Blood Flow Restriction for Upper Limb Rehabilitation in People With Multiple Sclerosis. A Randomized Controlled Trial (BFRT-EM)

Among the different physical exercise modalities, Blood Flow Restriction Training (BFRT) appears. This type of approach is a training modality performed with occlusion of blood flow in the extremities, partially restricting arterial flow and venous return of blood to the muscles involved. It is usually, but not always, performed in parallel with LL-RT, with repetitions close to muscle fatigue in each set, however, it can also be performed in parallel with functional or task-focused training, such as horizontal walking, aerobic work on a stationary bike. BFRT is applied via an external pneumatic tourniquet at the proximal end of the upper or lower extremity, applying occlusion pressure that promotes ischemia and blood pooling in the capillary beds of the musculature distal to the tourniquet. A 2020 investigation by Minitti et al indicated that the physiological mechanism behind the findings in muscle adaptations include acute muscle inflammation, increased recruitment of muscle fibers, decreased myostatins, decreased atrogenesis and satellite cell proliferation. Recent research has highlighted that the processes described above can be evoked in low-load strengthening in combination with the BFRT system, but not through conventional or high-load strengthening. In turn, these benefits have been observed in both young and older adults without increasing muscle damage, inflammation or pain perception. In the field of physiotherapy, BFRT has gained increasing importance, as it has awakened interest in its application as a complement to therapeutic exercise, especially in those subjects who cannot tolerate high loads due to their clinical considerations. Its validity as a tool has been proven both for sports performance in different populations (elite or amateur athletes; young and older adults with no training experience), and in populations with pathology (older adults with fragility, musculoskeletal rehabilitation, post-surgical or post-immobilization conditions, femoropatellar syndromes, meniscus tears, ligamentous strains, rehabilitation after anterior cruciate ligament surgery, people with type 2 Diabetes Myelitus, people with neurological pathologies, including multiple sclerosis, MS). The systematic review by Reina-Ruiz et al analyzed the effects of the use of the BFRT system in combination with LL-RT and aerobic exercise in people with different pathologies (anterior cruciate ligament reconstruction, stage two chronic kidney disease, coronary artery disease, end-stage renal disease, elderly comatose patients, knee osteoarthritis and recurrent non-specific low back pain). The results obtained in terms of strength, despite the heterogeneity of the outcome measures used, present the BFRT system as an effective tool for strength improvement, being equal or superior to HL-RT. In a study conducted in 2022, Vinolo-Gil et al conducted a systematic review on the use of the BFRT system in populations with different neurological pathologies (spinal cord injury (SCI), stroke, cerebral palsy and MS). Their results showed improvements in sensorimotor function, frequency, gait length symmetry, gait speed and muscle thickness. However, no improvements in balance were found. The systematic review by Jønsson et al published in the current year 2024 reported that BFRT generated greater improvements in strength in people with inclusion body myositis compared to those who received no intervention and in subjects with incomplete spinal cord injury who performed the BFRT protocol in combination with functional electrical stimulation (FES), showing greater muscle circumference in the quadriceps than those who only received FES-based treatment, with unclear results in people with MS. Given the idiosyncrasy of the tool, the safety of its use is a recurring theme in research, so a detailed analysis of the characteristics of the intervention is necessary. Since its origin in the 1980s, different types of cuffs have been used: pneumatic bicycle inner tubes, elastic bands and electronic devices. There is no scientific consensus on the use of one model over another; however, different investigations highlight certain determining characteristics for the safety and efficacy of the tool. The 4 main variables to take into account are: a) restriction pressure; b) cuff width; c) cuff type; d) cuff material. Another major concern of researchers about the BFRT system is the pain that may result from an intervention with these characteristics, which has increased significantly in recent years in this regard. The findings in terms of pain should be grouped into 2 sections: short term, medium term and long term. Short term: Korakakis et al analyzed the effects of an exercise protocol based on knee extension with low loads in combination with the BFRT system on anterior knee pain, observing that the 30 intervention subjects reduced their pain level in the 3 tests performed. In turn, the level of analgesia generated was maintained 45 minutes later, after a conventional physiotherapy session. Another investigation by Korakakis et al compared the effects of a low-intensity exercise protocol with a low-intensity exercise protocol in combination with the BFRT system. Analgesia in the low intensity and BFRT group was superior to that of the control group. Twenty percent of the participants in the control group reported greater discomfort after the intervention and 15% after 45 minutes. In turn, Lixandrão et al compared pain levels during and post-exercise compared to conventional training, finding no greater pain in the BFRT group. Medium and long term: Giles et al compared a low-load exercise protocol in combination with the BFRT system versus conventional training in patients with patellofemoral pain. The results showed significant differences in favor of the group that applied the BFRT system; in turn, the improvements were maintained in the follow-up assessment 6 months later. Beyond pain, the potential adverse effects derived from the BFRT system have been investigated in different investigations, finding no adverse effects in people with neurological pathology according to the systematic review by Jønsson et al of 2024 or only minor adverse effects in populations without neurological pathology such as small hematomas, paresthesias, stiffness, pain or stiffness. According to Nakajima et al (50), from a population of 13,000 subjects without neurological pathology, serious adverse effects derived from an intervention through the BFRT system were extremely rare (0.008-0.055%), some of these being rhabdomyolysis or thromboembolism. With respect to serious adverse effects, it should be noted that the research by Minniti et al (22) presented similar findings in terms of the frequency of occurrence of adverse effects, however, they include an analysis of the cases that presented such serious adverse effects. One patient presented deep vein thrombosis (DVT) having been exposed to continuous occlusion for 30 - 60 minutes and presenting a history of edema and alterations of sensibility of several years of evolution. Two subjects presented rhabdomyolysis, the first had a history of DVT after ankle surgery and was exposed to an arbitrary compression of 100mmHg; the second patient showed no history or apparent risk factors, but the investigators do not know the information regarding the pressure applied and the duration of this. Finally, it is worth noting that in the first case, once he was medicated for the rhabdomyolysis and the patient continued with the experimental protocol without any other adverse effects. Although the BFRT system has attracted the attention of health professionals, research on this tool in people with neurological pathology, particularly MS, is very limited. Furthermore, to our knowledge, studies on the effect of the BFRT system on forearm-hand muscle strength and fatigability, coordination and dexterity, functionality and quality of life in people with MS are nonexistent.