Date of Award

5-2021

Degree Name

Doctor of Philosophy

Department

Education and Human Development

First Advisor

Dr. Nicholas J. Hanson

Second Advisor

Dr. Timothy J. Michael

Third Advisor

Dr. Michael G. Miller

Fourth Advisor

Dr. Ya Zhang

Keywords

Aerobic exercise, cardiovascular health, vigorous exercise, V02max, fat-mass, fat free mass

Abstract

Background: A growing body of literature indicates that women, in comparison to men, report significantly more barriers to exercise, often times related to perceived lack of time due to their social roles (e.g. family responsibility, childcare). Therefore, it has been considered that exercise programs that require less time commitments would be more attractive for women to alleviate this concern. Objective: This review was conducted to comprehensively understand the present literature surrounding women and such a time-efficient protocol: high intensity interval training (HIIT). The primary aim was to determine the impact of HIIT on both cardiorespiratory fitness (CRF) and body composition. The secondary aim was to identify what variables, if any, influence the effect of HIIT on changes in CRF and body composition. Methods: A database search was conducted in MEDLINE (PubMed), CENTRAL (Cochrane), and ESCO (SPORTdiscus) to obtain all peer-reviewed publications up until November 2020. Studies were included if HIIT protocols were aerobic-based, a minimum of two weeks in duration, participants were between the ages of 18-65 years and free from cardiovascular, metabolic, or renal disease and cancers. Comparisons were made for changes in maximal or peak oxygen consumption (VO2max or VO2peak), fat mass (FM), fat-free mass (FFM), and body fat percentage (BF%). Results: 41 studies were included in this review, involving a total of 628 female subjects who were predominantly younger (582 subjects between ages 18-35 years) and overweight (body mass index ranging from 20.3-35.7 kg-m-2). Exercise intervention duration ranged from 2-15 weeks (7.8±3.7 weeks), utilizing between 2-5 sessions (3.1±0.4 visits) per week. Of the 37 studies with CRF as an outcome measures, 34 reported improvements. 35 studies reported pre- and post-intervention assessments surrounding body composition. 14 determined significant improvements in BF% and 12 studies reported a significant decrease in FM, six showed significant increases in FFM. Conclusion: It is suggested that HIIT can significantly improve CRF in women, irrespective of age, training status, BMI, and training frequency. However, exercise intervention duration, in conjunction with the appropriate intensity of exercise may influence the improvements. HIIT interventions that are shorter in duration (≤7 week) should consider utilizing intensities >100% VO2max (supramaximal) to elicit improvements in CRF. Intensities ranging from 85-95% VO2max are sufficient to augment CRF in interventions exceeding 7 weeks. The effect of HIIT on body composition is less clear. Excess post-exercise oxygen consumption (EPOC) and energy expenditure greatly exceeding 1000 MET-minutes per week may account for reductions in FM. However, there is no guarantee that these reasons alone account for all reductions in FM. There were improvements in FFM across very few studies (n = 6). It is suggested that aerobic-based HIIT be supplemented with resistance training to generate superior improvements in FFM. Furthermore, lack of controlled diet across all studies makes it difficult to determine if caloric intake could account for any changes in body composition. While HIIT may be an effective and time-efficient protocol for women, future research should focus on ecological validity and women’s adherence to such vigorous training, specifically within non-athletic and sedentary subgroups.

Access Setting

Dissertation-Open Access

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