Eric B. Taylor

This study is still in the process of completion. The following gives an overview of the study and its purpose. Permission has been received from the coaching staff of the Brigham Young University men=s cross country team to use its athletes as subjects given their consent. It is expected that the study will be completed by October of 2000.

The purpose of this study is to determine if track interval workouts with shorter intervals and shorter recoveries compared to longer intervals and longer recoveries produce lower peak lactate levels while keeping velocity, total work time and volume, and total recovery time constant.

Interval training is crucial to the success of middle and long distance runners because it develops the oxidative capacity of fast twitch muscle fibers. Motor units are recruited according to a size force relationship with larger motors units being recruited when higher contractile forces are required (1). Running at high velocities requires that one can maintain the recruitment of a significant pool of fast twitch motor units. If the fast twitch motor units being recruited at a certain velocity do not have the oxidative capacity to meet the metabolic demands placed upon them via aerobic pathways, then they will quickly fatigue thus requiring the recruitment of more anaerobic, less fatigue resistant fibers. The increased reliance on anaerobic metabolism results in reduced muscle and blood pH causing a decline in muscle force production and running velocity.

Fast twitch motor units must be recruited in training in order to develop their oxidative capacity. This is accomplished by interval training. However, athletes encounter the same obstacle in interval training as is encountered in racingCan increased reliance on anaerobic metabolism that may reduce the quality of the workout. It has been suggested that the low pH which is associated with high intensity workouts may contribute to muscle damage (2). Athletes find they need longer recovery times from lactate intensive workouts. Thus, these types of workouts cannot be performed with high frequency without an increased risk of overtraining.

The challenge presented to coaches and athletes is to develop the oxidative capacity of fast twitch motor units while avoiding high levels of lactic acid and the resultant low blood and muscle pH. It is the intent of this study to show that athletes may decrease the amount of lactate accumulation during interval workouts, without changing the total volume or the time necessary to complete the workout, by decreasing interval distances and recovery times. By keeping lactate accumulation lower during high velocity interval sessions, athletes may be able to complete workouts with higher total interval volume and repeat these workouts more frequently. This may lead to better development of fast twitch motor units and an improved ability to sustain high velocities during competition.

All subjects will complete two different interval workouts. Both workouts will take approximately 20 minutes to complete. The workouts will be separated by one week. Both will have a total of 9 minutes and 4 seconds of running (contingent upon the subjects running the specified pace) at the same velocity equal to 68 seconds per 400 meters while covering a total distance of 3200 meters, and will have a total of 6 minutes of walking recovery periods in between intervals. The workouts will be differentiated by the length of the intervals and recovery periods.. The longer interval workout (LI) will consist of 4 x 800 in 136 seconds (2:16) with 120 second (2:00) recovery periods. The shorter interval workout (SI) will consist of 8 x 400 in 68 seconds (1:08) with 51 second recoveries. Athletes will complete a non-strenuous running warm-up prior to engaging in the interval sessions.

For both workouts, blood will be sampled to measure peak blood lactate levels. Subjects will also be asked to rate the difficulty of each workout using the Borg scale for perceived exertion.

It is expected that the workout utilizing longer intervals will cause subjects to produce higher peak lactate levels and that subjects will also perceive it to be more difficult. The results of this study used in combination with possible follow up studies may provide information that will help athletes and coaches design superior training programs.

References

• Sale DG. Influence of exercise and training on motor unit activation. Exerc Sport Sci Rev 1987;15:95-151
• Armstrong RB. Initial events in exercise-induced muscular injury. Med Sci Sports Exerc. 1990;22:429-435