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Studies pertaining to kaatsu / long duration isometrics / hypoxia / altitude training.

A given level of hypoxic conditions occur in traditional weightlifting etc, can include studies on that also.

whatever!



x. Muscle size and strength are increased following walk training with restricted venous blood flow from the leg muscle, Kaatsu-walk training

   
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x. The history and future of KAATSU Training

KAATSU training involves the restriction of blood flow to exercising muscle and is the culmination of nearly 40 years of experimentation with the singular purpose of increasing muscle mass. KAATSU Training consists of performing low-intensity resistance training while a relatively light and flexible cuff is placed on the proximal part of one's lower or upper limbs, which provides appropriate superficial pressure. KAATSU Training should not be confused with training under ischemic conditions which has previously been reported (Sundberg, 1994). KAATSU Training does not induce ischemia within skeletal muscle, but rather promotes a state of blood pooling in the capillaries within the limb musculature. Applied basic and clinical research conducted over the past 10 years has demonstrated that KAATSU Training not only improves muscle mass and strength in healthy volunteers, but also benefits patients with cardiovascular and orthopedic conditions.

x. Muscle fiber cross-sectional area is increased after two weeks of twice daily KAATSU-resistance training

The purpose of this study was to examine the effect of low-intensity (20% of 1-RM) resistance training (LIT) combined with restriction of muscular venous blood flow (KAATSU) on muscle fiber size using a biopsy sample. Three young men performed LIT-KAATSU (restriction pressure 160-240 mmHg), and two young men performed LIT alone. Training was conducted twice daily for 2 weeks using 3 sets of two dynamic lower body exercises. Quadriceps muscle CSA was measured by magnetic resonance imaging at midpoint of the thigh. Muscle biopsies were obtained from the vastus lateralis (VL) muscle using a needle biopsy. Mean relative change in 1-RM squat strength was 14% in the LIT-KAATSU and 9% in the LIT after two weeks of the training. Mean changes in quadriceps muscle CSA was 7.8% for LIT-KAATSU and 1.8% for LIT. Changes in muscle fiber CSA was 5.9% for type-I and 27.6% (p<0.05) for type-II in the LIT-KAATSU, and -2.1% and 0.5%, respectively, in the LIT. Mean fiber CSA changed 17.0% in the LIT-KAATSU, but not in LIT (-0.4%). We concluded that skeletal muscle and fiber hypertrophy, especially type-II fiber, occur after high frequency KAATSU training.

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x. Hemodynamic and autonomic nervous responses to the restriction of femoral blood flow by KAATSU

x. Hemodynamic and neurohumoral responses to the restriction of femoral blood flow by KAATSU in healthy subjects

Abstract  The application of an orthostatic stress such as lower body negative pressure (LBNP) has been proposed to minimize the effects of weightlessness on the cardiovascular system and subsequently to reduce the cardiovascular deconditioning. The KAATSU training is a novel method to induce muscle strength and hypertrophy with blood pooling in capacitance vessels by restricting venous return. Here, we studied the hemodynamic, autonomic nervous and hormonal responses to the restriction of femoral blood flow by KAATSU in healthy male subjects, using the ultrasonography and impedance cardiography. The pressurization on both thighs induced pooling of blood into the legs with pressure-dependent reduction of femoral arterial blood flow. The application of 200 mmHg KAATSU significantly decreased left ventricular diastolic dimension (LVDd), cardiac output (CO) and diameter of inferior vena cava (IVC). Similarly, 200 mmHg KAATSU also decreased stroke volume (SV), which was almost equal to the value in standing. Heart rate (HR) and total peripheral resistance (TPR) increased in a similar manner to standing with slight change of mean blood pressure (mBP). High-frequency power (HFRR) decreased during both 200 mmHg KAATSU and standing, while low-frequency/high-frequency power (LFRR/HFRR) increased significantly. During KAATSU and standing, the concentration of noradrenaline (NA) and vasopressin (ADH) and plasma renin activity (PRA) increased. These results indicate that KAATSU in supine subjects reproduces the effects of standing on HR, SV, TPR, etc., thus stimulating an orthostatic stimulus. And, KAATSU training appears to be a useful method for potential countermeasure like LBNP against orthostatic intolerance after spaceflight.

   
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x. Acute growth hormone response to low-intensity KAATSU resistance exercise: Comparison between arm and leg

Exercise is a potent stimulus to GH secretion. However it is unclear if exercise-induced GH release differs between different muscle groups, i.e., arm and leg exercise, when performed at equivalent exercise intensity. The purpose of this study was to compare the GH responses to an acute resistance exercise, combined with restriction of muscular venous blood flow (KAATSU), in muscle groups of the arm and leg. Five young male subjects performed two types of exercise tests, arm and leg exercise, on separate days. The intensity of exercise was 20% of 1-RM, which was measured at least 1 week before the experiment. The external restriction pressure during the KAATSU exercise was selected 50% higher than each measured-arm and estimated-leg systolic blood pressure. Venous blood samples were obtained prior to the start of exercise, immediately post exercise, and 15- and 60-min after exercise, and blood lactate (LA), growth hormone (GH), noradrenaline (NA), hematocrit, albumin and Na/K concentrations were measured. Significant elevations were apparent immediately post and 15-min after exercise for LA and at immediately post, 15- and 60-min after exercise for GH in both arm and leg exercise. Significant elevation was also observed after exercise for NA in both arm and leg, but leg exercise resulted in a greater increase in NA than arm at immediately post exercise. Change in plasma volume after exercise was not different between two exercises. These results suggest that GH secretory responses to exercise may be similar between the arm and leg when performed at equivalent exercise intensity and restriction stimulus.

x. KAATSU-walk training increases serum bone-specific alkaline phosphatase in young men

Previous research has shown that high intensity resistance training causes increases in bone density and increases in serum measures of bone turnover like bone-specific alkaline phosphatase (BAP). Medium intensity or low intensity training (like walking) does not result in these changes. However, low intensity training with blood flow restriction (KAATSU) has shown promise in bone and muscle rehabilitation settings. We hypothesized that there would be increases in serum BAP following low intensity KAATSU walk training. Healthy men walked on a treadmill twice per day (at least 4 hours between sessions) for 3 weeks with (KAATSU; n=9) or without (Control; n=9) blood flow occlusion pressure belts on their thighs. After three weeks of training, the KAATSU group experienced significant increases in MRI-measured muscle CSA (P<0.01), 1-RM muscle strength (P<0.01), and serum BAP levels (P<0.05). Percent change in BAP was 10.8% for the KAATSU-walk and 0.3% for the Control-walk. There was no significant change in serum IGF-1 for either group. We conclude that 3 weeks KAATSU walk training increases BAP, a serum marker of bone turnover.

   
x. Electromyographic responses of arm and chest muscle during bench press exercise with and without KAATSU

The purpose of this study was to compare the EMG activity of blood flow restricted (limb) and nonrestricted (trunk) muscles during multi-joint exercise with and without KAATSU. Twelve (6 women and 6 men) healthy college students [means (SD) age: 24.1 (3.5) yrs] performed 4 sets (30, 15, 15, and 15 reps) of flat bench press exercise (30% of a predetermined one repetition maximum, 1-RM) during two different conditions [with KAATSU and without KAATSU (Control)]. In the KAATSU condition, a specially designed elastic cuff belt (30 mm wide) was placed at the most proximal position of the upper arm and inflated to a pressure of 100% of individual's resting systolic blood pressure. Surface EMG was recorded from the muscle belly of the triceps brachii (TB) and pectoralis major (PM) muscles, and mean integrated EMG (iEMG) was analyzed. During 4 sets of the exercise, gradual increases in iEMG were observed in both TB and PM muscles for the KAATSU condition. The magnitude of the increases in iEMG in the TB and PM muscles were higher (P<0.05) with KAATSU compared to the Control condition. In the first set, the mean exercise intensity from normalized iEMG was approximately 40% of 1-RM in both Control and KAATSU conditions. However, the mean exercise intensity of both muscles were 60-70% of 1-RM for the KAATSU condition and only about 50% of 1-RM for the Control condition, respectively, during the fourth set. We concluded that increases in iEMG in the trunk muscle during KAATSU might be an important factor for KAATSU training-induced trunk muscle hypertrophy.

x. Eight days KAATSU-resistance training improved sprint but not jump performance in collegiate male track and field athletes

The purpose of this study was to investigate the effects of short-term KAATSU-resistance training on skeletal muscle size and sprint/jump performance in college athletes. Fifteen male track and field college athletes were randomly divided into two groups: KAATSU (resistive exercise combined with blood flow restriction, n=9) and control (n=6) groups. The KAATSU group trained twice daily with squat and leg curl exercises (20% of 1-RM, 3 sets of 15 repetitions) for 8 consecutive days while both KAATSU and control groups participated in the regular sprint/jump training sessions. Maximal strength, muscle-bone CSA, mid-thigh muscle thickness (MTH), and sprint/jump performance were measured before and after the 8 days of training. The muscle-bone CSA increased 4.5% (p<0.01) in the KAATSU group but decreased 1% (p>0.05) in the control group. Quadriceps and hamstrings MTH increased (p<0.01) by 5.9% and 4.5%, respectively, in the KAATSU group but did not change in the control group. Leg press strength increased (9.6%, p<0.01) in the KAATSU group but not (4.8%, p>0.05) in the control group. Overall 30-m dash times improved (p<0.05) in the KAATSU-training group, with significant improvements (p<0.01) occurring during the initial acceleration phase (0-10m) but not in the other phases (10-20m and 20-30m). None of the jumping performances improved (p>0.05) for either the KAATSU or control groups. These data indicated that eight days of KAATSU-training improved sprint but not jump performance in collegiate male track and field athletes.

x. Day-to-day change in muscle strength and MRI-measured skeletal muscle size during 7 days KAATSU resistance training: A case study

The purpose of this study was to examine the daily skeletal muscle hypertrophic and strength responses to one week of twice daily KAATSU training, and follow indicators of muscle damage and inflammation on a day-to-day basis, for one subject. KAATSU training resulted in a 3.1% increase in muscle-bone CSA after 7 days of training. Both MRI-measured maximum quadriceps muscle cross-sectional area (Q-CSA max) and muscle volume can be seen increasing after the first day of KAATSU training, and continuously increasing for the rest of the training period. Following 7 days KAATSU resistance training, the increases in Q-CSA max and muscle volume were 3.5% and 4.8%, respectively. Relative strength (isometric knee extension strength per unit Q-CSA max) was increased after training (before, 3.60 Nm/cm2; after, 4.09 Nm/cm2). There were very modest increases in CK and myoglobin after a single bout of KAATSU exercise in the first day of the training, but the values were return towards normal at 2 days after the training. IL-6 remained unchanged throughout the training period. In conclusion, our subject gained absolute strength and increased muscle size after only one week of low intensity KAATSU resistance training. Indicators of muscle damage and inflammation were not elevated by this training. KAATSU training appears to be a safe and effective method to rapidly induce skeletal muscle strength and hypertrophy.

     
x. Use and safety of KAATSU training:Results of a national survey

KAATSU training is a novel training, which is performed under conditions of restricted blood flow. It can induce a variety of beneficial effects such as increased muscle strength, and it has been adopted by a number of facilities in recent times. The purpose of the present study is to know the present state of KAATSU training in Japan and examine the incidence of adverse events in the field. The data were obtained from KAATSU leaders or instructors in a total of 105 out of 195 facilities where KAATSU training has been adopted. Based on survey results, 12,642 persons have received KAATSU training (male 45.4%, female 54.6%). KAATSU training has been applied to all generations of people including the young (<20 years old) and the elderly (>80 years old). The most popular purpose of KAATSU training is to strengthen muscle in athletes and to promote the health of subjects, including the elderly. It has been also applied to various kinds of physical conditions, cerebrovascular diseases, orthopedic diseases, obesity, cardiac diseases, neuromuscular diseases, diabetes, hypertension and respiratory diseases. In KAATSU training, various types of exercise modalities (physical exercise, walking, cycling, and weight training) are used. Most facilities have used 5-30 min KAATSU training each time, and performed it 1-3 times a week. Approximately 80% of the facilities are satisfied with the results of KAATSU training with only small numbers of complications reported. The incidence of side effects was as follows; venous thrombus (0.055%), pulmonary embolism (0.008%) and rhabdomyolysis (0.008%). These results indicate that the KAATSU training is a safe and promising method for training athletes and healthy persons, and can also be applied to persons with various physical conditions.

x. Muscle, tendon, and somatotropin responses to the restriction of muscle blood flow induced by KAATSU-walk training.

OBJECTIVE: The efficacy of KAATSU training has been demonstrated in human athletes, both as a therapeutic method as well as a training aid. The purpose of this study was to investigate the effects of slow walk training combined with restriction of muscle blood flow (KAATSU) on muscle and tendon size. METHODS: Six healthy, unfit Standardbred mares performed walking (240 m/min for 10 min and then 5 min recovery) with KAATSU, and 6 mares performed walking without KAATSU. A specially designed elastic cuff1 was placed at the most proximal position of the forelegs and inflated to a pressure of 200-230 mmHg throughout the walking and recovery sessions. The training was conducted once a day, 6 days/week for 2 weeks. Skeletal muscle thickness and tendon thickness were measured using B-mode ultrasound at baseline and after 2 weeks of training. Venous blood samples were obtained before the first acute exercise and 5, 15 and 60 min afterwards. Serum somatotropin concentration was determined using a commercially available equine-specific ELISA kit. RESULTS: The acute increase in plasma somatotropin was 40% greater (P<0.05) in the KAATSU-walk group than in the Control-walk group 5 min after exercise and remained elevated (P<0.05) at 15 and 60 min post exercise compared with the Control-walk group. After 2 weeks of training, muscle thickness increased (P<0.05) 3.5% in the KAATSU-walk group but did not change in the Control-walk group (0.7%). Tendon thickness did not change (P>0.05) in either group. CONCLUSIONS: These data demonstrate that KAATSU training can induce muscle hypertrophy in horses and suggest that KAATSU training may provide significant therapeutic/ rehabilitative value in horses, as has been shown in man.

x. Kaatsu training for patella tendinitis patient

Low-intensity Kaatsu resistance training performed by patients with moderate vascular occlusion is known to cause skeletal muscle hypertrophy over a short term. In our patients who used such training as a part of their rehabilitation, we have seen the same results, as well as a quenching analgesic effect. Herein, we report the effect of Kaatsu resistance training in a patient with patella tendinitis. The patient was a 17-year-old male who played basketball and came to us with intense pain at the lower edge of the patella in the right knee and was confirmed by an MRI image which showed a high intensity signal in the area of the patella tendon. Initially, we gave a dose of antiphlogistic analgetic, a steroid injection, and prescribed hospitalization for 1 month. Kaatsu resistance training was also recommended in an attempt to prevent muscle atrophy. The vascular occlusion point for the Kaatsu training cuff was the proximal end of the right limb, which had an occlusion pressure ranging from 160-180 mmHg. The exercise components that were used in combination with the Kaatsu training program were SLR, hip abduction, hip adduction, calf raise, toe raise, squat, crunch, back extension, and shooting. The exercise protocol was performed at about 30% of 1RM, with 3 sets of 15 repetitions, 5 to 6 times per week, for 3 weeks. T2 weighted MRI images (axial and sagittal) of the right patella tendon prior to beginning Kaatsu training showed high intensity signals, however, after 3 weeks of Kaatsu training, the signal intensity was reduced and the thigh circumference was increased by 7 mm and 2 mm for the right and left sides, respectively. Further, there was no evidence of muscle atrophy. The present patient was then treated with appropriate anti-inflammatory drugs and 1-month of hospitalization. During that time it was possible to completely relieve the inflammation and avoid muscle atrophy with Kaatsu training, and the patient quickly returned to playing basketball. In conclusion, this low-intensity resistance training was able to be performed without applying excessive load, which may have caused further damage, and we intend to use Kaatsu training with future patients to help them return as early as possible to full activities.

x. Effects of KAATSU training on haemostasis in healthy subjects

     
x. Overview of neuromuscular adaptations of skeletal muscle to KAATSU Training

Skeletal muscle adapts to a progressive overload, but the response can vary between different modes and intensities of exercise. Generally, a minimal threshold intensity of 65% of the one repetition maximum (1-RM) is needed to elicit muscle hypertrophy; however, recent studies have challenged this hypothesis and have provided evidence that low-intensity training (LIT) combined with vascular restriction (KAATSU) may also elicit increases in muscle size and strength. The physiological aspects of applying vascular restriction during exercise are not fully understood and may be explained by several factors. Examining the results of previous studies may help elucidate the factors responsible for the adaptations associated with vascular restriction in humans. Therefore, the objectives of this review are to summarize current knowledge regarding the physiological adaptations of skeletal muscle after low-intensity exercise combined with vascular restriction, the different training protocols used to elicit adaptations, and suggested areas for future research.

   
x. Effects of KAATSU on muscular function during isometric exercise

x. Hemodynamic responses to simulated weightlessness of 24-h head-down bed rest and KAATSU blood flow restriction

     
x. The use of anthropometry for assessing muscle size

     
x. Can KAATSU be used for an orthostatic stress in astronauts?: A case study

The application of an orthostatic stress such as lower body negative pressure (LBNP) during exercise has been proposed to minimize the effects of weightlessness on the cardiovascular system and subsequently to reduce the cardiovascular deconditioning. The KAATSU training is a novel method for strength training to induce muscle strength and hypertrophy. KAATSU induces venous pooling of blood in capacitance vessels by restricting venous blood flow. Therefore, to investigate whether KAATSU can be used as an orthostatic stress, we examined the effects of KAATSU on the hemodynamic, autonomic nervous and hormonal parameters in one subject. The several parameters were measured by impedance cardiography; heart rate (HR), mean blood pressure (mBP), stroke volume (SV), cardiac output (CO), total peripheral resistance (TPR), and heart rate variability (HRV). These data were obtained before (pre), during and after (post) pressurization (50 and 200 mmHg) on both thighs with KAATSU mini belts, and compared with those in standing. The serum concentration of noradrenaline (NA) and vasopressin (ADH), and plasma rennin activity (PRA) were also measured. The application of 200 mmHg KAATSU decreased SV, which was almost equal to the value in standing. HR and TPR increased in a similar manner as standing with slight change of mBP. High frequency (HFRR), a marker of parasympathetic nervous activity, decreased during both 200 mmHg KAATSU and standing, while LFRR/HFRR, a quantitative marker of sympathetic nervous activity, increased significantly. During KAATSU and standing, NA, PRA and ADH increased. These results indicate that the application of KAATSU on both thighs simulates systemic cardiovascular effects of orthostasis in one gravity (1G), and that KAATSU training appears to be a useful method for potential countermeasure like lower body negative pressure (LBNP) against orthostatic intolerance in space flight as well as strength training to induce muscle strength and hypertrophy.

x. Effects of a single bout of low intensity KAATSU resistance training on markers of bone turnover in young men

   
x. KAATSU resistance training decreased the sinus pause in a patient demonstrating sick sinus syndrome. A case report

The effectiveness of KAATSU resistance training (Kaatsu) has been established as a method not only to increase muscle size and power but also to benefit patients with orthopedic and cardiac diseases. The method is a low-intensity resistance exercise (20?30% of one repetition maximum, 1RM) with a restriction of the venous return using a specially designed pressurized cuff or belt at the proximal end of the upper or lower extremities. The increases of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) by Kaatsu resistance training are considered to play an important role in elucidating the mechanism of Kaatsu. In this case, the sinus pause of a patient with sick sinus syndrome (SSS) decreased to approximately 40% with Holter ECG monitoring after Kaatsu resistance training. The mechanism regarding such an improvement by Kaatsu is herein discussed. Therefore, an additional effect of Kaatsu is reported concerning the decreased sinus pause observed in a SSS patient.

x. Resistance exercise combined with KAATSU during simulated weightlessness

   
x. Effect of knee extension exercise with KAATSU on forehead cutaneous blood flow in healthy young and middle-aged women

Dynamic exercise induces changes in the redistribution of whole-body organ-tissue blood circulation, including cutaneous blood circulation. We hypothesized that limb exercise combined with the restriction of muscular blood flow (KAATSU) may influence cutaneous blood flow redistribution. To examine this hypothesis, forehead (supraorbital) cutaneous blood flow was compared in women performing exercises with and without KAATSU. Ten young and middle-aged female subjects in the supine position performed three sets of 15 repetitions of unloaded unilateral knee extension exercises (30-s rest between sets). Blood flow was calculated from blood velocity and red blood cell mass (blood flow = velocity * mass) determined by laser blood flowmetry. While exercise without KAATSU did not induce alterations in velocity and mass (hence, no alterations in blood flow) throughout the entire exercise series, exercise with KAATSU induced increases (P<0.05) in blood flow owing to increases in velocity. These increases were not eliminated during the rest periods between exercise sets. Heart rate (HR) increased (P<0.05) with the second and third sets of exercises with KAATSU compared with HR before exercise initiation, and was higher than the HR resulting from a corresponding set of exercises without KAATSU. There were no changes in blood lactate and hematocrit in both types of exercises. Norepinephrine increased (P<0.05) at the completion of the exercise sets. These results suggest that forehead cutaneous blood circulation was increased by unloaded KAATSU leg exercise.

x. The horse: An alternative model for KAATSU research

In order to produce significant muscle hypertrophy, a training intensity of greater than 65% of the 1-repetition maximum (1-RM) is generally believed to be required. However, this concept has been challenged recently by data from studies that have combined 20%-50% 1-RM with restriction of venous blood flow from the working muscle, referred to as KAATSU-training. These studies have demonstrated significant gains in muscle size and strength in as little as 2 weeks in humans. The KAATSU-training model may have utility in models other than humans; several recent papers have investigated the safety and potential utility of KAATSU-training in an equine model. The purpose of this brief review is to discuss the horse as a viable model of KAATSU-training and discuss the available data using this model thus far.

   
x. Blood pressure response to slow walking combined with KAATSU in the elderly

x. Effects of Whole-Body Low-Intensity Resistance Training With Slow Movement and Tonic Force Generation on Muscular Size and Strength in Young Men

x. Acute Hormonal Responses To Restriction Of Leg Muscle Blood Flow During Walking: 564 Board #155 2:00 PM - 3:30 PM

11 male college students performed walking (50 m/min for five 2 min bouts; 1 min rest between bouts) with and without KAATSU (the proximal end of their thigh compressed at 130% of resting systolic blood pressure throughout the walking session) on separate days. Venous blood samples were obtained prior to the start of exercise (Pre), and immediately (IP), 15- (15P) and 60-min (60P) after exercise.
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RESULTS

Serum GH concentration was elevated (P<0.01) from Pre [1.72 (0.83) ng/ml] to IP [12.4 (3.2) ng/ml] and 15P [13.1 (2.4) ng/ml] in the walking with KAATSU. Free testosterone was also elevated (P<0.05) from Pre [12.7 (1.2) pg/ml] to IP [16.0 (1.3) pg/ml] in the walking with KAATSU. Neither GH [Pre, 1.67 (0.97) ng/ml; IP, 1.39 (0.91), 15P, 1.26 (0.92)] nor free testosterone [Pre, 14.3 (1.3) pg/ml; IP, 14.1 (1.2)] increased during the walking without KAATSU. Cortisol concentration showed a gradual decrease (P<0.05) during the experiments in both walking with and without KAATSU.
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CONCLUSIONS

The results of the present investigation with young male students indicated that slow walking with KAATSU caused greater responses in serum GH and free testosterone compared to normal slow walking.

x. Muscle Oxygenation and Pulse Oxygen Saturation during Walking Combined with Restriction of Leg Muscle Blood Flow: 2708: Board #216 3:PM - 4:PM

x. Effects of Walk or Squat Training Combined with Restriction of Leg Muscle Blood Flow on Hip, Thigh and Calf Muscle Hypertrophy: 1773: Board # 146 3:00 PM - 4:00 PM

Low-intensity resistance squat or walk training combined with restriction of leg muscle blood flow (KAATSU) increases thigh muscle size and strength. However, it is unknown whether muscle hypertrophy occurs in training movement-related accessory muscles, such as hip and calf, following KAATSU squat or walk training.

PURPOSE: To investigate the effects of 2 types (walk or squat) of exercise training combined with KAATSU on hip, thigh and calf muscle size and strength.

METHODS: 33 healthy young men [mean (SD) age: 22.4 (3.5) yrs] were randomized into 4 training groups: treadmill walking (50m/min, 5 sets of 2-min bout with a 1 -min rest between bouts, twice per day, 6 days per week for 3 weeks) with or without KAATSU (KAATSU-walk, n=9 or Control-walk, n=8), and squat exercise (20% of 1-RM, 4 sets, twice per day, 6 days per week for 2 weeks) with or without KAATSU (KAATSU-squat, n=9 or Control-squat, n=7). A specially designed elastic belt (50 mm wide) was placed around the most proximal portion of each leg during training with KAATSU. The belt contained a pneumatic bag along its inner surface that was connected to an electronic air pressure control system that monitored the restriction pressure. Because the subjects adapted to the occlusion stimulus during the training, the restriction pressure of 160-230 mmHg was selected for occlusive stimulus. Skeletal muscle volume was measured using magnetic resonance imaging (MRI) 1.5 T-scanners with spin-echo sequence. Contiguous transverse MRI images (about 100 slices) with a slice thickness of 1 -cm were obtained from the L4/L5 to the ankle joint before and after training. Quadriceps, gluteus maximus, and triceps surea muscle volume were calculated from the summation of digitized cross-sectional area. Maximum isometric knee extension strength was measured before and after training.

RESULTS: There were no changes (P >0.05) in muscle volume and maximum isometric strength for Control-walk and Control-squat groups. Maximum isometric knee extension strength increased (P <0.05) 11.1% for KAATSU-squat and 10.4% for KAATSU-walk. Quadriceps muscle volume increased (P <0.01) 4.1% and 7.5%, respectively, in KAATSU-walk and KAATSU-squat groups. Gluteus maximus muscle volume increased 8.4% (P <0.01) in KAATSU-squat but did not increase in KAATSU-walk (-0.6%). On the other hand, triceps surea muscle volume increased (P <0.05) 5.7% in KAATSU-walk but did not increase (P >0.05) in KAATSU-squat (1.2%).

CONCLUSION: Skeletal muscle hypertrophy occurred not only thigh muscle, but also in training movement-related accessory muscles following low-intensity KAATSU training.

x. Effects of Vascular Restriction on Muscular Function during Intermittent Submaximal Isometric Exercise: 2246: Board #159 June 1 8:00 AM - 9:30 AM

x. Proposal of alternative mechanism responsible for the function of high-speed swimsuits

Since many top swimmers wearing Speedo LZR Racer swimsuits have broken world records, it is considered that the corset-like grip of suit supports the swimmers to maintain flexibility of movement and reducing water resistance. We propose an alternative mechanism to explain this phenomenon. The suits are so tight that the blood circulation of swimmers is suppressed. This effect accelerates the anaerobic glycolysis system but rather suppresses the aerobic mitochondrial respiration system. Because of the prompt production of ATP in the glycolysis system, the swimmers, especially in short distance competitions, obtain instantaneous force in white fibers of the skeletal muscles.

x. Muscle Hypertrophy following Multi-joint Low Intensity Resistance Training with Single-joint Blood Flow Restriction: 1615: Board #162 May 28 3:30 PM - 5:00 PM

Low-intensity, single-joint resistance exercise training combined with restricted muscle blood flow results in significant increases in muscle size and strength. What remains poorly understood is whether muscle enlargement and strength changes occur in lowintensity multi-joint exercise where only a portion of the active musculature is exposed to restricted blood flow.

PURPOSE: To determine the impact of low-intensity multi-joint resistance exercise on strength and the hypertrophic response of muscles proximal (non-restricted) and distal (restricted) to blood flow restriction (KAATSU).

METHODS: Bench press training (30% of 1-RM, 4 sets, 30 sec rest between sets) was performed with (BP-K; n=5) and without (BP-C; n=5) KAATSU blood flow restriction; the proximal end of their upper arm compressed at 80-120% of resting systolic blood pressure throughout the exercise session. Training was conducted twice per day, six days per week for 2 weeks. Each morning prior to the training session, triceps brachii and pectoralis major muscle thickness (MTH) were measured by B-mode ultrasound (Aloka SSD-500, Tokyo). Serum creatine phosphokinase, myoglobin, growth hormone, testosterone, insulin-like growth factor (IGF)-1 and IGF-BP3 concentrations were measured prior to and 2-days following the last training session.

RESULTS: There were no changes in anabolic hormones or serum markers for muscle damage in either group. 2-weeks of training led to a significant increase (P<0.05) in 1-RM bench press in BP-K (+6%), but not in BP-C (-2%). Triceps and pectoralis major MTH increased 8% (pre, 36.1 mm; post 38.9 mm, P<0.01) and 16% (pre, 23.7 mm; post, 27.6 mm, P<0.01), respectively, in BP-K, but not in BP-C (-1% and 2%, respectively).

CONCLUSIONS: Low-intensity Kaatsu training involving a multi-joint exercise leads to a significant increase in muscular strength and hypertrophy in skeletal muscles proximal and distal to the blood-flow restriction; suggesting that the mechanism of KAATSU training affects adaptation upstream and downstream of the pressure cuff and blood flow restriction.

x. Neuromuscular Fatigue during Low-Intensity Dynamic Exercise in Combination with Externally Applied Vascular Restriction: 1768: Board #121 May 29 9:00 AM - 10:30 AM

   
x. Skeletal muscle size and strength are increased following walk training with restricted leg muscle blood flow: implications for training duration and frequency

The purpose of this study was to investigate once-daily walk training with restricted leg blood flow (KAATSU) on thigh muscle size and strength. Twelve young men performed walk training: KAATSU-walk training (n=6) and control (no KAATSU-walk; n=6). Training was conducted once daily, 6 days per week, for 3 weeks. Treadmill walking (50 m/min) was performed for 5 sets of 2-min bouts interspersed with 1-min rest periods. The KAATSU-walk group wore pressure cuff belts (5 cm wide) on both legs during training, with incremental increases in external compression starting at 160 mmHg and ending at 230 mmHg. Thigh muscle volume and isometric and 1-repetition maximal (1-RM) strength were measured before and after training. In the KAATSU-walk group, quadriceps and hamstrings muscle volume increased 1.7 and 2.4% (both P<0.05), respectively, following training. One-RM leg press and leg curl increased 7.3 and 8.6% (both P<0.05), respectively, following KAATSU-walk training. Also, isometric knee extension strength (4.4%; P<0.01), but not knee flexion strength (1.7%), increased following KAATSU-walk training. There were no changes in muscle volume or strength in the control-walk group. These results confirm previous work showing that the combination of slow walk training and leg muscle blood flow restriction induces muscle hypertrophy and strength gains. However, the magnitude of change in muscle mass and strength following once-daily KAATSU-walk training was approximately one-half that reported for twice-daily KAATSU-walk training over a 3-week period. These results in combination with previous observations lead to the conclusion that the impact of KAATSU-walk training on muscle size and strength is related to an ability to accomplish a high number of training bouts within a compressed training duration. Second, frequency-dependent muscle enlargement appears to be associated with KAATSU-walk training.

x. Muscle Tissue Oxygenation and Force Production during Low-intensity Resistance Exercise with Blood Flow Restriction: 1769: Board #122 May 29 9:00 AM - 10:30 AM

We have recently demonstrated that an acute bout of low-intensity resistance exercise combined with blood flow restriction (Kaatsu exercise) stimulates both muscle protein synthesis and translation initiation. Recently, myocardial ischemia-reperfusion has also been shown to activate the signaling pathway of translation initiation.

PURPOSE: To investigate the changes in muscle tissue oxygenation during Kaatsu exercise to assess the level of ischemia-reperfusion condition in skeletal muscle.

METHODS: Six subjects performed three separate experiments randomly; Control (CON), Kaatsu (KAT, blow restriction via pressure cuff), or High-intensity (HI) exercise group. CON and KAT performed a bout of unilateral knee extension exercise at 20% of 1-repetition maximum (1-RM) strength, while HI group exercised at 70% 1-RM. Vastus lateralis and rectus femoris muscle tissue oxygenation (HbO2) was assessed using near-infrared spectroscopy (NIRS), and isometric muscle strength was assessed immediately before and after the exercise bout.

RESULTS: In the KAT, resting HbO2 was reduced significantly (rest, 61.7%; cuff, 54.5%; p<0.05) in response to blood flow restriction. During exercise, HbO2 decreased further in KAT and reached the same level of tissue oxygenation as HI (KAT, 45.6%; HI, 44.8%; p<0.05 vs. rest for both groups) whereas HbO2 did not change in CON. During the recovery period, HbO2 was restored to the resting level both in CON and HI group (63.9 and 69.1% for CON and HI, respectively), whereas it was still significantly depressed in KAT group (51.4%, p<0.05). Muscular strength was significantly reduced after the bout of exercise in KAT and HI (-45 and -25% for KAT and HI, respectively; p<0.05), whereas no change in strength was observed in CON (-1.8%).

CONCLUSION: Although a decreased tissue oxygenation during exercise and recovery period may contribute to muscle fatigue, sustained ischemic condition during recovery period in KAT suggests a non-significant ischemia-reperfusion during low intensity resistance exercise with blood flow restriction.

x. Effects of short-term, low-intensity resistance training with vascular restriction on arterial compliance in untrained young men

Previous studies have shown that low-intensity resistance training with restricted blood flow, known as KAATSU training, increases muscle strength and size. Its effects on blood vessel function, however, have not been examined. We compared the effects of a short-term KAATSU resistance training protocol and traditional high-intensity resistance training on muscle strength and blood vessel function in young, untrained men. Male volunteers were randomly assigned to a KAATSU resistance training group (KR, n=10), a traditional resistance training group (RT, n=10), or a KAATSU-only group (K, n=10). Both KR and RT groups trained 3 times per week for 3 weeks doing leg press (LP), knee flexion (KF), and knee extension (KE) isotonic resistance exercises. Training sessions consisted of 5-10 min of warm-up, followed by 2 sets of 10 repetitions at 80% of 1 repetition maximum (1-RM) for the RT group, while the KR group performed the resistance exercises with vascular restriction at a load of 20% of 1-RM. The K group had only the vascular restriction treatment for 3 weeks. Muscle strength (1-RM) and arterial compliance (pulse contour analysis) were assessed at baseline and after training. Both the KR and RT groups did not show changes in arterial compliance of the large or small arteries (P>0.05) after training. There were significant time effects (P<0.05 pre- vs. posttraining); however, resistance training generally resulted in greater relative improvements in strength. Arterial compliance of the large and small arteries was not affected by the either the KAATSU or traditional high-intensity resistance training interventions.

   
x. Circuit training without external load induces hypertrophy in lower-limb muscles when combined with moderate venous occlusion

     
x. Fatigue Characteristics during Maximal Concentric Leg Extension Exercise with Blood Flow Restriction

x. The Effects Of Differing Thigh Composition On Tissue Oxygenation Of The Quadriceps Following Vascular Restriction: 1822: Board #172 May 27 2:00 PM - 3:30 PM

   
x. Increased muscle volume and strength following six days of low-intensity resistance training with restricted muscle blood flow

Traditional high-intensity resistance training performed 2-3 times per week induces muscle hypertrophy, at least, in 5 weeks (i.e. 10-15 training sessions). To examine the effect of a higher training frequency (12 sessions in 6 days), healthy young men performed low-intensity resistance training with (n=8, LIT-BFR) and without (n=8, LIT-CON) leg blood flow restriction with cuff inflation (BFR) twice per day for 6 days. Training involved 4 sets of knee extension exercise (75 total contractions) at 20% 1-RM. Significant muscle hypertrophy was observed only in the LIT-BFR group as estimated muscle-bone cross-sectional area (CSA) (2.4%), MRI-measured mid-thigh quadriceps muscle CSA (3.5%) and quadriceps muscle volume (3.0%) increased. The resulting hypertrophic potential (% change in muscle size divided by number of training sessions; ?0.3% per session) is similar to previously reported traditional high-intensity training (0.1 to 0.5% per session). Improved 1-RM knee extension strength (6.7%) following LIT-BFR training was accounted for by increased muscle mass as relative strength (1-RM/CSA) did not change. There was no apparent muscle damage associated with the exercise training as blood levels of creatine kinase, myoglobin, and interleukin-6 remained unchanged throughout the training period in both training groups. A single bout of training exercise with and without BFR produced no signs of blood clotting as plasma thrombin-antithrombin complex, prothrombin fragment 1,2 and D-dimer were unchanged. In conclusion, changes in muscle mass and strength following 6-day (12 sessions) of low-intensity resistance training requires BFR to produce responses comparable to the effect of several weeks of high-intensity resistance training.

x. Effects of Exercise Load and Blood-Flow Restriction on Skeletal Muscle Function

x. Effects of Vascular Occlusion on Muscular Endurance in Dynamic Knee Extension Exercise At Different Submaximal Loads

Strength training with low load under conditions of vascular occlusion has been proposed as an alternative to heavy-resistance exercise in the rehabilitation setting, when large forces acting upon the musculoskeletal system are unwanted. Little is known, however, about the relative intensity at which occlusion of blood flow significantly reduces dynamic muscular endurance and, hence, when it may increase the training effect. The purpose of this study was to investigate endurance during dynamic knee extension at different loads with and without cuff occlusion. Sixteen subjects (20-45 years of age) with strength-training experience were recruited. At 4 test sessions, the subjects performed unilateral knee extensions to failure with and without a pressure cuff around the thigh at 20, 30, 40, and 50% of their 1 repetition maximum (1RM). The pressure cuff was inflated to 200 mm Hg during exercise with occlusion. Significant differences in the number of repetitions performed were found between occluded and nonoccluded conditions for loads of 20, 30, and 40% of 1RM (p < 0.01) but not for the 50% load (p = 0.465). Thus, the application of a pressure cuff around the thigh appears to reduce dynamic knee extension endurance more at a low load than at a moderate load. These results may have implications regarding when it could be useful to apply a tourniquet in order to increase the rate of fatigue and perhaps also the resulting training effect. However, the short- and long-term safety of training under ischemic conditions needs to be addressed in both healthy and less healthy populations. Furthermore, the high acute pain ratings and the delayed-onset muscle soreness associated with this type of training may limit its potential use to highly motivated individuals.

x. The effects of low-intensity resistance training with vascular restriction on leg muscle strength in older men

x. Neuromuscular fatigue following low-intensity dynamic exercise with externally applied vascular restriction

This study investigated neuromuscular fatigue following low-intensity resistance exercise with vascular restriction (VR) and without vascular restriction (control, CON). Fourteen males participated in two experimental trials (VR and CON) each separated by 48 h. Each participant performed two isometric maximum voluntary contractions (MVCs) before and after five sets of 20 dynamic constant external resistance leg extension exercises (DCER-EX) at 20% of one-repetition maximum (1-RM). The participants were asked to lift (1.5 s) and lower (1.5 s) the load at a constant velocity. Surface electromyography (EMG) was recorded from the vastus lateralis during MVC and DCER-EX. Twitch interpolation was used to assess the percent of maximal voluntary activation (%VA) during the MVC. During performing five sets of 20 DCER-EX, the increases (p < 0.05) in EMG amplitude and decreases (p < 0.05) in EMG mean power frequency were similar for both VR and CON. However, there were significant differences between VR and CON for MVC force, %VA, and potentiated twitch force and significant interactions for EMG amplitude. VR decreased MVC force, %VA, potentiated twitch force, and EMG amplitude more than CON. Our findings suggest that the VR-induced fatigue may have been due to a combination of peripheral (decreases in potentiated twitch) and central (decreases in %VA and EMG amplitude) fatigue.

x. Cross-Transfer Effects of Resistance Training with Blood Flow Restriction

Purpose: This study investigated whether muscle hypertrophy-promoting effects are cross-transferred in resistance training with blood flow restriction, which has been shown to evoke strong endocrine activation.

Methods: Fifteen untrained men were randomly assigned into the occlusive training group (OCC, N = Cool and the normal training group (NOR, N = 7). Both groups performed the same unilateral arm exercise (arm curl) at 50% of one-repetition maximum (1RM) without occlusion (three sets, 10 repetitions). Either the dominant or nondominant arm was randomly chosen to be trained (OCC-T, NOR-T) or to serve as a control (OCC-C, NOR-C). After the arm exercise, OCC performed leg exercise with blood flow restriction (30% of 1RM, three sets, 15-30 repetitions), whereas NOR performed the same leg exercise without occlusion. The training session was performed twice a week for 10 wk. In a separate set of experiments, acute changes in blood hormone concentrations were measured after the same leg exercises with (N = 5) and without (N = 5) occlusion.

Results: Cross-sectional area (CSA) and isometric torque of elbow flexor muscles increased significantly in OCC-T, whereas no significant changes were observed in OCC-C, NOR-T, and NOR-C. CSA and isometric torque of thigh muscles increased significantly in OCC, whereas no significant changes were observed in NOR. Noradrenaline concentration showed a significantly larger increase after leg exercise with occlusion than after exercises without occlusion, though growth hormone and testosterone concentrations did not show significant differences between these two types of exercises.

Conclusion: The results indicate that low-intensity resistance training increases muscular size and strength when combined with resistance exercise with blood flow restriction for other muscle groups. It was suggested that any circulating factor(s) was involved in this remote effect of exercise on muscular size.

x. Effect of resistance exercise training combined with relatively low vascular occlusion

x. Venous blood gas and metabolite response to low-intensity muscle contractions with external limb compression

x. The Use of Occlusion Training to Produce Muscle Hypertrophy

LOW-INTENSITY OCCLUSION (50-100 MM HG) TRAINING PROVIDES A UNIQUE BENEFICIAL TRAINING MODE FOR PROMOTING MUSCLE HYPERTROPHY. TRAINING AT INTENSITIES AS LOW AS 20% 1 REPETITION MAXIMUM WITH MODERATE VASCULAR OCCLUSION RESULTS IN MUSCLE HYPERTROPHY IN AS LITTLE AS 3 WEEKS. A TYPICAL EXERCISE PRESCRIPTION CALLS FOR 3 TO 5 SETS TO VOLITIONAL FATIGUE WITH SHORT REST PERIODS. THE METABOLIC BUILDUP CAUSES POSITIVE PHYSIOLOGIC REACTIONS, SPECIFICALLY A RISE IN GROWTH HORMONE THAT IS HIGHER THAN LEVELS FOUND WITH HIGHER INTENSITIES. OCCLUSION TRAINING IS APPLICABLE FOR THOSE WHO ARE UNABLE TO SUSTAIN HIGH LOADS DUE TO JOINT PAIN, POSTOPERATIVE PATIENTS, CARDIAC REHABILITATION, ATHLETES WHO ARE UNLOADING, AND ASTRONAUTS.

x. Effects of Handgrip Training With Venous Restriction on Brachial Artery Vasodilation

Previous studies have shown that resistance training with restricted venous blood flow (Kaatsu) results in significant strength gains and muscle hypertrophy. However, few studies have examined the concurrent vascular responses following restrictive venous blood flow training protocols.

Purpose: To examine the effects of 4 weeks of handgrip exercise training, with and without venous restriction, on handgrip strength and brachial artery flow mediated dilation (BAFMD).

Methods: Twelve participants (age=22+/-1yr; male = 5, female = 7), completed 4 weeks of bilateral handgrip exercise training (Duration: 20 min; Intensity: 60% of the MVC; Cadence: 15 grips*min-:1; Frequency: 3 sessions*week-1). During each session venous blood flow was restricted in one arm (Experimental arm = EXP) using a pneumatic cuff placed 4 cm proximal to the antecubital fossa, and inflated to 80 mmHg for the duration of each exercise session. The EXP and control (CON) arm were randomly selected. Handgrip strength was measured using a hydraulic hand dynamometer. Brachial diameters and blood velocity profiles were assessed, using Doppler ultrasonography, before and after 5 min of forearm occlusion (200 mmHg), prior to and at the end of 4 weeks exercise.

Results: Following exercise training, handgrip strength increased 8.32% (p=0.05) in the CON arm and 16.17% (p=0.05) in the EXP arm. BAFMD increased 24.19% (p=0.0001) in the CON arm, and decreased 30.36% (p=0.0001) in the EXP arm.

Conclusion: The data indicate handgrip training combined with venous restriction results in superior strength gains, but reduced BAFMD compared to the non-restricted arm.

x. Acute vascular occlusion in horses: effects on skeletal muscle size and blood flow

x. Increase in calf post-occlusive blood flow and strength following short-term resistance exercise training with blood flow restriction in young women

   
x. Changes of Compound Muscle Action Potential after Low-Intensity Exercise with Transient Restriction of Blood Flow: a Randomized, Placebo-Controlled Trial

Abstract.  [Purpose] The purpose of this study was to investigate the mechanism of muscular force improvement after low-intensity exercise with transient restriction of blood flow using compound muscle action potential (CMAP) analysis. [Subjects] Thirty healthy subjects in their 20s (mean age=21.73 years) were randomly assigned to an experimental group (EG) and a placebo control group (PG); each group had 15 subjects. [Methods] CMAP was analyzed by measuring terminal latency and amplitude using a motor nerve conduction velocity test. For Baseline 1, supramaximal electrical stimulation was applied to the median nerves of the EG and PG to obtain CMAP at the abductor pollicis brevis. For Baseline 2, the intensity of the electrical stimulation was decreased to a level at which the CMAP amplitude was about a third (1/3) of the CMAP amplitude obtained by supramaximal electrical stimulation. In the first test, CMAP was obtained under the same conditions as Baseline 2 after low-intensity thumb abduction exercises were performed at subjects' own pace for one minute. EG had blood flow restricted by a sphygmomanometer cuff, but PG did not. In the retest, CMAP was obtained under the same conditions as Baseline 2, one minute after the removal of the sphygmomanometer cuff immediately after the first test. [Results] PG did not show significant changes in CMAP, whereas EG showed a significant increase in CMAP amplitude, signifying that more muscle fibers were recruited. [Conclusion] This study found that low-intensity exercise with transient restriction of blood flow recruited more muscle fibers than low-intensity exercise without transient restriction of blood flow.

x. Growth hormone and muscle function responses to skeletal muscle ischemia

x. Changes In Tissue Oxygenation And Muscular Function In Response To Vascular Restriction: 1826: Board #176 May 27 2:00 PM - 3:30 PM

x. Venous Blood Changes with Low-Intensity Muscle Contractions and Blood Flow Restriction: 1989: Board #153 May 29 2:00 PM - 3:30 PM

Work output during repetitive low-intensity muscle contractions is presumably maintained by increased motor unit recruitment (increased EMG activity) during restricted blood flow. Interestingly, the increased muscle activation is associated with an increased oxygen uptake (Vo2); an unexpected finding given the same external work and reduced muscle blood flow.

PURPOSE: To investigate changes in venous blood metabolites and gases during repetitive muscle contractions with restricted blood flow.

METHODS: Six male volunteers performed 3 trials (separated by 1-week) of unilateral elbow flexion muscle contractions (20% of 1-RM; 30 repetitive contractions then 3 sets of 15 contractions, 30 sec rest between sets). Contractions were performed with unrestricted blood flow (C) or two levels of blood flow restriction using a KAATSU belt; a specially designed elastic cuff placed at the most proximal position of the upper arm and inflated to either 100 (K100) or 160 (K160) mmHg to restrict blood flow. Venous blood was collected prior to contractions and following the 30 repetitive contractions and the last set of 15 contractions; (an indwelling catheter inserted in the brachial vein below the cuff). Venous blood was analyzed using a blood gas analyzer (Instrumentation Laboratory, Japan).

RESULTS: Oxygen saturation decreased with contractions in all trials (P<0.05) with K160 (33% and 34%, respectively) being greater than K100 (41% and 42%, respectively) and both greater than C (67% and 56%, respectively). Changes in venous blood pH and PCO2 were greater in K160 than K100 and C. Venous PO2 decreased similarly in K160 and K100, significantly less than C. Hematocrit and [glucose] were similar in all trials while [lactate] was greater (P<0.05) in K160 (4.4 and 5.6 mmol/L, respectively) than K100 (3.2 and 3.6 mmol/L, respectively) and C (2.5 and 2.9 mmol/L, respectively).

CONCLUSION: The significant reduction in oxygen saturation supports the previously observed increase in VO2 during blood flow restriction. The basis for the greater lactate concentration is unknown; either increased production or reduced removal. These data appear to support the conclusion that energy supply is paradoxically increased during low-intensity muscle contractions with restricted blood flow, likely associated with increased muscle activation.

     
x. What phenomena do occur in blood flow-restricted muscle?

Oxygen is an essential molecule for all cellular activities including growth. Either excessive or deficient oxygen supply to cells induces the various responses of the cells. In the field of pathophysiology, effects of blood flow restriction on various organs have been studied for the past ?130 years. Subsequently, the roles of oxygen at subcellular level have been studied in vitro. Although a number of studies show that a low-intensity exercise (20?50% of one repetition maximum) with a moderate tourniquet restriction of blood flow results in increases in muscular strength and size, the mechanisms for this muscular adaptation remain unclear. In particular, it is uncertain whether the low-intensity exercise with blood flow restriction using a tourniquet causes the hypoxia or hyperoxia in the muscle, and then what signals leading to muscular hypertrophy are activated inside and/ or outside the cells. Also, it is not well understood what side effects occur in addition to conferring the benefits of strength gains. The review summarizes recent studies on the muscular adaptations to oxygen environment and discusses the mechanisms that may be involved in the resistance exercise with restricted blood flow.

   
x. Time under Tension and Blood Lactate Response during Four Different Resistance Training Methods

x. Enhancement of cardiac autonomic nervous system activity by blood flow restriction in the human leg

The purpose of this study is to develop a unique method to enhance autonomic nervous system (ANS) activity by means of experimental leg occlusion. The effects of blood flow restriction on the activities of the ANS during rest were investigated using a power spectral analysis of heart rate variability. Two patterns of occlusion were randomly assigned to healthy subjects: pattern A, 10 min of 1.4 times of systolic blood pressure; pattern B, 5 min of mean blood pressure followed by 5 min of 1.4 times of systolic blood pressure. Electrocardiogram, blood pressure and cardiac output were continuously monitored during rest and occlusion. During occlusion, cardiac output and stroke volume showed significant decreases, due to modulation of autonomic nervous activity. After releasing from occlusion without blood pooling (A), the high frequency component of R-R interval variability representing vagal activity showed a significant increase (P<0.05). However, soon after releasing, the ECG QTc interval temporally prolonged (P<0.05) and recovered gradually. Further investigation is recommended to determine blood flow occlusion safety on the cardiac depolarization-repolarization process. In conclusion, the results suggest that blood flow restriction has potential to be a useful method to stimulate the activity of autonomic nervous system, and especially to enhance parasympathetic nervous system activity.

x. Plasticity of the Muscle Proteome to Exercise at Altitude

x. Effects of low-intensity resistance exercise with slow movement and tonic force generation on muscular function in young men

We investigated the acute and long-term effects of low-intensity resistance exercise (knee extension) with slow movement and tonic force generation on muscular size and strength. This type of exercise was expected to enhance the intramuscular hypoxic environment that might be a factor for muscular hypertrophy. Twenty-four healthy young men without experience of regular exercise training were assigned into three groups (n = 8 for each) and performed the following resistance exercise regimens: low-intensity [~50% of one-repetition maximum (1RM)] with slow movement and tonic force generation (3 s for eccentric and concentric actions, 1-s pause, and no relaxing phase; LST); high-intensity (~80% 1RM) with normal speed (1 s for concentric and eccentric actions, 1 s for relaxing; HN); low-intensity with normal speed (same intensity as for LST and same speed as for HN; LN). In LST and HN, the mean repetition maximum was 8RM. In LN, both intensity and amount of work were matched with those for LST. Each exercise session consisting of three sets was performed three times a week for 12 wk. In LST and HN, exercise training caused significant (P < 0.05) increases in cross-sectional area determined with MRI and isometric strength (maximal voluntary contraction) of the knee extensors, whereas no significant changes were seen in LN. Electromyographic and near-infrared spectroscopic analyses showed that one bout of LST causes sustained muscular activity and the largest muscle deoxygenation among the three types of exercise. The results suggest that intramuscular oxygen environment is important for exercise-induced muscular hypertrophy.

x. Increase in maximal oxygen uptake following 2-week walk training with blood flow occlusion in athletes

x. Delayed-onset muscle soreness induced by low-load blood flow-restricted exercise

x. Prevention of Disuse Muscular Weakness by Restriction of Blood Flow

Purpose: The aim of the present study was to compare the effects of periodic restriction of blood flow to lower extremities with those of isometric exercise on disuse muscular atrophy and weakness induced by immobilization and unloading.

Methods: The left ankle of each of 15 healthy males was immobilized for 2 wk using cast, and subjects were instructed to walk using crutches with non-weight bearing during this period. Subjects were divided into three groups: a restriction of blood flow (RBF) group (application of external compressive force of 200 mm Hg for 5 min followed by 3 min of rest, repeated five times in a single session, two sessions per day for 14 d); an isometric training (IMT) group (20 "exercises" of 5-s isometric contraction of the knee extensor, flexor, and ankle plantar flexor muscles followed by rest, twice a day, daily for 2 wk); and a control (CON) group (no intervention). We measured changes in muscle strength, thigh/leg circumferences, and serum growth hormone levels.

Results: Immobilization/unloading resulted in significant decreases in muscle strength of knee extensor and flexor muscles (P < 0.01 and < 0.05, respectively) and thigh and leg circumferences (P < 0.05, each) in the CON group, and significant decreases in muscle strength of the knee flexor muscles, ankle plantar flexor muscles, and leg circumference (P < 0.05) in the IMT group. RBF protected against these changes in muscle strength and thigh/leg circumference (P < 0.01 and < 0.05, respectively). No changes in serum growth hormone levels were noted.

Conclusion: Our results indicate that repetitive restriction of blood flow to the lower extremity prevents disuse muscular weakness.

x. Comparison of hormone responses following light resistance exercise with partial vascular occlusion and moderately difficult resistance exercise without occlusion