Energy Expenditure, Intensity, and Perceived Effort in Recreational Functional Training

Background: Functional training (FT) has become popular and seems to provoke health benefits. However, there are unsubstantiated claims regarding energy expenditure (EE) vs. weight-loss and cardiorespiratory improvements linked to FT. Objective: This study quantified the EE and intensity during FT performed in a conventional fitness center. Additionally, data of FT and moderate continuous walking (WLK) were compared. Methods: Healthy individuals with no previous experience with FT [n = 25, 11 males/14 females, 38.8 ± 9.3 years; 73.9 ± 13.8 Kg; 168.5 ± 8.5 cm; 26.0 ± 4.5 Kg/m2; 16 overweight (BMI >25 Kg/m2)] performed three FT sessions interspersed with 48 h (two familiarization, one assessment). The circuit included 4 rounds of 12 exercises performed at all-out intensity for 20 s with 1-min intervals between rounds. WLK was performed for 25 min with intensity corresponding to scores 3-5 on Borg CR-10 Scale. Outcomes were EE (kcal), movement counts estimated by triaxial accelerometry, heart rate reserve (%HRR), and rate of perceived exertion (RPE). Results: On average, FT sessions lasted 24 min and EE ranged between 124 and 292 kcal (188 ± 41 kcal), corresponding to 5-8 METs (6.1 ± 0.6 METs), and 70-80%HRR (74 ± 8%). Accelerometry (counts/min) showed that vigorous predominated over moderate intensity during FT and WLK (p = .01), with similar EE. The relative intensity and RPE were higher in FT vs. WLK (74% vs. 55%HRR and Borg 5-8 vs. 3-5, respectively; p < .0001). Conclusion: FT and WLK elicited EE consistent with recommendations to reduce cardiovascular disease risk, but only FT achieved relative intensities compatible with cardiorespiratory improvement. FT should be considered an option in health-oriented exercise programs for the general population.