REVIEW ARTICLE Overview of neuromuscular adaptations of to KAATSU Training

M. Karabulut, T. Abe, Y. Sato, M. Bemben

Int. J. KAATSU Training Res. 2007; 3: 1-9

Skeletal muscle adapts to a progressive overload, but the response can vary between different modes and intensities of . Generally, a minimal threshold intensity of 65% of the one repetition maximum (1-RM) is needed to elicit ; however, recent studies have challenged this Correspondence to: hypothesis and have provided evidence that low-intensity training (LIT) combined with vascular M. Karabulut, Department of restriction (KAATSU) may also elicit increases in muscle size and strength. The physiological aspects Health and Exercise Science, of applying vascular restriction during exercise are not fully understood and may be explained by University of Oklahoma, 1401 Asp Avenue, Norman, OK, several factors. Examining the results of previous studies may help elucidate the factors responsible for USA the adaptations associated with vascular restriction in humans. Therefore, the objectives of this review E-mail: [email protected] 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 See end of article for author’s affiliations adaptations, and suggested areas for future research. Key words: blood restriction, skeletal muscle, hypertrophy, KAATSU.

INTRODUCTION 2004; McCall et al., 1999]. Although the precise Skeletal muscle can adapt positively when the mechanisms underlying these adaptations remain appropriate training principles are followed. Central unclear, reducing the relative intensity of resistance to the concept of physiological adaptation are the training to 20% 1-RM and including vascular training principles dealing with overload, progression, restriction would have obvious advantages for and adaptation. It is well established that in order for individuals who may exhibit limited strength or physiological adaptation to occur, the exercise health-related risks with higher resistance training intensity must be sufficient to elicit the desired loads, such as older adults and diseased or injured training response, i.e., muscle hypertrophy, muscle patients. In addition to the relative low intensity power, muscular endurance, etc. Intensity of the (20% 1-RM) utilized with KAATSU (even though the exercise and training volume can be manipulated in absolute intensity may be as high or higher than several ways, for example, increasing the load being traditional training loads), other important aspects lifted or by increasing the frequency of training (times such as shorter training periods (duration) and lower per week) or the duration of a single bout of exercise. volumes of work (load x sets x reps) are needed to Often times, positive adaptations can take several induce muscle hypertrophy and improve strength weeks (as seen with skeletal muscle changes) or even when compared to traditional resistance training several months (as seen with bone changes) before principles. Generally, training volumes utilizing improvements can be noted. moderate to higher number of repetitions per set (6 The recent development of exercise training at to 12) at 67-85% 1-RM have been associated with greatly reduced intensities when combined with muscle hypertrophy [Baechle and Earle, 2000]; blood flow restriction (KAATSU) has challenged however, KAATSU training requires much lower many of the widely accepted principles of exercise exercise volumes for similar or even a greater training (Sato, 2005). A number of studies have hypertrophic response of skeletal muscle. Since demonstrated that low-intensity resistance exercise increases in skeletal muscle size in response to (i.e., 20% 1-RM) combined with vascular restriction KAATSU training is relatively fast (even after one (KAATSU) can elicit increases in muscle size [Abe et week of KAATSU training) and can be achieved with al., 2006; Beekley et al., 2005; Takarada et al., 2002; low training volumes, this may be useful from a Takarada et al., 2000a] and strength [Shinohara et al., clinical standpoint for decreasing rehabilitation time 1998; Takarada et al., 2002] to a similar or even following injury. greater extent then traditional resistance training A review of the available evidence on training in utilizing intensities greater than the recommended combination with vascular restriction may help 65% 1-RM threshold [Goto et al., 2005; Goto et al., elucidate the physiological mechanisms responsible 2 Overview of Neuromuscular Adaptations of Skeletal Muscle to KAATSU Training

for skeletal muscle adaptation. The following paper is (summarized in Table 1) indicate that the intensity a brief summary of the recent history of skeletal and volume of training do not have to be high when muscle adaptation to lower intensity exercise when compared to traditional resistance training programs accompanied by vascular occlusion, which has its’ in order to elicit skeletal muscle hypertrophy. modest beginning in the late 1990’s [Shinohara et al., Researchers have reported statistically significant 1998; Yoshida and Watari, 1997] but has recently increases in muscle size in mid-thigh muscles of 8.5% become an area of increased interest for many in a KAATSU group compared to a group performing researchers. Detailed information about each of the the same protocol without blood flow restriction (no- studies examined in this review such as the KAATSU) [Abe et al., 2005b]. KAATSU and no- performed, if control groups were included, subject KAATSU groups also experienced changes in muscle information (gender, training frequency, etc.), and volumes for the quadriceps (7.7% and 1.4%, the pressures used to induce blood flow restriction are respectively) biceps femoris (10.1% and 1.9%, provided in Tables 1 and 2. This paper will present respectively) and gluteus maximus (9.1% and - both KAATSU training responses and acute findings 0.6%, respectively) after two-weeks of twice daily related to vascular restriction on skeletal muscle low intensity (20% 1-RM) resistance training; physiology in humans. however, only the changes with the KAATSU protocol were statistically significant following TRAINING RESPONSES training and changes in muscle size with KAATSU 1. Hypertrophy were similar to those utilizing traditional high- Duration and intensity of training intensity resistance training programs for 3 months Muscular hypertrophy is an adaptation to [Goto et al., 2005; McCall et al., 1999]. Additionally, increasing work loads that exceeds the capacity of the one week of twice-daily KAATSU training consisting muscle fiber, resulting in an increase in muscle mass of knee extension exercises at 20% of 1-RM resulted and cross-sectional area [Russell et al., 2000]. in a 3% increase in the quadriceps muscle CSA [Abe Traditional resistance training programs use high et al., 2005a], whereas completion of an 8-week intensity (≥ 65% 1-RM) exercises to elicit muscle training program that included five sets of knee hypertrophy. One study reported that the cross- extension exercises at an intensity of 20% 1-RM with sectional area (CSA) of the biceps brachii muscle KAATSU resulted in a 10.3% increase in knee increased by ~11% following a training protocol extension CSA, but no significant changes in muscle consisting of three sets of 10 repetition maximum CSA were determined when exercising at the same (~75% 1-RM) for 8 exercises during a 12 week intensity without blood flow restriction [Takarada et period (33 sessions) [McCall et al., 1999]. Others al., 2004]. Finally, Yasuda et al (2005) observed a have investigated the effects of combinations of 7.8% and a 1.8% increase in quadriceps muscle CSA different intensity resistance exercises on muscular in KAATSU and no-KAATSU groups, respectively, adaptations [Goto et al., 2004]. Subjects performed after a 2-week training (at 20% 1-RM) program. Type nine sets of exercises at varied intensities (from 40 to I and Type II muscle fiber CSA increased 5.9% and 80% 1-RM), during a designed hypertrophy phase 27.6% following KAATSU training, whereas changes (6-week). Following this 6-week hypertrophy phase, in Type I and Type II fiber CSA were -2.1% and 0.5% subjects were then assigned to either a hypertrophy / after no-KAATSU training, respectively. The findings combination (HC) or a hypertrophy / strength (HS) suggest that skeletal muscle hypertrophic responses group and performed leg press and knee extension may not only be due to changes in water balance exercises for an additional four weeks (strength created by blood flow restriction, but due to increased phase). The HS group performed 5 sets of leg protein synthesis. exercises at 3-5 RM (~90% 1-RM), whereas the HC It appears as though when KAATSU is used in group performed the same protocol as the HS group combination with resistance training (20% 1-RM) but included an additional set of low-intensity and that the adaptation period is greatly reduced (one to high-repetition exercise at 25-35 RM (~50% 1-RM) two weeks) compared to the time required to during the strength phase. Both groups experienced demonstrate significant changes from traditional similar changes in muscle CSA (~4%) after resistance training programs (80% 1-RM and 8 to 16 completion of the hypertrophy phase; however, only weeks) and that the relative intensity of the training the HC training program resulted in a further increase program is also lower (20% 1-RM versus 80% 1- in CSA (~2%) compared to HS training protocol. RM). These studies suggest that the intensity and volume of traditional training programs are important factors Modes of training and should always be considered in order to induce Generally, the application of external pressures to hypertrophic responses. produce vascular restriction, have been used in On the other hand, recent KAATSU studies combination with resistance training, but the M. Karabulut, T. Abe, Y. Sato, et al. 3

Table 1. Training Studies on the Effects of Vascular Restriction on Skeletal Muscle Physiology Author Group Duration N Gender Freq Set x Rep Intensity Change in Change in Change in EMG, Comments of Study (d/wk) CSA Strength MMG, motor unit (Week) Increase (↑ ) Increase (↑ ) activation, PAP Decrease (↓ ) Decrease (↓ ) Increase (↑ ) Decrease (↓ )

Abe et al. E 1 wk 1 M 7 d 30 reps + 3 20% 1-RM 3.5% (↑) in 17% (↑) in NA The cuff pressure: (2005a) x 15 reps of quadriceps MVC day 1= 160 day4= knee 14% (↑) in 220 mmHg. extension 1-RM 30 sec rest between sets. Abe et al. E 2 wk 9 M 6x/wk 3 x 15 reps 20% 1-RM 8.5% (↑) in 16.8% (↑) in NA The cuff pressure= (2005b) of squad + mid-thigh squad Day 1=160 leg press 22.6% (↑) in leg Day 9= 240 mmHg curl 30 sec rest C 2 wk 7 M 6x/wk 3 x 15 reps 20% 1-RM 1.8% (↑) in 8.9% (↑) in NA between sets. of squad + mid-thigh squad leg press 1.3% (↑) in leg curl Abe et al. E 3 wk 9M 2x /d 5x 2min 50m/min 5.7% (↑) in 7.4% (↑) in leg NA The cuff pressure: (2006) 6x/wk walking Quads press (1-RM) 200 mmHg 7.6% (↑) in 8.3% (↑) in leg hamstrings curl (1-RM) Hamstrings Walking study 10.4% (↑) in knee ex. (MVC) 9.4% (↑) in knee flex. (MVC) No sig. change

C 3 wk M 2x /d 5x 2min 50m/min No sig. NA 6x/wk walking change Burgomaster E 8 wk 8 M 2x/wk 2x /10 + 50% 1-RM NA 10.5% (↑) in NA The cuff et al. (2003) 1x/failure isokinetic pressure: (1st 2 wk) strength 100 mmHg # of sets 22% (↑) in increased isotonic One min rest by 1-set/wk strength between sets 5x /10 + 1x and 5 min rest / failure between (from wk 5 blocks (3 to 8) sets= a block)

C 8 wk 8 M 2x/wk # of 50% 1-RM NA 9.6% (↑) in NA The repetitions isokinetic contralateral were strength arms were matched 23% (↑) in trained with the isotonic without occluded strength occlusion arm Ishii et al. E 8 wk 11 F 3x/wk 6 exercises NA 3% increase NA NA The cuff (2005) (knee-up, pressure: bent-knee 50-80 for push up, upper limbs leg raise, 80-120 seated knee mmHg for flexion, lower limbs. squad, and (KAATSU forward sportswear) lunge). Circuit C 8 wk 11 F 3x/wk Number of No sig. change NA NA training repetitions (No external varied. loading) Moore et E 8 wk 8 M 2x/wk 2x /10 + 50% 1-RM NA 22% (↑) in 51% (↑) in PAP The cuff al. (2004) 1x/failure dynamic No sig. change in pressure: (1st 2 wk) strength EMG activity & 100 mmHg # of sets 8% (↑) in MVC motor unit activation. increased One min rest by 1-set/wk Greater relative (↑) in between sets and 5x /10 + 1x EMG activity from 5 min rest / failure 1st rep of set-1 to 1st between blocks (from wk 5 rep of set-3 (3 sets= a block) to 8) 21% (↓) in resting twitch peak torque The contralateral C 8 wk 8 M 2x/wk # of 50% 1-RM NA 23% (↑) in No sig. change in arms were repetitions dynamic PAP, EMG activity, trained without were strength & motor unit occlusion matched No sig. change activation with the in MVC occluded arm Sata S. E 3 wk 1 M 5-6x/wk 3 x 15 30% 1-RM 7 mm (↑) in NA NA Subject was one (2005) (8 right thigh patella tendinitis exercises) and patient 2 mm (↑) in left thigh circum.

Table was organized according to alphabetical order of names. N= Number of subjects; Freq= Frequency; Rep= Repetitions; E = Exercise group; C= Control group; M= Male; F= Female; NA= Not applicable. 4 Overview of Neuromuscular Adaptations of Skeletal Muscle to KAATSU Training

Table 1. (continued) Author Group Duration N Gender Freq Set x Rep Intensity Change in Change in Change in EMG, Comments of Study (d/wk) CSA Strength MMG, motor unit (Week) Increase (↑ ) Increase (↑ ) activation, PAP Decrease (↓ ) Decrease (↓ ) Increase (↑ ) Decrease (↓ )

Shinohara E 4 wk 5 M 3x/wk ~ 36x 40% MVC NA 9% & 26% (↑) NA The cuff et al. isometric in ischemic-leg pressure: (1998) knee after 2-wk & 4- >250 mmHg extension wk, respectively Same subjects (2s on 3s trained with one off) No sig. change leg ischemic and in non-ischemic- the other non- leg ischemic Takarada E 2 wk 8 4M 5 x 5 min A cuff was 9.4% (↓) in NA NA Mean cuff et al. 4F 2x/d blood flow inflated knee pressure: (2000a) 12 restriction extensors 238 mmHg days 9.2% (↓) in (betwe knee flexors 3 min rest en the between 3rd No exercise occlusions and 14th Patients with an C 2 wk 8 4M days A cuff was 20.7% (↓) in NA NA operation for the 4F after on, but not knee reconstruction operati inflated extensors of the anterior on) 11.3% (↓) in cruciate knee flexors ligament Takarada E 8 wk 6 M 2x/wk Subjects 50% 1-RM 12.3% (↑) in 12.3% (↑) in NA Mean cuff et al. repeated knee isokinetic torque pressure: (2002) the lifting extensors (averaged over 200 mmHg (knee all velocities) extension) 30 sec rest until failure between sets. 4x

E 8 wk 6 M 2x/wk # of 50% 1-RM No sig. 3.2% (↑) in NA repetitions change isokinetic torque were (averaged over matched all velocities) with vascular occlusion group No sig. C 8 wk 5 M 2x/wk untrained change No sig. change NA Takarada E 8 wk 6 M 2x/wk 5x subjects 20% 1-RM 10.3% (↑) in 9.2% (↑) in NA Mean cuff et al. repeated knee isokinetic pressure: 218 (2004) the lifting extensors strength mmHg until failure 1-minute rest between sets. E 8 wk 6 M 2x/wk 5x subjects 20% 1-RM No sig. 3.1% (↑) in NA repeated change isokinetic the lifting strength until failure

C 8 wk 6 M 2x/wk 10 min untrained No sig. 2.8% (↑) in NA vascular change isokinetic occlusion strength Takarada E 16 wk 11 W 2x/wkSubjects ~30-50% 1- 20.3% (↑) in 18.4% (↑) in Sig. (↑) in iEMG Mean cuff et al. performed RM biceps brachii isokinetic compared to exercise pressure: 110 (2000b) 5 sets of 17.8% (↑) in strength of same intensity mmHg single-arm brachialis without restriction dumbbell 1-minute rest curl, each ~50-80% 1- 18.4% (↑) in 22.6% (↑) in between sets. set until RM biceps brachii isokinetic failure 11.8% (↑) in strength Repeated the brachialis lifting until failure. E 16 wk 8 W 2x/wk# of ~50% 1- 6.9% (↑) in 1.04% (↑) in No sig. change repetitions RM biceps brachii isokinetic In the subjects were 3.8% (↑) in strength of occlusion matched brachialis group, the with contralateral vascular arms were occlusion trained with a group high intensity C 16 wk 5 W 2x/wk5x of untrained No sig. No sig. NA exercise (80% 1- single-arm change change RM). dumbbell curl Yasuda et E 2 wk 3 M 2x/d 3x 15 20% 1-RM 7.8% (↑) in 14% (↑) in 1- NA The cuff al. (2005) 6x/wk (leg curl quadriceps RM (squat) pressure= and squat) Day 1=160 Day 9= 240 C 2 wk 2 M 2x/d 3x 15 20% 1-RM 1.8% (↑) in 9.1% (↑) in 1- NA mmHg 6x/wk (leg curl quadriceps RM (squat) 30 sec rest and squat) between sets and exercises. Table was organized according to alphabetical order of nam es. N= Number of subjects; Freq= Frequency; Rep= Repetitions; E = Exercise group; C= Control group; M= Male; F= Female; NA= Not applicable. M. Karabulut, T. Abe, Y. Sato, et al. 5

KAATSU technique has also been used with different patients. The CSA of the knee extensors in athletes modes of exercise to investigate skeletal muscle increased by 12.3% after an 8-week period of adaptation and response. Three weeks of twice-daily KAATSU resistance training at 50% of 1-RM walk training combined with vascular restriction indicating that low-intensity exercise with vascular (LIWT+R) compared to walking alone (LIWT) restriction can increase muscle size and strength resulted in an increase in quadriceps muscle CSA of regardless of training status [Takarada et al., 2002]. 5.7% and 1.5%, respectively (Abe et al., 2006), 7.5% and -0.6%, respectively [Beekley et al., 2005], and Rehabilitation hamstring muscle CSA of 7.6% and -1.7%, It was reported that low intensity KAATSU respectively [Abe et al., 2006]. resistance training has also been used as part of the Using a different approach, subjects wearing rehabilitation process in Japan [Sata, 2005]. A patient “KAATSU Sportswear” (PHENIX Co. Ltd., Tokyo with patellar tendinitis incorporated KAATSU training Japan) performed a circuit-training protocol only on the right injured limb along with exercises for using body weight as the external load. The protocol both lower extremities at 30% 1-RM for 3 weeks. It consisted of six exercises (Table 1) with blood flow was reported that the patient was able to begin restriction to both upper and lower limbs for 8 weeks. jogging one week after beginning the KAATSU The proximal ends of upper and lower limbs were training and that thigh circumference increased by 7 compressed by elastic belts to restrict blood flow. The mm for the injured right leg and 2 mm for the blood flow restriction pressure was determined by the uninjured left leg after three weeks of KAATSU stretched distance of the elastic belts and the training. It should be noted that the patient received circumference of the limbs. Thigh muscle CSA both anti-inflammatory drugs and a steroid injection; increased by ~3% in KAATSU group but no change therefore the training results are somewhat was observed after circuit training without blood flow confounded by the administration of the drugs. restriction, although there was no statistical difference However, the quick recovery of this patient suggests between the two groups (Ishii et al., 2005). These that this training method may be safe and decrease studies indicate that the combination of KAATSU recovery times in these types of patients. In addition, technique with different modes of training programs the application of vascular restriction without any may also be used to elicit hypertrophy but further exercise for a 2-week period resulted in disuse- research is needed to support these claims. induced decreases in muscle CSA of the knee extensors and flexors of -9.4 and -9.2%, respectively Age related adaptation and training status but were significantly less than those in a control Decreases in muscular strength with aging are group without KAATSU application (-20.7 and - attributed to declines in muscle fiber area [Grimby et 11.3%, respectively) [Takarada et al., 2000a]. Based al., 1982] and fiber number [Lexell et al., 1983]. on these findings, it can be suggested that blood flow Maintaining or improving muscular strength is very restriction alone may reduce atrophy associated with important for middle-aged and elderly populations so inactivity or when accompanied with low-intensity that quality of life can be maintained or improved. It exercise may increase muscle size in a variety of is known that high intensity exercise is needed to patient populations. induce muscle hypertrophy [Baechle and Earle, 2000], however, elderly people (70-79 years of age) 2. Strength and Neural Changes may be prone to orthopedic injury or be unable to a. Strength perform traditional high intensity strength testing and Duration and intensity of training training [Pollock et al., 1991]. Generally, strength adaptations have been assessed Middle-aged female subjects (47-67 yr) increased by measuring isometric [maximal voluntary their biceps brachii and brachialis muscle size by contraction (MVC)], isokinetic, or dynamic [one 20.3% and 17.8%, respectively, following a training repetition maximum (1-RM)] muscle strength, which protocol of five sets of single dumbbell curls at 30- may be due to neural adaptations, muscle 50% 1-RM with blood flow restriction for a 16-week hypertrophy, or both. Measuring changes in muscle training period [Takarada et al., 2000b]. However, the CSA or the total amount of muscle mass can explain same training program without blood flow restriction strength changes due to hypertrophy, whereas resulted in an increase in CSA of the biceps brachii of measuring motor unit activation (MUA), post only 6.9% and in the brachialis of 3.8%. This finding activation potentiation (PAP), recording suggests that KAATSU may be more effective and electromyography (EMG) and mechanomyography safer for improving muscle size in older individuals. (MMG) activities provides additional information The positive effects of KAATSU on muscle size and regarding any neural changes. strength have been reported not only in sedentary Traditional resistance training prgrams often report and active individuals but also in athletes and significant increases in both muscle hypertrophy and 6 Overview of Neuromuscular Adaptations of Skeletal Muscle to KAATSU Training

strength of 5 to 39% depending on the type of KAATSU was only 3.1%. Trained elite athletes also training (dynamic), the mode of testing (isokinetic, experienced a 14.3% strength gain after completion isometric, or dynamic), and duration of training of an 8-week KAATSU training program of the knee [Goto et al., 2004]. However, there is convincing extensor muscles at about 50% of 1-RM [Takarada et evidence in the literature to indicate that similar al., 2002]. benefits in terms of strength improvements can be achieved using much lower training intensities and Gender effects durations of training if combined with the KAATSU Although the subject population for most of the training technique (Table 1). KAATSU studies were young males, postmenopausal Following 8 weeks of unilateral elbow flexion females also increased isokinetic strength in elbow training (one arm was trained with restriction and the flexors by 18.4% following a 16-week resistance other without restriction) at 50% 1-RM, isometric training (30-50% 1-RM) combined with vascular MVC increased by 8.3% with blood flow restriction, restriction [Takarada et al., 2000b]. Subjects in the but no significant change was observed without KAATSU group exercised the contralateral arm with a restriction [Moore et al., 2004]. The same exercise high-intensity (80% 1-RM) exercise without protocol with blood flow restriction to only one limb restriction and increased isokinetic strength of the also resulted in a 10.5% increase in isokinetic elbow flexors by 22.6%, similar to the arm trained strength versus 9.6% without KAATSU and a 22% with blood flow restriction. However, when exercises increase in isotonic strength in elbow flexors with were performed at the same low intensity (30-50% KAATSU compared to a 23% increase without 1-RM) with no blood flow restriction, there was only KAATSU, with the increases in both conditions being a 1.0% increase in strength. Gender does not appear statistically similar [Burgomaster et al., 2003]. The to influence the adaptive ability of skeletal muscle in authors could not offer any physiological reasons response to KAATSU training, with similar why both limbs would respond in a similar fashion, adaptations being demonstrated by both males and contrary to all other published KAATSU protocols females. [Burgomaster et al., 2003]. We hypothesize that the adaptation to training may be affected by the mode of b. Neural response testing, because the mechanisms responsible for the Another noninvasive technique that has been used changes in strength may be similar for isokinetic and to determine motor unit activation and post isotonic strength, but different for isometric strength. activation potentiation (PAP) is twitch interpolation A 4-week training program of repeated isometric [Allen et al., 1995]. This technique involves electrical knee extensions at 40% of MVC resulted in stimulations applied to the muscle or nerve during significant increases in MVC values by 9% after the and after isometric MVC (Shield and Zhou, 2004). first 2-weeks and of 26% after the entire 4-week PAP, which can improve muscular performance, is training period [Shinohara et al., 1998]. When the first twitch obtained after a MVC trial [Moore et dynamic knee extension exercises at 20% 1-RM were al., 2004]. Eight weeks of low intensity (50% of 1- performed for 7 days, the authors reported a 17% RM) unilateral elbow flexion training with restricted and a 14% increase in MVC and 1-RM strength, blood flow resulted in a significant increase in PAP respectively [Abe et al., 2005a]. In a somewhat (51%), but no change was observed after low similar study, a low intensity resistance training intensity exercise without blood flow restriction. No protocol was used in combination with blood flow significant difference in increased dynamic strength restriction for two weeks, which resulted in 16.8% was reported between the two conditions (22% and 22.6% increases in squat and leg curl 1-RM increase with restricted blood flow and 23% increase strength, respectively. However, the control group without restriction); however, isometric strength performing the same exercises without blood (MVC) improved significantly more (8.3%) for the restriction experienced only 8.9% and 1.3% increases KAATSU condition compared to the control (no in squat and leg curl 1-RM strength, respectively [Abe change). Additionally, resting twitch torque was et al., 2005b]. In another 2-week study of twice-daily depressed by 21% with vascular occlusion but was training that included three sets of leg curls and not changed in the unrestricted blood flow condition squats at 20% 1-RM, the 1-RM squat strength which might be attributed to low frequency fatigue in increased by 14% [Yasuda et al., 2005]. Takarada et response to the KAATSU training regiment [Moore et al. (2004) reported a 9.2% increase in isokinetic al., 2004]. strength in the knee extensors after an 8-week training program consisting of five sets of knee ACUTE RESPONSES extension exercises (20% 1-RM) with KAATSU, but Neural response the isokinetic strength change in knee extensors in Surface electromyography (EMG) reflects the linear the group performing the same exercises without algebraic summation of muscle action potentials that M. Karabulut, T. Abe, Y. Sato, et al. 7

propagate within the electrode recording areas. The intensity for the first set was the same for both the time and frequency domains of the EMG signal may control and KAATSU session, but the intensity of reflect muscle activation (combination of motor unit exercise was higher in the KAATSU session during recruitment and firing rate) and motor unit action the forth set [Yasuda et al., 2006]. Takarada et al. potential conduction velocity via the global shape of (2000b) also reported that the relative iEMG was the action potentials, respectively [Basmajian and De 40% lower during low-intensity exercise (~50% 1- Luca, 1985]. EMG signals were recorded from the RM) without restriction compared to iEMG values triceps brachii and the pectoralis major during bench during high-intensity exercise (~80% 1-RM) with no press exercises with or without vascular restriction restriction indicating that there is a positive [Yasuda et al., 2006] (Table 2). Normalized integrated relationship between the level of the force exerted EMG (iEMG) increased gradually during four sets of and iEMG activity. Restriction pressure was increased the dynamic exercise at 30% 1-RM; however, the gradually during low-intensity exercise resulting in magnitude of the EMG response for both the triceps gradual increases in iEMG. This may be due to brachii and the pectoralis major were significantly increasing lactic acid production inhibiting higher when KAATSU was applied. contraction of muscle fibers leading to the Normalized iEMG determined that the exercise recruitment of additional motor units. However,

Table 2. The Acute Effects of Vascular Restriction on Skeletal Muscle Physiology Author Group Duration N Gender Set x Rep Intensity Change in Change in Change in EMG, Comments of Study CSA Strength MMG, motor unit (Week) Increase (↑ ) Increase (↑ ) activation, PAP Decrease (↓ ) Decrease (↓ ) Increase (↑ ) Decrease (↓ )

Karabulut E one session 12 M 5 x 20 20% 1-RM NA No sig. change 7% (↓) in et al. isometric in MVC, isometric (2006) knee MVC in extension No sig. change in Kaatsu session with EMG amplitude (not sig.) vs. Kaatsu (amp.), EMG mean 2% (↓) in (2s on 1s power frequency isometric off) (MPF), MMG amp, MVC in no- MMG MPF Kaatsu session C one session 12 M 5 x 20 20% 1-RM NA No sig. change There were sig. (not sig.) isometric in MVC difference between Same subject knee repetitions & MMG performed extension amp. increased from same exercises without set-1 to set-2 without Kaatsu Kaatsu (2s on 1s The cuff off) pressure= (Arm SBPx1.2)x 1.2 Takarada E one session 5 M Subjects -50% 1- NA NA Sig. (↑) in iEMG Mean cuff et al. performed RM (with compared to exercise pressure: 0- 100 (2000b) 5 sets of restriction) of same intensity mmHg single-arm without restriction dumbbell 1-minute rest curl, each between sets. set until failure Repeated the lifting until failure. E one session 5 M -80% 1- NA NA Sig. change RM 40% higher iEMG No sig. change (without than that of control between iEMG restriction) group with no- values @ 100 restriction mmHg and during high intensity without restriction C one session 5 M 5x of ~50% 1- NA NA NA single-arm RM dumbbell (without curl restriction)

Yasuda et E One 12 M & 30 reps + 30% 1-RM NA NA During first 30 reps= The cuff al. (2006) session F 3x 15 iEMG ~ 40% of 1- pressure= (bench RM Equaled to press) 3rd set= iEMG ~ 60- individual’s 70% 1-RM resting systolic blood C One 12 M & 30 reps + 30% 1-RM NA NA During first 30 reps= pressure session F 3x 15 iEMG ~ 40% of 1- (bench RM 30 sec rest press) 3rd set= iEMG ~ 50% between sets 1-RM Table was organized according to alphabetical order of names. N= Number of subjects; Freq= Frequency; Rep= Repetitions; E = Exercise group; C= Control group; M= Male; F= Female; NA= Not applicable. 8 Overview of Neuromuscular Adaptations of Skeletal Muscle to KAATSU Training

there was not a significant difference in iEMG values training programs may be the recruitment of more during low-intensity exercise with blood flow fast-twitch fibers and their higher threshold motor restriction at 100 mmHg and high-intensity exercise units. It is difficult to determine which factors are without restriction. A possible explanation for this more important since there are close relationships finding might be that the magnitude of blood pooling between these various factors. affected the surface EMG electrode recordings. Since low-intensity exercises combined with The mechanomyogram (MMG) records and vascular restriction requires less mechanical stress quantifies the low-frequency lateral oscillations of (20% versus 80% 1-RM), it may be an effective active skeletal muscle fibers [Barry and Cole, 1990; alternative method to increase strength and muscle Orizio, 1993]. During voluntary muscle actions, the size and used for in the elderly or for MMG signal represents a summation of the people with orthopedic injuries. In addition, KAATSU mechanical activity from individual motor units. The training programs may also provide an opportunity to time and frequency domains of the MMG signal have use different exercise modes such as walking for the been suggested to reflect motor unit recruitment and purpose of muscle hypertrophy and strength gains. In firing rate, respectively [Beck et al., 2007; Orizio, summary, additional studies are required to clarify the 1993]. MMG signals were recorded from the vastus physiology of the underlying factors associated with lateralis muscle during repetitive isometric KAATSU training; however, it seems to be a contractions at 20% MVC [Karabulut et al., 2006] potentially useful training method for improving the (Table 2). There were no significant interactions and quality of life in the elderly, enhancing performance no significant main effects for pre- versus post- in athletes, and shortening rehabilitation time in exercise or with- versus without blood flow patients. restriction for either MMG amplitude or MMG mean power frequency (MPF). MMG amplitude increased SUGGESTIONS FOR FUTURE RESEARCH from set 1 to 2, but there was no difference between One physiological system that needs further sets 2, 3, 4, and 5 for both the restricted and non- research is the area of bone physiology and the use of restricted sessions; however, the authors suggested KAATSU training. Various situations like that it was possible that the isometric exercise task rehabilitation from injury (limb immobilizations, was at too low of an intensity and did not result in casting, etc), bed rest (hip or knee replacement, etc), any substantial changes in motor unit firing rates and the loss of gravity (space flight) each have specific [Karabulut et al., 2006]. Table 2 summarizes the data needs for being able to prevent bone and muscle loss for the acute responses of skeletal muscle to a single which might be best accomplished with the aid of bout of KAATSU training. Since no previous studies blood flow restriction and low intensity exercise. have examined the MMG responses to KAATSU- Additionally, the longest published KAATSU related interventions, it was not possible to compare training study lasted 16 weeks; therefore, more these findings to other studies. research is needed to understand the long-term effects of KAATSU training, especially since bone is CONCLUSION typically much slower in responding to a training There seems to be some agreement that blood flow stimulus. Finally, other interesting areas of research restriction during low intensity exercise can could include the examination of the time course of potentiate physiological improvements in skeletal the adaptive changes following the termination of muscle, apparently independent of the commonly KAATSU training or the implications of switching accepted training principles associated with overload from KAATSU training to a traditional resistance and progression. These changes in skeletal muscle size training program (or vise versa) compared to similar and strength may possibly be through neuromuscular length, single mode training programs (KAATSU or adaptations such as improved muscle and/or nerve traditional resistance training). coordination and/or muscle hypertrophy and appear to be independent of gender, training status, and age. It should also be noted that there are probably References numerous factors involved in muscle hypertrophy Abe T, Yasuda T, Midorikawa T, Sato Y, Kearns CF, Inoue K, Koizumi and strength changes such as metabolite K, Ishii N (2005b) Skeletal muscle size and circulating IGF-1 are accumulation (lactic acid, ADP, etc.), induced increased after two weeks of twice daily “KAATSU” resistance training. hypoxia, reperfusion of the muscle, and localized or Int. J. KAATSU Training Res. 1:6-12. systemic endocrine responses (Growth Hormone, Abe T, Beekley MD, Hinata S, Koizumi K, Sato Y (2005a) Day-to-day Insulin-like Growth Factor-1, Testosterone, etc.). change in muscle strength and MRI-measured skeletal muscle size during One possible explanation for the relatively faster 7 days KAATSU resistance training: A case study. Int. J. KAATSU hypertrophic response (even after one week of Training Res. 1:71-76. Abe T, Kearns CF, Sato Y (2006) Muscle size and strength are KAATSU training) compared to traditional resistance increased following walk training with restricted venous blood flow from M. Karabulut, T. Abe, Y. Sato, et al. 9

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