A new perspective in pulmonary rehabilitation: anaerobic threshold as a discriminant in training

Exercise training is a mainstay of many pulmonary rehabilitation programmes. However, the physiologic basis for improved exercise tolerance is unclear. We hypothesized that since endurance training is known to reduce blood lactate at levels of work above the anaerobic threshold (AT), minute ventilation (VE) would also be lower. This might be an important benefit for the ventilatory-limited patient. We studied 10 normal subjects who performed 15 min of exercise at each of 4 work rates before and after 8 weeks of training. The lowest work rate was chosen to be below the AT; training produced a minimal decrease in VE (2.5 l.min-1). For the highest work rate, training produced a 4 mEq.l-1 decrease in lactate and a 37 l.min-1 decrease in VE. End-exercise VE reduction was well correlated with lactate reduction (r = 0.69). Seven men with chronic obstructive pulmonary disease (COPD) have also been studied. Each performed an incremental exercise test and two constant work rate tests (one above and one below AT) before and after an 8 week training period. Though responses were more variable than in normal subjects, training produced a reduced ventilatory requirement for exercise when blood lactate was reduced.