Japanese Journal of Physical Fitness and Sports Medicine

ON THE ENERGY METABOLISM OF ROPE SKIPPING

SHINKICHI OGAWA, YOSHINORI FURUTA, SHIGERU OBARA, TATSURO OBARA, KAZUT ...

1974 Volume 23 Issue 3 Pages 89-95
Published: September 01, 1974
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.7600/jspfsm1949.23.89

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In this study, energy consumption of three types of basic rope skipping was measured, together with an investigation of work intensities. The subjects were 5 healthy adult male. The results of this study were as follows :
1) The average relative metabolic rate (RMR) of 1 skip (one skip to one forwardturn of rope), 2 skip (double skip to one forward-turn of rope) and running skip were 13.6, 11.7 and 10.3, respectively, and it was noted that work intensities decrease in order of 1 skip, 2 skp and running skip.
2) On the three types of five minute rope skipping, the oxygen intake for the last one minute of exercise of 1 skip was equivalent to 63.7-78.0% of maximal oxygen intake, and in cases of 2 skip and running skip were 57.5-76.3% and 56.8-67.2%, respectively.
3) When skip frequencies of 1 skip were 92, 120 and 156 skips/min, respectively, oxy-gen requirement for 120 skips/min was the lowest, therefore, it was noted that skip fre-quency of 120 skips/min was optimal.

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INVESTIGATION OF LEAN BODY MASS AS A LIMITING FACTOR OF MAXIMUM OXYGEN UPTAKE

KAORU KITAGAWA, KOMEI IKUTA, YUKO HARA, KOICHI HIIRTA

1974 Volume 23 Issue 3 Pages 96-100
Published: September 01, 1974
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.7600/jspfsm1949.23.96

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Total muscle mass is thought of as one of the intrinsic limiting factors of aerobic power. But it is not yet clarified how the total muscle mass limits the magnitude of aerobic power. The purpose of this study was to clarify the relationship between total muscle mass and aerobic power and to make a further discussion conscerning its limiting factors. 17 sedentary students with a mean age of 19.3 (18-23) years, and 17 varsity footballers 19.9 (19-21) years old, were measured for lean body mass, which was an approximate indicator of the total muscle mass, by underwater-weighing method and VO₂ max by bicycle ergometer. The correlationship between lean body mass and VO₂max for sedentary students was found to be higher (r=0.821) than for footballers (r=0.595) . It was also shown that footballers had a significantly larger VO₂max per 1kg of lean body mass than sedentary students. Previous studies showed that the increment of VO₂max through endurance training was caused by the increment of such factors as mitochondria, maximum cardiac output and maximum stroke volume, and was not by lean body mass. So, it was concluded that lean body mass was a reasonable limiting factor for sedentary students, but was not a stable factor of VO₂max because of lower linearlity for footballers and the significant difference on VO₂max per 1kg of lean body mass between two groups.

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FINE CONTROL OF VOLUNTARY CONTRACTION

—SINGLE SPIKE DISCHARGES OF SINGLE MOTOR UNITS WITHOUT DISPLAY OF SPIKES—

Hiroshi KURATA

1974 Volume 23 Issue 3 Pages 101-102
Published: September 01, 1974
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.7600/jspfsm1949.23.101

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LONG PERIOD CONSTANCY OF THRESHOLD FORCE OF SINGLE MOTOR UNITS IN VOLUNTARY CONTRACTION AND ITS CHANGE INDUCED BY DESIRE FOR MICTURITION

Hiroshi KURATA

1974 Volume 23 Issue 3 Pages 103-111
Published: September 01, 1974
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.7600/jspfsm1949.23.103

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In order to examine the characteristics of the activities of motor units over a long time, single spikes and consecutive discharges of single motor units were recorded by use of an inserted electrode. In addition, the tension at isometric contraction of knee extension or elbow flexion was simultaneously recorded. The results are summarized as follows.
1) The relative threshold value of a single motor unit in m. vastus medialis stayed constant even for 13 hours. However, the threshold value increased with an increase in desire for micturition and returned to the original value upon disappearance of desire for micturition.
2) It was observed in surface electromyograms of m. rectus femoris that both the amplitudes of potentials at the moment of single spike appearance and those corresponding to a constant sustained tension increased on raise of desire for micturition. Under the same circumstances, however, some motor units in m. rectus femoris showed an increase of, and the other motor units showed a decrease of, their relative threshold value.
3) It was also found in m. biceps brachii that the relative threshold value of a single motor unit stayed constant for 6 hours. In this motor unit, no effect from the desire for micturition was observed.
From these results, it can be presumed that each motor unit possesses a specific susceptibility for a long period. The relative threshold value, however, changed depending upon internal conditions such as desire for micturition. It can thus be concluded that the rotation of activity among the motor units is due to the variations of the relative threshold value.

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[title in Japanese]

1974 Volume 23 Issue 3 Pages 112-114
Published: September 01, 1974
Released on J-STAGE: September 30, 2010

DOIhttps://doi.org/10.7600/jspfsm1949.23.112

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