Ankle Plantar and Dorsal Flexor Muscles Strength in Healthy Young Adults / 中国运动医学杂志

The purposes of this study were: (1) to test healthy young adults' ankle plantar and dorsal flexor muscles strength, providing integrate data and scientific basis for sports training, sports injury and recovery. (2) to investigate the biomechanical rule of healthy adults' ankle plantar and dorsal flexor muscles. Methods: 70 college students (35males and 35 females) volunteerily took part in the test. An advanced Cybex-6000 dynamometer was employed. This test consisted of two sections, isokinetic concentric (CON) test and isometric test. Results: males and females adults' ankle dorsal flexor isometric peak torque (PT) increased and plantar flexor isometric PT decreased with the increasing of testing angle. CON PT decreased while the test angle velocities increased. Plantar flexor PT were higher than corresponding dorsal flexor in two tests ( P

Effects of ramp and ballistic contractions on post-exercise hyperemia in human triceps surae / 体力科学

This study was designed to compare post-exercise hyperemia between ramp and ballistic contractions in human triceps surae. Subject was asked to extend ankle joint in range of 20 degrees for 1 sec and with maximum effort against loads of 10, 20, 30 or 40% of maximum voluntary contraction (MVC) in ankle extensors. Amount of post-exercise hyperemia was calculated from changes in calf girth recorded by using two strands mercury-in-rubber gauge.<BR>1) Calf girth after contractions transiently decreased below precontraction level and increased gradually until its peak value, over precontraction level, in about 8 sec. Calf girth recovered to resting level for about 30 sec.<BR>2) After ramp contractions, amount of decrease of calf volume increased in order to loads of 10, 20, 30 and 40% MVC, but was not so after ballistic contractions. Amount of its increase, excess precontraction level, depended on loads in both conditions. These values were below 1.0m<I>l</I>/100 m<I>l</I> tissue.<BR>3) Amount of decrease of calf volume after ramp contraction was larger than that of ballistic contraction, but amount of its increase was inverse.<BR>4) There was significant coefficient between calf volume increase after contraction and maximum inflow rate (m<I>l</I>/min/100 m<I>l</I> tissue) calculated from the maximum gradient in rising phase of calf girth (r=0.5508, p<0.001) .<BR>From these results, it is suggested that“milking action”in muscle generate with ramp contraction, and that disturbance of pulsatile inflow to muscle and chemical and neuronal regulations to generate post-exercise hyperemia pronouncely act by ballistic contraction.

Changes of calf girth during ballistic contraction in human ankle extensors / 体力科学

Muscle activity of human ankle extensors during ballistic plantar flexion movement was studied by use of the rubber-strain-gauge method. The muscle power was measured by using the after-loading method. The subjects quickly extended the ankle joint with loads of 20, 40 and 60% of the maximum voluntary contraction (MVC) of ankle extensor muscles.<BR>Maximum muscle power was exerted at about the load of 60% MVC. This result can presumably be attributed to the increase in the recruitment and firing frequency of motor units in gastrocnemius muscle with each load attached to ankle extensors.<BR>Although the amount of muscle power increased consistently with an increase in the calf girth immediately after an onset of load lifting (r=0.8479, p<0.001), the period in which it obtained maximum velocity was not significant. On the other hand, muscle activity immediately after onsets of load lifing are important and girth changes in muscle should be considered as parameter for estimating the power output of human muscles during ballitic contraction.