Understanding the properties associated with the vertical force–velocity (F–v) profiles is important for maximizing jump performance. The purpose of this study was to evaluate the associations of maximum and reactive strength indicators with the F–v profiles obtained from squat jump (SJ) and countermovement jump (CMJ). On the first day, 20 resistance-trained men underwent measurements for half squat (HSQ) one-repetition maximum (1RM). On the second day, jump performances were measured to calculate the drop jump (DJ) reactive strength index (RSI) and the parameters of F–v profiles (theoretical maximum force [F0], velocity [V0], power [Pmax], and slope of the linear F–v relationship [SFv]) obtained from SJ and CMJ. The DJ RSI was not significantly correlated with any parameter of the vertical F–v profiles, whereas the relative HSQ 1RM was significantly correlated with the SJ F0 (r = 0.508, p = 0.022), CMJ F0 (r = 0.499, p = 0.025), SJ SFv (r = −0.457, p = 0.043), and CMJ Pmax (r = 0.493, p = 0.027). These results suggest that maximum strength is a more important indicator than reactive strength in improving vertical F–v profiles. Furthermore, the importance of maximum strength may vary depending on whether the practitioner wants to maximize the performance of SJ or CMJ.

BACKGROUND: The rating of perceived exertion (RPE) is correlated with physiological variables. The purpose of this study was to assess the validity of using the Borg CR-10 scale and velocity to predict muscle fatigue assessed by surface electromyography during single joint resistance exercises. METHODS: Fifteen healthy males underwent different fatigue levels of unilateral elbow flexion (EF) and knee extension (KE), consisting of low, medium, and high volumes at 65% of their one-repetition maximum. The RPEs, spectral fatigue index (SFI), and mean velocity of the experimental exercises were assessed throughout the trials. RESULTS: Significant differences in overall RPE (p < 0.001) and average SFI (p < 0.001) were observed between the conditions in both exercises. Significant changes in RPE and SFI (p < 0.001) were observed throughout the EF, whereas a SFI increase (p < 0.001) was only observed at the end point of KE. Multiple regression analyses revealed two significant models (p < 0.001) for the prediction of muscle fatigue during EF (R2 = 0.552) and KE (R2 = 0.377). CONCLUSIONS: Muscle fatigue resulted in similar increases in perceptual responses, demonstrating that RPE is useful for assessing fatigue when resistance exercise is performed. However, velocity changes may not reflect muscle fatigue correctly when exercise is no longer performed in an explosive manner. We recommend combining RPE responses with velocity changes to comprehensively assess muscle fatigue during clinical and sports situations.

We aimed to compare the urinary titin N-terminal fragment (UTF) concentration after concentric and eccentric exercise and to clarify the specific response of UTF to exercise-induced muscle damage (EIMD). Nine healthy young men performed 30 concentric elbow flexion exercises with maximum effort, rested for at least eight weeks, and performed eccentric exercises at the same workload using the same arm. Changes in the maximal voluntary isometric contraction (MVIC), muscle soreness (SOR), range of motion (ROM), serum creatine kinase (CK) activity, and UTF concentrations were recorded before and after for six consecutive days after exercise. There was no significant difference in workload during exercise between the two exercise types. However, serum CK activity increased after eccentric exercise (p < 0.05). Additionally, MVIC, SOR, ROM, and UTF concentration were significantly higher after eccentric exercise than after concentric exercise (p < 0.05). Although workload was the same, the UTF concentration greatly increased after eccentric exercise. Based on these results, we suggest that UTF can be a non-invasive and highly specific biomarker of EIMD.

BACKGROUND: Agonist-antagonist muscle superset (SS) and paired-set (PS) strength training protocols enable the completion of training activities within a shorter period of time than traditional set. The purpose of this study was to investigate the effects of PS and SS through total volume (TV), set volume (SV), blood lactate concentration (LAC), rating of perceived exertion (RPE), and neuromuscular fatigue index (FInsm5). METHODS: Eleven males who train recreationally performed PS and SS consisting of bent-over row (BOR) and bench press (BP). In performing the PS, a single bout of BOR was followed by a rest interval of 60 seconds, the BP was then performed and followed by another rest interval of 60 seconds. When the SS was performed, a single bout of BOR and a single bout of BP were performed consecutively and followed by a single rest interval of 120 seconds. The exercise configurations were repeated until five sets were completed. The TV was calculated by multiplying the number of successful repetitions and the load. The LAC and RPE were measured at predetermined times. Electromyographic signals were recorded for use in the FInsm5 calculation. RESULTS: The RPE indicated that PS was significantly lower than SS (P<0.01). No significant differences between PS and SS were discovered in SV, TV, LAC, and FInsm5. CONCLUSIONS: This study demonstrates that PS has lower perceived exertion than SS when agonist-antagonist strength training protocols are selected as the training structure.

Purpose: The optimal load for maximal power output during hang power cleans (HPCs) from a mechanical perspective is the 1-repetition-maximum (1RM) load: however, previous research has reported otherwise. The present study thus aimed to investigate the underlying factors that determine optimal load during HPCs. Methods: Eight competitive Olympic weight lifters performed HPCs at 40%, 60%, 70%, 80%, 90%, 95%, and 100% of their 1RM while the ground-reaction force and bar/body kinematics were simultaneously recorded. The success criterion during HPC was set above parallel squat at the receiving position. Results: Both peak power and relative peak power were maximized at 80% 1RM (3975.7 [439.1] W, 50.4 [6.6] W/kg, respectively). Peak force, force at peak power, and relative values tended to increase with heavier loads (P < .001), while peak system velocity and system velocity at peak power decreased significantly above 80% 1RM (P= .005 and .011, respectively). There were also significant decreases in peak bar velocity (P < .001) and bar displacement (P < .001) toward heavier loads. There was a strong positive correlation between peak bar velocity and bar displacement in 7 of 8 subjects (r> .90, P < .01). The knee joint angle at the receiving position fell below the quarter-squat position above 70% 1RM. Conclusions: Submaximal loads were indeed optimal for maximal power output for HPC when the success criterion was set above the parallel-squat position. However, when the success criterion was defined as the quarter-squat position, the optimal load became the 1RM load.

BACKGROUND: Although the transversus abdominis (TrA) is considered to play a significant role in maintaining trunk stability, there is little information regarding the type of exercise that best facilitates the development of tension in the TrA. Muscle elasticity shows a strong association with muscle tension. Shear wave ultrasound elastography provides a means by which the tension of TrA can be noninvasively estimated, by quantifying it's elasticity. PURPOSE: The purpose of this study was to examine the TrA elasticity during several exercises as measured by shear wave ultrasound elastography, and to determine which of the studied exercises demonstrated the greatest tension. METHODS: Ten healthy men performed abdominal hollowing, abdominal bracing, a hanging deadlift, elbow-toe plank with contralateral arm and leg lift, and back bridge with single leg lift. During these exercises, TrA elasticity was measured using ultrasound elastography. The same measurements were performed at rest before and after these exercises. RESULT: No significant difference was found for rest conditions measured before and after the exercises (p = 0.63). Abdominal bracing showed a significantly higher elasticity value than the other exercises (p < 0.05), except for hanging deadlift. CONCLUSION: Among the exercises, abdominal bracing was the exercise that elevated the TrA tension the most. The present results also suggested that hanging deadlift also produced comparably high TrA tension with abdominal bracing. LEVEL OF EVIDENCE: 2c.

Athletes who aim to improve both muscular endurance and power often perform exercises that involve similar joint actions under different lifting conditions, such as changes in the load or speed, which are implemented at different times during a periodized exercise program or simultaneously. The prescribed exercises are considered to recruit the same muscles even if the lifting conditions differ to each other. The present study aimed to clarify this by examining whether the recruitment of individual hip and knee muscles during the squat exercise differs between lifting conditions adopted for muscular endurance and power training regimens. Moderately trained men performed back squats (BS), with a load of approximately 60% of one repetition maximum, as a muscular endurance training exercise, and they performed plyometric squat jumping (PSJ) for power training. During each exercise, the lower limb joint torques and the recruitment of five hip and knee muscles were determined with inverse-dynamics and T2-weighted magnetic resonance imaging, respectively. While the maximal and mean knee joint torques were greater during PSJ than during BS (p&lt;0.01), the T2 values for the quadriceps femoris muscle did not differ between the exercises. In contrast, the T2 values of the gluteus maximus and hip adductor muscles were higher during PSJ (p&lt;0.05) than during BS, although there was no significant difference in the mean hip extension torque between the two exercises. The current results indicate that the individual use of the agonist muscles differs between BS and PSJ, and it does not always correspond with the joint kinetics during the exercises. Therefore, in addition to the exercise type, the lifting condition should also be taken into consideration as a determinant of the major muscles trained during a resistance exercise.

The present study aimed to quantify the intensity of lower extremity plyometric exercises by determining joint mechanical output. Ten men (age, 27.3 +/- 4.1 years; height, 173.6 +/- 5.4cm; weight, 69.4 +/- 6.0kg; 1-repetition maximum [1RM] load in back squat 118.5 +/- 12.0kg) performed the following seven plyometric exercises: two-foot ankle hop, repeated squat jump, double-leg hop, depth jumps from 30 and 60cm, and single-leg and double-leg tuck jumps. Mechanical output variables (torque, angular impulse, power, and work) at the lower limb joints were determined using inverse-dynamics analysis. For all measured variables, ANOVA revealed significant main effects of exercise type for all joints (P&lt;0.05) along with significant interactions between joint and exercise (P&lt;0.01), indicating that the influence of exercise type on mechanical output varied among joints. Paired comparisons revealed that there were marked differences in mechanical output at the ankle and hip joints; most of the variables at the ankle joint were greatest for two-foot ankle hop and tuck jumps, while most hip joint variables were greatest for repeated squat jump or double-leg hop. The present results indicate the necessity for determining mechanical output for each joint when evaluating the intensity of plyometric exercises.

:The present study aimed to quantify the intensity of lower extremity plyometric exercises by determining joint mechanical output. Ten men (age, 27.3 ± 4.1 years; height, 173.6 ± 5.4 cm; weight, 69.4 ± 6.0 kg; 1-repetition maximum [1RM] load in back squat 118.5 ± 12.0 kg) performed the following seven plyometric exercises: two-foot ankle hop, repeated squat jump, double-leg hop, depth jumps from 30 and 60 cm, and single-leg and double-leg tuck jumps. Mechanical output variables (torque, angular impulse, power, and work) at the lower limb joints were determined using inverse-dynamics analysis. For all measured variables, ANOVA revealed significant main effects of exercise type for all joints (P < 0.05) along with significant interactions between joint and exercise (P < 0.01), indicating that the influence of exercise type on mechanical output varied among joints. Paired comparisons revealed that there were marked differences in mechanical output at the ankle and hip joints; most of the variables at the ankle joint were greatest for two-foot ankle hop and tuck jumps, while most hip joint variables were greatest for repeated squat jump or double-leg hop. The present results indicate the necessity for determining mechanical output for each joint when evaluating the intensity of plyometric exercises.

This study aimed to investigate the differences in the development of muscle thickness (MT) in the lower limbs with specific sports-event training. Furthermore, the relationship between MT of the lower limbs for weightlifters and sprinters and their competition performances (total weight lifted and 100m sprint times) was examined. Subjects were 64 males divided into 3 groups: weightlifters (n=20), sprinters (n=20), and untrained subjects as controls (n=24). The MT {relative to (body weight)(1/3)} of knee extensors (KE), knee flexors (KF), plantar flexors (PF) and dorsi flexors (DF) was measured at 21 sites (proximal, middle and distal) along the length of the upper and lower leg by B-mode ultrasound. The MT of KE for weightlifters was significantly greater than that for sprinters and controls, while the MT of KF and PF for sprinters was significantly greater than that for weightlifters and controls. The MT of rectus femoris (RF), vastus intermedius (VI), vastus lateralis (VL) and vastus medialis (VM) for weightlifters was significantly greater than that for sprinters and controls, while the MT of RF and VM for sprinters was greater than that of controls. On the other hand, the MT of KE for weightlifters and sprinters (especially VM) correlated significantly with competition performances. These results indicated that squatting affected the MT of KE except for RF while sprinting affected the MT of KF and PF. It was also concluded that the MT of KE for weightlifters and sprinters (particularly VM) was related to their competition performances. (Jpn. J. Phys. Fitness Sports Med., 60(4) : 401 similar to 411 (2011))

This study aimed to investigate the differences in the development of muscle thickness (MT) in the lower limbs with specific sports-event training. Furthermore, the relationship between MT of the lower limbs for weightlifters and sprinters and their competition performances (total weight lifted and 100m sprint times) was examined. Subjects were 64 males divided into 3 groups: weightlifters (n=20), sprinters (n=20), and untrained subjects as controls (n=24). The MT{relative to (body weight)1/3}of knee extensors (KE), knee flexors (KF), plantar flexors (PF) and dorsi flexors (DF) was measured at 21 sites (proximal, middle and distal) along the length of the upper and lower leg by B-mode ultrasound. The MT of KE for weightlifters was significantly greater than that for sprinters and controls, while the MT of KF and PF for sprinters was significantly greater than that for weightlifters and controls. The MT of rectus femoris (RF), vastus intermedius (VI), vastus lateralis (VL) and vastus medialis (VM) for weightlifters was significantly greater than that for sprinters and controls, while the MT of RF and VM for sprinters was greater than that of controls. On the other hand, the MT of KE for weightlifters and sprinters (especially VM) correlated significantly with competition performances. These results indicated that squatting affected the MT of KE except for RF while sprinting affected the MT of KF and PF. It was also concluded that the MT of KE for weightlifters and sprinters (particularly VM) was related to their competition performances.

The purpose of this study was to investigate sex differences in the muscle volume (MV) of the iliopsoas, psoas major, and iliacus muscles, normalized by fat free mass (FFM), in the elderly. The subjects were 15 males and 15 females 65 years of age or over. Serial transverse 1.5T magnetic images (10mm slice) of each subject were taken between the 12^<th> thoracic vertebrae and the lesser trochanter. FFM was measured with a bioelectrical impedance analyzer. The mean MV of each muscle on the right and left sides were calculated and used for regression analysis of the relationship between MV and FFM. A significant correlation was observed between MV and FFM of the iliacus in both sexes (p<0.01), but not between the MV and FFM of the psoas major. MV normalized by FFM and cross-sectional area (CSA) normalized by FFM^<2/3> showed significantly greater values for the psoas major in the males than in the females (p<0.001), but there was no sex difference in the MV or CSA normalized by FFM of the iliacus. These results suggest that elderly males tend to have a greater muscle volume and cross-sectional area of the iliopsoas than elderly females, and that these sex differences are attributable to differences in the psoas major.

The purpose of the present study was to compare the snatch techniques of Japanese and international female weightlifters using kinematic analysis. Motion analysis of the snatch techniques conducted using videos recorded at the 2006 Women's Junior World Weightlifting Championship. The results indicated no significant differences between the snatch techniques of Japanese and international weightlifters in terms of the kinematic parameters expressed by the barbell trajectory and joint angles. However, the interval of time between the peak velocity of the hip joint and peak vertical velocity of the barbell was longer for Japanese weightlifters, while the power applied to the barbell was 35% greater for international weightlifters. These findings indicate that differences in strength and power production affected the performances of Japanese and international weightlifters.

The stages of change (Precontemplation, Contemplation, Preparation, Action, and Maintenance) are a key concept of the transtheoretical model. The present study, designed as a cross-sectional study using an Internet questionnaire, was intended to identify characteristics of stages of change for strength training behavior and to examine the relationship between them and self-efficacy for strength training behavior. Measured variables included stages of change for strength training behavior, moderate-vigorous physical activity, type of strength training, self-efficacy for strength training behavior, and socio-demographic variables. Subjects (5,177 Japanese adults; 40.1±12.0 years; recruited from registrants of a social research company) were in the following stages: 39.5% in Precontemplation; 25.1% in Contemplation; 21.0% in Preparation; 5.6% in Action; and 8.8% in Maintenance. The most common types of strength training activities were done at home (74.3%), used the subject's own body weight (60.4%), and were done in the subject's own way (85.1%). ANCOVA results showed a significant association between stages of change and moderate-vigorous physical activity. Subjects who were women, older, unemployed, with lower education levels, or with lower income significantly tended to be classified into the two earlier stages with the χ² and Kruskal-Wallis tests. In multiple logistic regression analysis, self-efficacy predicted stages of change. Approaches to promote strength training such as enhancement of self-efficacy targeting those who were in earlier stages (e.g. older women) would be needed.

To compare the effectiveness of five different muscle training movements on the biceps brachii, latissimus dorsi and trapezius muscles, eight weight-trained men (age, 20.4±0.5 years) were asked to perform three repetitions, at 70% one repetition maximum, of upright rowing (UR) and bent-over rowing (BR) exercises using a barbell ; and seated rowing (SR), front lat pulldown (LPf) and back lat pull-down (LPb) exercises using a Universal Machine. The activities of the biceps brachii, latissimus dorsi, and trapezius during the elbow flexsion and elbow extension phases of each exercise were analyzed using integrated electromyography (EMG) and normalized I-EMG. The results were as follows : 1. The mean nrmsEMG values for the biceps brachii were larger during UR and LPf exercises than during BR, SR, and LPb exercises, suggesting that UR and LPf are more effective than the other movements for training the biceps brachii. The mean nrmsEMG values for the latissimus dorsi were larger during SR, LPf, and LPb exercises, followed by BR and UR exercises (in descending order), suggesting that SR, LPf, and LPb exercises are more effective than the other movements for training the latissimus dorsi. 2. The mean nrmsEMG values for the upper trapezius were larger during UR and BR exercises than during SR, LPf, and LPb exercises, suggesting that UR and BR exercises are more effective than the other movements for training the upper trapezius. The mean nrmsEMG values for the middle trapezius were larger during BR and SR exercises than during UR, LPf, and LPb exercises, suggesting that BR and SR exercises are more effective than the other movements for training the middle trapezius. The mean nrmsEMG values for the lower trapezius were larger during BR exercise than during other movements, suggesting that BR exercise is more effective than the other movements for training the lower trapezius. 3. In all the exercises, each muscle showed a higher nrmsEMG value during the elbow flexsion phase than during the elbow extension phase. This observation suggests that the training method examined in this study should emphasize the elbow flexsion movement. The present results suggest that UR exercise is the most effective movement for training the biceps brachii and upper trapezius, BR is most effective for training the upper trapezius, middle trapezius and lower trapezius, SR is most effective for training the latissimus dorsi and middle trapezius, LPf is most effective for training the biceps brachii and latissimus dorsi, and LPb is most effective for training the latissimus dorsi.

本研究は足関節における反動動作による弾性エネルギーの貢献度と機械的仕事量およびパワー増強との関係を明らかにすることを目的とした. 被検者 (7名) はスレッジ装置上で以下の3条件で足関節のみを使用した跳躍を行った: (1) 反動なしの底屈 (PFJ), (2) 反動動作を伴う底屈 (CMJ) および (3) ドロップジャンプ (DJ). CMJおよびDJにおいて, すべての被検者で足関節の機械的仕事量およびパワーは増加した. 底屈局面の機械的仕事量に対する弾性エネルギーの貢献度はCMJで39.7%, DJで71.7%であり, 両試行とも底屈局面の機械的仕事量およびパワーの増加率と弾性エネルギーの貢献度の間に相関関係が認められた. これらの結果は, 1) 足関節の反動動作では弾性エネルギーが関節の機械的仕事量に大きな貢献を果たすこと, 2) 反動動作では機械的仕事量やパワー増強の大きさは弾性エネルギーの大きさに依存することを示唆する.

The purpose of this study was to compare the effects of resistance training with counter movement (stretch shortening cycle) or without counter movement (normal style) in elbow flexion. We also attempted to identify the effect of elbow flexors on force development, cross sectional area and volume. Six subjects performed dumbbell curls using their elbow flexor muscles with either theright or left arm for both modes according to random assignment. Training (60% of one repetition maximum × 10 repetitions × 5 sets) was performed 3 days per week for 6 weeks. Maximum force and maximum rate of force development were determined during static and dynamic elbow flexion tests before and after the training period using a special arm ergometer. In addition, muscle volume of elbow flexors (biceps brachii and brachialis muscle) were estimated from magnetic resonance images. Maximum force in the static condition at elbow flexion of 2.09 radians was significantly increased only for stretch-shortening cycle training (from 245±41 to 292±40N, p<0.05). Maximum force and maximum rate of force development during dynamic tests at most loads (2-9kg) were significantly increased (10-15%) for stretch-shortening cycle training. No significant changes were observed in these values for normal style training during the dynamic elbow flexion test. On the other hand, muscle volume was increased only for normal style training (from 269±43 to 30±54cm^3, p<0.05). These results indicated that stretch-shortening cycle training was more effective for dynamic force production than conventional isotonic trauning and that it can be considered a specific mode of training.

The purpose of this study was to describe the kinematic characteristics of the snatch technique from the viewpoint of barbell trajectory. Subjects included 6 elite male Asian weight lifters who participated in the first Japan International Friendship Tournament in 1993. Trajectories of the barbell during snatch lifts in the competition were videotaped. Three vertical acceleration peaks of the barbell during the pull movement were observed and corresponded to the first pull, transition, and second pull phases. The angle of the resultant acceleration (ARA) of the barbell averaged 85 degrees in the first pull and transition pull phases. In the second pull phase. the ARA was almost 140 degrees, indicating that the barbell was accelerated anteriorly, away from the lifter. The results of this study suggest that during the first pull and transition pull phases, elite lifters pulled the barbell toward themselves to produce the needed vertical acceleration and that the resulting posterior movement of the barbell was controlled by the forward acceleration produced in the second pull phase.

The purpose of this study was to describe the kinematic characteristics of the snatch technique from the viewpoint of barbell trajectory. Subjects included 6 elite male Asian weight lifters who participated in the first Japan International Friendship Tournament in 1993. Trajectories of the barbell during snatch lifts in the competition were videotaped. Three vertical acceleration peaks of the barbell during the pull movement were observed and corresponded to the first pull, transition, and second pull phases. The angle of the resultant acceleration (ARA) of the barbell averaged 85 degrees in the first pull and transition pull phases. In the second pull phase. the ARA was almost 140 degrees, indicating that the barbell was accelerated anteriorly, away from the lifter. The results of this study suggest that during the first pull and transition pull phases, elite lifters pulled the barbell toward themselves to produce the needed vertical acceleration and that the resulting posterior movement of the barbell was controlled by the forward acceleration produced in the second pull phase.