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Journal of alternative and complementary medicine (New York, N.Y.) 05/2013; · 1.69 Impact Factor
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International Journal of Clinical Medicine 02/2013; 4(2):114-121.
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ABSTRACT: It is known that ambulatory exercises such as brisk walking and jogging are potent stimuli for improving aerobic capacity, but it is less understood whether ambulatory exercise can increase leg muscle size and function. The purpose of this brief review is to discuss whether or not ambulatory exercise elicits leg muscle hypertrophy in older adults. Daily ambulatory activity with moderate (>3 metabolic equivalents [METs], which is defined as the ratio of the work metabolic rate to the resting metabolic rate) intensity estimated by accelerometer is positively correlated with lower body muscle size and function in older adults. Although there is conflicting data on the effects of short-term training, it is possible that relatively long periods of walking, jogging, or intermittent running for over half a year can increase leg muscle size among older adults. In addition, slow-walk training with a combination of leg muscle blood flow restriction elicits muscle hypertrophy only in the blood flow restricted leg muscles. Competitive marathon running and regular high intensity distance running in young and middle-aged adults may not produce leg muscle hypertrophy due to insufficient recovery from the damaging running bout, although there have been no studies that have investigated the effects of running on leg muscle morphology in older subjects. It is clear that skeletal muscle hypertrophy can occur independently of exercise mode and load.
Clinical Interventions in Aging 01/2013; 8:369-75. · 2.08 Impact Factor
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ABSTRACT: The purpose was to investigate the acute effects of blood flow restriction (BFR) on arterial and venous hemodynamic parameters. Nine participants completed a 10-min time control (resting condition) and then a lower body BFR protocol. The protocol was five, 5-min bouts of restrictive cuff inflation with 3-min of deflation between each bout. The pressure was set relative to each individual's thigh circumference. There were no significant differences between resting and BFR conditions for blood pressure or wave reflection. There was, however, a significant decrease in venous compliance and maximal venous outflow following BFR. Acute BFR with pressures relative to thigh circumference does not result in acute changes in blood pressure or wave reflection. There is, however, an acute decrease in venous compliance and maximal venous outflow, the significance of which is currently unknown. These results suggest that an acute BFR protocol affects venous but not arterial hemodynamics.
Clinical Physiology and Functional Imaging 01/2013; 33(1):79-82. · 1.33 Impact Factor
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Interventional Medicine and Applied Science. 12/2012; 4(4):217-220.
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ABSTRACT: Background and Aims: It is unknown whether the site-specific muscle loss of ageing muscle is associated with accelerometer-determined daily step count and/or the intensity of which the physical activity is completed. The purpose of this study was to examine the relationships between accelerometer-determined physical activity and lower body muscle size in women. Methods: Forty-eight women aged 52 to 76 years had their muscle thickness (MTH) measured by B-mode ultrasound at seven sites on the anterior and posterior aspects of their upper- and lower-leg. Daytime physical activity was measured using an accelerometer on 30 consecutive days and the total duration of each level of exercise intensity (light-PA, moderate-PA and vigorous-PA), average step count, and physical activity-related energy expenditure were calculated. Results: Age was inversely correlated with anterior 30% upper-leg MTH (r = - 0.296, P < 0.05), but not with other measured MTH sites. Light-PA was not significantly (p > 0.05) correlated with measured lower body MTH. However, moderate-PA was correlated (P < 0.05) with lower-leg MTH, while vigorous-PA was correlated (P < 0.05) with lower-leg and anterior 30% upper-leg MTH. Following adjustment for confounding factors, the anterior and posterior lower-leg MTH was positively correlated (P < 0.05) with duration of moderate-PA and vigorous-PA, as well as average step count. Conclusions: Thus daily moderate and vigorous physical activity was associated with higher muscle mass in the lower leg, but not in the upper-leg muscle, suggesting that the site-specific upper-leg muscle loss may not be prevented or attenuated by daily physical activity.
Aging - Clinical and Experimental Research 11/2012;
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The Journal of Physiology 11/2012; 590(Pt 21):5271. · 4.72 Impact Factor
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ABSTRACT: We sought to determine if blood flow restriction (BFR) by itself or in combination with exercise would result in prolonged decrements in torque when using restriction pressures relative to the participants' limb size. Sixteen participants were randomized into Experiment A (n = 9) or Experiment B (n = 7). Experiment A participants performed unilateral knee extensions at 30 % of their one repetition maximum (1RM) with moderate blood flow restriction on one leg (BFR + Exercise) and exercised the other leg without BFR (CON + Exercise). Experiment B participants rested for 4 min with BFR applied to one leg and rested for 4 min without any treatment on the other leg (CON). Maximal voluntary isometric torque (MVC) was measured before and immediately after the exercise or 4 min of rest, 1 h post, and 24 h post. Ratings of perceived exertion (RPE) and discomfort were taken before and after each set. MVC was significantly reduced following both exercise conditions with BFR + Exercise having the largest reduction in torque. However, torque quickly recovered by 1 h post exercise and was back to baseline by 24 h. No changes in torque were observed in Experiment B. RPE and discomfort were rated consistently higher for those in the BFR + Exercise and BFR conditions compared to control. In conclusion, BFR + Exercise does not result in prolonged decrements in torque. The acute changes in torque are due to fatigue and quickly recover back to baseline within 24 h of exercise. In addition, BFR in the absence of exercise has no effect on torque at any time point.
Arbeitsphysiologie 09/2012; · 2.15 Impact Factor
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ABSTRACT: The purpose of this study was to determine (i) the cardiovascular responses to acute blood-flow-restricted (BFR) resistance exercise and (ii) the influence of applied BFR cuff type on the cardiovascular and perceptual responses.
In a randomized, crossover design, 27 participants wore either a 5·0 cm wide elastic cuff or a 13·5 cm wide non-elastic cuff around the thigh while performing four sets of knee extension exercise using 20% of 1-RM. Brachial and central blood pressure (BP) and aortic augmentation index (AIx) were measured before and after the restrictive cuffs were applied and inflated, after the 2nd and 4th set of resistance exercise, and 5 and 15 min following the 4th set of exercise. Ratings of perceived exertion and pain were obtained before exercise and after the 2nd and 4th set of exercise.
Both brachial and central BPs increased and AIx decreased during BFR exercise but returned to baseline levels within 15 min following exercise. The wide cuffs caused a greater elevation in heart rate, brachial and central BPs, perceived effort and pain and a greater decrease in AIx during the BFR exercise.
These findings suggest that low-intensity BFR resistance exercise does not appear to acutely negatively affect the vasculature. Also, cuff type will greatly affect cardiovascular and perceptual responses to BFR resistance exercise and thus is an important consideration in study design.
Clinical Physiology and Functional Imaging 09/2012; 32(5):331-7. · 1.33 Impact Factor
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ABSTRACT: Abstract Background: It is unknown whether severe sarcopenia produces unfavorable effects on cardiovascular risk factors. To examine the influence of severe and moderate sarcopenia on selected cardiovascular risk factors, 687 men were screened; those exhibiting clinically relevant diseases and higher body fat percentage (>25% fat) were excluded. A total of 410 men aged 40-76 years (mean age 56.0 years) were used for data analyses. Methods: Sarcopenia was defined as a skeletal muscle mass (SM) index (muscle mass/height squared) of 1-2 standard deviations (SD) below (moderate) or <2 SDs below (severe) the mean for young adult men. Ultrasound-measured subcutaneous fat and muscle thicknesses were used to estimate the SM, percent body fat, and fat-free mass. Serum total cholesterol (TC) and high-density lipoprotein cholesterol (HDL-C) levels were determined using fasting blood samples. Systolic blood pressure and diastolic blood pressure were also measured. Results: HDL-C was similar among the groups, but TC was lower in severe and moderate sarcopenia groups compared to the normal group. As a result, the TC:HDL-C ratio was lower in the moderate and severe sarcopenia groups than in the normal group. After adjusting for age, body mass index (BMI), waist circumference, and percent body fat, HDL-C was lower in both sarcopenia groups compared to the normal group, but other parameters were similar among the groups. A low prevalence of high HDL-C and high prevalence of moderate HDL-C were observed in the severe and the moderate sarcopenia groups. Conclusion: Our results suggest that moderate and severe sarcopenia may influence the HDL-C level, although the values are still maintained in the clinically normal range.
Metabolic syndrome and related disorders 07/2012;
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ABSTRACT: Sarcopenia is observed as a site-specific loss of skeletal muscle mass, however, it is unknown whether the site-specific sarcopenia is associated with development of physical disability. The purpose of this study was to examine the relationship between age-related thigh muscle loss and gait performance. Fifty-three women aged 52-83 years had their thigh muscle thickness (MTH) measured by ultrasound at five sites on the anterior (30%, 50%, and 70% of thigh length) and posterior (50% and 70% of thigh length) aspects of their thigh. Maximum and normal walking speeds, zig-zag walking time, and maximal voluntary isometric knee extension and flexion strength were measured. Age was inversely correlated to the anterior and posterior MTH ratio (e.g., anterior 50%:posterior 70% MTH ratio [r=-0.426, p=0.002]), thus the site-specific muscle loss of the thigh was observed in the present sample. There were no significant correlations between the anterior/posterior MTH ratio and maximum and normal walking speeds. However, the ratios of anterior 50%:posterior 70% MTH (r=-0.430) and anterior 30%:posterior 70% MTH (r=-0.444) were correlated (p=0.001) to zig-zag walking test. After adjusting for age, height and weight, the anterior 30%:posterior 70% MTH (r=-0.292, p=0.040) was inversely correlated to zig-zag walking performance. Isometric knee extension strength was also inversely correlated to zig-zag walking. Our results suggest that an age-related loss of adductor/quadriceps muscles may be associated with a decrease in a relatively difficult task performance such as zig-zag walking.
Archives of gerontology and geriatrics 07/2012; 55(2):e21-5. · 1.36 Impact Factor
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ABSTRACT: Skeletal muscle may be viewed as an endocrine organ that releases numerous factors with the potential to influence vascular tone. Previous cross-sectional studies have shown an inverse relationship between muscle mass and arterial stiffness. We examined the relationship between muscle mass, arterial pressure in the aorta and brachial artery, and pressure from wave reflections [characterized as heart rate corrected augmentation pressure (AP)] and augmentation index (AIx). Twenty-seven (13 male, 14 female) subjects who were non-smokers and had no known cardiovascular or metabolic diseases visited the laboratory for two sessions of testing. Upon arriving for the first session, mid-thigh muscle (mCSA) and fat (fCSA) cross-sectional area were assessed using peripheral Quantitative Computed Tomography. Following this, concentric one-repetition maximum (1-RM) testing was completed to assess knee extensor strength. The second visit consisted of taking brachial and aortic blood pressure measurements. A significant positive relationship was found between mCSA and brachial systolic blood pressure (r = 0.47, p = 0.02), but not between mCSA and aortic systolic blood pressure (r = 0.35, p = 0.09). There was an inverse association between mCSA and AP75 (-0.49, p = 0.01) and AIx75 (-0.49, p = 0.01). In conclusion, muscle mass is associated with brachial systolic blood pressure and inversely associated with pressure from wave reflections. Our findings suggest a link between global musculo-skeletal integrity and cardiovascular hemodynamics in young healthy adults.
Arbeitsphysiologie 07/2012; · 2.15 Impact Factor
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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.
Clinical Physiology and Functional Imaging 07/2012; 32(4):247-52. · 1.33 Impact Factor
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ABSTRACT: We investigated the acute and chronic effects of low-intensity concentric or eccentric resistance training with blood flow restriction (BFR) on muscle size and strength. Ten young men performed 30% of concentric one repetition maximal dumbbell curl exercise (four sets, total 75 reps) 3 days/week for 6 weeks. One arm was randomly chosen for concentric BFR (CON-BFR) exercise only and the other arm performed eccentric BFR (ECC-BFR) exercise only at the same exercise load. During the exercise session, iEMG for biceps brachii muscles increased progressively during CON-BFR, which was greater (p<0.05) than that of the ECC-BFR. Immediately after the exercise, muscle thickness (MTH) of the elbow flexors acutely increased (p<0.01) with both CON-BFR and ECC-BFR, but was greater with CON-BFR (11.7%) (p<0.01) than ECC-BFR (3.9%) at 10-cm above the elbow joint. Following 6-weeks of training, MRI-measured muscle cross-sectional area (CSA) at 10-cm position and mid-upper arm (12.0% and 10.6%, respectively) as well as muscle volume (12.5%) of the elbow flexors were increased (p<0.01) with CON-BFR. Increases in muscle CSA and volume were lower in ECC-BFR (5.1%, 0.8% and 2.9%, respectively) than in the CON-BFR and only muscle CSA at 10-cm position increased significantly (p<0.05) after the training. Maximal voluntary isometric strength of elbow flexors was increased (p<0.05) in CON-BFR (8.6%), but not in ECC (3.8%). These results suggest that CON-BFR training leads to pronounced acute changes in muscle size, an index of muscle cell swelling, the response to which may be an important factor for promoting muscle hypertrophy with BFR resistance training.
PLoS ONE 01/2012; 7(12):e52843. · 4.09 Impact Factor
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ABSTRACT: Low-intensity resistance exercise combined with blood flow restriction has been shown to produce comparable increases in muscle strength and hypertrophy as traditional high-intensity (HI) resistance training. However, the vascular effects of low-intensity blood flow-restricted (LI-BFR) exercise training are not well characterized. Therefore, the purpose of this study was to compare the vascular effects of LI-BFR, moderate-intensity (MI), and HI resistance exercise training. Forty-six young men were divided into four groups: a HI, MI or LI-BFR lower body resistance training group or a non-exercise control group (C). Blood pressure, arterial compliance and calf vascular conductance (CVC) were assessed before and after the 6-week intervention. After the intervention, CVC was significantly increased in the three exercise groups combined compared with C (47·5 ± 3·1 versus 35·0 ± 4·5 flow per mmHg) without any changes in arterial compliance in any group. These results suggest HI, MI and LI-BFR lower body resistance exercises increase CVC, but do not affect arterial compliance. LI-BFR resistance exercise may be an effective alternative to HI resistance exercise for improving vascular conductance for individuals unable to perform HI resistance exercise. As more evidence concerning the safety and efficacy of LI-BFR resistance exercise continues to mount, this may provide a research base for prescribing this type of exercise if and/or when this type of exercise becomes more available worldwide.
Clinical Physiology and Functional Imaging 01/2012; 32(1):45-51. · 1.33 Impact Factor
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ABSTRACT: The purpose of this study was to determine the difference in cuff pressure which occludes arterial blood flow for two different types of cuffs which are commonly used in blood flow restriction (BFR) research. Another purpose of the study was to determine what factors (i.e., leg size, blood pressure, and limb composition) should be accounted for when prescribing the restriction cuff pressure for this technique. One hundred and sixteen (53 males, 63 females) subjects visited the laboratory for one session of testing. Mid-thigh muscle (mCSA) and fat (fCSA) cross-sectional area of the right thigh were assessed using peripheral quantitative computed tomography. Following the mid-thigh scan, measurements of leg circumference, ankle brachial index, and brachial blood pressure were obtained. Finally, in a randomized order, arterial occlusion pressure was determined using both narrow and wide restriction cuffs applied to the most proximal portion of each leg. Significant differences were observed between cuff type and arterial occlusion (narrow: 235 (42) mmHg vs. wide: 144 (17) mmHg; p = 0.001, Cohen's D = 2.52). Thigh circumference or mCSA/fCSA with ankle blood pressure, and diastolic blood pressure, explained the most variance in the cuff pressure required to occlude arterial flow. Wide BFR cuffs restrict arterial blood flow at a lower pressure than narrow BFR cuffs, suggesting that future studies account for the width of the cuff used. In addition, we have outlined models which indicate that restrictive cuff pressures should be largely based on thigh circumference and not on pressures previously used in the literature.
Arbeitsphysiologie 12/2011; 112(8):2903-12. · 2.15 Impact Factor
