e., log transformed and multiplied by 20). Statistical analysis Means and standard deviations were determined for the raw and Ponatinib TNKS2 ln transformed ECG derived RMSSD values. The ithlete? and corrected criterion RMSSD recordings were compared with a paired samples T-test and Pearson product correlation. In addition, the constant error (CE) and the standard error of estimate (SEE) were calculated for the ithlete?. Bland-Altman plots were also formed to identify the limits of agreement for ithlete? (Bland and Altman, 1986). A priori statistical significance was set at p < 0.05. All statistical analysis was completed using the SPSS version 16.0. Results The raw and ln transformed RMSSD values from the 55 sec ECG strip were 89.0 �� 54.2 ms and 4.3 �� 0.6, respectively. The corrected criterion RMSSD values were 86.
23 �� 12.3, while the ithlete? provided values of 86.19 �� 12.3. These values were not significantly different (p = 0.91) and the effect size was negligible (partial eta2 = 0.001). The correlation between the criterion and ithlete? was near perfect (r = 0.99, p < 0.001, Figure 1). Compared to the criterion, the ithlete? revealed a SEE of 1.47. The Bland Altman plot showed that the LOA ranged from 2.57 below to 2.63 above the CE of ?0.03 (Figure 2). Figure 1 Scatterplot representing the relationship between the Criterion and ithlete? The middle line represents the line of regression, while the two outside dashed lines represent the standard error of the estimate. Figure 2 Bland-Altman plot comparing the corrected RMSSD estimated by the ithlete? with the criterion.
The solid line represents the mean bias while the two outside dashed lines represent the 95% limits of agreement. Discussion The aim of this study was to determine the validity of the ithlete? HRV smart phone application in comparison to laboratory derived RMSSD data. The mobile system functions via a wireless heart rate monitor, an analog chest strap and a portable ECG receiver that inserts into the headphone slot of a smart phone or tablet device. The heart rate monitor detects cardiac cycles at the moistened conduction site and sends this information via radio transmission to the receiver. The receiver processes R wave data and automatically performs a calculation providing the lnRMSSD multiplied by 20.
The manufacturer purports that the ithlete? is capable of providing accurate values (Wegerif, 2009), however, to our knowledge, there are no previous studies that have investigated these claims. The current study demonstrated that the ithlete? system strongly agreed with the criterion measure. There were no significant mean differences and a near perfect correlation between the ithlete? and laboratory corrected RMSSD values. In addition, the ithlete? provided a low SEE and tight LOA. Therefore, the ithlete? provided a suitably accurate measure of corrected RMSSD when compared to the ECG measure obtained in the laboratory within the current sample of healthy Brefeldin_A adult participants.