Effects on the Patellar Tendon After Low-load Blood Flow Restriction Training.

Short-term Effects on the Patellar Tendon After Low-load Blood-flow Restriction Training Versus High-load Conventional Training. Randomized Clinical Trial.

The main objective of this research project is to study the transient adaptations that occur in the tendon immediately after the object of training with low loads and blood flow restriction and to compare these adaptations with those derived from training with high loads, in order to thus helping to elucidate the complex existing framework regarding the effects of this training methodology on the tendon.

Introduction: Nowadays, it is known that mechanical loading is essential to achieve tendon adaptations. So,if tendons are stimulated in the right way, positive changes will take part on the tendinous tissues increasing its capability to stand mechanical loading.In the last decade, low load blood flow restriction training has developed as an alternative methodto high load training, as some investigations have found a similar increase in force and hypertrophy between both training methods. Although, the evidence about tendon adaptations leading from low load blood flow restriction training is still very limited.Aim: The present study aims to study tendon temporary responses leading immediately after a low load blood flow restriction training and compare those adaptations with those leading from high load strength training.Design: A randomized case-control clinical trial will be conducted.Sample: The measurement of the sample size was done with theG*Power 3.1.5 program and was based on the time-by-group interaction of a mixed variance analysis (ANOVA). With two groups and three measurement moments. The final sample size was constituted by 84 subjectsMethods:The 84 participants will be randomly allocated in two groups: a) Low load blood flow restriction training (n=42); b) high load strength training (n=42). The low load blood flow restriction training group will perform a strength training with an intensity equivalent to 30% 1RM with an occlusion pressure of 80% on the total restriction pressure assessed individually, whilst the other group will train with a load equivalent of 80% 1RM. Patellar tendon characteristics will be studied as morphometry and densitometry parameters and microcirculation pre, post immediate intervention and 24 hourspost intervention.

The first group, which we will call the "BFR group", will be trained using low-load exercises with blood flow restriction. To the second group, which we will call "high load group", an exercise program with high loads will be applied.

Training is applied to this group using low-load exercises with restriction of blood flow. Based on the variables used by the major part of the protocols used in studies on the ERFS, the protocol that will be applied to this group will consist of the following parameters. Training: 1 series of 30 repetitions followed by 3 series of 15 repetitions of squats Rest between series: Duration of 45 seconds. Workload: 30% of 1RM. Cadence: 2 seconds for the concentric phase and 2 seconds for the eccentric phase (2:2). Cuff pressure: The inflation pressure will be individualized for each individual. A pressure equivalent to 80% of the minimum pressure necessary for the total occlusion of the femoral artery. • Cuff placement: proximal quadriceps.

A program will be applied to this group of exercise with high loads as a method of treatment in which the following will be applied parameters: Training: 4 series of 12 repetitions of squats. Rest between series: Duration 2 minutes. Workload: 70% of 1RM.

Ultrasound will be used in order to collect the data of the images of each participants. Then, we will asses and compare possible changes in thickness, measured in cm, of each tendon before, after and 24 hour after the intervention.

A delimited area of 159x20 pixels inside the tendon structure will be selected. Then the program may classified all the pixels of each area on a gray scale of 255, resulting in an histogram of each tendon before, after and 24 hour after the intervention, measured in pixels in the gray scale.

Evaluate the possible presence of micro vascularization of the patellar tendon through the visualization of the tendon structure with the doppler system of the ultrasound.

The Doppler mode of ultrasound will be used to observe and compare the presence of micro-vascularization inside the patellar tendon structure, before, immediately after and 24 hours after performing the intervention for each subject. The images where the doppler mode could detect some micro-vascularization may be assigned with ''Yes´´ and those which does not show any evidence of micro-vascularization ,may be assigned as ''no´´.

Inclusion Criteria: Physically active population (physical activity between 1 and 3 weekly sessions). With the final purpose to adjust the results to normality and refer to a general population. Subjects who have received the information sheet and have given their consent informed to participate in the study. Exclusion Criteria: People who reproduce pain or symptomatology to the execution of the exercise of the treatment. People who have had symptoms in the last 2 months in the region below patellar Present musculoskeletal injuries or inability to perform the protocol experimental. Individuals with a training frequency equal to or greater than 5 sessions per week or that present a RM equal to or greater than 110kg. Since they do not fit a population and may affect the homogeneity of the sample.

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