In response to accumulating metabolic fatigue there is a change in muscle recruitment pattern resulting in enhanced EMG activity. Muscles increase their EMG amplitude and/or shift their EMG frequency content towards higher frequencies [1, 2]. However, recent studies have shown that the neuromuscular response to fatiguing exercise, following ACL reconstruction is altered [3]. PURPOSE: The aim of the present study was to evaluate the time course of EMG variables indicating muscle recruitment patterns in a group of ACL reconstructed and healthy soccer players. METHODS: We evaluated 14 ACL reconstructed soccer players 1-3 years post-operatively and 14 healthy control soccer players. ACLR players had anterior tibial translation difference between reconstructed and intact leg less than 2mm, Tegner activity score 8 and Lysholm score 99. Athletes performed a 10 minute run at intensity ~90% of their VO2max with expired gas analysis. Blood lactate was measured at baseline and at end-exercise. EMG data were recorded at the 3rd, 5th, 7th, and 10th minute from muscles vastus lateralis and biceps femoris bilaterally with a telemetric EMG system. The dependent variables examined were the peak EMG amplitude and the total energy of the high frequency components (>90Hz, HE) of the power spectrum. Repeated measures ANOVA`s were used to compare the time course of the EMG variables between legs. RESULTS: ACL reconstructed group run at 87.6(4.4) %VO2max and control group at 88.7(3.1) %VO2max. End-exercise blood lactate values were 7.6(1.7) mM and 7.9(1.6) mM respectively. For vastus lateralis muscle peak EMG amplitude increased for both the control and intact leg but not the reconstructed leg (F=4.26, p=0.008 and F=6.74, p=0.001 respectively). HE tended to increase for both the control and intact leg but not the reconstructed leg (F=3.97, p=0.011 and F=2.81, p=0.052 respectively). For biceps femoris muscle there was an increase in peak EMG amplitude only when the ACL reconstructed group was considered (F=4.26, p=0.011). HE increased significantly for each of the tested legs and there was no significant interaction. CONCLUSION: While for both the control and intact leg there was an enhanced EMG activity in order to compensate for the accumulating fatigue, the reconstructed leg shows an inability to alter muscle recruitment patterns. This may indicate greater fatigability for the vastus lateralis of the reconstructed leg. For biceps femoris, both groups showed signs of enhanced EMG activity but this was more pronounced only for the ACL reconstructed group. This may indicate the presence of a protective mechanism under metabolic fatigue.
© Copyright 2009 14th annual Congress of the European College of Sport Science, Oslo/Norway, June 24-27, 2009, Book of Abstracts. Julkaistu Tekijä The Norwegian School of Sport Sciences. Kaikki oikeudet pidätetään. / Kääntänyt https://www.DeepL.com/Translator