The Importance of Oxidative Capacity and its Application with Power Athletes by Ben Peterson

Introduction

There is a commonly held misconception among strength and conditioning professionals that the energy systems of the body turn on in a pre-determined sequential order. Many have become accustomed to thinking only certain energy systems are used for certain sports, a classification usually based on the time a play or an event takes to complete.  Football is clearly anaerobic alactic because a play only lasts 4 seconds, a 200-meter sprint is anaerobic lactate specific because shifts last about 30 seconds. This belief has lead many to think that power athletes, such as football, hockey, and soccer players do not need to improve their oxidative capacity. This could not be further from the truth.

Oxidative capacity, also referred to as an athlete’s aerobic base, is an essential piece to the power athletes’ overall energy system puzzle. It plays a major role in phosphocreatine (PCr) recovery, glycogen storage, and contributes to the total energy expenditure in short anaerobic bursts, all of which improve athletic performance. The current ideology, that a power athlete’s oxidative capacity does not play an important role in sports, needs to change.

In addition, it is not enough to simply change the ideology behind the current views of oxidative training. The way in which coaches go about implementing programs to increase oxidative capacity must be refined. While the current trend of aerobic training on bikes, treadmills, and stairs may work for distance athletes, they will hinder performance for those competing in power sports. Taking a closer look at muscle fiber recruitment, rate of force development, and physiological results of high-intensity interval training (HIIT) on athletes, it becomes clear that the methods used to achieve an aerobic base are as critical as its development.

Review

The phosphocreatine (PCr) system is the fastest means for a power athlete to generate adenosine triphosphate (ATP), the energy source that runs the human body. When athletes exert maximal effort during a sporting event, their bodies will begin to break down PCr in an attempt to replenish the ATP that has been used. During the time PCr is being broken down, the body’s other energy sources pick up the slack, providing energy as a gap bridge (Gastin, P.B., 2001, p. 731) (This energy contribution from other sources was alluded to earlier and will be covered in the following paragraphs). The rate limiting factor in this process, however, is oxygen availability. According to Elliot, M.C.C.W., Wagner, P.P., & Chiu, L., (2007) an athlete’s diminished ability to process oxygen will slow the rate of PCr synthesis, ultimately slowing the rate of ATP production and athletic performance.

Another important benefit of improving an athletes oxidative capacity is increased glycogen storage. The repetitive depletion and repletion of glycogen stores in the body lead to a super-compensation effect in the muscle, allowing it to store more glycogen than before (Elliot, M.C.C.W., et al. 2007, p. 53). A physiological response typically associated with aerobic training, power athletes who can store more glycogen in their muscles have a clear advantage in anaerobic lactate sports. Elliot, M.C.C.W., (2007) points to this advantage in sports such as soccer, where numerous, repeated, high-intensity bouts of exertion take place throughout a match while maintaining a constant state of low aerobic activity.

While PCr repletion and glycogen storage are two key components of oxidative capacity, the most important link in the chain for power athletes is that the aerobic energy system contributes to energy expenditure during anaerobic activities. It is not a cut and dried sequence of activation like many believe. To the contrary, it is fully integrated power grid with all the components contributing, albeit at different rates, all at the same time. A review by Gastin, P.B., (2001) found that during repeated 6 second sprints on a bicycle, power output from sprint 1 to sprint 10 decreased by 27%. While this could be explained by a decrease in PCr repletion, the experiment also found a decline in anaerobic ATP utilization of 64%. With the anaerobic system operating at less than half its capacity, aerobic metabolism must have contributed in some way to maintain power output. While the actual percentage of aerobic contribution to anaerobic energy expenditure is widely debated, the fact that it contributes signifies its importance.

All athletes are not created equal. If they were, Adrian Peterson would be just as effective running the New York Marathon as he is on running the ball out of the backfield. This same idea must cary over to training power athletes to gain a better aerobic base. As study done by Izequierdo, M., Ibanez, J., Hakkinen, K., Kraemer, W.J., Ruesta, M., & Gorostiaga, E.M., (2004) found that the average power output of weightlifters was significantly higher (42-48%) than that of road cyclists. This observation held true even after power output was expressed relative to body weight.  Power athletes have a much higher proportion of Type IIx and Type IIa muscle fibers as compared to aerobic athletes and as a result, pound for pound, can generate more force.

Training an athlete for an aerobic base who is made up of predominately type IIx fiber with the same methods that would be used to train an athlete made up of predominately type I is illogical. This goes back to a basic foundation of the strength and conditioning profession: specific adaptions to imposed demands (SAID Principal). It is imperative that the training methods meet the demands of the sport.

Again, the method of how training is applied to a power athlete is just as important as acquiring an aerobic base itself. Conventional aerobic endurance training, according to Tanaka, H., & Swensen, T., (1998) has been associated with depressed vertical jumping ability in athletes. In power sports where the rate of force development is crucial to making cuts on a field, jumping high off the ground, or delivering a blow to an opponent, losing power is not an option. Similar studies have found that aerobic endurance training actually changes the physiology of the muscle, reducing muscle fiber size, rate of myofibril contractile properties, shortening velocity of type II fiber, and peak tension in all fiber types (Tanaka, H., & Swensen, T., 1998, p.193). The key is to find a method of training that trains type II muscle fiber, maximizes power output, and elicits the same effects as conventional aerobic training.

A study performed by Forbes, S.C., Slade, J.M., Meyer, R.A. (2008) discovered that PCr recovery time improved by 14% after high-intensity interval training with their test subjects. In short, they were able to increase the functional oxidative capacity of muscle without conventional aerobic training. By performing high-intensity intervals, the researchers managed to train type II muscle fiber, maintain power output, and get results similar to an athlete who had done conventional aerobic training. The method that best allows power athletes to improve their aerobic base without sacrificing power is high-intensity interval training (HIIT).

Discussion

The overarching problem in today’s sports model is that there is no off season. There is no extended period of time where athletes can take extended time off, come back, and slowly start building back up all the pieces that make them great athletes. As a result, coaches are forced to find methods to stack multiple training goals on top of one another within a single training block. It is ill-advised with a 12-week off season, such as baseball, to take 4 weeks and focus purely on aerobic conditioning.  It can be done, but at the expense of strength, power and speed.

To maximize a power athlete’s potential, methods such as HIIT must replace current trends where coaches lean towards long, steady state aerobic conditioning. While much of the research is still heavily debated, there is enough evidence that shows interval training improves oxidative capacity that a shift in methods must be made.

Future research needs to be done looking more specifically at the duration of the intervals being performed, as well as the rest taken in between bouts. It is likely that both of those times could be tailored for specific sports or events to maximize the output of the body’s energy system.

Conclusion

A power athlete is made up of a complicated, intricate network of multiple energy systems all working together for the same goal — meet the energy demands of the body. Many coaches try to compartmentalize these energy systems with rules, ranges and times, limiting their use and dictating their function. These imposed limits on energy system training have lead many to believe that an athlete only has to work on the specific energy system emphasized in their sport. And while that may be a convenient way to frame how the body uses energy and a simpler way to plan workouts, it is wrong. The truth is that every energy system contributes at every level in some way. Specifically when looking at the aerobic contribution to anaerobic athletes.

Increasing oxidative capacity in power athletes can drastically improve performance, if the methods used to improve that capacity also maximize power and speed. A good aerobic base will improve PCr recovery, glycogen stores in muscle, as well as aid in the contribution of energy needed during maximal efforts on the field. To maximize these results, an athlete should use HIIT to ensure they recruit type II muscle fiber. This ensures they maintain the rate of force development in the muscle.

Ultimately, an improved oxidative capacity allows the power athlete to do two things; play hard for longer periods of time and play hard more often with less rest. It dictates your motor. Making the right decisions when choosing how to condition your energy system is the difference between running like a mini-van or running like a mustang on the field.