A urine specific gravity (USG) spot-check is the analysis of the concentration of a urine sample
collected at a random time in the day. Many companies and sports teams have relied on urine
specific gravity (USG) spot-checks as a field measure of hydration due to the lack of
The MX3 Hydration Testing System provides this alternative through rapid Salivary Osmolarity
(SOSM) assessment. SOSM testing has significant advantages over USG testing in
convenience, accuracy, and non-invasiveness.
Several recent studies have cast doubt on the appropriateness of USG spot-checks a
hydration indicator due to the confounding effects of physical activity, diet and fluid intake on
urine production and concentration. These studies have demonstrated that USG spot-checks
have a very poor specificity, meaning that upwards of half of appropriately hydrated workers
could be incorrectly classified as dehydrated when using USG.
For more information about the limitations of USG measurements see our blog post on the
accuracy of USG spot checks.
The MX3 Hydration Testing System empowers organizations to routinely measure SOSM for
the first time as an effective and superior alternative to USG spot-checks.
SOSM has been demonstrated to be a responsiveness indicator of active (physical activity-
induced) dehydration when benchmarked against gold-standard blood-based biomarkers or
body mass changes. Where these studies have also integrated USG spot-check measures,
SOSM has typically shown superior performance.
Direct from tongue sampling and immediate results guarantee sample integrity. Measurement
data is automatically logged through the MX3 app and detailed reports are available in MX3
Web Portal, allowing organisations to have unparalleled access to their hydration assessment
For more information about the science behind SOSM measurements and the MX3 Hydration
Testing System see our MX3 HTS White Paper.