Sweat iron concentration during 4-week exercise training.
Level 3 - non-randomized controlled study
Prospective single-arm follow-up study without a non-exercising control group.
PubMed 30260183 · doi:10.26444/aaem/78787
What was done
43 untrained volunteers were enrolled in a 4-week progressive exercise training program (cycle ergometer and cross-trainer at 85% maximal heart rate, progressing from 8 minutes per device in week 1 to 15 minutes per device in weeks 3 and 4); 29 completed the full program. Sweat samples were collected using a sterile sweat patch placed between the shoulder blades on days 1, 15, and 28 to measure sweat iron and sodium concentrations.
What was found
Sweat iron concentration did not differ significantly between day 1 and day 15. On day 28, sweat iron was significantly increased compared with day 1 (p < 0.001) and day 14/15 (p = 0.006). Median sweat iron concentrations were 21.2 ppb on day 1, 52.5 ppb on day 15, and 286.2 ppb on day 28. The ratio of iron to sodium concentration in sweat was also significantly increased on day 28 (p < 0.005).
Why it matters
This indicates that starting regular exercise training substantially increases sweat iron concentration, highlighting dermal excretion as a potential contributor to exercise-related iron depletion.
Limits
The study lacked a non-exercising control group, had notable participant attrition (14 of 43 dropped out), and had a small final sample size (n = 29). The abstract reports no whole-body sweat volume, systemic iron status biomarkers, or dietary intake controls, leaving net whole-body iron loss unmeasured.
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