Table 3 Comparative analysis of biomarker sources towards assessing human performance

Apocrine Sweat

Underarm, groin

Sweat volume, noninvasive and continuous measurements possible

Locations on body may intrude athlete mobility/comfort, limited locations on body.

No. There remains a need to validate fabricated devices in formalized studies

¹⁹

Blood

In the body

Well validated technology

Cannot be measured continuously, real-time, or noninvasively.

Yes. Sample drawn during physicals or when necessary.

¹³⁵

Eccrine Sweat

Pores distributed across skin (>100 glands/cm²)

Noninvasive, continuous measurements possible without intruding on athlete mobility

Skin contamination, dried sweat on the glands, low-sampling rates, sample volume (e.g., function of weather conditions).

Yes. There remains a need to continue to validate wearable devices in formalized studies

^{18,19,– 20}

Urine

Bladder

Sample volume, ease of access

Noninvasive, continuous measurements are not possible

Yes, urine color used to assess hydration. Biomarkers from urine used during drug tests

^{107, 136, 137}

Saliva

Mouth

Sample volume, ease of access

Limited to sports which require or necessitate mouthguard devices. Point-of-care (POC) devices currently developed in literature do not permit continuous measurements.

No. There remains a need to validate fabricated devices in formalized studies

^{12, 14, 15, 107, 108}

Tears

Eyes

Noninvasive measurement possible

Sample volume, continuous measurements not possible over long duration, limited biomarkers can be detected, athlete comfort and safety

No. There remains a need to validate fabricated devices in formalized studies.

^{138, 139}