If you've ever had an awesome, intense leg workout, you may have experienced post-workout muscle shaking. In most cases, this is a normal response that's easy to correct. However, if shakiness is accompanied by nausea, extreme weakness or confusion, see your doctor -- it could indicate diabetes or hypoglycemia. An occasional case of leg shakes that is purely the result of intense training usually has two main culprits.
The most likely cause of leg shaking after exercise is the result of nerve confusion. As you train, your muscles tire and the nerves that send impulses to them to contract become overloaded, causing muscles to shake. The buildup of lactic acid, a byproduct of muscle contraction, can also result in muscle cramping, fatigue and shakiness. When this happens, simply resting for a few minutes will usually stop the shaking. You may also be able to reduce this effect by slowly increasing training load rather than trying to be Arnold during your first week in the gym.
Hydration and Nutrition Deficiencies
The other common cause of post-workout shakes is dehydration and low blood sugar. If you become dehydrated, your muscles will have a tougher time recovering, which can cause shakes to linger a little longer. Nutritional deficiencies and low blood sugar can also cause shaking. If you start to feel light-headed or shaky during or after a workout, sip on a sports drink or eat a snack containing carbohydrates to boost your blood sugar.