Background - Surface electromyographic data (SEMG) was acquired from leg muscles Soleus, Tibialis Anterior and Lateral head of Gastrocnemius to study effect of footwear on heel rise action while knee kept in flexion. Surface electromyography signals were synchronously acquired from different subjects on separate occasions for this purpose. Reliability of surface electromyography data was required to be established prior to analyze the intended footwear influences on leg muscle in heel rise action. Therefore, so acquired SEMG signal data was tested for intra-session & intra-rater reliability analysis of surface electromyographic outcome measures. Aim – The study was undertaken to analyze intra-session, intra-tester reliability of frequency as well as time domain outcome measures extracted from SEMG signals. Design & Setting – Experimental approach was adopted to acquire simultaneous SEMG signals from leg muscles from 40 participants. Each participants performed three repetitions of heel rise action with knee maintained in flexion, both in barefoot (experimental) and shod (control - flip flop) conditions. The order of the experimental and control condition was assigned randomly. Common SEMG features Mean Frequency MNF, Root Mean Square RMS & Time to Peak TTP were extracted from the SEMG signal data so acquired. Statistical Analysis – reliability analysis was performed for RMS, MNF & TTP features from individual dataset of all three trials in the two foot conditions (barefoot & shod). Intra-class Correlation (ICC) was computed for corresponding dataset to test the reliability of the SEMG data drawn features. Results – Good intra-rater reliability (ICC > 8.0) was found for Mean Frequency and Root Mean Square for all three leg muscles in both barefoot and shod conditions; however very poor reliability was demonstrated by Time To Peak (TTP) feature for all muscles in both conditions. In general reliability was better in barefoot condition than shod; ICC was observed higher in footwear condition only in case of Tibialis Anterior for RMS feature. Discussion – The result establish the fact that intra-session, intra-rater reliability of SEMG based outcome measures is affected (reduced) by footwear as compared to the barefoot. Grossly ICC analysis affirm good reliability for Mean Frequency and Root Mean Square features while it is very poor (unreliable) for the Time to Peak (TTP) feature. These results were found consistent with respect to each muscle and shod condition. Conclusion – Flip Flop (footwear) alters (reduces) intra-session intra-rater reliability of SEMG outcome measures. Frequency domain (MNF) outcome measure when extracted during concentric action of muscle give most reliable dataset as compared to the other SEMG features. Further three repetitions are reasonably sufficient for averaging purpose of SEMG data without compromising reliability of sEMG variables.

SEMG, RELIABILITY, FOOTWEAR, SOLEUS, HEEL-RISE