Elsevier

Progress in Cardiovascular Diseases

Volume 70, January–February 2022, Pages 73-83
Progress in Cardiovascular Diseases

The effects of high-intensity interval training, Nordic walking and moderate-to-vigorous intensity continuous training on functional capacity, depression and quality of life in patients with coronary artery disease enrolled in cardiac rehabilitation: A randomized controlled trial (CRX study)

https://doi.org/10.1016/j.pcad.2021.07.002Get rights and content

Abstract

Background

Coronary artery disease (CAD) patients undergoing revascularization procedures often experience ongoing, diminished functional capacity, high rates of depression and markedly low quality of life (QoL). In CAD patients, studies have demonstrated that high-intensity interval training (HIIT) is superior to traditional moderate-to-vigorous intensity continuous training (MICT) for improving functional capacity, whereas no differences between Nordic walking (NW) and MICT have been observed. Mental health is equally as important as physical health, yet few studies have examined the impact of HIIT and NW on depression and QoL. The purpose of this randomized controlled trial (RCT) was to compare the effects of 12 weeks of HIIT, NW and MICT on functional capacity in CAD patients. The effects on depression severity, brain-derived neurotrophic factor (BDNF) and QoL were also examined.

Methods

CAD patients who underwent coronary revascularization procedures were randomly assigned to: (1) HIIT (4 × 4-min of high-intensity work periods at 85%–95% peak heart rate [HR]), (2) NW (resting HR [RHR] + 20–40 bpm), or (3) MICT (RHR + 20–40 bpm) twice weekly for 12 weeks. Functional capacity (six-min walk test [6MWT]), depression (Beck Depression Inventory-II [BDI-II]), BDNF (from a blood sample), and general (Short-Form 36 [SF-36]) and disease-specific (HeartQoL) QoL were measured at baseline and follow-up. Linear mixed-effects models for repeated measures were used to test the effects of time, group and time × group interactions.

Results

N = 135 CAD patients (aged 61 ± 7 years; male: 85%) participated. A significant time × group interaction (p = 0.042) showed greater increases in 6MWT distance (m) for NW (77.2 ± 60.9) than HIIT (51.4 ± 47.8) and MICT (48.3 ± 47.3). BDI-II significantly improved (HIIT: −1.4 ± 3.7, NW: −1.6 ± 4.0, MICT: −2.3 ± 6.0 points, main effect of time: p < 0.001) whereas BDNF concentrations did not change (HIIT: -2.5 ± 9.6, NW: -0.4 ± 7.7, MICT: −1.2 ± 6.4 ng/mL, main effect of time: p > 0.05). Significant improvements in SF-36 and HeartQoL values were observed (main effects of time: p < 0.05). HIIT, NW and MICT participants attended 17.7 ± 7.5, 18.3 ± 8.0 and 16.1 ± 7.3 of the 24 exercise sessions, respectively (p = 0.387).

Conclusions

All exercise programmes (HIIT, NW, MICT) were well attended, safe and beneficial in improving physical and mental health for CAD patients. NW was, however, statistically and clinically superior in increasing functional capacity, a predictor of future cardiovascular events.

Section snippets

Alphabetical list of abbreviations

6MWT, six-min walk testBDI-II, Beck Depression Inventory-II
BDNF, brain-derived neurotrophic factorBMI, body mass index
CABG, coronary artery bypass graft surgeryCAD, coronary artery disease
CONSORT, consolidated standards of reporting trialsCI, confidence interval
CR, cardiac rehabilitationCV, coefficient of variation
CVD, cardiovascular diseaseGXT, graded exercise test
HIIT, high-intensity interval trainingHR, heart rate
MCID, minimal clinically important differenceMI, myocardial

Study design

This single-centre, parallel-group, RCT was conducted at the University of Ottawa Heart Institute (UOHI), a tertiary care cardiovascular institute. This study was registered with ClinicalTrials.gov (NCT02765568) and carried out in accordance with the consolidated standards of reporting trials (CONSORT) and template for intervention description and replication (TIDieR) checklist.19 The protocol was approved by the Ottawa Health Science Network Research Ethics Board (protocol #: 20160127-01H).

Recruitment

Functional capacity

Functional capacity was assessed using a 6MWT on a measured indoor track at baseline and follow-up.24 Patients were instructed to walk as far as possible for 6 min but not to run or jog. At 2, 3, and 4 min of the 6MWT, patients were provided with standardized encouragement and informed of the time remaining. Total walking distance was measured in meters. The measures were performed in duplicate; the average was used for statistical analyses. A suggested minimal clinically important difference

Results

Of the 1222 patients who were screened, 135 were eligible and consented to participate; a total of 43, 43 and 44 patients were randomized to HIIT, NW and MICT, respectively (see Fig. 1). Patients' demographics, anthropometrics, medical conditions and medications are presented in Table 1. Most patients were male and identified, on average, as being overweight or obese, and normotensive (many due to medical management). Most were taking statins, acetylsalicylic acid, β-blockers, anti-platelets,

Discussion

The physical and mental health benefits of traditional CR involving MICT are well established for patients with CAD.35 This RCT examined the efficacy of alternative exercise interventions (i.e. HIIT and NW) for improving functional capacity, depression severity, BDNF concentrations and QoL in patients with CAD who recently underwent coronary revascularization procedures. Contrary to our hypothesis, a significantly greater increase in functional capacity was achieved following NW when compared

Conclusion

The findings from this RCT reveal that NW facilitated greater improvements in functional capacity, an important predictor of future cardiovascular events,8 when compared to HIIT and MICT in patients with CAD. All exercise modalities produced significant, beneficial changes in functional capacity and improved depression severity and QoL. These offerings were well attended and safe. Depending on space, equipment, personnel (e.g. expertise, experience in NW instruction) and patient preference, CR

Sources of funding

This investigator initiated research was supported by the Innovations Fund of the Alternate Funding Plan for the Academic Health Sciences Centres of the Ministry of Ontario (PIs: Pipe, Reed) and Heart and Stroke Foundation of Canada (PI: Reid).

Declaration of Competing Interest

The authors declare they have no conflicts of interests.

Acknowledgments

We would like to thank the patients, CR staff and Anna Clarke, Christie Cole, Dr. Daniele Chirico, Kyle Scott, Brenna Czajkowski, Rachelle Beanlands, Janet Wilson, Aaron Brautigam and Yannick MacMillan for their contributions to this research.

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