Monocarboxylate transporters (MCTs) in skeletal muscle and hypothalamus of less or more physically active mice exposed to aerobic training.

AIMS: The synthesis of monocarboxylate transporters (MCTs) can be stimulated by aerobic training, but few is known about this effect associated or not with non-voluntary daily activities. We examined the effect of eight weeks of aerobic training in MCTs on the skeletal muscle and hypothalamus of less or more physically active mice, which can be achieved by keeping them in two different housing models, a small cage (SC) and a large cage (LC). MAIN METHODS: Forty male C57BL/6J mice were divided into four groups. In each housing condition, mice were divided into untrained (N) and trained (T). For 8 weeks, the trained animals ran on a treadmill with an intensity equivalent to 80 % of the individual critical velocity (CV), considered aerobic capacity, 40 min/day, 5 times/week. Protein expression of MCTs was determined with fluorescence Western Blot. KEY FINDINGS: T groups had higher hypothalamic MCT2 than N groups (ANOVA, P = 0.032). Significant correlations were detected between hypothalamic MCT2 and CV. There was a difference between the SC and LC groups in relation to MCT4 in the hypothalamus (LC > SC, P = 0.044). Trained mice housed in LC (but not SC-T) exhibited a reduction in MCT4 muscle (P < 0.001). SIGNIFICANCE: Our findings indicate that aerobically trained mice increased the expression of MCT2 protein in the hypothalamus, which has been related to the uptake of lactate in neurons. Changes in energy metabolism in physically active mice (kept in LC) may be related to upregulation of hypothalamic MCT4, probably participating in the regulation of satiety.

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.

Energy Systems Contribution in the Running-based Anaerobic Sprint Test.

The aims of the present study were to verify the contributions of the energy systems during repeated sprints with a short recovery time and the associations of the time- and power-performance of repeated sprints with energetic contributions and aerobic and anaerobic variables. 13 healthy men performed the running-based anaerobic sprint test (RAST) followed by an incremental protocol for lactate minimum intensity determination. During the RAST, the net energy system was estimated using the oxygen consumption and the blood lactate responses. The relative contributions of oxidative phosphorylation, glycolytic, and phosphagen pathways were 38, 34, and 28%, respectively. The contribution of the oxidative pathway increased significantly during RAST especially from the third sprint, at the same time that power- and time-performances decreases significantly. The phosphagen pathway was associated with power-performance (peak power=432±107 W, r=0.65; mean power=325±80 W, r=0.65; minimum power=241±77 W, r=0.57; force impulse=1 846±478 N·s, r=0.74; p<0.05). The time-performance (total time=37.9±2.5 s; best time=5.7±0.4 s; mean time=6.3±0.4 s; worst time=7.0±0.6 s) was significantly correlated with the oxidative phosphorylation pathway (0.57+0.65; p<0.05) and glycolytic pathway (0.57+<+r>0.58; p<0.05). The oxidative pathway appears to play an important role in better recovery between sprints, and the continued use of the glycolytic metabolic pathway seems to decrease sprint performances. Finally, the phosphagen pathway was linked to power production/maintenance.

Serum IGF-I, IGFBP-3 and ALS concentrations and physical performance in young swimmers during a training season.

INTRODUCTION: The GH/IGF-I axis is a system of growth mediators, receptors, and binding proteins that regulate somatic and tissue growth; and it has been shown that exercise programs are related to the anabolic function of this axis. OBJECTIVE: The aim of this study was to analyse the changes of serum IGF-I concentration and that of its binding proteins IGFBP-3 and ALS in adolescent swimmers at different stages of a training season, and compare them with physical performance parameters and body composition of the athletes. MATERIAL AND METHODS: Nine male athletes, aged 16 to 19years and who trained regularly throughout the season, were included in this study. Serum IGF-I, IGFBP-3, and ALS concentrations were recorded before and after (pre×post) standardized training sessions during the different stages of a training season (extensive×intensive×tapering). Endurance in freestyle, anaerobic fitness in tied swimming (Peak Force and Average Force), body mass, fat percentage, and lean body mass were also analysed at the different stages of training in order to compare the changes of the IGF-I/IGFBP/ALS system with the physical performance and body composition of the athletes. Variations in the IGF-I/IGFBP-3-ALS system before and after a standardized training session, and at the different stages of training were analysed by the Wilcoxon and Friedman non-parametric tests, respectively. Significance was considered at 5%. RESULTS: The results from this study demonstrate that IGF-I is sensitive to the acute and chronic effects of training, exhibiting biphasic behaviour throughout the season. The catabolic phase was characterized by a reduction in serum IGF-I concentrations during the intensive stage (∆IGF-I: - 43.33±47.32ng/ml; P<0.05) while the anabolic phase was marked by similar basal concentrations at the different stages of training and an increase in post-training serum IGF-I concentrations during the tapering stage (320±40; 298±36 and 359±94ng/ml; P<0.05). IGFBP-3 was only sensitive to the chronic effects of training, with a reduction in post-training serum concentrations during the intensive stage and an increase during the tapering stage (4.7±0.7, 4.6±0.4 and 5.0±0.7mg/l; P<0.05). No significant difference (P>0.05) was observed in pre- or post-training IGFBP-3 concentrations (∆IGFBP-3) at the different stages. ALS concentrations remained unchanged throughout the season, demonstrating that in adolescent athletes they are unaffected by the acute or chronic effects of swimming. Peak Force (25.0±6.3, 24.2±5.7 and 28.5±6.5N; P<0.05) and Average Force (10.3±3.6, 8.8±1.8 and 14.7±1.8N; P<0.05) followed IGF-I and IGFBP-3 variations, with a decrease during the intensive stage and a significant (P<0.05) increase during the tapering stage. The body composition and cardiorespiratory condition of the swimmers did not vary significantly throughout the season, exhibiting behaviour independent of IGF-I or IGFBP-3. CONCLUSION: Serum IGF-I and IGFPB-3 concentrations have proven to be sensitive markers of training status and, thus, may be used as guides for coaches and athletes in the challenging task of modulating training intensity in young athletes.

The Hoff circuit test is more specific than an incremental treadmill test to assess endurance with the ball in youth soccer players.

The assessment of aerobic endurance is important for training prescription in soccer, and is usually measured by straight running without the ball on a track or treadmill. Due to the ball control and technical demands during a specific soccer test, the running speeds are likely to be lower compared to a continuous incremental test. The aim of the present study was to compare the heart rate (HR), rating of perceived exertion (RPE) and speeds corresponding to 2.0 mmol∙L(-1), 3.5 mmol∙L(-1), lactate threshold (Dmax method) and peak lactate determined in the laboratory and in the Hoff circuit soccer-specific test. Sixteen soccer players (16±1 years) underwent two incremental tests (laboratory and Hoff circuit tests). The speeds were significantly higher in the treadmill test than on the Hoff circuit (2.0 mmol∙L(-1): 9.5±1.2 and 8.1±1.0 km∙h(-1); 3.5 mmol∙L(-1): 12.0±1.2 and 10.2±1.1 km∙h(-1); Dmax: 11.4±1.4 and 9.3±0.4 km∙h(-1); peak lactate: 14.9±1.6 and 10.9±0.8 km∙h(-1)). The HR corresponding to 3.5 mmol∙L-1 was significantly higher on the Hoff circuit compared to the laboratory test (187.5±18.0 and 178.2±17.6 bpm, respectively; P <0.001), while the RPE at the last incremental stage was lower on the Hoff circuit (P < 0.01). The speeds during the Hoff specific soccer test and the HR corresponding to 2.0 mmol∙L(-1), 3.5 mmol∙L(-1) and Dmax/threshold were different compared with the laboratory test. The present study shows that it is possible to assess submaximal endurance related variables specifically in soccer players.

Determination of VO2-Intensity Relationship and MAOD in Tethered Swimming.

This study aimed to test the reproducibility of the maximal accumulated oxygen deficit (MAOD) values and VO2-intensity relationship parameters as measured during tethered swimming. 9 swimmers performed an incremental test to determine the maximal aerobic force (MAF), 6 submaximal efforts to develop VO2-intensity relationship, and an exhaustive effort to determine MAOD. The tests were performed twice. The reproducibility of the measurements was tested using intraclass correlation (ICC), typical error (TE) and coefficient of variation (CV). High levels of reproducibility were observed for MAF (TE=2.6 N; CV=4.3%; ICC=0.98) and VO2-intensity relationship parameters, as intercept (TE=0.01 L.min(-1); CV=11.4%; ICC=0.97), slope (TE=0.002 L.min(-1).N(-1); CV=3.1%; ICC=0.97) and coefficient of determination (TE=0.02; CV=1.8%; ICC=0.47). The MAOD values measured during the test (2.9±1.1 L and 45.3±14.0 mL.Kg(-1)) and retests (2.9±1.1 L and 45.2±12.6 mL.Kg(-1)) were highly correlated (absolute values: ICC=0.93; relative to body mass values: ICC=0.89) and presented low values of TE (0.3 L and 4.3 mL.Kg(-1)) and CV (9.5% for absolute and 9.6% for relative to body mass values). Thus, we demonstrated the potential use of tethered swimming to assess anaerobic capacity in an aquatic environment.

MAOD Determined in a Single Supramaximal Test: a Study on the Reliability and Effects of Supramaximal Intensities.

The main barrier to the wide use of maximal accumulated oxygen deficit (MAOD) is the considerable time required to apply several sub- and supra-maximal exercise sessions. The main question of this study was whether the determination of MAOD using a single supramaximal exercise session (MAODALT) is valid and reliable in running. We investigated the effects of the supramaximal exercise intensity (A) and the reliability of a single supramaximal exercise session (B) to assess MAOD in treadmill running. For this aim 29 subjects participated in A & B studies with single allocation "A" (n=15) and "B" (n=14). The conventional MAOD and 8 MAODALT were determined in exhaustive efforts varying between 100-150% at an intensity associated with maximal oxygen uptake (i+V˙O2MAX). In B study 2 supramaximal efforts were applied to analyze the test-retest reliability. Non-significant differences were found between MAOD and the 8 values of MAODALT. Despite the MAOD being statistically correlated with the MAODALT 100% i+V˙O2MAX (0.490.59), MAODALT determined at 115% of i+V˙O2MAX (52.4±1.7 mL·kg(-1)) presented the higher correlation values (0.650.77) and concordance. In addition, the MAOD at 115% of i+V˙O2MAX presented high test-retest reliability. MAODALT determined at 115% of i+V˙O2MAX was a valid and reliable method to assess MAOD in running.

Running-based Anaerobic Sprint Test as a Procedure to Evaluate Anaerobic Power.

The aim of this study was to evaluate the use of the running anaerobic sprint test (RAST) as a predictor of anaerobic capacity, compare it to the maximal accumulated oxygen deficit (MAOD) and to compare the RAST's parameters with the parameters of 30-s all-out tethered running on a treadmill. 39 (17.0±1.4 years) soccer players participated in this study. The participants underwent an incremental test, 10 submaximal efforts [50-95% of velocity correspondent to VO(2MAX) (vVO(2MAX))] and one supramaximal effort at 110% of vVO(2MAX) for the determination of MAOD. Furthermore, the athletes performed the RAST. In the second stage the 30-s all-out tethered running was performed on a treadmill (30-s all-out), and compared with RAST. No significant correlation was observed between MAOD and RAST parameters. However, significant correlations were found between the power of the fifth effort (P5) of RAST with peak and mean power of 30-s all-out (r=0.73 and 0.50; p<0.05, respectively). In conclusion, the parameters from RAST do not have an association with MAOD, suggesting that this method should not be used to evaluate anaerobic capacity. Although the correlations between RAST parameters with 30-s all-out do reinforce the RAST as an evaluation method of anaerobic metabolism, such as anaerobic power.

Relationship of aerobic and anaerobic parameters with 400 m front crawl swimming performance.

The aims of the present study were to investigate the relationship of aerobic and anaerobic parameters with 400 m performance, and establish which variable better explains long distance performance in swimming. Twenty-two swimmers (19.1±1.5 years, height 173.9±10.0 cm, body mass 71.2±10.2 kg; 76.6±5.3% of 400 m world record) underwent a lactate minimum test to determine lactate minimum speed (LMS) (i.e., aerobic capacity index). Moreover, the swimmers performed a 400 m maximal effort to determine mean speed (S400m), peak oxygen uptake ([Formula: see text]) and total anaerobic contribution (CANA). The CANA was assumed as the sum of alactic and lactic contributions. Physiological parameters of 400 m were determined using the backward extrapolation technique ([Formula: see text] and alactic contributions of CANA) and blood lactate concentration analysis (lactic anaerobic contributions of CANA). The Pearson correlation test and backward multiple regression analysis were used to verify the possible correlations between the physiological indices (predictor factors) and S400m (independent variable) (p < 0.05). Values are presented as mean ± standard deviation. Significant correlations were observed between S400m (1.4±0.1 m·s-1) and LMS (1.3±0.1 m·s-1; r = 0.80), [Formula: see text] (4.5±3.9 L·min-1; r = 0.72) and CANA (4.7±1.5 L·O2; r= 0.44). The best model constructed using multiple regression analysis demonstrated that LMS and [Formula: see text] explained 85% of the 400 m performance variance. When backward multiple regression analysis was performed, CANA lost significance. Thus, the results demonstrated that both aerobic parameters (capacity and power) can be used to predict 400 m swimming performance.

MCT1 and MCT4 kinetic of mRNA expression in different tissues after aerobic exercise at maximal lactate steady state workload.

We evaluate the mRNA expression of monocarboxylate transporters 1 and 4 (MCT1 and MCT4) in skeletal muscle (soleus, red and white gastrocnemius), heart and liver tissues in mice submitted to a single bout of swimming exercise at the maximal lactate steady state workload (MLSSw). After 72 h of MLSS test, the animals were submitted to a swimming exercise session for 25 min at individual MLSSw. Tissues and muscle samples were obtained at rest (control, n=5), immediately (n=5), 5 h (n=5) and 10 h (n=5) after exercise for determination of the MCT1 and MCT4 mRNA expression (RT-PCR). The MCT1 mRNA expression in liver increased after 10 h in relation to the control, immediate and 5 h groups, but the MCT4 remained unchanged. The MCT1 mRNA expression in heart increased by 31 % after 10 h when compared to immediate, but no differences were observed in relation to the control group. No significant differences were observed for red gastrocnemius in MCT1 and MCT4 mRNA expression. However, white gastrocnemius increased MCT1 mRNA expression immediately when compared to rest, 5 and 10 h test groups. In soleus muscle, the MCT1 mRNA expression increased immediately, 5 and 10 h after exercise when compared to the control. In relation to MCT4 mRNA expression, the soleus increased immediately and 10 h after acute exercise when compared to the control group. The soleus, liver and heart were the main tissues that showed improved the MCT1 mRNA expression, indicating its important role in controlling MLSS concentration in mice.

Nonfunctional overreaching leads to inflammation and myostatin upregulation in swiss mice.

The aims of the this study were a) to verify whether the performance decrease induced by nonfunctional overreaching (NFOR) is linked to high concentrations of cytokines in serum, skeletal muscles and liver; b) to verify muscle myostatin adaptation to NFOR; c) to verify the effects of chronic glucose supplementation on the parameters mentioned above. Mice were divided into control (C), trained (TR), overtrained (OTR) and supplemented overtrained (OTR + S). The incremental load test (ILT) and exhaustive test (ET) were used to measure performances before and after exercise protocols. 24 h after ET, muscles and liver were removed and stored at -80°C for subsequent measurements. Total blood was collected from decapitation for subsequent determination of cytokine concentrations. Generally, OTR and OTR + S presented higher contents of IL-6, TNF-alpha, GLUT-4 and myostatin in muscle samples compared to C and TR. Glucose supplementation attenuated the high contents of IL-6, TNF-alpha and IL-15 in liver, and of IL-6 in serum. In summary, NFOR led to low-grade chronic inflammation and myostatin upregulation.

Aerobic and anaerobic performances in tethered swimming.

The purpose of this study was to investigate whether the critical force (CritF) and anaerobic impulse capacity (AIC) - estimated by tethered swimming - reflect the aerobic and anaerobic performance of swimmers. 12 swimmers performed incremental test in tethered swimming to determine lactate anaerobic threshold (AnTLAC), maximal oxygen uptake ( ˙VO2MAX) and force associated with the ˙VO2MAX (i ˙VO2MAX). The swimmers performed 4 exhaustive (tlim) exercise bouts (100, 110, 120 and 130% i ˙VO2MAX) to compute the CritF and AIC (F vs. 1/tlim model); a 30-s all-out tethered swimming bout to determine their anaerobic fitness (ANF); 100, 200, and 400-m time-trials to determine the swimming performance. CritF (57.09±11.77 N) did not differ from AnTLAC (53.96±11.52 N, (P>0.05) but was significantly lower than i ˙VO2MAX (71.02±8.36 N). In addition, CritF presented significant correlation with AnTLAC (r=0.76; P<0.05) and i ˙VO2MAX (r=0.74; P<0.05). On the other hand, AIC (286.19±54.91 N.s) and ANF (116.10±13.66 N) were significantly correlated (r=0.81, p<0.05). In addition, CritF and AIC presented significant correlations with all time-trials. In summary, this study demonstrates that CritF and AIC can be used to evaluate AnTLAC and ANF and to predict 100, 200, and 400-m free swimming.

Propulsive force asymmetry during tethered-swimming.

This study aimed to determine whether: i) tethe-red-swimming can be used to identify the asymmetry during front crawl swimming style; ii) swimmers that perform unilateral breathing present greater asymmetry in comparison to others that use bilateral breathing; iii) swimmers of best performance present smaller asymmetry than their counterparts; iv) repeated front crawl swimming movements influence body asymmetry. 18 swimmers were assessed for propulsive force parameters (peak force, mean force, impulse and rate of force development) during a maximal front crawl tethered-swimming test lasting 2 min. A factorial analysis showed that propulsive forces decreased at the beginning, intermediate and end of the test (p<0.05), but the asymmetries were not changed at different instants of the test. When breathing preference (uni- or bilateral) was analyzed, asymmetry remained unchanged in all force parameters (p>0.05). When performance was considered (below or above mean group time), a larger asymmetry was found in the sub-group of lower performance in comparison to those of best performance (p<0.05). Therefore, the asymmetries of the propulsive forces can be detected using tethered-swimming. The propulsive forces decreased during the test but asymmetries did not change under testing conditions. Although breathing preference did not influence asymmetry, swimmers with best performance were less asymmetric than their counterparts.

The effects of physical fitness and body composition on oxygen consumption and heart rate recovery after high-intensity exercise.

The aim of this study was to investigate the potential relationship between excess post-exercise oxygen consumption (EPOC), heart rate recovery (HRR) and their respective time constants (tvo2 and t HR) and body composition and aerobic fitness (VO2max) variables after an anaerobic effort. 14 professional cyclists (age=28.4±4.8 years, height=176.0±6.7 cm, body mass=74.4±8.1 kg, VO2max=66.8±7.6 mL·kg - 1·min - 1) were recruited. Each athlete made 3 visits to the laboratory with 24 h between each visit. During the first visit, a total and segmental body composition assessment was carried out. During the second, the athletes undertook an incremental test to determine VO2max. In the final visit, EPOC (15-min) and HRR were measured after an all-out 30 s Wingate test. The results showed that EPOC is positively associated with % body fat (r=0.64), total body fat (r=0.73), fat-free mass (r=0.61) and lower limb fat-free mass (r=0.55) and negatively associated with HRR (r= - 0.53, p<0.05 for all). HRR had a significant negative correlation with total body fat and % body fat (r= - 0.62, r= - 0.56 respectively, p<0.05 for all). These findings indicate that VO2max does not influence HRR or EPOC after high-intensity exercise. Even in short-term exercise, the major metabolic disturbance due to higher muscle mass and total muscle mass may increase EPOC. However, body fat impedes HRR and delays recovery of oxygen consumption after effort in highly trained athletes.

A semi-tethered test for power assessment in running.

We analyzed the usefulness of a semi-tethered field running test (STR) and the relationships between indices of anaerobic power, anaerobic capacity and running performance in 9 trained male sprinters (22.2 ± 2.9 yrs, 176 ± 1 cm, 68.0 ± 9.4 kg). STR involved an all out 120 m run attached to an apparatus that enabled power calculation from force and velocity measures. Subjects also carried out a cycloergometer Wingate Anaerobic Test (WT), an all out 300 m run and had accessed their maximal accumulated oxygen deficit (MAOD) on a treadmill. Peak and mean powers attained in STR (1720 ± 221 and 1391 ± 201 W) were greater but significantly related (r = 0.82; P < 0.01) to those in the WT (808 ± 130 and 603 ± 87 W). In addition, power measures derived from the STR were stronger related to running performance compared to those from the WT (r = 0.81-0.94 vs. 0.68-0.84; P < 0.05). Relationships between MAOD and most power indices were only weak to moderate. These results support the usefulness of STR for specific power assessment in field running and suggest that anaerobic power and capacity are not related entities, irrespective of having been evaluated using similar or dissimilar exercise modes.

Anaerobic contribution during maximal anaerobic running test: correlation with maximal accumulated oxygen deficit.

The aims of this study were: (i) to measure energy system contributions in maximal anaerobic running test (MART); and (ii) to verify any correlation between MART and maximal accumulated oxygen deficit (MAOD). Eleven members of the armed forces were recruited for this study. Participants performed MART and MAOD, both accomplished on a treadmill. MART consisted of intermittent exercise, 20 s effort with 100 s recovery, after each spell of effort exercise. Energy system contributions by MART were also determined by excess post-exercise oxygen consumption, lactate response, and oxygen uptake measurements. MAOD was determined by five submaximal intensities and one supramaximal intensity exercises corresponding to 120% at maximal oxygen uptake intensity. Energy system contributions were 65.4±1.1% to aerobic; 29.5±1.1% to anaerobic a-lactic; and 5.1±0.5% to anaerobic lactic system throughout the whole test, while only during effort periods the anaerobic contribution corresponded to 73.5±1.0%. Maximal power found in MART corresponded to 111.25±1.33 mL/kg/min but did not significantly correlate with MAOD (4.69±0.30 L and 70.85±4.73 mL/kg). We concluded that the anaerobic a-lactic system is the main energy system in MART efforts and this test did not significantly correlate to MAOD.

Hematological parameters and anaerobic threshold in Brazilian soccer players throughout a training program.

We assessed the responses of hematological parameters and their relationship to the anaerobic threshold of Brazilian soccer players during a training program. Twelve athletes were evaluated at the beginning (week 0, T1), in the middle (week 6, T2), and at the end (week 12, T3) of the soccer training program. On the first day at 7:30 am, before collecting the blood sample at rest for the determination of the hematological parameters, the athletes were conducted to the anthropometric evaluation. On the second day at 8:30 am, the athletes had their anaerobic threshold measured. Analysis of variance with Newman-Keuls'post hoc was used for statistical comparisons between the parameters measured during the soccer training program. Correlations between the parameters analyzed were determined using the Pearson's correlation coefficient. Erythrocytes concentration, hemoglobin, and hematocrit were significantly increased from T1 to T2. The specific soccer training program led to a rise in erythrocytes, hemoglobin, and hematocrit from T1 to T2. We assumed that these results occurred due to the plasma volume reduction and may be explained by the soccer training program characteristics. Furthermore, we did not observe any correlation between the anaerobic threshold and the hematological parameters.