Article

Exercise intensity and muscle hypertrophy in blood flow-restricted limbs and non-restricted muscles: a brief review

Department of Health and Exercise Science, University of Oklahoma, Norman, OK 73019, USA.
Clinical Physiology and Functional Imaging (Impact Factor: 1.33). 07/2012; 32(4):247-52. DOI: 10.1111/j.1475-097X.2012.01126.x
Source: PubMed

ABSTRACT Although evidence for high-intensity resistance training-induced muscle hypertrophy has accumulated over the last several decades, the basic concept of the training can be traced back to ancient Greece: Milo of Croton lifted a bull-calf daily until it was fully grown, which would be known today as progressive overload. Now, in the 21st century, different types of training are being tested and studied, such as low-intensity exercise combined with arterial as well as venous blood flow restriction (BFR) to/from the working muscles. Because BFR training requires the use of a cuff that is placed at the proximal ends of the arms and/or legs, the BFR is only applicable to limb muscles. Consequently, most previous BFR training studies have focused on the physiological adaptations of BFR limb muscles. Muscle adaptations in non-BFR muscles of the hip and trunk are lesser known. Recent studies that have reported both limb and trunk muscle adaptations following BFR exercise training suggest that low-intensity (20-30% of 1RM) resistance training combined with BFR elicits muscle hypertrophy in both BFR limb and non-BFR muscles. However, the combination of leg muscle BFR with walk training elicits muscle hypertrophy only in the BFR leg muscles. In contrast to resistance exercise with BFR, the exercise intensity may be too low during BFR walk training to cause muscle hypertrophy in the non-BFR gluteus maximus and other trunk muscles. Other mechanisms including hypoxia, local and systemic growth factors and muscle cell swelling may also potentially affect the hypertrophic response of non-BFR muscles to BFR resistance exercise.

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    • "Consequently , due to the lower mechanical stress on the musculo-skeletal system LLRE with BFR may provide a training method for potential use by some clinical and elderly populations where HLRE is not possible or not recommended (Takarada et al., 2000; Karabulut et al., 2010, 2011; Vieira et al., 2013). With this in mind, and despite the effects of BFR exercise training on increasing muscle strength, size, and endurance being well founded (Abe et al., 2012; Pope et al., 2013), it is important to identify the hemodynamic effects of BFR exercise to further establish and support its safe application prior to making any recommendations for prescription in populations where HLRE may be contraindicated. Of importance is the method by which BFR may be applied. "
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    ABSTRACT: Light-load exercise training with blood flow restriction (BFR) increases muscle strength and size. However, the hemodynamics of BFR exercise appear elevated compared with non-BFR exercise. This questions the suitability of BFR in special/clinical populations. Nevertheless, hemodynamics of standard prescription protocols for BFR and traditional heavy-load exercise have not been compared. We investigated the hemodynamics of two common BFR exercise methods and two traditional resistance exercises. Twelve young males completed four unilateral elbow flexion exercise trials in a balanced, randomized crossover design: (a) heavy load [HL; 80% one-repetition maximum (1-RM)]; (b) light load (LL; 20% 1-RM); and two other light-load trials with BFR applied (c) continuously at 80% resting systolic blood pressure (BFR-C) or (d) intermittently at 130% resting systolic blood pressure (BFR-I). Hemodynamics were measured at baseline, during exercise, and for 60-min post-exercise. Exercising heart rate, blood pressure, cardiac output, and rate-pressure product were significantly greater for HL and BFR-I compared with LL. The magnitude of hemodynamic stress for BFR-C was between that of HL and LL. These data show reduced hemodynamics for continuous low-pressure BFR exercise compared with intermittent high-pressure BFR in young healthy populations. BFR remains a potentially viable method to improve muscle mass and strength in special/clinical populations.
    Scandinavian Journal of Medicine and Science in Sports 07/2014; DOI:10.1111/sms.12297 · 3.17 Impact Factor
    • "These results appear to be in line with the notion that isotonic low-intensity resistance exercise with BFR produces greater muscle hypertrophy compared with walking in combination with BFR (Loenneke et al. 2012a,b,c). The contrast in the magnitude of change in muscle mass may result from inherent differences in the exercise mode and/or external load to the working muscle (Abe et al. 2012). "
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    ABSTRACT: Walking combined with blood flow reduction (BFR-walk) elicits muscle hypertrophy. However, the skeletal muscle intracellular signaling behind this response is currently unknown. To investigate the effects of BFR-walk on mechanistic target of rapamycin (mTOR) and mitogen-activated protein kinase (MAPK) signaling pathways in young men. Six young men performed 20 minutes of treadmill walking at 55 % of their predetermined maximum oxygen uptake. A pressure cuff belt was applied to the most proximal thigh of only one leg (BFR-Leg, external compression was 240 mmHg) whereas the other leg (CON-Leg) was without BFR during walking. Muscle biopsies were taken from the vastus lateralis of the CON-Leg before exercise and in both legs 3 hours after exercise. Erk1/2 phosphorylation levels were significantly (p<0.05) increased after exercise in both legs, however, only the BFR-Leg saw an increased phosphorylation of p38. For mTOR signaling, there were no changes in Akt, mTOR, or S6K1 phosphorylation levels before or after walking. However, eEF2 phosphorylation level was significantly (p<0.05) lower for the BFR-Leg 3 hours after walking compared with CON-Leg. BFR-walk exercise may activate some intracellular signaling cascades that are associated with muscle hypertrophy in young men. This article is protected by copyright. All rights reserved.
    Acta Physiologica 01/2014; 211(1). DOI:10.1111/apha.12243 · 4.25 Impact Factor
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    • "Training at much lower than normal intensity could result in greater safety, and greater adherence to exercise in a variety of situations, while still enjoying the benefits (i.e., increases in muscle strength) of high-intensity training. Interested readers are referred to several recent reviews for more information about Kaatsu training (Abe et al., 2012; Manini et al., 2011; Wernbom, Augustsson & Raastad, 2008). Eight weeks of once daily Kaatsu training resulted in improved performances on functional outcome measures and 3 RM lower extremity strength measures in an older adult. "
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    ABSTRACT: Combining blood flow occlusion, Kaatsu, with a daily treadmill-walking program increases muscular strength in young, healthy men. Research using a similar training program in older adults is lacking. The present case study examined functional activity and body impairment responses to a daily walking program with Kaatsu in an older adult. The 67-year-old female participant walked at 0.85 m/s for five 2-min bouts with 1 min of rest between bouts, five times/week for 8 weeks with lower extremity Kaatsu cuffs inflated. Outcomes (Timed Up and Go, the Six Minute Walk Test, Ten Meter Walk Test, lower extremity strength measures) were collected at baseline, 2, 4, 6, and 8 weeks. Vitals were measured at the beginning and end of each walking session. Descriptives were calculated over time to determine the temporal effects of the Kaatsu-walk training program. All assessments, Timed Up and Go, Six Minute Walk Test, Ten Meter Walk Test, and lower extremity strength measures, increased 18.2% up to 46.8% from baseline to post-test. Data suggested that the 8-week Kaatsu-walk training program increases outcomes in an older adult.
    Physical & Occupational Therapy in Geriatrics 02/2013; 31(1). DOI:10.3109/02703181.2012.763149
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