ABSTRACT
ABSTRACT Objective: The present study investigated the time needed to achieve a steady state for an accurate assessment of resting energy expenditure (REE) in adolescents with healthy weight and obesity. Materials and methods: Thirty adolescents aged 12-17 years were assigned to a group with healthy weight (GHW; n = 12, body mass index [BMI] 22.5 ± 3.6 kg/m2) and another group with obesity (GO; n = 18, BMI 34.1 ± 5.2 kg/m2). Participants underwent test-retest reliability of REE assessment as follows: a) 24 h of abstention from physical exercise, soft drinks, or caffeine; b) fasting for ~12 h; c) acclimation period of 10 min; d) 30-min assessment in a supine position. Results and discussion: A significant change occurred during the 30 min in REE. Significant differences existed between consecutive means until the 20th and 25th min for the GHW and GO, respectively. Although significant differences between trials 1 and 2 were detected during the first 5-10 min of assessment, the REE for each 5-min time point exhibited high test-retest reliability across trials in both groups (intraclass correlation coefficients range 0.79-0.99). Conclusion: The following recommendations are provided to promote accurate assessment of REE among adolescents: a) initiate the REE assessment with 10 min of acclimation to decrease restlessness; b) determine REE for a minimum of 20 min if healthy weight and 25 min if obesity; c) determine REE for a further 5 min, with the average of this last 5 min of REE data being regarded as the REE.
ABSTRACT
Abstract Aim: Spinal cord injury (SCI) is associated with changes in cardiac autonomic control, that can be evaluated by heart rate variability (HRV), for which the electrocardiogram (ECG) is the gold standard. However, the use of ECG is limited to laboratory environments, and new tools are needed for this purpose and that can be applied in the routine monitoring of individuals with SCI. The present study aimed to investigate the validity of the Polar V800 heart rate monitor in assessing the cardiac autonomic control of individuals with SCI. Methods: Nineteen adult men with SCI (paraplegia n = 10; 44.5 ± 8.5 years and tetraplegia n = 9; 34.4 ± 7.5 years) participated in this cross-sectional study. The participants remained in the sitting position at rest for 10 min for the acquisition of the ECG and Polar V800 signals. The last 5-min window was used to count the beat-by-beat R-R interval series and then calculate the HRV indices (linear methods in the time and frequency domains). The study subgroups were compared, and the validity of the measurements generated with a heart rate monitor was determined using the intraclass correlation coefficient (ICC2,1) and Bland-Altman graphs. Results: Agreement analyses for the R-R intervals, SDNN, rMSSD, PNN50, SD1, LF, HF, and LF: HF ratio tended to show reliability ranging from acceptable to excellent (ICC = 0.579-0.990; P = 0.043-0.001) and acceptably narrow limits of agreement within both the group with tetraplegia and the group with paraplegia. Conclusion: The Polar V800 heart rate monitor is a valid instrument for assessing HRV in individuals with paraplegia and tetraplegia.