Effects of Neuromuscular Electrical Stimulation Waveforms and Occlusion Pressures on Elicited Force and Microvascular Oxygenation

CONTEXT: Interest in the effects of concurrently using neuromuscular electrical stimulation (NMES) and blood flow restriction (BFR) to improve muscle strength has risen, but limited studies and inconsistent findings have led to more questions. The 2 current projects aimed to systematically investigate how NMES waveform shape and BFR occlusion pressure acutely influence electrically elicited force (EEF) and tissue oxygen saturation (StO2) of the knee extensors. DESIGN: A single-session repeated-measures design was followed. METHODS: EEF and StO2 were measured in 2 different groups of 15 participants during 3 sets of NMES contractions. Ten NMES contractions per set were performed with 5 minutes of passive interset recovery. In the first project, different NMES waveforms (RUS, Russian burst-modulated alternating current; VMS, biphasic pulsed current; and VMS-Burst, burst-modulated biphasic pulsed current) were administered for each set, while BFR was applied at 60% limb occlusion pressure (LOP). During the second projet, VMS was administered, while a different BFR occlusion pressure (0% LOP, 40% LOP, and 80% LOP) was used during each set. Two-way repeated-measures analysis of variance examined if repetition and/or NMES waveform (first project) or BFR occlusion pressure (second project) significantly affected (P < .05) EEF or StO2. RESULTS: VMS (12% [7%] MVIF) and VMS-Burst (13% [10%] MVIF) led to higher EFF compared with RUS (6% [5%] MVIF) with 60% LOP; 80% LOP (20% [14%] MVIF) led to lower EEF compared with 0% LOP (29% [17%] MVIF) with VMS. No significant differences in StO2 were observed between NMES waveforms or BFR occlusion pressures. CONCLUSIONS: If a clinician wanted to concurrently use NMES and BFR, the acute findings of the current projects would suggest the use of VMS or VMS-Burst with lower BFR occlusion pressure (40% LOP). However, further investigation into how these parameters would influence muscle strength subsequent to a training/rehabilitation intervention should be performed.