The purpose of this study was to examine the effect of two kinds of neck muscle training on the isometric cervical extension strength (ICES) and cross-sectional area (CSA) of the neck extensor muscles.The subjects which were examined consisted of 22 male college judo athletes. Each was assigned to one of three groups: shrug and upright rowing training (SU); shrug, upright rowing and dynamic neck muscle training (COM); and control (CONT). The SU and COM groups trained 3 days per week for 9 weeks. The ICES and CSA of the neck muscles were measured before and after muscle training.The ICES of the COM group showed a significant increase after training. For the CSA, although a significant increase was only found in a superficial area of the neck extensor muscles in the SU group, the COM group showed significant increases in all areas.This study determined that combined neck muscle training is effective for developing the neck extensor muscles.

A study was conducted to evaluate and compare neck muscle strength between two levels of college American football players with the aim of preventing neck injuries. The subjects were American football players at N University (n=52) belonging to the first level league and American football players at G University (n=14) belonging to the third level league. The findings were as follows.
1. The neck muscle strength of freshman players at N University tended to be lower than that of senior players.
2. It was shown that the neck muscle strength/body weight of experienced American football players was 10-30% higher than that of inexperienced players.
3. There was a significant difference in neck muscle strength/body weight between N University and G University in 1997. However, there was no significant difference between them in 1998, because neck muscle strength/body weight of G University players increased by 13-30% after neck muscle training for about nine months. It was suggested that coaching staff must evaluate the neck muscle strength of each player, especially in freshmen who have had no experience of American football, in order to prevent neck injuries because mismatch of performance level may cause catastrophic neck injury.

The purpose of this study is to evaluate and compare isometric cervical extension strength (extension strength) of college American football players belonging to different level leagues at the eight cervical positions measured by a cervical extension machine (Medx Inc.) and give some suggestions for preventing neck injuries. The subjects were American football players at N University (n=41) belonging to the first-level league and at G University (n=32) belonging to the third-level league. The findings were as follows.
1. The isometric cervical extension strength/body weight of players at N University was sig-nificantly higher than that of G University at 72°, 54°and 36° (a neutral cervical position) .
2. The extension strength/body weight of the linemen at N University was significantly higher at 108°, 54°and 36°than that of the linemen at G University. While there were no significant differences between universities in the eight cervical positions of back players herein referred to as‘backs’.
In conclusion, it was shown that there were significant differences in the extension strength and the extension strength/body weight between teams of different levels. The differences tended to be larger between the linemen than between the backs. Therefore, it was suggested that the evaluation of neck muscle strength was important for preventing neck injuries especially caused by a mismatch of players at different performance levels.

The purpose of this study was to examine the effects of dynamic neck muscle training using a cervical extension machine (CEM) on isometric cervical extension strength (ICES) and a cross-sectional area of neck extensor muscles.Subjects were 18 male college judo athletes divided into a control group (n=10) and training group (n=8), respectively. In the training group, dynamic neck muscle training was performed for a 6 week training period, followed by a 10 week training period. There was a detraining period of 12 weeks between the first training period and the second. The ICES was measured at eight angles using a CEM, and the neck muscle cross-sectional area was determined using magnetic resonance imaging.The ICES and cross-sectional area of neck extensor muscles in the training group showed significant increases after the second training period. In particular, the increase in the cross-sectional area was greater in the deepest layer of the neck extensor muscles (rotator, multifidus and semispinaris cervicis muscles) than in the superficial layer (trapezius muscle). In the control group, no significant changes in ICES or cross-sectional area were observed.In conclusion, it was shown that dynamic neck muscle training using a CEM was effective in developing both ICES and the cross-sectional area of neck extensor muscles, especially in the deepest layer.

The purpose of this study was to examine the relationship between isometric cervical extension strength and the cross-sectional area (CSA) of neck extensor muscles in order to obtain fundamental data for conducting neck muscle training to prevent neck injuries. Subjects were 8 males belonging to the judo or American football club in N University. Isometric cervical extension strength was measured at eight positions (0°, 18°, 36°, 54°, 72°, 90°, 108°, maximum flexion) using a cervical extension machine (Medx Inc., USA) . A transaxial magnetic resonance imaging (MRI) image of neck muscles was obtained at the intervertebral disk between C4 and C5 (using an MRI machine made by Hitachi medical Corp., JAPAN) . The findings were as follows.
1. The correlation between isometric cervical extension strength at 36°, 54°and 72°in a neutral position (60.8±1.4°) and the CSA of neck extensor muscles were higher than at other degrees (0°, 18°, 90°, 108°, maximum flexion) . In particular, there was a significant linear relationship at 54° (slightly extended position) .
2. A significant linear relationship was observed between the neck girth and CSA of neck extensor muscles.
In conclusion, there was a closer relationship between isometric cervical extension strengths at certain angles in a neutral position and the CSA of neck extensor muscles. Therefore, it was shown that isometric cervical extension strengths at certain angles in a neutral position mainly represented the CSA of neck extensor muscles.

In this study, 10 healthy students were subjected to experiments. They bathed in plain hot spring water and hot spring water with 2% Togol mud at 39°C for 10min at an interval of 1 week. No difference in the change rates of pulse rate and blood pressure was observed between the two types of bathing. Forehead and oral temperatures decreased slightly after bathing in plain hot spring water. However, after bathing in hot spring water with Togol mud, the forehead temperature tended to be higher than that before bathing while the oral temperature increased significantly after bathing. Skin surface temperatures on the chest wall, left instep, and right forearm increased significantly after both types of bathing. Changes in the skin temperature after bathing in hot spring water with Togol mud tended to be greater than those after bathing in plain hot spring water. Eight out of 10 students felt warmer after bathing in hot spring water with Togol mud. These findings suggest that bathing in hot spring water with Togol mud is useful for medical care.