Figueiredo, DH, Figueiredo, DH, Moreira, A, Gonçalves, HR, and Stanganelli, LCR. Effect of overload and tapering on individual heart rate variability, stress tolerance, and intermittent running performance in soccer players during a preseason. J Strength Cond Res 33(5): 1222–1231, 2019—This study evaluates the weekly natural log of the root-mean-square difference of successive R-R intervals (lnRMSSDmean), its coefficient of variation (lnRMSSDcv), training load (TL), stress tolerance (ST), and changes in intermittent running performance in response to a 2-week overload (OL) followed by a 1-week taper (TP) during a preseason. Additionally, we determined the relationships between these variables. Ultra-short lnRMSSD, psychometric responses, and ratings of perceived exertion were evaluated daily among 16 under-19 soccer players. At the end of each training phase, the athletes performed the Yo-Yo Intermittent Recovery test level 1 (Yo-Yo). Group analysis showed a decrease in lnRMSSDmean and ST, increases in lnRMSSDcv, and decreases in the Yo-Yo during OL, with a return to baseline levels and a trivial increase in the Yo-Yo during TP. Small to very large correlations were found between lnRMSSDmean and lnRMSSDcv values, with changes in Yo-Yo, TL, monotony, and strain during the preseason (r values ranging from −0.27 to 0.82). No correlation was found between lnRMSSD responses and ST. During OL, athletes with decreases in lnRMSSDmean and increases in lnRMSSDcv accumulated higher perceived TL, with higher monotony and overall stress, and presented a decrease in ST and intermittent running performance, interpreted as a negative adaptation in response to the maintenance of higher TL. During TP, these responses were reversed, leading to an increase in intermittent running performance. In addition, subjective measures of ST may be used to provide early indicators of training adaptation in soccer players.

The purpose of this study was to investigate the effects of chronic beetroot juice (BRJ) supplementation on 10-km running performance in recreational runners. In a double-blind, placebo-controlled, crossover-designed study, fourteen male recreational runners (age: 27.8 ± 3.4 y) performed three 10-km running tests at baseline, under the conditions of BRJ supplementation and placebo (PLA). Supplementation was administered for three days, and on the day of the assessments, the ingestion occurred two hours before each test and consisted of a dose of 420 mL of BRJ in natura (8.4 mmol NO3-/day) or PLA with depleted NO3- (0.01 mmol NO3-/day). The mean velocity (MV) was calculated and the following variables were determined: maximum heart rate (HRmax), maximal rating of perceived exertion (RPEmax), and determined at pre and post test glucose concentrations (Glycpre, Glycpost), and lactate peak. There was no main effect between conditions regarding to 10-km running time performance (BRJ: 50.1 ± 5.3; PLA: 51.0 ± 5.1 min, p = 0.391) and total MV (BRJ: 12.1 ± 1.3; PLA: 11.9 ± 1.2 km·h-1, p = 0.321), as well as in the other analyzed variables. The time to complete the first half of the test (5 km) was statistically lower in the BRJ compared to that in the PLA (P = 0.027). In conclusion, chronic supplementation with BRJ increasing MV in the first half of the test and improves the final test time of ten of the fourteen runners, although we did not find a statistically significant difference in the performance of 10-km.

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Figueiredo, DH, Figueiredo, DH, Moreira, A, Gonçalves, HR, and Dourado, AC. Dose-response relationship between internal training load and changes in performance during the preseason in youth soccer players. J Strength Cond Res 35(8): 2294–2301, 2021—The aim of this study was to describe training intensity distribution based on the session rating of perceived exertion (sRPE) and heart rate (HR) methods and examine the dose-response relation between internal training load (ITL) and change in performance of 16 youth soccer players (mean ± SD age: 18.75 ± 0.68 years, height: 175.3 ± 5.5 cm, body mass: 68.7 ± 6.5 kg, and body fat: 10.7 ± 1.2%) belonging to a Brazilian first division team during a 3-week preseason. The sRPE and HR data were registered daily to calculate the ITL and the training intensity distribution, in 3 intensity zones (low, moderate, and high). The Yo-yo Intermittent Recovery Level 1 (Yo-yo IR1) was evaluated before and after experimental period. The total time spent in the low-intensity zone (HR method) was greater (p < 0.01) compared with the moderate- and high-intensity zones. No difference was observed between training intensity zones determined by the sRPE method (p > 0.05). Negative correlations were observed between weekly mean sRPE-TL (r = −0.69), Edward's-TL (r = −0.50), and change in Yo-yo IR1. Linear regression indicated that weekly mean sRPE-TL (F 1;14 = 13.3; p < 0.01) and Edward's-TL (F 1;14 = 4.8; p < 0.05) predicted 48.7 and 25.5% of the variance in performance change, respectively. Stepwise linear regression revealed that these 2-predictor variables (F 2;13 = 18.9; p < 0.001) explained 74.5% of the variance in performance change. The results suggest that the sRPE and HR methods cannot be used interchangeably to determine training intensity distribution. Moreover, sRPE-TL seems to be more effective than the HR-based TL method to predict changes in performance in youth soccer players.

Background: Long distance practice running are growing and nutritional ergogenic are commonly used as a potential aid in final training and competition performance. Caffeine (CAF) and carbohydrates (CHO) are among the most commonly used supplements due to their expected ergogenic properties that can optimize energetic systems. The objective of this study was to examine potential changes in 10-km running performance with acute isolated and combined CAF and CHO supplementation. Material and method: Fifteen recreational endurance-trained runners performed four 10-km running performance on an official athletic track (400 m) under four supplementation conditions: placebo and placebo (PLA+PLA), placebo and caffeine (PLA+CAF), placebo and carbohydrates (PLA+CHO), caffeine and carbohydrates (CAF+CHO). CAF and CHO supplementation consisted of capsules of 6 mg·kg-1 and 8% CHO solution (1 g·kg-1) respectively, ingested 60 and 30 minutes before the performance tests. Placebo was obtained through empty capsules for CAF and juice for CHO without sugar (Clight®). During each trial running speed to calculate 10-km mean velocity (MV) and maximum heart rate (HRmax) were analyzed. Results: There was a difference in the pacing strategy adopted by the runners with higher MV during the initial phase for PLA+CAF and CAF+CHO groups and in the final phase for PLA+ CHO. However, there was no statistically significant difference in 10-km running performance between the conditions, as well as for HRmax. Conclusions: The use of acute, isolated and combined CAF+CHO supplementation had influence in the pacing strategy, but no in 10- km final performance, of recreational runners.