MECHANOMYOGRAPHY OF THE HUMAN QUADRICEPS MUSCLE DURING INCREMENTAL CYCLE ERGOMETRY

The mechanical activity of the human quadriceps muscle during maximal incremental cycle ergometry was investigated by mechanomyography (MMG) . MMG and surface electromyography (EMG) recordings of vastus laterali s muscle activity were obtained from nine males. Cycle ergometry was p erformed at 60 rev/min and work load was incremented step wise by 20 W (3.2 Nm) every minute until volitional fatigue. The mean amplitudes o f MMG (mMMG) and EMG (mEMG) during the contraction phase were calculat ed from the last six contractions in each load. The duration, load and work rate of exercise at exhaustion were 13.3 (1.6) min, 34.1 (5.5) N m, 276.7 (34.7) W, respectively. A linear relationship between mMMG an d load was evident in each subject (r = 0.868-0.995), while mEMG seeme d to dissociate as the load became greater. In the grouped mean data, mMMG was linearly related to load whether aligned to the absolute (r = 0.995) or maximal (r = 0.995) load. Involvement of the noise componen t was further investigated by studying passive cycling by four subject s. Pedals were rotated passively for the first half of each stage !PAS ) and the subject then pushed the pedals for the second half (ACT). In the lighter load region, the mMMG of ACT was as small as that of PAS. However, the change in the mMMG of PAS was very small compared with t hat of ACT. In conclusion, this study demonstrates a linear relationsh ip between the mMMG of the quadriceps muscle and work load during maxi mal incremental cycle ergometry. The effect of movement noise was thou ght to be small and stable.