## 4 Discussion
Another study [32] reported 18% less perceived exertion with passive (sitting on a chair) recovery than with active (treadmill run at 50% maximal speed) recovery [32]. Although the results of the Borg scales (0 to 10 points: [33]; 6-20 points: [32]) are comparable to our fatigue perception because both are measures of subjective physical condition, the differences of the measurement characteristics could explain why there was no difference across the conditions in our study. The Borg scale matches a numeric scale with descriptions of exertion, asking subjects to indicate their exertion level, whereas our measurement simply asked subjects to place themselves between \"unfatigued\" and \"fatigued\" on a visual analogue scale. Measurements were also taken during exercise using the Borg scale and after exercise in our study. Since subjects in previous studies felt less exertion in the passive condition than those in the active condition [32; 33], providing different descriptions (e.g., fresh or recovered) or using a more detailed numeric scale may have produced a different result. Interestingly, blood lactate and fatigue perception values had a strong correlation in our study (r = 0.75, r\({}^{2}\) = 0.57). Thus, at least 57% of an individual's perceived fatigue can be explained by blood lactate and vice versa. However, fatigue perception returned to the pre-run level at 20 min postexercise (post-run 20 min)whereas blood lactate levels did not. This observation has several practical implications. First, people may feel complete recovery although their bodies are still in the process of physiological recovery. Second, a complete physiological recovery may be unnecessary for psychological (perceptual) recovery. Third, in addition to blood lactate, there could be other factors which contribute to the level of fatigue perception. A future study should examine the relationships between psychological, physiological, and athletic performance. Similarly, there were no changes in the circumferences of lower extremities at any time point. Given that a tape measure was used to obtain circumferences in many previous studies [34; 35; 36; 37], the measurement reproducibility in our study was strong (ICC value of 0.99 for between-session reliability in all measurements), measurement technique or errors were unlikely to contribute to the results. In fact, we did not even observe a circumference change at the post-run measurements, which could be explained by the exercise duration and mode (specific energy system). Previously reported postexercise extremity circumference was induced by resistance [34; 35] or endurance exercise [36; 37]. Therefore, an approximately 7-min all-out treadmill run may not have been sufficient to increase leg swelling. Exercise-induced transient hypertrophy, also known as \"the pump\", is thought to be caused by the accumulation of intracellular fluid from reactive hyperemia [38] or osmolytic activity [39]. In endurance activities, the expansion of extracellular volume [37] due to increased plasma volume and sodium retention [40] is thought to be responsible for oedemaous swelling. While we assumed that our intense treadmill run mostly used the combined energy system of anaerobic glycolysis, it produced neither of the physiological mechanisms, resulting in no circumference change. Because body fluid removal is an important facet of physical recovery, a future investigation should examine how the IBP strategy affects the increased circumference caused by either resistance or prolonged endurance exercise. Appendicular body composition analysis along with skinfold thickness would provide better accuracy in the assessment of exercise-induced anthropometric changes. There are several limitations and assumptions in our study that may benefit future research.