Ability of Wearable Electromyographical Compression Shorts to Predict Lactate Threshold

Background: Proper determination of lactate threshold (LT) is an important variable in improving cardiovascular endurance and performance. Unfortunately, monitoring LT during exercise is a costly, invasive blood analysis, which requires either capillary blood samples or an indwelling venous catheter. However, electromyography (EMG) is a potential new method of monitoring exercise intensity and may provide a novel, non-invasive technique to monitor lactate during exercise. Purpose: The purpose of this investigation was to determine if EMG compression shorts accurately estimated LT during incremental cycling. Methods: Thirteen adult men (n = 8) and women (n = 5) volunteered to participate in this study. Participants completed an incremental, maximal graded exercise test on a cycle ergometer. Blood lactate, heart rate, and oxygen consumption were measured every minute, while EMG was recorded continuously throughout the test at the vastus lateralis. Surface EMG signals were acquired via compression shorts containing built-in, non-invasive surface electrodes. The lactate and EMG thresholds were determined in each participant via Dmax calculations. Results: Results demonstrated no significant difference in work rate (p = 0.08) between lactate and electromyographical thresholds. Additionally, no mean differences existed between EMG and lactate thresholds for maximal heart rate (p = 0.13, Cohen’s d = 0.43) or percent peak oxygen consumption (p = 0.64, Cohen’s d = 0.09). Consistent with previous results, EMG provided a moderate correlation with the prediction of work rate associated with the LT (r = 0.68, p = 0.01). Conclusions: The results demonstrate that no differences occurred between LT and EMG threshold for any of the metrics examined (i.e., work rate, heart rate, or oxygen consumption). This confirms that both lactate and EMG exhibit similar properties (i.e., increasing exponential values) during incremental exercise. A possible mechanism includes the rise in blood lactate concentration increasing motor unit recruitment in an attempt to maintain proper cadence and force output during incremental exercise. Thus, a coincidental, exponential increase in EMG amplitude may occur. Practical Application: Monitoring blood lactate values may be an important determinant of the ability of the athlete to maintain pre-determined exercise intensities for extended durations. Therefore, EMG, monitored via specialized compression gear, may provide a viable option in monitoring training intensity and predicting LT levels due to its ability to provide feedback in real-time