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1997 Publications

Spectral Analysis of Quadriceps Function Following ACL Reconstructionby MP McHugh, TF Tyler, SJ Nicholas, GW Gleim (FACSM)NISMAT, Lenox Hill Hospital, New York, New York. - last modified 2013-02-09 00:00
Med. Sci. Sports Exerc., Vol. 29(5):s, 1997.


The ability to voluntarily activate the quadriceps in long sitting (quad set) is noticeably impaired immediately following ACL reconstruction and is evidenced by a decrease in the amplitude of the surface EMG signal. Concomittant changes in the frequency content of the EMG signal have not been examined. The purpose of this study was to examine amplitude (IEMG) and frequency changes in the surface EMG signals from the vastus lateralis (VL) and medialis muscles (VM) during a quad set. EMG signals were recorded during 4 maximal contractions lasting 4 s in 10 patients (4 men 6 women). Measurements were made 2 weeks prior to ACL reconstruction, 2 weeks post-op, and 6 months post-op. Additionally knee extension strength (KE) was measured isokinetically pre-op and 6 months post-op. Results are percent of uninvolved knee+sem (*significant deficit p<0.05).

KE strength was decreased pre-op (75 +/- 6%*) and 6 months post-op (63 +/- 6%*). Both the amplitude and frequency content of the EMG signals from the VM and VL during a quad set were affected by ACL injury (pre-op) and reconstruction (post-op). As expected quadriceps inhibition was evident at two weeks. The EMG amplitude during a quad set had returned to normal by 6 months despite significant weakness. However, the median frequency of the VM remained depressed.