Joana Francisca Reis

Walking and running are vital components of human locomotion that contain time-dependent structures in their nature, which shed light on the control of individuals’ movement patterns (Hausdorff et ...

Repeated sprint ability (RSA) is a critical component of football, yet high-intensity effort leads to H⁺ accumulation. Sodium bicarbonate (SB) is an effective buffering agent, though evidence supporting its use among female football players remains limited. We conducted a randomized, double-blind, placebo-controlled, crossover trial (NCT06098794) to examine the acute effects of SB on RSA in recreational female football players. Eleven athletes completed two RSA sessions on a cycle ergometer under SB and placebo (PL) conditions. Each session involved 3 sets of 6 maximal 6 s sprints performed every 30 s, with a 5 min recovery between sets. Participants ingested 0.2 g·kg⁻¹ of the supplement 2 h prior to testing and 0.1 g·kg⁻¹ 1 h before the session. The results showed that SB induced a greater blood lactate accumulation (SB: 14.0 ± 4.32 vs. PL: 10.9 ± 3.55 mmol·L⁻¹, p = 0.010) and a greater elimination of CO₂ through breathing (p = 0.038), while maintaining muscle oxygenation. These physiological responses were accompanied by improved performance, as SB prevented a decline in mean power output from the first to the second set (SB: +1.4% vs. PL: −3.7%) and reduced the post-test drop in jump height (SB: −2.0% vs. PL: −8.2%). These findings suggest that SB supplementation may be useful to reduce muscular acidosis and fatigue in recreational female football players.

Soccer requires athletes to exhibit high levels of acceleration and speed, both of which are crucial for optimal performance. The acceleration–speed (A–S) profile is increasingly utilized to assess these sprinting capacities in soccer, providing in situ insights into an athlete’s maximal theoretical acceleration (A0) and speed (S0). This study aimed to investigate the association of external load metrics with A0 and S0 across different age groups in elite academy soccer athletes. One hundred thirty-six athletes, ranging from under-14 to B-team, participated in the study. Training sessions and matches were monitored over a season using Global Navigation Satellite System (GNSS) technology to collect data on the A–S profile and external load metrics. Stepwise regression analysis revealed a positive correlation, in several age groups (under-15, -17, -19, and -23 and B-team), between accumulation of sprint distance (Spr. Dist.) and an increased S0 (R 2: 0.30–0.52). However, no significant correlation was found between any external load metric and A0. These findings highlight the necessity of individualized training interventions and the inclusion of Spr. Dist. throughout the planning of the training load of young soccer athletes for the improvement of sprint capacity. It may also suggest that acceleration in youth soccer athletes may be influenced by other factors, such as strength training.

This study aimed to monitor the in-water and dryland interlimb asymmetry of young competitive swimmers throughout a full training macrocycle and verify possible associations with performance. Twenty-three young competitive swimmers (12.13 ± 0.74 years) were evaluated before (M1) and after (M2) a 16-week training macrocycle. The swimmers were timed at a 25 m front crawl (T25) and then evaluated in anthropometrics, mean peak (Fpeak) in-water forces and the shoulder internal rotator’s strength (IR) of dominant (D) and non-dominant (ND) limbs. The symmetry index was computed for both in-water (SyI_water) and dryland (SyI_land) environments followed by the rate of force transfer (RFT) estimation. While the swimmers have grown in height, arm span and hand surface area, accompanied by an improvement in T25, the other variables remained unchanged after the 16 weeks. A significant and moderate association was found between FpeakD (r = −0.47) or FpeakND (r = −0.41) and T25, as well as between the IRD (r = −0.51) or IRND (r = −0.57) and T25 in M1. In M2, the non-dominant side gained relevance mostly in FpeakND, showing a significant and high association with T25 (r = −0.68), like the FpeakD (r = −0.69) and IRD (r = −0.53). Most of the individual plots (>80%) were under 30% of SyI_water, with the faster swimmer values between 10 and 30%. It can be concluded that a 16-week training macrocycle is not enough to change the young swimmers’ in-water and dryland symmetry, but this does not seem to affect their front crawl sprint performance.

Introduction: Since sex-specific accumulated oxygen deficit (AOD) during high-intensity swimming remains unstudied, this study aimed to assess AOD during 50, 100, and 200 m front-crawl performances to compare the responses between sexes and analyse the effect of lean body mass (LBM). Methods: Twenty swimmers (16.2 ± 2.8 years, 61.6 ± 7.8 kg, and 48.8 ± 11.2 kg LBM—50% males) performed 50, 100, and 200 m to determine accumulated oxygen uptake (V̇O_2Ac). The swimmers also performed an incremental test from which five submaximal steps were selected to estimate the oxygen demand (V̇O_2demand) from the V̇O₂ versus velocity adjustment. V̇O₂ was sampled using a gas analyser coupled with a respiratory snorkel. AOD was the difference between V̇O_2demand and V̇O_2Ac, and LBM (i.e. lean mass not including bone mineral content) was assessed by dual-energy X-ray absorptiometry (DXA). Results: A two-way ANOVA evidenced an AOD increase with distance for both sexes: 19.7 ± 2.5 versus 24.9 ± 5.5, 29.8 ± 8.0 versus 36.5 ± 5.8, and 41.5 ± 9.4 versus 5.2 ± 11.9 ml × kg⁻¹, respectively, for 50, 100, and 200 m (with highest values for females, P < 0.01). Inverse correlations were observed between LBM and AOD for 50, 100, and 200 m (r = − 0.60, − 0.38 and − 0.49, P < 0.05). AOD values at 10 and 30 s elapsed times in each trial decreased with distance for both sexes, with values differing when female swimmers were compared to males in the 200 m trial (at 10 s: 2.6 ± 0.6 vs. 3.4 ± 0.6; and at 30 s: 7.9 ± 1.7 vs. 10.0 ± 1.8 ml × kg⁻¹, P < 0.05). Conclusion: LBM differences between sexes influenced AOD values during each trial, suggesting that reduced muscle mass in female swimmers plays a role on the higher AOD (i.e. anaerobic energy) demand than males while performing supramaximal trials.

The Nordic hamstring exercise (NHE) is a very popular exercise used to improve eccentric strength and prevent injuries. The aim of this investigation was to assess the reliability of a portable dynamometer that measures maximal strength (MS) and rate of force development (RFD) during the NHE. Seventeen physically active participants (34.8 ± 4.1 years; n = 2 women and n = 15 men) participated. Measurements occurred on two different days separated by 48–72 h. Test–retest reliability was calculated for bilateral MS and RFD. No significant test–retest differences were observed in NHE (test–retest [95% CI, confidence interval]) for MS [−19.2 N (−67.8; 29.4); p = 0.42] and RFD [−70.4 N·s⁻¹ (−178.4; 37.8); p = 0.19]. MS showed high reliability (intraclass correlation coefficient [ICC] [95% CI], =0.93 [0.80–0.97] and large within-subject correlation between test and retest [r = 0.88 (0.68; 0.95)]. RFD displayed good reliability [ICC = 0.76 (0.35; 0.91)] and moderate within-subject correlation between test and retest [r = 0.63 (0.22; 0.85)]. Bilateral MS and RFD displayed a coefficient of variation of 3.4% and 4.6%, respectively, between tests. The standard error of measurement and the minimal detectable change for MS was 44.6 arbitrary units (a.u.) and 123.6 a.u., and 104.6 a.u. and 290.0 a.u. for peak RFD. This study shows that MS and RFD can be measured for NHE using a portable dynamometer. However, not all exercises are suitable to apply to determine RFD, so caution must be taken when analyzing RFD during NHE.

This study aimed to compare muscle strength and power indicators according to bioimpedance spectroscopy’s phase angle (PhA) values, in resistance-trained (RT) men, while exploring associations between PhA and performance. Forty-four men aged 18–45 years, engaged in RT, were allocated according to PhA tertiles. Lean soft tissue (LST) and fat mass (%FM) were assessed using dual-energy x-ray absorptiometry; dynamic muscle strength using 1 repetition maximum (1RM) of bench press (BP) and back squat (BS) and muscle power using Wingate test (WT) and countermovement jump (CMJ). For WT and CMJ, the 3rd tertile was significantly higher than the 1st tertile (p = 0.027 and p = 0.018, respectively). Regarding BP 1RM, the 3rd tertile was significantly higher than the 2^nd tertile (p = 0.037). LST better explained the variability in the WT, BS and BP (p =< 0.001), while %FM better accounted for jump height in CMJ (p =< 0.001). PhA was a predictor of performance in both CMJ (p = 0.040) and BP (p = 0.012), independently of LST and %FM. Participants with higher PhA also displayed superior muscle strength of the upper limbs and greater muscle power of the lower limbs. PhA displayed significant moderate associations with performance in CMJ and BP, even after controlling for body composition. Still, LST was the most important predictor of muscle strength and power.

The current case study aimed to quantify within-subjects correlations between training load and well-being in elite male beach soccer players. Data were obtained over three consecutive days during the preparation camp for the FIFA Beach Soccer World Cup Russia 2021. The session rating of perceived exertion (s-RPE) and external training load metrics using global positioning system (GPS) were recorded. Eleven players reported perceived well-being (sleep quality, fatigue, muscle soreness and stress) using a Likert scale (Hooper Index) before breakfast. Within-subjects correlation coefficients between workload and well-being were calculated. Workload metrics and perceived well-being indices were significantly lower on day three than on days one and two. The Hooper Index presented a very large positive correlation with s-RPE (r = 0.86 [0.67, 0.94], 95% confidence interval, CI), exposure time (r = 0.88 [0.71, 0.95]), total distance (r = 0.83 [0.60, 0.93]), high-speed distance (r = 0.77 [0.50, 0.91]), and number of sprints (r = 0.75 [0.47, 0.90]). Sleep quality presented a moderate to large positive correlation with s-RPE (r = 0.51 [0.11, 0.77]), exposure time (r = 0.50 [0.10, 0.76]), high-speed distance (r = 0.53 [0.15, 0.78]), number of sprints (r = 0.62 [0.28, 0.83]) and total distance (r = 0.41 [0.18, 0.78]). Fatigue presented a large to very large positive correlation with s-RPE (r = 0.85 [0.66, 0.94]), exposure time (r = 0.90 [0.78, 0.96]), total distance (r = 0.86 [0.68, 0.94]), high-speed distance (r = 0.65 [0.31, 0.84]) and number of sprints (r = 0.56 [0.18, 0.79]). Muscle soreness presented a large to very large positive correlation with s-RPE (r = 0.79 [0.56, 0.91]), exposure time (r = 0.83 [0.62, 0.93]), total distance (r = 0.81 [0.59, 0.92]), high-speed distance (r = 0.75 [0.47, 0.89]) and number of sprints (r = 0.59 [0.22, 0.81]). Overall, workload presented a meaningful correlation with perceived well-being indices in elite male beach soccer players during a training camp. These findings suggest that workload metrics and perceived well-being indices can be implemented into the daily routine of an elite beach soccer team, which may assist coaches, sports scientists, and practitioners in better preparing players for beach soccer competitions.

Aims: The present study aimed to assess the ability of bioelectrical impedance vector analysis (BIVA) in discriminating fitness levels in futsal players, exploring the association of body composition and bioelectrical parameters with aerobic power. Methods: Forty-eight professional futsal players (age 23.8 ± 5.3 years) were involved in a cross-sectional study during their pre-season phase. Fat mass (FM) and muscle mass were determined by dual-energy X-ray absorptiometry. VO_2max was obtained by indirect calorimetry through a graded exercise test performed on a treadmill. Bioelectrical resistance (R), reactance (Xc), and phase angle (PhA) were directly measured using a foot-to-hand bioimpedance technology at a 50 kHz frequency. Bioelectric R and Xc were standardized for the participants’ height and used to plot the bioimpedance vector in the R-Xc graph according to the BIVA approach. Results: The participants divided into groups of VO_2max limited by tertiles showed significant differences in mean vector position in the R-Xc graph (p < 0.001), where a higher VO_2max resulted in a longer vector and upper positioning. FM, muscle mass, and PhA differed (p < 0.01) among the athletes grouped by tertiles of VO_2max, where athletes with a greater aerobic power showed a lower percentage of FM and a higher percentage of muscle mass and PhA. FM and PhA were associated with VO_2max (FM: r = −0.658, p < 0.001; PhA: r = 0.493, p < 0.001). These relationships remained significant after adjusting for age and body mass (FM: ß = −0.335, p = 0.046; PhA: ß = 0.351, p = 0.003). Conclusions: Bioelectrical impedance vectors positioned on the lower pole of the R-Xc graph identified futsal players with a lower VO_2max, while longer vectors corresponded to a greater aerobic power. Additionally, PhA, that describes the vector direction, was positively associated with VO_2max, while a higher FM negatively affected VO_2max in the futsal players. BIVA and PhA evaluation may represent a valid support for screening the aerobic fitness level in professional futsal players, when more sophisticated assessment methods are not available.