Feature
“most athletes tend to drink far too much while training
and racing, particularly in hot and humid conditions” overhydration appears to be the most
important means for preventing hyponatraemia
under these conditions.”
or muscle weakness, spasms or cramps,
restlessness and irritability, and in severe
cases, seizures, coma or even death. The
main reason for these symptoms and scary
consequences is a rapid swelling of the brain
that the condition prompts. In fact, there is some evidence to suggest that
too much sodium taken during an event can
also impair hydration, and may exacerbate the
condition.
It’s an issue that South African sports scientist
Prof. Tim Noakes has cautioned against for
decades. Over 50 studies on the subject,
including his seminal paper in the field, “Water
Intoxication: A Possible Complication During
Endurance Exercise”, led him to publish a book
titled Waterlogged: The Serious Problem of
Overhydration in Endurance Sports, and he
continues to vociferously decry the general
recommendations for fluid replacement during
physical activity.
Based on his research, Noakes suggests that
“if athletes drink when they’re thirsty, they’ll
be fine.” To put a figure on it, Noakes’ letter
titled “Sodium ingestion and the prevention
of hyponatraemia during exercise,” published
in the British Journal of Sports Medicine
(BJSM) in 2004, stated that “the absolute
maximum rate at which these athletes (female
runners who took up 4.25 hours to complete
a marathon) should have ingested fluid during
exercise was probably even less than 500
ml/h. This is substantially less than the drinking
guidelines of the American College of Sports
Medicine (ACSM) and the Gatorade Sports
Science Institute, which have promoted rates
of fluid ingestion of up to 1200–1800 ml/h.”
Divergent Thinking
The ACSM regularly updates their position on
hydration – most recently in 2016 in response
to an Institute of Medicine report – and have
since altered their guidelines. However,
Noakes and others remain critical for a few
reasons. For instance, a few key points
in the ACSM’s recommendations still
include:
• Thirst is not the best indicator
of how much fluid athletes
should replace in terms of fluid
and sodium losses following
prolonged physical activity
and/or heat exposure.
• ACSM experts also
recommend water losses
due to sweating during
exercise be replaced at a
rate close to or equal to the
sweating rate.
• Fluid replacement during
exercise is meant to prevent
excessive dehydration (weight-
loss greater than two percent
from baseline body weight) and
to avoid excessive changes in electrolyte
balance in order to avert compromised
performance.
• The guidelines note that consuming
beverages containing electrolytes and
carbohydrates often provide more benefits
than consuming water alone.
These guidelines are based on the premise
that even mild dehydration impairs exercise
performance, which numerous studies reveal is
not always the case. As already stated, slight
dehydration (a 2% to 6% decrease in body
weight) can actually improve performance.
Secondly, according to Noakes, exercise-
associated hyponatraemia is due to over-
drinking, not a lack of sodium and other
electrolytes.
Further support for this stance recently
came to the fore in a study published in
December 2014 in the journal Medicine &
Science in Sports & Exercise. Based on the
findings of the “Sodium Supplementation and
Exercise-Associated Hyponatraemia during
Prolonged Exercise” study of participants
in the 2014 Western States 100-miler trail
run, the research team concluded that “a
low sodium intake in supplements has
minimal responsibility for development of
hyponatraemia during continuous exercise up
to 30 hours, whereas overhydration
is the primary characteristic
of those developing
hyponatraemia.
Therefore,
avoiding
New Approach
So, how can athletes ensure optimal hydration
during racing and training? Most research
on hyponatraemia echoes Prof. Noakes’
recommendations that athletes drink to thirst,
rather than to a schedule, and that water
is sufficient to maintain optimal hydration.
That’s not to say you can’t or shouldn’t use an
electrolyte replacement drink, or a mainstream
sports drink. There are other benefits to these
drinks, such as the addition of liquid-based
calories and carbohydrates for energy, and
there is some evidence to suggest that 33% of
cramp sufferers can find some degree of relief
from the ingestion of electrolytes – sodium,
potassium, magnesium, chloride, and/or
calcium.
The important thing to remember is that total
fluid intake should be managed according to
guidelines that aim to prevent hyponatraemia.
The overconsumption of water and/or sports
drinks and electrolyte solutions can all result
in the development of this life-threatening
condition.
Given the distance and projected
finishing time for the vast majority
of entrants in the Dis-Chem Half
Marathon, hyponatraemia should
not be a problem on race day, but
it is suggested that all runners
drink according to your
perceived thirst – as in,
when you feel like a
drink – instead of
to a regular
schedule.
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