Twenty-four-hour motor activity in human infants with and without iron deficiency anemia.

Iron deficiency anemia (IDA) is a very common nutritional problem that alters motor activity. The aim of this study was to compare 24-h motor activity in the home in healthy 6-month-old infants with and without IDA. Activity was assessed via actigraphs on the leg during 24 continuous hours in 17 Chilean infants with IDA and 18 with normal hemoglobin levels. All infants were given oral iron, and activity was reassessed at 12 and 18 months. The frequency of movement units per minute was determined for each waking/sleep state during the day and night, and the duration of each state was computed. At 6 months of age, there were no differences between anemic and nonanemic infants in time per state. However, infants with IDA showed an overall increase in motor activity compared to controls. These differences were no longer observed at 12 and 18 months of age. Increased activity during the period of IDA raises the issue of a shared underlying mechanism with restless legs syndrome, a sensorimotor dysfunction where iron deficiency increases the severity of the symptoms and iron supplementation ameliorates them. Due to previous findings of decreased motor activity in the laboratory at 12 months during the waking time surrounding an afternoon nap, we also compared those data to a nap in the home. Infants with IDA were less active in the laboratory than in the home. The home versus laboratory results suggest that contextual factors affect the motor activity of IDA infants to a larger extent than controls.

Spontaneous motor activity in human infants with iron-deficiency anemia.

This study compared spontaneous motor activity in 6-month-old Chilean infants with or without iron-deficiency anemia (IDA) who were otherwise healthy. Activity was assessed in conjunction with polysomnographic recording during an afternoon nap in 11 infants with IDA and 15 with normal hemoglobin levels. All infants were given oral iron, and activity was reassessed at 12 and 18 months. Using actigraphs placed on the ankle, the frequency of movement units per minute was determined for each waking/sleep state. The total amount of time infants were in an alert-active state before and after the nap was used to calculate the proportion of movements/minute of waking. There were no differences between anemic and nonanemic infants in total recording time, duration of sleep, or motor activity during sleep. However, infants with IDA showed reduced motor activity during waking at all ages. The magnitude of the differences increased at 12 and 18 months. Thus, IDA was associated with reduced motor activity in infants even after iron treatment. It will be important to confirm these results in a larger sample and to determine the 24-h pattern of motor activity, since reduced motor activity may limit infants' opportunities to explore and learn from the social and physical environment.

Exploration and selection of intralimb coordination patterns in 3-month-old infants.

Through the exploration of their own capacities and the selection of adaptive responses, infants learn new motor solutions. Using a conjugate reinforcement mobile procedure, previous researchers have repeatedly shown that infants increase their leg kick frequency to control a mobile that is connected to their ankles. That traditional experimental design allows multiple motor solutions to the task and therefore provides limited information about the infants' capacity to explore and select specific motor solutions. The author designed a new experimental procedure to study infants' capacity to discover and adopt specific motor solutions. The new, constraining mobile reinforcement procedure requires a specific motor response and therefore the development of a more finely tuned perception-action map than has previously been experimentally demonstrated. To gain reinforcement from the mobile, infants had to produce a coordinated hip and knee extension within the same leg. The results from the 13 infant participants showed that they were capable of increasing their frequency of coordinated movements to make the mobile move. Those results suggest that infants at the age of 89-106 days are sensitive to intralimb coordination task requirements and are capable of mapping their own limb dynamics to the environmental information.

Treadmill training of infants with Down syndrome: evidence-based developmental outcomes.

OBJECTIVE: On average, infants with Down syndrome (DS) learn to walk about 1 year later than nondisabled (ND) infants. The purpose of this study was to determine if practice stepping on a motorized treadmill could help reduce the delay in walking onset normally experienced by these infants. METHODS: Thirty families of infants with DS were randomly assigned to the intervention or control group. All infants were karyotyped trisomy 21 and began participation in the study when they could sit alone for 30 seconds (Bayley Scales of Infant Development, Second Edition 1993, item 34). Infants received traditional physical therapy at least every other week. In addition, intervention infants received practice stepping on a small, motorized treadmill, 5 days per week, for 8 minutes a day, in their own homes. Parents were trained to support their infants on these specially engineered miniature treadmills. Every 2 weeks research staff went into the homes and tested infants' overall motor progress by administering the Bayley Scales of Infant Development, Second Edition, monitored growth status via a battery of 11 anthropometric measures, and checked parents' compliance with physical therapy and treadmill intervention. The primary measures of the intervention's effectiveness were comparisons between the groups on the length of time elapsed between sitting for 30 seconds (entry into the study) and 1) raising self to stand; 2) walking with help; and 3) walking independently. RESULTS: The experimental group learned to walk with help and to walk independently significantly faster (73.8 days and 101 days, respectively) than the control group, both of which also produced large effect size statistics for the group differences. The groups were not statistically different for rate of learning to raise self to stand but there was a moderate effect size statistic suggesting that the groups were meaningfully different in favor of the experimental group. CONCLUSIONS: These results provide evidence that, with training and support, parents can use these treadmills in their homes to help their infants with DS learn to walk earlier than they normally would. Current research is aimed at 1) improving the protocol to maximize outcome; 2) determining the impact of treadmill practice on walking gait patterns; 3) testing the application to other populations with a history of delays in walking; and 4) determining the long-term benefits that may accrue from this form of activity. motor development, Down syndrome, early intervention, walking.

Soleus H-reflex gain in elderly and young adults: modulation due to body position.

BACKGROUND: The control of posture and balance in the elderly is a primary health concern. Postural instability directly leads to a greater incidence of falling in the elderly population. One important neuromuscular mechanism instrumental in the control of posture and balance is the reflex system. The purpose of this study was to examine the gain of the soleus H-reflex in young and elderly adults in two different body positions: standing and prone. METHODS: Eighteen neurologically healthy volunteers were categorized by age in two groups: young (n = 9, mean age = 23.3 yr) and elderly (n = 9, mean age = 71.7 yr). In each position, the resting H-max/M-max ratio was determined. The gain of the reflex was also assessed by instructing the subject to perform voluntary contractions of 10, 20 and 30% of their maximum voluntary contraction, using real-time EMG biofeedback. Data were sampled on-line using custom designed software (sample rate = 2 kHz). Dependent variables included the average background EMG of the soleus muscle (40 ms window prior to stimulation) and the peak-to-peak amplitude of the elicited soleus H-reflex. To examine the gain of the reflex, the peak-to-peak amplitude of the H-reflex was plotted against the background EMG activity for each contraction intensity. RESULTS: Results indicated the following: young subjects significantly depressed the H-max/M-max ratio when standing (69.3% prone, 55.1% standing), whereas elderly subjects increased the ratio (36.1% prone, 54.5% standing). Also, the young subjects modulated the gain of the reflex from prone to standing (3.30 prone, 3.68 standing), and the elderly subjects demonstrated no gain modulation in the different body positions (2.23 prone, 1.91 standing). In both body positions the young subjects demonstrated significantly higher gain that the elderly subjects. CONCLUSIONS: The results demonstrate different control strategies for young and elderly subjects between prone and standing body positions.