Blood Flow Restriction and Cross-education Effect on Muscle Strength Recovery After ACL Reconstruction

It has been suggested that standard strengthening exercises applied during rehabilitation after ACL reconstruction may be insufficient in terms of recovery of quadriceps strength and muscle volume. This insufficiency increases the risk of injury if the person returns to sports. At the same time, weight-bearing exercises within a safe knee range of motion are more recommended for these patients, as resistance quadriceps strengthening in non-weight-bearing positions (knee extension) for early strength gain is thought to be detrimental to graft healing. However, such exercises may not be as adequate as weightless exercises to strengthen the quadriceps. At this point, cross-training can be a potential way to achieve strength gain. Cross-education is an increase in strength in the untrained limb after unilateral strengthening of the homologous contralateral limb. Although the exact mechanisms of cross-education have not yet been defined, the strength gains produced in the non-exercising extremity are thought to occur as a result of improvements in cortical and spinal neural activity. Another popular practice for muscle hypertrophy recently is low-intensity exercise with blood flow restriction, also known as KAATSU training or occlusion training. Blood flow restriction exercise training is an exercise protocol based on external pressure restriction of blood flow by means of an elastic bandage or cuff from the proximal of the target muscle. It is recommended that external pressure be applied sufficiently to restrict venous return but maintain arterial flow. The relative anaerobic environment created during these periods of venous occlusion causes various localized cellular and hormonal changes that stimulate muscle hypertrophy. It is suggested that the effects of exercise increase in this hypoxic environment, thus increasing muscle mass and strength. It is thought that with the combined application of these approaches, their effects on muscle strength development will increase, and accordingly, the functional results of individuals will be positively affected.

The sample size was calculated as 1Nm/kg difference in muscle strength with 80% power and 0.05 type I error. A total of 20 individuals were determined, with 10 volunteers in each group.

Demographic information (age, gender, body mass index, dominant side, affected side, history, time from injury to surgery, date of surgery) of all cases will be recorded. Primary and secondary outcome meausers will be evaluated before the training session.

Eccentric cross-education with the isokinetic system will be applied to the unaffected extremities of the patients in the intervention and control groups. Each isokinetic training session will include 3 sets of 12 repetitions at 10°- 90° flexion angles, 60°/s angular velocity. There will be 2 minutes rest between sets. Cross-education will be applied in the same way for both groups. In the intervention group, blood flow restriction (occlusion) will be applied at a safe pressure range specific to each patient by wearing a pneumatic tourniquet from the proximal thigh during cross-training for 8 weeks.

The data will be analyzed using per-protocol anaylses. IBM SPSS 21.0 will be conducted for statistical analysis. The normality of the distribution will be analyzed with the Shapiro-Wilk test. The independent samples T test will be used for the normal distribution variables in the comparisons between the groups, and the Mann-Whitney U test will be used for the within-group comparisons for the variables that do not fit the normal distribution. For in-group comparisons, the paired samples T test will be used for the variables conforming to the normal distribution, and the Wilcoxon test will be used for the variables not conforming to the normal distribution. Significance level was set at p < 0.05.