Static stretching (SS) is widely used to decrease and retain the passive stiffness of the muscle-tendon unit in clinical and athletic settings. It is important to consider the minimum SS duration required to decrease the passive stiffness of the hamstring, from the perspective of injury prevention of the hamstring muscle. The purpose of this study was to investigate the time course of the effect of static stretching (SS) on passive stiffness of the hamstring and to clarify the minimum SS duration required to decrease the passive stiffness. Fifteen healthy males participated in this study. Fifteen healthy and non-athlete male volunteers participated in this study. SS of 60-s session was performed for five sessions with a 30-s rest between sessions. Passive stiffness was measured prior to SS (PRE) and immediately after each SS session to determine the minimum SS duration required to decrease the passive stiffness. The passive stiffness was calculated as the slope of the torque-angle curve corresponding to 50% of the final angle (Nm/°). Passive stiffness after 180, 240, and 300 s of SS was significantly lower than that at PRE. Our results showed that SS for >180 s is recommended to decrease the passive stiffness of the hamstring muscle.
Low birth weight has been reported as a risk factor for non-communicable diseases, which can be caused by metabolic dysfunction. Here, we conducted a retrospective study to define the correlation between birth weight and present physical characteristics/fitness in Japanese university students, by gender. The subjects were from among 1,333 healthy university students. They carried out a self-administered questionnaire on birth weight, physical characteristics, and exercise habits, and 8 types of physical fitness tests. We excluded data from subjects that lacked information in their questionnaire and those who were not a full-term single birth. Finally, data of 378 participants (28.4% of all subjects, 116 males and 262 females) were analyzed. We categorized the participants into lower and higher birth weight groups, based on the overall median value calculated for birth weight. The lower birth weight group of males demonstrated lower grip strength; however, there was no significant association after adjustment for height, weight, and exercise habits. The lower birth weight group of females showed higher scores on the 50-meter running test even after the adjustment for physical characteristics and exercise habits. These results suggest that lower birth weight males had a lower grip strength, which was strongly associated with their physical size. In contrast, higher sprint performance was shown to be independent of physical size in lower birth weight females.
We investigated the relationship between basketball free-throw accuracy and anthropometry, physical fitness tests, and performance variables among 16 collegiate female basketball players. Each participant performed 20 basketball free throws. Anthropometric measures were height and weight; physical fitness tests were sit-and-reach, back strength, and grip strengths; other basketball performance variables were the phases of the pre-shoot routine: (a) time taken, (b) minimum angle when taking the ball back, (c) angle at ball release, (d) angular displacement during the forward arm swing, and (e) angular velocity at ball release on the elbow, shoulder, hip, knee, and ankle. We analyzed the correlation between free-throw accuracy and data on anthropometry and physical fitness, the time period and variability of the pre-shot routine, and kinematic data. There were negative correlations between free-throw accuracy and mean pre-shot time, and variability of the pre-shot time, indicating that participants with a shorter and less variable pre-shot time showed a higher free-throw accuracy. Angular displacement of the shoulder during the forward swing and angular velocity of the knee at ball release showed positive correlations with free-throw accuracy. There was also a negative correlation between free-throw accuracy and variability of angular displacement during the forward swing at the elbow, indicating that participants with smaller variability of angular displacement of the elbow showed higher free-throw accuracy. Some performance variables, including routine duration, angular displacement of the shoulder and elbow, and angular velocity of the knee, were related to free-throw accuracy.
This study examined the effects of different dynamic stretching (DS) amplitudes on joint range of motion (ROM), passive torque (PT), and subjective fatigue. Twelve healthy subjects (age [mean ± SD] = 19.3 ± 1.0 years) underwent three experimental trials: DS at maximal active ankle plantarflexion-dorsiflexion ROM (DS100), DS at 80% maximal active ROM (DS80), or control. Ankle angle and PT were measured before and after DS with the ankle passively dorsiflexed at 1º/s to its maximal ROM. DS consisted of four sets of 30 s of ankle plantarflexion-dorsiflexion at 100 beats/min while standing. Subjective fatigue during DS was measured using the visual-analogue scale. Maximal ankle dorsiflexion angle was significantly increased after DS100 (20.6 ± 3.5º to 23.8 ± 3.8º, P < 0.05); no changes were seen after DS80/control. Subjective fatigue was significantly greater at two (2.6 ± 0.7 mm vs 1.2 ± 0.3 mm), three (3.7 ± 0.9 mm vs 1.3 ± 0.3 mm), and four (5.2 ± 0.9 mm vs 1.6 ± 0.3 mm) sets of DS100 than with DS80 (P < 0.05). PT at maximal dorsiflexion increased from before to after stretching (DS100: 26.3 ± 3.2 Nm to 30.4 ± 3.4 Nm, DS80: 28.8 ± 3.0 Nm to 31.0 ± 3.3 Nm, Control: 26.6 ± 2.8 Nm to 29.1 ± 3.5 Nm, P < 0.05), although there were no significant differences among trials. These results indicated that greater active ROM during DS is important for increasing joint ROM, although DS with greater active ROM induces greater subjective fatigue.
This article published in J Phys Fitness Sports Med, 6 (2): 95-102 (2017) has been retracted at the request of the authors because body composition data using dual-energy X-ray absorptiometry was obtained by an uncertified technician. Japanese Society of Physical Fitness and Sports Medicine Journal of Physical Fitness and Sports Medicine Editor-in-Chief Katsumasa Goto