Repeated cold-water immersion improves autonomic cardiac modulation following five sessions of high-intensity interval exercise.

PURPOSE: The study aimed to investigate the effect of repeated cold-water immersion (CWI) after high-intensity interval exercise sessions on cardiac-autonomic modulation, neuromuscular performance, muscle damage markers, and session internal load. METHODS: Twenty-one participants underwent five sessions of high-intensity interval exercise (6-7 bouts of 2 min; pause of 2 min) over a two-week period. Participants were allocated randomly into either a group that underwent CWI (11-min; 11 °C) or a group that performed passive recovery after each exercise session. Before the exercise sessions were performed, countermovement jump (CMJ) and heart rate variability were recorded (i.e., rMSSD, low and high frequency power and its ratio, SD1 and SD2). Exercise heart rate was calculated by recording the area under the curve (AUC) response. Internal session load was evaluated 30 min after each session. Blood concentrations of creatine kinase and lactate dehydrogenase were analyzed before the first visit and 24 h after the last sessions. RESULTS: The CWI group presented higher rMSSD than the control group at each time point (group-effect P = 0.037). The SD1 was higher in CWI group when compared to the control group following the last exercise session (interaction P = 0.038). SD2 was higher in CWI group compared to the control group at each time point (group-effect P = 0.030). Both groups presented equal CMJ performance (P > 0.05), internal load (group-effect P = 0.702; interaction P = 0.062), heart rate AUC (group-effect P = 0.169; interaction P = 0.663), and creatine kinase and lactate dehydrogenase blood concentrations (P > 0.05). CONCLUSION: Repeated post-exercise CWI improves cardiac-autonomic modulation. However, no differences in neuromuscular performance, muscle damage markers, or session internal load were demonstrated between the groups.

Sodium bicarbonate induces alkalosis, but improves high-intensity cycling performance only when participants expect a beneficial effect: a placebo and nocebo study.

The study aimed to investigate the effects of sodium bicarbonate (NaHCO3) intake with divergent verbal and visual information on constant load cycling time-to-task failure, conducted within the severe intensity domain. Fifteen recreational cyclists participated in a randomized double-blind, crossover study, ingesting NaHCO3 or placebo (i.e., dextrose), but with divergent information about its likely influence (i.e., likely to induce ergogenic, inert, or harmful effects). Performance was evaluated using constant load cycling time to task failure trial at 115% of peak power output estimated during a ramp incremental exercise test. Data on blood lactate, blood acid-base balance, muscle electrical activity (EMG) through electromyography signal, and the twitch interpolation technique to assess neuromuscular indices were collected. Despite reduced peak force in the isometric maximal voluntary contraction and post-effort peripheral fatigue in all conditions (P < 0.001), neither time to task failure, EMG nor, blood acid-base balance differed between conditions (P > 0.05). Evaluation of effect sizes of all conditions suggested that informing participants that the supplement would be likely to have a positive effect (NaHCO3/Ergogenic: 0.46; 0.15-0.74; Dextrose/Ergogenic: 0.45; 0.04-0.88) resulted in improved performance compared to control. Thus, NaHCO3 ingestion consistently induced alkalosis, indicating that the physiological conditions to improve performance were present. Despite this, NaHCO3 ingestion did not influence performance or indicators of neuromuscular fatigue. In contrast, effect size estimates indicate that participants performed better when informed that they were ingesting an ergogenic supplement. These findings suggest that the apparently ergogenic effect of NaHCO3 may be due, at least in part, to a placebo effect.

Menstrual cycle impacts adipokine and lipoprotein responses to acute high-intensity intermittent exercise bout.

Due to hormonal fluctuation, the menstrual cycle impacts inflammatory response and lipid metabolism; moreover, the anti-atherogenic and anti-inflammatory effects of exercise in this cycle, mainly high-intensity intermittent exercise (HIIE), need to be examined. Therefore, the aim of the current study was to investigate the influence of menstrual cycle phases on adipokine and lipoprotein responses after acute HIIE sessions in healthy women. Fourteen women (age: 24 ± 2 years; BMI: 22.79 ± 1.89 kg·m2) were recruited to perform two HIIE sessions (10 × 1 min running at 90% of maximum aerobic velocity, with 1 min recovery); one during the follicular phase (FP) and other during the luteal phase (LP), randomly. Blood samples were collected at rest, immediately, and 60 min after HIIE sessions. Macrophage inflammatory protein-1α (MIP-1α), leptin, adiponectin, total cholesterol, triacylglycerol (TAG), HDL-c, and glucose concentrations were analyzed. At rest, higher MIP-1α concentrations were observed during the LP compared to FP (p = 0.017). Likewise, leptin (p = 0.050), LDL-c (p = 0.015), and non-HDL (p = 0.016) were statistically higher in the LP. In contrast, the adiponectin/leptin ratio was lower in the LP compared to the ratio found in the FP (p = 0.032). Immediately post-HIIE sessions, in both menstrual phases, higher TAG (p = 0.001) and HDL-c (p = 0.001) concentrations were found, which returned to resting levels after 60 min. In conclusion, adipokine and lipoprotein responses after a single HIIE session are regulated by the phase of the menstrual cycle, contributing to inflammatory conditions, and demonstrating the importance of considering the phases of the menstrual cycle for the periodization of physical training.

Peripheral BDNF and psycho-behavioral aspects are positively modulated by high-intensity intermittent exercise and fitness in healthy women.

Acute high-intensity intermittent exercise (HIIE) induces the myokine secretion associated with neurogenesis, as well brain-derived neurotrophic factor (BDNF); however, it remains unknown how the menstrual phase influences this secretion after an acute exercise session. The current study aimed to investigate the effects of HIIE performed in luteal and follicular menstrual phases on BDNF, cognitive function, mood, and exercise enjoyment. Fourteen healthy women completed four experimental sessions, randomly. One graded exercise test (GXT) and one HIIE session (10 × 1-min runs 90% peak GXT velocity [1-min recovery]) were performed for each menstrual phase. Blood samples were collected at rest and immediately after efforts, and the profile of mood states questionnaire (POMS) and Stroop-task test were applied. During the HIIE, subjective scales were applied (feeling, felt arousal, rate of perceived exertion, and physical activity enjoyment). The main results showed that the serum BDNF presented no difference between menstrual phases (p = 0.870); however, HIIE increased BDNF concentration in both menstrual phases (p = 0.030). In addition, the magnitude of circulating BDNF variation (Δ%BDNF) and [Formula: see text] demonstrated an inverse relationship in the follicular phase (r = - 0.539, p = 0.046), whereas in the luteal phase, Δ%BDNF was negatively correlated with time test (r = - 0.684, p = 0.007) and RPE (r = - 0.726, p = 0.004) in GXT. No differences between menstrual phases were observed for POMS (p ≥ 0.05); however, HIIE attenuated tension (p < 0.01), depression (p < 0.01), and anger moods (p < 0.01), independently of menstrual phases. The subjective scales and Stroop-task test did not show differences. In conclusion, menstrual cycle phase does not affect serum BDNF levels, cognitive function, mood, and exercise enjoyment. Contrary, HIIE increases peripheral BDNF and attenuates tension, depression, and anger independently of menstrual phase. In addition, Δ%BDNF was correlated with physical fitness in the follicular phase, exhibiting higher changes in women with lower physical fitness status.