The acute effects of different blood flow restriction settings on blood lactate, electromyography and leg strength during bilateral knee extensions
Abstract
Description
The current protocols being used for Blood Flow Restriction (BFR) exercise did not examine the
effects of different Initial Restrictive Pressures (pressure applied to limb by cuff prior to
inflation, IRP) during design. There are several research articles highlighting the importance of
IRP and how it can create variability in results. Therefore it is necessary to evaluate the current
BFR protocol against different IRP in order to determine reliability.
PURPOSE: The purpose of this study was to examine the acute effects of different blood flow
restriction setting on 1) the level of blood lactate production, 2) neuromuscular activation (the
changes in motor unit activation and median frequency), and 3) fatigue response during bilateral
knee extension exercise.
METHODS: Thirty-three male (age= 26.63 (5.8), n=17) and female (age= 22.76 (3.3), n=16)
participants performed four sets of bilateral knee extensions on four separate occasions separated
by at least 48 hours. Each session was randomized into the following conditions:
IRP50@FRP+20, IRP65@FRP-20, IRP50 (Control), and IRP65. During each condition, blood
pressure (BP), heart rate (HR), rate of perceived exertion (RPE), discomfort/pain (DF), and
blood lactate were recorded throughout the study. Maximal voluntary contraction (MVC) was
recorded pre and post exercise. Electromyography was recorded at the vastus lateralis and rectus
femoris with a focus on motor unit activation (RMS) and muscle firing rate (MDF).
RESULTS: No significant difference was found between conditions for BP, blood lactate or
RPE. HR displayed a condition*gender interaction (p=0.022) and a trend for a condition*time
interaction (p<0.06). IRP65@FRP-20 displayed a trend for increased levels of DF (p=0.062); it
also produced significantly higher decreases in pre to post MVC in both males and females
(p<0.023), showing a strong trend for a greater effect in males (p=0.055). IRP65@FRP-20
further displayed greater levels of overall motor recruitment in the vastus lateralis (p=0.024) as
well as greater levels of motor recruitment throughout sets 2-4 in the vastus lateralis (p<0.01)
and rectus femoris (p<0.01).
CONCLUSION:IRP65@FRP-20 created greater variations amongst the variables compared to
the Control, despite having a lower final restrictive pressure. This suggests that the current
protocol may not be the most reliable method of BFR. Further research is needed to develop a
protocol that takes IRP into account.
PDF; 73 pgs.
PDF; 73 pgs.