Table 4.
Best practice recommendations for measuring sweat [Na+] of athletes in the field using the absorbent patch technique
| Local sweat [Na+] | |
|---|---|
| Conditions | Test during exercise (as opposed to passive heat stress or pharmacologically-induced local sweating) |
| Test in conditions (environment, intensity, season, equipment, etc.) representative of training/competition | |
| Conduct multiple tests within athletes to determine sweat [Na+] in various conditions | |
| Methods | Check for background electrolytes in collection system (e.g. patches, storage tubes, etc.) |
| Anatomical location: consider site accessibility and validity compared with whole-body sweat [Na+] (e.g. forearm may be best suited when considering both factors) | |
| Clean skin immediately prior to application: alcohol, deionized/distilled water rinse, and dry with sodium-free gauze/towel | |
| Apply multiple patches per athlete (e.g. right and left forearm) to have a backup (e.g. in case one patch falls off) | |
| Apply patches 20–30 min after the onset of exercise (to establish steady-state sweating prior to sweat collection) | |
| Avoid hidromeiosis: prevent patch saturation by limiting patch time on skin, using patches with high absorbent capacity, and/or changing patches frequently | |
| Check patches for adherence to skin—flag data if patch becomes detached prematurely | |
| Apply multiple patches per session if expecting significant changes in factors that would impact sweating rate (exercise intensity or environment) or if conditions are conducive to whole-body hidromeiosis (e.g. prolonged intense running in humid, still air) | |
| Avoid cross-contamination when working with multiple athletes (e.g. use clean forcipes for each patch) | |
| Storage | Refrigerate (e.g. approximately 4 °C) for up to approximately 3–5 days in airtight (e.g. Parafilm-M® sealed) containers |
| Analysis | IC or ICP-MS in the laboratory; ISE in the field |
| Analysis in the field recommended if sample storage duration and conditions during transportation cannot be well-controlled | |
| Corrections | Use regression equations to predict whole-body sweat [Na+] from local sweat [Na+] |
| Quality control | Flag samples that meet the following criteria: |
| • Sweat sample volume suggestive of saturated patch (volume depends on specific patch type and size) | |
| • Sweat [Na+] <10 mmol/L or >90 mmol/L | |
| • Sweat [K+] <2 mmol/L or >10 mmol/L |
See text for discussion and supporting references
IC ion chromatography, ICP-MS inductively coupled plasma mass spectrometry, ISE ion-selective electrode, [K + ] potassium concentration, [Na + ] sodium concentration