In-Season Longitudinal Hydration/Body Cell Mass Ratio Changes in Elite Rugby Players

Abstract

Background: Hydration status has a direct role in sports performance. Bioelectrical Impedance Vector Analysis (BIVA) and Urine Specific Gravity (USG) are commonly used to assess hydration. The study aims to identify the sensitivity and relationship between BIVA and USG in a field sports setting. Methods: BIVA and USG measurements were conducted five times throughout one rugby season. 34 elite male rugby players (25.1 ± 4.4 years; 184.0 ± 7.8 cm; 99.9 ± 13.4 kg) were enrolled. Differences over time were tested using one-way repeated measures ANOVA, and Bonferroni’s post-hoc test was applied in pairwise comparisons. Resistance-reactance graphs and Hotelling’s T2 test were used to characterize the sample and to identify bioelectrical changes. A repeated measures correlation test was conducted for BIVA-USG associations. Results: Two clear trends were seen: (1) from July to September, there was a vector shortening and an increase of the phase angle (p < 0.001); and (2) from December to April, there was a vector lengthening and a decrease of the phase angle (p < 0.001). USG reported neither changes nor correlation with BIVA longitudinally (p > 0.05). Vector variations indicated a body fluid gain (especially in the intracellular compartment) and a body cell mass increase during the preseason, suggesting a physical condition and performance improvement. During the last months of the season, the kinetic was the opposite (fluid loss and decreased body cell mass). Conclusions: Results suggested that BIVA is sensitive to physiological changes and a better option than USG for assessing hydration changes during a rugby sports season.

Somatotype and bioelectrical impedance vector analysis of Italian CrossFit® practitioners

“…In addition, showed an inverse correlation with the ratio of extracellular to intracellular water (ECW/ICW), independently of the BIVA approach [ 14 ]. BIVA has been studied in many sports [ 15 ], plotting the athletes within a tolerance ellipse of a given reference population, performing intra- or inter-group comparisons, monitoring athletes through a competitive season [ 16 , 17 ], or creating new tolerance ellipses for specific sports population, as it has been made in soccer players and referees [ 18 , 19 ], cyclists [ 20 ], synchronized swimmers [ 21 ], handball players [ 22 ] or natural bodybuilders [ 23 ]. To our knowledge, this is the first study analyzing the complete bioelectrical profile in CrossFit®.…”