Neuromuscular effects of dorsiflexor training with and without blood flow restriction

Abstract

Blood flow restriction training (BFRT) has been proposed for elderly and clinical populations with weakness. Before being used in these populations it is important to understand the neurological effects of, and subject perceptions to, BFRT. Seventeen healthy subjects were recruited and performed 2 experimental sessions, BFRT and training without blood flow restriction (TR-only), on separate days. Four sets of concentric/eccentric dorsiflexion contractions against theraband resistance were performed. Surface electromyography of the tibialis anterior was recorded during exercise and for the electrophysiological measures. At baseline, immediately-post, 10-min-post and 20-min-post exercise, motor evoked potentials (MEPs) from single pulse transcranial magnetic stimulation (TMS), paired-pulse TMS with interstimulus intervals of 2-ms (SICI) and 15-ms (ICF), and the M-max amplitude were recorded in the resting TA. Following training, subjects provided a numerical rating of the levels of pain, discomfort, fatigue, focus and difficulty during training. Muscle activation was higher in the last 20 contractions during BFRT compared to TR. There was no difference (time × condition interaction) between BFRT and TR for single-pulse MEP, SICI, ICF or M-max amplitude. There was a significant main effect of timepoint for single-pulse MEP and M-max amplitudes with both significantly reduced for 20-min-post exercise. No reductions were observed for SICI and ICF amplitudes. Taken together, BFRT and TR-only were only different during exercise and both regimes induced similar significant reductions in M-Max and MEP-amplitude post-training. Due to the lack of changes in SICI and ICF, it is unlikely that changes occurred in cortical sites related to these pathways. The increased surface electromyography activity in the last 20 contractions, indicate that the training regimes are different and that BFRT possibly induces more fatigue than TR. As such, BFRT could be used as an adjunct to conventional training. However, as subjects perceived BFRT as more painful, difficult and uncomfortable than TR-only, people should be selected carefully to undertake BFRT.

A Systematic Review and Meta-Analysis on Neural Adaptations Following Blood Flow Restriction Training: What We Know and What We Don't Know

“…These differences were still apparent after the end of the 4-min period. Since then, similar observations were reported by several research groups (Kinugasa et al, 2006 ; Lauver et al, 2017 , 2019 ; Husmann et al, 2018 ; Ilett et al, 2019 ; Kjeldsen et al, 2019 ). Even though the results of the latter studies indicated profound increases in muscle excitation with LL-BFR, there was also a small number of studies which could not find any between-group differences (Thiebaud et al, 2014 ; Oranchuk et al, 2019 ).…”

“…The results regarding the differences in muscle excitation between LL and LL-BFR training demonstrated a significant increase in surface muscle EMG in favor of LL-BFR. The longitudinal changes which are reviewed in this work, resemble findings from cross-sectional studies looking at the acute effects of training with partial vascular occlusion (Kinugasa et al, 2006;Lauver et al, 2017Lauver et al, , 2019Husmann et al, 2018;Ilett et al, 2019;Kjeldsen et al, 2019). In a frequently cited study by Moritani et al (1992) participants were instructed to complete a 4-min bout of repeated intermittent isometric hand grip contractions (20% MVC) with one group having the blood flow restricted during the second minute (cuff pressure 200 mmHg).…”

“…While it is not clear what was causing the decrease in resting twitch torque, the increase in PAP could be one potential mechanism explaining the increased adaptations in muscle strength after LL-BFR training compared to LL training without BFR even though no long-term study has investigated this. In an acute study, Kjeldsen et al ( 2019 ) looked at central neural changes following a single bout of LL-BFR and LL exercise and found neither a group difference in short-interval intracortical inhibition (SICI), intracortical facilitation (ICF) nor in single pulse motor evoked potentials (MEPs) measured in the tibialis anterior muscle (TA). One reason explaining why the authors did not observe any changes in these parameters could be that they applied these measures during rest and not during activity even though it is known that especially inhibition is known to be task-specifically modulated (Soto et al, 2006 ; Opie and Semmler, 2016 ; Taube et al, 2019 ).…”

“…For an adequate interpretation of the present findings, there are some critical aspects that need to be considered. Firstly, acute and cross-sectional studies examining the effects of LL-BFR training on neuromuscular parameters are currently becoming available in large quantities (Kinugasa et al, 2006 ; Lauver et al, 2017 , 2019 ; Husmann et al, 2018 ; Ilett et al, 2019 ; Kjeldsen et al, 2019 ). However, trials investigating long-term peripheral and central neural adaptations are scarce.…”

The Differences of Pulse on The Day of Training Based on Hours Sleep

“…There is a new training model, namely by blocking the flow of blood, there will be a bigger contraction if this method is used (Kjeldsen, Naess-Schmidt, Hansen, Nielsen, & Stubbs, 2019), this exercise is done by tying the muscles, it is uncomfortable, is more painful and has a higher level of fatigue (Kjeldsen et al, 2019). Based on research exercise improves arterial blood vessel function even without weight loss (Maeda et al, 2015).…”