The Hydration Status of Female Collegiate Soccer Players Over Consecutive Training and Match Days / Estado de Hidratación de Jugadoras de Fútbol Universitarias Durante Días de Entrenamiento y Partidos Consecutivos

Abstract Purpose: Hydration has been shown to play a pivotal role in sport. Soccer is a team sport in which the integrity of all players is vital for team performance; thus, individual player hydration status is important. The primary aim of this study was to investigate the hydration status of female collegiate soccer players during regular season. Methods: Sixteen collegiate female soccer players (age: 20.4 ± 0.8 years; height: 163.6 ± 6.9 cm; weight: 65.3 ± 12 kg) provided urine over 9 days to monitor their hydration status. Hydration was determined by urine specific gravity (Usg). Usg was analyzed in the morning (AM) and in the afternoon before practice/game (PM). Results: All 16 players were at least minimally hypohydrated (Usg > 1.010) in the AM on 5 of the 9 days tested. Players had significantly higher Usg values in the AM as compared to PM (F(1,250) = 23.09; p < 0.0001); however, there was no significant time*day interaction (F(1,250) = 1.98; p = 0.16). Conclusion: Data show a high prevalence of hypohydration occurring in this specific population. This sub-optimal hydration status could be a cause for concern in terms of overall performance. Efforts should be made to integrate hydration interventions and daily monitoring to minimize hypohydration in players.

Resumen Propósito: Se ha demostrado que la hidratación juega un papel fundamental en el deporte. El fútbol es un deporte de equipo en el que la integridad de todos los jugadores es vital para su rendimiento; por lo tanto, el estado de hidratación de cada jugador es importante. El objetivo principal de este estudio fue investigar el estado de hidratación de las jugadoras universitarias de fútbol durante la temporada regular. Métodos: Dieciséis jugadoras universitarias de fútbol (edad: 20.4 ± 0.8 años; estatura: 163.6 ± 6.9 cm; peso: 65.3 ± 12 kg) proporcionaron muestras de orina durante 9 días para controlar su estado de hidratación, la cual se determinó por la gravedad específica de la orina (Usg). La Usg se analizó en la mañana (AM) y en la tarde antes del entrenamiento o el juego (PM). Resultados: Las 16 jugadoras estaban al menos mínimamente hipohidratadas (Usg > 1.010) en la AM en 5 de los 9 días medidos. Las jugadoras tuvieron valores Usg significativamente más altos en AM en comparación con PM (F (1,250) = 23.09; p < 0.0001); sin embargo, no hubo interacción significativa de tiempo * día (F(1,250) = 1.98; p = 0.16). Conclusión: los datos muestran una alta prevalencia de hipohidratación en esta población específica. Este estado de hidratación subóptimo podría ser motivo de preocupación en términos de rendimiento general. Se deberían hacer esfuerzos para integrar las intervenciones de hidratación y el monitoreo diario para reducir al mínimo la hipohidratación en las jugadoras.

Resumo Objetivo: Foi demonstrado que a hidratação desempenha um papel fundamental no esporte. O futebol é um esporte coletivo no qual a integridade de todos os jogadores é vital para o desempenho da equipe; portanto, o estado de hidratação de cada jogador é importante. O objetivo principal deste estudo foi investigar o estado de hidratação de universitárias jogadoras de futebol do sexo feminino durante a temporada regular. Métodos: Dezesseis universitárias jogadoras de futebol (idade: 20,4 ± 0,8 anos; altura: 163,6 ± 6,9 cm; peso: 65,3 ± 12 kg) forneceram amostras de urina por 9 dias para monitorar seu estado de hidratação. A hidratação foi determinada pela gravidade específica da urina Usg. Sua Usg foi analisado pela manhã (matutino) e à tarde (vespertino) antes do treino ou jogo. Resultados: As 16 jogadoras estavam minimamente hipohidratadas (Usg > 1.010) no período matutino em 5 dos 9 dias medidos. As jogadoras apresentaram valores de Usg significativamente maiores no período matutino em comparação ao vespertino (F (1.250) = 23,09; p <0,0001); no entanto, não houve interação tempo * dia significativa (F (1.250) = 1,98; p = 0,16). Conclusão: os dados mostram uma alta prevalência de hipohidratação nesta população específica. Este estado de hidratação abaixo do ideal pode ser uma preocupação em termos de desempenho geral. Devem ser feitos esforços para integrar intervenções de hidratação e monitoramento diário para minimizar a hipohidratação em jogadoras.

Reliability and validity of various laboratory methods of body composition assessment in young adults.

Accurate measures of body composition (BC) are essential for performance and health. In addition to accuracy, BC measures should be practical and be minimally invasive to maximize their utility. The purpose of the present study was to compare the day-to-day variability and validity of four common laboratory-based body composition assessments to a criterion four-compartment model. Dual x-ray absorptiometry (DXA), air displacement plethysmography (BP), multi-frequency bioelectrical impedance (MF-BIA) and underwater weighing (UWW) were performed twice in a sample of 32 young men and women. Participants were assessed in a fasted, euhydrated state 2-7 days apart. All methods were compared to a criterion four-compartment model using BP-derived body volume, DXA-derived bone mineral content and MF-BIA-derived total body water (4CBP ). Additional four-compartment models using UWW- and DXA-derived body volume were also examined (4CUWW ) and (4CDXA ). Validity results were conducted with paired t-tests and Bland-Altman analysis. Reliability was determined using intraclass correlations (ICC), coefficients of variation (CV) and standard error of the measurement (SEM). Validity analysis revealed that all methods overestimated per cent body fat and fat mass, and underestimated fat-free mass when compared with 4CBP , but only DXA and BP were significantly different (P<0·008). All measures were highly reliable across days (ICCs > 0·9, CVs < 12%). Results of the present study indicate that typical laboratory-based methods of body composition are valid and reliable. However, we caution that results should not be translated between methods and assessments should be performed with the same instrument when the goal is to monitor changes in body composition over time.

Energy compensation after sprint- and high-intensity interval training.

BACKGROUND: Many individuals lose less weight than expected in response to exercise interventions when considering the increased energy expenditure of exercise (ExEE). This is due to energy compensation in response to ExEE, which may include increases in energy intake (EI) and decreases in non-exercise physical activity (NEPA). We examined the degree of energy compensation in healthy young men and women in response to interval training. METHODS: Data were examined from a prior study in which 24 participants (mean age, BMI, & VO2max = 28 yrs, 27.7 kg•m-2, and 32 mL∙kg-1∙min-1) completed either 4 weeks of sprint-interval training or high-intensity interval training. Energy compensation was calculated from changes in body composition (air displacement plethysmography) and exercise energy expenditure was calculated from mean heart rate based on the heart rate-VO2 relationship. Differences between high (≥ 100%) and low (< 100%) levels of energy compensation were assessed. Linear regressions were utilized to determine associations between energy compensation and ΔVO2max, ΔEI, ΔNEPA, and Δresting metabolic rate. RESULTS: Very large individual differences in energy compensation were noted. In comparison to individuals with low levels of compensation, individuals with high levels of energy compensation gained fat mass, lost fat-free mass, and had lower change scores for VO2max and NEPA. Linear regression results indicated that lower levels of energy compensation were associated with increases in ΔVO2max (p < 0.001) and ΔNEPA (p < 0.001). CONCLUSIONS: Considerable variation exists in response to short-term, low dose interval training. In agreement with prior work, increases in ΔVO2max and ΔNEPA were associated with lower energy compensation. Future studies should focus on identifying if a dose-response relationship for energy compensation exists in response to interval training, and what underlying mechanisms and participant traits contribute to the large variation between individuals.

Impact of 4 weeks of interval training on resting metabolic rate, fitness, and health-related outcomes.

Resting metabolic rate (RMR) and substrate oxidation (respiratory exchange ratio; RER) are important indicators of health. The effects of interval training on RMR have not been thoroughly investigated, which was the purpose of the present study. Thirty men and women (mean ± SD age and maximal oxygen uptake: 28.8 ± 7.6 years and 33.0 ± 8.3 mL·kg-1·min-1) completed 4 weeks of Wingate-based sprint interval training (SIT), repeated 1-min high-intensity intervals (HIIT), or served as controls. Before and after training, RMR, resting RER, maximal oxygen uptake, body composition, physical activity, and energy intake were recorded. Data were analyzed using a repeated-measures ANOVA. RMR increased in response to 4 weeks of SIT training (1789 ± 293 to 1855 ± 320 kcal·day-1; p = 0.003) but did not increase after HIIT (1670 ± 324 to 1704 ± 329 kcal·day-1; p = 0.06). While SIT increased RMR by ∼2× the magnitude of HIIT, the difference was not significant (p = 0.5). Fasting substrate oxidation and RER did not change (p > 0.05). Maximal oxygen uptake increased, and small changes were also observed in percent body fat and fat mass (p < 0.05 for all). In conclusion, SIT provided a time-efficient stimulus to increase RMR after 4 weeks in healthy adults. However, the clinical relevance of the changes observed in this study remains to be determined. Further studies should be conducted in obese individuals and those with diabetes or insulin resistance to examine if interval training (≥4 weeks) influences resting metabolic rate in magnitudes similar to that reported here.

Caffeine, coffee, and appetite control: a review.

Coffee and caffeine consumption has global popularity. However, evidence for the potential of these dietary constituents to influence energy intake, gut physiology, and appetite perceptions remains unclear. The purpose of this review was to examine the evidence regarding coffee and caffeine's influence on energy intake and appetite control. The literature was examined for studies that assessed the effects of caffeine and coffee on energy intake, gastric emptying, appetite-related hormones, and perceptual measures of appetite. The literature review indicated that coffee administered 3-4.5 h before a meal had minimal influence on food and macronutrient intake, while caffeine ingested 0.5-4 h before a meal may suppress acute energy intake. Evidence regarding the influence of caffeine and coffee on gastric emptying, appetite hormones, and appetite perceptions was equivocal. The influence of covariates such as genetics of caffeine metabolism and bitter taste phenotype remain unknown; longer controlled studies are needed.