IDENTIFYING THE INTEGRATED ELECTROMYOGRAPHIC THRESHOLD USING DIFFERENT MUSCLES DURING INCREMENTAL CYCLING EXERCISE

Background. The purpose of this study was to identify the IEMG thresho ld in the vastus lateralis (VL) and rectus femoris (RF) muscles during progressive, incremental exercise and to relate these thresholds to t he ventilatory threshold (Tvent), Methods, Ten men (age: 23.40+/-3.13 yrs, mass 76.64+/-8.13 kg, % fat: 8.81+/-2.32,(V) over dotO(2) peak: 6 6.37+/-10.61 ml kg min-l) with cycling experience completed a graded e xercise test on a cycle ergometer by cycling at 90 rpm using 45 watt i ncrements at two minute intervals. Oxygen uptake was measured continuo usly and the IEMG activity of the VL and RF was calculated during the last 5 s of each minute. The mean for the IEMG of 6 to 7 complete peda l revolutions was used as the final value. Tvent was visually identifi ed using the (V) over dotO(2)/(V) over dotO(2) and V-slope methods. Th e IEMG threshold for VL and RF was visually identified at the inflecti on point where a non-linear increase in IEMG occurred. Comparisons bet ween Tvent and IEMG thresholds were made using dependent means ''t''-t ests. Results, Results showed that an IEMG threshold was identified in all 10 subjects for the RF, but in only 5 of 10 subjects for the VL, However, when identified, the IEMG threshold for VL was similar to RF. (V) over dotO(2) at IEMG threshold for RF (3.53+/-0.36 L.min(-1)) was not significantly different from Tvent (3.36+/-0.42 L.min(-1)). Conclu sions. These results show that the IEMG threshold is more consistently detected in the RF compared to VL during incremental cycling exercise . In addition, the IEMG threshold for RF was closely related to Tvent and provides an alternative means to assess the ventilatory threshold.