Within- and between-day reliability and repeatability of neuromuscular function assessment in females and males.

The study evaluated the reliability and repeatability of the force and surface electromyography activity (EMG) outcomes obtained through voluntary and electrically evoked contractions of knee extensors in females (n = 18) and males (n = 20) and compared these data between sexes. Maximal isometric voluntary contractions (iMVCs) of knee extensors associated with electrical stimulation of the femoral nerve were performed over 4 days (48-h interval), with the first day involving familiarization procedures, the second involving three trials (1-h interval), and the third and fourth involving just one trial. The intraclass correlation coefficient (ICC), coefficient of variation (CV), and repeatability of outcomes from within- and between-day trials were determined for each sex. Females presented lower maximal voluntary force during iMVC (iMVCForce) and associated vastus lateralis EMG activity (root mean square, RMSVL), force evoked by potentiated doublet high-frequency (Db100Force) and single stimuli (Qtw), and M-wave amplitude than males (P ≤ 0.01, partial eta squared ≥0.94). Voluntary activation (VA) and RMSVL/M-wave amplitude did not differ between sexes. iMVCForce, VA, Db100Force, Qtw, and M-wave amplitude were the most reliable outcomes in within-day trials, with similar results between sexes (ICC > 0.62; CV < 6.4%; repeatability: 12.2%-22.6%). When investigating between-day trials, the iMVCForce, VA, Db100Force, and Qtw were the most reliable (ICC > 0.66; CV < 7.5%; repeatability: 13.2%-33.45%) with similar results between sexes. In conclusion, females presented lower iMVCForce and evoked response than males. Although reliability and repeatability statistics vary between trials, data (e.g., from EMG or force signal), and sexes, most of the outcomes obtained through this technique are reliable in females and males.NEW & NOTEWORTHY Although reliability and repeatability of knee extensors vary according to the type of neuromuscular function outcome (e.g., from force or EMG responses), the trial intervals (i.e., hours or days), and the sex of the participant, most force and EMG outcomes obtained through these neuromuscular assessment protocols present ICC > 0.75, very good CV (<10%), and repeatability <25% in within- and between-day trials in both sexes.

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.

Beneficial Performance Effects of Training Load Intensification Can Be Abolished by Functional Overreaching: Lessons From a Water Polo Study in Female Athletes.

ABSTRACT: Brisola, GMP, Dutra, YM, Murias, JM, and Zagatto, AM. Beneficial performance effects of training load intensification can be abolished by functional overreaching: Lessons from a water polo study in female athletes. J Strength Cond Res 37(6): e391-e402, 2023-The purpose of this study was to compare the outcomes from 2 weeks of training load intensification strategy in female water polo players diagnosed with functional overreaching (F-OR) with no F-OR players (acute fatigue) on the performance outcomes and hormonal, immunological, and cardiac autonomic nervous system responses. Twenty-two female water polo players were allocated into control and intensification group during 7 weeks. The swimming performance, biochemical parameters, heart rate variability, profile of mood states, and upper respiratory tract infection symptoms were assessed twice before and twice after 2 weeks of intensification period. F-OR showed a worsening in total time of the repeated sprint ability (RSA) test compared with the control group and the acute fatigue group after intensification ( p ≤ 0.035). Furthermore, after the tapering period, the F-OR group maintained worse total time of the RSA test than the acute fatigue group ( p = 0.029). In addition, the acute fatigue group showed improvement in total time of the RSA test after intensification compared with the control group ( p < 0.001). No significant interactions were found for the other parameters. Therefore, periods of intensification without the F-OR development can promote higher gains in the total time of the RSA test after intensification and tapering period.

Validity of a Taekwondo-Specific Test to Measure VO2peak and the Heart Rate Deflection Point.

Sant'Ana, J, Franchini, E, Murias, JM, and Diefenthaeler, F. Validity of a taekwondo-specific test to measure VO2peak and the heart rate deflection point. J Strength Cond Res 33(9): 2523-2529, 2019-This study investigated whether the progressive specific taekwondo test (PSTT) is a valid test to measure peak oxygen consumption (VO2peak) and the heart rate deflection point (HRDP) in taekwondo athletes. Eighteen male black belt athletes (25.3 ± 4.8 years; 8.2 ± 4.7 years of practice; 171.8 ± 4.7 cm; 76.1 ± 8.2 kg, and 13.1 ± 2.9% body fat) involved in regional- and national-level competitions performed the PSTT and an incremental treadmill test (IT). The following variables were analyzed: VO2peak, respiratory quotient, oxygen consumption at the HRDP (VO2HRDP), peak heart rate (HRpeak), HRDP, and peak posttest blood lactate concentration. During the PSTT, the peak kick frequency (FKpeak) and kick frequency at the HRDP (FKHRDP) were also obtained. During the IT, the peak speed and the speed at the HRDP were identified by the Dmax method (the first and last points of the curve were connected by a straight line, and the most distant point of the curve to the line was considered as the HRDP). No differences were observed between VO2 responses during the PSTT and IT (p > 0.05). VO2peak and VO2HRDP presented bias (1.3 ml·kg·min and -0.78 ml·kg·min, respectively) derived from the Bland and Altman plots, with the 95% limits of agreement indicating that the differences between the 2 measures can reach 11% for VO2peak and 17% for VO2HRDP. The PSTT is a valid tool to assess aerobic power and capacity in taekwondo athletes based on direct comparisons to a treadmill test. The test presents more specific variables for the assessment and training of taekwondo athletes, such as FKpeak and FKHRDP, which can be used to determine and control the effects of training and help coaches in prescribing training programs.