptations should be avoided, at least in nonexperienced athletes.

Validation of the maximal cardiopulmonary exercise test in adolescents with major depressive disorder and comparison of cardiorespiratory fitness with sex- and age-related control values

Endurance training has been shown to be effective in treating adolescents with major depressive disorder (MDD). To integrate endurance training into the therapeutic setting and the adolescents' daily lives, the current performance status of the adolescents should be accurately assessed. This study aims to examine adolescents with MDD concerning exhaustion criteria during a cardiopulmonary exercise test (CPET), as well as to compare the values obtained thereon with sex- and age-related control values. The study included a retrospective examination of exhaustion criteria ((i) oxygen consumption (V̇O2) plateau, (ii) peak respiratory exchange ratio (RERpeak) > 1.0, (iii) peak heart rate (HRpeak) ≥ 95% of the age-predicted maximal HR, and (iv) peak blood lactate concentration (BLCpeak) > 8.0 mmol⋅L−1) during a graded CPET on a cycle ergometer in adolescents with MDD (n = 57). Subsequently, maximal V̇O2, peak minute ventilation, V̇O2 at the first ventilatory threshold, and peak work rate of participants who met at least two of four criteria were compared with published control values using an independent-sample t-test. Thirty-three percent of the total population achieved a V̇O2 plateau and 75% a RERpeak > 1.0. The HR and BLC criteria were met by 19% and 22%, respectively. T-test results revealed significant differences between adolescents with MDD and control values for all outcomes. Adolescents with MDD achieved between 56% and 83% of control values. Conclusions: The study shows that compared with control values, fewer adolescents with MDD achieve the exhaustion criteria on a CPET and adolescents with MDD have significantly lower cardiorespiratory fitness. Clinical trial registration: No. U1111-1145–1854.What is Known:• It is already known that endurance training has a positive effect on depressive symptoms.What is New:• A relevant proportion of adolescents with major depressive disorder do not achieve their V̇O2max during a graded cardiopulmonary exercise test.• Adolescents with major depressive disorder have significantly lower cardiorespiratory fitness compared to sex- and age-related control values.

Sex- and age-related differences in the rating of perceived exertion after high-intensity rowing exercise during childhood and adolescence.

The present study aimed to evaluate the effects of age and sex on the rating of perceived exertion (RPE) during high-intensity exercise and determine whether mechanical and physiological parameters could be predictors of RPE during childhood and adolescence. Forty-three boys and 36 girls performed a 60-s all-out test on a rowing ergometer and were categorized by age group (10.0-11.9; 12.0-13.9; 14.0-15.9; 16.0-17.9 years) and sex. Ratings of perceived exertion were assessed using the 6-20 RPE and CR-10 scales and analyzed with respect to mechanical work rate (Wtot ), post-exercise peak blood lactate concentration ([La]peak ), and peak minute ventilation (V̇Epeak ). Multilevel regression modeling revealed a significant influence of Wtot , [La]peak and V̇Epeak on 6-20 RPE and CR-10 scores (r2 =.34 and .36, p < .001, respectively). However, while boys perceived high-intensity exercise as being subjectively more difficult than girls at all ages (p < .05) except 12.0-13.9 years, significant higher mechanical work rate and greater associated metabolic responses in boys than girls were only found from the age of 14 years (Wtot and V̇Epeak ) or 16 years ([La]peak ), suggesting that the association between RPE and mechanical/physiological parameters could not be held before the age of 12 years. To conclude, RPE increased with increasing age, with boys exhibiting higher scores than girls at all ages except 12.0-13.9 years. This finding is probably explained by the higher Wtot and greater concomitant metabolic responses in boys at the time of puberty. However, other factors should be considered at least in children before the age of 12 years.

Within-season Adaptations in Physical, Physiological and Technical-tactical Performance of Experimented Futsal Players

This study analysed the seasonal variations in futsal players’ physical, physiological, and technical–tactical performance. Eight senior futsal players from the same team were monitored at three time points in the season (beginning of the preseason, middle of the first half of the season, and middle of the second half of the season). A progressive and intermittent shuttle-running test (the futsal intermittent endurance test) was applied to collect the following variables: maximum velocity, distance covered, total distance covered, test duration, initial heart rate, peak heart rate, peak blood lactate concentration, and rating of perceived exertion. In addition, different match-performance variables were assessed during a simulated futsal match (goals scored, shots on goal, successful passes, balls lost, balls recovered, and goals conceded). Results indicated that the physiological variables of initial heart rate (p&lt;.001, η2=.862) and peak blood lactate concentration (p=.001, η2=.640) significantly varied over the course of the season. However, no significant differences were found in the physical and technical–tactical variables. This study has implications for sport practitioners; specifically, it emphasizes that preseason and in-season training load periodization enhances the physiological fitness of top-level futsal players, although their physical and technical–tactical performance remained relatively stable.

Higher Oxygen Uptake And Heart Rate Response In Recovery From Acute High Intensity Interval Exercise

Optimizing energy expenditure is paramount to achieving negative energy balance and promoting weight loss. High intensity interval exercise (HIIE) has been popularized for its ability to reduce body fat despite its time efficiency, yet it is unknown if the majority of calories burned during acute HIIE stems from completion of each interval or subsequent recovery period. Moreover, it is thought that the adaptive response to HIIE is mediated by the acute metabolic stress, but it is unknown if this stems from the interval or recovery phase of training. PURPOSE: To compare oxygen uptake (VO2) and heart values (HR) acquired during HIIE and in subsequent recovery to various HIIE regimens. METHODS: Data from 6 previously-published studies requiring various cycling-based HIIE regimens were analyzed from 89 healthy and active men and women (age, BMI, PPO, and VO2max = 25 ± 6 yr, 24 ± 3 kg/m2, 276 ± 59 W, and 40 ± 7 mL/kg/min). HIIE protocols included six to twelve 30 s - 2.5 min efforts at intensities ranging from 70 - 85 %PPO, with recovery periods ranging from 30 - 75 s. During exercise, VO2, HR, and blood lactate concentration (BLa) were acquired. RESULTS: HIIE bouts elicited peak HR, VO2, and BLa equal to 90 ± 6 %HRmax, 76 ± 12 %VO2max, and 10 ± 4 mM, respectively, and calorie expenditure was equal to 173 ± 47 kcal. Paired t-test revealed significantly higher VO2 (1.95 ± 0.46 L/min vs. 2.02 ± 0.46 L/min, p < 0.001) and HR (158 ± 14 b/min vs. 161 ± 15 b/min, p < 0.001) during recovery from acute HIIE versus the intervals. Significant inverse associations were demonstrated between VO2max and peak VO2 (r = -0.40, p < 0.001) and peak HR (r = -0.30, p = 0.004) attained during HIIE. CONCLUSIONS: Data reveal a significantly higher VO2 during recovery from HIIE compared to each interval, which may be due to slow O2 kinetics of these average fitness adults. HR was also higher in recovery suggesting a severe stress on the cardiovascular system not only during each interval, but also in recovery despite the low power outputs completed. More fit participants showed a blunted VO2 and HR response to HIIE suggesting that they may be at lower relative intensities versus less fit individuals. The structure of recovery periods as well as the interval efforts may be modified by clinicians to optimize calorie expenditure and metabolic stress of acute HIIE.

Effect of Sodium Bicarbonate Supplementation on Muscle Performance and Muscle Damage: A Double Blind, Randomized Crossover Study

Sodium bicarbonate (NaHCO3) has been used as an ergogenic substance during high-intensity exercises. Therefore, the aim of the present study was to investigate the effects of NaHCO3 supplementation on external and internal load parameters during isokinetic exercise in trained subjects. Ten subjects were tested on two occasions: after ingesting 0.3 g.kg-1 of body mass of NaHCO3 or placebo. Maximum voluntary isometric contraction was performed before and after a dynamic protocol consisting of 10 series of 10 movements of flexion/extension of the knee extensors at 120° s-1 at an interval of 60 s between series. Outcomes considered were: peak torque (isokinetic dynamometry), blood lactate and creatine concentration (CK), analysis of perceptions of effort (OMNI scale), pain (visual analog scale) and recovery (scale raging 6 to 20). Performance was assessed using peak torque values. Muscle damage was assessed prior and 24 h post exercise. The subjective perceptions of effort, pain and recovery were assessed at different times and the internal load of the session was assessed 30 min post-effort. Although significant reductions in peak torque were noted both in isometric (NaHCO3:-29.11 ± 22.95%, Placebo: −23.51 ± 15.23%; p = 0.38) and isokinetic strength (NaHCO3:-23.0 ± 13.9%, Placebo:-19.6 ± 9.1%; p = 0.09), there was no effect of supplementation on performance (p > 0.05). The blood CK concentrations (NaHCO3: pre:225.3 ± 135.9 U/L, post: 418.4 ± 318.4 U/L; Placebo: pre:238 ± 94.03 U/L, post:486 ± 336.6 U/L) increased after protocol (p = 0.005), however, without differences between conditions. In conclusion, the NaHCO3 did not attribute benefits in performance or in parameters related to the internal load of exercise.

L-carnitine does not improve valproic acid poisoning management: a cohort study with toxicokinetics and concentration/effect relationships

BackgroundValproic acid (VPA) poisoning is responsible for life-threatening neurological and metabolic impairments. Despite only low-level evidence of effectiveness, L-carnitine has been used for years to prevent or reverse VPA-related toxicity. We aimed to evaluate the effects of L-carnitine used to treat acute VPA poisoning on the time-course of plasma VPA concentrations and VPA-related toxicity. We designed a single-center cohort study including all VPA-poisoned patients admitted to the intensive care unit. We studied VPA toxicokinetics using a nonlinear mixed-effects model-based population approach and modeled individual plasma VPA/blood lactate concentration relationships. Then, we evaluated L-carnitine-attributed effects by comparing VPA elimination half-lives and time-courses of blood lactate levels and organ dysfunction [assessed by the Sequential Organ Failure Assessment (SOFA) score] between matched L-carnitine-treated and non-treated patients using a multivariate analysis including a propensity score.ResultsSixty-nine VPA-poisoned patients (40F/29 M; age, 41 years [32–47]) (median [25th–75th percentiles]; SOFA score, 4 [1–6]) were included. The presumed VPA ingested dose was 15 g [10–32]. Plasma VPA concentration on admission was 231 mg/L [147–415]. The most common manifestations were coma (70%), hyperlactatemia (3.9 mmol/L [2.7–4.9]) and hyperammonemia (127 mmol/L [92–159]). VPA toxicokinetics well fitted a one-compartment linear model with a mean elimination half-life of 22.9 h (coefficient of variation, 28.1%). Plasma VPA (C)/blood lactate concentration (E) relationships were well described by an exponential growth equation [E={E}_{0}times {e}^{kcdot C}; with baseline E0 = 1.3 mmol/L (43.9%) and rate constant of the effect, k = 0.003 L/mg (59.5%)]. Based on a multivariate analysis, peak blood lactate concentration was the only factor independently associated with L-carnitine administration (odds ratio, 1.9, 95% confidence interval, 1.2–2.8; P = 0.004). We found no significant contribution of L-carnitine to enhancing VPA elimination, accelerating blood lactate level normalization and/or preventing organ dysfunction.ConclusionsVPA poisoning results in severe toxicity. While L-carnitine does not contribute to enhancing VPA clearance, its impact on accelerating blood lactate level normalization and/or preventing organ dysfunction remains uncertain. Investigating VPA toxicokinetics and concentration/effect relationships may help understanding how to improve VPA-poisoned patient management.

Energetics of Floor Gymnastics: Aerobic and Anaerobic Share in Male and Female Sub-elite Gymnasts

BackgroundArtistic gymnastics is a popular Olympic discipline where female athletes compete in four and male athletes in six events with floor exercise having the longest competition duration in Women’s and Men’s artistic gymnastics (WAG, MAG). To date no valid information on the energetics of floor gymnastics is available although this may be important for specific conditioning programming. This study evaluated the metabolic profile of a simulated floor competition in sub-elite gymnasts.Methods17 (9 male, 8 female) sub-elite gymnasts aged 22.5 ± 2.6y took part in a floor-training-competition where oxygen uptake was measured during and until 15 min post-exercise. Additionally, resting and peak blood lactate concentration after exercise were obtained. The PCr-LA-O2 method was used to calculate the metabolic energy and the relative aerobic (WAER), anaerobic alactic (WPCr) and anaerobic lactic (WBLC) energy contribution. Further, the athletes completed a 30 s Bosco-jumping test, a countermovement jump and a drop jump.ResultsThe competition scores were 9.2 (CI:8.9–9.3) in WAG and 10.6 (CI:10.4–10.9) in MAG. The metabolic profile of the floor routine was mainly aerobic (58.9%, CI: 56.0–61.8%) followed by the anaerobic alactic (24.2%, CI: 21.3–27.1%) and anaerobic lactic shares (16.9%, CI:14.9–18.8%). While sex had a significant (p = .010, d = 1.207) large effect on energy contribution, this was not the case for competition duration (p = .728, d = 0.061). Relative energy contribution of WAG and MAG differed in WAER (64.0 ± 4.7% vs. 54.4 ± 6.8%, p = .004, d = 1.739) but not in WPCr (21.3 ± 6.1% vs. 26.7 ± 8.0%, p = .144, d = 0.801) and WBLC (14.7 ± 5.4% vs. 18.9 ± 4.2%, p = .085, d = 0.954). Further no correlation between any energy share and performance was found but between WPCr and training experience (r = .680, p = .044) and WBLC and competition level (r = .668, p = .049).ConclusionThe results show a predominant aerobic energy contribution and a considerable anaerobic contribution with no significant difference between anaerobic shares. Consequently, gymnastic specific aerobic training should not be neglected, while a different aerobic share in WAG and MAG strengthens sex-specific conditioning. All in all, the specific metabolic share must secure adequate energy provision, while relative proportions of the two anaerobic pathways seem to depend on training and competition history.

Heart-Rate Acceleration Is Linearly Related to Anaerobic Exercise Performance.

To prescribe training loads to improve performance, one must know how an athlete is responding to loading. The maximal rate of heart-rate increase (rHRI) during the transition from rest to exercise is linearly related to changes in endurance exercise performance and can be used to infer how athletes are responding to changes in training load. Relationships between rHRI and anaerobic exercise performance have not been evaluated. The objective of this study was to evaluate relationships between rHRI and anaerobic exercise performance. Eighteen recreational strength and power athletes (13 male and 5 female) were tested on a cycle ergometer for rHRI, 6-second peak power output, anaerobic capacity (30-s average power), and blood lactate concentration prior to (PRE), and 1 (POST1) and 3 (POST3) hours after fatiguing high-intensity interval cycling. Compared with PRE, rHRI was slower at POST1 (effect size [ES] = -0.38, P = .045) but not POST3 (ES = -0.36, P = .11). PPO was not changed at POST1 (ES = -0.12, P = .19) but reduced at POST3 (ES = -0.52, P = .01). Anaerobic capacity was reduced at POST1 (ES = -1.24, P < .001) and POST3 (ES = -0.83, P < .001), and blood lactate concentration was increased at POST1 (ES = 1.73, P < .001) but not at POST3 (ES = 0.75, P = .11). rHRI was positively related to PPO (B = 0.19, P = .03) and anaerobic capacity (B = 0.14, P = .005) and inversely related to blood lactate concentration (B = -0.22, P = .04). rHRI is linearly related to acute changes in anaerobic exercise performance and may indicate how athletes are responding to training to guide the application of training loads.

Peak Blood Lactate Concentration and Its Arrival Time Following Different Track Running Events in Under-20 Male Track Athletes.

To determine (1) the time of arrival of peak blood lactate concentration ([BLa]peak) followed by various track events and (2) significant correlation, if any, between average velocity and [BLa]peak in these events. In 58 under-20 male track athletes, heart rate was recorded continuously and blood lactate concentration was determined at various intervals following 100-m (n = 9), 200-m (n = 8), 400-m (flat) (n = 9), 400-m hurdles (n = 8), 800-m (n = 9), 1500-m (n = 8), 3000-m steeplechase (n = 7), and 5000-m (n = 10) runs. The [BLa]peak, in mmol/L, was recorded highest following the 400-m run (18.27 [3.65]) followed by 400-m hurdles (16.25 [3.14]), 800-m (15.53 [3.25]), 1500-m (14.71 [3.00]), 200-m (14.42 [3.40]), 3000-m steeplechase (11.87 [1.48]), 100-m (11.05 [2.36]), and 5000-m runs (8.65 [1.60]). The average velocity of only the 400-m run was found to be significantly correlated (r = .877, p < 0.05) with [BLa]peak. The arrival time of [BLa]peak following 100-m, 200-m, 400-m, 400-m hurdles, 800-m, 1500-m, 3000-m steeplechase, and 5000-m runs was 4.44 (0.83), 4.13 (0.93), 4.22 (0.63), 3.75 (0.83), 3.34 (1.20), 2.06 (1.21), 1.71 (1.44), and 1.06 (1.04)minutes, respectively, of the recovery period. In under-20 runners, (1)[BLa]peak is highest after the 400-m run, (2)the time of appearance of [BLa]peak varies from one event to another but arrives later after sprint events than longer distances, and (3)the 400-m (flat) run is the only event wherein the performance is significantly correlated with the [BLa]peak.

The Effects of L-Citrulline on Blood-Lactate Removal Kinetics Following Maximal-Effort Exercise

The accumulation of lactate in muscle and blood during high-intensity exercise is negatively correlated with the duration exercise can be sustained. Removal of lactate is a key component of acute recovery between consecutive bouts of such exercise. Low-intensity exercise enhances recovery by accelerating lactate turnover in metabolically active tissues, largely mediated by blood flow to these tissues. Therefore, the purpose of this research was to clarify if L-citrulline, a nutritional supplement purported to promote vasodilation via enhanced nitric oxide availability, would augment the removal of blood lactate during active recovery (AR). L-citrulline ingestion will augment the rate of blood lactate concentration decrease during AR, reduce the oxygen-cost of submaximal exercise, and increase time-to-exhaustion and peak oxygen uptake (V̇O2peak) during a test of maximal aerobic power. Healthy university students (five males & five females) participated in this double-blind, randomized, placebo-controlled study. Participants exercised on a cycle ergometer at submaximal steady-state intensities followed by progressively increasing intensity to exhaustion, 10 min of AR, and then supramaximal intensity exercise to exhaustion. Oxygen uptake was measured throughout the trial and blood lactate was sampled repeatedly during AR. The protocol elicited very high peak blood lactate concentrations after exercise (11.3 + 1.3 mmol/L). L-citrulline supplementation did not significantly alter blood lactate kinetics during AR, the oxygen cost of exercise, V̇O2peak, or time-to-exhaustion. Despite a strong theoretical basis by which L-citrulline could augment lactate removal from the blood, L-citrulline supplementation showed no effect as an exercise-recovery supplement.

Effects of sprint distance and repetition number on energy system contributions in soccer players

Background/objectiveThis study aims to compare the effect of sprint distance and repetition number on performance, physiological responses, and energy systems contributions. MethodsEighteen male university league soccer players (age: 19.9 ± 1.6 years, height: 177.9 ± 4.7 cm, body mass: 72.4 ± 6.3 kg, percentage body fat: 8.9 ± 1.8, training experience: 7.4 ± 1.6 years) completed two different repeated sprint protocols: 20 × 20 m (20 × 20) and 10 × 40 m (10 × 40) with 15s and 30s rest intervals, respectively. Oxygen uptake (VO2) were measured during the rest, exercise, and recovery phases. Rest and peak blood lactate concentrations were determined. Using VO2 and lactate values, the energy system contributions were calculated using a mono-exponential model and mathematical calculations. Energy systems contributions and total energy expenditure (TEE) were calculated both for the entire protocol (overall) and for the sprints only. ResultsRatings of perceived exertion (RPE), peak and mean heart rate (HR) responses were significantly higher in the 20 × 20 whereas lactate response was higher in the 10 × 40. TEE was similar between the 10 × 40 (586.3 ± 60.8 kJ) and 20 × 20 (595.6 ± 57.5 kJ). For overall estimations, the 10 × 40 and 20 × 20 presented similar results of oxidative (47.5 ± 5.4 vs 45.7 ± 5.1 kJ min−1) and phosphagen (44.7 ± 5.4 vs (42.9 ± 4.8 kJ min−1) systems contributions whereas glycolytic contribution was higher in the 10 × 40 (15.5 ± 2.2 vs 12.8 ± 2.3 kJ min−1). For sprints only estimation, the phosphagen (257.6 ± 31.5 vs 225.2 ± 28.2 kJ min−1), glycolytic (89.4 ± 13.4 vs 67.3 ± 12.5 kJ min−1), and oxidative (76.9 ± 6.9 vs 72.0 ± 7.9 2 kJ min−1) systems contributions were higher in the 10 × 40. ConclusionsAlthough HR and RPE responses were higher in the 20 × 20, phosphagen (during sprints) and glycolytic (during both sprints and overall protocol) were higher in the 10 × 40 protocol. Therefore, the 10 × 40 protocol seems more reasonable for developing or evaluating the anaerobic systems.

Effects of an experimental taper period on male and female swimmers

This study investigated the possible influence of the gender on the responses of swimmers during a taper period (TP). Ten males (19±3 years and 73.5±7.8 kg) and ten females (17±2 years and 54.7±7.2 kg) swimmers were submitted to a 12-week training, followed by three weeks of the TP. Before and after the TP we evaluated the performance at 100 m freestyle, stroke parameters and lactacidemic responses; lactate minimum intensity (LMI) and stroke parameters associated with LMI and the propulsive force in tethered swimming. TP consisted of 14 sessions with mean volume 2253±1213 m/session at an intensity below than the LMI, 1730±327 m/session at an intensity near the LMI and 1530±1019 m/session at an intensity above the LMI. Significant effects of the genders were observed for LMI and stroke parameters (P<0.001 and η2>0.52 [large]) and propulsive force (P=0.001; η2=0.59 [large]). However, no significant effects of the TP were identified in the performance of the 100 m freestyle (P=0.66; η2=0.006 [small]), propulsive force (P>0.63; η2<0.006 [small]), aerobic parameters (LMI: P=0.32 and η2=0.03 [small]) and mechanical parameters (P>0.23; η2=0.01 [small]). Nonetheless, the peak blood lactate concentrations were improved after TP (P=0.014; η2=0.16 [large]), without significant interactions (P=0.38; η2=0.02 [small]), as well as the mechanical parameters during maximum 100 m freestyle (P<0.04 and η2>0.10 [medium]). Hence, men and women presenting significantly different values in the age group studied, the responses observed after the TP investigated were the same independent of gender.

Associations between the occurrence of the ACTN3 R577X, ACE I/D, BDKRB2 +9/-9 polymorphisms and anaerobic performance among a group of elite fencers

Introduction: This research aims to detect possible associations between the ACTN3 R577X, ACE I/D, BDKRB2 +9/-9 genetic polymorphisms, and selected anaerobic performance indicators among elite and sub-elite fencers. Methods: The sample of participants included a group of 20 fencers (males, age 25.5 ± 6.9 years; height 185.1 ± 5.8; weight 78.3 ± 9.8). We obtained genotype analysis for selected polymorphisms (ACTN3 R577X, ACE I/D, BDKRB2 +9/-9) through buccal swabs. 30-second Wingate test was used for the anaerobic performance where the following variables were monitored: the maximal anaerobic performance – Pmax [W], the anaerobic capacity – AnC [kJ], the total number of revolutions – TR [n], the peak blood lactate concentration – LApeak [mmol·l-1]. Results: Within ACTN3 R577X polymorphism, no differences were found in the observed variables between genotypes. However, ACE I/D heterozygotes reached higher Pmax, AnC, and LApeak values than homozygotes. Furthermore, BDKRB2 +9/-9 polymorphism homozygotes with -9 allele reached higher Pmax and AnC values than homozygotes with +9 allele. No statistical differences were found in all monitored variables between genotypes of monitored polymorphisms. Conclusions: The research findings might serve as another useful piece of knowledge related to the existing statements in the field of genetics, focusing on speed-strength performance problems. It should be highlighted that current studies are only the first steps in helping us better understand the associations between genetic factors and performance in sports.

Metabolic and Cardiorespiratory Responses of Semiprofessional Football Players in Repeated Ajax Shuttle Tests and Curved Sprint Tests, and Their Relationship with Football Match Play.

In this study, the Ajax Shuttle Test (AST) and the Curved Sprint Test (CST) were conducted on semiprofessional football players to evaluate (1) their test performance, (2) the extent of anaerobic glycolysis by measuring blood lactate, (3) performance decrement and onset of fatigue, and (4) the correlation between selected physiological variables and test performance. Thirty-two semiprofessional Polish football players participated in this study. Both AST and CST were conducted on an outdoor football ground and were conducted in two sets; each set had six repetitions. In the case of AST, the total duration for 6 repetitions of the exercise in Sets 1 and 2 were 90.63 ± 3.71 and 91.65 ± 4.24 s, respectively, whereas, in the case of CST, the respective values were 46.8 ± 0.56 and 47.2 ± 0.66 s. Peak blood lactate concentration [La] after Sets 1 and 2 of AST were 14.47 ± 3.77 and 15.00 ± 1.85 mmol/L, and in the case of CST, the values were 8.17 ± 1.32 and 9.78 ± 1.35 mmol/L, respectively. Performance decrement in AST was more than in CST, both after Set 1 (4.32 ± 1.43 and 3.31 ± 0.96 in AST and CST, respectively) and Set 2 (7.95 ± 3.24 and 3.71 ± 1.02 in AST and CST, respectively). Only in a few of the repetitions, pulmonary ventilation (VE) and oxygen uptake (VO2) were found to be significantly correlated with the performance of the volunteers in both AST and CST. Respiratory exchange ratio (RER) was significantly correlated with most of the repetitions of AST, but not with CST. The study concludes that (1) AST shows more dependence on the anaerobic glycolytic system than shorter repetitive sprints (as in CST), (2) there is more performance decrement and fatigue in AST than in CST, and (3) early decrease in performance and fatigue in the semiprofessional football players in AST and CST may be due to the insufficiency of their aerobic energy system.

Sodium bicarbonate improves sprint performance in endurance cycling

ObjectivesOral sodium bicarbonate intake (NaHCO3) may improve performance in short maximal exercise by inducing metabolic alkalosis. However, it remains unknown whether NaHCO3 also enhances all-out performance at the end of an endurance competition. Therefore, the present study investigated the effect of stacked NaHCO3 loading on sprint performance following a 3-h simulated cycling race. DesignDouble-blind randomized placebo-controlled cross-over study. MethodsEleven trained male cyclists (22.3 (18.3–25.3) year; 73.0 (61.5–88) kg; VO2max: 63.7 (57–72) mlkg−1min−1) ingested either 300mgkg−1 body weight NaHCO3 (BIC) or NaCl (PL). NaHCO3 or NaCl was supplemented prior to (150mgkg−1) and during (150mgkg−1) a 3-h simulated cycling race with a 90-s all-out sprint (90S) at the end. Capillary blood samples were collected for determination of blood pH, lactate and HCO3− concentrations. Analysis of variance (lactate, pH, HCO3−) and paired t-test (power) were applied to compare variables across condition (and time). ResultsNaHCO3 intake improved mean power during 90S by ∼3% (541±59W vs. 524±57W in PL, p=0.047, Cohen’s D=0.28, medium). Peak blood lactate concentration and heart rate at the end of 90S were higher (p<0.05) in BIC (16.2±4.1mmoll1, 184±7bpm) than in PL (12.4±4.2mmoll−1, 181±5bpm). NaHCO3 ingestion increased blood [HCO3−] (31.5±1.3 vs. 24.4±1.5mmoll−1 in PL, p<0.001) and blood pH (7.50±0.01 vs. 7.41±0.03 in PL, p<0.05) prior to 90S. ConclusionsNaHCO3 supplementation prior and during endurance exercise improves short all-out exercise performance at the end of the event. Therefore, sodium bicarbonate intake can be applied as a strategy to increase success rate in endurance competitions.

Markers Of Training Stress Associated With Functional Overreaching In Middle Distance Runners

PURPOSE: The present study aimed to identify markers of training stress that were related to the incidence of overreaching in response to overload training in middle distance runners. METHODS: Twenty-four middle distance runners (n=16 M, V̇O2peak: 73.3±4.3 mL·kg·min-1; n=8 F, V̇O2peak: 63.2±3.4 mL·kg·min-1) completed 3 wk of normal training, followed by 3 wk of high-volume training (HVTr; 10% increase in volume each successive week), and a 1-wk taper (TapTr; 55% exponential reduction in training volume from HVTr wk 3). Before, and immediately after each training phase, an incremental treadmill test was performed to measure time to exhaustion (TTE), peak heart rate (HRpeak), HR recovery, peak blood lactate concentration ([La]bpeak) and V̇O2peak. In addition, resting metabolic rate (RMR), body composition, energy intake and resting blood biomarkers of training stress were measured. Runners who had a decreased TTE (>CV) after HVTr were classified as being functionally overreached (FOR), others as acutely fatigued (AF; no decrease performance). Differences between AF and FOR were analysed using mixed-model ANOVAs with pairwise comparisons. RESULTS: Following HVTr, there were significant between group differences in the responses to exhaustive running, whereby FOR (n=12) had a decrease in TTE (-49 ± 14 s), HRpeak (-4 ± 3 BPM; p = 0.02), [La]bpeak (-4.30 ± 1.80 mmol·L-1; p = 0.01) and V̇O2peak (-2.33 ± 2.0 mL·kg·min-1,) and a faster HR recovery (-5 ± 4 BPM; p = 0.03) compared to AF (n=12). There were no between group differences in these variables during submaximal running, nor were there changes in absolute or relative RMR, while only the FOR group increased energy intake during the HVTr. There was no statistically significant change in body composition in either group throughout the study nor were there changes in resting blood biomarkers that reflected inflammation (IL-6, GDF-15 and CRP), metabolism (thyroid hormones), catabolism and anabolism (DHEA, urea, total protein, testosterone, cortisol and GH) or iron regulation (iron, ferritin, and UIBC). CONCLUSIONS: Middle distance runners who were classified as FOR following an overload training period did not have alterations in RMR, resting blood biomarkers or submaximal exercise responses compared to runners who did not have impaired performance.