BACKGROUND: When comparing neuromuscular activity between different individuals or different conditions by use of surface electromyography (sEMG) it is necessary to apply standardized assessment protocol. Most frequently used method is the maximum voluntary isometric contraction (MVIC). However, the influence of body posture on sEMG activity during MVIC testing remains largely unknown.
AIM: To evaluate the MVIC method for sEMG normalization in supine versus standing positions for selected muscles of the lower extremity and trunk.
METHODS: Twelve healthy individuals participated; five females and seven males (age 22-51 yrs). sEMG signals were recorded bilaterally from mm tibialis anterior, gluteus medius, adductor longus, rectus abdominus, external oblique and internal oblique/transversus abdominus according to standardized test protocol. Two different body positions were used: supine and standing position.
RESULTS: MVIC peak sEMG signal amplitudes did not differ systematically between supine and standing test positions. Pronounced inter-subject variability in MVIC reference sEMG activity were observed between participants, during both supine and standing test positions.
CONCLUSION: Present data demonstrate that MVIC EMG normalization is a biomechanically stable procedure that can be performed in a reproducible manner for the major leg and trunk muscles when comparing supine vs. standing test positions.