Fitness Testing

Sweat Patches

Sweat collection using patches can be used to determine the composition of sweat.

purpose: to use sweat patches applied to the skin to collect a sample of sweat for analysis.
equipment required: sweat patches (available from Gatorade), razor, alcohol wipes, centrifuge, sweat analyzer (or external laboratory).
description / procedure: There are many possible skin sites to use for sweat collection. The site used may depend on the purposes of testing. Commonly used are the upper back, chest, forearm, thigh and forehead. If standard sites are used, they need to be measured up and marked for correct placement. Prepare the skin by shaving any hair and clean with alcohol wipes and allow to dry. Another method is to wash the area with de-ionized water. Place the small absorbent sweat patches on the skin. At the conclusion of the exercise protocol, the patches are removed and placed in a centrifuge, where they are analyzed for electrolyte content. If the analysis equipment is not available, some laboratories can do the analysis for you. (see also the sweat collection videos)

analysis: Most commonly tested is the electrolyte content including sodium (Na), potassium (K), and magnesium (Mg+2). This is important as depletion of sodium, the primary electrolyte in sweat, can lead to muscle cramping.
results: The results can be used to give feedback to the athlete to improve their hydration practices. Some people may be found to be 'salty sweaters', meaning they have high concentration of Na- in their sweat. These individuals may benefit from appropriate modification to their fluid and food intake for optimal electrolyte replacement. Research can also be performed to determine if sodium losses change throughout an endurance event, under different conditions and exercise intensities.
reliability: If the subject is to be retested, or athletes are being compared, accurate placement of the patches is very important for reliability. It is also important to standardize the testing conditions, so that the exercise intensity, duration, clothing, and environment are the same.
comments:
- the cost and requirement to send the sweat off for laboratory analysis makes this testing method more suitable for research purposes.
- sweat patches are also used to test the levels of sweat chloride as a test for cystic fibrosis

references:
- C Palaciosa, K Wigertza, B Martina, C.M Weavera, Sweat mineral loss from whole body, patch and arm bag in white and black girls. Nutrition Research. Vol 23, Issue 3, p401-411 (March 2003)