Impact of index finger force on motor unit recruitment pattern in flexor digitorum superficialis / 医用生物力学

Objective To detect the recruitment pattern of motor unit in human flexor digitorum superficialis (FDS) at different force levels produced by the index finger. Methods Eight subjects were recruited to produce a certain force level with the index finger to match the ordered force level (20%, 40%, 60% maximum voluntary contraction). During the force tracking task, the multi-channel surface electromyography (sEMG) signals were recorded on FDS using 8×1 (row×column) electrode-array. The motor unit action potential (MUAP) information was extracted by Fast Independent Component Analysis (FastICA), and then the correlation between MUAP pattern and force level was analyzed. Results Four different types of MUAP were extracted successfully by FastICA from original sEMG signals and the total number of MUAP showed an increasing trend with the force level increasing. At different force levels, the proportion of different types of MUAP was different, showing different trends with change of the force level. ConclusionsAt different levels of the finger force, the recruitment pattern of motor unit in FDS will be changed so as to produce the force accordingly.

The Proximal and Distal Interphalangeal Flexion Dysfunction, Opposition Palm Ratio and Thumb Index Ratio in the Korean Adults

OBJECTIVE: The purpose of this study was to evaluate the incidence of inability to flex proximal interphalangeal (PIP) and distal interphalangeal (DIP) joint in normal Koreans. The opposition palm ratio and thumb index ratio was also of interest. METHOD: Randomly selected eighty nine normal Korean adults of 48 men and 41 women, with ages 20 to 79 years. The finger flexion was measured using the standard flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) screening tests. Thumb index ratio and opposition palm ratio was also assessed additionally. RESULTS: In the sample population, 2 subjects (2.2%) were unable to bilaterally flex their fifth PIP joints independently. Four subjects (4.4%) were unable to flex one or both of their fourth or fifth DIP joints. These results show far less incidence of FDS dysfunction comparing with 52% of FDS dysfunction rate in Americans. The opposition palm ratio in men were 63.6% and in women 69.9%, indicating lower ratio in men. The thumb index ratio was not different statistically between the men and women. CONCLUSION: These data suggest that the different incidences of FDS and FDP dysfunction should be considered in interpretation. The opposition palm ratio and thumb index ratio might be useful in the hand rehabilitation.