Driftline is presenting the Exercise Threshold System, a true breakthrough in exercise science. Human muscle consists of three major types of muscle fibers, i.e., slow oxidative fibers, fast oxidative/glycolytic fibers, and fast glycolytic fibers. With increasing exercise intensity, the muscle recruits progressively faster fibers and transitions are reflected in five evenly spaced exercise thresholds (T1 - T5).

T1 is named endurance threshold, since it reflects the ratio of slow, aerobic muscle fibers and determines the individual's aerobic endurance. T2 is named Critical threshold, since it is critical for endurance performance and coincides with this familiar scientific threshold. T5 is named Max speed threshold, since it represents the individual's absolute maximum speed.

Driftline's new endurance parameter scales between 0 - 100% and reflects the proportion of slow, aerobic muscle fibers. A high-endurance runner will get good mileage from glucose stores and produce competitive race times over long distances. In short, endurance is fuel preservation through muscle efficiency.

The speedometer above shows how endurance reflects the alignment of exercise thresholds. Use the endurance slider to explore the threshold alignment. Endurance is minimized when thresholds are in distal alignment (T1 equals zero) and maximized when they are in proximal alignment (T1 equals half of T5). The discovery of endurance is poised to become an important milestone in exercise physiology.

Maximum speed is one of two the major performance factors for running, the other being Endurance. Based on Driftline's principle of threshold alignment, the maximum speed is easily extrapolated, since it equals the highest of the five exercise thresholds (T5).

The speedometer above shows the threshold speed levels for the specific case of 50% endurance. The maximum speed is always fixed as the T5 threshold. You can use the Max speed slider to see how the other thresholds are directly related to the max speed. Driftline has discovered how to measure maximum running speed indirectly, based on a leisurely run.