Using the 1km Challenge to test aerobic capacity and anaerobic threshold
A swimmer's anaerobic threshold is a useful tool for setting interval times for training swimmers, and the MSC 1km Challenge can be used to test aerobic capacity and determine a swimmer's anaerobic threshold. Repeating the 1km Challenge at a later date will help measure and track the improvement in aerobic capacity that a swimmer has made in the intervening training period.
Anaerobic threshold is the speed at which aerobic processes can no longer keep up with the recycling of the byproducts of anaerobic metabolism and acidosis begins. Anaerobic metabolism occurs below the anaerobic threshold but aerobic metabolism is able to recycle the byproducts as quickly as they are produced so they do not accumulate. Anaerobic threshold speed is therefore the maximum speed that a swimmer can sustain over long distances. If the swimmer exceeds their anaerobic threshold speed acidosis occurs, this is signaled by the sensation of the muscles "burning". As acidosis progresses it impairs muscle function, and actually damages the muscle tissues, forcing the swimmer to slow down.
Knowing a swimmer's anaerobic threshold pace is important in setting intervals because different systems will be stressed to different degrees depending on whether the pace is above or below anaerobic threshold pace. Basic Endurance Training should swum below the anaerobic threshold so that the aerobic system is stressed for longer periods as longer distances can be swum without acidosis. Threshold Endurance Training should be swum at anaerobic threshold speed and Overload Endurance Training should be swum at higher than anaerobic threshold speed. Without knowing a swimmer's anaerobic threshold speed you cannot assign intervals to ensure that the desired type of training occurs.
By conducting periodic 1km Challenge events you can monitor improvements in aerobic capacity and anaerobic threshold speed, giving feedback on training progression and interval adjustments, and swimmers will see tangible improvements to help maintain motivation.
Recently, Matsunami and colleagues (1999a) compared the accuracy of a number of test distances from 3,000m down to 600m for estimating the anaerobic threshold. Their criterion measure was a lactate step test that estimated the speed at which blood lactate began to accumulate in a linear manner. They reported that a test distance of 1,000m provided the closest relationship to the anaerobic threshold speed as predicted from the criterion measure. Consequently, they proposed that a 1,000m time trial could be used in place of a 2,000 or 3,000m time trial to evaluate changes in aerobic capacity and prescribe training speeds.
From Swimming Fastest, Earnest W. Maglischo, 2003, p569
Matsunami, M., M. Taguchi, A. Taimura, M. Suyama, M. Suga, S. Taba. 1999a. Relationship among different performance tests to estimate maximal aerobic swimming speed. Medicine and Science in Sports and Exercise 31 (Supplement 5): Abstract #376.
Maglischo goes on to express personal doubts about whether a T1000 would better predict anaerobic threshold than a T2000 or T3000, but states that in any case it is a good way to test improvement in aerobic capacity and anaerobic threshold.
To estimate aerobic threshold for training purposes just divide the 1km time by ten to get the anaerobic threshold pace per 100m.