Abstract
The goal of this trial was to determine whether low-load blood flow-restricted (BFR) exercise of appendicular muscles induces a cross-transfer of effect to the trunk extensor (TE) muscles, such that low-load TE exercise would enhance TE size and function to a greater extent than standard low-load exercise in people with recurrent low back pain (LBP). We also investigated the direct effects of BFR exercise in the appendicular muscles. Thirty-two adults with recurrent, nonspecific LBP were randomized into two groups: Appendicular BFR exercise (BFR exercise) or control exercise (CON exercise). All participants trained (two times per week) for 10 wk, with a 12-wk follow-up. Participants performed three sets of leg extension (LE), plantar flexion (PF), and elbow flexion (EF) exercises followed by low-load TE exercise without BFR. Outcome measures included magnetic resonance imaging-derived muscle size (quadriceps and TE), strength (LE, PF, EF, and TE), and endurance (LE and TE). There was no evidence for a cross-transfer of effect to the TE. There was also no statistically significant enhancement of limb skeletal muscle size or function of BFR relative to CON exercise at any time point; though, moderate effect sizes for BFR exercise were observed for enhanced muscle size and strength in the leg extensors. Low-load BFR exercise of the appendicular muscles did not result in a cross-transfer of effect to the TE musculature. There was also no significant benefit of low-load BFR exercise on the appendicular muscle size and function, suggesting no benefit from low-load BFR exercise in adults with recurrent, nonspecific LBP.
Highlights
More than 25 yr ago Sundberg and colleagues [1] suggested that performing exercise under conditions of modest blood flow restriction (BFR)
A strong stimulation of the metaboreflex by these conditions could account for findings from numerous studies reporting that single bouts of BFR exercise increase serum growth hormone and IGF-1 levels [12,13,14,15,16] to levels comparable to, or greater than, those observed during resistance training at much higher intensities [17]
We were able to investigate the direct effects of BFR exercise in the appendicular muscles, which is impactful when one considers that many studies on BFR exercise have been criticized for being lower-quality studies [3]
Summary
More than 25 yr ago Sundberg and colleagues [1] suggested that performing exercise under conditions of modest blood flow restriction (BFR) (referred to in their seminal article as “ischemic training”). Madarame and colleagues reported an increase in muscle size (12%) and strength (9.8%) of the elbow flexors after 10 wk of low-load resistance exercise coupled with BFR of the legs, but not arms [8] This purported phenomenon, commonly referred to as a “cross-transfer of effect,” has been reported in several studies [8,9,10,11]. A strong stimulation of the metaboreflex by these conditions could account for findings from numerous studies reporting that single bouts of BFR exercise increase serum growth hormone and IGF-1 levels [12,13,14,15,16] to levels comparable to, or greater than, those observed during resistance training at much higher intensities [17] This underlying scientific premise has been called into question by data suggesting no systemic hormonal influence on hypertrophy or strength gains [18,19]. We were able to investigate the direct effects of BFR exercise in the appendicular muscles, which is impactful when one considers that many studies on BFR exercise have been criticized for being lower-quality studies [3]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
