Blood flow restriction reduces the increases in cardiorespiratory responses and subjective burden without inhibiting muscular activity during cycling at ventilatory threshold in healthy males.

Low-intensity endurance exercise with blood flow restriction (KAATSU) is under consideration for use in cardiac rehabilitation. However, the physiological responses to such exercise have not yet been fully characterized. In an initial effort in healthy males (n = 11, age: 26.3±4.6 y), we compared the physiological responses to low-intensity endurance exercise with and without a thigh KAATSU. Participants performed maximal graded exercise testing using a cycle ergometer with or without KAATSU. We examined responses to cycling exercise at ventilatory threshold (VT) in heart rate (HR), oxygen consumption (VO2), dyspnea, ratings of perceived exertion (RPE), blood pressure (BP), and rectus femoris activation. Participants reached VT at a lower mechanical load, HR, VO2, dyspnea, and double product (HR×systolic BP) with KAATSU vs. no-KAATSU. At VT, RPE, and rectus femoris activity did not differ between the two conditions. These results suggest that KAATSU reduced exercise intensity to reach VT and the physiological responses to exercise at VT without changes in knee extensor muscle activation. Results from this pilot study in healthy males suggest that KAATSU aerobic exercise at VT intensity has the potential to be an effective and low-burden adjuvant to cycling in cardiac rehabilitation.

Clinical usefulness of phase angle as an indicator of muscle wasting and malnutrition in inpatients with cardiovascular diseases.

Background and Objectives: Extracellular water is increased in patients with edema, such as those with chronic heart failure, and it is difficult to assess skeletal muscle mass with the skeletal muscle mass index when extracellular water is high. We investigated the relationship between phase angle and physical function, nutritional indices, and sarcopenia in patients with cardiovascular diseases, including chronic heart failure. Methods and Study Design: In 590 patients with cardiovascular diseases (372 men), handgrip strength, gait speed, and anterior mid-thigh muscle thickness by ultrasound were measured, and the skeletal muscle mass index, phase angle, and the extracellular water: total body water ratio were measured with a bioelectrical impedance analyzer, and presence of sarcopenia was evaluated. Results: Phase angle, but not the skeletal muscle mass index, was correlated with serum albumin (r = 0.377, p < 0.001) and hemoglobin values in women. Multivariate regression analysis showed that at the extracellular water: total body water ratio below 0.4, both phase angle and skeletal muscle mass index were independent determinants of handgrip strength and log mid-thigh muscle thickness in men, after adjustment for age and presence of chronic heart failure. In contrast, for the ratio of 0.4 or greater, after adjustment for age and presence of chronic heart failure, phase angle was a stronger independent determinant of handgrip strength and log mid-thigh muscle thickness than the skeletal muscle mass index in men. Conclusions: Phase angle is a good marker of muscle wasting and malnutrition in patients with cardiovascular disease, including chronic heart failure.

Low-Intensity Resistance Training with Moderate Blood Flow Restriction Appears Safe and Increases Skeletal Muscle Strength and Size in Cardiovascular Surgery Patients: A Pilot Study.

We examined the safety and the effects of low-intensity resistance training (RT) with moderate blood flow restriction (KAATSU RT) on muscle strength and size in patients early after cardiac surgery. Cardiac patients (age 69.6 ± 12.6 years, n = 21, M = 18) were randomly assigned to the control (n = 10) and the KAATSU RT group (n = 11). All patients had received a standard aerobic cardiac rehabilitation program. The KAATSU RT group additionally executed low-intensity leg extension and leg press exercises with moderate blood flow restriction twice a week for 3 months. RT-intensity and volume were increased gradually. We evaluated the anterior mid-thigh thickness (MTH), skeletal muscle mass index (SMI), handgrip strength, knee extensor strength, and walking speed at baseline, 5-7 days after cardiac surgery, and after 3 months. A physician monitored the electrocardiogram, rate of perceived exertion, and the color of the lower limbs during KAATSU RT. Creatine phosphokinase (CPK) and D-dimer were measured at baseline and after 3 months. There were no side effects during KAATSU RT. CPK and D-dimer were normal after 3 months. MTH, SMI, walking speed, and knee extensor strength increased after 3 months with KAATSU RT compared with baseline. Relatively low vs. high physical functioning patients tended to increase physical function more after 3 months with KAATSU RT. Low-intensity KAATSU RT as an adjuvant to standard cardiac rehabilitation can safely increase skeletal muscle strength and size in cardiovascular surgery patients.

Phase Angle as an Indicator of Sarcopenia, Malnutrition, and Cachexia in Inpatients with Cardiovascular Diseases.

Malnutrition is associated with sarcopenia, cachexia, and prognosis. We investigated the usefulness of phase angle (PhA) as a marker of sarcopenia, cachexia, and malnutrition in 412 hospitalized patients with cardiovascular disease. We analyzed body composition with bioelectrical impedance analysis, and nutritional status such as controlling nutritional status (CONUT) score. Both skeletal muscle mass index (SMI) and PhA correlated with age, grip strength and knee extension strength (p < 0.0001) in both sexes. The SMI value correlated with CONUT score, Hb, and Alb in males. Phase angle also correlated with CONUT score, Hb, and Alb in males, and more strongly associated with these nutritional aspects. In females, PhA was correlated with Hb and Alb (p < 0.001). In both sexes, sarcopenia incidence was 31.6% and 32.4%; PhA cut-off in patients with sarcopenia was 4.55° and 4.25°; and cachexia incidence was 11.5% and 14.1%, respectively. The PhA cut-off in males with cachexia was 4.15°. Multivariate regression analysis showed that grip strength and brain natriuretic peptide (BNP) were independent determinants of SMI, whereas grip strength, BNP, and Hb were independent determinants of PhA. Thus, PhA appears to be a useful marker for sarcopenia, malnutrition, and cachexia in hospitalized patients with cardiovascular disease.

Blood Flow Restriction Increases the Neural Activation of the Knee Extensors During Very Low-Intensity Leg Extension Exercise in Cardiovascular Patients: A Pilot Study.

Blood flow restriction (BFR) has the potential to augment muscle activation, which underlies strengthening and hypertrophic effects of exercise on skeletal muscle. We quantified the effects of BFR on muscle activation in the rectus femoris (RF), the vastus lateralis (VL), and the vastus medialis (VM) in concentric and eccentric contraction phases of low-intensity (10% and 20% of one repetition maximum) leg extension in seven cardiovascular patients who performed leg extension in four conditions: at 10% and 20% intensities with and without BFR. Each condition consisted of three sets of 30 trials with 30 s of rest between sets and 5 min of rest between conditions. Electromyographic activity (EMG) from RF, VL, and VM for 30 repetitions was divided into blocks of 10 trials and averaged for each block in each muscle. At 10% intensity, BFR increased EMG of all muscles across the three blocks in both concentric and eccentric contraction phases. At 20% intensity, EMG activity in response to BFR tended to not to increase further than what it was at 10% intensity. We concluded that very low 10% intensity exercise with BFR may maximize the benefits of BFR on muscle activation and minimize exercise burden on cardiovascular patients.