EMG Threshold Determination in Eight Lower Limb Muscles During Cycling Exercise: A Pilot Study

Abstract

The first aim of this study was to verify the occurrence of the EMG threshold (EMG_Th) in each of eight lower limb muscles (vastus lateralis [VL], vatus medialis [VM], rectus femoris [RF], semimembranosus [SM], biceps femoris [BF], gastrocnemius lateralis [GL] and medialis [GM], and tibialis anterior [TA]) during incremental cycling exercise. The second aim was to investigate the test-retest reproducibility of the EMG_Th occurrence. Six sedentary male subjects (27 ± 1 years) performed the same incremental cycling test until exhausted, (workload increments of 25 W/min starting at 100 W) twice. During the tests, the EMG Root Mean Square (RMS) response was studied in the aforementioned muscles. The EMG_Th was detected mathematically from the RMS vs. workload relationship. All the subjects showed an EMG_Th in the VL muscle, and the response was reliable in both tests (246 ± 33 W and 254 ± 33 W for the first and second test, respectively; coefficient of variation: 9.6 %, standard error of measurement: 28.9). However, few of them showed an EMG_Th in the other muscles, especially in RF, SM or GM. When present, the EMG_Th occurred at 75 - 80 % of the peak power output obtained during the tests. Our results suggest that EMG_Th determination can be used as a reliable method for studying neuromuscular adjustments in the VL of untrained individuals, but not in other lower limb muscles.

Root mean square - cycle-ergometer - neuromuscular fatigue - motor unit

References

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