Acute hemoglobin responses during bench press exercise across relative loads and sport backgrounds: a cross-sectional functional near-infrared spectroscopy study.
Toru Kosuge; Tadamitsu Matsuda; Susumu Yoshida; Kodai Sugawara; Hiroku Mitsuya; Takayoshi Hakkaku; Shogo Okamura; Toshihiko Hashimoto; Takashi Okada
European journal of applied physiology, 30 Jun. 2026
PURPOSE: To compare acute hemoglobin responses during bench press (BP) exercise among bodybuilders (BB), powerlifters (PL), Paralympic powerlifters (PP), and untrained controls (CON), with emphasis on relative load and sport background. METHODS: Thirty-eight participants (BB, n = 10; PL, n = 10; PP, n = 8; CON, n = 10) performed ten BP repetitions at 20%, 40%, and 60% of one-repetition maximum (1RM). Multichannel functional near-infrared spectroscopy (fNIRS) was used to assess oxygenated hemoglobin (O₂Hb), deoxygenated hemoglobin (HHb), and total hemoglobin (tHb) responses over the C3-Cz-C4 region. Linear mixed models were used to test the effects of group, condition, and their interactions. RESULTS: The main effect of condition was significant for ΔO₂Hb in nine of ten channels and for ΔtHb in one channel (p_FDR_channel < 0.05). No group effects or group × condition interactions were observed for ΔO₂Hb, ΔHHb, or ΔtHb. Within-group post hoc analyses showed that ΔO₂Hb differences were observed mainly between 20 and 40% of 1RM (p_FDR_slice < 0.05), with fewer additional differences involving 60% of 1RM. CONCLUSION: Acute hemoglobin responses during BP were expressed primarily as ΔO₂Hb changes and were associated with relative load under the present low-to-moderate load conditions. Because group effects and group × condition interactions were not supported, these findings should be regarded as preliminary and descriptive rather than evidence of sport-specific adaptation or between-group differences in response magnitude. Observed O₂Hb changes represent regional hemodynamic responses, not direct measures of cortical activation or motor control processes.

Electromyographic activity during bench press differs by attentional focus strategy and sport: a cross-sectional comparison of bodybuilding, powerlifting, and paralympic powerlifting.
Toru Kosuge; Hiroku Mitsuya; Takayoshi Hakkaku; Shogo Okamura; Takashi Okada
European journal of applied physiology, Jun. 2026
PURPOSE: To provide new insights into the regulation of muscle activation by attentional focus strategies by examining whether differences in attentional focus among athletes who use the bench press (BP) as part of their training are reflected in distinct acute electromyography (EMG) responses during BP. METHODS: Thirty-seven participants were included: ten bodybuilding (BB) athletes, ten powerlifting (PL) athletes, seven paralympic powerlifting (PP) athletes, and ten untrained controls (CON). BP tests were performed under four conditions: external focus, pectoralis internal focus (IF), triceps IF, and a no-instruction baseline. Under each condition, the participants completed three repetitions at 60% and 80% of the One-repetition maximum (1RM). The surface EMG of the pectoralis major and lateral and long heads of the triceps brachii were recorded and normalized to the maximum voluntary contraction. RESULTS: At 60% 1RM, selective activation of the pectoralis major during BP was observed only in the BB group (p < 0.01) and not in the PL, PP, or CON groups. Across conditions, the long-head EMG of the triceps in the PP group was consistently higher than that in the other groups under every condition (p < 0.05, p < 0.01), whereas no significant between-group differences were observed for the pectoralis or triceps lateral-head EMG. CONCLUSION: The findings indicate that even among athletes proficient in the same BP exercise, attentional focus influences EMG amplitude depending on the combination of sport-specific characteristics and load intensity. These differences suggest the presence of sports-specific and intensity-dependent differences in the neural control of force production.

The angle-based dynamic control ratio in isokinetic fatiguing knee flexion-extension effort: A study of healthy subjects.
Kodai Suzuki; Takashi Okada; Takayoshi Hakkaku; Shohei Shimowada; Michal Katz-Leurer; Zeevi Dvir
Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology, Dec. 2025
This study examined the angle-based variations in the dynamic control ratio (DCRab), defined as the peak concentric moment of the quadriceps (Qcon) divided by its hamstring counterpart (Hecc) when calculated calculated at 1° intervals, during isokinetic fatiguing conditions. Sixteen men performed 30 maximal concentric knee extensions and eccentric flexions of the right and left knees at speeds of 120°/s and 180°/s. Data were analyzed using ratio values extracted from three repetition segments (4-6, 14-16, and 27-29) and presented graphically. All DCRab curves followed asymmetric second-order patterns, with the values near end-RoM (full extension: 5-7°) significantly higher than at RoM onset (95° of flexion), reflecting increased hamstring moment output. Fatigue reduced the Q and H moment at the equilibrium point [DCRe(M); Hecc = Qcon] and shifted the angle at which the DCRe occurred [DCRe(∠)] rightward, indicating altered muscle balance. DCRe(M) correlated with DCRe(∠): r = 0.84-0.90, while the DCRe(∠) correlated with angle of peak moment (r = 0.63-0.88), especially at 180°/s. Notably, the DCRe(∠) occurred at 20-30° of knee extension and correlated with the angle of peak moment of Hecc at 180°/s, indicating enhanced joint protection. No significant inter-limb differences were found in either Qcon or Hecc strength (p = 0.520). The use of the DCRab and its derivatives, the DCRe(M) and DCRe(∠) indicates that fatigue may affect Q-H balance. Thus, these parameters may aid in assessing the risk of knee injury and design of rehabilitation protocols.

Running Acceleration Correlates With T2 Magnetic Resonance Imaging Values of the Lumber Intervertebral Disc.
Takayoshi Hakkaku; Yoshiaki Kubo; Koji Koyama; Koichi Nakazato; Takashi Okada; Kenji Hiranuma
Translational sports medicine, 2025
Background: Running can contribute to both beneficial and detrimental responses in the intervertebral discs (IVDs). To better understand these effects, we investigated the relationship between loading directions during slow running and the rapid changes in T2 times occurring in the lumbar IVDs before and after running. Methods: Sixteen healthy male students were fitted with a triaxial accelerator and ran on a treadmill at 8 km/h for 1 minute. Three lumbar T2 times from the L3/L4 to L5/S1 levels were measured before, immediately after, and 30 min postexercise via magnetic resonance imaging (MRI). The analysis focused on five regions of interest within each disc. Results: Acceleration was 0.23 ± 0.06 root mean square in the mediolateral (X-axis), 1.37 ± 0.08 in the vertical (Y-axis), and 0.30 ± 0.06 in the anteroposterior (Z-axis) direction. A strong correlation was observed between the T2 relaxation times and acceleration, particularly in the Z-axis. At L3/L4, a positive correlation was observed for the posterior nucleus (r = 0.72, p=0.002, R 2 = 0.59). At L4/L5, a positive correlation was observed for the central nucleus (r = 0.73, p=0.003, R 2 = 0.49). At L5/S1, a negative correlation was observed for the anterior annulus fibrosus (r = -0.73, p=0.01, R 2 = 0.48). Conclusion: These results suggest that anteroposterior loading may play a significant role in the response of the IVDs to running.

Hip flexion angle affects longitudinal muscle activity of the rectus femoris in leg extension exercise.
Hiroku Mitsuya; Koichi Nakazato; Takayoshi Hakkaku; Takashi Okada
European journal of applied physiology, Jun. 2023
PURPOSE: We investigated the effect of the hip flexion angle (HFA) on the longitudinal muscle activity of the rectus femoris (RF) during leg extension exercise (LEE). METHODS: We conducted an acute study in a specific population. Nine male bodybuilders performed isotonic LEE using a leg extension machine at three different HFAs: 0°, 40°, and 80°. Participants extended their knees from 90° to 0° at each HFA setting for four sets of ten repetitions at 70% of the one-repetition maximum. The transverse relaxation time (T2) of the RF was measured before and after LEE using magnetic resonance imaging. We analyzed the rate of change in the T2 value in the proximal, middle, and distal regions of the RF. The subjective sensation of muscle contraction of the quadriceps was measured using a numerical rating scale (NRS) and compared with the T2 value which was the objective index. RESULTS: At 80°, the T2 value in the middle RF was lower than that in the distal RF (p < 0.05). The T2 values at 0° and 40° HFA were higher than those at 80° HFA in the proximal (p < 0.05, p < 0.01) and middle RF (p < 0.01, p < 0.01). The NRS scores were inconsistent with the objective index. CONCLUSION: These results suggest that the 40° HFA is practical for region-specific strengthening of the proximal RF, and subjective sensation alone as an indication of training may not activate the proximal RF. We conclude that activation of each longitudinal section of the RF is possible depending on the hip joint angle.

The dynamic control ratio and its equilibrium point: A preliminary study of isokinetic fatiguing internal-external rotational effort of the shoulder joint in healthy subjects.
Kodai Suzuki; Takashi Okada; Hakkaku Takayoshi; Michal Katz-Leurer; Zeevi Dvir
Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology, Jun. 2023
The shoulder joint-related dynamic control ratio (DCR) is derived by dividing the peak eccentric moment of the external rotators (ER) by the peak concentric moment of the internal rotators (IR). However, given the inherent limitation associated with a single value DCR, an alternative approach is to calculate it at fixed angular intervals. This preliminary study aimed at exploring the variation in the DCR at a resolution of 1° and under fatiguing external and internal rotation exertions. Eighteen young men, 10 experienced and 8 without experience in overhead sporting activities completed two separate series of 45 ER eccentric and 45 IR concentric isokinetic repetitions at 120°/s. The analysis focused on repetitions 1-3 (TR1), 21-23 (TR2) and 41-43 (TR3). The relative fatigue values for both muscle groups and for both E and NE participants were 25-40% with significantly higher fatigue resistance in eccentric compared with concentric exertions. The DCR traces varied substantially linearly for most of the internal rotation range of motion while significant differences (p < 0.001) were found in their values within group between TR1, TR2 and TR3 and between experienced and non-experienced participants. An antagonistic moment equilibrium (DCR = 1) was reached in all instances and for both groups only during TR3 with a significant progressive reduction in this moment as fatigue increased. Thus, considering the DCR as an angle-based variable rather than a single value isokinetic parameter, may add new insight regarding the interplay between the rotatory muscles of the shoulder joint.

The association of lower trunk muscle strength with low back pain in elite lightweight judokas is dependent on lumber spine abnormalities
Takashi Okada; Kazunori Iwai; Takayoshi Hakkaku; Koichi Nakazato
ISOKINETICS AND EXERCISE SCIENCE, 2022

Weight Category-dependent Trunk Muscle Strength and its Relation with LBP in Elite Judokas.
Takashi Okada; Takayoshi Hakkaku; Kazunori Iwai; Koichi Nakazato
Sports medicine international open, Jan. 2021
Trunk muscle strength (TMS), especially rotator, is an important factor for both athletic performance and injury risks in judokas. However, the characteristics of TMS that depend on weight categories are still unclear. Although inadequate TMS might cause low back pain (LBP), the relationship between these two variables is not fully understood. In this study, weight category-dependent TMS and its relationship with LBP was investigated in Japanese judokas. The subjects were 66 male collegiate judokas, who were classified into the lightweight (N=14), middleweight (N=29) or heavyweight (N=23) category. The peak torques of extensor, flexor and rotator muscles were measured. The LBP group and non-LBP group were defined by questionnaire. TMS (normalized by body weight) in the heavier weight category showed a lower tendency in comparison with other categories, except for rotator strength. Significant differences were observed in the extensors (90 and 120 °/s; P<0.05) and flexors (60, 90 and 120 °/s; P<0.05). The LBP group (N=9) only showed significantly lower extensor (60 °/s; P<0.05) and right-rotator (60 °/s; P<0.01) strength in the heavyweight category compared with the non-LBP group (N=14). The relative TMS of judokas decreased in the heavyweight category, except for trunk rotator strength. Notably, low trunk extensor and rotator strengths are risk factors for LBP in heavyweight judokas.

The Effect of a Previous Strain Injury on Regional Neuromuscular Activation Within the Rectus Femoris.
Yoshiaki Kubo; Kohei Watanabe; Koichi Nakazato; Koji Koyama; Takayoshi Hakkaku; Shoya Kemuriyama; Masakazu Suzuki; Kenji Hiranuma
Journal of human kinetics, Mar. 2019
The rectus femoris (RF) has a region-specific functional role; that is, the proximal region of the RF contributes more than the middle and distal regions during hip flexion. This study aimed to investigate whether RF strain injury affected the region-specific functional role of the muscle. We studied seven soccer players with a history of unilateral RF strain injury. Injury data were obtained from a questionnaire survey and magnetic resonance imaging (MRI). Multichannel surface electromyographic (SEMG) signals were recorded from the proximal to distal regions of the RF with 24 electrodes during isometric knee extension and hip flexion. The SEMG signals of each channel during hip flexion were normalised by those during knee extension for the injured and non-injured RF (HF/KE), and compared among the proximal, middle, and distal regions. Six RF strain injuries showed a low signal area in MRI. There was no significant difference in muscle strength between the injured and non-injured RF. While the HF/KE in the proximal region was significantly higher than those in the middle and distal regions in the non-injured RF, a difference in the HF/KE was seen only between the proximal and distal regions of the injured RF. Furthermore, the HF/KE of the most proximal channel in the injured RF was significantly lower than that in the non-injured RF. However, there was no significant difference between injured and non-injured areas in the HF/KE. Our findings suggest that the region-specific functional role of the RF muscle is partly affected by RF strain injury.

Cervical Intervertebral Disc Degeneration and Low Cervical Extension Independently Associated With a History of Stinger Syndrome.
Takayoshi Hakkaku; Koichi Nakazato; Koji Koyama; Karina Kouzaki; Kenji Hiranuma
Orthopaedic journal of sports medicine, Nov. 2017
BACKGROUND: Stinger syndrome frequently occurs in athletes who compete in collision sports. Sharp pain and impairment of neck motion are major symptoms. Cervical intervertebral disc degeneration (CIDD) is also frequently observed in those who compete in collision sports. PURPOSE/HYPOTHESIS: To investigate whether CIDD and neck functionality are related to a history of stinger syndrome. The hypothesis was that a significant relationship exists between CIDD and neck motion and a history of stinger syndrome in Japanese collegiate football players. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: A total of 49 male Japanese collegiate football players (mean age, 20.0 ± 1.1 years; mean athletic experience, 3.8 ± 2.3 years; mean height, 172.3 ± 4.8 cm; mean weight, 83.1 ± 12.2 kg) were subdivided into athletes with stinger syndrome (stinger group) and those without (control group). Stinger syndrome was confirmed based on a questionnaire and interview. CIDD was assessed by using T2-weighted magnetic resonance imaging. Range of motion (ROM) and isometric muscle strength were measured for neck function testing. RESULTS: Thirty-nine percent (19/49) of athletes had at least 1 episode of stinger syndrome. The prevalence of CIDD was significantly higher in the stinger group (68%) than in the control group (30%) (P < .01). A statistically significant difference in cervical extension ROM was found between the stinger group (50.9° ± 11.1°) and the control group (60.2° ± 11.4°) (P < .01). Logistic regression analysis showed that CIDD and low cervical extension were independently associated with a history of stinger syndrome. CONCLUSION: Study results suggest that stinger syndrome is associated with CIDD and low cervical extension in collegiate football players.

The Relation Between Lumbar Disc Degeneration And Physical Characteristics In Male Asian Collegiate Basketball Players
Im Kyong-ae; Nakazato Koichi; Koyama Koji; Fujita Masahiro; Kotani Kiwamu; Hakkaku Takayoshi; Hiranuma Kenji
MEDICINE AND SCIENCE IN SPORTS AND EXERCISE, May 2016

A study on differences in core muscle reaction time and rate of force development among university male judokas, across weight classes
下和田翔平; 菅原幸大; 鈴木広大; 小菅亨; 八角卓克; 岡田隆
運動とスポーツの科学, 2025

スポーツ現場・臨床で使える!トレーニングやエクササイズのための器具と機器 スポーツ現場,臨床で有用なトレーニング・エクササイズ器具 中等度から高負荷の筋力・パワートレーニングに有用な器具
2024

スポーツ医学に関する研究 ボディビル大会前後の生理学的指標の変化
2024

大学アメリカンフットボール選手における腰椎椎間板変性と筋横断面積の関連性
2022

ウェイトリフティング選手の競技パフォーマンスおよびパワー発揮特性における性差について
2018

ストレングストレーニングにおける強度設定とトレーニング効果の性差に関する研究
2018

ウェイトリフティング選手の競技パフォーマンスおよびパワー発揮特性における性差について
2018

ストレングストレーニングにおける強度設定とトレーニング効果の性差に関する研究
2018

男子大学ラグビー選手における下腿運動誘発性筋痙攣発生頻度と身体特性との関連の検討
2016

健常大学生における神経伝導速度とTensiomyographyの関連性について
2015

大学アメリカンフットボール選手におけるバーナー症候群既往と頚部筋力および頚部可動域の関連性について
2015

日体大教授が教える運動0でお腹が凹む!「脂肪燃焼」食堂
Jun. 2026
9784065439258