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Table 1 Factors distinguishing the dehydration that occurs in many outdoor settings from that in hypohydration research studies

From: Are we being drowned in hydration advice? Thirsty for more?

 

Exercise settings (esp. outdoors)

Studies on hypohydration

Comments

Hypohydrated at start

Seldom

Some

Larger effects; see text and Figure 3

Hypohydration extent

Mostly <2% BM

Usually ≥2% BM

Larger effects; see text and Figure 3

Airflow

Usually high (e.g. >2 m/s)

Usually slow (e.g. <2 m/s) and partial coverage

Exponential relation to heat transfer; decreased T sk and Q̇ sk req

Thirst

Usually self controlled

Usually not self controlled, nor reported in results

May interact with other factors in Table

Familiarised to, or blinded against, the psychological effect of intervention

Not applicable

Very rare

Placebo and familiarisation effects (see Figure 2 and [85])

Exercise pacing

Often autonomous

Often imposed, for part or all of exercise

Interactions with other factors in table

Motivation to perform

Higher?

Limited?

Interactions with other factors in table

  1. Note that each of these factors can impair the validity of research findings for exercise occurring in outdoor settings, yet the findings of such research is largely used to produce hydration policies that are applied to the outdoor settings.
  2. T sk: skin temperature.
  3. Q̇ sk: skin blood flow.