Using an elliptical machine gives you an effective cardio workout and is much less stressful on your muscles and joints than running or jogging on a hard surface. However, working out on an elliptical machine requires a certain amount of stamina and endurance just like any other cardio exercise. Some fatigue is normal, but if you are not in shape or not getting enough nourishment, leg fatigue occurs more quickly and is more pronounced.
Fatigue in your legs as the result of running -- or a running-like motion when using an elliptical machine -- occurs when your leg muscles cannot contract properly anymore. Your legs might feel heavy and experience pain or cramps. The feeling of fatigue often is accompanied by a burning sensation in your legs, but that should fade after several minutes. It also might be difficult or mildly painful to stand or use your legs.
Muscle fatigue was commonly thought to be caused by the buildup of lactic acid, which is produced as a waste byproduct of muscle contraction, but that theory has been discredited. Scientists at Columbia University have shown that one factor leading to muscle fatigue is leaking calcium. Their research found that at some point during exercise, tiny channels in the muscle start to leak the calcium, which weakens muscle contractions, causing fatigue. The research originally was meant to produce a drug for sufferers of heart problems, but subsequent tests verified that the same principles applied to skeletal muscle, particularly the muscles of the leg.
Regardless of the exact mechanism that triggers leg fatigue, certain conditions have been found to contribute to it during or after cardio activity. These include improper nutrition, dehydration, lack of muscle strength and overexertion. Overexertion is a common cause of leg fatigue in those new to exercise who don't realize what their fatigue threshold should be. Although using an elliptical device is a low-impact exercise, it still requires endurance and strength in the muscles of your leg. Once your leg muscles are stronger, they function more efficiently, and it takes longer for them to tire. Your muscles also require the proper fuel in the form of nutrients and water; lack of either can lead to an early onset of fatigue during activity.
If you are just starting a cardio program using the elliptical, pace yourself and stop as soon as your legs start to feel tired. Start slowly and gradually increase your intensity over a period of days or weeks. Add exercises that strengthen your leg muscles to your regimen. Drink water before and after activity to stay hydrated. If you are using the elliptical for more than 30 minutes, take a break during activity to drink water. Consume a healthful, nutrient-dense diet so your leg muscles have the proper fuel. If you are a casual user of the elliptical, consuming a meal that has mostly carbohydrates with some protein and fat the day you exercise should help. If you are a more serious athlete, you should consult with a certified sports nutritionist to find a diet that suits your needs. Get plenty of rest and avoid exercising on the elliptical if you are tired or your legs are sore. Consult a doctor if taking preventive measures doesn't help.