Effects of moderate-intensity intermittent hypoxic training on health outcomes of patients recovered from COVID-19: the AEROBICOVID study protocol for a randomized controlled trial

Background

Recent studies point to a lower number and reduced severity of cases in higher altitude cities with decreased oxygen concentration. Specific literature has shown several benefits of physical training, so, in this sense, physical training with hypoxic stimulus appears as an alternative that supports the conventional treatments of the COVID-19 patient’s recovery. Thus, this study’s primary aim is to analyze the effects of moderate-intensity intermittent hypoxic training on health outcomes in COVID-19 recovered patients.

Methods

A clinical trial controlled double-blind study was designed. Participants (30–69 years old) will be recruited among those with moderate to severe COVID-19 symptoms, approximately 30 days after recovery. They will be included in groups according to the training (T) and recovery (R) association with hypoxia (H) or normoxia (N): (a) T_H:R_H, (b) T_N:R_H, (c) T_N:R_N, and last (d) the control group. The 8-week exercise bike intervention will be carried out with a gradual load increase according to the established periods, three times a week in sets of 5 min, 90 to 100% of the anaerobic threshold (AT), and a 2.5-min break. Blood will be collected for genotyping. First, after 4 weeks (partial), after 8 weeks, and later, 4 weeks after the end of the physical training intervention, participants will perform assessments. The primary outcome is the maximum oxygen consumption (VO₂peak). The secondary outcomes include lung function, inflammatory mediators, hematological, autonomic parameters, AT, body composition analysis, quality of life, mental health, anthropometric measurements, and physical fitness. The statistical analysis will be executed using the linear regression model with mixed effects at a 5% significance level.

Discussion

This study is designed to provide evidence to support the clinical benefits of moderate-intensity intermittent hypoxic training as a part of the treatment of patients recovered from COVID-19. It may also provide evidence on the efficacy and safety of intermittent hypoxic training in different health conditions. Lastly, this study presents an innovative strategy enabling up to 16 participants in the same training session.

Trial registration

ClinicalTrials.gov RBR-5d7hkv. Registered after the start of inclusion on 3 November 2020 with the Brazilian Clinical Trials Registry

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05414-2.

Effects of an experimental taper period on male and female swimmers

BACKGROUND

This study investigated the possible influence of the gender on the responses of swimmers during a taper period (TP).

METHODS

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 2,253 ± 1,213 m•session-1 at an intensity below than the LMI, 1,730 ± 327 m•session-1 at an intensity near the LMI and 1,530 ± 1,019 m•session-1 at an intensity above the LMI.

RESULTS

Significant effects of the genders were observed for LMI and stroke parameters (p-value < 0.001 and η2 > 0.52 [large]) and propulsive force (p-value = 0.001; η2 = 0.59 [large]). However, no significant effects of the TP were identified in the performance of the 100 m freestyle (p-value = 0.66; η2 = 0.006 [small]), propulsive force (p-value > 0.63; η2 < 0.006 [small]), aerobic parameters (LMI: p-value = 0.32 and η2 = 0.03 [small]) and mechanical parameters (p-value > 0.23; η2 = 0.01 [small]). Nonetheless, the peak blood lactate concentrations were improved after TP (p-value = 0.014; η2 = 0.16 [large]), without significant interactions (p-value = 0.38; η2 = 0.02 [small]), as well as the mechanical parameters during maximum 100 m freestyle (p-value < 0.04 and η2 > 0.10 [medium]).

CONCLUSIONS

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.

Predicting the individual lactate minimum speed by T10 and T30 in swimming

BACKGROUND

This study investigated the relationship between the lactate minimum (LACmin) and the 10- (T10) and 30-min (T30) continuous tests in swimmers.

METHODS

Twelve swimmers (78.1 ± 3.1% of world record) performed the LACmin (hyperlactatemia: 2 x 50 m all-out 8-min apart, incremental part: n x 300 m 30-s apart), T30 and T10 using the front-crawl stroke. Blood samples were collected after each stage of LACmin for lactate analysis. Swimmers were oriented to swim as fast and as constant as possible in T10 and T30.

RESULTS

Speeds in T10 (1.28 ± 0.10 m/s) and T30 (1.21 ± 0.09 m/s) were different from LACmin (1.24 ± 0.09 m/s). T10 and T30 speeds presented a nearly perfect relationship with LACmin and acceptable prediction errors (T10: r = 0.938, p < 0.001, 0.033 m/s; T30: r = 0.927, p < 0.001, 0.036 m/s, respectively).

CONCLUSIONS

T10 and T30 can be used as indirect tests for evaluating LACmin in swimming.

Physiology Responses and Players' Stay on the Court During a Futsal Match: A Case Study With Professional Players

Physiological responses in futsal have not been studied together with temporal information about the players’ stay on the court. The aim of this study was to compare heart rate (HR) and blood lactate concentration ([La⁻]) responses between 1-H and 2-H considering the time of permanency of the players on the court at each substitution in a futsal match. HR was recorded during entire match and [La⁻] was analyzed after each substitution of seven players. %HR_mean (89.61 ± 2.31 vs. 88.03 ± 4.98 %HR_max) and [La⁻] mean (8.46 ± 3.01 vs. 8.17 ± 2.91 mmol·L⁻¹) did not differ between 1-H and 2-H (ES, trivial-small). Time in intensity zones of 50–100 %HR_max differed only in 60–70 %HR_max (ES, moderate). HR coefficient of variation throughout the match was low (7%) and among the four outfield players on the court (quartets, 5%). Substitutions (2 player’s participation in each half), time of permanence on the court (7.15 ± 2.39 vs. 9.49 ± 3.80 min), ratio between time in- and out-ratio on the court (In:Outcourt = 1:1.30 ± 1:0.48 vs. 1:1.05 ± 1:0.55 min) also were similar between 1-H and 2-H (ES, moderate and small, respectively). Balancing the number of substitutions, and the In:Outcourt ratio of players in both halves of the match, playing lower time at 1-H, ~8 min for each participation in the match, made it possible to maintain intensity of the match in 2-H similar to the 1H. These results are a good guidance to coaches and for application in future studies.

Beta-alanine fails to improve on 5000 m running time despite increasing PAT1 expression in long-distance runners

BACKGROUND

Beta-alanine has become a dietary supplement widely used by athletes due to its ergogenic effect. However, there is still no consensus on the performance benefit of beta-alanine on exercise lasting longer than ten minutes. The present study aimed to evaluate the effect of beta-alanine supplementation on running performance and the expression of TauT and PAT1.

METHODS

This double-blind, randomized study enrolled 16 long-distance runners (37±8 years) who were randomly allocated to two groups: placebo (PLA) and beta-alanine (BA) (4.8 g/day 1) for four weeks. Maximal oxygen consumption, anthropometry, body composition, and food intake were determined. Before and after the intervention, the athletes undertook a 5000 m running time trial. Venous blood (TauT and PAT1 expressions) and ear lobe capillary blood (lactate) collected before and after exercise. Between tests, we monitored the training variables.

RESULTS

The results were analyzed by t-tests and an ANOVA of repeated measures, with Sidak's post hoc (P<0.05). PLA exhibited lower body fat than BA (8.7±2.2 vs. 11.5±2.8%, P=0.04). After supplementation, there was an increase in PAT1 expression in BA when compared to PLA (1.17±0.47 vs. 0.77±0.18, P=0.04). No significant differences were shown for the 5000 m running time in PLA (PRE: 1128±72; POST: 1123±72s) and BA (PRE: 1107±95; POST: 1093±86s).

CONCLUSIONS

Although beta-alanine supplementation increased PAT1 expression, there was no statistically significant improvement in 5000 m running performance. However, individual responses should be considered as the BA showed a higher delta than the PLA.

Proposal of a Conditioning Activity Model on Sprint Swimming Performance

This study aimed to propose a conditioning activity (CA) model to stimulate improvement on neuromuscular responses, mechanical parameters and for the 50-m freestyle swimming. Thirteen male swimmers (19 ± 3 years and performances of 77% in relation to World Championship records) performed four CA protocols followed by a maximum performance in the 50-m freestyle. In the first protocol (P1) swimmers performed a standard warm-up (∼15 min); in the second protocol (P2) lunges (3 × 85% of the one-repetition maximum); in the third (P3) pull-ups (3 maximum repetitions) and box jumps 40 cm high and 60 cm deep (1 × 5 with 10% of the corporal weight); and in the fourth protocol (P4) a combination of exercises from the second and third protocols. CA protocols had no effect on the standard warm-up. However, P2 performance (27.01 ± 1.25 s) was similar to P1 (27.01 ± 1.18 s) and presented higher positive effects in mechanical parameters for the swim start performance in comparison to other protocols, contributing to improvements in the 50-m freestyle. In addition, turnaround time also had a negative effect, mainly in P3 (3.12 ± 0.28 s), signaling the improvement of this variable in all protocols (P1: 3.30 ± 0.38 s; P2: 3.17 ± 0.30 s; P4: 3.17 ± 0.34 s). P2 (after: 80 ± 11%; before: 82.7 ± 9.9%) and P3 (after: 82.7 ± 9.9%; before: 85.1 ± 9.7%) presented a possible positive effect on the percentage of voluntary activation in relation to P1 (after: 79.3 ± 10.7%; before: 76.3 ± 12%). In conclusion, the proposed conditioning activity protocols were not efficient for performance improvement in the 50-m freestyle compared to the standard model and seem to specifically influence each phase of the event.

Backward extrapolation technique: analysis of different criteria after supramaximal exercise in cycling

BACKGROUND

Backward extrapolation technique (BE) was used to estimate V̇O<inf>2</inf> from postexercise measuring, eliminating oronasal mask (OM) during the efforts. Despite its advantage, literature presents discrepancy in applied methods. Thus, the first aim of this study was to compare different mathematical criteria to estimate values of V̇O<inf>2</inf> during a supramaximal effort (V̇O<inf>2PEAK</inf>), while the second aim was to verify the effects of OM on cycling performance.

METHODS

Twenty-four male cyclists (35±6 years, 81.3±8.9 kg, 180±6 cm) performed three days of tests, with at least 24 h of interval between each test. Firstly, a graded exercise test was applied to determine V̇O<inf>2max</inf> and your correspondent intensity (MAP). The second and the third day were destined to supramaximal efforts at 120% of MAP, performed with (Supra<inf>mask</inf>) and without (Supra<inf>be</inf>) oronasal mask (OM) in a randomized order. After Supra<inf>be</inf>, OM was coupled, and BE was applied. Sixty-six values of V̇O<inf>2</inf> were obtained based on a linear regression fitting.

RESULTS

V̇O<inf>2peak</inf> can be estimated using different curve lengths. However, only curves between 20 and 60 s with extrapolation to 3 s or lesser shows at least one consistent criterion. The 60 s curve extrapoled to -3 s was the most accurate criteria (P=0.723; ES=-0.055; r=0.824; Bias=-0.36 and LoA=7.72 mL.kg.min^-1). Performance was not impaired with OM and was similar in both condition (P=0.84, ES=0.04).

CONCLUSIONS

We conclude that it was possible to accurately estimate V̇O<inf>2</inf> values of a supramaximal effort without any respiratory apparatus with a time-efficient analysis. Therefore, we recommended the use of a 60 seconds V̇O<inf>2</inf> curve analysis with a negative extrapolation for 3 seconds.

A New Approach to Evaluate Neuromuscular Fatigue of Extensor Elbow Muscles

Neuromuscular fatigue evaluation is widely performed on different muscles through the conventional protocol using maximum voluntary contraction (MVC) with electrical stimuli in the analyzed muscle. In an attempt to use this protocol on elbow extensor musculature, previous studies and pilot studies showed co-contraction effects from antagonist musculature during muscular stimulations. The aim of this study was to propose a new neuromuscular fatigue protocol evaluation on elbow extensor musculature. Twenty participants preformed exercises to induce central (CenFat) and peripheral fatigue (PerFat). Neuromuscular fatigue was evaluated on knee extensor muscles by a conventional protocol that provides Twitch Superimposed (TS_K) and Twitch Potentiated (TP_K), central and peripheral parameters respectively. For elbow extensor muscles, the protocol used sustained submaximal contraction at 10, 20, 30, 40, and 50% of MVC. The neuromuscular fatigue in upper limbs was identified by Twitch Potentiated (TP_E) and multiple Twitch Superimposed (TS_E) parameters. Using the relationship between MVC (%) and evoked force, the proposed protocol used several TS_E to provide slope, y-intercept and R ². It is proposed that slope, R ², and y-intercept change may indicate peripheral fatigue and the identified relationship between y-intercept and R ² may indicate central fatigue or both peripheral and central fatigue. The results were compared using the non-parametric analyzes of Friedmann and Wilcoxon and their possible correlations were verified by the Spearmann test (significance level set at p < 0.05). After PerFat a decrease in TP_E (57.1%, p < 0.001) was found but not in any TS_E, indicating only peripheral fatigue in upper limbs. After CenFat a decrease in TP_E (21.4%, p: 0.008) and TP_K (20.9%, p < 0.001) were found but not in TS_K, indicating peripheral fatigue in upper and lower limbs but not central fatigue. A non-significant increase of 15.3% after CenFat and a statistical reduction (80.1%, p: 0.001) after PerFat were found by slope. Despite R ² showing differences after both exercises (p < 0.05), it showed a recovery behavior after CenFat (p: 0.016). Although PerFat provided only peripheral fatigue, CenFat did not provide central fatigue. Considering the procedural limitations of CenFat, parameters resulting from the proposed protocol are sensitive to neuromuscular alteration, however, further studies are required.

Correction to: Beta alanine supplementation effects on metabolic contribution and swimming performance

An amendment to this paper has been published and can be accessed via the original article.

Determination of Maximum Accumulated Oxygen Deficit Using Backward Extrapolation

This study aimed to compare the Maximum Accumulated Oxygen Deficit determined by the conventional method (MAOD_C) with that determined by the backward extrapolation technique (MAOD_EXTR) in runners. Fourteen runners underwent a maximal incremental test for determination of iVO_2MAX, ten submaximal efforts (50-95% of iVO_2MAX for 7 min). During the submaximal efforts oxygen consumption (VO₂) values were obtained conventionally and through the backward extrapolation technique (~ 3 s after the end of each effort). A supramaximal effort (110% of iVO_2MAX) (tLim_C) and five supramaximal bouts (tLim_EXTR) were performed. MAOD_C and MAOD_EXTR were determined from the difference between the VO₂ accumulated during tLim_C and tLim_EXTR and the predicted values. The tLim_C was lower than tLim_EXTR (164.06±36.32 s, 200.23±63.78 s, p<0.05). No significant differences were found between absolute and relative MAOD_C and MAOD_EXTR values, however, low intraclass correlations (0.26 and 0.24), high typical errors (2.03 L and 24 mL∙kg^-1) were observed, and coefficients of variation (46 and 48%), respectively. The graphical analysis of the differences showed agreement and correlation between the methods (r=0.86 and 0.85). Thus, it can be concluded that the MAOD_EXTR is not a valid method for estimating the anaerobic capacity of runners, moreover, unreliable.

Beta alanine supplementation effects on metabolic contribution and swimming performance

BACKGROUND

Investigations of β-alanine supplementation shows effects on metabolic (aerobic and anaerobic) participation and performance on swimming by a possible blood acidosis buffering. Considering this background, the objective of the present study was to analyze the effects of β-alanine supplementation on metabolic contribution and performance during 400-m swim.

METHODS

Thirteen competitive swimmers underwent a 6-week, double-blind placebo-controlled study, ingesting 4.8 g.day- 1 of β-alanine or placebo. Before and after the supplementation period, the total anaerobic contribution (TAn) and 30-s all-out tethered swimming effort (30TS) were assessed. Anaerobic alactic (AnAl) and lactic energy (AnLa) was assumed as the fast component of excess post-exercise oxygen consumption and net blood lactate accumulation during exercise (∆[La-]), respectively. Aerobic contribution (Aer) was determined by the difference between total energy demand and TAn. In addition to conventional statistical analysis (Repeated measures ANOVA; p > 0.05), a Bayesian repeated measures ANOVA was used to evidence the effect probability (BFincl).

RESULTS

No differences and effects were found between groups, indicating no supplementation effects. Repeated measures ANOVA, with confirmation of effect, was indicate reduce in ∆Lactate (p: 0.001; BFincl: 25.02); absolute AnLa (p: 0.002; BFincl: 12.61), fatigue index (p > 0.001; BFincl: 63.25) and total anaerobic participation (p: 0.008; BFincl: 4.89).

CONCLUSIONS

Thus, the results demonstrated that all changes presented were evidenced as a result of exposure to the training period and β-alanine supplementation doesn't affect metabolic contribution and performance during 400-m freestyle.

The 400-m Front Crawl Test: Energetic and 3D Kinematical Analyses

The aim of the study was to verify the relative contributions of energetic and kinematic parameters to the performance in 400-m front crawl test. Fourteen middle-distance swimmers participated in the study. Oxygen consumption was measured directly and blood samples were collected to assay lactate concentration. Both oxygen consumption and lactate concentration were used to calculate the: (i) overall energy expenditure, (ii) anaerobic (alactic and lactic) and (iii) aerobic contributions. The mean centre of mass speed and intracycle velocity variation were determined through three-dimensional kinematic analysis. Mean completion time was 315.64±26.91s. Energetic contributions were as follows: 6.1±0.28% from alactic anaerobic metabolism, 5.9±0.63% from anaerobic lactic and 87.8±0.88% from aerobic. Mean intracycle velocity variation was 0.14±0.03. The results indicated that performance of 400-m test relies predominantly on aerobic power. Parameters such as lactate, mean speed, anaerobic lactic and alactic (kW) correlated with performance of 400-m test (p <0.05). Multiple linear regressions indicated that mean centre of mass speed and anaerobic alactic (kW) determined the 400-m test performance (R²=0.92). Even though the T400 is characterized by aerobic metabolism, the anaerobic alactic component cannot be negligible at this competition level.

Physical training, UCP1 expression, mitochondrial density, and coupling in adipose tissue from women with obesity

BACKGROUND

Exercise training may improve energy expenditure, thermogenesis, and oxidative capacities. Therefore, we hypothesized that physical training enhances white adipose tissue mitochondrial oxidative capacity from obese women.

OBJECTIVE

To evaluate mitochondrial respiratory capacity, mitochondrial content, and UCP1 gene expression in white adipose tissue from women with obesity before and after the physical training program.

METHODS

Women (n = 14, BMI 33 ± 3 kg/m² , 35 ± 6 years, mean ± SD) were submitted to strength and aerobic exercises (75%-90% maximum heart rate and multiple repetitions), 3 times/week during 8 weeks. All evaluated subjects were paired, before and after training for resting metabolic rate (RMR), substrate oxidation (lipid and carbohydrate) by indirect calorimeter, deuterium oxide body composition, and aerobic maximum velocity (V_max ) test. At the beginning and at the ending of the protocol, abdominal subcutaneous adipose tissue was collected to measure the mitochondrial respiration by high-resolution respirometry, mitochondrial content by citrate synthase (CS) activity, and UCP1 gene expression by RT-qPCR.

RESULTS

Combined physical training increased RMR, lipid oxidation, and V_max but did not change body weight/composition. In WAT, exercise increased CS activity, decreased mitochondrial uncoupled respiration and mRNA of UCP1. RMR was positively correlated with fat-free mass.

CONCLUSION

Physical training promotes an increase in mitochondrial content without changing tissue respiratory capacity, a reduction in mitochondrial uncoupling degree and UCP1 mRNA expression in WAT. Finally, it improved the resting metabolic rate, lipid oxidation and physical performance, independent of the body changing free, or fat mass in obese women.

Fed and fasted states on heart rate variability, hemodynamic heart rate and blood pressure in adults submitted to moderate aerobic exercise

Background

Heart rate variability (HRV) has proven to be a powerful non-invasive tool to investigate cardiac autonomic control and, seems to be influenced by nutritional status and exercise practice. However, the acute effects of fed or fasting states on HRV and blood pressure (BP) during low-to-moderate intensity aerobic exercise are currently unknown. Therefore, we investigated the baseline values and behavior of HRV, BP, and heart rate (HR) before and after low-to-moderate intensity aerobic exercise in fed and fasted states in healthy adults.

Methods

12 healthy individuals with mean age (SD) 59.0 (9.1) years performed two tests on a treadmill at 80% of the mean velocity of the 6-min walking test separated by 48 h: 12 h fasted (FST) or 1 h fed (FED). HRV, BP and HR were analyzed at rest, posttest, and at the third, fifth, and seventh minutes of recovery.

Results

HRV and HR presented no significant alterations between nutritional conditions. HR at baseline was not different between nutritional conditions. Diastolic blood pressure was increased during the fasted baseline state.

Conclusions

The results of the current study provide that 12 h overnight fasting does not seem to be enough to affect significant changes in the autonomic modulation in healthy adults submitted to low-to-moderate intensity aerobic exercise.

Relationships Between Aerobic and Anaerobic Parameters With Game Technical Performance in Elite Goalball Athletes

Our aims were to compare physiological parameters from the laboratory environment (LaB) and simulated goalball games (GaM), test relationships between physiological parameters in the laboratory and game technical performance (GTP), and examine the associations between physiological and technical responses during games. Seven elite athletes from the Brazilian National Team performed in LaB environment; (i) an incremental test to determine peak oxygen consumption (O_2PEAK), its corresponding speed, and peak blood lactate concentration and (ii) submaximal and supramaximal efforts to estimate maximal anaerobic contribution (AnC). In GaM condition, simulated games were also performed to determine physiological responses throughout the game, and to analyze the GTP (number of throws, defenses, recovery, and density of actions). No correlations (unclear) were found between laboratory and games analyses for O_2PEAK [47.3 (17.2) vs. 25.8 (18.2) mL⋅Kg^-1⋅min^-1], peak blood lactate concentrations [10.2 (5.4) vs. 2.0 (0.7) mM], and total AnC [21.0 (14.0) vs. 4.8 (6.1) mL Kg^-1]. O_2PEAK in the laboratory condition presented very likely correlations with throw and recovery frequency in games (r = -0.87 and confidence interval [CI] = 0.41; r = -0.90 and CI = 0.35; respectively). Oxygen consumption remained above baseline while blood lactate concentration remained unchanged during the games. The very likely correlation between anaerobic alactic contribution and action density (r = 0.95 and CI = 0.25) highlights the importance of the alactic metabolism. In general, our study demonstrates that goalball can be characterized as a high-intensity intermittent effort, where athlete performance is based on aerobic metabolism predominance while determinant actions are supplied by the anaerobic alactic metabolism. Specifically, higher values of LaB vs. GaM highlighted the need for standardization of specific protocols for goalball evaluation, mainly for the reproduction of ecologically valid values. In addition, O_2PEAK correlated with recovery frequency in the LaB condition, demonstrating that passive or low-intensity recovery between actions is fundamental to maintain performance.

Effects of 4 weeks of β-alanine supplementation on aerobic fitness in water polo players

The purpose of the present study was to investigate the ergogenic effects of 4 weeks of β-alanine supplementation on peak oxygen uptake (V˙O2peak) and force associated with V˙O2peak (FV˙O2peak) during a tethered swimming graded exercise test, and a three-minute all-out effort (3min_ALL-OUT) in water polo players. Twenty-two male national competitive level water polo players were randomly assigned to receive either 4 weeks of β-alanine (n = 11) or a placebo (n = 11) (i.e., 4.8 g·day^-1 for 10 days, then6.4 g·day^-1 for 18 days, resulting in 163.2 g over 28 days). The participants performed the TS_GET and 3min_ALL-OUT before and after the supplementation period. There were no significant interaction effects between-groups for any variable, however, the magnitude-based inferences analyses showed a possibly beneficial effect (74%) of β-alanine supplementation on FV˙O2peak compared to placebo treatment (Δ% [post–pre] for Placebo group = -5.2%; Δ% [post–pre] for β-alanine group = +0.7%). Only the β-alanine group presented a significant reduction in V˙O2peak expressed in absolute values (PRE = 3.3±0.6L·min^-1; POST = 3.0±0.4L·min^-1; p = .021). Similarly, only the β-alanine group presented a significant increase in critical force (PRE = 51.2±10.4N; POST = 56.5±13.1N; p = .044) and a reduction in the curvature constant parameter (W'; PRE = 2998.0±1103.7N·s; POST = 2224.6±1058.9N·s; p = .049). Thus, we can conclude that 4 weeks of β-alanine supplementation presented mixed results in water polo players, indicating that this nutritional strategy may not be effective in improving parameters of the TS_GET and 3min_{ALL-OUT .}

Dynamics of Recovery of Physiological Parameters After a Small-Sided Game in Women Soccer Players

Purpose: Training methods based on small-sided game (SSG) seem to promote physiological and tactical benefits for soccer players as they present characteristics more specific to the game. Thus, the main objective of the present study was to analyze the hormonal, biochemical, and autonomic parameters in an acute manner and the recovery dynamics (up to 72 h after) in a SSG. Methods: Thirteen professional female soccer players participated in the study (18.8 ± 0.8 years, body mass 59.4 ± 6.2 kg, and height 1.68 ± 0.05 m). During and after the SSG session (4 min × 4 min separated by 3 min of passive interval and 120 m² coverage per player), autonomic modulation was analyzed in the time and frequency domains using heart rate variability, and blood samples (5 ml) were collected before (0 h) and after (10 min and 24, 48, 72 h) the SSG for biochemical and hormonal analysis. Results: The SSG induced an increase effect for LF (low frequency) (92,52%; Very likely increase) and a decrease effect for HF (high frequency) values (-65,72%; Very likely decrease), after 10 min of recovery. The LF/HF increase after 10 min of recovery (386,21%; Very likely increase). The RMSSD (square root of the mean squared differences of the successive N-N intervals) and pNN50 (measure of the number of adjacent NN intervals which differ by more than 50 ms) values presented a decrease effect 10 min after SSG (61,38%; Very likely decrease and-90%; Very likely decrease). The CK (creatine kinase) values presented no changes 10 min after SSG. The LDH (lactate dehydrogenase) values presented an increase effect 10 min after the SSG (19,22%; Likely increase). Both testosterone and cortisol concentrations presented the same behavior after SSG, where no alterations were observed with after 10 min (<0,37%; Most likely trivial). Conclusion: The SSG promoted significant cardiovascular stress that was restored within the first 24 h of recovery. Parasympathetic parameters continued to increase while sympathetic parameters declined significantly during the 72 h of recovery. In addition, the reduced game did not alter biochemical or hormonal responses during the 72 h.

Table tennis playing styles require specific energy systems demands

The aim of the present study was to investigate the differences in energy system contributions and temporal variables between offensive and all-round playing styles. Fifteen male table tennis players (Offensive players: N = 7; All-round players: N = 8) participated in the study. Matches were monitored by a portable gas analyzer and the blood lactate responses was also measured. The contributions of the oxidative (WOXID), phosphagen (WPCr), and glycolytic (W[La]) energy systems were assumed as the oxygen consumption measured during the matches above of baseline value, the fast component of excess post-exercise oxygen consumption (EPOCFAST) measured after the matches, and the net of blood lactate concentration (Δ[La]), respectively. Energy systems contributions were not significantly different between the offensive and all-round playing styles (WOXID: 96.1±2.0 and 97.0±0.6%, P = 0.86; WPCr: 2.7±1.7 and 2.0±0.6%, P = 0.13; W[La]: 1.2±0.5 and 1.0±0.7%, P = 0.95; respectively), however, magnitude-based analysis of WPCr presented Likely higher contribution for offensive compared to all-round players. Regarding temporal variables, only rate of shots presented higher values for offensive when compared to all-round players (P = 0.03), while the magnitude-based analysis presented Very likely lower, Likely lower and Likely higher outcomes of rate of shots, WPCr and maximal oxygen consumption, respectively, for all-round players. Strong negative correlation was verified for offensive players between number of shots and WPCr (r = -0.86, P = 0.01), while all-round players showed strong correlations between rally duration, WOXID (r = 0.76, P = 0.03) and maximal oxygen consumption (r = 0.81, P = 0.03). Therefore, despite no differences in energy system contributions for offensive and all-round players, different playing styles seems to requires specific energy systems demands.