ELECTROMYOGRAPHICAL COMPRESSION SHORTS TO PREDICT LACTATE THRESHOLD ABILITY OF WEARABLE ELECTROMYOGRAPHICAL COMPRESSION SHORTS TO PREDICT LACTATE THRESHOLD Ronald L. Snarr, Ashleigh V. Hallmark, Danilo V. Tolusso, and Michael R. Esco Department of Kinesiology, The University of Alabama, Tuscaloosa, AL Abstract Methods Results 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. Recreationally trained men (n=9, age = 23.7 ± 5.6, height = 175.7 ± 4.2 cm, weight = 85.6 ± 10.1 kg) and women (n=4, age = 20.75 ± 1.5, height = 165.0 ± 8.4 cm, weight = 60.5 ± 6.4 kg) volunteered to participate in this study. Participants performed a graded exercise test on a cycle ergometer, while blood lactate, heart rate, and oxygen consumption were measured every minute until exhaustion. EMG signals were recorded continuously via compression shorts interlaced with electrodes to measure muscle activity (Figure 1). Lactate and EMG thresholds were established through Dmax calculations. Muscle Activity (mV) Lactate (mmol) Time (seconds) Figure 3. Sample plot of lactate and muscle activity for 1 participant. Conclusions Non-invasive EMG was able to accurately determine the lactate threshold when compared to invasive blood sampling. Results indicate that field metrics (i.e., heart rate and oxygen consumption) may provide useful for assigning training intensities to improve cardiovascular health and endurance. Blood lactate may play a key role in muscular recruitment during exercise and therefore may provide increases in EMG signaling in a similar exponential pattern when compared to blood lactate samples. Figure 1. Athos Compression Shorts Practical Applications Introduction & Purpose Results This study provides a novel approach to examining blood concentrations of key metabolites during exercise via a non-invasive approach. Non-invasive EMG may provide a viable option for monitoring training intensities and predicting blood lactate levels. Future research of non-invasive prediction of blood constituents may provide a key role in the monitoring of blood glucose in Type II diabetic individuals. No significant differences were observed between the lactate and EMG threshold in relation to work rate during the graded exercise test. When expressed as percentage of maximal oxygen consumption, there was no significant mean difference between lactate and EMG threshold (74.6 ± 5.8% vs. 75.3 ± 6.9%, respectively). Additionally, there were no significant mean differences between lactate and EMG thresholds when expressed as percentage of maximal heart rate (88.8 ± 33.9% vs. 90.4 ± 4.1%, respectively). Determining lactate threshold is an important metric to prescribe exercise training intensities, as well as monitor chronic adaptations to the cardiovascular and neuromuscular systems. However, currently, lactate testing can only be accomplished through costly and invasive techniques (i.e., indwelling catheters or capillary blood sampling). The purpose of this investigation was to determine if a non-invasive technique (i.e., EMG) could monitor changes in lactate levels within the bloodstream and eliminate the need for invasive blood drawls. ACKNOWLEDGMENTS This investigation was funded by MAD Apparel, Inc.