hyponatremia-article

Document Sample
hyponatremia-article Powered By Docstoc
					                                      CHAPTER 4


  HYDRATION BELIEFS AND PRACTICES AMONG RUNNERS IN A MIDWEST
                          MARATHON



Lynne Stamey, Kay Wolf, Diane Habash, Laura Harris, Christopher Taylor, Jenna Bell-
Wilson




Abstract
      Over the last 30 years, the profile of a marathon runner has changed; novice

runners (typically > 4 hour completion) have joined in a race once associated with only

the elite. With the increase in novice and slower runners, reported cases of exercise-

associated hyponatremia (serum sodium concentration below 135 mEq/L ) during

marathons have increased and drawn attention from medical professionals, researchers,

racers and event coordinators 1-7. The purpose of this study was to measure the

differences between experienced and inexperienced marathon runners on their practices

and beliefs regarding fluid intake during marathons. Results show there is no difference

between the hydration beliefs and practices of experienced and inexperienced marathon

runners, nor is there a consensus among runners on proper hydration technique. Based on

subject responses, runners have developed inconsistencies in their hydration beliefs and

practices, intertwining information on hydration from new research with outdated

information.
Key words: Hydration, Hyponatremia, Fluid intake, Marathon, Runners

Introduction

       Fluid recommendations for athletes have wavered over the years. In 1996, the

American College of Sports Medicine (ACSM) published a position statement for

Exercise and Fluid Replacement 17 to promote euhydration among athletes during events

and training. ACSM recommended that during exercise, athletes should consume 150 ml

- 300 ml every 15 to 20 minutes (600 ml – 1200 ml per hour) to replace the fluid lost

through sweat, or consume “the maximum amount that can be tolerated” to prevent

dehydration. The belief was that thirst was not an accurate indicator of fluid need and by

the time an athlete became thirsty he was already dehydrated. The statement addressed

hyponatremia by recommending sodium containing fluids to replace the sodium lost

through sweat. Since the 1996 release, studies have shown that while sodium

supplementation may decrease the severity of exercise-associated hyponatremia, it is not

prevented if the athlete is over-consuming water in response to sweat losses18-20.

       In 2002, the International Marathon Medical Directors Association (IMMDA)

published an advisory statement on the Guidelines for Fluid Replacement During

Marathon Running 21 in an attempt to correct the belief that runners should “drink as

much as possible” for optimal performance. Contradicting ACSM guidelines of

consuming between 600 ml – 1200 ml per hour17, IMMDA recommended drinking ad

libitum, but no more than 400 ml – 800 ml per hour 22, 23. Due to differences among

individual athletes, IMMDA deemed it is unsafe to give a blanket statement on fluid

intake. In addition, IMMDA provided anecdotal evidence by interviewing elite-athletes

who stated they consumed minimal fluid during marathon events (~200 ml/hour) due to
difficulty ingesting larger volumes while running at a faster speed and higher intensity.

The following year, USA Track & Field (USATF) 24 issued an advisory statement

announcing the adoption of the new IMMDA guidelines. USATF also discussed the

importance of calculating an individual sweat rate for “optimal hydration”, providing

instructions for calculation.

       The 1st International Exercise-Associated Hyponatremia Consensus Development

Conference (CDC) 25 was held in 2005 with the primary goal of reviewing current

research to determine the etiology of exercise-associated hyponatremia. The secondary

goal was to provide guidelines for its prevention. CDC issued a position statement25

stressing the importance of thirst as the primary determinant of fluid intake and

recommending the USATF method of calculating sweat rate.

       The same year, ACSM convened to conduct a roundtable discussion and review

current research on hydration and physical activity26, issuing several evidence-based

consensus statements as a result. While no specific recommendations were made,

ACSM discussed the importance of education for both professional and recreational

athletes in preventing exercise-associated hyponatremia. ACSM suggested an

individualized approach to fluid intake, and identified evidence-based research which

shows that each athlete should calculate his or her sweat rate so that fluid intake never

exceeds sweat losses.

       In 2006, IMMDA 27 again revised their guidelines stating runners should drink

only when thirsty, and provided a chart showing recommended fluid intake to pace or

time. IMMDA emphasized that the motivated athlete should calculate an individual

sweat rate to determine fluid intake for prevention of both exercise-associated
hyponatremia and dehydration. In 2007, ACSM issued a new position statement 28,

emphasizing the individualized approach to hydration.     For runners who have not

calculated their sweat rate, ACSM recommended drinking ad libitum, but no more than

0.4 – 0.8 L/hr-1 (smaller amounts for low body weight, more for larger body weight).

       For the first time, the hydration guidelines from ACSM and IMMDA are close in

agreement. Both disregard the “one size fits all” fluid intake recommendations of the

past, and instead emphasize the importance of letting thirst dictate fluid intake. Although

ACSM placed more emphasis on the importance of sweat rate calculation28, both ACSM

and IMMDA agree that hydration is based on the individual, and calculating individual

sweat rates for proper hydration during a marathon can prevent exercise-associated

hyponatremia and dehydration25, 28.

       Marathon directors and organizers are aware of the dangers of hyponatremia and

have access to the current recommendations from the aforementioned organizations;

however the knowledge and behavior of the marathon participant is unknown. Data is

lacking on hydration beliefs and practices of marathon runners, and whether they have

knowledge of the current recommendations for fluid intake. Gauging the beliefs and

practices of marathon runners may provide valuable information on where to focus future

education efforts. The purpose of this study is to assess the hydration practices and

beliefs of marathon participants and measure the differences between experienced and

inexperienced marathon runners.

Methods

       A three part, thirty-one question survey was e-mailed to all registered participants

of the 2006 Columbus Marathon with a valid e-mail address. Part I and Part II of the
survey used a Likert Scale to measure beliefs and practices of the subjects54.

Respondents were asked to rank their level of agreement with each statement ranging

from one (“Strongly Agree”) to four (“Strongly Disagree”).

       Part I of the survey included twelve questions to determine the hydration beliefs

of the subjects. Part II of the survey asked eleven questions to determine the hydration

practices of the subjects. Part III of the survey included six close-ended questions

regarding demographics (age, gender), individual information on marathon times, number

of completions, hydration resources, and whether the subjects trained individually or with

a group.

Subject Selection

       Subjects included registered participants over the age of 18 who completed the

2006 Columbus Marathon, including all runners, walkers and wheelchair participants

(n=4,097). All participants who completed the survey in its entirety have been included

in the results (n=1,185).

Calculating Scores

       A four point scale was used for calculating mean scores. An answer of 3 or 4

indicated the question was answered correctly. An answer of 1 or 2 indicated the

question was answered incorrectly. The higher the mean score, the more accurate the

response. Items 1-12 were used to compute the “belief score”. The maximum score

possible is 48 (412), and the minimum score possible is 12 (112). Statements 15-25

were used to compute the “practices score”. The maximum score possible is 44 (411)

and the minimum possible score is 11 (111). To allow scores to be computed
accurately, several questions were reverse coded for calculation. For these questions

only, an answer of 1 became 4; an answer of 2 became 3; an answer of 3 became 2; and

an answer of 4 became 1.

Statistical Analysis

       T-tests of independent samples were used to compare beliefs and practices with

descriptive characteristics. Spearman’s correlation determined the relationship between

completion time and beliefs or practices. Pearson’s correlation was used when

calculating the relationship between demographics (age, gender) and beliefs or practices.

Results

       An internet survey was sent to 4,097 participants of the 2006 Columbus Marathon

via e-mail. A total of 288 e-mails were undeliverable, resulting in 3,809 delivered e-

mails. The number of e-mails opened by recipients was 2,247 (58.9% of delivered). The

number of surveys received back from participants was 1,270 (33.3% of delivered, 56.5%

of opened). Respondents who returned incomplete questionnaires were excluded (n=85,

6.7% of total returned), resulting in a total of 1,185 (93% of returned) completed survey

responses.

       There were 673 male (57%) and 562 female (47%), 623 experienced runners

(53%) and 562 inexperienced runners (47%). Age of the respondents ranged from 18 to

76. Results of the survey are reported in Tables 4.1 and 4.2
Table 4.1: Beliefs of marathon runners (n=1,185)

                                                                     Strongly                      Strongly
                                                                     Agree      Agree   Disagree   Disagree
                              BELIEFS                                    %        %        %           %
 Each marathon runner should consume a set amount of water
 per hour, depending on their body weight.                             10.0      38.8     46.9        4.2
 * Every person has different fluid needs during a marathon.           46.8      51.9      1.4        0.0
 My performance will suffer if I finish a marathon slightly
 dehydrated (slight decrease in total body weight).                    14.9      40.3     41.5        3.4
 If I am feeling thirsty, it means I am already dehydrated.            34.4      44.1     19.5        1.9
 Drinking before I am thirsty will prevent dehydration.                24.6      62.4     11.8        1.1
 It is better for my performance to drink more fluid than I lose
 during a marathon.                                                    3.1       26.2     60.6       10.0
 *It is better for my performance to drink a sports drink instead
 of water when running a marathon.                                     13.8      45.6     37.0        3.7
 The longer it takes me to complete a marathon, the more fluids I
 should drink.                                                         12.8      52.7     30.8        3.7
 My performance will suffer more if I drink too much than if I
 drink too little.                                                     8.4       43.5     44.9        3.3
 Regardless of the temperature on race day, I should drink the
 same amount of fluid for every race.                                  1.4       7.6      53.2       37.8
 Drinking a sports drink instead of water will prevent me from
 being over-hydrated.                                                  1.0       15.9     67.2       15.9
 I should continue drinking fluid after the marathon, even if I am
 not thirsty.                                                          27.1      61.5     11.1        0.3
* indicates question was reverse coded for analysis


Table 4.2: Practices of marathon runners (n=1,185)

                                                                     Strongly                      Strongly
                                                                      Agree     Agree   Disagree   Disagree
                         PRACTICES                                      %         %        %          %
 *I drink fluid only when I am thirsty                                  1.2     13.4      71.3       14.1
 *On a warm or hot race day, I tend to drink more fluids               41.2     57.1       1.5        0.2
 *I weigh myself before and after a training day run to
 check my fluid status.                                                5.3      16.6      49.5       28.6
 *I weigh myself before and after a race to check my fluid
 status                                                                 3.5     13.4      53.2       29.9
 I try to drink before I am thirsty.                                   18.2     71.6      10.1        0.1
 I try to replace 100% of the fluid lost through sweat and
 urination.                                                             8.9     44.8      44.0        2.4
 *I change how much I drink based on my thirst                          7.9     64.7      25.8        1.5
 I drink at every water station, whether I'm thirsty or not            11.8     33.1      43.4       11.7
 *I have calculated my sweat rate                                       1.4      5.1      50.1       43.5
 *I use my sweat rate calculation to determine how much I
 drink during a marathon.                                              0.7       5.1      50.5       43.7
 *I use the same drinking practices during training as I do
 on race day.                                                          11.6     42.3      39.2       6.9
* indicates question was reverse coded for analysis
       Experienced runners (30.5 ± 3.4) had a significantly higher belief score than

inexperienced runners (30.0 ± 3.0, p=<0.004), however there was no significant

difference between the practices of experienced (25  2.9) and inexperienced marathon

runners (24.7  2.8, p=<0.088). There was a significant negative correlation between

beliefs and completion time (r = -0.081, p=<0.005), but there was no relationship

between practices and completion time of runners (r= -0.013, p=<0.651). No relationship

was found between the beliefs of runners who participate in an organized running group

(30.3  3.0) and runners who do not (30.3  3.1, p=<0.566), nor is their a relationship

between the practices of runners who participate in an organized running group (24.9 

2.8) and the practices of runners who do not (24.8  2.9, p=<0.499), There was a

significant difference in the beliefs of male (30.7  3.1) versus female runners (29.7 

3.0, p=<0.0001), but no differences between the practices of male (24.9  2.0) and female

runners (24.7  2.8, p=<0.346). Finally, a significant relationship was observed between

the beliefs and age of marathon runners (r=0.125, p=<0.0001) as well as the practices and

age of marathon runners (r=0.115, p=<0.0001).

       The most frequent sources of hydration information were coach (67%), friends

(44.8%) and the internet (37%). This is consistent with runners who were experienced,

inexperienced; runners who do not participate in a training group; and runners with

completion times above and below four hours. Runners who train with a group use

coaches (68%) most frequently for hydration information, followed by friends (53%) and

running magazines (40.8%).

       The resources least frequented for hydration information for all runners are

IMMDA (0.7%), USATF (4.1%) and GSSI (4.6%). Results are reported in Table 4.3.
Table 4.3: Sources of hydration information (n=1,185)

                                                                  Train with a
                                                                     Group        Completion time
   Sources of      Total     Inexperienced      Experienced       Yes      No     <4 hrs   >4 hrs
  Information       %              %                %              %        %       %        %
 USATF                4.1                 3.4              4.8       5.7    3.5       4.6        3.5
 ACSM                 5.2                 4.1              6.3       5.7    5.0       5.6        4.7
 IMMDA                0.7                 0.2              1.1       1.1    0.5       0.7        0.6
 GSSI                 4.6                 3.9              5.2       5.9    4.0       5.5        3.3
 Magazine            17.7               17.7              17.6     40.8     7.9      15.9       20.4
 Coach               67.1               59.9              73.8     68.0    66.7      70.2       62.0
 Internet            37.0               36.0              37.8     29.5    40.1      37.6       36.0
 Friend              44.8               47.9              42.0     53.0    41.3      41.6       49.3
 Other                27.6                  27.7        27.4       24.6 28.8       26.5        29.1
USATF = USA Track & Field; ACSM=American College of Sports Medicine; IMMDA=International Marathon Medical Directors
Association; GSSI=Gatorade Sports Science Institute




Discussion

            The main factor contributing to exercise-associated hyponatremia is intake of

water and sports drinks in excess of fluid losses (sweat, urine)55. To reduce the incidence

of exercise-hyponatremia, experts have recommended that endurance athletes drink ad

libitum, and use their calculated sweat rate to individualize fluid needs24-26, 55. IMMDA25,

USATF24 and CDC25, 55 further suggest using thirst as an indicator of fluid consumptions.

Subject’s responses in the present study contradict these recommendations. A majority

of respondents (89.8%) try to drink before they are thirsty; with 87% stating that drinking

before they are thirsty will prevent dehydration and 78.5% believing if they are feeling

thirsty, they are already dehydrated. Only 14.6% of respondents stated they do not drink

until they are thirsty.

            While the recommendations for fluid intake post-exercise vary slightly, none

recommend excessive drinking. ACSM26 and IMMDA25 suggest that normal

consumption of food and beverage with higher sodium levels (pretzels, broth) post-

exercise will bring the body back into euhydration. USATF24 suggests the goal of post-
exercise hydration is to replenish fluids lost based on sweat rate calculations. However,

85.6% of the runners surveyed believe they should continue to drink after a marathon,

even if they are not thirsty. Hyponatremia can develop post-race due to aggressive

overhydration53 in an attempt to replenish fluids, especially if fluid losses are unknown.

       In 2003, USATF24 recommended calculating individual sweat rates for prevention

of hyponatremia and dehydration. Since then, sweat rate calculation has been endorsed

by IMMDA25, 27, ACSM26 and CDC55, as well as several sports nutrition companies such

as PowerBar56 and Gatorade57. Contrary to these endorsements, only 6.5% of

respondents have calculated their sweat rate, and only 5.8% of runners use their sweat

rate calculation to determine fluid intake on race day. In addition, only 22% of

respondents weigh themselves before and after a training run, and 17% on race day to

check their hydration status. Perhaps runners do not calculate their sweat rate due to the

cumbersome nature of the process. To calculate sweat rate, runners must weight

themselves nude prior to a run, track and measure fluid intake during a one hour run,

void, weigh themselves nude post run, subtract post-weight from pre-weight, convert to

ounces, and add to fluid consumed. This calculation should be completed in several

different environmental conditions for an accurate sweat rate calculation.

       The survey revealed several questions where the respondent’s beliefs and

practices were divided, indicating that half of the runners surveyed have improper

hydration techniques. When asked about performance and hydration, 48.2% of

respondents did not believe their performance would suffer more if they drank too much

than if they drank too little, while 55.2% believe their performance will suffer if they
finish a marathon slightly dehydrated. This is inconsistent with the practices of elite

marathon runners, most of whom finish the race slightly dehydrated15, 21.

Further increasing the risk of hyponatremia is the practice of drinking at every water

station (44.9%) whether they are thirsty or not.

       Of the 25 questions on hydration beliefs and practices, a majority of respondents

answered only three questions consistent with IMMDA25, 27, ACSM26 and

CDC55recommendations25-27, 55. Subjects (98.6%) believe that every runner has different

fluid needs during a marathon, 98.3% drink more fluids on hot or warm days and 91% do

not agree with the statement that they should drink the same amount of fluid regardless of

the temperature.

Summary

       The data reveal that there is not a difference between the hydration beliefs and

practices among experienced and inexperienced marathon runners, nor is there a

consensus among runners on proper hydration technique. According to the results,

runners have developed inconsistencies in their hydration beliefs and practices.

       There is a consensus among researchers6, 12, 32, 33, 58 that education is the key to

prevent hyponatremia. The results from this research show that a majority of marathon

runners (67.1%) look to their coaches for hydration information. Educating coaches

appears to be paramount in promoting proper hydration techniques to athletes.

Additionally, researchers have shown that education provided by marathon directors and

organizers can reduce the number of events of exercise-associated hyponatremia33, 45.

       While organizations such as ACSM, IMMDA and CDC are approaching

agreement in their hydration position statements, each publish slightly different hydration
recommendations. Perhaps runners need to be presented with one clear consolidated

hydration technique to prevent hyponatremia and dehydration, endorsed by all three

organizations. Many of the runners surveyed (17.7%) use magazines such as Runner’s

World as the source for hydration information. These magazines publish articles with

updated information from IMMDA and ACSM59, 60. It is unclear as to whether receiving

multiple versions of hydration techniques is confusing to the reader.

       Previous communications which stressed the importance of consuming “the

maximum amount that can be tolerated”17 have created a lasting impression with

marathon runners. These legacy beliefs are still maintained by many athletes. Future

campaigns will likely need to address this issue directly. Introducing “new” hydration

recommendations endorsed by the top three hydration organizations, ACSM, IMMDA

and CDC, may strengthen the message of proper hydration techniques to coaches and

athletes, reducing or preventing future cases of exercise-associated hyponatremia.

				
DOCUMENT INFO