Practices of Athletic Trainers Using Weight Charts to Determine Hydration Status and Fluid-Intervention Strategies

Design

A quantitative survey design was applied to meet the 4 research aims. The independent variable was clinical setting, with 3 levels: high school (HS), National Collegiate Athletic Association (NCAA) Division I, and small college (SC; NCAA Divisions II and III and National Association Intercollegiate Athletics [NAIA] combined post hoc). Variables of interest were weight chart use and postevent (ie, practices, games) fluid-intervention strategies.

Participants

Athletic trainers in the HS; NCAA Divisions I, II, and III; and NAIA settings were recruited from a randomized list of 1000 email addresses created by the National Athletic Trainers' Association (NATA) Member Services Department and a social media campaign. Participants included both staff and graduate assistant ATs. Job title and clinical setting were the only inclusion criteria. The university institutional review board approved the study before data collection began. Each participant provided informed consent by reading the purpose and study description on the survey's first page and proceeding to the first question.

Measurements and Instrumentation

Our 26-question quantitative survey was housed on a password-protected online site (SurveyMonkey, San Mateo, CA). The survey was divided into 3 sections: demographics, current weight chart practices, and postevent fluid-intervention strategies (Supplemental Table). Face and content validity were established by a panel of experts (2 academic specialists [15 years each of hydration research] and 1 clinical content specialist [15 years as a staff AT with Division I Southeastern Conference football]). The content panel met in person and online to determine which elements composed weight charts (units of measure, baseline weight, use timeframe, etc) via verbal consensus. The academic experts and principal investigator (J.M.E.) reviewed research and consensus statements before and after this meeting to ensure that all elements involved in the use of body mass changes for assessing hydration status were included in the survey.^{1,3,5,11,17–22} Questions were developed that asked the AT to report his or her current practice for each implementation element. The panel members added and revised the survey until they agreed that the survey contained all of the implementation elements. A pilot study of 44 graduate assistant ATs and 13 full-time ATs was then completed (data not included in the analysis). These ATs worked in a variety of clinical athletic settings and with various sports. The expert panel revised the survey based on the ATs' feedback to improve question clarity in order to obtain the desired data for each implementation element.

Procedures

The survey link and invitation to participate were e-mailed to potential recruits through NATA Member Services. After 1 month, we added a convenience sample by emailing colleagues with connections to HS and Division II and III ATs and a social media campaign to gather more responses for those clinical site categories. This convenience sample was assembled in a 2-week timeframe. Participants gave consent at the beginning of the survey and completed the instrument in 1 sitting.

Statistical Analysis

We calculated frequencies of responses for each question. Cross-tabulation with contingency table analysis determined if differences existed between clinical settings (HS, Division I, and SC) for select items. Adjusted residuals were analyzed post hoc to identify which cells deviated from independence. We used SPSS (version 25; IBM Corp, Armonk, NY) for the analyses and set α at .05 a priori. Bonferroni adjustments were conducted on the post hoc analyses.

Participant Demographics

We had a response rate of 25% (250/1000) from the NATA Member listserv. An additional 104 participants composed the convenience sample, for a total of 354 completed surveys. A total of 34.4% (n = 116) of the ATs worked in the HS setting, 45.7% (n = 154) in Division I, and 19.9% (n = 67) in the SC setting. Ages ranged from 21 to 70 years. Detailed demographic information appears in Table 1.

Table 1 Participant Demographics Across Clinical Settings

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Current Practices Using Weight Charts

The majority (57.2%, n = 191/334) of ATs did not use weight charts to measure changes in athletes' hydration status. Barriers were available time (17.7%, n = 34/192), accessible space (5.7%, n = 11/192), administrative help (11.9%, n = 23/192), or a combination (64.6%, n = 124/192). Of those who did not use weight charts, the majority (67.7%, n = 126/186) relied on athlete education and self-monitored urine color. Among those who used weight charts, 76% (n = 108/142) applied them to football, 28% (n = 41/142) to soccer, and 6% (n = 9/142) to wrestling. The use of weight charts did not differ by clinical setting (χ²₂ = 4.25, P = .119).

The implementation logistics of the ATs who used weight charts to determine hydration status are described in Table 2. Of the 60.9% (n = 81/133) of ATs who used a baseline weight, 27.8% (n = 37/133) took the weight at the first preseason practice. However, 83.1% (n = 69/83) did not verify if the athlete was hydrated at the time the baseline weight was measured. Only 7.2% (n = 6/83) used urine specific gravity to confirm hydration status. Of the ATs who used baseline weights, 74.0% (n = 54/73) did not recalculate the athlete's baseline weight, and 11.0% (n = 8/73) remeasured 5 days later. After Bonferroni adjustments, no differences were apparent between clinical settings for use of a baseline measure (χ²₂ = 8.70, P = .191) or verification of baseline weight (χ²₂ = 3.03, P = .805). Initial analysis indicated differences between clinical settings for use of the chart method (χ²₂ = 18.05, P = .001) or length of time used (χ²₂ = 31.11, P = .001). However, adjusted residuals showed that no value deviated from independence (P > .05).

Table 2 Use of Weight Charts by Athletic Trainers (n = 143)

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Postevent Fluid-Intervention Strategies

Overall, 56.1% (n = 171/305) of ATs had policies and procedures in place to address hydration status changes via weight charts, with no difference among clinical settings (χ²₂ = 4.77, P = .092). For the ATs who relied on percentage changes in body mass, Figure 1 illustrates the percentages they used to determine if an intervention was needed. The clinical settings did not differ for intervention value (χ²₂ = 22.95, P = .115).

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A total of 86.8% (n = 289/333) of ATs intervened via oral educational instructions with set amounts of fluid to consume, and 70.3% (n = 234/333) informed the athletes they were responsible for drinking fluids at home or at the dining facility on their own. One-third (30.0%, n = 100/333) of ATs provided a hydration handout to the athlete. A majority (58.9%, n = 196/333) supplied actual fluids to the athlete as an intervention; ATs in Division I furnished fluids more often than HS and SC ATs (χ²₂ = 16.849, P < .001).

Across settings, most ATs (71.2%, n = 237/333) shared body mass change information with their athletes and 61.0% (n = 203/333) with team coaches (Figure 2). Compared with other settings, more Division I ATs conveyed hydration changes to dietitians (χ²₂ = 19.497, P < .001), strength and conditioning staff (χ²₂ = 75.778, P < .001), and team physicians (χ²₂ = 14.621, P < .001), whereas parental contact was greater in the HS setting (χ²₂ = 103.922, P < .001). The majority of ATs (84.7%, 254/300) did not refer athletes with abnormal weight chart results to another sports medicine team member, and this plan did not differ by clinical setting (χ²₂ = 9.40, P = .052). Those ATs who did refer athletes directed them to the team physician (25%, n = 83/333), nurse (3%, n = 10/333), or dietitian (6%, n = 20/333).

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Participant Demographics

The survey participants represented ages 21 to 60 years and 0 to 40 years of clinical experience. The clinical settings surveyed were HS and all levels of collegiate athletics. Clinician experience ranged from newly certified to more than 20 years of clinical practice. The Division I setting had the largest number of respondents. The majority of ATs were preceptors to athletic training students, student aides, or both and enlisted them to assist with writing or typing body masses into weight charts. However, ATs did not typically ask their students or aides to calculate body mass changes. Relying on help to overcome administrative barriers is especially important for HS ATs because most HSs only employ or contract with 1 AT.²³ Athletic trainers in this setting should discuss with school administrators options for adding additional ATs to improve the care provided. Athletic trainers can also elicit help from the coaching staff.

Current Practices Using Weight Charts

A majority of ATs surveyed did not use weight charts to track hydration changes, even for a short period of time. This practice does not follow the recommendations of the NATA¹ and American College of Sports Medicine³ position statements, which advise tracking hydration status changes. More concerning was that these respondents did not determine hydration status using any other method, likely leading to unrecognized hypohydration or hyperhydration in some of their athletes. Hydration status can be measured in many ways, but the benefits of using weight charts are that they are noninvasive, field friendly, and quick.²⁴ Regardless of the environmental conditions and sport setting, weight charts should be used to track hydration changes in all athletes. Additional clinical recommendations for the efficient implementation of weight charts are available in Table 3.

Table 3 Weight Chart Implementation Elements and Corresponding Clinical Recommendations

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Weight charts were most commonly used for football, soccer, and wrestling athletes. This finding is encouraging, as these athletes are at risk for hypohydration due to the nature of their sports. Given that tracking weight in wrestlers is mandatory for sport participation,¹ it is interesting that more wrestling ATs did not complete the survey. This may have occurred because wrestling ATs use weight charts for verifying competition weight categories rather than hydration purposes.

Also, fewer ATs in female sports reported using weight charts. The athlete's sex should not be a deterrent to tracking hydration with weight charts, as both male and female athletes can have body weight challenges. Sensitivity and confidentiality regarding weight and body image can be concerns when using weight charts; however, steps can be taken to ensure privacy when obtaining an athlete's weight. Scales are available with a screen that can shield the athlete from viewing the measurement. A clinician can also record weight on a separate piece of paper or in a computer program and share only the hydration change with the athlete, not the absolute value.

Only a very small number of ATs verified that their athletes were hydrated when the baseline weight was recorded. In the absence of an accurate baseline weight, the chart may provide invalid information, as the calculations will be based on an athlete who is perhaps hypohydrated. A valid baseline weight can be ensured in 2 ways. The first option is to record the weight each morning for 3 days.⁷ The second option is to use a refractometer (clinical or digital) to measure urine specific gravity at a 1-time convenient weight. If urine specific gravity indicates the athlete is not hydrated (ie, ≥1.024),¹⁶ then he or she should return after an appropriate rehydration timeframe to try again.

Another key finding was that most ATs only calculated absolute differences in weight from pre-exercise to postexercise. Absolute calculations are helpful in determining individual rehydration recommendations but do not account for the athlete's size.⁷ An offensive lineman who weighs 250 lb (113 kg) and loses 5 lb (2 kg) of water during practice is of much less concern than a cross-country runner who weighs 150 lb (68 kg) and loses 5 lb. Therefore, the percentage change in hydration status provides clinical information on possible risk factors (hypohydration, hyperhydration) and should be considered in developing hydration policies and making return-to-play decisions.²

Weight chart calculations with corresponding clinical use recommendations are supplied in Table 4. Using a paper chart is helpful when staffing is minimal and athletes are recording their weights. However, a computer performs the calculations automatically, and clinicians can enact their hydration intervention plans sooner. Across all settings, a variety of individuals were tasked with measuring or recording weights. It is worrisome that, in some instances, athletes who recorded their own weights could fabricate the results if they were afraid of missing practices or games.

Table 4 Weight Chart Calculations and Recommendations for Clinical Use

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Most ATs used weight charts for the first 2 to 3 weeks of their seasons. Ideally, ATs would track athletes' hydration throughout the season for optimal performance, but if that is not possible, tracking the weeks carrying the highest risk for exertional heat illness is beneficial. During the weeks of highest risk (first 2 weeks of warm to hot conditions), appropriate hydration is an efficient prevention technique.¹¹ Only 1 respondent used kilograms. One kilogram of weight loss equals 1 L of water lost (1 kg = 1 L). When discussing hydration with athletes and implementing fluid-intervention strategies, it is helpful to use kilograms, particularly because the 1-L water bottle is common in athletic settings.

Postevent Fluid-Intervention Strategies

Regardless of clinical setting, the majority of ATs had written policies and procedures in place for identifying a hypohydrated athlete. Yet almost half of ATs lacked such policies and procedures, which fails to conform with the NATA¹ and American College of Sports Medicine³ position statements. We are unsure of the exact reasons why ATs do not have policies for hydration-related conditions. Future researchers should investigate barriers and why many clinicians do not use weight charts to identify hypohydrated or hyperhydrated athletes or have designated policies to follow.

We found that ATs used a change in body mass of −3% as the clinical threshold for intervention, which is appropriate because performance, cardiovascular, and thermoregulatory decrements were observed when this percentage was exceeded.^4,5,8,9 It is important to predetermine a threshold for developing policies and individualizing interventions, such as recommending the fluid amounts an athlete should consume to return to a euhydrated state.^1,3,7 Athletic trainers should not recommend athletes consume arbitrary amounts of fluids without knowing their change in body mass.^2,25 Examples of percentage hydration thresholds that can be used to set policies are provided in Table 5, but clinicians are encouraged to tailor the policies to their clinical setting.

Table 5 Example of Weight Chart Policy Thresholds

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When the AT deemed a fluid intervention was warranted, an overwhelming majority intervened with oral education about rehydration. Any education (oral or written) as a sole intervention produced mixed results.^26,27 In a cohort study,²⁸ investigators found that a 1-time education session was not enough to affect hydration behaviors compared with individual guidelines in adolescent athletes. In another study,²⁹ the authors demonstrated that multiple sessions of an educational intervention effectively instilled positive hydration behaviors in hypohydrated athletes. As researchers continue to determine the best methods of hydration education, we support ATs' use of oral interventions. Providing individualized fluid recommendations based on the weight chart results will be more beneficial than an arbitrary general recommendation.²⁵ For example, if the athlete lost 1 kg from prepractice to postpractice, the AT could orally or electronically (ie, via text message) advise the athlete to drink 1 L of fluid to replace these losses.

Most ATs shared hypohydration levels with their athletes and did not refer players with nonemergency hypohydration to sports medicine team members. Athletic trainers must remain mindful of the importance of an interdisciplinary health care team approach. Of those ATs who referred athletes to other sports medicine professionals, Division I ATs referred to dietitians more than ATs in other settings, most likely because of access and ease of referral. Athletic trainers are knowledgeable about hydration and can effectively monitor and treat athletes with hydration concerns.³⁰ Hydration information should at least be shared with coaches, regardless of level, as some athletes feel that coaches are barriers to drinking during practices. Coaches who are educated on hydration topics can encourage proper drinking habits to keep their players safely performing at peak levels.³¹