Author(s): NAKANO, H., HIROSE, K., KONDO, A., MIYAMOTO, N., KAJIWARA, W., ONODERA, K., UDA, S., TAKEDA, M., Institution: DOSHISHA UNIVERSITY, Country: JAPAN, Abstract-ID: 944

INTRODUCTION:
A golden standard for EMGT (EMG Threshold) determination has not been established. This study examined methods for determination for EMGT in incremental exercise test on a bicycle ergometer (12 discrimination methods described below), and evaluated the correlation between the 12 detected EMGTs and LT1 (Lactate Threshold), LT2 (Onset of Blood Lactate Accumulation), VT1 (Ventilatory Threshold) and VT2 (Respiratory Compensation Threshold).
METHODS:
Seventeen adult male subjects (25.6 ± 9.3 years) with exercise habits were subjected to incremental exercise test on a bicycle ergometer (LC4, Monark, Sweden). The workload at the beginning of exercise was set at 30 watts (constant 60 rpm), and the workload was increased by 30 watts every 2 minutes. Wireless electromyography (DSP EMG sensor, Sports sensing, Japan) sensors were attached to the rectus femoris and vastus lateralis muscles, and EMG were obtained during exercise. Exhaled gas exchange was measured with an exhaled gas analyzer (AE-310s, Minato, Japan). Blood lactate concentration (Lactate pro 2, Arkley, Japan) was measured before the start of exercise, every 2 minutes during exercise, and immediately after the end of exercise. An accelerometer was attached to the crank of a bicycle ergometer to calculate the pedaling angle from the angular acceleration. The obtained EMG data was analyzed based on FFT, and divided by low frequency band (10-130 Hz), high frequency band (130-420 Hz), and all bands (10-420 Hz). By considering elements of 2 pedaling angles (180° or 360°) and 3 frequency bands based on the FFT analysis (Low, High or All), 6 EMGs (360°-EMG (Low), 360°-EMG (High), 360°-EMG (All), 180°-EMG (Low), 180°-EMG (High), 180°-EMG (All)) were obtained from raw EMG data. The EMGTs were determined by visual inspection, using the point at which the magnitude of the EMGTs began to rise sharply, first (EMGT1) and second (EMGT2) respectively. Total 12 EMGTs (6 EMGT1 and 6 EMGT2) were detected and evaluated the correlation between LT1, VT1, LT2, and VT2.
RESULTS:
EMGT was detected in all 12 EMGT detection methods in both the rectus femoris and vastus lateralis muscles from all subjects. The validity of the analyzed segment for pedaling (360° or 180° is preferable) was similar for the rectus femoris muscle (r = 0.83-0.92, p < 0.05) and for the vastus lateralis muscle (r = 0.80-0.97, p < 0.05). The correlation coefficient was slightly higher with 180° analyzed segment. The combinations of highest correlation among pedaling angles and frequency bands were 180°-EMGT1 (Low) in the vastus lateralis (r = 0.84, p < 0.05) for LT1, 360°-EMGT2 (High) of the vastus lateralis (r = 0.97, p < 0.05) for LT2, 180°-EMGT1 (Low) in the vastus lateralis (r = 0.82, p < 0.05) for VT1, and 180°-EMGT2 (Low) in the vastus lateralis (r = 0.86, p < 0.05) for VT2.
CONCLUSION:
It was desirable to use the vastus lateralis muscle as the target muscle for detecting EMGT. EMGT considering both pedaling angle and frequency band might be highly correlated with LT and VT.