If you experience shaking or trembling after a run, you could be suffering from muscle fatigue or low blood sugar. Both of these conditions can signal danger, or even an emergency situation. Muscle shaking or quaking is a sign of muscle fatigue, while trembling hands and limbs can indicate your body is out of fuel -- sugar -- and you are in a hypoglycemic state.
Shaking from Muscle Fatigue
To build muscle mass, bodybuilders perform exercise to the point of muscle fatigue; the point when proper form can no longer be sustained during the required movements. Running can also fatigue your muscles in a manner similar to resistance training. When your muscles tremble or twitch from fatigue after running, it can be a signal that you are pushing yourself too hard and you are in danger of causing injury to your muscles, tendons or ligaments.
Causes of Muscle Fatigue
If your muscles fatigue quickly while running, you may be overdoing your exercise program. Skeletal muscles are comprised of cell groups connected to the spinal cord by motor nerves. Cell groups contract together, with groups fatiguing at different rates during sustained exercise, such as running a long distance. When some of a muscle's cell groups stop functioning, shaking, trembling or quaking movements occur. A period of rest allows muscle cell groups to return to normal.
Shaking from Hypoglycemia
Hypoglycemia, low blood sugar, is most likely to occur in people with diabetes, but can occur in non-diabetic individuals. One of the first symptoms of hypoglycemia is shaking, along with hunger, sweating and changes in skin color. The condition occurs when blood sugar levels are low and your body's signaling process -- that results in the release of glycogen from the liver -- does not function properly. Instead, your body releases adrenaline -- which is normally released by your body when you are in danger. Adrenaline responses result in muscle shaking or trembling, rapid heart rate, dilated pupils and other physiological reactions to danger.
How Gluclose Stores are Depleted
Glucose fuels your body, from your brain to your toes. Your vital organs, such as your brain, obtain glucose from your bloodstream. But your muscles are excluded from using glucose from your blood. Instead, your muscles have their own store of glucose in the form of glycogen. During exercise, your muscles burn glycogen, turning to body fat -- a less-efficient form of energy -- if you deplete your glycogen stores.
- Understanding Diabetes; H. Peter Chase, MD
- National Diabetes Information Clearinghouse: Hypoglycemia
- HuffPost Healthy Living: Muscle Shaking: Is Your Workout Better If Your Body Trembles?
- Scientific American: Why Do Muscles Tremble After Strenuous Exercise?
- University of California: Muscle Physiology: Extracting Energy from Gluclose
- Peak Performance: Muscle and Gluclose