The purpose of this study was to evaluate the response of urine specific gravity (U sg ) and urine osmolality (U osm ) when compared to plasma osmolality (P osm ) from euhydration to 3% dehydration and then a 2-hr rehydration period in male and female collegiate athletes. Fifty-six National Collegiate Athletic Association (NCAA) wrestlers (mean ± SEM); height 1.75 ± 0.01 m, age 19.3 ± 0.2 years, and body mass (BM) 78.1 ± 1.8 kg and twenty-six NCAA women's soccer athletes; height 1.64 ± 0.01 m, age 19.8 ± 0.3 years, and BM 62.2 ± 1.2 kg were evaluated. Hydration status was obtained by measuring changes in P osm , U osm , U sg and BM. Male and female subjects dehydrated to achieve an average BM loss of 2.9 ± 0.09% and 1.9 ± 0.03%, respectively. Using the medical diagnostic decision model, the sensitivity of U sg was high in both the hydrated and dehydrated state for males (92%) and females (80%). However, the specificity of U sg was low in both the hydrated and dehydrated states for males (10% and 6%, respectively) and females (29% and 40%, respectively). No significant correlations were found between U sg and P osm during either the hydrated or dehydrated state for males or females. Based on these results, the use of U sg as a field measure of hydration status in male and female collegiate athletes should be used with caution. Considering that athletes deal with hydration status on a regular basis, the reported low specificity of U sg suggests that athletes could be incorrectly classified leading to the unnecessary loss of competition.
An acoustical handheld hydration monitor (HM) for assessing the water balance of the human body was developed. Dehydration is a critical public health problem. Many elderly over age of 65 are particularly vulnerable as are infants and young children. Given that dehydration is both preventable and reversible, the need for an easy-to-perform method for the detection of water imbalance is of the utmost clinical importance. The HM is based on an experimental fact that ultrasound velocity in muscle is a linear function of water content and can be referenced to the hydration status of the body. Studies on the validity of HM for the assessment of whole-body hydration status were conducted in the Appalachian State University, USA, on healthy young adults and on elderly subjects residing at an assisted living facility. The HM was able to track changes in total body water during periods of acute dehydration and rehydration in athletes and day-to-day and diurnal variability of hydration in elderly. Results of human studies indicate that HM has a potential to become an efficient tool for detecting abnormal changes in the body hydration status.
In almost any sport, athletes undergoing dehydration often suffer from numerous dehydration related injuries. The purpose of this study was to evaluate the validity of acoustic method to detect changes in the hydration status of athletes after undergoing acute dehydration and a 2-hour rehydration protocol. The acoustic method of assessing body hydration status is based on the experimental fact that ultrasound speed in muscle is a linear function of the tissue water content. The assessment of water imbalance was conducted by measuring speed of ultrasound in the calf muscles using through transmission method. Eighty-two male and female collegiate athletes were examined to detect changes in hydration status before and after undergoing 3% acute dehydration. Results demonstrated that the changes of ultrasound velocity are in average about 1.1 m/s per 1% of body dehydration and ultrasound velocity in muscle potentially may serve as a measure of body hydration status. However, ultrasound speed measurement using through transmission mode implemented in this study is highly dependent on the positioning of the probe: even slight variation in the acoustic path results in significant changes in the measured values, which may results in unacceptable error. A solution to this problem is proposed and discussed. [NIH2R44AG042990.]
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