Reliability of Time to Exhaustion Above the Power Output at VO2peak in Trained Mountain Bikers.

To our knowledge, no study has investigated the reliability of the time to exhaustion (TTE) test during constant-load trials in Olympic distance cross-country mountain bike (XCO-MTB) athletes. Thus, the aim was to analyze the reliability of the TTE test at intensities above peak oxygen uptake (VO2peak) in trained XCO-MTB athletes. Fifteen male XCO-MTB athletes (mean ± SD: age 31.5 ± 6.6 years, stature 174.0 ± 5.4 cm, body mass 67.2 ± 5.1 kg, VO2peak 64.5 ± 4.7 mL·kg-1·min-1) completed 2 TTE tests on the cycle ergometer with 4 different intensities above the maximal work rate in the incremental test (Wmax) (105%, 120%, 130%, and 140% of Wmax). There was moderate reliability between TTE tests at 105% (intraclass correlation coefficient (ICC) = 0.81, p ≤ 0.001; coefficient of variation (CV) = 9.1%; standard error of measurement (SEM) = 18.3%), and 120% (ICC = 0.88, p ≤ 0.001; CV = 6.6%; SEM = 9.3%) Wmax. For intensities of 130% (ICC = 0.53, p = 0.018; CV = 9.2%; SEM = 15.8%) and 140% (ICC = 0.56, p = 0.012; CV = 12.2%; SEM = 13.5%) Wmax, the reliability results proved to be questionable. In addition, no significant differences were found between the 2 TTE tests in all intensities (p > 0.05). Caution should be taken when assessing TTE above VO2peak or when using it as a performance indicator, given its moderate to questionable reliability.

Correction: Acute effects of single dose transcranial direct current stimulation on muscle strength: A systematic review and meta-analysis.

[This corrects the article DOI: 10.1371/journal.pone.0209513.].

Effects of Transcranial Direct Current Stimulation With Caffeine Intake on Muscular Strength and Perceived Exertion.

Lattari, E, Vieira, LAF, Oliveira, BRR, Unal, G, Bikson, M, de Mello Pedreiro, RC, Marques Neto, SR, Machado, S, and Maranhão-Neto, GA. Effects of transcranial direct current stimulation with caffeine intake on muscular strength and perceived exertion. J Strength Cond Res 33(5): 1237-1243, 2019-The aim of this study was to investigate the acute effects of transcranial direct current stimulation (tDCS) associated with caffeine intake on muscular strength and ratings of perceived exertion (RPE). Fifteen healthy young males recreationally trained (age: 25.3 ± 3.2 years, body mass: 78.0 ± 6.9 kg, height: 174.1 ± 6.1 cm) were recruited. The experimental conditions started with the administration of caffeine (Caff) or placebo (Pla) 1 hour before starting the anodal tDCS (a-tDCS or sham). There was an intake of 5 mg·kg of Caff or 5 mg·kg of Pla. After the intake, a-tDCS or sham was applied in the left dorsolateral prefrontal cortex with intensity of 2 mA and 20 minutes of duration. The experimental conditions were defined as Sham + Pla, a-tDCS + Pla, Sham + Caff, and a-tDCS + Caff. After the conditions, muscular strength and RPE were verified. Muscular strength was determined by volume load performed in bench press exercise. Muscular strength in Sham + Pla condition was lower compared with all others conditions (p < 0.05). The RPE in the Sham + Pla was greater compared with a-tDCS + Caff (p < 0.05). Muscular strength was greater in all experimental conditions, and a-tDCS + Caff had lower RPE compared with placebo. When very little gains in muscle strength are expected, both caffeine and tDCS were effective in increasing muscle strength. Besides, the improvement in RPE of the caffeine associated with a-tDCS could prove advantageous in participants experienced in strength training. In fact, coaches and applied sport scientists quantitating the intensity of training based on RPE.

Acute effects of single dose transcranial direct current stimulation on muscle strength: A systematic review and meta-analysis.

Previous studies investigating the effects of transcranial direct current stimulation (tDCS) on muscle strength showed no consensus. Therefore, the purpose of this article was to systematically review the literature on the effects of single dose tDCS to improve muscle strength. A systematic literature search was conducted on PubMeb, ISI Web of Science, SciELO, and Scopus using search terms regarding tDCS and muscle strength. Studies were included in accordance with Population, Intervention, Comparison, Outcomes, and Setting (PICOS) including criteria. Healthy men and women, strength training practitioners or sedentary were selected. The acute effects of single dose anode stimulus of tDCS (a-tDCS) and the placebo stimulus of tDCS (sham) or no interventions were considered as an intervention and comparators, respectively. Measures related to muscle strength were analyzed. To conduct the analyses a weighted mean difference (WMD) and the standardized mean difference (SMD) were applied as appropriate. A total of 15 studies were included in this systematic review and 14 in meta-analysis. Regarding the maximal isometric voluntary contraction (MIVC), a small effect was seen between tDCS and Sham with significant difference between the conditions (SMD = 0.29; CI95% = 0.05 to 0.54; Z = 2.36; p = 0.02). The muscular endurance measured by the seconds sustaining a percentage of MIVC demonstrated a large effect between tDCS and Sham (WMD = 43.66; CI95% = 29.76 to 57.55; Z = 6.16; p < 0.001), showing an improvement in muscular endurance after exposure to tDCS. However, muscular endurance based on total work showed a trivial effect between tDCS and Sham with no significant difference (SMD = 0.22; CI95% = -0.11 to 0.54; Z = 1.32, p = 0.19). This study suggests that the use of tDCS may promote increase in maximal voluntary contraction and muscular endurance through isometric contractions.

Differences in exercise intensity seems to influence the affective responses in self-selected and imposed exercise: a meta-analysis.

Self-selected exercise seems to promote positive affective responses due to the perceived autonomy associated with it. The objective of the present study was to determine the magnitude of differences in Feeling Scale (FS) responses during self-selected and imposed exercise sessions. The PRISMA Statement was adopted for this meta-analysis. The search used PubMed, Scopus, PsycINFO, and ISI Web of Knowledge databases. A total of 10 studies that compared the effects of self-selected and imposed exercise sessions on acute FS responses were included. The screening strategy included: exclusion of studies that were duplicated between databases, abstract screening, and text screening. The standardized mean difference (SMD) between self-selected and imposed exercise sessions categorized in five intensities (equal intensity: both exercises were performed at the same intensity, below lactate/ventilatory threshold (LT/VT): imposed exercise was performed at an intensity below the LT/VT, at LT/VT: imposed exercise was performed at the LT/VT intensity, above LT/VT: imposed exercise was performed at an intensity above the LT/VT, and different intensity: both exercises were performed at different intensities and the intensity of imposed session was not reported relative to LT/VT) and an overall SMD were calculated. Self-selected exercise was used as the reference condition. The subtotal SMD values were as follows: -0.10 (equal intensity), -0.36 (below LT/VT), -0.57 (at LT/VT), -1.30 (above LT/VT), and -0.09 (different intensity) and the overall SMD was -0.41. The results of the present study indicate that the difference between affective responses in self-selected and imposed exercise sessions is dependent on the intensity of the imposed exercise session.

We need to move more: Neurobiological hypotheses of physical exercise as a treatment for Parkinson's disease.

Parkinson's disease (PD) is one of the most prevalent neurodegenerative diseases in the world. The degeneration of dopaminergic neurons in the substantia nigra and chronic inflammation impair specific brain areas, which in turn result in lesser motor control, behavioral changes and cognitive decline. Nowadays, drug-treatments are the foremost approaches in treating PD. However, exercise has been shown to have powerful effects on PD, based on several neurobiological mechanisms. These effects may decrease the risk of developing PD by 33%. However, these mechanisms are unclear and little explored. Among several mechanisms, we propose two specific hypotheses: 1. Physical exercise reduces chronic oxidative stress and stimulates mitochondria biogenesis and up-regulation of authophagy in PD patients. Moreover, antioxidant enzymes (e.g. superoxide dismutase) become more active and effective in response to physical exercise. 2. Exercise stimulates neurotransmitter (e.g. dopamine) and trophic factors (BDNF, GDNF, FGF-2, IGF-1, among others) synthesis. These neurochemical phenomena promote neuroplasticity, which, in turn, decreases neural apoptosis and may delay the neurodegeneration process, preventing or decreasing PD development and symptoms, respectively.

Continuous and high-intensity interval training: which promotes higher pleasure?

OBJECTIVES: To compare the psychological responses to continuous (CT) and high-intensity interval training (HIT) sessions. METHODS: Fifteen men attended one CT session and one HIT session. During the first visit, the maximum heart rate, VO2Peak and respiratory compensation point (RCP) were determined through a maximal cardiopulmonary exercise test. The HIT stimulus intensity corresponded to 100% of VO2Peak, and the average intensity of both sessions was maintained at 15% below the RCP. The order of the sessions was randomized. Psychological and physiological variables were recorded before, during and after each session. RESULTS: There were no significant differences between the average percentages of VO2 during the two exercise sessions (HIT: 73.3% vs. CT: 71.8%; p = 0.779). Lower responses on the feeling scale (p≤0.01) and higher responses on the felt arousal scale (p≤0.001) and the rating of perceived exertion were obtained during the HIT session. Despite the more negative feeling scale responses observed during HIT and a greater feeling of fatigue (measured by Profile of Mood States) afterwards (p<0.01), the physical activity enjoyment scale was not significantly different between the two conditions (p = 0.779). CONCLUSION: Despite the same average intensity for both conditions, similar psychological responses under HIT and CT conditions were not observed, suggesting that the higher dependence on anaerobic metabolism during HIT negatively influenced the feeling scale responses.

Comparison of two proposed guidelines for aerobic training sessions.

The purpose was to compare 24 participants' acute physiological and affective responses to two aerobic prescriptions in three sessions. Anthropometry, International Physical Activity Questionnaire, and VO2max were recorded. In subsequent visits two aerobic prescriptions were randomly applied: one based on VO2max (PBVO2max) and another based on physical activity level (PBPA). Physiological and affective variables were measured in each session. The PBVO2max showed lower risk for dropout than the PBPA. An effect size analysis showed higher ratings on the Feeling Scale in the PBVO2max session at the end of exercise. After categorizing participants by fitness (High, Medium, and Low) according to VO2max, significant differences were observed for the training impulse between Low and High fitness categories, indicating PBVO2Max were sensitive in distinguishing levels of fitness. The PBVO2max, compared to PBPA, seems to provide better physiological and affective responses. VO2max (even if estimated) is recommended as the basis for aerobic prescriptions.

A new strategy for the implementation of an aerobic training session.

The objectives were to propose a new strategy for adjusting aerobic training variables based on the eighth American College of Sports Medicine (ACSM) guidelines and maximal aerobic power (&OV0312;O2max) and to establish energy expenditure (EE) recommendations for training, which depend on a subject's body mass (BM). Exclusively based on aerobic training recommendations that are available in the ACSM guidelines, 16 equally partitioned subcategories were created from the slope of a linear regression between the lower (16.4 ml·kg(-1)·min(-1)) and upper (61.2 ml·kg(-1)·min(-1)) limits of VO(2max) percentile tables and all aerobic variables (intensity: 30-85%Reserve, duration: 60-300 min·wk(-1), frequency: 3-5 d·wk(-1), and EE: 1,000-4,000 kcal·wk). ACSM's EE (EE(ACSM)) recommendation was compared to EE based on VO(2max) (EE(Actual)), BM, exercise intensity and duration combined, for five BM categories (60 to 100 kg). The following equations were generated to adjust aerobic training: Intensity (%(Reserve)) = VO(2max) (ml·kg(-1)·min(-1)) × 1.23 + 9.85, Duration (min·wk(-1)) = VO(2max) × 5.36-27.91, Frequency (d·wk(-1) = VO(2max) × 0.044 + 2.27, EE(ACSM) (kcal·wk(-1)) =VO(2max) × 82.61-1,055.29, and EE(Actual) (kcal·wk(-1)) = ([V(O2max) - 3.5] × Intensity + 3.5) × BM (kg)/200 × Frequency. A comparison of EE(ACSM) and EE(Actual) for 5 BM and 3 aerobic fitness categories demonstrated an effect size classification that is equal or superior to "large" in 9 of 15 comparisons, suggesting that EE(ACSM) adjustment is inadequate at least 60% of the time. Despite the need to verify the adequacy of the linear model and perform future cross-sectional and longitudinal studies, the present proposal first provides criteria to adjust aerobic training variables consistent with subject capacity, thus diminishing the risk of the imprecise aerobic prescription.