The Dose-response Effects of High Intensity Functional Training on Metabolic Syndrome Risk Factors

This study aims to explore the dose effects of three weekly volumes of high-intensity functional training (HIFT) on apolipoprotein B (ApoB), triglyceride (TG) and cholesterol (CHOL) content of low-density lipoproteins (LDL), very low-density lipoproteins (VLDL), and high-density lipoproteins (HDL) particles, fasting insulin and glucose, glycosylated hemoglobin (HbA1c), and endothelial function after a 12-week training program. Secondarily, this study aims to also explore the subjective dose-responses of "exercise enjoyment" and "intention to continue" after this 12-week training program.

Background: Individuals with metabolic syndrome (MetS) are at a greater risk for developing atherosclerotic cardiovascular disease (ASCVD) than those without MetS, due to underlying endothelial dysfunction, dyslipidemia, and insulin resistance. Exercise is an effective primary and secondary prevention strategy for MetS, however less than 25% of adults meet the minimum stated public recommendations. Barriers often identified are lack of enjoyment and lack of time. High intensity functional training (HIFT), a time efficient modality of exercise, has shown some potential to elicit positive affectivity, and elicit increased fitness and improved glucose metabolism. However, the effects of HIFT on dyslipidemia and endothelial dysfunction have not been explored, nor have the effects been explored in a population with MetS. Additionally, no studies have investigated the minimal dose of HIFT per week to see clinically meaningful changes in cardiometabolic health. The purpose of this study is to: 1) determine the dose-response effect of HIFT on blood lipids, insulin resistance, and endothelial function, and 2) determine the dose-response effect of HIFT on body composition, fitness, and perceived enjoyment and intention to continue the exercise.

Methods/design: In this randomized, dose-response trial, participants will undergo a 12-week HIFT intervention of either 1 day/week, 2 days/week, or 3 days/week of supervised, progressive exercise. Outcomes assessed at baseline and post-intervention will be multiple cardiometabolic markers, and fitness. Additionally, the participant's affective response will be measured after the intervention.

Discussion: The findings of this research will provide evidence on the minimal dose of HIFT per week to see clinically meaningful improvements in the risk factors of MetS, as well as whether this modality is likely to mitigate the barriers to exercise. If an effective dose of HIFT per week is determined and if this modality is perceived positively, it may provide exercise specialists and health care providers a tool to prevent and treat MetS.

Eligibility Criteria:
Inclusion Criteria:

* Physically Inactive (\< 30 min/day, 3 days/wk, for 3 months of moderate intensity exercise)
* Possess at least 3 of the following 5 risk factors defining metabolic syndrome (MetS): waist circumference ≥ 102cm (men) or ≥ 88cm (women), resting blood pressure ≥ 130/85, HDL-C ≤ 40mg/dl (men) or ≤ 50mg/dl (women), fasting triglycerides ≥ 150mg/dl, and fasting blood glucose ≥ 100mg/dl.

Exclusion Criteria:

* Diagnosed heart, lung, kidney, liver, pancreatic or neurological disease
* Pregnant or plan to become pregnant
* Medical or orthopedic conditions preventing participation in exercise