All issues
Volume 28 (1979)
- Issue 4 Pages 299-
- Issue 3 Pages 239-
- Issue 2 Pages 81-
- Issue 1 Pages 1-
Volume 28, Issue 2
Displaying 1-6 of 6 articles from this issue
- |<
- <
- 1
- >
- >|
-
AKIRA NAGATA, MASUO MURO, TETSUYA HIMARU1979 Volume 28 Issue 2 Pages 81-87
Published: June 01, 1979
Released on J-STAGE: September 30, 2010
JOURNAL FREE ACCESSThe impulsive force-external loads relationships are reported experimentally on eight adult males by the method providing different actions : soft and hard motion or attached spring on the platform, four jumping down heights of the stand : 15, 33, 67 and 125cm and four additional loads to the body weight : 1, 2, 4 and 8kg. The forces are dealed with as the momentum on the landing motion and apparatus used are multi-component forces plate and 16mm camera. The impulsive force is measured using the planimeter about recorded waves of multicomponent forces exerted in the landing motion over the time of 0.8sec. The results obtained are as follows ;
1) The impulssive forces are increased on the relation of the logalithmic function proportionally with the height of stand and with the weight of load.
2) According to analyses of the landing motion, these angles of the ankle, the knee and the hip are flexed greater in proportion to heigher of the stand but no changes of these angles of body segments are showed with weighter of additional loads.
3) Taking these results and reference into consideration, absorbable landing motion has been assumed to involve decrement oscillation in internal body segments and to maintain potential using for the next motion.View full abstractDownload PDF (745K) -
MASAHIRO KANEKO, TAKESHI YAMAZAKI, JIRO TOYOOKA1979 Volume 28 Issue 2 Pages 88-94
Published: June 01, 1979
Released on J-STAGE: December 10, 2010
JOURNAL FREE ACCESSIn order to re-evaluate the mechanical efficiency during bicycle pedalling the total mechanical work (internal work + external work) and the energy expenditure were determined on four adult males (20-21 years) . The subject worked on a Monark bicycle ergometer with 6 different loads (0-5kp) at a constant pedal frequency of 50rpm. The internal work (W-int) to accelerate the leg itself was determined by a cinematographic procedure used by Fenn (1930) . With the data of external work (W-ext) and energy expended above resting (Et-Er), the‘true’efficiency has been calculated as
‘True’efficiency=W-int+W-ext/Et-Er×100
The result obtained was as follows : 1) The time course of kinetic energy due to leg movement was similar to those in walking and running reported previously. 2) The W-int at 0kp ranged in about 70-90kgm/min. In the mean values of four subjects the W-int tend to be constant at the loads from 0 to 3kp (about 80kgm/min), but increased appreciably at higher loads of 4-5k p (about 100-110kgm/min) . 3) The ratios of W-int to W-ext were about 20-30% at lkp, 10-20% at 2kp and 5-10% at 3-5kp. 4) The efficiency of leg movement only at Okp resulted in high values of about 40-85%, suggesting energy transfer between leg and inertia wheel. 5) The efficiency values at 1 to 5kp, ranging in 23.5-36.2%, appeared to show a maximum at intermediate work loads. 6) The‘true’efficiency so calculated did not largely differ from the efficiency calculated by conventional way ; 1.5-4% higher than the work efficiency, 2-5% higher than the net efficiency, and 3-5% higher than the apparent efficiency at intermediate loads.View full abstractDownload PDF (820K) -
TAKASHI YAMAMOTO1979 Volume 28 Issue 2 Pages 95-103
Published: June 01, 1979
Released on J-STAGE: September 30, 2010
JOURNAL FREE ACCESSThe purpose of the present study is threefold : first, to observe simultaneously the changes in both the frequency of motor unit (MU) discharges and the amplitude of surface electromyogram (EMG) during the prolonged and sustained voluntary efforts; and second, to demonstrate the effects of arterial occlusion on the frequency of MU discharges ; lastly, to discuss the mechanism of motor control in the light of the present results and others'. Two male adults participated in the experiment. They were with no nervous disorders, right-handed, aged 24 and 33 years. Each subject was seated with both eyes closed in a chair in an electrically shielded room. He held a weight of 1 kg on his wrist during periods of about 45 minutes. The angle of his elbow joint was maintained at 90 degrees during the course of the experiments. The impulses of MU and the surface EMG were led off from muscles biceps brachii of the left upper arm by using coaxial needle electrodes and surface ones respectively. Discharge intervals of MUs were recorded as ordinate by means of ‘Electro-tachograph’. The action voltages of single MU was monitored for differentiation from that of others with a cathode-ray oscillograph and with a loud speaker. The subject's complaints were noted during the course of the experiments. The following results were obtained.
1. The patterns of changes in the frequency of discharges of MUs were divided into three types. The first pattern showed the steep decrease in the frequency of discharge for short period, and at last the discharge disappeared, the second the gradual prolongation of discharge intervals and the increase in both irregular fluctuation and slow undulation, the third constant frequency of discharge even immediately before the exhaustion of voluntary effort.
2. The undulation and prolongation of discharge intervals appeared during the abolition of blood supply to the arm. It did not recover for about 1 minute even though the arterial occlusion was released.
3. The gradual increase in the amplitude of direct EMG in muscles biceps brachii was observed during holding a weight of constant load.
4. The rotational activity of MU was suggested to exist in the case of prolonged, sustained and voluntary muscular contraction.
5. The gradual increase in prolongation and undulation of MU seems to come from the decrease in number of afferent impulses resulting from fatigue.View full abstractDownload PDF (1071K) -
SHIGEHIRO YOSHIZAWA, HIROKO HONDA1979 Volume 28 Issue 2 Pages 104-111
Published: June 01, 1979
Released on J-STAGE: September 30, 2010
JOURNAL FREE ACCESSMaximal oxygen uptakes were determined by means of ground run for 53 male and 56 female subjects aged from 3 to 5 years.
Furthermore 38 male and 45 female subjects restricted on the age of 4 and 5 years were chosen and 5 minute run was loaded on them to know their aerobic motor performance.
The following results were obtained:
1) Male absolute values of maximal oxygen uptakes (l/min) avaraged 0.655, 0.789, and 0.904 respectively at the age of 3, 4, and 5 years. The corresponding values for females were 0.523, 0.751, and 0.808.
2) For males mean values of maximal oxygen uptakes in terms of body weight (ml/ kg/min) were 42.60, 47.36, and 51.31 respectively.
For females the corresponding values only reached 35.91, 44.48, and 44.20. The sex differences were found at the age of 3 and 5 years.
3) The developments of relative maximal oxygen uptakes (ml/kg/min) with increasing age (months) were expressed by the following regression equations for males and females respectively;
y=52.723 logx-44.071 (n=53, r=.487)
y=44.095 logx-33.980 (n=56, r = .445) .
4) The regression equations of absolute maximal oxygen uptakes (l/min) to body weights (kg) were the following ;
y=0.51x-.125 (n=53, r=.729) for males
y=0.043x+.007 (n=56, r=.747) for females.
5) During 5 minute run males could cover 798.85m and 844.00m respectively at the age of 4 and 5 years. The corresponding values by females were 779.29m and 785.38m. Males could run significantly faster than females.
6) The correlation coefficients between relative maximal oxygen uptakes (ml/kg/min) and distances covered for 5 minutes (m) were .500 for males and .510 for females respectively.
The regression equations of 5 minute run (m) and maximal oxygen uptakes related to body weight (ml/kg/min) were
y=5.034x+576.680 for mals
y=5.009x+558.408 for females.View full abstractDownload PDF (897K) -
KUNIATSU NAGAMI, SHOICHI NAKANO1979 Volume 28 Issue 2 Pages 112-121
Published: June 01, 1979
Released on J-STAGE: September 30, 2010
JOURNAL FREE ACCESSIn the present report, significances of voluntary muscular relaxations were studied. Pattern of relaxation in elbow flexor muscles was examined in two conditions, with and without relaxation of contralateral muscles (Active Relaxation : AR, Passive Relaxation : PR, respectively) .
EMG patterns of biceps were obtained in various experimental conditions to investigate characteristics of each muscular relaxations. Arm flexor strength was exerted with saw-tooth and square forms produced by Low Frequency Generator, and in other case the strength was voluntarily exerted as fast as possible.
Muscular relaxation time was determined by the difference between begining of tension decrease and vanishing point of biceps spike discharge.
The results were ;
1) PR was faster than AR, but both relaxation times were prolonged following the increment of initial tension. There were no significant differences in the times between left and right arms, and between supine and prone positions of the forearm. Relaxation time in the square form muscular exertion was the fastest in AR.
2) Quickness of the biceps relaxation in PR was significantly correlated with the velocity of extensor muscular contraction. (r=0.41)
3) However, a transient excess tension development over the initial tension was observed at the initiation of relaxation in both conditions (less than 1 kg and 100 msec in most cases) . Both the excess tension produced and its duration were greater when the initial tension was higher. The rate of rise (g/msec) in PR was higher than AR.
These results suggested that each muscular relaxation in this study was conducted by different inhibitory systems. The inhibitory system in Active Relaxation might be localized in higher level of the central nervous system than that of Passive RelaxationView full abstractDownload PDF (7788K) -
1979 Volume 28 Issue 2 Pages 127-233
Published: June 01, 1979
Released on J-STAGE: September 30, 2010
JOURNAL FREE ACCESSDownload PDF (18548K)
- |<
- <
- 1
- >
- >|