Nathan F. Meier

Comparison of Consumer and Research Monitors under Semistructured Settings.

PURPOSE This study evaluated the relative validity of different consumer and research activity monitors during semistructured periods of sedentary activity, aerobic exercise, and resistance exercise. METHODS Fifty-two (28 male and 24 female) participants age 18-65 yr performed 20 min of self-selected sedentary activity, 25 min of aerobic exercise, and 25 min of resistance exercise, with 5 min of rest between each activity. Each participant wore five wrist-worn consumer monitors [Fitbit Flex, Jawbone Up24, Misfit Shine (MS), Nike+ Fuelband SE (NFS), and Polar Loop] and two research monitors [ActiGraph GT3X+ on the waist and BodyMedia Core (BMC) on the arm] while being concurrently monitored with Oxycon Mobile (OM), a portable metabolic measuring system. Energy expenditure (EE) on different activity sessions was measured by OM and estimated by all monitors. RESULTS Mean absolute percent error (MAPE) values for the full 80-min protocol ranged from 15.3% (BMC) to 30.4% (MS). EE estimates from ActiGraph GT3X+ were found to be equivalent to those from OM (± 10% equivalence zone, 285.1-348.5). Correlations between OM and the various monitors were generally high (ranged between 0.71 and 0.90). Three monitors had MAPE values lower than 20% for sedentary activity: BMC (15.7%), MS (18.2%), and NFS (20.0%). Two monitors had MAPE values lower than 20% for aerobic exercise: BMC (17.2%) and NFS (18.5%). None of the monitors had MAPE values lower than 25% for resistance exercise. CONCLUSION Overall, the research monitors and Fitbit Flex, Jawbone Up24, and NFS provided reasonably accurate total EE estimates at the individual level. However, larger error was evident for individual activities, especially resistance exercise. Further research is needed to examine these monitors across various activities and intensities as well as under real-world conditions.

Walking versus biofeedback: a comparison of acute interventions for stressed students

ABSTRACT Background: High rates of stress-related problems in college students and low utilization of treatment options demonstrate the need for effective stress-reducing interventions that can be self-regulated. This study compared the effect of brief paced-breathing with biofeedback and exercise interventions on heart rate variability, state anxiety and affect. Methods: Students (n = 32) with high levels of perceived stress completed three 10-min interventions on separate days: paced-breathing with biofeedback (Biofeedback), a self-paced walk (Exercise), and an attention control condition of quiet studying (Quiet Study). Anxiety and affect were measured before (Pre), immediately after (Post0) and 15 mins after (Post15) the intervention. Heart rate variability was measured pre- and post-intervention using electrocardiogram. Results: Biofeedback reduced anxiety more than the exercise condition (Pre to Post0: Biofeedback d = −0.48, Exercise d = −0.13). Secondly, Exercise temporarily increased energy (Pre to Post0: d = 0.67), whereas Biofeedback temporarily increased calmness (Pre to Post0: d = 0.51). All conditions significantly increased total heart rate variability (p < .05). Conclusions: Biofeedback and Exercise interventions improved emotional states in high-stress college students, but the type of change observed (i.e. energizing, calming or anxiety reducing) depended upon the condition.