Evaluation of energy expenditure in children with cerebral palsy using a multi-sensor accelerometer.

AIM: The aim of this paper was to evaluate the validity and reliability of a multisensor accelerometer, the Intelligent Device for Energy Expenditure and Activity (IDEEA, MiniSun, CA), for measuring energy expenditure in children with cerebral palsy (CP). Twenty-one children with CP, age range 4-10 years, with varying degrees of impairment, were recruited for the study. In addition, 7 children with normal development, age range 5.67-8.5 years, were also tested. METHODS: Children were connected to a portable metabolic cart (Cosmed, Rome, Italy) and to the IDEEA by five sensors. Children were asked to perform a series of activities simulating everyday activity, walk on a treadmill for 4 min and climb a staircase for 4 min. During all activities oxygen consumption values were measured and converted to energy units. Energy expenditure as measured by the IDEEA was also recorded. RESULTS: During the simulation of daily activities and during walking at a comfortable speed the IDEEA significantly overestimated the energy expenditure. However significant and relatively high positive correlations (0.70-0.97) were found between the two instruments. Inconsistent results were obtained during walking at increased speed. During a step test similar means were found by the two instruments for children with normal development and children with CP with good correlations between the values measured by the two instruments. Energy expenditure measurement in children with CP were found to be very reliable, with a correlation of 0.998 for repeated measurements during treadmill walking. CONCLUSION: It seems IDEEA, with its present conversion equations, is not suitable for exact evaluation of energy expenditure in children with CP or in young children with normal development. However, in light of the good correlation with the standard method of evaluating energy expenditure and the high test-retest reliability of the IDEEA's measurements, It is suggested that IDEEA may be a valuable tool for clinical follow-up of children with CP for quantitative evaluation of the efficacy of treatment interventions. The establishment of population specific conversion equations is expected to significantly increase the accuracy of energy expenditure evaluation by the IDEEA.

Random perturbation: a potential aid in treatment of children with cerebral palsy.

BACKGROUND AND PURPOSE: The motor behaviour of children with cerebral palsy (CP) can be viewed in terms of a stable mode with very little flexibility that prevents adaptation to tasks. We hypothesized that the use of random perturbations (RP) would weaken excessive stability, introduce flexibility and enhance the effects of physical treatment. The objective was to evaluate the contribution of RP to gross motor function and mechanical efficiency (MEg) during intensive physiotherapy in children with CP. METHODS: A convenience sample of 20 children with CP (mean age 8.2, range: 5.9-12.9 yrs) were matched by age and GMFCS level, and randomly assigned to structured intensive treatment (SIT) or to SIT + RP groups. Groups received one month of daily treatment. RP was applied by engine-induced random passive cycling for upper and lower limbs for up to 10 min in a 90-min treatment session. Gross Motor Function Measure (GMFM)-66 and gross mechanical efficiency (MEg) during stair climbing (MEg) were measured before and after treatment. RESULTS: GMFM-66 scores increased by about 1.0 in both groups. However, external work and MEg increased significantly more in SIT + RP than SIT. The increase in MEg in SIT + RP was independent of the level of motor function at baseline. CONCLUSION: The addition of RP in treatment of children with CP may have weakened previously established stereotypical motor patterns and introduced flexibility, thereby improving mechanical efficiency of a complex motor task. RP may enhance the effects of intensive treatment.

The cumulative heat strain index--a novel approach to assess the physiological strain induced by exercise-heat stress.

The cumulative heat strain index (CHSI) is a new approach for assessing the total physiological strain experienced by subjects exposed to an exercise-heat stress. The index is based on inherent physiological logic that combines the thermoregulatory strain, which is described by the area under the hyperthermic curve, and the circulatory strain, which is characterized by heart-beat count. According to this model, the index reflects the dynamics of changes in the thermoregulatory and cardiovascular components and accounts for the complementary nature of the interaction between them. Mathematically, the index is calculated as follows: CHSI =[ sigma(0-t) hb-fc(0) x t] x l0(-3) x [ integral (0-t) Tre x dt-Tre(0) x t] (units) Where: hb=heart beats, fc(0)=initial lowest heart rate (bpm), Tre = rectal temperature (Tre(0) = baseline Tre) (degrees C) and t = time (min) from the onset of measurements. Four sets of data, from various former studies, have been used to demonstrate the index's applicability and its sensitivity to differentiate between levels of stain under various stressful conditions (e.g. clothing insulation, acclimation to heat and levels of tolerance to heat). In all cases, the index was found to be a sensitive tool for assessing the level of strain. Furthermore, the CHSI can be used to predict potential strain. The index's high sensitivity arises from its nature, which reflects miniature differences in the pattern of changes in the dynamics of physiological responses and therefore is a powerful and practical tool for evaluating even minor changes in strain.

Changes in heart rate variability following acclimation to heat.

We studied the sympatho-vagal balance during acclimation to heat in eight healthy individuals. The subjects, dressed in shorts and tennis shoes, underwent a 10 d procedure of acclimation. Daily exposure lasted 115 min--5 min rest followed by 2 bouts of 50 min exercise (walking on a treadmill at a work load of approximately 350 watt) separated by 10 min rest-at 40 degrees C and 40% relative humidity. We analyzed the time and frequency domains of 256 R-R intervals, toward the end of the second bout of exercise, on the first and tenth days of acclimation. Typical changes for heat acclimation (a reduction in rectal temperature and heart rate, an increase in sweat rate) were observed. Concomitant to a decrease in the final heart rate on the tenth day, sympathetic tone increased. We suggest that, except for the chronotropic response, changes in the sympatho-vagal balance may reflect several adaptive mechanisms of the cardiovascular system. Peripheral factors rather than intrinsic cardiac factors are of relatively greater importance in the direct control of cardiac function.