**2. BFRT in patients with cardiovascular comorbidities**

Research examining the safety of BFR exercise and training has thus far concluded that BFR exercise is a safe and novel method not only for training athletes and healthy persons but also it could be a beneficial training method for athletes/ patients (post-surgery or injury situations) and for vulnerable populations and individuals with varying comorbidities where exercise options are limited [34, 52].

Furthermore, Abe et al. [53]; and Conceição et al. [54]; reported positive effects of BFRT regarding muscle strength, mass, and cardiorespiratory capacity when it is combined with low intensity walking or cycling. Abe et al. examined the acute and chronic effects of walk training with and without KAATSU on MRI-measured muscle size and maximum dynamic (one repetition maximum) and isometric strength, along with blood hormonal parameters. Eighteen healthy men volunteered to participate in this study. Nine men performed BFR-walk training, and nine men performed walk training alone (control-walk). Training was conducted two times a day, 6 days/wk., for 3 wk. using five sets of 2-min bouts (treadmill speed at 50 m/min), with a 1-min rest between bouts. For the BFR-walk training group, a restriction pressure of 160–230 mmHg was selected for the occlusive stimulus, as this pressure has been suggested to restrict venous blood flow and cause pooling of blood in capacitance vessels distal to the restriction point, as well as restricting arterial blood flow [55]. They conclude that BFR with slow-walk training induces muscle hypertrophy and strength gain, despite the minimal level of exercise intensity. Moreover, Conceicao et al. assessed the effects of BFR endurance training compared with conventional endurance training and resistance training in functional, morphological, and molecular responses. They examined 30 healthy men who were randomly assigned to the endurance BFR group, to the endurance conventional training group, and to the resistance conventional training group. All the groups performed eight weeks of training protocol. The endurance BFR group underwent 30 minutes cycling at 40% of VO2max, four days per week, while the conventional group performed 30 minutes cycling at 70% of VO2max, four days per week. In the BFR endurance group, cuff pressure was set at 80% of the maximum tibial arterial pressure (approximately 95 mmHg). The resistance training group performed four sets of ten leg press reps at 70% of 1RM with 60 seconds rest, four days per week. They suggest that BFR endurance training could increase muscle strength and induce similar hypertrophy stimulation to resistance training, while cardiorespiratory capacity could be improved even with a significantly lower workload compared to conventional endurance training. Altogether, this suggests

that BFRT could be a potentially safe training method, particularly for older adults or clinical cohorts incapable of exercising at high training loads.

Moreover, Cezar et al. showed that eight weeks of wrist flexion exercise training with 30% of maximum dynamic force with vascular occlusion (70% of the resting SBP) was sufficient to reduce blood pressure in medicated hypertensive subjects [56]. Twenty-three women were randomly assigned to three groups: one was the control group and the other two underwent eight weeks of training performed twice a week, including three series of wrist flexion exercises with or without vascular occlusion. Blood pressure was assessed before each session and based on that measurement (blood pressure at rest), occlusion pressure was determined for use during exercise in the BFRT group. The cuff pressure was equivalent to 70% of the subject's resting systolic pressure (maintained from the beginning of the exercise period until the end of the last series). The exercised with occlusion group showed a pre- to post-test reduction in systolic and diastolic blood pressure, mean arterial pressure, and double product, whereas the other groups showed no significant hemodynamic changes.

Despite the positive adjustments of low-intensity aerobic exercise with BFR techniques, no research has been done to evaluate the effects of this type of exercise program on cardiovascular patients. Only one study has looked at short-term hemodynamic adjustments after low-intensity aerobic BFR in elderly hypertensive women, highlighting the potential benefits of this type of exercise in hypertensive patients [57]. Specifically, Barili et al. examined the acute responses of cardiorespiratory and oxidative stress parameters to low intensity aerobic exercise (LIAE) with blood flow restriction (BFR) in hypertensive elderly women. Each subject performed in random order three experimental protocols: (a) high intensity aerobic exercise (HIAE): 50% of the estimated maximum oxygen consumption; (b) low intensity aerobic exercise (LIAE): 30% of the estimated maximum oxygen consumption; and (c) low intensity aerobic exercise with blood flow restriction (LILIAE+BFR): 30% of the estimated maximum oxygen consumption and occlusion pressure equivalent to 130% of the measured systolic blood pressure at rest. Blood samples were collected at three different times: at rest, immediately after each exercise protocol, and after 30 min of recovery. The findings support the indication of low-intensity aerobic exercise with BFR, with potential benefits for the hypertensive elderly population.

Only five research attempts have examined the effect of low resistance BFRT in cardiovascular patients with positive results in terms of muscle strength, mass, and hypertrophy as well as the functionality of these patients [52, 58–61]. However, three of these studies are characterized by serious methodological problems as they are pilot studies and do not draw definitive conclusions [58–60]. In particular, they reported positive results in improving muscle strength and functionality without increasing the risk of adverse effects through hemostatic and inflammatory responses. Madarame et al. [60] investigated the haemostatic and inflammatory responses to BFR exercise in nine stable patients with ischaemic heart disease. The patients performed four sets of bilateral knee extension exercises with a load of 20% 1RM either with or without BFR. In each exercise session (total two separated at least by one week), one set of 30 repetitions was followed by three sets of 15 repetitions with 30 seconds of rest between each set. During the BFRT, the cuff was attached to the proximal portions of the thighs and compressed at a pressure of 200 mmHg. The cuff was kept throughout the session, including rest periods between sets, and was released immediately after the session. Blood samples were obtained before, immediately after, and 1 hour after the exercise. They suggest that low-intensity resistance exercise with BFR would be relatively safe for stable IHD patients, at least in terms of haemostatic and inflammatory responses.

#### *Blood Flow Restriction Training in Cardiovascular Disease Patients DOI: http://dx.doi.org/10.5772/intechopen.96076*

Similar results were reported by Kambic et al. [58], who assessed the safety and efficacy of BFR resistance training in patients with coronary artery disease (CAD) compared to usual care. Twenty-four participants were included in this study: 12 (control group) performed conventional care (aerobic exercise training), while in the intervention group (n = 12), BFRT was added on usual care. Subjects in the BFR resistance training group trained for eight weeks, performing a total of 16 unilateral leg extension exercise sessions. During each week, two exercise sessions were performed with a 48-hour rest period in between. Each training session consisted of three sets of 8, 10, and 12 repetitions in the first, second, and third sets, respectively, with a 45-second inter-set rest interval. The load was set at 30% of 1RM. The cuff was inflated between 15 and 20 mmHg greater than resting brachial systolic pressure, and the pressure was maintained throughout the entire training session and was released at the end of the last set. Findings report that BFR resistance training is safe and associated with significant improvements in muscle strength and may therefore be provided as an additional exercise option to aerobic exercise to improve skeletal muscle functioning in patients with CAD.

Nakajima et al. [52]; also showed improvement in muscle strength and endurance in patients with cardiovascular disease after a low-resistance BFR program for three months with two workouts per week, while Fakuda et al. [61]; evaluated muscle activation in the biceps using low-resistance BFR compared to low-resistance exercise and showed that the BFR subgroup showed statistically significantly greater activation than the low-resistance exercise subgroup, suggesting that BFR could be a valuable tool for improving muscle hypertrophy in cardiovascular patients. However, it should be noted that the last two studies have been published in a newspaper dealing only with BFR (Int. J. KAATSU Training).
