Studies that have compared transdermal (on the skin) sodium bicarbonate supplements to oral bicarbonate have generally found oral delivery to be better. The results from testing of transdermal bicarbonate have been mixed, both in terms of its ability to enhance exercise performance and its ability to affect systemic acid-base balance.[1][2]
Transdermal sodium bicarbonate supplements are applied as a lotion directly to the skin. Because they bypass the gastrointestinal (GI) tract, transdermal bicarbonate supplements are marketed to have all the advantages of oral bicarbonate without any of the unpleasant GI side effects. However, because transdermal bicarbonate is generally unable to affect the systemic acid-base balance, researchers in one study used a specialized technique to measure local changes in muscle pH after application of the transdermal bicarbonate. Consistent with previous studies, the researchers observed only a marginal change in systemic pH. However, the transdermal bicarbonate caused a significant increase in intramuscular pH, which indicates that it was penetrating into the muscles after application on the skin.[3] This trial was performed in resting participants, so the effect on exercise performance wasn’t tested. These results suggest that by affecting intramuscular pH, transdermal bicarbonate has the potential to affect exercise performance, but more research is needed to determine its efficacy.