Sweat sodium loss influences serum sodium concentration in a marathon A Spanish group examined, which has the loss of sodium with the welding for an influence on the sodium concentration in the blood. 51 runners were divided into different groups based on their welding.It was a connection between sodium loss in the welding and sodium in the blood.
However, the runners with the largest sodium loss in the sweat did not develop hyponatemia. All numbers can be found under https://pubmed.ncbi.nlm.nih.gov/26661748/