Running increases muscle activity and metabolism. According to the American Academy of Orthopedic Surgeons, during exercise the body releases 70 to 90 percent of the energy produced as heat. Perspiration cools the body and results in a loss of fluid. Dehydration and electrolyte depletion may trigger muscle cramps and swollen fingers while running.
Heat and Dehydration
Water regulation in the body occurs through a feedback loop to the brain. According to the "Journal of the American Dietetic Association," when exercise reduces water in the blood, the brain releases a hormone called anti-diuretic hormone, also known as ADH, to prevent the loss of water in urine. However, heavy sweating without proper hydration leads to dehydration and an inability to produce enough sweat to cool the body. According to the American Academy of Orthopedic Surgeons, failure to replace salt and fluids during intense, longer-duration exercise causes heat cramps in the leg muscles, stomach or arm and may lead to heat exhaustion.
Hyponatremia Symptoms
Runners may develop low blood sodium levels from dehydration or by drinking more water than is lost in sweat. According to "Sports Science Exchange" signs of hyponatremia include puffy fingers and ankles, bloated stomach and severe headache. Drinking excess water dilutes the sodium in the blood and causes water to enter the brain and cause swelling that can lead to confusion, coma and death.
Staying Hydrated
Maintain adequate hydration by replacing the amount of fluid lost while running. Recommendations reported in "Sports Science Exchange" suggest limiting fluid intake to no more than 400 to 800 mL per hour while running to reduce the risk of hyponatremia. According to the Colorado State University Extension, the body absorbs chilled fluids faster and cold beverages help lower body temperature.
Treatment Options
Stop running when leg cramps and swollen fingers occur. The American Academy of Orthopedic Surgeons recommends gently stretching the sore muscles and replacing fluid lost with cool water or a low-sugar electrolyte solution like a sports drink. Seek medical attention for severe cramps, dizziness, nausea and vomiting.
References
- American Academy of Orthopedic Surgeons: Heat Injury and Heat Exhaustion
- "Sports Science Exchange"; Hyponatremia in Athletes; Bob Murray Ph.D., John Stofan and E. Randy Eichner M.D.; 2003
- "Journal of the American Dietetic Association"; Water: Can the Endurance Athlete Get Too Much of a Good Thing?; Susan I. Barr and David L. Costill; November 1989
- Colorado State University Extension: Nutrition for the Athlete
