gas exchange threshold, anaerobic threshold, ventilatory threshold, exercise physiology, Dmax, VO2max fitness test, exercise intensity, endurance testing, lactate threshold, metabolic cart, exercise testing, graded exercise test, fitness testing, endurance training, exercise test, cardiovascular fitness tests, oxygen uptake, aerobic threshold, endurance test, maximal oxygen uptake, maximum oxygen uptake, maximal oxygen consumption, ventilatory breakpoint, ventilatory equivalents, V-slope, Gaskill et al. 2001, Jones Molitoris 1984, Beaver et al. 1986, Orr et al. 1982, Cheng et al. 1992