Validation Of The Cybex Arc Trainer Estimation Of Energy Expenditure

Abstract

PURPOSE: Elliptical machine exercise has grown in popularity in the fitness community. Despite the popularity of the Cybex Arc Trainer, (AT) which utilizes a unique arc motion unlike other elliptical machines, little is known about the validity of the AT console display of energy expenditure (EE). The purpose of this study was to examine the accuracy of the AT estimation of EE during a 30-minute moderate intensity workout. METHODS: Thirteen participants (5 normal-weight, 8 overweight) were fitted with the Oxycon Mobile (OXY), a portable indirect calorimeter system. Resting heart rate was used to calculate heart rate reserve, (HRR) an individual characterization of workout intensity. To maintain a moderate intensity throughout the 30-minute bout, participants were instructed to change the resistance level to yield a rating of perceived exertion of 12-13, while maintaining stride rate at 114 ± 5 strides per min.Criterion EE measured via the OXY was compared to EE values on the AT console display at the end of the workout. Linear mixed effects models and correlations were used to examine differences in EE between the AT and OXY and the relationship between EE OXY and EE AT. RESULTS: The AT significantly overestimated EE compared to the OXY (NW: 12.4%; OW: 18.0%). Correlations between OXY and AT EE ranged from r = 0.96 to 0.97 for NW and OW groups, respectively. No differences were observed in % HRR between groups. CONCLUSIONS: Although correlations between OXY and AT EE were high, AT consistently overestimated EE. Additionally, the EE overestimation was larger for the overweight group. These results indicate that the AT EE display is inaccurate. Therefore, users do not receive correct EE feedback. This will affect user ability to achieve desired EE goals, and over-time this discrepancy may have a substantial impact on weight-loss management. Fitness professionals should consider these results when prescribing AT exercise in physical activity interventions.