A 4000 m cycling race is considered an endurance race, but also has characteristics of a sprint-type event. Training for the 4000 m may emphasize aerobic conditioning -- you cannot sprint the entire race. However, anaerobic training can increase overall and finishing speed. In recent research, both methods were found to have a positive effect on muscle metabolism and energy use.
Aerobic Respiration
During exercise, your breathing rate speeds up to bring more oxygen to hard-working muscle cells. Oxygen is used to form ATP -- an energy molecule -- that powers cells. Aerobic respiration occurs when your body has sufficient oxygen during your workout. Oxygen molecules allow you to continuously form ATP; thus, your muscles can work longer without experiencing fatigue. Carbohydrates, fats and protein are broken down during this process. Aerobic respiration forms carbon dioxide and water as byproducts, which are easily released by breathing. During endurance events at a sub-maximal pace, your body uses aerobic respiration to power your slow-twitch muscles.
Anaerobic Respiration
Without sufficient oxygen during exercise, your body begins anaerobic respiration. Power-based movements, like sprints or lifting heavy weights, are fueled by fast-twitch muscle fibers and anaerobic respiration. However, this process -- without an adequate oxygen supply -- tires your muscles much more quickly. Anaerobic respiration uses up available ATP sources and breaks down glycogen -- stored energy -- while producing lactic acid as a byproduct. Because lactic acid is difficult to eliminate, it builds up in your muscles and leads to fatigue and cramping.
Aerobic and Anaerobic Training Methods
High-intensity interval training targets fast-twitch muscles and your anaerobic processes, while endurance training increases slow-twitch, aerobic muscle fibers. Both can help you improve your 4000 m cycling experience. In a 2008 study published in the "Journal of Physiology," active but untrained subjects performed four to six 30-second, maximal-effort sprints three days per week or 40 to 60 minutes of continuous, moderate-effort cycling five days per week. Results found that both types of training induced similar metabolic muscle changes; each group saw increases in muscle endurance as well as effective fuel use. Researchers concluded that, if pressed for time, high-intensity training can be just as effective as endurance exercise.
Aerobic vs. Anaerobic
Whether aerobic or anaerobic training is more effective for a 4000 m cycling event may also depend on the athlete. According to Dr. Frederic Martini's book "Fundamentals of Anatomy & Physiology," amounts of fast- and slow-twitch muscle fibers differ with each individual. For instance, an athlete with better sprinting ability likely has more fast-twitch fibers than someone that is slower but can bike for longer distances. In either case, a middle road can be found. Martini's book states that your muscle cells respond to changes in exercise patterns. Fast-twitch fibers can develop intermediate fiber characteristics, improving aerobic endurance. Talk to a professional cycling coach to develop an individualized protocol for your cycling event.
References
- Premier Coaching Online: Aerobic vs. Anaerobic Training
- "Fundamentals of Anatomy & Physiology, 5th Edition"; F. Martini, et al.; 2001
- "Journal of Physiology"; Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans; K.A. Burgomaster, et al.; January 2008
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