Introduction Studies analysing the pattern of activity of the muscles implied in pedalling were carried out on sedentary subjects or non elite cyclits (Eisner et al., 1999; Ericson et al., 1986). They do not reveal any interindividual difference in the use of the various muscles and are often limited to the use of a single technique of analysis: the surface electromyograpy (EMG). EMG has been used for many years for characterizing the muscular electrical activity in numerous sports. In addition, the Magnetic Resonance Imaging (MRI) permits a non-invasive functional exploration of muscles function. Thus, the analysis of the changes (before versus after exercise) of contrast (T2 type) makes it possible to determine the active muscles during an exercise. The amplitude of these changes is correlated to the exercise intensity (Fisher et al., 1990). In the present series of experiments performed on professional cyclists, we combined these two noninvasive techniques to study the pattern of activity of lower limb muscular groups during exhausting pedalling exercises. Our experimental approach allows to determine wether or not the expert cyclists use a common pattern of recruitment for these muscles during pedalling. Methods Six professional cyclists participated to this study. For each subject, the experiment proceeded over one day. Cyclists performed in the morning a progressive test on cycloergometer (Excalibur, Lode®, France). After 3 minutes of pedalling at 100 Watts, the load was increased by 26 Watts every minute until exhaustion and voluntary stop of the subject. During this exercise, we recorded EMG of eight muscles of the right lower limb (Mega®, Finland), i.e. Vastus Lateralis (VL), Rectus Femoris (RF), Vastus medialis (VM), Semitendinosus (ST), Biceps Femoris (BF), Gastrocnemius Lateral (GL), Gastrocnemius Median (GM) and Tibialis Anterior (TA). After 3 h of recovery including a meal, the cyclists performed a constant-load exercise on the same cycloergometer. After 10 minutes of pedalling at 100 Watts, the load was increased to the Maximal Tolerated Power (MTP) of the subject determine during the morning session. The subject was asked to maintain this power until exhaustion (tlimMTP). MRI recordings were carried out immediately after the exercise on the front right thigh. Results The EMG signal was computed by using the MegaWin software (Mega®, Finland) to obtain the Root Mean Square (RMS), thus revealing the average power of the myoelectric signal for each studied muscle. Our results show that RMS changes of each muscle are very different between subjects.
© Copyright 2002 Expertise in Elite sport. 2nd International Days of Sport Sciences, 12.-15. November 2002, INSEP, Paris (France). Veröffentlicht von INSEP. Alle Rechte vorbehalten.