Edward Pfluger1, Ryan Z. Amick1

1Wichita State University, Wichita, KS

INTRODUCTION: There has recently been an influx in wearable technology. While some devices fail to perform their function, many produce valid, reliable physiological data such as heart rate, joint angle, and blood pressure. These devices are beneficial to the public and to researchers who may not have access to traditional laboratory equipment. A new wearable lactate threshold device (WLT) claims to predict lactate threshold (LT) non-invasively based on peripheral capillary oxygen saturation (SpO2). It does so with near-infrared spectroscopy, which detects the presence of oxygen by the level of light penetration into the tissue. There is limited research validating this WLT’s ability to accurately predict LT. PURPOSE: To evaluate the ability of a new WLT to accurately predict LT non-invasively. METHODS: A sample of 8 participants (4 male, 4 female, 24.1±1.6 years) with no known health concerns volunteered for the study. Participants were fitted with the WLT on the right shank at the widest circumference of the calf muscle, and was synced via Bluetooth to an iPhone, following all manufacturer instructions. They were fitted with a spirometer for a VO2max test using the Bruce protocol to elicit fatigue and lactate production in the working muscles. The test consists of six 3-minute stages with a finger prick blood sample collected during the final 10-seconds of each stage. The sample was analyzed with the Lactate Pro, and SpO2 was collected from the WLT app, simultaneously. RESULTS: A repeated-measures ANOVA was conducted to determine if any differences exist between the WLT and direct blood lactate analysis. Mauchly’s Test of Sphericity indicated that the assumption of sphericity had been violated, x2(0.613), p=0.019, and therefore a Greenhouse-Geisser correction was used, where a significant difference was observed, F (1.063, 5) = 9.489, p=0.019. However, pairwise comparisons with Bonferroni adjustment indicated that, within each stage of the Bruce test, there were no significant differences between direct blood lactate analysis and WLT measures. CONCLUSION: Results indicate that non-invasive SpO2 reported by the WLT may accurately predict LT compared to direct blood lactate analysis. However, this study is limited by a small sample size, and further testing to evaluate the WLT validity is currently underway.

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