Energy Expenditure and Intensity of Group-Based High-Intensity Functional Training: A Brief Report

Abstract

Background: High-intensity functional training (HIFT) may offer an attractive, time-efficient alternative to traditional aerobic exercise. However, limited information is available in the literature regarding HIFT meeting exercise guidelines for energy expenditure (improve health outcomes: ≥1000 kcal/wk; weight management: ≥2000 kcal/wk) and level of intensity (moderate: 3-6 metabolic equivalents [METs], vigorous: ≥6 METs) elicited by this approach. Thus, the primary aim was to objectively measure energy expenditure and intensity of HIFT sessions.

Methods: \Energy expenditure was assessed in 20 adults (18-50 y, 50% females). The HIFT session format included the following segments: warm-up (∼5 min), exercise (∼35 min), and cooldown (∼5 min). Participant oxygen consumption (COSMED, L/min and mL/kg/min), heart rate (Polar RS400), and physical activity (ActiGraph GT3X+) were collected in 15-second intervals. Average kcal per minute, METs, total kcal per session, and percent maximum heart rate (HRmax) were calculated.

Results: METs ranged from 5.5 to 11.6 for the complete session (including warm-up and cooldown). Participant's HRmax was ∼80% (range: 69%-100%). Average energy expenditure was ∼485 kcal per session (∼1400 kcal/wk). The vigorous-intensity exercise portion (∼35 min) contributed to 80% of total energy expenditure.

Conclusions: HIFT has the potential to meet the recommendations for exercise to improve health outcomes.

Trial registration: ClinicalTrials.gov NCT02526108.

Keywords: accelerometer; exercise; indirect calorimetry.

Figures

Figure 1 —

Percent maximum heart rate (minute-by-minute) by participants wearing the calorimeter versus other participants.

Figure 2 —

Individual variation in energy expenditure by sex.