Abstract

Study Objectives: i) To describe and compare, in COPD patients, the acute physiological, symptomatic, and affective responses to continuous training at a high intensity (CTHI), continuous training at the ventilatory threshold (CTVT), and interval training (IT); ii) To examine the nature and degree of association between acute measures of intensity and adherence to a 12-week exercise-training program; iii) To investigate whether the relationship between acute responses and adherence is mediated or moderated by affect/vigor.

Methods: Thirty-five COPD patients (FEV1 = 60.2 ± 15.8 % predicted) underwent baseline assessments, were randomly assigned to CTHI, CTVT, or IT, were monitored during a single exercise-training bout, and subsequently took part in a 12-week exercise-training program. Physiological, symptomatic, and affective responses were measured using a portable system, the PANAS and GVA questionnaires, and the Borg scale; respectively. Adherence was defined as the percent time spent within the target heart rate range for attended sessions.

Results: In comparison to CTHI, CTVT was associated with lower levels of RER, HR, and RR, whereas IT was associated with higher levels of VE, VE/MVV, RR, and a greater drop in SpO2. Affective state generally improved from pre- to post-exercise, with increases in positive affect (F=9.74, p<0.001) and decreases in negative affect (F=6.43, p=0.005). The CTVT group experienced a greater dip in global affect mid-exercise compared to CTHI (p=0.04), yet had a higher level of end-exercise alertness compared to CTHI (p=0.01) and IT (p=0.02). The IT group reported the lowest levels of post-exercise alertness (p=0.04 versus CTHI and p=0.02 versus CTVT), and significantly lower 12-week adherence rates (F=6.69, p=0.004). Mean exercise VO2 (r=-0.466, p=0.007) and end-exercise global vigor (r=0.420, p=0.017) were most strongly correlated with adherence. The moderation model was supported, where end-exercise global vigor moderated the relationship between VO2 and adherence (β=2.74, t (32)=2.32, p=0.03).

Conclusion: Compared to CTHI, CTVT was associated with less physiological strain, and greater end-exercise alertness, while IT was associated with slightly more physiological strain, lower post-exercise alertness, and lower 12-week adherence rates. VO2 and end-exercise global vigor were most strongly associated with adherence. Acute end-exercise vigor was found to moderate the relationship between acute VO2 and adherence.