Acute effect of static stretching on passive and active properties of the gastrocnemius muscle–tendon unit: an investigation based on different repetition durations and numbers / 体力科学

<p>Many previous studies have reported that static stretching (SS) may decrease muscle stiffness and compromise muscles’ ability to produce maximal strength. However, the effects of SS at different repetition durations and numbers within a constant total time remain unclear. Therefore, the purpose of this study was to examine whether SS for a constant total time (2 min) with different repetition durations and numbers (e.g., 60 s × 2 times, 30 s × 4 times, and 10 s × 12 times) produces different changes in muscle stiffness and strength. Fifteen healthy males (mean age: 23.3 ± 1.0 years) participated in this study. Muscle stiffness was measured during passive ankle dorsiflexion using dynamometer and ultrasonography. In addition, muscle strength of the plantar flexors was measured using a dynamometer at 0° of plantarflexion with the hip and knee joints fully extended. Muscle stiffness and strength were measured before and immediately after SS. Each experimental protocol was conducted in random order with at least a 1-week interval but no longer than a 2-week interval between testing sessions. The results showed that there were no significant interaction effects on muscle stiffness and strength. However, in all experimental protocols, muscle stiffness and strength immediately decreased after SS. In conclusion, SS for a constant total of 2 min decreases muscle stiffness and strength regardless of repetition durations and numbers of each individual SS.</p>

CHANGE IN MUSCLE THICKNESS OF THE REGIONS OF TRANSVERSUS ABDOMINIS BY ULTRASOUND IMAGING / 体力科学

This study investigated the changes in muscle thickness of transversus abdominis (TrA) during trunk muscle training. The subjects comprised 30 young men (average age 20.1 SD1.6 years) without low back pain. The muscle thickness of the upper region of TrA, middle region of TrA and lower region of TrA were measured by B-mode ultrasound. Muscle thickness were measured at rest and during the following 5 exercises; abdominal drawing, curl up, trunk ipsilateral rotation, trunk contralateral rotation and both straight leg raise in supine. There were no significant differences in the muscle thickness of the upper region of TrA between resting condition and all exercises. Muscle thickness during drawing, curl up and ipsilateral rotation were significantly greater than that at rest in middle region of TrA, and the rate of change in muscle thickness was the largest for drawing. Muscle thickness during drawing, curl up and ipsilateral rotation were significantly greater than that at rest in the lower region of TrA, and the rate of change in muscle thickness was the largest for ipsilateral rotation. These results suggested that the changes in muscle thickness of TrA during trunk muscle training showed different patterns depending on the region of TrA.

PHYSICAL FUNCTION SCREENING OF INSTITUTIONALIZED ELDERLY WOMEN TO PREDICT THEIR RISK OF FALLING / 体力科学

This study examined the relationship between multiple physical function and falls among institutionalized elderly women, and screening methods designed to effectively identify elderly with a high risk of falling. The subjects comprised 44 elderly women aged 82±6 years residing in a nursing home. Multiple physical assessments were tested using the following measures; muscle strength(quadriceps strength and grip strength), balance test(functional reach and one-legged stance test), flexibility test(sit and reach test), agility test(stepping test), and physical performance test(TUG and chair stand test). Based on the experience of fall-related accidents within the past two years, we categorized the subjects into two groups (non-fall group and fall group). Of these measures, quadriceps strength, grip strength, functional reach, stepping test in a standing position, and chair stand test were significant factors discriminating whether the subject had a history of falls. Logistic regression analysis demonstrated that quadriceps strength, functional reach, stepping test in a standing position, and chair stand test were important predictors of falls in an institutionalized elderly population. The results of this study suggest that 0.84 Nm/kg for quadriceps strength, 26 cm for functional reach, 17 steps for stepping test, and 14 sec for chair stand test, were useful indicators for screening institutionalized elderly for risk of falling. Particularly, the stepping test was most effective in screening the elderly to assess their fall risk.