Impact of Complete Intermittent Blood Flow Restriction in Upper Limbs Strength and Neural Function.

Purpose: We aimed to investigate the chronic effects of low-load strength training (LT) with complete intermittent blood flow restriction (IBFR) on neural adaptations and strength in biceps brachii. Methods: Nineteen volunteers were randomly assigned into two different 9-week training protocols consisting of three assessment weeks and six training weeks: (a) LT with complete IBFR (LT-IBFR; n = 10) and (b) LT without complete IBFR (LT; n = 9). Strength was evaluated by predicted 1 repetition maximum (1RM) at weeks 1, 5, and 9 and neural function by root mean square (RMS) and median frequency (MDF) at sessions 1, 7, and 12 during the first three and last three repetitions. Both groups performed three sets of Scott curl with 20% of predicted 1RM interspersed with 90s rest twice a week. Results: No changes were found in predicted 1RM throughout the training protocols nor between groups. LT-IBFR group showed lower RMS in the first set than LT for the first three repetitions and higher RMS in all sets for the last three repetitions with decreases in this value across the sets with no longitudinal changes for both groups. MDF in the first three repetitions did not differentiate between groups, however, in the last three repetitions, MDF were lower for LTIBFR group in all sets and it increased across the sets for this condition with no chronical changes for both groups in both repetitions zones. These results suggest that LT-IBFR may be ineffective for increasing Q5 strength and it did not promote chronic neural adaptations.

Low load strength training, associated with or without blood flow restriction increased NO production and decreased production of reactive oxygen species in rats aorta.

Studies have shown that strength training (ST) with blood flow restriction (BFR) in which low load is used (20-50% of 1 maximum voluntary contraction - MVC) can produce positive adaptations similar to ST with loads equal to or greater than 70% 1 MVC. Furthermore, recent studies have investigated the effects of STBFR on muscle adaptations, but few studies investigated the effects of STBFR on vascular function. This study aimed to evaluate the effects of the STBFR program on the vascular reactivity of the abdominal aorta of Wistar rats with femoral arteriovenous blood flow restriction. Male rats were divided into four groups: sedentary sham (S/S), sedentary with blood flow restriction (S/BFR), trained sham (T/S), and trained with blood flow restriction (T/BFR). The animals in the S/BFR and T/BFR groups underwent surgery to BFR in the femoral artery and vein. After one week, the trained groups started the ST which consisted of climbing ladder, six sets of 10 repetitions with 50% of 1 MVC assessed by maximum loaded weight (MLW) carried out for four weeks. Concentration-response curves to Acetylcholine (ACh: 10 nM - 100 µM) and Phenylephrine (PHE: 1 nM - 30 µM) were performed in aortic rings with intact endothelium. The production of nitric oxide (NO) and reactive oxygen species (ROS) in situ and the vascular remodeling marker (MMP-2) were also measured. The ST increased the strength of the T/S and T/BFR groups in MLW tests. The S/BFR group showed a 22% reduction in relaxation to acetylcholine, but exercise prevented this reduction in the T/BFR group. In animals without BFR, ST did not alter the response to acetylcholine. An increase in NO production was seen in T/S and T/BFR showed a reduction in ROS production (62% and 40%, respectively). In conclusion low load ST with BFR promotes similar vascular function responses to ST without BFR. Low load ST with and without BFR is interventions that can improve performance with similar magnitudes. Both training methods could have some benefits for vascular health due to NO production in the aorta increased in the T/S group and decreased production of reactive oxygen species in the T/BFR group.