Acute physiological responses to interval and continuous training in ILD

Introduction/Aim Exercise training in pulmonary rehabilitation is an effective intervention for people with interstitial lung disease (ILD). However, a large proportion of those who participate are not attaining its benefit. Alternative training strategies to the current method of continuous exercise at moderate intensity may prove more effective in people with ILD. This study aims to compare the acute physiological effects of high intensity interval training (HIIT), moderate intensity interval training (MIIT) and moderate intensity continuous training (MICT) in people with ILD. Methods Six participants with ILD performed in random order three different cycle training protocols until volitional exhaustion, symptom limitation or desaturation (SpO2 < 80%) after performance of a baseline cardiopulmonary exercise test. Training protocols were thirty second intervals alternating 100% peak work rate with unloaded cycling (HIIT), two minute intervals alternating between 80% and 40% peak work rate (MIIT) and continuous exercise at 60% peak work rate (MICT). The cycle tests were separated by a minimum of one week. Heart rate (HR), blood pressure, SpO2, oxygen uptake (VO2), minute ventilation (VE) and Borg scores for dyspnoea and fatigue were recorded. Results The MIIT protocol resulted in significantly higher VO2, HR and VE (Table 1) when compared to other exercise protocols. During MIIT, participants exercised at a higher percentage of VO2peak (Table 1) and were associated with more dyspnoea, leg fatigue and oxygen desaturation, although this was not statistically significant. There was no significant difference between HIIT and MICT protocols for the VO2, VE, HR, SpO2, leg fatigue or dyspnoea. However, HIIT was associated with a smaller volume of work. Conclusion Using HIIT for people with ILD may allow for a greater training load with similar levels of breathlessness and desaturation to traditional endurance training. Whereas MIIT appears to result in a greater physiological challenge suggesting it is a less effective training strategy.