###### Abstract  
This study examined whether the 5-week pre-operative progressive exercise rehabilitation program with weekly monitoring contributed to a significantly lower muscle activity imbalance in the treatment group, both before and immediately after anterior cruciate ligament reconstruction (ACLR), as well as during the next 5 weeks in comparison to the control group. Twelve professional soccer players took part in the study (from among the top three Polish levels of competition) (age: \(26\pm 5\) years, body mass: \(73\pm 7\) kg, stature: \(180\pm 6\) cm, training experience: \(15\pm 4\) years). The participants were randomly assigned to the treatment group (\(n=6\)) or to the control group (\(n=6\)). Both groups performed the same pre- and post-operative progressive exercise rehabilitation program, while the rehabilitation of the treatment group was extended by supplementary body-weight functional stabilization training. The three-way repeated-measures ANOVA revealed a statistically significant interaction for muscle \(\times\) group \(\times\) time (\(p<0.0001\); F = \(24.897\); \(\eta^{2}=0.806\)). The post-hoc analysis for the interaction effect of muscle \(\times\) group \(\times\) time indicated a significantly higher muscle activity imbalance for every measured muscle in the control group at any time point than in the treatment group (from \(p=0.036\) to \(p<0.0001\)). The muscle activity imbalance was significantly higher from the 1 st to 4 th weeks than in the last week before surgery for quadriceps (\(p<0.016\) for all) and hsmstrings (\(p<0.001\)). However, in the case of plutal muscles' activity imbalance, it was significantly higher at every time point of the post-operative phase than in the last week before surgery (\(p<0.001\)). The results of this study showed that the 5-week pre-operative rehabilitation program with weekly monitoring influenced outcomes of the post-operative phase. Nevertheless, performing both pre- and post-ACLR rehabilitation significantly reduced the muscle activity imbalance of lower limbs, but in the case of the quadriceps muscles, not to a sufficient level. e lectromyography; soccer; muscle activity; body-weight training; balance training +
Footnote †: journal: Applied Sciences  
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22 July 2022  
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risk for ACL re-injury [6]. One approach is to conduct combined pre- and post-operative progressive rehabilitation among patients treated for acute injury [7,8]. The rationale for this approach is that optimal pre-operative knee joint function will lead to a faster and safer return of knee joint function in the post-operative phase [7,9]. [PERSON] et al. [10] showed that a 5-week progressive exercise rehabilitation program, within 3 months after ACL rupture, was sufficient to significantly improve knee joint function (limb symmetry index and single-leg hop test). However, the authors did not also evaluate knee function during pre-operative rehabilitation. Another study by [PERSON] et al. [9] indicated that a large pre-operative quadriceps strength deficit results in a significantly lower limb symmetry index at 6 and 9 months after ACLR. Moreover, the study by [PERSON] et al. [11] was the only one to show that pre-operative rehabilitation involving progressive strengthening and neuromuscular training, followed by a post-operative rehabilitation program, resulted in better functional results and RTP rates 2 years after ACLR than the cohort without extended preoperative rehabilitation. Furthermore, [PERSON] et al. [12] found that 4 weeks of pre-operative rehabilitation significantly lowered the deficit in quadriceps strength and improved single-leg hop distance in comparison to patients who did not participate in a pre-operative rehabilitation. Moreover, in addition to the positive effects of preoperative rehabilitation on physical fitness, the psychological factors should also be taken into account as important for return to pre-injury sport activity after ACLR [13,14].