The purpose of this study was to compare echocardiographically measured left ventricular (LV) dimensions of 85 trained 11-12-year-old athletes with 106 untrained children matched for skeletal age and fat-free mass. Training status for each group applied to the 3 years prior to the measurements. It was found that 12 min and 100 m runs demonstrated the superior athletic ability of the trained children, but there were no significant differences in LV internal diameters at diastole and systole, in LV posterior wall thickness, or in LV end-diastolic volume and LV mass. These data indicate that little difference occurs in LV size between moderately trained and untrained 11-12-year olds or between boys and girls matched for fat-free mass and skeletal age. It is also evident that consistent but moderate training during late pre-adolescence has little effect on LV development.
The purpose of this study was to analyse, by electromyographic technique, abdominal muscle activity in exercises commonly advocated as being effective in improving abdominal muscle performance. In general exercises from the lying position were found to involve the rectus abdominis and oblique muscles more than those exercises from standing, sitting or kneeling positions. Further, among exercises from lying, 'trunk on legs' and 'trunk plus legs' involved these muscles more than 'legs on trunk' exercises. With pregnancy and in the puerperium there was a change in the pattern of abdominal muscle involvement in exercises from the lying position, suggesting that the traditional division of exercise lists into 'antenatal' and 'postnatal' is not optimal: the demarcation "circumnatal" (around the time of birth) and "abnatal" (remote from the time of birth) would appear to be more appropriate. Details are given of the method of assessment of exercises, data analysis and interpretation of results. The findings have implications for the selection of exercises for clinical Use in obstetric physiotherapy.
Fulton (1949) states that the recti abdominis contract reflexly when the lower intercostal nerves supplying the skin of the abdomen are stimulated. He also states that stimulation of certain sensory nerves in the leg produces contraction of the abdominal muscles in association with the flexor response. Miller (1924), Miller & Simpson (1924) and Miller & Waud (1925a, b), using the decapitate cat with mechanical recording, showed that electrical stimulation of the cut central ends of visceral nerves evoked reflex contractions of the abdominal wall, diaphragm and limb muscles. Similar reflexes were obtained by mechanical stimulation of abdominal viscera.In man it is well known that the abdominal muscles contract in conditions of visceral irritation, and there is often involvement of hip and leg flexor muscles. In these conditions also the abdominal reflexes are more readily evoked (Mackenzie, 1920).In this paper we describe the electromyographic response elicited in the abdominal and some limb muscles of the cat and rabbit in response to various afferent stimuli. A preliminary account of some of our results has already been published (Chennells & Floyd, 1951). METHODCats under chloralose anaesthesia (80 mg/kg body weight) and under pentobarbitone sodium anaesthesia (50 mg/kg body weight) and a few cats and rabbits under allobarbitone (B.P.C.) anaesthesia (0-6 ml./kg body weight) were used in these experiments.The abdominal muscles of the cat and the rabbit are innervated by branches of the intercostal and lumbar nerves, chiefly T 13 (T 12, rabbit) and L 1-3. A longitudinal skin incision, made over the ventral edge of the back muscles, reveals the cutaneous branch of the nerve, running towards the mid-line and supplying the skin of the abdominal wall; by cutting down on the external oblique muscle, the bifurcation of the nerve into cutaneous and muscle branches is revealed. The muscle branch runs caudad, roughly parallel to the line of the vertebral column, and supplies the external oblique, internal oblique and rectus abdominis muscles.
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