Applied Physiology of Female Soccer: An Update

Nutritional optimization for female elite football players-topical review

Women's football is an intermittent sport characterized by frequent intense actions throughout the match. The high number of matches with limited recovery time played across a long competitive season underlines the importance of nutritional strategies to meet these large physical demands. In order to maximize sport performance and maintain good health, energy intake must be optimal. However, a considerable proportion of female elite football players does not have sufficient energy intake to match the energy expenditure, resulting in low energy availability that might have detrimental physiologic consequences and impair performance. Carbohydrates appear to be the primary fuel covering the total energy supply during match-play, and female elite football players should aim to consume sufficient carbohydrates to meet the requirements of their training program and to optimize the replenishment of muscle glycogen stores between training bouts and matches. However, several macro- and micronutrients are important for ensuring sufficient energy and nutrients for performance optimization and for overall health status in female elite football players. The inadequacy of macro-and micronutrients in the diet of these athletes may impair performance and training adaptations, and increase the risk of health disorders, compromising the player's professional career. In this topical review, we present knowledge and relevant nutritional recommendations for elite female football players for the benefit of sports nutritionists, dietitians, sports scientists, healthcare specialists, and applied researchers. We focus on dietary intake and cover the most pertinent topics in sports nutrition for the relevant physical demands in female elite football players as follows: energy intake, macronutrient and micronutrient requirements and optimal composition of the everyday diet, nutritional and hydration strategies to optimize performance and recovery, potential ergogenic effects of authorized relevant supplements, and future research considerations.

Relationship between Physical Fitness and Match Performance Parameters of Chile Women's National Football Team

The aim of this study was to analyze the relationships between the level of physical fitness and the physical performance parameters recorded by GPS in official FIFA matches of the Chilean women’s senior national football team in the period 2018–2020. Twenty-six female field players (age (mean ± SD) 26.8 ± 3.3 years, height 157.8 ± 21.5 cm, weight 58.9 ± 4.9 kg) participated in the study. Physical fitness variables were assessed: muscular strength, countermovement jump (CMJ), speed, agility and aerobic fitness. Physical performance variables were recorded by GPS in 26 official FIFA matches. The most notable associations with significant statistical significance (p < 0.001) were those observed between neuromuscular variables such as time to run 10 m (T10; r = −0.629) and jump (CMJ; r = 0.502) and the number of accelerations; aerobic fitness showed a highly significant relationship with meters run per minute (M/M; r = 0.589). The findings of this study provide evidence of how the level of physical fitness (neuromuscular and aerobic) relates to physical performance parameters recorded in official competitions.

Associations between maximal strength, sprint, and jump height and match physical performance in high-level female football players

Studies on females' decisive physical components to physical match-play performance are sparse and only emphasize endurance tests. Thus, the influence of maximal strength and power on physical performance during match-play is currently unknown. The aim of this study was to assess the association between one repetition maximum (1RM) half squat strength, 5-, 10-, and 15-m sprint times, countermovement jump (CMJ) height, and physical high-intensity match-play performance in high-level female football players. Thirty-seven female high-level football players completed 1-2 football matches with physical performance measured by local positioning tracking. Correlations were assessed between physical match-play performance variables (total distance covered, running distance, high-intensity running distance, sprinting distance as well as acceleration and deceleration counts, and peak speed) and laboratory tests (half squat 1RM, 15-m sprint, and CMJ). We found no correlation between 1RM and physical match-play performance. Further, 10-m- and 15-m sprint time (r = -0.56, r = -0.56, p < 0.001) and CMJ jump height (r = 0.50, p < 0.01) strongly correlated with peak match speed. Further, there was a moderate correlation between 15-m sprint time and ACC (r = -0.43, p < 0.05). 5-m sprint time did not correlate with physical match-play performance. Laboratory-based sprint and jump performance, but not maximal half squat strength, showed moderate to large correlations with high-intensity physical match-play performance measures in high-level female football players.

Ankle Injuries in Soccer Players: A Narrative Review

Soccer is one of the most popular sport, with many describing it as the "king of sports." In recent years, increased global participation in soccer has led to an inevitable increase in injury rates, especially in the lower extremities. Consequently, there is an increase in the epidemiology of soccer injuries, both in professionals and amateur athletes. The cause of an injury is multifactorial and depends on psychosocial, predisposing, intrinsic, and extrinsic factors. Also, contact with another player and non-contact injuries seem to be the most widespread mechanisms of injuries. The most common injuries recorded in soccer are ankle sprains and hamstrings injuries. More specifically, many studies have shown a correlation between the previous injury in lower extremities, weakness of abductors muscle, and psychosocial factors with the ankle sprain. Additionally, according to study results, injuries in adult men, adolescent men, and women during a match are higher than injuries during training. This narrative review aims to record the epidemiology of ankle injuries, risk factors, and the relationship between circadian rhythm, sleep, and injuries.

Effects of a Neuromuscular Warm-Up Program in Youth Female Soccer Players

The protective effects of different warm-up injury prevention routines in youth female soccer players have been demonstrated in the literature, however, there is a paucity of information regarding the effects that these kinds of programs have on soccer-specific physical performance variables. The purpose of this study was to assess the effectiveness of a 12-week neuromuscular warm-up program on physical performance in youth female soccer players. Players (age: 13.94 ± 0.82 years) were divided into two groups. One group performed a neuromuscular activation program (n = 21) twice per week whereas the other group (control, n = 17) continued with their habitual warm-up routine for the same duration. Both groups of players performed strength, jumping and balance tests before and after the intervention period. Substantially greater improvements were detected in the mean velocity for the squat (p < 0.001; Effect Size = 0.95) and the hip thrust (p < 0.001; Effect Size = 0.51) in the experimental group in comparison to the control group. In addition, after the intervention period players in the experimental group showed an increase in the jumping height in the unloaded double-leg and single-leg counter-movement jumps (p = 0.003-0.012; Effect Size = 0.42-0.46). The results of this study provide evidence that a 12-week neuromuscular warm-up program can be effective to improve different physical performance variables in youth female soccer players.

Physiological Characteristics of Female Soccer Players and Health and Performance Considerations: A Narrative Review

Female soccer has seen a substantial rise in participation, as well as increased financial support from governing bodies over the last decade. Thus, there is an onus on researchers and medical departments to develop a better understanding of the physical characteristics and demands, and the health and performance needs of female soccer players. In this review, we discuss the current research, as well as the knowledge gaps, of six major topics: physical demands, talent identification, body composition, injury risk and prevention, health and nutrition. Data on female talent identification are scarce, and future studies need to elucidate the influence of relative age and maturation selection across age groups. Regarding the physical demands, more research is needed on the pattern of high-intensity sprinting during matches and the contribution of soccer-specific movements. Injuries are not uncommon in female soccer players, but targeting intrinsically modifiable factors with injury prevention programmes can reduce injury rates. The anthropometric and physical characteristics of female players are heterogeneous and setting specific targets should be discouraged in youth and sub-elite players. Menstrual cycle phase may influence performance and injury risk; however, there are few studies in soccer players. Nutrition plays a critical role in health and performance and ensuring adequate energy intake remains a priority. Despite recent progress, there is considerably less research in female than male soccer players. Many gaps in our understanding of how best to develop and manage the health and performance of female soccer players remain.

Physical workload and fatigue pattern characterization in a top-class women's football national team: a case study of the 2019 FIFA Women's World Cup

BACKGROUND

With the growing scientific interest in women's football it is critical to understand the match demands and fatigue patterns during a top-class women's competition.

METHODS

Physical characteristics and performance of top-class women football matches during the 2019 FIFA Women's World Cup was investigated from data collected using global positioning system for 21 outfield players during the tournament.

RESULTS

Relative total distance (TD; m·min^-1) was moderately lower (P≤0.05, ES:0.6) in the final match (96.1±5.0 m·min^-1) compared to the first (104.1±5.9 m·min^-1) match. Performance in relative total high-speed running (THSR; m·min^-1) declined -27.5% (P≥0.05) throughout the tournament following peak performance in the third match (M3) (5.3±1.7 m·min^-1). Match performance between halves was reduced -25.4±0.13% (P≤0.05, ES:1.2-2.3) across all measures in M3. Relative high-intensity running (HIR; 25.9±3.5 m·min^-1) and THSR (9.8±1.5 m·min^-1) were greater (P≤0.05, ES:0.2-0.7) for forwards, while midfielders performed greater (P≤0.05, ES:0.6) relative total distance (102.0±5.5 m·min^-1), compared to central defenders (HIR: 16.1±3.7 m·min^-1; THSR: 3.1±1.6 m·min^-1; TD: 92.5±5.7 m·min^-1). Reductions in relative HIR between halves (-10.9%), within the first half (-31.0%), and the start and end of the match (-36.9%) were most pronounced for midfielders (P≤0.05, ES:0.6-2.3). Across all matches, relative THSR performance was reduced, with moderate to large differences (P≤0.001, ES: 0.7-0.8) observed between halves, within the first half, and throughout the match.

CONCLUSIONS

In conclusion, specific fatigue patterns observed within and between matches throughout the women's World Cup, may be influenced by playing positions, the rank of the opposition, as well as the stage of the tournament.

Muscle metabolism and impaired sprint performance in an elite women's football game

The present study examined skeletal muscle metabolism and changes in repeated sprint performance during match play for n = 20 competitive elite women outfield players. We obtained musculus vastus lateralis biopsies and blood samples before, after, and following intense periods in each half of a friendly match, along with 5 × 30-meter sprint tests and movement pattern analyses (10-Hz S5 Global Positioning System [GPS]). Muscle glycogen decreased by 39% and 42% after an intense period of the second half and after the match, respectively, compared to baseline (p < 0.05). Post-match, 80% type I fibers and 69% type II fibers were almost empty or completely empty of glycogen. Muscle lactate was higher (p < 0.05) after the intense period of the first half and post-match compared to baseline (14.3 ± 4.6 (±SEM) and 12.9 ± 5.7 vs. 6.4 ± 3.7 mmol/kg d.w.). Muscle phosphocreatine was reduced (p < 0.05) by 16% and 12%, respectively, after an intense period in the first and second half compared to baseline. Blood lactate and glucose increased during the match and peaked at 8.4 ± 2.0 and 7.9 ± 1.2 mmol/L, respectively. Mean 5 × 30 m sprint time declined by 3.2 ± 1.7 and 7.0 ± 2.1% after the first and second half, respectively, and 4.7 ± 1.6% (p < 0.05) after an intense period in the first half compared to baseline. In conclusion, match play in elite female football players resulted in marked glycogen depletion in both fiber types, which may explain fatigue at the end of a match. Repeated sprint ability was impaired after intense periods in the first half and after both halves, which may be associated with the observed muscle metabolite perturbations.

Relationships between Fitness Status and Match Running Performance in Adult Women Soccer Players: A Cohort Study

Background and Objectives: The aim of this study was twofold: (i) to analyze the relationships between fitness status (repeated-sprint ability (RSA), aerobic performance, vertical height jump, and hip adductor and abductor strength) and match running performance in adult women soccer players and (ii) to explain variations in standardized total distance, HSR, and sprinting distances based on players' fitness status. Materials and Methods: The study followed a cohort design. Twenty-two Portuguese women soccer players competing at the first-league level were monitored for 22 weeks. These players were tested three times during the cohort period. The measured parameters included isometric strength (hip adductor and abductor), vertical jump (squat and countermovement jump), linear sprint (10 and 30 m), change-of-direction (COD), repeated sprints (6 × 35 m), and intermittent endurance (Yo-Yo intermittent recovery test level 1). Data were also collected for several match running performance indicators (total distance covered and distance at different speed zones, accelerations/decelerations, maximum sprinting speed, and number of sprints) in 10 matches during the cohort. Results: Maximal linear sprint bouts presented large to very large correlations with explosive match-play actions (accelerations, decelerations, and sprint occurrences; r = -0.80 to -0.61). In addition, jump modalities and COD ability significantly predicted, respectively, in-game high-intensity accelerations (r = 0.69 to 0.75; R2 = 25%) and decelerations (r = -0.78 to -0.50; R2 = 23-24%). Furthermore, COD had significant explanatory power related to match running performance variance regardless of whether the testing and match performance outcomes were computed a few or several days apart. Conclusion: The present investigation can help conditioning professionals working with senior women soccer players to prescribe effective fitness tests to improve their forecasts of locomotor performance.

The Efficacy of Heat Acclimatization Pre-World Cup in Female Soccer Players

The efficacy of a 14-day field-based heat acclimatization (HA) training camp in 16 international female soccer players was investigated over three phases: phase 1: 8 days moderate HA (22. 1°C); phase 2: 6 days high HA (34.5°C); and phase 3: 11 days of post-HA (18.2°C), with heart rate (HR), training load, core temp (T_c), and perceptual ratings recorded throughout. The changes from baseline (day−16) in (i) plasma volume (PV), (ii) HR during a submaximal running test (HRex) and HR recovery (HRR), and (iii) pre-to-post phase 2 (days 8–13) in a 4v4 small-sided soccer game (4V4SSG) performance were assessed. Due to high variability, PV non-significantly increased by 7.4% ± 3.6% [standardized effect (SE) = 0.63; p = 0.130] from the start of phase 1 to the end of phase 2. Resting T_c dropped significantly [p < 0.001 by −0.47 ± 0.29°C (SE = −2.45)], from day 1 to day 14. Submaximal running HRR increased over phase 2 (HRR; SE = 0.53) after having decreased significantly from baseline (p = 0.03). While not significant (p > 0.05), the greatest HR improvements from baseline were delayed, occurring 11 days into phase 3 (HRex, SE = −0.42; HRR, SE = 0.37). The 4v4SSG revealed a moderate reduction in HRex (SE = −0.32; p = 0.007) and a large increase in HRR (SE = 1.27; p < 0.001) from pre-to-post phase 2. Field-based HA can induce physiological changes beneficial to soccer performance in temperate and hot conditions in elite females, and the submaximal running test appears to show HRex responses induced by HA up to 2 weeks following heat exposure.

Distance and Intensity Profiles in Division I Women's Soccer Matches across a Competitive Season

Women’s participation in soccer has increased rapidly. The purpose of this study was to evaluate the physiological demands imposed on women’s NCAA Division I soccer players across a season according to speed, total distance traveled, and numbers of sprints measured via GPS (Polar Team Pro^®). Eighteen athletes (19.2 ± 1.1 years, 50.5 ± 6.5 mL/kg/min and 23.4 ± 3.6% fat) participated in this study. The analysis was obtained through 13 official matches. Speed zones were defined as Zone 1 (1.0 to 5.99 km·h⁻¹), Zone 2 (6.0 to 10.99 km·h⁻¹), Zone 3 (11.0 to 15.49 km·h⁻¹), Zone 4 (15.5 to 19.9 km·h⁻¹) and Zone 5 (sprint > 20 km·h⁻¹), with Zones 4–5 considered as high intensity running. Individual differences in playing time and total distance were highly variable due to substitutions. Average distance traveled per game in quartiles was 3.9 km, 5.6 km and 7.4 km in the 25th, 50th, and 75th quartiles, respectively. Relative to playing time, players travelled an average of 113.64 ± 17.12 m/min (range: 93.7 to 143.5 m/min) and ran one sprint every 4.12 ± 2.06 min. When distance was summated and analyzed for the entire team, significant difference between halves was found for speed Zones 2, 3 and 4, with greater values found in the first half. Total distance, high intensity running and sprint distance were significantly less than previously recorded in professional players. These findings suggest that coaches should consider the unique physiological demands and recovery opportunities present in NCAA play when constructing practices and conditioning programs.

Exploring the Determinants of Repeated-Sprint Ability in Adult Women Soccer Players

This study aimed to explore the main determinants of repeated-sprint ability (RSA) in women soccer players considering aerobic capacity, sprinting performance, change-of-direction, vertical height jump, and hip adductor/abductor isometric strength. Twenty-two women soccer players from the same team participating in the first Portuguese league were observed. Fitness assessments were performed three times during a 22-week cohort period. The following assessments were made: (i) hip abductor and adductor strength, (ii) squat and countermovement jump (height), (iii) change-of-direction test, (iv) linear sprinting at 10- and 30-m, (v) RSA test, and (vi) Yo-Yo intermittent recovery test level 1. Positive moderate correlations were found between peak minimum RSA and adductor and abductor strength (r = 0.51, p < 0.02 and r = 0.54, p < 0.01, respectively). Positive moderate correlations were also found between peak maximum RSA and adductor and abductor strength (r = 0.55, p < 0.02 and r = 0.46, p < 0.01, respectively). Lastly, a moderate negative correlation was found between fatigue index in RSA and YYIR1 test performance (r = -0.62, p < 0.004). In conclusion, abductor and adductor isometric strength-based coadjutant training programs, together with a high degree of aerobic endurance, may be suitable for inducing RSA in female soccer players.

Varying Demands and Quality of Play Between In-Conference and Out-of-Conference Games in Division I Collegiate Women's Soccer

Bozzini, BN, McFadden, BA, Walker, AJ, and Arent, SM. Varying demands and quality of play between in-conference and out-of-conference games in Division I collegiate women's soccer. J Strength Cond Res 34(12): 3364-3368, 2020-The purpose of this study was to assess differences in physical workloads, physiological responses, and performance variables between in-conference (IC) and out-of-conference (OC) games during a collegiate women's soccer season. Female field players (N = 11), who played a minimum of 45 minutes for >50% of games, were evaluated using an integrative GPS and HR monitoring system to determine training load (TL), exercise energy expenditure (EEE), total distance covered (DIS), sprints, time spent in HR zones 4 and 5 (HRZ4 = 80-89% HRmax; HRZ5 = 90-100% HRmax), and distance covered in speed zones 4 and 5 (DISZ4 = 15.0-19.9 km·h; DISZ5 = ≥20 km·h). In addition, percent passing accuracy (PA%), dribbling success (DS%), tackling success (TS%), and challenges won (CW%) were generated for all games. Workload data were analyzed as a rate per minute playing time (PT) per game to account for differences in game duration and PT between OC (n = 7) and IC games (n = 11). Repeated-measures multivariate analyses of variance with univariate follow-ups and effect sizes (Hedges' g) were conducted to compare conditions (OC vs. CON) (p < 0.05). There were significantly greater TL, DIS, EEE, and HRZ5 per minute PT in OC versus IC games (Hedges' g: TL = 0.48; DIS = 0.20, EEE = 0.55; HRZ5 = 0.83; p < 0.05). Further analysis found significant differences in first half play favoring OC games (p < 0.05), but not second half play (p > 0.05). Based on these findings, OC games seem to be more demanding compared to IC, particularly during first half play. Emphasis should be placed on tailoring TL to the accumulating in-season demands through athlete-monitoring technology to prevent declines in performance in the latter half of the season.

Effects of Plyometric Jump Training on Jump and Sprint Performance in Young Male Soccer Players: A Systematic Review and Meta-analysis

BACKGROUND

Even from a young age, modern soccer requires high levels of physical fitness development, particularly jumping and sprinting. Plyometric jump training (PJT), combined with young athletes' regular soccer sessions, has the potential to improve jumping and sprinting. However, studies exploring the effects of PJT are generally limited by small sample sizes. This problem of underpowered studies may, thus, be resolved by pooling study results in a meta-analysis.

OBJECTIVE

The objective of this systematic review with meta-analysis (SRMA) was to assess the effects of plyometric jump training (PJT) on jumping and sprinting among young male soccer players.

METHODS

The SRMA included peer-reviewed articles that incorporated PJT in healthy players (i.e., < 23 years of age), a control group, and a measure of jumping or sprinting. Means and standard deviations of outcomes were converted to Hedges' g effect sizes (ES), using the inverse variance random-effects model. Moderator analyses were conducted for PJT duration, frequency, total number of sessions, participants' chronological age, and FIFA age categories (i.e., U-17 vs. U-20 vs. U-23). A multivariate random-effects meta-regression was also conducted.

RESULTS

Thirty-three studies were included, comprising 1499 participants. PJT improved vertical jump tests (ES = 0.60-0.98; all p < 0.01) and linear sprint performance (ES = 0.60-0.98; p < 0.03). Interventions of > 7 weeks and > 14 PJT sessions induced greater effects compared to PJT with ≤ 7 weeks and ≤ 14 total sessions on 10-m sprint performance (between group p = 0.038).

CONCLUSION

PJT is effective in improving jumping and sprinting performance among young male soccer players. Greater 10-m linear sprinting improvements were noted after interventions > 7-week duration and > 14 sessions, suggesting a greater return from exposure to longer PJT interventions, partially in support for the adoption of a long-term approach to athletic development in young athletes. However, with reference to the findings of the meta-regression, and those from the remaining subgroup and single factors analysis, a robust confirmation regarding the moderator role of participant's age or PJT configuration effects on young soccer player's fitness qualities needed.

Physical performance and loading for six playing positions in elite female football: full-game, end-game, and peak periods

The present study investigated the position-specific match demands and heart rate response of female elite footballers, with special focus on the full-game, end-game, and peak-intensity periods. In total, 217 match observations were performed in 94 players from all eight teams of the best Danish Women's League, that is, goalkeepers (GK, n = 10), central defenders (CD, n = 23), full-backs (FB, n = 18), central midfielders (CM, n = 28), external midfielders (EM, n = 18), and forwards (FW, n = 11). Positional data (GPS; 10 Hz Polar Team Pro) and HR responses were collected. HR_mean and HR_peak were 87%-89% and 98%-99% of HR_max , for outfield players, with no positional differences. CM, EM, and FB covered 8%-14% greater (P < .001) match distances than CD. EM, FW, FB, and CM performed 40%-64% more (P < .05) high-speed running and 41%-95% more (P < .01) very-high-speed running (VHSR) than CD. From the first to the last 15-minute period, total distance, except for FW, number of VHSR, except FB, peak speed and sum of accelerations and sum of decelerations decreased (P < .05) for all outfield positions. In the most intense 5-minute period, EM, FB, and CM performed 25%-34% more (P < .01) HSR than CD, whereas EM, FW, and FB performed 36%-49% more (P < .01) VHSR than CD. In conclusion, competitive elite female matches impose high physical demands on all outfield playing positions, with high aerobic loading throughout matches and marked declines in high-speed running and intense accelerations and decelerations toward the end of games. Overall physical match demands are much lower for central defenders than for the other outfield playing positions, albeit this difference is minimized in peak-intensity periods.

Positional Match Running Performance and Performance Profiles of Elite Female Field Hockey

PURPOSE

To determine if there is a link between the demands of competitive game activity and performance profiles of elite female field hockey players.

METHODS

Global positioning systems (GPS) were used to quantify running performance of elite female field hockey players (N = 20) during 26 competitive games. Performance profiles were assessed at 2 time points (preseason and midseason) for 2 competitive seasons. A battery of anthropometric and performance field-based tests (30-15 intermittent fitness test, incremental run test, 10-30-m speed test, T test, and vertical jump test) were used to determine the performance profiles of the players.

RESULTS

Players covered a mean total distance of 5384 (835) m, of which 19% was spent at high intensities (zone 5: 796 [221] m; zone 6: 274 [105] m). Forwards covered the lowest mean total distance (estimated marginal means 4586 m; 95% confidence interval, 4275-4897), whereas work rate was higher in forwards compared with midfielders (P = .006, d = 0.43) and central defenders (P = .001, d = 1.41). Players showed an improvement in body composition and anaerobic performance from preseason to midseason. Aerobic performance capacity (maximal oxygen uptake and speed at the 4-mM lactate threshold) was positively correlated with high-intensity activities.

CONCLUSIONS

There is a clear relationship between running performance and aerobic performance profiles in elite female hockey players. These results highlight the importance of a well-developed aerobic performance capacity in order to maintain a high performance level during hockey games.

External and internal loads during the competitive season in professional female soccer players according to their playing position: differences between training and competition

The aim of this study was to compare external (EL) and internal loads (IL) during training sessions compared to official matches between elite female soccer players according to their playing position.Training and match data were obtained during the 2017/18 season from eighteen players (age: 26.5±5.7 years; height: 164.4±5.3 cm; body mass: 58.56±5.58 kg) from a first Division Spanish team. The EL (total distance covered; high-speed running distance; number of accelerations and decelerations) was assessed with a Global Positioning System (GPS) and triaxial accelerometer. The IL was assessed with ratings of perceived exertion (RPE; and session-RPE).The EL and the IL from official matches were higher compared to training sessions (p<0.05; effect size [ES]:0.6-5.4). In matches, the EL was greater in Attackers (AT) and Central Midfielders (CM) versus Central Backs (p<0.05; ES:0.21-1.74). During training sessions, the EL was similar between playing positions (p>0.05; ES:0.03-0.87). The EL and the IL are greater in matches compared to training sessions, with greater match-related EL in AT and CM players. Current results may help practitioners to better understand and modulate training session's loads according to playing position, potentially contributing to their performance readiness and injury risk reduction.

Injury Incidence Across the Menstrual Cycle in International Footballers

Objectives: This study aimed to assess how menstrual cycle phase and extended menstrual cycle length influence the incidence of injuries in international footballers.

Methods: Over a 4-year period, injuries from England international footballers at training camps or matches were recorded, alongside self-reported information on menstrual cycle characteristics at the point of injury. Injuries in eumenorrheic players were categorized into early follicular, late follicular, or luteal phase. Frequencies were also compared between injuries recorded during the typical cycle and those that occurred after the cycle would be expected to have finished. Injury incidence rates (per 1,000 person days) and injury incidence rate ratios were calculated for each phase for all injuries and injuries stratified by type.

Results: One hundred fifty-six injuries from 113 players were eligible for analysis. Injury incidence rates per 1,000 person-days were 31.9 in the follicular, 46.8 in the late follicular, and 35.4 in the luteal phase, resulting in injury incidence rate ratios of 1.47 (Late follicular:Follicular), 1.11 (Luteal:Follicular), and 0.76 (Luteal:Late follicular). Injury incident rate ratios showed that muscle and tendon injury rates were 88% greater in the late follicular phase compared to the follicular phase, with muscle rupture/tear/strain/cramps and tendon injuries/ruptures occurring over twice as often during the late follicular phase compared to other phases 20% of injuries were reported as occurring when athletes were “overdue” menses.

Conclusion: Muscle and tendon injuries occurred almost twice as often in the late follicular phase compared to the early follicular or luteal phase. Injury risk may be elevated in typically eumenorrheic women in the days after their next menstruation was expected to start.

Effects of Short-Term Plyometric Training on Agility, Jump and Repeated Sprint Performance in Female Soccer Players

The aim of the study was to determine the effects of short-term (4 weeks, twice a week: 8 sessions) plyometric training on agility, jump, and repeated sprint performance in female soccer players. The study comprised 17 females performing this sports discipline. The players were randomly divided into two groups: with plyometric training (PLY) and the control (CON). All players followed the same training program, but the PLY group also performed plyometric exercises. Tests used to evaluate physical performance were carried out immediately before and after PLY. After implementing the short PLY training, significant improvement in jump performance (squat jump: p = 0.04, ES = 0.48, countermovement jump: p = 0.009, ES = 0.42) and agility (p = 0.003, ES = 0.7) was noted in the PLY group. In the CON group, no significant (p > 0.05) changes in physical performance were observed. In contrast, PLY did not improve repeated sprint performance (p > 0.05) among female soccer players. In our research, it was shown that PLY can also be effective when performed for only 4 weeks instead of the 6–12 weeks typically applied.

Growth and Maturity Status of Female Soccer Players: A Narrative Review

Reported mean ages, heights and weights of female soccer players aged <19 years in 161 studies spanning the years 1992-2020 were extracted from the literature or calculated from data available to the authors; 35 studies spanning the years 1981-2020 also included an indicator of biological maturation. Heights and weights were plotted relative to U.S. reference data. Preece-Baines Model 1 was fitted to moving averages to estimate ages at peak velocity. Maturity indicators included skeletal age, pubertal status, age at menarche, percentage of predicted adult height and predicted maturity offset. Heights and weights showed negligible secular variation across the time interval. Heights were slightly above or approximated the reference medians through 14 years old and then varied between the medians and 75th percentiles through 18 years old. Weights were above the reference medians from 9 to 18 years old. Mean ages at menarche ranged from 12.7 to 13.0 years. The trend in heights and weights suggested the persistence and/or selection of taller and heavier players during adolescence, while estimated age at peak height velocity (PHV) and ages at menarche were within the range of mean ages in European and North American samples. Data for skeletal and sexual maturity status were limited; predicted maturity offset increased linearly with mean ages and heights at prediction.

Injury Profile in Women's Football: A Systematic Review and Meta-Analysis

BACKGROUND

Football is the most popular sport among women; however, little is known about the injury profile in this population. This information would help design tailored injury risk mitigation strategies that may make football safer for women.

OBJECTIVE

The aim of this study was to perform a systematic review and meta-analysis of epidemiological data of injuries in women´s football.

METHODS

A systematic review following PRISMA guidelines was performed up to January 2020 in PubMed, Web of Science, Sportdiscus and the Cochrane Library databases. Twenty-two studies reporting the incidence of injuries in women football were analysed. Two reviewers independently extracted data (intraclass correlation coefficient [ICC] for inter-reviewer reliability = 0.87) and assessed study quality using the STROBE statement, GRADE approach, Newcastle Ottawa Scale and Downs and Black assessment tools. Studies were combined in pooled analyses (injury incidence and injury proportion) using a Poisson random effects regression model.

RESULTS

The overall incidence of injuries in female football players was 6.1 injuries/1000 h of exposure. Match injury incidence (19.2 injuries/1000 h of exposure) was almost six times higher than training injury incidence rate (3.5 injuries/1000 h of exposure). Lower extremity injuries had the highest incidence rates (4.8 injuries/1000 h of exposure). The most common types of injuries were muscle/tendon (1.8 injuries/1000 h of exposure) and joint (non-bone) and ligament (1.5 injuries/1000 h of exposure), which were frequently associated with traumatic incidents. Slight/minimal injuries (1-3 days of time loss) were the most common. The incidence rate of injuries during matches in the top five world ranking leagues was higher than the rest of the leagues (19.3 vs 10.7 injuries/1000 h of exposure, respectively). The weighted injury proportion was 1.1 (95% confidence interval = 0.6-1.7) whereby on average players sustained more than one injury per season.

CONCLUSIONS

Female football players are exposed to a substantial risk of sustaining injuries, especially during matches that require the highest level of performance. To markedly reduce overall injury burden, efforts should focus on introducing and evaluating preventative measures that target match specific dynamics to make football players more capable of responding to the challenges that they have to deal with during match play.

REGISTRATION

This systematic review was registered in the PROSPERO international prospective register of systematic reviews (ID = CRD42019118152).

Physical Characteristics of Elite Youth Female Soccer Players Characterized by Maturity Status

Emmonds, S, Scantlebury, S, Murray, E, Turner, L, Robsinon, C, and Jones, B. Physical characteristics of elite youth female soccer players characterized by maturity status. J Strength Cond Res 34(8): 2321-2328, 2020-The purpose of this study was to investigate the influence of maturity status on the physical characteristics of youth female soccer players. One hundred fifty-seven players from 3 elite soccer academies in England completed assessments of anthropometry, strength (isometric midthigh pull), lower-body power (countermovement jump [CMJ]), aerobic capacity (Yo-Yo intermittent recovery test level 1), change of direction (CoD: 505-left/right), and speed (10 and 30 m). Each player was classified into 1 of 6 maturity groups based on their estimated years from peak height velocity (YPHV). Magnitude-based inferences were used to assess for the practical significance between consecutive groups. Speed, CoD time, CMJ, and aerobic capacity were all possibly most likely better in more mature players. However, there was a likely difference in relative peak force between maturity groups -0.5 YPHV (27.13 ± 4.24 N·Kg) and 0.5 YPHV (24.62 ± 3.70 N·Kg), which was associated with a likely difference in 10-m sprint time (-0.5 YPHV: 2.00 ± 0.12 vs. 0.5 YPHV 2.08 ± 0.16 seconds) and unclear changes in CMJ and CoD time. Findings provide novel comparative data for this cohort relative to maturity status and can be used by strength and conditioning coaches to inform the design of training programs for youth female soccer players. Strength and conditioning coaches should be aware that youth female soccer players may experience a decrease in relative strength around peak height velocity, which may impact upon the speed, CoD time, and CMJ of players.

Sex Differences in Physical Capacities of German Bundesliga Soccer Players

Cardoso de Araújo, M, Baumgart, C, Jansen, CT, Freiwald, J, and Hoppe, MW. Sex differences in physical capacities of German Bundesliga soccer players. J Strength Cond Res 34(8): 2329-2337, 2020-Sex differences in physical capacities of elite soccer players have received limited attention. Therefore, this study investigated sex differences in linear and nonlinear sprint, squat and countermovement jump, core endurance, as well as incremental and intermittent endurance capacities in German Bundesliga soccer players. A total of 76 field players (29 women) were tested for the mentioned anaerobic- and aerobic-related physical capacities in a noninterventional cross-sectional design. The largest sex differences were evident in the explosive- and intermittent endurance-related capacities, with women presenting largely to extremely largely lower values in sprints, jumps, and intermittent endurance (effect size [ES] ≥1.77, p < 0.01). The differences in the total core endurance, running velocity at 2 and 4 mmol·L capillary blood lactate (v2 and v4), maximal heart rate (HR) (ES ≤ 0.72, p ≥ 0.06), and distance covered during the incremental endurance test (ES = 1.09, p = 0.01) were trivially to moderately lower for women. However, women had small to moderately higher ventral and dorsal core endurance (ES ≤ 0.69, p ≥ 0.07) and largely higher relative HR at the lactate thresholds (ES ≥ 1.54, p < 0.01). The individual data of female players showed more variability. Some individual data of women overlapped those of men, most evident in the total core endurance and v2. The findings indicate that there are sex differences in physical capacities according to the underlying amount of anaerobic and aerobic energy supply. The sex specificities should be considered to optimize training and testing procedures for soccer players.

Physical performance development in a female national team soccer program

OBJECTIVES

Significant resources are invested in maximizing player performance without extensive knowledge of the athletic progression of elite female soccer players during their career. The aim of the current study was therefore to investigate the change in physical performance characteristics in 12- to 34-year-old female soccer players in a national team program.

DESIGN

Mixed-longitudinal study.

METHODS

Physical performance was assessed across five years and 657 testing occasions (n = 143) using anthropometrics, 40 m sprint (10 m split), broad jump, countermovement jump, squat jump, and 30-15 intermittent fitness test (IFT).

RESULTS

Using a Gaussian mixture model, Youth and Senior groups were bifurcated at approximately 23 years old. Subsequent linear mixed models for each group and variable identified significant improvements in the Youth group in maximal speed (30-40 m split), broad jump, countermovement jump, and final velocity_30-15IFT (p ≤ 0.002), and a decrease in squat jump height with increasing age (p = 0.04). The Senior group recorded slower 10 m sprint time and a decrease in squat jump height with increasing age (p < 0.001). Body mass increased from 12 to 34 years old (Youth and Senior: p ≤ 0.001). The Youth group significantly differed in the rate of change compared to the Senior group in body mass, 10 m sprint time, countermovement jump, squat jump, and final velocity_30-15IFT (p ≤ 0.001).

CONCLUSIONS

This information can be used to identify average rates of physical performance improvement and decay to help guide optimal physical training and maximize the longevity of a female soccer players' career.

Sustained Passing Performance of Elite and Subelite Female Soccer Players Following a Female Match-Specific Exercise Protocol

PURPOSE

This study examined the maintenance of passing performance following soccer-specific high-intensity intermittent exercise in elite (n = 9) and subelite (n = 11) Western Australian female soccer players (19.5 [2.5] y).

METHODS

A total of 20 participants completed the Loughborough Soccer Passing Test (LSPT) prior to, during, and following 90 minutes of a modified, female-specific, individualized exercise protocol (Loughborough Intermittent Shuttle Test [LIST]) to simulate 2 halves of a soccer match. Performance in the LSPT was calculated by adding "raw time" to the accumulated "penalty time" for each test.

RESULTS

Elite players recorded greater distances (t58 = 4.671, P < .001, effect size [ES] = 1.21) and higher derived VO2max values (t58 = 4.715, P < .001, ES = 1.20) for the LIST exercise protocol over the subelite players. The total performance times for each LSPT were longer in the subelites in comparison with the elites, with a very large ES difference seen in post-LIST1 (t18 = -6.64, P < .001, ES = 2.99) and post-LIST2 (t18 = -9.143, P < .001, ES = 4.12). No between-groups differences were identified for "raw time" at any time point. Hence, all reported LSPT performance differences are attributed to "penalty time."

CONCLUSION

These data suggest that elite players can sustain their passing performance more efficiently throughout match play that can subelite female soccer players. These findings may contribute to future talent-identification testing by helping to distinguish between elite- and subelite-level players through sustained passing performance. Coaches may also use this information to better inform best-practice training methods through modification of male soccer-specific high-intensity intermittent exercise to a female cohort.

Performance on sprint, agility and jump tests have moderate to strong correlations in youth football players but performance tests are weakly correlated to neuromuscular control tests

PURPOSE

This study aimed at evaluating the correlation between seven different performance tests and two neuromuscular control tests in youth football players and to evaluate the influence of sex and age groups on test results.

METHODS

One-hundred and fifteen football players (66 boys, 49 girls) mean age 14 ± 0.7 (range 13-16) years from youth teams were tested at the start of the second half of the competitive season. A test battery including agility t-test, 505 agility test, single-leg hop for distance test, side-hop test, countermovement jump test, 10-m sprint test, 20-m sprint test, tuck jump assessment (TJA) and drop vertical jump (DVJ) was completed.

RESULTS

Correlations between the seven different performance tests of agility, jump and sprint ability were generally moderate to strong (r = 0.534-0.971). DVJ did not correlate with the performance tests (rho = 0.004 to  -  0.101) or with TJA total score (rho = 0.127). There were weak to moderate correlations between TJA total score and the performance tests (r =  - 0.323-0.523). Boys performed better than girls in all performance tests (p < 0.001) and in TJA total score (p = 0.002). In boys, older players performed better than younger players in the majority of the tests, while there was no clear age influence among girls.

CONCLUSION

Sprint performance was moderately to strongly correlated with agility and jump performance, and performance tests were weakly to moderately correlated to TJA, while DVJ did not correlate with the other tests. Boys performed better than girls on performance tests and TJA. An age effect on performance was evident in boys but not in girls.

LEVEL OF EVIDENCE

Level IV TRIAL REGISTRATION: Clinical Trials gov identifier: NCT03251404.

COVID-19-Related Restrictions and Quarantine COVID-19: Effects on Cardiovascular and Yo-Yo Test Performance in Professional Soccer Players

The present study aimed to verify the quarantine's effects during a serious viral outbreak on the cardiovascular and performance associated with the Yo-Yo test in a sample of professional soccer players. 20 high-level soccer players (n = 20; age: 26 ± 4 years-old; weight: 76.85 ± 6.7 kg; height: 179 ± 6 cm) participated in this study. The intermittent Yo-Yo test was performed pre- and post- COVID-19 quarantine in a random order. During each test, the soccer players' running performance outcomes were monitored using a portable 5-Hz GPS with a 100 Hz accelerometer and a paired t-test was conducted at a p-value of ≤ 0.05. The main results demonstrated significant differences between pre- versus post-COVID-19 quarantine in the following variables: relative distance (161.7 ± 5.9 > 141.1 ± 33.8 m/min), maximal speed (18.7 ± 0.9 > 18.2 ± 0.6 km/h), acceleration (60 ± 20 frequency > 52 ± 16 frequency), deceleration (34 ± 13 frequency > 27 ± 6 frequency), sprints > 19 km/h [0.8 (0.2;3)% >0.5 (0;0.5)%], and in high intensity running distance [16.48 (2.68;41.64)m > 0.827 (0.164;3.0)m]. We concluded that COVID-19-related restrictions and quarantine COVID-19 demonstrated adverse effects on professional soccer players' Yo-Yo tests performance.

The effect of music on short-term exercise performance during the different menstrual cycle phases in female handball players

The present study aimed to evaluate the effect of music on short-term exercise performance during the different menstrual cycle phases (MCP). In different MCP (i.e. menstrual phase (MP), luteal phase (LP), follicular phase (FP)) and in a randomized order, fourteen female handball players aged between 21-24 years performed during music (fast-tempo, 140 bpm) and no-music conditions the following tests: squat jump (SJ) test, countermovement jump (CMJ), agility T-test (TT), and repeated sprint ability (RSA). The profile of mood states (POMS) questionnaire was completed in the different MCP. The rating of perceived exertion was recorded at the end of TT and RSA. MCP does not affect the SJ, CMJ, TT and RSA performance. However, anxiety, anger, and confusion were higher in MP compared to LP and FP. Music enhances the SJ performance during the different MCP. However, the music improved the SJ performance (the first test) only following warm-up in all MCP. In conclusion, listening to music during warm-up could be beneficial for short-term exercise performance in all MCP, but the potential effect of the music on physical performance vanishes over time.

Effects of Plyometric Jump Training in Female Soccer Player's Physical Fitness: A Systematic Review with Meta-Analysis

We aimed to assess the effects of plyometric jump training (PJT) on female soccer player’s physical fitness. To this aim, a systematic review with meta-analysis (SRMA) was conducted. The electronic databases PubMed, MEDLINE, Web of Science, and SCOPUS were used. To qualify for inclusion, peer-reviewed studies must have included (i) a PJT programme of ≥2 weeks, (ii) healthy athletes, (iii) a control group, and (iv) physical fitness outcomes (e.g., jump; sprint). Studies were excluded if (i) they incorporated injuried female soccer players, (ii) did not involve PJT or an active control group, (iv) lack of baseline and/or follow-up data. Data was meta-analyzed using the inverse variance random-effects model. Ten moderate-to-high quality studies were included in the analyses, comprising 13 training groups (n = 140) and 10 control groups (n = 110). Small to large (ES = 0.60–2.24; p = 0.040 to <0.001) effects were noted for countermovement jump, drop jump, kicking performance, linear sprint, change of direction speed, and endurance. The moderator analyses (i.e., PJT duration, age groups, competitive level, and soccer experience) revealed no significant differences between groups. In conclusion, PJT may improve the physical fitness of female soccer players. Such improvements might be expected after PJT interventions with six or more weeks of duration, and in players with different chronological ages, competitive levels and soccer experience.

Short-term effects of maximal dynamic exercise on flow-mediated dilation in professional female soccer players

BACKGROUND

Endothelial function assessment may provide important insights into the cardiovascular function and long-term effects of exercise training. Many studies have investigated the possible negative effects on cardiovascular function due to extreme athletic performance, leading to undesirable effects. The purposes of this study were to investigate the acute effects of maximal intensity exercise on endothelium-dependent vasodilation, and to understand the patterns of flow-mediated dilation (FMD) change following maximal exercise in elite female athletes with a high-volume training history.

METHODS

Twenty-six elite female soccer players (mean age, 22±4 years; BMI, 21±2 kg/m²; VO<inf>2max</inf>, 41±4 mL/kg/min) were evaluated. Brachial artery FMD was determined using high-resolution ultrasound at rest, and after 15 and 60 min of maximal cardiopulmonary exercise (CPX) testing on a treadmill. Flow velocity was measured at baseline and during reactive hyperemia at the same periods.

RESULTS

Rest FMD was 12.4±5.5%. Peak diameter in response to reactive hyperemia was augmented after 15 min of CPX (3.5±0.4 vs. 3.6±0.4 mm, P<0.05), returning to resting values after 60 min. However, %FMD did not change among time periods. There were two characteristic patterns of FMD response following CPX. Compared to FMD at rest, half of the subjects responded with an increased FMD following maximum exercise (10.5±6.1 vs. 17.8±7.5%, P<0.05). The other subjects demonstrated a reduced FMD response following maximum exercise (14.2±4.3 vs. 10.9±3.2%, P<0.01).

CONCLUSIONS

These results indicate that elite female soccer players presented robust brachial artery FMD at rest, with a heterogeneous FMD response to acute exercise with a 50% FMD improvement rate.

Technical determinants of success in professional women's soccer: A wider range of variables reveals new insights

Knowledge of optimal technical performance is used to determine match strategy and the design of training programs. Previous studies in men’s soccer have identified certain technical characteristics that are related to success. These studies however, have relative limited sample sizes or limited ranges of performance indicators, which may have limited the analytical approaches that were used. Research in women’s soccer and our understanding of optimal technical performance, is even more limited (n = 3). Therefore, the aim of this study was to identify technical determinants of match outcome in the women’s game and to compare analytical approaches using a large sample size (n = 1390 team performances) and range of variables (n = 450). Three different analytical approaches (i.e. combinations of technical performance variables) were used, a data-driven approach, a rational approach and an approach based on the literature in men’s soccer. Match outcome was modelled using variables from each analytical approach, using generalised linear modelling and decision trees. It was found that the rational and data-driven approaches outperformed the literature-driven approach in predicting match outcome. The strongest determinants of match outcome were; scoring first, intentional assists relative to the opponent, the percentage of shots on goal saved by the goalkeeper relative to the opponent, shots on goal relative to the opponent and the percentage of duels that are successful. Moreover the rational and data-driven approach achieved higher prediction accuracies than comparable studies about men’s soccer.

Environmental Conditions, Preseason Fitness Levels, and Game Workload: Analysis of a Female NCAA DI National Championship Soccer Season

Benjamin, CL, Hosokawa, Y, Curtis, RM, Schaefer, DA, Bergin, RT, Abegg, MR, and Casa, DJ. Environmental conditions, preseason fitness levels, and game workload: Analysis of a female NCAA DI National Championship Soccer Season. J Strength Cond Res 34(4): 988-994, 2020-The purpose of this study was to determine the independent and combined moderating effect of aerobic fitness and environmental conditions on physical workloads during collegiate female soccer matches. Nineteen National Collegiate Athletic Association female soccer athletes were included in this study (mean ± SD: age, 20.6 ± 1.4 years; height, 169 ± 6.1 cm; body mass 64.7 ± 5.3 kg). Maximal oxygen consumption (V[Combining Dot Above]O2max) was estimated from the yo-yo intermittent recovery test before preseason training and wet-bulb globe temperature (WBGT) was recorded onsite for home matches and at the nearest weather station for away matches. Relative distance (TD), relative high-speed running distance (%HSD), and relative high metabolic load (%HML) performance were collected during each match using a global positioning system unit (Viper Pod; STATSports, Chicago, IL). Statistically significant differences were observed in TD between LOW WBGT and MOD WBGT (mean difference [MD] = 7.08 m·min; effect size [ES] = 0.54; p < 0.001), in %HSD between LOW WBGT and MOD WBGT (MD = 1.97%; ES = 0.64; p = 0.01) and between LOW WBGT and HIGH WBGT (MD = 2.71%; ES = 1.01; p < 0.001), and in %HML between LOW WBGT and MOD WBGT (MD = 1.24%; ES = 0.56; p < 0.001) and between LOW WBGT and HIGH WBGT (MD = 1.55%; ES = 0.78; p = 0.01). There was a significant interaction between WBGT and V[Combining Dot Above]O2max for %HSD (p = 0.03). These findings demonstrate that physical performance metrics were affected by increased WBGT. In addition, aerobic fitness seemed to moderate the effect of increasing WBGT on %HSD, meaning maximizing aerobic capacity is important for optimizing running performance in the heat. Coaches and sports medicine staff could alter training time and session length based on environmental conditions as well as potentially use aggressive cooling strategies to mitigate the imposed heat stress and decrements in physical performance.

Effects of Combined Strength and Power Training on Physical Performance and Interlimb Asymmetries in Adolescent Female Soccer Players

PURPOSE

To examine the effects of an 8-week combined strength and power training intervention on physical performance and interlimb asymmetries in adolescent female soccer players.

METHODS

Thirty-seven adolescent female soccer players (age 16.1 [1.1] y) were randomly assigned to a control group (n = 18) or experimental group (n = 19). The experimental group performed combined strength and power training twice a week, which consisted of strength and power exercises that trained the major muscles of the lower body and trunk musculature. Preintervention and postintervention tests included unilateral and bilateral horizontal and countermovement jump tests, a 40-m sprint test (10- and 30-m split times), a 10-m sprint with a 180° change-of-direction (COD) test, and a multiple-COD test (V-cut test). Asymmetries were also analyzed in the unilateral tests.

RESULTS

Significant group-by-time interaction of the improvement between pretest and posttest was observed for speed (effect size [ES]: -1.30 to -1.16) and COD tests (ES: -0.62 to -0.61) but not in jumping (ES: -0.09 to 0.28) and interlimb-asymmetry tests (ES: -0.13 to 0.57).

CONCLUSIONS

The short-term in-season combined strength and power training program induced greater speed and COD performance improvements than soccer training alone in adolescent female soccer players.

Assessment of energy availability and associated risk factors in professional female soccer players

This study aimed to assess energy availability (EA), alongside possible risk factors of reduced or low EA of professional female soccer players during a competitive season. Thirteen players (age: 23.7 ± 3.4 y, stature: 1.69 ± 0.08 m, body mass: 63.7 ± 7.0 kg) engaged in a 5-day (two rest days, one light training, heavy training and match day) monitoring period. Energy intake (EI) and expenditure during exercise (EEE) were measured. EA was calculated and categorised as optimal, reduced or low (>45, 30-45, <30 kcal·kg FFM^-1·day^-1, respectively). Relationships between EA and bone mineral density, resting metabolic rate (RMR), plasma micronutrient status, biochemical markers and survey data were assessed. EA was optimal for 15%, reduced for 62% and low for 23% of players. Higher EA was observed on rest days compared to others (P<0.05). EA was higher for the light compared to the heavy training day (P<0.001). EEE differed significantly between days (P<0.05). EI (2124 ± 444 kcal), carbohydrate (3.31 ± 0.64 g·kg·day^-1) and protein (1.83 ± 0.41 g·kg·day^-1) intake remained similar (P>0.05). Survey data revealed 23% scored ≥8 on the Low Energy Availability in Females Questionnaire and met criteria for low RMR (ratio <0.90). Relationships between EA and risk factors were inconclusive. Most players displayed reduced EA and did not alter EI or carbohydrate intake according to training or match demands. Although cases of low EA were identified, further work is needed to investigate possible long-term effects and risk factors of low and reduced EA separately to inform player recommendations.

Contextual factors influencing the characteristics of female football players

Women's football participation rates are projected to increase to 60 million worldwide by 2026, doubling the current participation. Growing investment and the increase in research in women's football has had a positive effect on the level of performance over the last 10 years. The present review aimed to examine the literature on the physical and physiological characteristics of female football players from 2010 to 2019 to reflect the recent changes in professionalism. Characteristics investigated include anthropometry, strength, speed, endurance, power, change of direction and repeated sprint ability. These characteristics are presented in relation to playing position, age and competition-level. Results revealed that goalkeepers (171 cm, 66 kg) and defenders (168 cm, 61 kg) were the tallest and had the greatest body mass, while attackers were the fastest players over 20 m (3.05 s) and 30 m (4.38 s) and midfielders had the highest endurance (55.4 mL∙kg^-1∙min^-1) (P<0.05). Characteristics tended to improve with age until full biological maturity around 17 to 18 years of age. Competition comparisons demonstrated international players have significantly greater speed, repeated sprint ability, power and endurance characteristics (P<0.05). By identifying influential factors, coaches may be able to optimize their training and physical assessment practices, to better expose players to the required stimulus to develop these characteristics considered crucial to improved performance.

Sprint Endurance Abilities in Elite Female Soccer Players

PURPOSE

To profile sprint endurance performance of elite-level female soccer players.

METHODS

Twenty-five female national-team soccer players (age 25.1 [2.7] y, body mass 59.6 [3.6] kg, height 168.5 [4.1] cm) were tested for sprint endurance, performing 5 maximal sprints, interspersed with 30 seconds of active recovery (5 × 30 m) and a 30-second all-out shuttle run in a soccer pitch. The Yo-Yo Intermittent Recovery Test level 1 (YYIR1) evaluated intermittent high-intensity endurance under the same field-testing conditions. Maximal anaerobic capacity was assessed while participants performed three 10-second all-out bouts separated by 20 seconds of passive recovery (3 × 10 s) on a nonmotorized treadmill.

RESULTS

Huge interplayer variability was observed for sprint decrements in 3 × 10 seconds (coefficient of variation = 37%) and 5 × 30 m (coefficient of variation = 62%). The 3 × 10 performance was largely associated with 5 × 30-m mean and best time and very largely with 30 seconds. A very large and nearly perfect correlation was observed between 30 seconds and 5 × 30 mMean (r = -.86) and 5 × 30 mBest (r = -.92), respectively. The YYIR1 was moderately to largely associated with 5 × 30-m variables and 30 seconds, respectively. A nearly perfect association was observed between 5 × 30 mBest and 5 × 30 mMean (r = .97).

CONCLUSIONS

Elite female soccer players' sprint endurance variables are characterized by remarkable variability. Associations between sprint endurance variables suggest physiological interdependence and a likelihood of a general ability in sustaining sprinting in this population.

Women's Football: An Examination of Factors That Influence Movement Patterns

Griffin, J, Larsen, B, Horan, S, Keogh, J, Dodd, K, Andretta, M, and Minahan, C. Title: Women's football: An examination of factors that influence movement patterns. J Strength Cond Res 34(8): 2384-2393, 2020-The popularity and professionalism of women's football has increased in conjunction with participation rates over the last 10 years, with projected female participation rates to double worldwide by 2026. Scientific interest has also increased, in part due to Fédération Internationale de Football Association now allowing global positioning system (GPS) units to be worn during all competitive matches, resulting in investigations into the match demands of women's football. Therefore, the purpose of the present review is to provide a summary of the literature specific to the movement patterns of women's football matches. Contemporary scientific investigation using GPS match data has led to a greater understanding of the movement patterns of football. Greater emphasis has been placed on high-speed running and sprinting during matches because of the strong link to scoring opportunities and being a distinguishing factor between international and national along with elite and subelite competition levels. Further research, however, is warranted in regard to accelerations and decelerations, given the high metabolic and mechanical loads and contribution to high-speed running and sprinting. With an influx of research into the movement patterns of match-play, investigators have begun to examine factors affecting match performance such as positional demands, age, level of competition, opponent, scoreline, and phase of the game. An understanding of the factors that influence match demands is vital to ultimately be able to understand the effects on performance and how manipulating these factors may improve football performance and reduce the risk of injury.

Short-Duration Beta-Alanine Supplementation Did Not Prevent the Detrimental Effects of an Intense Preparatory Period on Exercise Capacity in Top-Level Female Footballers

Purpose: High-intensity activity is an important aspect of football performance during competitive match play. The aim of this study was to investigate the effect of beta-alanine supplementation throughout a short-duration intense football-specific training period prior to an international competition on measures of high-intensity running performance. Methods: Twenty-four elite international U20 female footballers (age 18 ± 1 y, height 1.67 ± 0.07 m, body mass 62.7 ± 7.4 kg) volunteered to perform the YoYo Intermittent Recovery Test Level 1 (YoYo IR1), the Running Anaerobic Sprint Test (RAST) and a 20-m maximal sprint test on two separate occasions, separated by 3 weeks of training and supplementation. Participants were randomly assigned to receive either 6.4 g·day-1 sustained-release beta-alanine (BA, N = 12) or an equivalent dose of maltodextrin (placebo, PL, N = 12) throughout a 3-week standardized training camp. Results: There was a main effect of group (P = 0.05) and time (P = 0.004) on YoYo IR1; overall values were lower in PL and distance covered was lower post- vs. pre-supplementation. There was no group × time interaction (P = 0.07). There was an effect of sprint number for RAST, but no further main effects and there were no effect for the 20-m sprint. Conclusions: Top-level female footballers involved in this intense 3-week training period prior to a competition worsened their high-intensity intermittent exercise capacity, and this negative result was not attenuated by a short-duration BA supplementation protocol throughout the same period. Further work is necessary to elucidate whether adapted training protocols and BA dosing regimens could lead to better results.

The Effect of a Single Session of Plyometric Training Per Week on Fitness Parameters in Professional Female Soccer Players: A Randomized Controlled Trial

Nonnato, A, Hulton, AT, Brownlee, TE, and Beato, M. The effect of a single session of plyometric training per week on fitness parameters in professional female soccer players. A randomized controlled trial. J Strength Cond Res XX(X): 000-000, 2020-As the interest and popularity of female soccer has increased over the last few decades, there still lacks research conducted with the elite population, specifically ecological training interventions during the competitive season. Therefore, the aim of this study was to compare the effectiveness of 12 weeks (undertaken once a week) of plyometric (PLY) training on physical performance in professional female soccer players during the season. Using a randomized controlled trial design, 16 players were included in the current study (mean ± SD; age 23 ± 4 years, weight 60.3 ± 4.9 kg, height 167 ± 3.7 cm) and randomized in PLY (n = 8) and Control groups (CON, n = 8), respectively. Squat jump (SJ), counter movement jump (CMJ), long jump (LJ), single-leg triple jump distance test (triple jump test), changes of direction 505 test (505-COD), and sprint 10 and 30 m were performed before and after 12 weeks of PLY training. Significant within-group differences were found in triple jump test dominant (p = 0.031, effect size [ES] = moderate) and nondominant limb (p = 0.021, ES = moderate) and sprint 10 m (p = 0.05, ES = large), whereas the CON did not report any positive variation. However, neither group reported significant variation in SJ, CMJ, LJ, 505-COD, and sprint 30 m (underlining the difficulties in obtain meaningful variation in season). These findings have strong practical applications because this study showed for the first time that a single session a week of plyometric training can significantly increase sport-specific fitness parameters in professional female soccer players during the season.

Effects of plyometric jump training in female soccer player's vertical jump height: A systematic review with meta-analysis

To assess the effects of plyometric jump training (PJT) in female soccer player's vertical jump height, a review was conducted using the data sources PubMed, MEDLINE, Web Of Science and SCOPUS. Only peer-review articles were included. To qualify for inclusion in the meta-analysis, studies must have included (i) a PJT programme of at least 2 weeks, (ii) cohorts of healthy female soccer players with no restriction for age, (iii) a control group, (iv) a measure of countermovement jump (CMJ). The inverse variance random-effects model for meta-analyses was used. From 7,136 records initially identified through database searching, 8 were eligible for meta-analysis, comprising 9 training groups (n = 99) and 9 control groups (n = 94). The magnitude of the main effect was moderate (ES = 1.01 [95%CI = 0.36-1.66], Z = 3.04, p = 0.002). Sub-group analyses were performed (i.e., PJT frequency, duration and total number of sessions), revealing no significant subgroup differences (p = 0.34-0.96). Among the studies included in this review, none reported injury or other adverse effects. In conclusion, PJT is effective in female soccer players for the improvement of vertical jump height. In future, research must identify specific dose-response relationships following PJT, particularly in the long term.

Activity Profiles in U17, U20, and Senior Women's Brazilian National Soccer Teams During International Competitions: Are There Meaningful Differences?

Ramos, GP, Nakamura, FY, Penna, EM, Wilke, CF, Pereira, LA, Loturco, I, Capelli, L, Mahseredjian, F, Silami-Garcia, E, and Coimbra, CC. Activity profiles in U17, U20, and senior women's Brazilian national soccer teams during international competitions: are there meaningful differences? J Strength Cond Res 33(12): 3414-3422, 2019-The aim of this study was to compare locomotor activity profiles of Brazilian top-class female soccer players competing at distinct age brackets (under 17 [U17], under [U20], and senior). External match load of 14 U17, 14 U20, and 17 senior female soccer players competing in 6-7 full official international matches were assessed using global positioning systems. Total distance covered, distance covered in high intensity (15.6-20 km·h), distance covered in sprints (sprint: >20 km·h), number of accelerations (Acc) >1 m·s, decelerations (Dec) >-1 m·s, and Player Load generally increased across the age brackets (U17 <U20 <senior). For all playing positions, senior athletes presented greater total distance, accelerations, and decelerations than U20 players. For high-intensity distance and sprints, only central defender and midfielder senior players presented greater values than U20 players. Senior players demonstrated higher values in all locomotor activities in comparison to U17 players, irrespective of playing positions. Except for central defenders who presented similar total distance, sprint distance, and number of accelerations between U20 and U17, most match external loads evaluated in all playing positions were greater in U20 than in U17 players. These results provide useful information for player development and should be used to establish appropriate match-specific conditioning drills according to age categories.

Biomarker Response to a Competitive Season in Division I Female Soccer Players

Walker, AJ, McFadden, BA, Sanders, DJ, Rabideau, MM, Hofacker, ML, and Arent, SM. Biomarker response to a competitive season in Division I female soccer players. J Strength Cond Res 33(10): 2622-2628, 2019-The purpose of this study was to evaluate effects of training load (TL) on performance and biomarkers of health, performance, and recovery in Division I female soccer players throughout a competitive season. Subjects (N = 25, Mage = 20 ± 1.1 years) were monitored before the start of preseason and every 4-weeks thereafter (T1-T5). A battery of performance tests was administered before the start of preseason (P1) and end-of-season (P2), including body composition (percent body fat [%BF], fat free mass [FFM], and fat mass), vertical jump (VJ), and VO2max. Blood draws were conducted at every time point (T1-T5) to assess free and total cortisol (CORTF and CORTT), prolactin (PRL), T3, IL-6, creatine kinase (CK), sex-hormone binding globulin, omega-3 (n-3FA), vitamin-D (Vit-D), iron (Fe), hematocrit (HcT), ferritin (Fer), percent saturation (%Sat), and total iron-binding capacity (TIBC). Daily exercise energy expenditure (EEE) and TL were determined. There were significant declines in VO2max, VJ, weight, and %BF from P1-P2 (p < 0.05) with no significant differences in FFM. Training load and EEE significantly decreased from T1-T3 (p < 0.05). Significant increases were seen in CORTT, CORTF, PRL, T3, IL-6, CK, and TIBC throughout the season (p < 0.05). Significant decreases were seen in n-3FA, Fe, Fer, %Sat, and Hct throughout the season (p < 0.05). Female athletes experience significant physiological changes following high TL and EEE associated with preseason and appear to be further exacerbated by the cumulative effects of the season. Unique insights provided by biomarkers enable athletes and coaches to be cognizant of the physiological changes that are occurring throughout the season.

Quantification of Internal and External Load in School Football According to Gender and Teaching Methodology

The design of teaching tasks determines the physical and physiological demands that students are exposed to in physical education classes. The purpose of this study is to quantify and compare, according to gender and teaching methodology, the external (eTL) and internal (iTL) load resulting from the application of two programs that follow different teaching methodologies, i.e., a Tactical Games Approach (TGA) and Direct Instruction (DI), to teach school football. The Ratings of Perceived Exertion (RPEs) recorded in the assessments were also studied. A total of 41 students in the fifth year of primary education from a state school from Spain participated in the study (23 boys and 18 girls), aged from 10 to 11 (M ± SD, 10.63 ± 0.49 years) and divided into two class groups. All the sessions were monitored with inertial devices that made it possible to record physical activity and convert the information into kinematic parameters. The results indicated that the students who followed the TGA method recorded higher iTL values (heart rate) and spent more time performing high-intensity activities. Boys recorded higher eTL, iTL, and RPE values than girls. There was an evolution in the RPE between the assessments, with both groups presenting a more efficient RPE in the posttest. The TGA method favors student physical fitness and health, thus, this method is recommended when planning physical education sessions.