Purpose:
The purpose of this research was to investigate the effect of eight weeks of cross-training on the intensity of electrical activities and the functional quality of the muscles of athletes with anterior cruciate ligament injury during walking.
Methods:
This semi-experimental study utilized a pre-test/post-test design. The statistical population included the athletes from Qeshm Island and Bandar Abbas City (football and volleyball), who had at least six months since their anterior cruciate ligament reconstruction. In this research, there were 30 participants who were divided into two training groups and a control group. The average age of the training group was 24.15 ± 7.89 and the control group was 24.97 ± 7.18 years. The electrical activity of the muscles was measured by an electromyography device in two phases, 100 milliseconds before (in the swing phase) and 200 milliseconds after the contact of the foot with the ground (in the stance phase). Also, the force plate device was used to measure the functional quality of the muscles. Ground reaction force; GRF and center of pressure; COP fluctuations were measured from the time of foot contact with the ground to 200 milliseconds after contact (in the stance phase), before and after cross training. The data were analyzed using SPSS software, version 25 and Repeated Measures ANOVA.
Results:
In the swing phase (100 milliseconds before the heel strike), the electromyography data of the research showed that after a period of cross training, the electrical activity of all the selected muscles increased, but this increase was significant in the tibialis anterior(from 45.18 to 48.31 microvolts) (p=0.009), rectus femoris (from 38.54 to 40.17 microvolts) (p=0.004), and gluteus medius (from 29.18 to 33.50 microvolts) (p=0.005). Also, the results of examining the electrical activity of the muscles in the stance phase (200 milliseconds after the heel strike), showed that the intensity of the electrical activity of all muscles increased after a period of cross training, but this increase was significant,  in the anterior tibial (from 09 44.56 to 49.5 microV) (p=0.001), vastus medialis(from 48.00 to 56.58 microV) (p=0.004), rectus femoris (from 45.18 to 48.31 microV) (p=0.02), biceps femoris (from 40.54 to 48.74 μV) (p=0.007) and gluteus medius (from 34.09 to 39.17 μV) (p=0.01). The results of the data related to moror control, (including the components of the ground reaction force and the fluctuations of the center of pressure from the time of the heel strike to 200 milliseconds later) after a period of cross training, a significant reduction has been shown in the vertical components (from 16 123.75 to 113.75 percent of weight in kilograms) (p=0.001), and the posterior component of the ground reaction force (from 23.12 to 19.15 percent of weight in kilograms) (p=0.002), and also in the fluctuations of the pressure center in the lateral direction (from 1.39 to 1.18 mm/s) (p=0.004) and the anterior direction (from 1.32 to 1.52 mm/s) (p=0.001).
Conclusion:
Cross- training has been able to create changes in the injured leg through positive neuroplasticity in the motor cortex of the brain, which not only increases muscle activity, but also improves the quality and control of movement. It is suggested for sports injury and rehabilitation specialists to positively transfer the quality of movement to the injured leg It is suggested for sports injury and rehabilitation specialists to positively transfer the quality of movement to the injured leg. These exercises can be used to prevent anterior cruciate ligament injury and also in the initial time after the injury )when the person is unable to move the injured leg( or even after months of the injury.