Blood lactate and electromyograpy during aerobic exercise

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The assessment of lactate threshold (LT) is an important measurement to prescribe training intensities and monitor chronic adaptations in athletes. A non-invasive method, electromyography (EMG), has been suggested as an alternative approach to LT testing. Three experiments determined the ability of EMG incorporated into compression shorts to estimate LT, effect of exercise on LT and EMG threshold (EMGT), and determined the most appropriate filtering method of the EMG signal to estimate LT. In the first investigation, participants performed an incremental exercise test while blood lactate and EMG were measured. EMG displayed no differences from blood lactate in the ability to predict LT (p = 0.08). EMGT and LT showed a moderate correlation (r = 0.68, p = 0.01) between the determination of work rates. The EMGT occurred at the same stage of the incremental test as LT in 11 out of the 13 participants (85%). No differences were seen between percentage of maximal oxygen consumption or percentage of maximal heart rate between LT and EMGT. In the second study, the effect of exercise on LT and EMGT measurement was evaluated. Participants completed two maximal exercise tests separated by 30-minutes of exercise. Individual agreement demonstrated that pre- and post-exercise LT occurred at the same work rate in 5 of 10 participants; while pre- and post- EMGT occurred at the same work rate in 6 of 10 participants. Results indicated no significant difference between the work rates of the pre-exercise LT and EMGT (0.43), although post-trial LT was significantly lower than post-trial EMGT (p = 0.007). No difference in test stage were seen between the pre- and post-exercise EMGT; however, post-trial LT occurred at a lower work rate as compared to pre-trial LT (p = 0.03). In the final study, four popular methods of EMG signal transformation were examined in order to determine their effectiveness in estimating LT. The methods used were root mean square (10- and 60-second epochs), 60- second Smoothing, and 60-secons peak-amplitude averaging. Results indicated no differences in the ability of any signal processing variations to predict LT or in relation to %VO2peak at each threshold level. In conclusion, EMG has been demonstrated to be a viable tool to estimate LT and may provide a reliable low-cost, non-invasive method of prescribing training intensities based upon EMGT testing.

Electronic Thesis or Dissertation
Kinesiology, Health sciences, Physiology