This study aimed to examine the effect of linear polarized near-infrared light (PL) irradiation on the recovery of isokinetic muscle exertion and subjective fatigue sensation in muscles after strenuous exercise. Eighteen healthy college students participated in the experiment for all conditions of meridian point irradiation (MPI), femurs muscles irradiation (FMI), and no irradiation (NI) . They all took isokinetic knee extension and flexion tests (IK test) before and after strenuous exercise up to exhaustion. Each subject was irradiated at the meridian point or in femurs muscles after the second IK test. The third IK test was carried out after ten-minutes rest. The effects of PL irradiation were confirmed on the recovery rate of muscle fatigue in knee extension motion with high load intensity (PT 60 d/s and TW 60 d/s : MPI, FMI> NI, p<0.05 16.2%, 13.4%>8.5%, and 16.1%, 14.1%>8.3%, respectively) . Also, in flexion motion, significant differences in the recovery-degree for each condition were found, and the effect of PL irradiation was suggested. There was no difference between the effect of MPI and FMI. In addition, subjective fatigue sensation in muscles after rest decreased significantly in MPI as compared with NI (MPI: 52.1%>NI : 36.6%, p<0.05) . From the above, it was suggested that PL irradiation is effective on recovery in muscle fatigue after strenuous exercise regardless of irradiation conditions, MPI or FMI.
The purpose of this study was to examine the effects of off-season training on the anaerobic power output and muscle thickness of male varsity rowers. 23 rowers participated in this study. Four all-out cycle ergometer work tests lasting 7 and 40 seconds were used to estimate anaerobic alactic power (AAP) and anaerobic lactic power (ALP) with leg (pedaling) and arm (cranking) exercises. AAP was computed as the highest power output during 7 seconds and ALP was obtained as the mean power output during 40 seconds. Muscle thickness was measured by B-mode ultrasonography at 11 sites on the body. There were significant differences between before and after off-season training in AAP (cranking : 8.4±1.00 vs 9.2±1.10W /kg, p<0.001, pedaling: 14.4± 1.10 vs 15.0±1.00 W/kg, p<0.001) and ALP (cranking : 5.2±0.42 vs 5.5±1.20W/kg, p<0.001, pedaling: 10.1±0.62 vs 9.5±2.10 W/kg, n, s.) . Muscle thickness increased significantly as a result of off-season training at sites on the biceps, triceps, pectoralis major, subscaplar and hamstrings. Similarly, there were significant differences in estimated muscle cross-sectional area (MCSA) on sites on the elbow flexor (20.6±2.6 vs 22.1±1.8cm2, p< 0.01), elbow extensor (25.3 ±4.8 vs 28.6±4.2cm2, p<0.001) and knee flexor (71.1±5.8 vs 74.3±5.2cm2, p<0.01) . The main training program in the off-season consisted of resistance training of the whole body. The high intensity training, used by male varsity rowers during off-season training, increased arm AAP, leg AAP, arm ALP and muscle thickness of the upper body ; but there was no difference in leg ALP and knee extensor muscle. It was suggested that improvements in leg ALP and knee extensor muscle are necessary to during the off-season training program of male varsity rowers.
Electromyographic muscle activities of the shoulder muscles during shoulder external rotation with reference to load magnitude were studied in 8 healthy male subjects without history of shoulder injuries. In addition, we discussed the relationship between rotator cuff muscles and superficial muscles. The subjects performed shoulder external rotation from 60°internal rotation to 45° external rotation at 20° of shoulder abduction and 20° of flexion. A Cybex dynamometer used to prescribe angle and velocity of the shoulder movement. At the same time, intramuscular wire electrodes were inserted into the supraspinous, infraspinous and teres minor muscles, and then surface electrodes were placed over the posterior deltoid and middle trapezius muscles. The load magnitude ranged 2-18 Nm and the angle velocity was set at 15 deg/sec. The rotator cuff muscles became significantly to be activated from 2 Nm (the supraspinous and infraspinous m.) and from 4-5 Nm (the teres minor m.) compared with the muscle activity during non-load. The superficial muscles became significantly to be activated from 4-7 Nm (the posterior deltoid m.) and from 3-6 Nm (the middle trapezius m.) compared with the muscle activity during non-load. Within the load range (18 Nm 46.8% MVC), %iEMG of the rotator cuff muscles was always larger than that of the superficial muscles. Therefore, we concluded that the contribution of the rotator cuff muscles was larger than that of the superficial muscles up to 3-4 Nm, and activities of the superficial muscles increased gradually from 3-4 Nm during shoulder external rotation.
The purpose of this study was to examine the individual differences in relative grip-strengthendurance (RGE) variables and relations between force, endurance time and level of subjective musclefatigue sensation (SMS) of RGE. Endurance time and SMS during grip-strength exertion using various relative demand values to the maximal grip-strength-value (MAX) were analyzed. Subjects were 23 healthy adults (male 10 and female 13) . Four demand values of 25, 35, 50 and 75% were selected as relative demand values to MAX. The grip-strength-exertion value was input into a personal computer using the system of grip-strength with a strain-gauge (Yagami : ED-D 100 R) . The results are summarized as follows: 1) Muscle group related to grip-strength exertion recovered up to about 60% of initial within 10-15 sec after grip-strength exertion stopped regardless of the degree of relative demand values. 2) The SMS in any relative demand values reached a peak after continuing relative demand values became impossible, and the tendency is stronger with a higher demand value. 3) With about 25% relative demand values, physiological muscle fatigue and SMS advanced at almost the same time, and the grip-strength exertion was possible for a little while after the SMS reached a peak. 4) With the lower relative demand values under 50%, the influence of SMS appeared stronger by extending the endurance time and the decline-delay of grip-strength-exertion. 5) With relative demand values over 50%, continuing relative demand values became impossible within a short time, and the peak SMS appeared earlier than that of relative demand values. On the other hand, the continuing the lower relative demand values was possible to some extent, and individual differences in the continuance and peak arrival-times of SMS were large.
In order to elucidate factors associated with sudden cardiac death during exercise in school from 1986 to 1995, the frequency and characteristics of death were investigated. The authors collected data from the booklet “Deaths and injuries under school supervision” published by the National Stadium and School Health Center of Japan. There were 480 cases of sudden cardiac death during exercise from 1986 to 1995, and boys accounted for 74% of these cases. In more recent years, the incidence per one hundred thousand persons has decreased in elementary and senior high schools ; whereas it has increased in junior high school. Regarding activity at the time of occurrence, 251 cases (52%) occurred during physical education ; 144 cases (30%) during sports club training; and 85 cases (18%) during school events. Incidence during sports club training in elementary school was significantly lower than that in junior and senior high school. Regarding past history, in most case, there was no past history of heart disease. Regarding types of exercise, incidence while running was highest (48%) . Among “running” cases, most occurred during training. Regarding past history, the incidence of cases showing a past history was high for light intensity running, and the incidence of cases without a past history was high during running that involved upper light intensity running. Regarding the stages of running, incidence was markedly higher in the first half of the running period among cases showing a past history, and during training and for light exertion, while the incidence was high in the latter half of the running period among cases without a past history, and also high during timed races and for upper light exertion. Among causes of death, acute heart failure was the most frequent cause. As a result, more attention should be paid to circumstances related to a high incidence of death and the necessity of teaching health care and the prevention of sudden death at school and at home.
The purpose of this study was to examine the bone stiffness of healthy girls during their growth period and factors affecting on such stiffness. The subjects were 302 secondary school girls in Tokyo. Parameters examined included the body characteristics (standing height, body weight, bone stiffness measured by ultrasound, muscle thickness measured with the ultrasound B-mode system), extension power of the lower limb (containing the knee and hip joints), and a questionnaire about the daily intake of milk, kinds of meals and number of years from menophania. These examinations were carried out in June 1997. Results were summarized as follows : 1) From the observation of bone stiffness in secondary school girls, it appears that bone stiffness increases during the junior high school period. In other words, the bone stiffness of the subjects had almost reached on adult level by high school. 2) A significant positive correlation was recognized between chronological age and bone stiffness (r=0.365, p<0.05) . A positive correlation also existed between the years from menophania and bone stiffness (r=0.477, p<0.05) . These coefficients showed that the years from menophania correlate with bone stiffness more closely in comparison with chronological age. 3) In the period when short comparatively years from menophania, body characteristics, which were the index of maturity, correlated to bone stiffness. However, muscle thickness/power, which was related to exercise habit, became the major parameter correlating with bone stiffness. These results suggest that factors affecting bone stiffness should differ according to the growth period. 4) Comparison of different athletic clubs showed that the bone stiffness of volleyball players was higher than that of control. These data suggest that physical education class, which was given 3 times a week, is not enough for total body development in both quality and quantity. In other words, physical education should be better matched with total physical development, including the growth of healthy bones.