Water 2 Flashcards
What is the current consensus on dehydration?
- “Dehydration >2% BW degrades aerobic exercise performance in temperate-warm-hot environments. Greater levels of dehydration will further degrade aerobic exercise performance.” - most recent (15yrs old)
What are some reasons that elite athletes are hypohydrated?
Large proportion of athletes are classified as hypohydrated
- Athletes lose body mass and hydration during exercise especially endurance athletes
- Training allows time breaks for drinking, but competition doesn’t
- Match demands are slightly different to training demands hence we see hypohydration
- Avg of participant pool lost over 2% of BM during the trial, up to 6%
- Longer/ more intense the exercise the more likely hypohydration is to occur
- Even providing athletes with water, you cannot make them drink enough to not be hypohydrated
Why is environmental temperature largely corelated to hydration state?
- Greater environmental temperature exacerbates the negative effects of hypohydration
- Most people performed worse when hypohydrated, Avg decrement in performance got larger as environment temp got hotter - maintaining hydration is harder in hot environments(sweat rate)
How does hypohydration impact strength performance?
- 24 h complete fluid restriction with maximal strength test before and after
- Maximal voluntary force production reduced with hypohydration
- Hypohydrated trial has sig decline in maximal strength compared to euhydrated trial
- Situations of fatigue and hypohydration decreases performance to prevent injury
Does hypohydration impair skill performance?
- Hypohydration impaired:
- Line and length, but not speed of bowling
- Shuttle run performance
- Higher point = worst performance
- Bowling performance was sig worse when hypohydrated compared to euhydrated = increased accuracy for same speed
What implications are caused by exercise-induced dehydration?
- decreased plasma volume
- decreased mood
- increased plasma osmolality
- increased thirst
- decreased CV function
- increased body temperature
- increased muscle glycogen use
- increased RPE
- overall impaired endurance performance
What are some limitations of current evidence on hypohydration studies?
- Subjects are not blinded from the study intervention/aim - can cause psychological effects and change performance based on what they think is going on, know they are dehydrated
- Typical methods used to dehydrate subjects are unfamiliar, uncomfortable and outside usual practises - e.g.: diuretics that make you feel like you need the toilet for 3-4hrs
What is the purpose behind blinded hypohydration?
Allows to see whether the effect of knowing you are hypohydrated effects performance
- All responses were similar between 2 groups
- Unblind group had a worse performance in hypohydration
- Blinded group was very similar
Conclusions:
- Hypohydration does impair cycling performance in heat in males
- Performance decline is not made worse if the person knows if they are hypo/euhydrated
What are some limitations of unfamiliarised hypohydration-race data?
- More weight lost during an endurance event(hypohydration), the faster they complete the event(speed) - 2-8% loss in body mass. Association is that if you run faster, you sweat more because of more heat produced
- It would be surprising if faster finishers weren’t more hypohydrated at the end of a race