The feasibility of implementing high-intensity interval training in cardiac rehabilitation settings: a retrospective analysis

Rates of compliance and adherence to high-intensity interval training: a systematic review and Meta-analyses

BACKGROUND

To determine rates of compliance (i.e., supervised intervention attendance) and adherence (i.e., unsupervised physical activity completion) to high-intensity interval training (HIIT) among insufficiently active adults and adults with a medical condition, and determine whether compliance and adherence rates were different between HIIT and moderate-intensity continuous training (MICT).

METHODS

Articles on adults in a HIIT intervention and who were either insufficiently active or had a medical condition were included. MEDLINE, EMBASE, PsychINFO, SPORTDiscus, CINAHL, and Web of Science were searched. Article screening and data extraction were completed by two independent reviewers. Risk of bias was assessed using RoB 2.0 or ROBINS-I. Meta-analyses were conducted to discern differences in compliance and adherence between HIIT vs. MICT. Sensitivity analyses, publication bias, sub-group analyses, and quality appraisal were conducted for each meta-analysis.

RESULTS

One hundred eighty-eight unique studies were included (n = 8928 participants). Compliance to HIIT interventions averaged 89.4% (SD:11.8%), while adherence to HIIT averaged 63% (SD: 21.1%). Compliance and adherence to MICT averaged 92.5% (SD:10.6%) and 68.2% (SD:16.2%), respectively. Based on 65 studies included in the meta-analysis, compliance rates were not different between supervised HIIT and MICT interventions [Hedge's g = 0.015 (95%CI: - 0.088-0.118), p = .78]. Results were robust and low risk of publication bias was detected. No differences were detected based on sub-group analyses comparing medical conditions or risk of bias of studies. Quality of the evidence was rated as moderate over concerns in the directness of the evidence. Based on 10 studies, adherence rates were not different between unsupervised HIIT and MICT interventions [Hedge's g = - 0.313 (95%CI: - 0.681-0.056), p = .096]. Sub-group analysis points to differences in adherence rates dependent on the method of outcome measurement. Adherence results should be interpreted with caution due to very low quality of evidence.

CONCLUSIONS

Compliance to HIIT and MICT was high among insufficiently active adults and adults with a medical condition. Adherence to HIIT and MICT was relatively moderate, although there was high heterogeneity and very low quality of evidence. Further research should take into consideration exercise protocols employed, methods of outcome measurement, and measurement timepoints.

REGISTRATION

This review was registered in the PROSPERO database and given the identifier CRD42019103313.

Extraordinary claims in the literature on high-intensity interval training (HIIT): III. Critical analysis of four foundational arguments from an interdisciplinary lens

Kinesiology aspires to be an integrated, interdisciplinary field that studies human movement from multiple perspectives. However, the main societal deliverables of the field, namely exercise prescriptions and physical activity recommendations, still reflect fragmentation, placing more emphasis on physiological outcomes than on behavioral and other considerations. Recently, researchers have called for the introduction of High-Intensity Interval Training (HIIT) to the domain of public health, based on the argument that HIIT can maximize fitness and health benefits for a fraction of the time recommended by the prevailing model of physical activity in public-health guidelines. Here, we show that an unintended side-effect of arguments underpinning the implementation of HIIT in the domain of public health might have been the exacerbation of segmentation. To highlight the value of interdisciplinarity, four foundational claims in support of HIIT are critiqued by tapping into cognate literatures: (1) the primary reason people do not exercise is lack of time, (2) HIIT is relevant to public health, (3) HIIT is being proposed as merely another option, so there is no basis for controversy, and (4) HIIT is safe and well tolerated. These claims are contradicted by credible lines of evidence. To improve the accuracy and effectiveness of its public claims, kinesiology should remain committed to the ideals of integration and interdisciplinarity.

Exercise training reduces circulating cytokines in male patients with coronary artery disease and type 2 diabetes: A pilot study

Low-grade inflammation is central to coronary artery disease (CAD) and type 2 diabetes (T2D) and is reduced by exercise training. The objective of this study was to compare the anti-inflammatory potential of moderate-to-vigorous intensity continuous training (MICT) and high-intensity interval training (HIIT) in patients with CAD with or without T2D. The design and setting of this study is based on a secondary analysis of registered randomized clinical trial NCT02765568. Male patients with CAD were randomly assigned to either MICT or HIIT, with subgroups divided according to T2D status (non-T2D-HIIT n = 14 and non-T2D-MICT n = 13; T2D-HIIT n = 6 and T2D-MICT n = 5). The intervention was a 12-week cardiovascular rehabilitation program consisting of either MICT or HIIT (twice weekly sessions) and circulating cytokines measured pre- and post-training as inflammatory markers. The co-occurrence of CAD and T2D was associated with increased plasma IL-8 (p = 0.0331). There was an interaction between T2D and the effect of the training interventions on plasma FGF21 (p = 0.0368) and IL-6 (p = 0.0385), which were further reduced in the T2D groups. An interaction between T2D, training modalities, and the effect of time (p = 0.0415) was detected for SPARC, with HIIT increasing circulating concentrations in the control group, while lowering them in the T2D group, and the inverse occurring with MICT. The interventions also reduced plasma FGF21 (p = 0.0030), IL-6 (p = 0.0101), IL-8 (p = 0.0087), IL-10 (p < 0.0001), and IL-18 (p = 0.0009) irrespective of training modality or T2D status. HIIT and MICT resulted in similar reductions in circulating cytokines known to be increased in the context of low-grade inflammation in CAD patients, an effect more pronounced in patients with T2D for FGF21 and IL-6.

Predictors of adherence of enhanced external counterpulsation in patients with coronary heart disease after discharge: A mixed-methods study

Background

Although enhanced external counter pulsation (EECP) has been included in the cardiac rehabilitation prescription for coronary heart disease (CHD) in China, because the total treatment duration of a course of EECP is 36-36 h, the average hospital stay of CHD patients is short, and the adherence after discharge remains unclear. The purpose of this study is to investigate the adherence to EECP in CHD patients after discharge, and analyze the related influencing factors.

Methods

A retrospective mixed method study combining qualitative and quantitative methods. Quantitative component included CHD patients who had received EECP treatment between March 2020 and August 2021. The qualitative component included in-depth interviews with patients who did not adhere to EECP after discharge. Binary Logistic regression was used to analyze the predictors of EECP adherence after discharge. In-depth interviews with patients were conducted to explore the reasons for dropping out of the EECP after discharge.

Results

Among 1,304 patients, only 24.23% adhered to EECP treatment after discharge. Binary logistic regression results showed that patients with disease duration < 2 years (OR = 3.13, 95%CI: 2.31-4.24), high school or below (OR = 2.81, 95%CI: 1.98-4.01), distance between residence and hospital more than 20km (OR = 2.08, 95%CI: 1.47-2.96), age over 60 (OR = 2.00, 95%CI: 1.46-2.74), female (OR = 1.64, 95%CI: 1.78-2.29), and angina pectoris (OR = 1.65, 95%CI: 1.16-2.34) were more likely to not adhere to EECP treatment after discharge. However, patients with monthly family income over 8000¥ (OR = 0.46, 95%CI: 0.28-0.75) were more likely to adhere to EECP treatment after discharge than those with household monthly income below 4,000¥. In the qualitative results, the reasons why patients do not adhere to EECP after discharge mainly include insufficient understanding, restricted objective conditions and psychosocial factors.

Conclusions

The adherence of CHD patients to EECP treatment after discharge was poor. It is necessary to develop effective intervention measures, such as brochures or videos to improve patients' understanding of the importance of adherence to EECP treatment after discharge. In addition, offering EECP treatment during off-hours and weekends may also improve adherence in more young patients.

A case series of acute responses to high-intensity interval training in four males with permanent atrial fibrillation

Background

Atrial fibrillation (AF) is a serious medical condition and a burgeoning patient population. Chronic exercise training, including high-intensity interval training (HIIT), has been shown to improve symptoms and quality of life in patients with AF. Yet, the acute responses to HIIT in this population remain understudied, leaving clinicians and patients hesitant about prescribing and engaging in high-intensity exercise, respectively.

Case summary

This case series describes acute exercise responses [i.e. power output, heart rate (HR), blood pressure (BP), ratings of perceived exertion (RPE), symptoms] to 10 weeks (3 days/week) of HIIT. Participants were four white males (58–80 years old) with permanent AF, co-morbidities (diabetes, coronary artery disease, Parkinson’s disease), and physical limitations. The increases in HR and BP during HIIT were modest across all participants, regardless of age and medication use. Differences in RPE were observed; the oldest participant perceived the sessions as more challenging despite a lower HR response. All patients complied with the HIIT prescription of 80–100% of peak power output by week 4. No adverse events were reported.

Discussion

Patients’ concerns regarding high-intensity exercise may discourage them from participating in HIIT, our results demonstrated no abnormal HR or BP (e.g. hypotension) responses during HIIT or cool-down. These findings align with the typical exercise responses noted in other cardiovascular populations. Notwithstanding the high metabolic demands of HIIT, male patients with permanent AF tolerated HIIT without problem. Further investigation of HIIT as an approach to enable those with AF to recover physical capacity and minimize symptomatology is warranted.

Exercise training in paediatric congenital heart disease: fit for purpose?

Exercise and physical activity (PA) have been shown to be effective, safe and feasible in both healthy children and children with congenital heart disease (CHD). However, implementing exercise training as an intervention is still not routine in children with CHD despite considerable evidence of health benefits and well-being. Understanding how children with CHD can safely participate in exercise can boost participation in PA and subsequently reduce inactivity-related diseases. Home-based exercise intervention, with the use of personal wearable activity trackers, and high-intensity interval training have been beneficial in adults' cardiac rehabilitation programmes. However, these remain underutilised in paediatric care. Therefore, the aims of this narrative review were to synthesise prescribed exercise interventions in children with CHD, identify possible limitation to exercise training prescription and provide an overview on how to best integrate exercise intervention effectively for this population into daily practice.

Sex and Age Differences in Anxiety and Depression Levels Before and After Aerobic Interval Training in Cardiac Rehabilitation

PURPOSE

The objective of this study was to investigate sex and age differences in anxiety and depression among patients with cardiovascular disease at baseline and following aerobic interval training (AIT)-based cardiac rehabilitation (CR) and secondarily to compare dropout rates between sexes and age groups.

METHODS

Participants were younger (≤44 yr), middle-aged (45-64 yr), and older adults (≥65 yr). The AIT protocol consisted of: 4 × 4-min of high-intensity work periods at 85-95% peak heart rate (HR) interspersed with 3 min of lower-intensity intervals at 60-70% peak HR, twice weekly for 10 wk. Anxiety and depression were assessed using the Hospital Anxiety and Depression Scale at baseline and following CR.

RESULTS

At baseline, of 164 participants (32% female), 14 (35% female) were younger, 110 (33% female) were middle-aged, and 40 (30% female) were older. Older adults reported lower anxiety levels versus younger (4.4 ± 2.6 vs 7.8 ± 3.4 points, P = .008) and middle-aged adults (4.4 ± 2.6 vs 6.1 ± 3.6 points, P = .05). Baseline depression levels did not differ between age groups (P = .749). All age groups experienced a reduction in anxiety (younger =-2.67; middle-aged =-1.40; older =-0.85) and depression (younger =-1.50; middle-aged =-0.83; older =-0.70) levels following CR. Differences in dropout rates were observed between age groups (χ2[1] = 13.4, P = .001). Within each age group, 43% (female n = 2, male n = 4) of younger, 10% (female n = 8, male n = 3) of middle-aged, and 2.5% (female n = 0, male n = 1) of older participants dropped out.

CONCLUSIONS

Younger and middle-aged adults experience higher levels of anxiety upon entry into CR compared with older adults. Cardiac rehabilitation was associated with significant reductions in anxiety and depression severity, yet dropout rates were highest among younger adults.

High level physical activity in cardiac rehabilitation: Implications for exercise training and leisure-time pursuits

IMPORTANCE

Regular moderate-to-vigorous physical activity and increased levels of cardiorespiratory fitness (CRF) are widely promoted as cardioprotective measures in secondary prevention interventions.

OBSERVATIONS

A low level of CRF increases the risk of cardiovascular disease (CVD) to a greater extent than merely being physically inactive. An exercise capacity <5 metabolic equivalents (METs), generally corresponding to the bottom 20% of the fitness continuum, indicates a higher mortality group. Accordingly, a key objective in early cardiac rehabilitation (CR) is to increase the intensity of training to >3 METs, to empower patients to vacate this "high risk" group. Moreover, a "good" exercise capacity, expressed as peak METs, identifies individuals with a favorable long-term prognosis, regardless of the underlying extent of coronary disease. On the other hand, vigorous-to-high intensity physical activity, particularly when unaccustomed, and some competitive sports are associated with a greater incidence of acute cardiovascular events. Marathon and triathlon training/competition also have limited applicability and value in CR, are associated with acute cardiac events each year, and do not necessarily provide immunity to the development of or the progression of CVD. Furthermore, extreme endurance exercise regimens are associated with an increased incidence of atrial fibrillation and accelerated coronary artery calcification.

CONCLUSIONS AND RELEVANCE

High-intensity training offers a time-saving alternative to moderate intensity continuous training, as well as other potential advantages. Additional long-term studies assessing safety, adherence, and morbidity and mortality are required before high-intensity CR training can be more widely recommended, especially in previously sedentary patients with known or suspected CVD exercising in non-medically supervised settings.

The Effects of High-Intensity Interval Training (HIIT) on Fall Risk Factors in Healthy Older Adults: A Systematic Review

High-intensity interval training (HIIT) improves functional capacity, muscle power and physical performance in older adults with and without comorbidities. The aim of this study was to explore the effectiveness of HIIT as a method for reducing major fall risk factors (balance, muscle strength and physical activity) in older adults. A systematic literature search was conducted following the PRISMA guidelines. A computerized search was conducted using electronic databases (PubMed, CINAHL, Cochrane Library, APA PsycInfo, Web of Science, Scopus, PEDro, and AgeLine) published up to July 2021. Eleven papers (9 studies) of moderate quality (mean of 5.5 in Pedro scale) involving 328 healthy older adults met the inclusion criteria. Studies were characterized by high heterogeneity in terms of methodology, HIIT modality and protocol, subject characteristics, and outcome measures. Results indicate that HIIT cannot be recommended as a single modality for fall prevention in older adults due to insufficient data and no consensus among the studies. HIIT appears to be a safe and well-tolerated supplement to proven fall prevention programs, due to its effects on lower limb strength reflected in functional performance tests, and on dynamic balance and subjective balance perception. However, caution is warranted following HIIT, especially after the first session, due to possible temporary instability.

High Intensity Interval Training (HIIT) as a Potential Countermeasure for Phenotypic Characteristics of Sarcopenia: A Scoping Review

Background: Sarcopenia is defined as a progressive and generalized loss of skeletal muscle quantity and function associated predominantly with aging. Physical activity appears the most promising intervention to attenuate sarcopenia, yet physical activity guidelines are rarely met. In recent years high intensity interval training (HIIT) has garnered interested in athletic populations, clinical populations, and general population alike. There is emerging evidence of the efficacy of HIIT in the young old (i.e. seventh decade of life), yet data concerning the oldest old (i.e., ninth decade of life onwards), and those diagnosed with sarcopenic are sparse.

Objectives: In this scoping review of the literature, we aggregated information regarding HIIT as a potential intervention to attenuate phenotypic characteristics of sarcopenia.

Eligibility Criteria: Original investigations concerning the impact of HIIT on muscle function, muscle quantity or quality, and physical performance in older individuals (mean age ≥60 years of age) were considered.

Sources of Evidence: Five electronic databases (Medline, EMBASE, Web of Science, Scopus, and the Cochrane Central Register of Controlled Trials [CENTRAL]) were searched.

Methods: A scoping review was conducted using the Arksey and O'Malley methodological framework (2005). Review selection and characterization were performed by two independent reviewers using pretested forms.

Results: Authors reviewed 1,063 titles and abstracts for inclusion with 74 selected for full text review. Thirty-two studies were analyzed. Twenty-seven studies had a mean participant age in the 60s, two in the 70s, and three in the 80s. There were 20 studies which examined the effect of HIIT on muscle function, 22 which examined muscle quantity, and 12 which examined physical performance. HIIT was generally effective in Improving muscle function and physical performance compared to non-exercised controls, moderate intensity continuous training, or pre-HIIT (study design-dependent), with more ambiguity concerning muscle quantity.

Conclusions: Most studies presented herein utilized outcome measures defined by the European Working Group on Sarcopenia in Older People (EWGSOP). However, there are too few studies investigating any form of HIIT in the oldest old (i.e., ≥80 years of age), or those already sarcopenic. Therefore, more intervention studies are needed in this population.

Cardiac Rehabilitation of Patients with Acute ST-Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention in a Han Population in Northern China: A Prospective Cohort Study

Background

Cardiac rehabilitation (CR) has been associated with improved cardiac function in cardiovascular diseases. Our aim was to explore the factors associated with cardiac function and CR.

Methods

This prospective cohort study had 473 STEMI patients admitted for primary percutaneous coronary intervention (PCI) who were divided into a CR group (group A, n = 104) and a non-CR group (group B, n = 369) based on whether they could complete CR. Patients’ clinical features, such as age, hyperlipidemia, family history of premature coronary heart disease (FHPCHD), smoking history, body mass index (BMI, kg/m²), number of diseased vessels, arrhythmia during PCI, N-terminal pro–B-type natriuretic peptide (NT-proBNP), left ventricular ejection fraction (LVEF) and major adverse cardiac events (MACEs) at 6 months after PCI were compared. Then, the clinical characteristics of patients were further analyzed according to those with MACEs (n = 78) and those without MACEs (n = 395).

Results

After CR of 6 months, NT-proBNP levels (p = 0.027), 6-MWD (meter, P = 0.000), LVEF (P = 0.000) were significantly improved in group A compared to group B, but not for SMWA (P = 0.875). Multivariate analysis indicated that even though patients in group A (OR 3.06, 95% CI 1.132–8.274, p = 0.03) have a higher incidence of hyperlipidemia, their MACEs (OR 0.191, 95% CI 0.038–0.961, p = 0.05) at 6 months were significantly lower than in group B, mainly because the average patient low age (<65 years, OR 0.917, 95% CI 0.859–0.979, p = 0.01) and significant improvement of 6-MWD (OR 7.999, 95% CI 4.342–14.737, P = 0.00) and the LVEF at 6 months (OR 1.112, 95% CI 1.072–1.154, p = 0.00). Further analysis based on the MACES outcomes showed that there were 6 factors associated with the occurrence of MACEs, they were age >65 years (OR 1.032, 95% CI 1.009–1.009, p = 0.007), smoking history (OR 0.485, 95% CI 0.238–0.989, p = 0.046), education level (OR 2.646, 95% CI 1.370–5.108, p = 0.004), 6-MWD (OR 1.688, 95% CI 1.104–2.811, p = 0.044), LVEF (OR 0.958, 95% CI 0.926–0.991, p = 0.013) and CR (OR 6.271, 95% CI 2.236–17.590, p = 0.000).

Conclusion

CR, including exercise rehabilitation, is a beneficial option to reduce MACEs in STEMI patients treated with primary PCI.

Sex differences in physical and mental health following high-intensity interval training in adults with cardiovascular disease who completed cardiac rehabilitation

This pre-post study examined sex-differences in peak aerobic power (V̇O2peak) and physical- and mental-health outcomes in adults with cardiovascular disease who completed high-intensity interval training (HIIT)-based cardiac rehabilitation. HIIT consisted of 25 minutes of alternating higher- (4×4 minutes 85-95% heart rate peak (HRpeak)) and lower- (3×3 minutes 60-70% HRpeak) intensity intervals twice weekly for 10 weeks. V̇O2peak estimated from a graded exercise test using the American College of Sports Medicine equation, body mass index (BMI), waist circumference, blood pressure, blood biomarkers and anxiety and depression were assessed at baseline and follow-up. Linear mixed-effects models for repeated measures were performed to examine differences over time between sexes. Of 140 participants (mean ± standard deviation: 58 ± 9 years), 40 were female. Improvements in V̇O2peak did not differ between sexes (interaction: p = 0.273, females: 28.4 ± 6.4 to 30.9 ± 7.6; males: 34.3 ± 6.3 to 37.4 ± 6.0 mL/kg/min). None of the time by sex interactions were significant. Significant main effects of time showed reductions in waist circumference, triglycerides, low-density lipoprotein (LDL), total cholesterol (TC)/high-density lipoprotein (HDL) and anxiety, and increases in V̇O2peak and HDL from baseline to follow-up. Significant main effects of sex revealed smaller V̇O2peak, BMI and waist circumference, and higher LDL, TC and HDL in females than males. HIIT led to similar improvements in estimated V̇O2peak (females: 8.8%, males: 9.0%) and additional health outcomes between sexes. Novelty: HIIT-based cardiac rehabilitation led to similar improvements in estimated V̇O2peak and other physical and mental health outcomes between sexes. The number of sessions attended was high (>70%) and did not differ by sex. Both sexes showed good compliance with the exercise protocol (HR target).

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)

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.

Risk Factors of Atrial Arrhythmia in Patients With Liver Cirrhosis: A Retrospective Study

Background and Objectives: Liver cirrhosis is known to be associated with atrial arrhythmia. However, the risk factors for atrial arrhythmia in patients with liver cirrhosis remain unclear. This retrospective study aimed to investigate the risk factors for atrial arrhythmia in patients with liver cirrhosis. Methods: In the present study, we collected data from 135 patients with liver cirrhosis who were admitted to the Department of Gastroenterology at Shanghai Tongji Hospital. We examined the clinical information recorded, with the aim of identifying the risk factors for atrial arrhythmia in patients with liver cirrhosis. Multiple logistic regression analysis was used to screen for significant factors differentiating liver cirrhosis patients with atrial arrhythmia from those without atrial arrhythmia. Results: The data showed that there were seven significantly different factors that distinguished the group with atrial arrhythmia from the group without atrial arrhythmia. The seven factors were age, white blood cell count (WBC), albumin (ALB), serum Na⁺, B-type natriuretic peptide (BNP), ascites, and Child-Pugh score. The results of multivariate logistic regression analysis suggested that age (β = 0.094, OR = 1.098, 95% CI 1.039-1.161, P = 0.001) and ascites (β =1.354, OR = 3.874, 95% CI 1.202-12.483, P = 0.023) were significantly associated with atrial arrhythmia. Conclusion: In the present study, age and ascites were confirmed to be risk factors associated with atrial arrhythmia in patients with liver cirrhosis.

Strengthening the Case for Cluster Set Resistance Training in Aged and Clinical Settings: Emerging Evidence, Proposed Benefits and Suggestions

Resistance training (RT) is a fundamental component of exercise prescription aimed at improving overall health and function. RT techniques such as cluster set (CS) configurations, characterized by additional short intra-set or inter-repetition rest intervals, have been shown to maintain acute muscular force, velocity, and 'power' outputs across a RT session, and facilitate positive longer-term neuromuscular adaptations. However, to date CS have mainly been explored from a human performance perspective despite potential for application in health and clinical exercise settings. Therefore, this current opinion piece aims to highlight emerging evidence and provide a rationale for why CS may be an advantageous RT technique for older adults, and across several neurological, neuromuscular, cardiovascular and pulmonary settings. Specifically, CS may minimize acute fatigue and adverse physiologic responses, improve patient tolerance of RT and promote functional adaptations (i.e., force, velocity, and power). Moreover, we propose that CS may be a particularly useful exercise rehabilitation technique where injury or illness, persistent fatigue, weakness and dysfunction exist. We further suggest that CS offer an alternative RT strategy that can be easily implemented alongside existing exercise/rehabilitation programs requiring no extra cost, minimal upskilling and/or time commitment for the patient and professional. In light of the emerging evidence and likely efficacy in clinical exercise practice, future research should move toward further direct investigation of CS-based RT in a variety of adverse health conditions and across the lifespan given the already demonstrated benefits in healthy populations.

Adherence to High-Intensity Interval Training in Cardiac Rehabilitation: A REVIEW AND RECOMMENDATIONS

PURPOSE

High-intensity interval training (HIIT) is gaining popularity as a training approach for patients attending cardiac rehabilitation (CR). While the literature has focused on the efficacy of HIIT for improving cardiorespiratory fitness (CRF), particularly when compared with moderate intensity exercise, less emphasis has been placed on adherence to HIIT. The aim of this review was to summarize the current literature regarding adherence to HIIT in CR patients with coronary artery disease.

REVIEW METHODS

A review identified 36 studies investigating HIIT in CR patients with coronary artery disease. Methods and data were extracted for exercise or training adherence (to attendance, intensity, and duration), feasibility of protocols, and CRF. The review summarizes reporting of adherence; adherence to HIIT and comparator/s; the influence of adherence on changes in CRF; and feasibility of HIIT.

SUMMARY

Adherence to the attendance of HIIT sessions was high and comparable with moderate-intensity exercise. However, adherence to the intensity and duration of HIIT was variable and underreported, which has implications for determining the treatment effect of the exercise interventions being compared. Furthermore, additional research is needed to investigate the utility of home-based HIIT and long-term adherence to HIIT following supervised programs. This review provides recommendations for researchers in the measurement and reporting of adherence to HIIT and other exercise interventions to facilitate a sufficient and consistent approach for future studies. This article also highlights strategies for clinicians to improve adherence, feasibility, and enjoyment of HIIT for their patients.

Sex Differences in Cardiometabolic Health Indicators after HIIT in Patients with Coronary Artery Disease

PURPOSE

Cardiorespiratory fitness (CRF) is an independent predictor of mortality, and females typically achieve smaller improvements in CRF than males after exercise-based cardiac rehabilitation. High-intensity interval training (HIIT) has been shown to produce superior improvements in CRF than traditional cardiac rehabilitation, but the sex differences are unknown. The purpose of this systematic review and meta-analysis was to evaluate sex differences for changes in CRF and cardiometabolic health indicators after HIIT in adults with coronary artery disease (CAD).

METHODS AND RESULTS

A systemic search of five electronic databases for studies examining the effect of HIIT on measured CRF and cardiometabolic health indicators in adults with CAD was performed. Data (published and unpublished) from 14 studies were included in the meta-analyses with approximately eightfold greater male than female participation (n = 836 vs n = 103). Males with CAD achieved a near-significant absolute improvement in CRF (mean difference [MD] = 1.07, 95% confidence interval [CI] = -0.08 to 2.23 mL·kg-1⋅min-1, P = 0.07) after HIIT when compared with control; there were insufficient data to conduct such an analysis in females. Significantly smaller improvements in CRF were experienced by females than males (MD = -1.10, 95% CI = -2.08 to -0.12 mL·kg-1⋅min-1, P = 0.03); there was no sex difference for the relative (percentage) change in CRF after HIIT. Females achieved significantly smaller reductions in body mass index (MD = -0.25, 95% CI = -0.03 to -0.47 kg·m-2, P = 0.02) and fasting blood glucose (MD = -0.38, 95% CI = -0.05 to -0.72, P = 0.03); no sex differences were observed for other cardiometabolic health indicators.

CONCLUSION

There are no sex differences for relative improvements in CRF after HIIT; however, females are greatly underrepresented in trials. Future studies should increase female participation and perform sex-based analyses to determine sex-specific outcomes following HIIT.