| Date | November 2020 | Marks available | 2 | Reference code | 20N.3.SL.tz0.10 |
| Level | Standard Level | Paper | Paper 3 | Time zone | time zone 0 |
| Command term | Calculate | Question number | 10 | Adapted from | N/A |
Question
A study considered the hydration status of 345 athletes. To assess validity, the best urine measure of hydration (urine osmolarity) was compared with four other measures (urine specific gravity; urine colour; thirst perception scale; and bioelectrical impedance analysis).
Correlation to urine osmolarity is shown in the scattergrams.
[Source: Fernández-Elías VE, Martínez-Abellán A, López-Gullón JM,
Morán-Navarro R, Pallarés JG, De la Cruz-Sánchez E, et al. (2014) Validity of Hydration Non-Invasive
Indices during the Weightcutting and Official Weigh-In for Olympic Combat Sports. PLoS ONE 9(4): e95336.
https://doi.org/10.1371/journal.pone.0095336. © 2014 Fernández-Elías et al. Published under the terms of
Creative Commons CC by 4.0 licence: https://creativecommons.org/licenses/by/4.0.]
State the measure with a non-significant correlation to urine osmolarity.
Calculate the difference in the strength of the correlation (r) with urine osmolarity between urine colour and thirst perception scale.
Urine osmolarity is considered the most accurate measure of hydration that does not require blood. Comment on the relative validity of each of the other methods in this study.
State two reasons why water is vital to sustain human life.
Discuss regulation of electrolyte balance in endurance exercise.
Markscheme
bioelectrical impedance analysis;
0.74 – 0.30;
= 0.44;
Accept in different order.
urine specific gravity is the most strongly related to urine osmolarity / therefore the most valid;
urine colour strongly positively related to urine osmolarity / therefore valid;
thirst perception scale only shows a small positive relationship with urine osmolarity / therefore questionable validity;
bioelectrical impedance is unrelated to urine osmolarity / therefore not valid;
basic substance for all metabolic processes in the body;
regulates body temperature;
enables transport of substances essential for growth;
allows for the exchange of nutrients and aids the removal/excretion of metabolic end products;
electrolyte balance can become a problem when electrolyte levels are too high or too low/balance is disrupted;
athletes lose large amounts of water through sweat, which must be replaced;
profuse sweating includes loss of sodium/electrolytes;
too much water intake can dilute electrolyte balance / hyponatremia;
cramping;
fewer electrolytes are lost through urine, as urine production declines;
dehydration induces ADH, which promotes the retention of sodium;
Examiners report
No issues.
No issues.
No issues.
No issues.
Candidates struggled with the application nature of this question.
