Effect of Low-Intensity Aerobic Training Combined with Blood Flow Restriction on Body Composition, Physical Fitness, and Vascular Responses in Recreational Runners

is study investigated the effect of low-intensity aerobic training combined with blood ow restriction (LABFR) on body composition, physical tness, and vascular functions in recreational runners. The participants were 30 healthy male recreational runners, randomized between the LABFR (n= 15) and control (n= 15) groups. The LABFR group performed ve sets of a repeated pattern of 2 min running at 40% VO 2maxand 1 min passive rest, while wearing the occlusion cuff belts on the proximal end of the thigh. The frequency was three times a week for the period of eight weeks. The control group performed the identical running protocol without wearing the occlusion cuff belts. At the end of the training, the participants' body composition (fat mass, body fat, muscle mass, and right and left thigh circumference), physical tness (power and VO 2max), and vascular responses ( ow-mediated dilation (FMD), brachial ankle pulse wave velocity (baPWV), ankle brachial index (ABI), systolic blood pressure (SBP) and diastolic blood pressure

protocol without wearing the occlusion cuff belts. At the end of the training, the participants' body composition (fat mass, body fat, muscle mass, and right and left thigh circumference), physical tness (power and VO 2max), and vascular responses ( ow-mediated dilation (FMD), brachial ankle pulse wave velocity (baPWV), ankle brachial index (ABI), systolic blood pressure (SBP) and diastolic blood pressure (DBP)) were measured. The results showed a signi cant time group interaction effect on muscle mass (F = 53.242,p= 0.001, p 2= 0.664) and right thigh circumference (F = 4.544,p= 0.042, p 2= 0.144), but no signi cant variation in any other factors, including fat mass, body fat, left thigh circumference, FMD, baPWV, ABI, SBP, and DBP (p> 0.05). Overall, our results suggested that eight-week LABFR exerted a positive effect on the body composition, especially muscle mass and thigh circumference, of recreational runners. Keywords: blood ow restriction; body composition; low-intensity aerobic training; recreational runner; physical tness; vascular responses 1. Introduction Recent interest in the application of blood ow restriction (BFR) has focused on the effect of training in general training adaptations during periods of reduced blood ow [1]. In Japan, Dr. Yoshiaki Sato promoted “kaatsu training”, involving “training with added pressure” through which BFR became widely known to the general public [2]. In typical BFR training, a cuff/tourniquet system is used to apply a partial restriction to the arterial in ow in the working musculature during exercise, while the venous out ow is completely restricted [3] so that the consequent blood pooling allows for an increased training effect [4]. Recent evidence has indicated the superiority of the reinforced training stimuli using the combined BFR training compared to the same exercise without BFR training [5]. The BFR method is usually used during low-load resistance exercise, and has been shown to be effective in enhancing long-term hypertrophic and strength responses in both clinical and athletic populations [6]. According to several studies on BFR training, an increase in muscle strength and hypertrophy could be expected from the conventional resistance training only via high-intensity training using an approximately 70–85% load of one-repetition maximum (1

during low-load resistance exercise, and has been shown to be effective in enhancing long-term hypertrophic and strength responses in both clinical and athletic populations [6]. According to several studies on BFR training, an increase in muscle strength and hypertrophy could be expected from the conventional resistance training only via high-intensity training using an approximately 70–85% load of one-repetition maximum (1 RM), whereas the BFR training exerted a similar level of effect Healthcare2022,10, 1789.

Healthcare2022,10, 1789 2 of 9 using a 20–50% load of 1 RM [5–7]. In fact, BFR training has been shown to offer signi cant bene ts in the change in skeletal muscles in a number of studies, for example, by increasing the local muscle mass, strength, and endurance, despite the training being performed with lower resistance [8]. Moreover, several recent studies have reported a positive effect of BFR training in controlling the arterial compliance compared to the absence of BFR training, as well as stronger advantages in the change in vascular functions through four or more weeks of BFR training compared to conventional resistance training, thus, implicating a potential contribution in cardiovascular health [9]. Meanwhile, changes induced by low-intensity aerobic training combined with BFR (LABFR) have been investigated in recent studies, with the results showing the advan- tages of BFR training as a single mode of training based on the simultaneous increase in aerobic tness and muscular strength, in addition to the increased maximum oxygen uptake (VO2max), delayed onset of blood lactate accumulation, and enhanced economy of motion [10,11]. For these reasons, LABFR has been applied to individuals with a low level of training or a handicap in certain training, such as those recovering from an injury or those seeking assistive training to add new stimuli to aerobic training, and the reported effects were positive in inducing a variety of physiological changes [12–14]. In fact, Abe et al. [15] reported that, although the intensity of slow-walk training with BFR was set to a low level, secretion of growth hormone after acute exercise was increased and, after three weeks, the thigh muscle cross-sectional area and volume were increased by 4–7%. In a recent study by Pinheiro et al. [12], trained cyclists with knee osteoarthritis performed low-intensity aerobic training combined with BFR for nine weeks, in which a positive change was found, not only for aerobic tness such, as with 20 km cycling time-trial performance and peak oxygen consumption (VO 2peak), but also for right and left leg maximal strength and the cross-sectional area of the vastus lateralis. These studies on LABFR

with knee osteoarthritis performed low-intensity aerobic training combined with BFR for nine weeks, in which a positive change was found, not only for aerobic tness such, as with 20 km cycling time-trial performance and peak oxygen consumption (VO 2peak), but also for right and left leg maximal strength and the cross-sectional area of the vastus lateralis. These studies on LABFR involved individuals who were injured or poorly trained. However, in some cases, low-intensity aerobic training is one of the training strategies used by recreational runners. High-intensity interval training can increase catabolic hormones, such as cortisol, which inhibit muscle protein synthesis, reducing muscle hypertrophy and muscle strength development [16,17]. In addition, BFR changes acute physiological stressors, such as local muscle oxygen availability and vascular shear stress, which can lead to adaptations that cannot be easily obtained with traditional training [1]. These advantages can provide positive effects for recreational runners. However, research on the positive effects of LABFR for recreational runners is limited. Thus, this study aimed to investigate the effect of an eight-week protocol of LABFR on body composition, physical tness, and vascular responses in recreational runners. We hypothesized that regular LABFR training will increase the body composition, physical tness, and vascular responses in recreational runners. 2. Methods 2.1. Subjects Thirty health male recreational runners participated in this study. A recreational runner was de ned as an individual who had regularly participated in running three times a week for a minimum of six months. The sample size was estimated by setting the effect size to 0.25 with an alpha level ofp 0.05 and statistical power > 0.80. As a result, the sample size required for this study wasn= 24. Considering the drop-out rate, a total of 30 individuals were recruited. Individuals who received an operation related to a musculoskeletal disorder in the past six months, those with an injury history, and those with a vascular health problem (e.g., hypertension or deep vein thrombosis, or distended varicose veins) or a history of medical treatment or drug administration, were excluded. Prior to the experiment, the participants were given detailed explanations on the purpose,

who received an operation related to a musculoskeletal disorder in the past six months, those with an injury history, and those with a vascular health problem (e.g., hypertension or deep vein thrombosis, or distended varicose veins) or a history of medical treatment or drug administration, were excluded. Prior to the experiment, the participants were given detailed explanations on the purpose, procedures and methods of the experiment, and all participants voluntarily signed an informed consent form. The 30 participants were randomized between the LABFR group (n= 15) and the control group (n= 15), but 1 from the LABFR group dropped out of the

Healthcare2022,10, 1789 3 of 9 study for a personal reason, leaving 14 individuals in the LABFR group and 15 individuals in the control group at the end of the experiment (Table). An independent t-test found no signi cant differences between groups for the variables of age, height, weight, body mass index (BMI), and body fat (p> 0.05). The study procedures and methods, and the consent form, were approved by the university's Institutional Review Board. The study was conducted between April 2021 and January 2022. Table 1.Physical characteristics of the subjects. LABFR (n= 14) CON ( n= 15) Age (years) 30.21 4.93 29.67 3.06 Height (cm) 175.07 8.46 172.27 5.66 Weight (kg) 75.23 9.08 73.59 10.68 BMI (kg/m 2 ) 24.44 2.32 24.63 2.77 Body fat (%) 12.54 4.27 15.33 5.05 Data are presented as mean standard deviation (SD); BMI, body mass index; LABFR, low-intensity aerobic training combined with blood ow restriction group; CON, control group. 2.2. Low-Intensity Aerobic Training Combined with Blood Flow Restriction Participants visited a laboratory with BFR equipment to perform training. Here, VO2maxwas measured for LABFR. Before the VO2maxmeasurement, the participants at- tended an education session on relevant procedures and precautions. Afterwards, each participant performed a warm-up on the treadmill, followed by exercise at 1.7 mph with 10% slope. At every 3 min interval, the speed was increased by 0.8–0.9 mph, and the slope was increased by 2% as part of the Bruce protocol to measure the VO2max. In the measurements, gas analyzers (Quark b, Cosmed, Rome, Italy) were concurrently applied, after adjustments for the daily volume, humidity, and temperature. The criteria of VO2max were (i) a change in VO2 2 mL kg 1 min 1 ; (ii) respiratory exchange ratio 1.1; (iii) age- predicted maximal heart rate 85%. Before performing LABFR, 10 min of light jogging was performed as a warm-up. Afterwards, each participant wore an occlusion cuff belt (KAATSU NANO, KAATSU JAPAN, Tokyo, Japan) at the proximal end of both thighs (Figure). For LABFR, each participant repeated a pattern of 2 min running on a treadmill (HERA-9000, Health-One, Goyang, Republic of Korea) with the exercise

rate 85%. Before performing LABFR, 10 min of light jogging was performed as a warm-up. Afterwards, each participant wore an occlusion cuff belt (KAATSU NANO, KAATSU JAPAN, Tokyo, Japan) at the proximal end of both thighs (Figure). For LABFR, each participant repeated a pattern of 2 min running on a treadmill (HERA-9000, Health-One, Goyang, Republic of Korea) with the exercise intensity set to 40% VO2max, followed by a 1 min passive rest, performing a total of ve sets. The total time taken for exercise was 15 min. The pressure range during LABFR was set to 160–240 mmHg, because the use of LABFR with higher occlusion pressures ( 130 mmHg) has been shown to improve both the aerobic tness and aerobic performance in young adults [18]. Partic- ipants performed LABFR three times per week for a period of eight weeks. They were instructed to take suf cient recovery time after training, and were also asked to avoid consuming caffeine-containing foods and beverages for 24 h before training. The LABFR protocol in this study was designed with reference to previous studies [2,18]. The LABFR protocol used in this study was registered at July 2022). The control group performed the same protocol as the LABFR group without wearing the occlusion cuff belts for blood ow restriction. 2.3. Body Composition The body composition (fat mass, body fat, and muscle mass) of the participants was measured using a bioelectrical impedance analysis device (InBody-270, Biospace, Seoul, Republic of Korea) [19]. For accurate measurements, the participants were prohibited from performing excessive physical activity or exercise on the day prior to the day of measurement. They were also advised not to drink caffeinated or alcoholic beverages with a potential effect on moisture imbalance, although they were allowed to drink an adequate quantity of water. After a minimum of 8 h of fasting, the measurements were taken during the morning hours. The thigh circumference was also measured to examine the changes in muscle hypertrophy [20]. For this, while the participant's leg was in a natural extension

drink an adequate quantity of water. After a minimum of 8 h of fasting, the measurements were taken during the morning hours. The thigh circumference was also measured to examine the changes in muscle hypertrophy [20]. For this, while the participant's leg was in a natural extension

Healthcare2022,10, 1789 4 of 9 state, a spot 18 cm from the knee joint was marked with ink and the circumference around the spot was measured using a berglass tape (Gulick II, Country Technology Inc., Gays Mills, WI, USA).Healthcare 2022, 10, 1789 4 of 9 Figure 1. Occlusion cuff belts used in this study for blood flow restriction. 2.3. Body Composition The body composition (fat mass, body fat, and muscle mass) of the participants was measured using a bioelectrical impedance analysis device (InBody-270, Biospace, Seoul, Republic of Korea) [19]. For accurate measurements, the participants were prohibited from performing excessive physical activity or exercise on the day prior to the day of measurement. They were also advised not to drink caffeinated or alcoholic beverages with a potential effect on moisture imbalance, although they were allowed to drink an adequate quantity of water. After a minimum of 8 h of fasting, the measurements were taken during the morning hours. The thigh circumference was also measured to examine the changes in muscle hypertrophy [20]. For this, while the participant’s leg was in a natural extension state, a spot 18 cm from the knee joint was marked with ink and the circumference around the spot was measured using a fiberglass tape (Gulick II, Country Technology Inc., Gays Mills, WI, USA). 2.4. Physical Fitness The physical fitness was measured and subdivided into power and cardiorespiratory fitness. Power was measured using the vertical jump. For this, a jump-MD (TKK-5406, TAKEI, Niigata, Japan) was used. While standing on a mat with the feet aligned with each respective shoulder, the participant made as high a vertical jump as possible through the instant flexion and extension of the knees at the investigator’s signal. The measurements were taken twice, and the higher of the two values was recorded. The participant was cautioned against jumping through rebounding. For cardiorespiratory fitness, the VO2max was measured. The measurement procedure for VO2max has already been described in detail in Section 2.2. 2.5. Vascular Responses Flow-mediated dilation (FMD) is a method of assessing the endothelial functions based on the level of expansion of the brachial

the higher of the two values was recorded. The participant was cautioned against jumping through rebounding. For cardiorespiratory fitness, the VO2max was measured. The measurement procedure for VO2max has already been described in detail in Section 2.2. 2.5. Vascular Responses Flow-mediated dilation (FMD) is a method of assessing the endothelial functions based on the level of expansion of the brachial artery in response to the nitric oxide pro- duced by vascular endothelial cells. To measure the FMD, an ECG-guided high-resolution B-mode ultrasound system (UNEX-EF-38G, UNEX Corp., Nagoya, Japan) was used to measure the baseline diameter of the brachial artery at rest, and the maximum diameter after applying shear stress to express the change in brachial arterial diameter as a ratio was determined [21]. The respective equation for FMD is as follows: FMD = [(maximal diameter–baseline diameter)/baseline diameter × 100]. The brachial ankle pulse wave ve- locity (baPWV) of each participant in the supine position was measured using a non-in- vasive vascular screening device (VP-1000 Plus, Omron, Kyoto, Japan) after at least 5 min of rest. The sampling time for one pulse wave recording was 10 sec. For each participant, Figure 1.Occlusion cuff belts used in this study for blood ow restriction. 2.4. Physical Fitness The physical tness was measured and subdivided into power and cardiorespiratory tness. Power was measured using the vertical jump. For this, a jump-MD (TKK-5406, TAKEI, Niigata, Japan) was used. While standing on a mat with the feet aligned with each respective shoulder, the participant made as high a vertical jump as possible through the instant exion and extension of the knees at the investigator's signal. The measurements were taken twice, and the higher of the two values was recorded. The participant was cautioned against jumping through rebounding. For cardiorespiratory tness, the VO2max was measured. The measurement procedure for VO2max has already been described in detail in Section. 2.5. Vascular Responses Flow-mediated dilation (FMD) is a method of assessing the endothelial functions based on the level of expansion of the brachial artery in response to the nitric oxide produced by vascular endothelial cells. To measure the FMD,

rebounding. For cardiorespiratory tness, the VO2max was measured. The measurement procedure for VO2max has already been described in detail in Section. 2.5. Vascular Responses Flow-mediated dilation (FMD) is a method of assessing the endothelial functions based on the level of expansion of the brachial artery in response to the nitric oxide produced by vascular endothelial cells. To measure the FMD, an ECG-guided high-resolution B-mode ultrasound system (UNEX-EF-38G, UNEX Corp., Nagoya, Japan) was used to measure the baseline diameter of the brachial artery at rest, and the maximum diameter after applying shear stress to express the change in brachial arterial diameter as a ratio was determined [21]. The respective equation for FMD is as follows: FMD = [(maximal diameter– baseline diameter)/baseline diameter 100]. The brachial ankle pulse wave velocity (baPWV) of each participant in the supine position was measured using a non-invasive vascular screening device (VP-1000 Plus, Omron, Kyoto, Japan) after at least 5 min of rest. The sampling time for one pulse wave recording was 10 s. For each participant, two consecutive measurements were taken and the mean of two values was used in the analysis. The factors that determine a pulse wave are time difference (DT), distance between two measured spots (L), and participant's height (cm). The pulse wave (L/DT, cm/s) for an arterial segment was automatically calculated by the device [22]. Ankle brachial index (ABI) was measured using the same device as in the baPWV measurements. The cuff was applied to the limbs of each participant in the supine position, after at least 10 min of rest. The systolic blood pressure (SBP) was measured at the left and right brachial artery and the left and right posterior tibial artery, and by dividing the highest posterior tibial arterial pressure by the highest brachial arterial pressure, the ratio for ABI was obtained [23]. The respective equation for ABI was as follows: ABI = (highest left and right ankle systolic blood pressure)/(highest left and right arm systolic blood pressure).

The study examines the impact of a training protocol on body composition and fitness in recreational runners.