ABSTRACT
The repeatability of the mechanomyogram (MMG) must be carefully determined before the signal can be generally used as a reliable tool in the fields such as physical fitness, sports and rehabilitation. In the present investigation, both the between-trial and between-day repeatability of the MMG was examined in the time and frequency domain and was compared with that of the more established electromyogram (EMG) . Isometric contraction trials of the biceps brachii muscles at different force levels of 10% to 90% MVC were held until a force plateau lasting 5 s was completed. The testing session consisting of 9 submaximal trials was repeated 6 times on the same day for estimation of the variation between trials. The same testing session was also performed 8 times over 3 weeks with a 2-day rest interval to examine the day-to-day variation. The coefficient of variation (CV) between-trials as well as between-days of the root mean squared (rms) MMG, mean frequency and median frequency did not demonstrate any significant differences among the force levels. The combined CV of the rms MMG over all the force levels was approximately 9 % between trials and 22% between days. The mean frequency and the median frequency presented the CV between-trials and between-days of approximately 6% and 10%, respectively. The different CV between the time and frequency domain parameters of the MMG may result from different contributing factors in the motor unit activation pattern. The results of this study suggest that the repeatability of the time domain parameter of the MMG is similar to that of the more established EMG, whereas the frequency parameters are somewhat less repeatable than those of the EMG.
ABSTRACT
The repeatability of the mechanomyogram (MMG) must be carefully determined before the signal can be generally used as a reliable tool in the fields such as physical fitness, sports and rehabilitation. In the present investigation, both the between-trial and between-day repeatability of the MMG was examined in the time and frequency domain and was compared with that of the more established electromyogram (EMG) . Isometric contraction trials of the biceps brachii muscles at different force levels of 10% to 90% MVC were held until a force plateau lasting 5 s was completed. The testing session consisting of 9 submaximal trials was repeated 6 times on the same day for estimation of the variation between trials. The same testing session was also performed 8 times over 3 weeks with a 2-day rest interval to examine the day-to-day variation. The coefficient of variation (CV) between-trials as well as between-days of the root mean squared (rms) MMG, mean frequency and median frequency did not demonstrate any significant differences among the force levels. The combined CV of the rms MMG over all the force levels was approximately 9 % between trials and 22% between days. The mean frequency and the median frequency presented the CV between-trials and between-days of approximately 6% and 10%, respectively. The different CV between the time and frequency domain parameters of the MMG may result from different contributing factors in the motor unit activation pattern. The results of this study suggest that the repeatability of the time domain parameter of the MMG is similar to that of the more established EMG, whereas the frequency parameters are somewhat less repeatable than those of the EMG.
ABSTRACT
The present study attempted to define a dynamic muscle contraction against viscosity resistance in which force is proportional to velocity of movement, and to determine its mechanical properties in comparison with isotonic and isokinetic muscle contraction. This dynamic contraction was referred to as the “isoviscous contraction” . A loading mechanism consisting of a directly-driven electromagnetic motor and an electronic control circuit was developed to enable three patterns of dynamic contraction to be performed. The torque, joint angle and joint angular velocity in the three types of dynamic contraction were measured in 8 healthy male volunteers during knee joint extension. The isoviscous contraction was not accompanied by any abrupt change in torque during the movement observed regularly in isotonic and isokinetic contraction. The instructed movement for isoviscous contraction could be performed over a wide range of joint motion at all levels of contraction. In addition to its unique mechanical properties, since the viscosity resistance produces a better damping effect against an abrupt change in torque, isoviscous contraction is considered to be a useful method of rehabilitation training in disabled patients and aged individuals. However, the great inertial force produced by isoviscous contraction corresponding to that in isotonic contraction should be further investigated.
ABSTRACT
Eighteen persons with both severe mental retardation and severe physical disabilities and ten normal persons participated to investigate cardiovascular response to hydrostatic pressure stress using supine and sitting positions. All of the handicapped subjects lay down on the bed during the entire day. They were classified into three groups. That is, the first group (LD) had not opportunity of sitting passively in daily living at all. Another two groups were given opportunity of sitting. In addition, the second group (ST 1) was unable to sit and stand independently in the past but the third group (ST 2) was able. The LD showed unchanged heart rate and decreased blood pressure with reduced peripheral blood flow in the sitting position. This suggested that serious lower function or dysfunction in both central and peripheral circulatory system. The cardiovascular function of the ST 1 was characterized by elevated heart rate and lowered blood pressure. This seemed to indicate lower baroreflex control to the peripheral vascular system. The ST 2 demonstrated similar function to the normal persons. The cardiovascular regulation in the severely handicapped persons may depend on opportu-unity of taking orthostatic posture in daily living in addition to motor adility in the past.
ABSTRACT
Daily physical activities for 12 severely physically and mentally handicapped persons were investigated using heart rates during a 24-hr period. The recorded heart rates were processed statistically and analyzed. The standard deviation and skewness for the severely handicapped persons with low ambulatory ability were significantly greater than those for the most severely handicapped persons without ambulatory ability. These properties confirmed that physical activities of daily living were extremely different for the two groups. The severely handicapped persons with low ambulatory ability had higher heart rates of about 10% relating to active physical activities. It was suggested that the active physical activities of daily living could contribute to the improvement of physical work capacity if these activities were more prolonged in duration. On the other hand, such higher heart rates were not observed in the case of most severely handicapped persons and extremely low function in their cardiorespiratory system was suspected. It became impor. tant to apply physical training to the most severely handicapped persons even though light work was performed passively.