Flanagan, SD, Comstock, BA, DuPont, WH, Sterczala, AR, Looney, DP, Dombrowski, DH, McDermott, DM, Bryce, A, Maladouangdock, J, Dunn-Lewis, C, Luk, HY, Szivak, TK, Hooper, DR, and Kraemer, WJ. Concurrent validity of the Armour39 heart rate monitor strap. J Strength Cond Res 28(3): 870–873, 2014—New technology offers potential advantages in physically demanding environments where convenience and comfort are important and accurate and reliable data collection is challenging. Nevertheless, it is important to validate the accuracy and reliability of such biological monitoring systems (BMS) before they are adopted. The purpose of this investigation was to assess the concurrent validity of a new heart rate monitor across a range of exercise intensities and with a large and diverse group of male subjects in a large cohort with diverse physical fitness characteristics. Seventy-five men (age, 23 ± 4 years; height, 181 ± 8 cm; body mass, 83 ± 12 kg; estimated V̇o2peak, 3.16 ± 0.63 [L·min−1]) volunteered and completed a graded cycle ergometer exercise protocol while heart rate was continuously monitored before, during, and after exercise with the new device (Armour39) and the gold standard (electrocardiogram). The 2-minute stages included sitting, standing, and cycling with 35 W increments until volitional fatigue. The coefficient of determination between mean heart rate values at each stage was R2 = 0.99, whereas Pearson correlations (r) at each stage were ≥0.99. Heart rates during exercise were typically within 1 beat of each other. The Armour39 BMS, therefore, is an acceptable means for the valid and reliable determination of heart rate under various bodily positions and levels of exertion, including maximal exercise intensity.