Developing and optimizing endurance for athletic performance

by Panos Prokos, MS, CSCS

Note: Before starting any type of exercise program obtain clearance from your physician. Always train under the supervision of a qualified Personal Trainer or coach. Aerobic exercise places increased stress in your heart and can possibly produce dangerous side effects.

This article is written in addition to my previous subject concerning muscle development. I have noticed through the e-mails I receive, that in a similar way to muscle development, muscle endurance as well as aerobic fitness are subjects of interest and at the same time surrounded by much mystery and misinformation. In this article, I will attempt to shed some light into the subject and explain some of the most important principles for achieving better endurance and aerobic ability.

We should begin by examining the difference between muscle endurance and aerobic endurance. Muscle endurance simply refers to the number of muscular contractions or the number of repetitions RM performed by a muscle. Cardiorespiratory or aerobic endurance refers to the capacity of the heart, lungs and blood to carry and deliver oxygen throughout the body.

Throughout this article I will make repeated reference to VO2 max so let me explain that this term refers to the maximal rate of oxygen uptake during exercise. It is typically expressed in milliliters per kilogram of body weight per minute. To give you a rough idea of what VO2 max represents here are some figures according to the YMCA and ACSM standards: The average value of VO2 max for the population is 40 ml/kg/min. Figures between 50-60 are considered Very Good while figures above 60 are considered exceptional. Olympic caliber runners typically achieve 80 ml/kg/min and Olympic caliber cyclists and swimmers achieve 75 ml/kg/min. It should be noted that the above figures represent male athletes. The equivalent figures for female athletes are typically between 10-15% lower.

Lets start out by discussing Cardiorespiratory endurance more commonly known as Aerobic endurance. As already mentioned, Aerobic endurance is directly related to the amount of Oxygen that can be extracted from the environment and delivered throughout the body. Therefore, improvements in VO2 max should be noted as the athlete's aerobic endurance improves. Improvements in Aerobic endurance and VO2 max are directly related to the frequency and duration of training. VO2 max can normally be improved anywhere from 10-15% although in some rare cases improvements up to 30% have been observed. However, the 30% improvements have been observed in people whose overall rate of conditioning was very low before starting an exercise program, in other words these were people who were in a low level of fitness and who had never been involved in exercise before.

When it comes to designing an exercise program with the intention of increasing aerobic endurance and VO2 max, the total time of exercise plays a much more important role than the intensity and duration alone. In other words, a trainee who exercises for 40 minutes at a lower intensity will obtain the same results as a trainee who exercises for only 20 minutes but with much higher intensity. However, it should be mentioned that since most people use aerobic exercise as a vehicle towards reducing body fat, duration of less than 12 minutes are not recommended as they do not promote substantial fat loss. I will not expand into this further here since I have already discussed the subject further in another article titled "Optimizing Aerobic Training for Maximum Fat Loss" which you can find in my "Articles" page. Therefore, programs emphasizing moderate intensity training with duration between 20-40 minutes are recommended for most adults for the purposes of increasing Aerobic endurance. In addition, training at a moderate intensity has the added benefit of reducing the chances of injury, or other more severe and dangerous side effects. As far as what constitutes moderate intensity, the ACSM suggests that the minimal training intensity threshold for improvement in VO2 max is approximately 55-65% of the maximum Heart Rate HRmax (Maximum Heart Rate equals 220 minus your age). More advanced and experienced athletes can train up to 75% of their HRmax but only if they have developed the ability to tolerate it through previous training.

Keep in mind that this article is focused on Training for increases in Aerobic Endurance. Therefore, the principles mentioned here are NOT suitable for optimum fat loss. Individuals who exercise aerobically with the goal of losing fat should adjust their aerobic workouts particularly the duration which should be no more than 25 minutes long. In addition, such people should also use resistance training for increasing their metabolic rate. The combination of aerobic exercise in duration of no more than 20 minutes and resistance training is the optimal recipe for fat reduction. Aerobic exercise longer than 20 minutes may actually be counterproductive as far as fat loss is concerned.

Interval Training can also be highly beneficial to increases in Aerobic ability and VO2 max. Internal Training simply consists of short higher intensity exercise bouts alternated with rest or relief periods of mild to light exercise. Interval Training allows the trainee to exercise at a higher intensity than he or she could sustain if exercising continuously. However, Interval Training is suitable only for intermediate and higher level athletes. An example of Interval Training for a more advanced runner would be sprinting 45 to 50 meters followed by jogging for 55 to 60 meters and repeating this pattern until a distance of 2-3 miles is covered.

Another factor in Aerobic endurance concerns the frequency of the exercise. Studies have shown that Aerobic training 3 times a week offers optimal VO2 max development with frequencies up to 5 times a week being appropriate only for very advanced competitive athletes. For the general population and Fitness enthusiasts 3 times a week is the optimal frequency of training for Aerobic endurance.

To summarize the above, in order to increase Aerobic endurance the trainee should be involved in an aerobic activity such as Cycling, Running or a typical Spinning class 3 times per week for 20-40 minutes of moderate training which would allow him or her to maintain a Heart rate of 65% of HRmax. More advanced and experienced athletes can train up to 75% and can also use Interval training following the principles outlined above.

Let me explain another terminology that I will be using from now on, that of the Lactic Acid. When an athlete undergoes intensive training a point is reached where the specific muscle which has been exercised experiences increased fatigue and eventually a feeling of "burning" sensation. This is due to the accumulation of Lactic Acid which is actually a byproduct of anaerobic metabolism as I have discussed in some of my other articles. If after this point an athlete continues training by reducing the intensity of exercise, he or she will eventually (after 10 minutes) will enter another phase of training where another kind of metabolic process begins and which is called aerobic metabolism. During this phase no Lactic Acid is produced but because the previous Anaerobic phase still works in the background (although significantly minimized) a small amount of Lactic acid is still produced although not enough to fatigue the muscles and make them "burn". However, if the athlete raises his or her intensity level again to the previous level, there will be a point where Lactic Acid will again start being produced at a high level. This point is called Anaerobic Threshold.

The significance of Anaerobic Threshold in endurance training is paramount. That is because training at intensities that correspond to the Anaerobic threshold is the most effective way to increase endurance. We should note here that we are referring to sports high in aerobic capacity and not to anaerobic ones such as weight training. It is not possible to repeat the same muscle movement for 10 minutes continuously during weight training in order to experience aerobic metabolism. Other muscles will have to come into play during different exercises and that will not allow to develop endurance for specific muscles or muscle groups. Therefore weight training is not recommended for development of endurance. Sports high in Aerobic capacity such as running, hurdles, cycling, or swimming should be used for this purpose.

Keep in mind that pushing too much and training above the Anaerobic Threshold can have the exact opposite effects to endurance. Overzealous Fitness enthusiasts should exercise self control and avoid pushing too much otherwise they will obtain the opposite of what they wish to achieve.

Another reason that training at the Anaerobic Threshold increases endurance is that it requires contractions of both Fast twitch and Slow twitch muscle fibers in muscle groups. As a result, the Aerobic capacity of both muscle groups is improved whereas lower intensity would affect only the Slow twitch muscle fibers and higher intensity would affect only the Fast twitch muscle fibers. So try to train at the Anaerobic threshold for maximum endurance development. It should be mentioned here that the most accurate way to determine the anaerobic threshold is through blood lactate measurement which is normally not available to the average athlete. So training slightly below the point where muscle fatigue occurs and a "burning" sensation starts developing after at least 10 minutes of training is the closest approximation we can make to Anaerobic Threshold.

Before closing, I would again caution that the above principles concerning VO2 max and endurance should not be applied without appropriate medical clearance and without supervision by an experienced Personal trainer or coach otherwise such exercise can be potentially dangerous. Always perform cardiovascular exercise under the guidance of a specialist and after obtaining medical clearance form your physician.

Train Smart, Train Efficiently!!