Hopping on an exercise bike is an effective way to improve cardiovascular fitness and burn calories. Exercising beyond your endurance capacity, however, can lead to fatigue and other, possibly more serious, complications. Signs and symptoms of overexertion include breathlessness, muscle fatigue or tightness, cramping and feeling lightheaded or dizzy. Talk with your doctor before beginning an exercise routine, and consult a personal trainer for advice about working out on an exercise bike.
Energy and Exercise
Exercising requires energy, which the body creates with the help of a variety of nutrients and biochemical processes. Your body produces energy through aerobic or anaerobic metabolism — with or without oxygen, respectively. Aerobic processes provide 95 percent of normal energy production, according to the textbook "Fundamentals of Anatomy & Physiology"; as long as you maintain adequate oxygen intake, your body uses this process. When oxygen demand overcomes supply, the body breaks down pyruvic acid, which doesn’t require oxygen. This process is less efficient, providing less energy, and produces lactic acid as a byproduct. Anaerobic metabolism leads to muscle fatigue more quickly than aerobic metabolism. However, anaerobic processes are required for intense activities such as sprinting and lifting heavy weights.
Breathlessness
One sign of overexertion is breathlessness or difficulty catching your breath. Known as oxygen debt, your body is attempting to restore its pre-exertion oxygen levels. While pedaling an exercise bike, you can maintain a speed and resistance that still enables you to hold a conversation. At this point, your body is relying on aerobic metabolism and has enough oxygen to promote the creation of energy. Exercising past your endurance point, or choosing a speed or resistance that forces your muscles to work harder than usual, causes your body to run out of oxygen. Your breath becomes short, and you may find yourself gasping to take in enough oxygen. When conversation is out of the question and you cannot breathe without gasping, you are likely overexerting yourself.
Muscle Fatigue
Breathlessness may accompany muscle fatigue, although you can experience these symptoms alone. Muscle fatigue is characterized by a burning sensation, which can evolve into muscle tightness. The National Safety Council considers sore or painful muscles a sign of overexertion. Anaerobic metabolism is the likely cause of sore and tired muscles. After oxygen levels decrease and the body begins anaerobic respiration, less energy is produced for contracting muscles. In addition, lactic acid — the byproduct of anaerobic metabolism — builds up in the muscles. Lactic acid is linked to muscle fatigue as well as cramping and pain.
Considerations
Experiencing breathlessness, dizziness, chest pain, irregular heart beats, nausea and chest pain while exercising is an indication you are working too hard. However, these symptoms may also stem from certain health conditions. Heart disease, emphysema, chronic fatigue syndrome and asthma can limit your ability to exercise and induce fatigue. If you suffer from a health condition that influences your endurance and strength, talk with your doctor. She can suggest appropriate exercises that improve your physical fitness without aggravating your condition.
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