Survival prognosis of Japanese with severe motor and intellectual disabilities living in public and private institutions between 1961 and 2003.

BACKGROUND: Although the prognosis for survival in people with severe functional disabilities is a serious concern for their families and health care practitioners, there have been few reports on survival rates for this population. Every year, the Japanese Association of Welfare for Persons with Severe Motor and Intellectual Disability collects anonymous records of individual registrations and deaths from all private and public institutions, excepting national institutions. We used these data to estimate the prognosis for survival. METHODS: We reviewed the records of 3221 people with severe motor and intellectual disabilities (SMID); all subjects had lived in one of 119 public or private institutions in Japan between 1961 and 2003. Kaplan-Meier survival estimates were calculated according to disability type and birth year range. RESULTS: Of the 3221 persons, 2645 were alive and 576 had died. The survival rate at the age of 20 for all subjects was 79% (95% confidence interval, 78%-81%). Among people who were unable to sit, those with lower intelligence quotients had lower survival rates. CONCLUSIONS: The survival rate among people with SMID housed in public and private institutions in Japan was much worse than that of the general population, and has not improved since the 1960s.

Sex differences in mechanomyographic responses to voluntary isometric contractions.

PURPOSE: This study was designed to compare mechanomyography (MMG) and the force relationship during isometric ramp contractions of biceps brachii muscles in females and males to identify sex differences in the MMG responses. METHODS: Subjects (10 females and 9 males; age range, 20-26 yr) were asked to exert an isometric elbow flexion torque from 5 to 80% maximal voluntary contraction (MVC) at a constant rate of 10% MVC per second. The MMG signal was normalized to muscle cross-sectional area (CSA) as measured by ultrasound imaging. RESULTS: MVC and CSA were significantly different between the two sex groups (males>females); however, there was no sex difference in the MVC relative to muscle CSA (MVC/CSA). The root mean squared amplitude of the MMG (RMSMMG) was significantly greater in the male group than the female group. The RMSMMG relative to muscle CSA was also different between the two sex groups (males>females). The sex difference in the RMSMMG/CSA was more pronounced with increasing torque. The torque levels at which the inflection points in the MMG amplitude were located were different between the two sex groups. The mean power frequency (MPF) of the MMG in the female group increased monotonously, which was different from that in the male group. CONCLUSION: Our results suggest that the sex differences in MMG responses and motor unit (MU) activation strategy result from the predominant activity of the MU with slow-twitch fibers and an effective fused tetanus in females. In addition, the sex-related differences in muscle morphology, subcutaneous adipose tissue, and muscle stiffness appear to be insufficiently reflected in the present MMG responses, particularly relative to muscle CSA.

Age-related changes in the interactive mobility of the hip and knee joints: a geometrical analysis.

This study examined any systematic age-related change in the passive range of motion (PROM) of the hip and knee joints. Seventy-seven healthy male volunteers ranging in age from 15 to 73 years were assessed. A geometrical range of motion (ROM) analysis was applied, which could evaluate the effects of both monoarticular and biarticular muscles. The PROM of the hip joint decreased progressively with advancing age, whereas that of the knee joint remained unchanged. In addition, the interactive PROM of the hip and knee joint associated with biarticular rectus femoris and hamstring muscles also showed an age-related reduction. The progressive reduction of the ROM is probably caused by shortening of muscles or connective tissues due to reduced compliance of joint structures and degenerative changes in spinal alignment, as well as by diminished muscle stretching resulting from a decrease in daily physical activities with advancing age.

Effect of exercise at the AT point for children with cerebral palsy.

Eleven children with spastic cerebral palsy (CP) who could walk underwent exercise at the anaerobic threshold (AT) point. The subjects exercised for 20 minutes per session, twice a week for a period ranging from 6 to 20 weeks. The subjects were divided into two groups. The leg exercise group contained six CP children who exercised on a cycle ergometer with average attendance of 1.8 days a week. The other five CP children constituted the arm exercise group and exercised using an arm cranking ergometer with average attendance of 1.5 days per week. After the exercise period, the oxygen uptake (VO2) at the AT point increased significantly in the children in the leg exercise group. On the other hand, the VO2 at the AT point did not change in children in the arm exercise group. These results demonstrate that cycle ergometer exercise at the AT point is effective in improving the physical endurance of children with CP. In contrast, arm exercises for children with CP seem to have little effect on increasing physical endurance.

Frequency response model of skeletal muscle and its association with contractile properties of skeletal muscle.

The aims of the present study were to develop a mathematical model of the skeletal muscle based on the frequency transfer function, referred to as frequency response model, and to presume the relationship between the model elements and skeletal muscle contractile properties. Twitch force in elbow flexion was elicited by applying a single electrical stimulation to the motor point of biceps brachii muscles, and then analyzed visually by the Bode gain and phase diagram of the force signal. The frequency response model was represented by a frequency transfer function consisting of five basic control elements (proportional element, dead time element, and three first-order lag elements). The model element constants were estimated by best-fitting to the Bode gain and phase diagram of the twitch force signal. The proportional constant and the dead time in the frequency response model correlated significantly with the peak torque and the latency in the actual twitch force, respectively. In addition, the time constants of the three first-order lag elements in the model correlated strongly with the contraction time and the half relaxation time in the actual twitch force. The results suggested a possibility that the individual elements in the frequency response model would reflect the biochemical and biomechanical properties in the excitation-contraction coupling process of skeletal muscle.

Age-related change in motor unit activation strategy in force production: a mechanomyographic investigation.

This study was designed to examine the effect of increasing age on the recruitment and activation of motor units (MU) in the biceps brachii muscle, using the mechanomyogram (MMG)/force relationship during isometric ramp contractions. The relationships between the root mean squared amplitude (RMS) and mean power frequency (MPF) of the MMG and relative force (% MVC) in the elderly (male, n = 10, age = 69.8 +/- 4.7 years, mean +/- SD) were markedly different from those in the young group (male, n = 15, age = 22.7 +/- 1.8 years). In elderly individuals, the RMS increased progressively with force up to 57.6 +/- 3.4% MVC, when a brief rapid increase was followed by a stable trend beyond 63.6 +/- 3.7% MVC. The MPF increased slowly up to 59.4 +/- 2.3% MVC; after a temporary reduction from 59.4% to 64.3 +/- 2.0% MVC, it then increased progressively again. In conjunction with absolute force (F(abs)), both the RMS and MPF in the elderly were smaller than those in the young group throughout the submaximal levels of force exerted. The results reflect an alteration in MU activation strategy, with a predominant role for MUs with slow-twitch fibers and an effective fused tetanus induced at lower firing rate of the MUs, resulting from age-related neuromuscular changes.

Mechanomyographic responses during voluntary ramp contractions of the human first dorsal interosseous muscle.

The aim of this study was to examine the mechanomyogram (MMG) and force relationship of the first dorsal interosseous (FDI) muscle as well as the biceps brachii (BB) muscle during voluntary isometric ramp contractions, and to elucidate the MMG responses resulting from the intrinsic motor unit (MU) activation strategy of FDI muscle with reference to the MMG of BB muscle. The subjects were asked to exert ramp contractions of FDI and BB muscle from 5% to 70% of the maximal voluntary contraction (MVC) at a constant rate of 10% MVC/s. In FDI muscle, the root-mean-squared amplitude (RMS) of the MMG decreased slowly with force up to 21%, and then a progressive increase was followed by a relatively rapid decrease beyond 41% MVC. The RMS/%MVC relationship in BB muscle consisted of an initial slow increase followed by a rapid increase from 23% MVC and a progressive decrease beyond 61% MVC. With respect to the mean power frequency (MPF), FDI muscle demonstrated no obvious inflection point in the MPF/%MVC relationship compared with that in BB muscle. Namely, the MPF of FDI muscle increased linearly through the force levels exerted. In contrast to FDI muscle, the MPF/%MVC relationship in BB muscle was decomposed into four specific regions: (1) a relative rapidly increase (<34% MVC), (2) a slow increment (34-53% MVC), (3) a temporary reduction (53-62% MVC), and (4) a further rapid increase (>62% MVC). The different MMG responses between FDI and BB muscles are considered to reflect the fact that the MU activation strategy varies among different muscles in relation to their morphology and histochemical type. Namely, the rate coding of the MUs plays a more prominent role in force production in relatively small FDI muscle than does MU recruitment compared with their respective roles in the relatively large BB muscle.