Water 2

Question 1

What is the current consensus on dehydration?

Answer 1

• “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)

Question 2

What are some reasons that elite athletes are hypohydrated?

Answer 2

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

Question 3

Why is environmental temperature largely corelated to hydration state?

Answer 3

• 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)

Question 4

How does hypohydration impact strength performance?

Answer 4

• 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

Question 5

Does hypohydration impair skill performance?

Answer 5

• 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

Question 6

What implications are caused by exercise-induced dehydration?

Answer 6

• 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

Question 7

What are some limitations of current evidence on hypohydration studies?

Answer 7

1. 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
   
   2. 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

Question 8

What is the purpose behind blinded hypohydration?

Answer 8

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

Question 9

What are some limitations of unfamiliarised hypohydration-race data?

Answer 9

• 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