Aerobic interval training and moderate-to-vigorous intensity continuous training are associated with sex-specific improvements in psychological health in patients with heart disease

Cardiovascular disease (CVD) is a global pandemic and is the leading cause of morbidity and mortality in women.1 More than 50% of women at 40 years of age living free of known disease are expected to develop CVD in their lifetime.2 Following a cardiac event, women experience more adverse psychological and physical consequences than men, which negatively impact the recovery trajectory following an event.3 Cardiac rehabilitation (CR) affords significant opportunities to improve psychological and physical health in those with coronary artery disease (CAD). The number of women participating in CR more than doubled between 1996 and 2010.4 However, women remain less likely than men to enroll in or adhere to CR programmes. Women frequently report lack of time and interest in conventional exercise programming as deterrents to CR participation.5 Aerobic interval training (AIT) has emerged as an alternative exercise training paradigm in CR. When compared with traditional moderate-to-vigorous intensity continuous exercise (MICE), AIT has been shown to produce similar or greater improvements in psychological6 and physical7 health outcomes with reduced time commitment. These findings are, however, based on studies involving exclusively women6 or predominantly men.7 It was unknown if AIT and MICE would produce differential effects on women and men. Therefore, we conducted a retrospective analysis to compare the changes in psychological and physical health indicators associated with two exercise modalities (i.e. AIT and MICE) on women and men. Approval for the study was obtained from the Ottawa Health Sciences Network Research Ethics Board (protocol no. 20170721-01H). Participants completed an on-site CR programme led by physiotherapists at the University of Ottawa Heart Institute between January 2014 and September 2018. Details of the AIT and MICE programmes have been described elsewhere.6 Participants enrolled in the AIT programme attended sessions twice weekly for 8 weeks following a 2-week familiarisation period. Each session consisted of a modified Norwegian AIT protocol: (a) 10-minute warm-up at 60–70% peak heart rate (HRpeak); (b) four 4-minute high-intensity intervals at 85–95% HRpeak and a rating of perceived exertion (RPE) (6–20 scale) of 15–17 (hard to very hard) interspersed with 3-minute low-intensity intervals at 60–70% HRpeak and an RPE of 11–13 (light to somewhat hard); and, (c) 10-minute cool-down at 60–70% HRpeak. Each session was 45 minutes in duration. Participants enrolled in MICE attended sessions twice weekly for 8 weeks. Participants exercised at 70–85% HRpeak (i.e. moderate-to-vigorous intensity) or an RPE of 12–15 (moderate to hard). Each session was 60 minutes in duration and included a warm-up and cool-down. Research assistants retrieved participants’ demographic and relevant medical information. Height, body mass, waist circumference, resting blood pressure and heart rate were measured using standardised procedures by CR staff. Body mass index (BMI) was calculated (kg/m2). Anxiety and depression were assessed using the hospital anxiety and depression scale (HADS), a 14-item self-report scale which yields separate anxiety and depression scores.8 The minimal clinically important difference (MCID) for the HADS scores is 1.7 points or greater.9 These psychological and physical data were collected at baseline and following completion of the CR programme. Baseline characteristics were compared using factorial analysis of variance (ANOVA) (women vs. men by AIT vs. MICE) for continuous variables and chi-square analyses for categorical variables. Baseline and follow-up psychological and physical measures were compared within each exercise modality by paired t-tests. To assess the interaction between sex and exercise modality, we performed 2 × 2 analysis of covariance (ANCOVA) (women vs. men by AIT vs. MICE) on changes in psychological and physical health measures. The analyses were adjusted for baseline age, body mass, prescribed medications, cardiac conditions and baseline measures of the dependent variables. Analyses were performed using SPSS for Windows (version 25; IBM Corp, Armonk, NY, USA). P < 0.05 was considered statistically significant. A total of 120 participants, 60 in AIT (30 women and 30 men) and 60 in MICE (30 women and 30 men) completed CR (Table 1). At baseline, a smaller proportion of women were diagnosed with CAD (P < 0.001) and were less frequently prescribed anti-platelet (P = 0.013) and anti-dyslipidemic (P < 0.001) medications. Both AIT and MICE significantly reduced anxiety (–1.7 ± 3.2 and –2.1 ± 2.8 points, respectively; both P < 0.001) and depression severity (–1.5 ± 2.6 points, P < 0.001 and –0.7 ± 2.7 points, P = 0.040, respectively), as well as body mass, BMI and waist circumference (all P < 0.05). ANCOVA showed a significant sex-by-exercise modality interaction effect on changes in anxiety severity (P = 0.036), revealing a greater reduction following AIT versus MICE (–1.7 ± 2.7 vs. –0.4 ± 2.8 points) in women, whereas a greater reduction following MICE versus AIT (–3.2 ± 2.9 vs. –2.3 ± 2.9 points) in men (Table 1). Baseline and changes in psychological and physical health indicators. Age, psychological and physical health indicators are presented as mean (SD). Changes represent follow-up minus baseline values. ACE: angiotensin-converting enzyme; AF: atrial fibrillation; AIT: aerobic interval training; BMI: body mass index; BP: blood pressure; CAD: coronary artery disease; HF: heart failure; MICE: moderate-to-vigorous intensity continuous exercise. Baseline and changes in psychological and physical health indicators. Age, psychological and physical health indicators are presented as mean (SD). Changes represent follow-up minus baseline values. ACE: angiotensin-converting enzyme; AF: atrial fibrillation; AIT: aerobic interval training; BMI: body mass index; BP: blood pressure; CAD: coronary artery disease; HF: heart failure; MICE: moderate-to-vigorous intensity continuous exercise. This was the first study to examine the interplay between sex and exercise modality on psychological and physical health in patients participating in a CR programme. The primary finding was that, while AIT and MICE were associated with statistically significant and clinically meaningful improvements in anxiety severity, the degree of changes associated with AIT and MICE were sex dependent. In women, the mean improvement in anxiety severity reached the MCID (i.e. –1.7 points)9 following AIT but not MICE. In men, while the reductions reached the MCID following AIT and MICE, they were more prominent following MICE. We also found that both AIT and MICE were associated with significant reductions in body mass, waist circumference and depression severity independent of sex. The efficacy of AIT in improving psychological and physical health indicators has been established in studies which predominantly involved men. Our results suggest that AIT affords an alternative opportunity to improve BMI, waist circumference and depression, and augment reductions in anxiety severity in women, but not in men. Women recovering from a cardiac event are less active when compared with men,10 and increased anxiety severity predicts non-adherence to interventions11 and adverse outcomes following cardiovascular events.12 Clinically meaningful reductions in anxiety severity in women following AIT may, therefore, contribute to fewer secondary cardiovascular events in women. With more women participating in CR programmes,4 our finding highlights an important alternative exercise strategy to target the psychological health of women. The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: TT was supported by the Jan & Ian Craig Cardiac Prevention and Rehabilitation Endowed Fellowship from the University of Ottawa Heart Institute. JLR was supported by a Canadian Institutes of Health Research (CIHR) New Investigator Award in Clinical Rehabilitation.