Race pace intensities
Is a race pace intensity, working at threshold power and heart rate ranges, more aerobic or anaerobic? All endurance race efforts are mainly aerobic. The degree to how much anaerobic metabolism plays a role will all depend on the type of racing you are preparing for. Short hard forceful efforts, such as a burst of speed on a road bike, a 3-10 second sprint, or a super steep climb on a trail, may all require some degree of anaerobic metabolism. But outside of a 3-10 second all out effort, your aerobic systems are mainly in play, even at a race pace or threshold intensity. Aerobic systems work towards removing lactic acid that is built from hard efforts. The stronger your aerobic system is, the faster you will remove acid from the muscle and the faster you will recover from each hard effort.
Working at threshold or race pace intensities is often looked at as an intensity that calls upon anaerobic properties to get the job done. In part, some anaerobic energy is used but it is mainly aerobic properties used within aerobic and anaerobic systems that play a main role in producing energy while working race pace intensities. To understand this you need to understand the different types of muscle fibers and the properties they carry. You have three types of fibers within the muscle. Type I, Type II-A, and Type II-B. Type I fibers carry aerobic properties only. Type II A fibers carry a mix of aerobic and anaerobic properties and type II-B fibers carry anaerobic properties only. Types II B fibers are the only muscle fibers that do not require oxygen to produce energy. Anaerobic means without oxygen. Type II-B fibers are your true anaerobic fibers and are the fibers used when there is a need for a very hard short effort from 3-10 seconds if not slightly longer. Outside of these short efforts, your ability to absorb oxygen within the muscle from aerobic adaptations within your type I and type II A fibers plays a key role in producing energy, even at race pace.
Type II A fibers come into play at all intensities but to which degree depends on how intense the activity is. They definitely come into play in larger quantities when working at threshold intensities or above and working threshold efforts or above takes place within all races, to different degrees depending on the race. It is the mix of aerobic and anaerobic properties that the type II A fibers carry that make them a key player in building power and speed for endurance events. To make gains to these fibers, you need to work your upper end ranges near threshold and above. A race or a hard ride is a great way to make gains to your type II fibers, as well as working forceful efforts on single speeds or using big gears. But there are a few major drawbacks to working with too much intensity too often. Training stress working at threshold ranges and above is high and too much work there is the most common reason for overtraining. Once over trained, a loss of power, sore muscles, and a lackluster mental attitude will follow. Recovery from an over trained state can take a long time. Also, the potential you have for making aerobic gains while focusing on working hard efforts is far less than your potential for making aerobic gains while working easier, focused on your type I aerobic friendly fibers. Like mentioned above, it is your potential for removing lactic acid that gives you more endurance and potential to produce a higher level of power for the duration of an endurance event.
As an endurance athlete, focusing on making aerobic gains is a priority. Your internal aerobic engine has more room to grow compared to your anaerobic engines. Too much hard work above your threshold ranges will elicit gains but it will also lead to an over trained state if it is taken too far. Each athlete can greatly vary in terms of how much high intensity stress they can handle. The best way to know how you handle intensity is to follow all forms of bio feedback, including heart rate responses, perceived exertions, and breathing trends. There are times of the year to focus on a majority of hard efforts but those times of year need to be timed well and kept in moderation to help peak for certain events. Working forceful efforts into the upper end ranges, using single speeds, big gear work, or running hills, is very important at times but how often and in what duration is another topic for another time.
Mike Schultz CSCS
Highland Training LLC
Phone: 814.289.6620 | Email: firstname.lastname@example.org