Viswanath B. Unnithan

Role of cocontraction in the O2 cost of walking in children with cerebral palsy

UNLABELLED A major movement related limitation for children with spastic cerebral palsy (CP) is the compromised gait pattern, which may explain their excessive energy cost of locomotion. The aims of this study were to determine differences in the O2 cost of locomotion between children with CP (7 males, 2 females; 12.7 +/- 2.8 yr) and able-bodied controls (7 male, 1 female; 13.6 +/- 2.1 yr) and to assess the contribution that cocontraction of agonist and antagonist muscles had upon the elevated O2 cost seen in children with CP versus able-bodied controls. The treadmill submaximal walking protocol consisted of 2 x 4 min intermittent stages at 3 km.h-1 and 90% of the predetermined fastest walking speed (FWS) at 0% grade. Electromyographic data were collected during the final minute of each bout from vastus lateralis and hamstrings (thigh) and tibialis anterior and soleus (lower leg). Significant (P < 0.05) differences were noted at 3 km.h-1 for mass-relative VO2. (CP: 16.6 +/- 6.5 vs control: 10.2 +/- 1.2 ml.kg-1.min-1), % VO2max (CP: 53.5 +/- 26.0 vs CONTROL 22.5 +/- 4.93) and heart rate (CP: 143 +/- 41 vs CONTROL 91 +/- 14 beats.min-1). Thigh and lower leg muscle cocontraction accounted for 51.4% and 42.8%, respectively, of the variability in VO2 for the subjects with CP at 3 km.h-1. These results suggest that cocontraction is a major factor responsible for the higher energy cost of walking seen in children with CP.

Biological risk indicators for recurrent non-specific low back pain in adolescents

Objectives: A matched case-control study was carried out to evaluate biological risk indicators for recurrent non-specific low back pain in adolescents. Methods: Adolescents with recurrent non-specific low back pain (symptomatic; n  =  28; mean (SD) age 14.9 (0.7) years) and matched controls (asymptomatic; n  =  28; age 14.9 (0.7) years) with no history of non-specific low back pain participated. Measures of stature, mass, sitting height, sexual maturity (Tanner self assessment), lateral flexion of the spine, lumbar sagittal plane mobility (modified Schöber), hip range of motion (Leighton flexometer), back and hamstring flexibility (sit and reach), and trunk muscle endurance (number of sit ups) were performed using standardised procedures with established reliability. Backward stepwise logistic regression analysis was performed, with the presence/absence of recurrent low back pain as the dependent variable and the biological measures as the independent variables. Results: Hip range of motion, trunk muscle endurance, lumbar sagittal plane mobility, and lateral flexion of the spine were identified as significant risk indicators of recurrent low back pain (p<0.05). Follow up analysis indicated that symptomatic subjects had significantly reduced lateral flexion of the spine, lumbar sagittal plane mobility, and trunk muscle endurance (p<0.05). Conclusions: Hip range of motion, abdominal muscle endurance, lumbar flexibility, and lateral flexion of the spine were risk indicators for recurrent non-specific low back pain in a group of adolescents. These risk indicators identify the potential for exercise as a primary or secondary prevention method.

DIFFERENCES IN THORACIC KYPHOSIS AND IN BACK MUSCLE STRENGTH IN WOMEN WITH BONE LOSS DUE TO OSTEOPOROSIS

Study Design. Cross-sectional. Objectives. To determine if thoracic kyphosis was different in older women grouped based on their bone mineral density (BMD) and back extensor strength (BES), and to determine if an association between and these variables exist. Summary of Background Data. Changes in kyphosis might be related to back extensor weakness in patients with osteoporosis. Disproportionate weakness in back extensor musculature considerably increases the possibility of deformities in the fragile osteoporotic spine. Methods. A total of 189 female subjects 50 to 80 years of age were grouped by their BMD and additionally by their BES. All were evaluated for thoracic kyphosis, maximal isometric strength of the back extensors, and BMD of the lumbar spine and the hip. Results. There was no significant difference in thoracic kyphosis among all groups. Multivariate analyses of BES and BMD showed that only BES might influence thoracic kyphosis (P = 0.02). There was no correlation between BES and BMD. Statistically significant deficit in BES was observed only between the osteoporotic and osteopenic group (P < 0.05). The importance of BES in maintaining posture was observed when the study population was divided according to their BES level. With respect to thoracic kyphosis and BMD values, there were no statistical differences between strong women (BES more than 60 N) and those with medium BES (BES between 60 and 35 N). But the weakest group (BES less then 35 N) had significantly higher (P < 0.05) mean values of thoracic kyphosis in comparison to strong women (BES more than 60 N) and those with medium BES (BES between 60 and 35 N). Conclusion. The severity of thoracic kyphosis may be influenced especially by changes in BES. Therefore, provision of strong, natural extrinsic support for the spine seems to be important to decrease the incidence of spinal deformity.

Talent identification in youth soccer

Abstract The purpose of this review article was firstly to evaluate the traditional approach to talent identification in youth soccer and secondly present pilot data on a more holistic method for talent identification. Research evidence exists to suggest that talent identification mechanisms that are predicated upon the physical (anthropometric) attributes of the early maturing individual only serve to identify current performance levels. Greater body mass and stature have both been related to faster ball shooting speed and vertical jump capacity respectively in elite youth soccer players. This approach, however, may prematurely exclude those late maturing individuals. Multiple physiological measures have also been used in an effort to determine key predictors of performance; with agility and sprint times, being identified as variables that could discriminate between elite and sub-elite groups of adolescent soccer players. Successful soccer performance is the product of multiple systems interacting with one another. Consequently, a more holistic approach to talent identification should be considered. Recent work, with elite youth soccer players, has considered whether multiple small-sided games could act as a talent identification tool in this population. The results demonstrated that there was a moderate agreement between the more technically gifted soccer player and success during multiple small-sided games.

Age-Related Changes in Aerobic Capacity in Individuals with Mental Retardation: A 20-yr Review

INTRODUCTION Persons with mental retardation (MR), particularly individuals with Down syndrome (DS), have been found to have attenuated peak exercise responses in previous research. However, it is unknown if the pattern of age-associated changes in HR or aerobic capacity (VO2peak) is similar to individuals without disabilities. PURPOSE To investigate age-related changes in aerobic capacity in persons with MR, with and without DS, using a retrospective analysis. METHODS Data were collected in university research laboratories, using 180 persons with MR without DS, 133 persons with MR with DS, and 322 persons without disabilities in four age categories: 9-15, 16-21, 22-29, and 30-45 yr. Subjects underwent treadmill testing with peak HR and VO2peak measurements. RESULTS Relative VO2peak was lowest for persons with DS across all age groups. VO2peak did not change after 16 yr in the individuals with DS, whereas the other groups exhibited a slight decline (approximately 10 mL x kg(-1) x min(-1)) with age. Peak HR was overall different between all three groups (P < 0.001), and the youngest age group had the highest peak HR versus the other three age groups (P < 0.0001). CONCLUSIONS Persons with MR without DS exhibit similar age-related changes in VO2peak and peak HR as individuals without disabilities. Similar age-related changes were also observed for peak HR in individuals with DS, despite overall lower levels. However, relative VO2peak did not decline with age in persons with DS, suggesting that aerobic capacity exhibits a different age-related response in individuals with DS.

Evaluation by Exercise Testing of the Child with Cerebral Palsy

Cerebral palsy (CP) is classified as a static encephalopathy. CP is a nonprogressive disorder affecting posture and movement and is commonly associated with a spectrum of developmental disabilities. Serial testing of physiological function can provide a quantitative assessment of improvement or decline in the condition of the patient. Furthermore, there are increasing numbers of children with disability who are involved in athletic activity, and the need for physiological feedback to the disabled athlete and coach is the same as for able-bodied individuals. It is acknowledged that children and adolescents with CP have a lower maximal oxygen consumption (V̇O2max) compared with their able-bodied peers. Children with CP also have distinctly subnormal values for peak anaerobic power and muscular endurance of the upper and lower limbs. Irrespective of the scaling method used (absolute or relative), when compared with normal data from healthy controls, children with CP scored between 2 and 4 standard deviations below the expected mean value for power. Gait abnormalities in children with CP have been shown to increase submaximal walking energy expenditure almost 3-fold compared with healthy children.Assessment of the metabolic cost alone is important but does not provide any information on the mechanisms giving rise to the high energy cost of locomotion in children with CP. Hence, a multidisciplinary (kinetic, kinematic and electromyographic) approach is an important noninvasive tool for studying some of the underlying mechanisms responsible for abnormal gait and elevated energy costs.A certain level of muscle co-contraction is necessary for achieving joint stability during locomotion, particularly at the ankle and knee. There appears, however, to be a co-contraction threshold beyond which there are associated elevated metabolic costs during locomotion in children with CP.

Physical activity, metabolic issues, and assessment

Considering the important health consequences of physical activity and aerobic capacity, current guidelines recommend that all individuals should be physically active all or most days of the week. Relatively little is known about physical activity patterns or aerobic capacity of individuals who have disabilities, but existing data clearly show a disturbing pattern of low levels of physical activity and aerobic capacity in most, if not all, populations who have disabilities. More research is needed on all populations who have disabilities, not only documenting current levels of physical activity and aerobic capacity but also investigating potential strategies for improvement. Unfortunately, the techniques available for measuring physical activity have significant shortcomings. DLW shows considerable promise, but it is expensive and not appropriate for population studies. All other techniques have significant shortcomings in regard to tracking individual physical activity patterns, but they might provide valuable insight regarding group behavior. Although maximal exercise testing is the gold standard for measuring aerobic capacity, this technique is difficult to use in many populations that have disabilities. Few protocols have been validated for use with individuals who have disabilities, and indiscriminant use of protocols developed for nondisabled populations is inappropriate when testing individuals who have disabilities. Submaximal testing could be of considerable utility, but few protocols have been validated. For most populations that have disabilities, submaximal tests designed to predict VO2peak are not valid, given the altered disability-specific physiological responses, which usually result in gross overpredictions. Submaximal tests designed to compare (either intra or inter individual comparisons) physiological responses at predetermined submaximal work rates show considerable promise. Both populations of children who have disabilities that are discussed herein exhibit low levels of physical activity and aerobic capacity, which is consistent with most of the literature for any group that has disabilities. Although the mechanisms for producing lower levels of activity and aerobic capacity differ among children who have mental retardation and children who have CP, the outcome is similar in both populations. Appropriate testing methodology differs between these populations, and the different mechanisms involved demonstrate the disability-specific nature of research in children who have disabilities, which also illustrates the difficulty of producing general guidelines for exercise and physical activity interventions. Current data clearly show the need for improving both physical activity patterns and aerobic capacity in most children who have disabilities. Failure to accomplish this goal will ultimately have considerable negative health outcomes for individuals who have disabilities.

Role of mechanical power estimates in the O2 cost of walking in children with cerebral palsy.

UNLABELLED It has been established in able-bodied children that traditional biomechanical descriptors of gait such as stride length or stride frequency do not fully account for the differences seen in the energy cost of locomotion noted with age. Hence, measures of total body mechanical power output have been adopted to explain these differences. PURPOSE The aim of this study was to estimate the ability of this mechanical power calculation to explain the variability in the metabolic energy cost of treadmill walking in children with spastic cerebral palsy (CP). METHODS Thirteen subjects volunteered for the study. One group consisted of eight (6 male, 2 female) children with CP (age 12.2 +/- 2.7 yr). The second group consisted of five (4 male, 1 female) able-bodied controls (age 13.4 +/- 2.8 yr). The treadmill walking protocol consisted of one 4-min stage at 0% grade, 3 km x h(-1). Infrared markers were placed on 12 anatomical landmarks and data were collected using the OPTOTRAK motion analysis system over a 5-s time period during the last 30 s of the 4-min stage. On-line oxygen consumption VO2 measurements were obtained throughout using the Beckman Horizon Metabolic Cart. RESULTS Relative VO2 (mL x kg(-1) x min(-1)) was significantly (P < 0.05) different between the two groups (CP: 16.6 +/- 6.5 vs control: 10.2 +/- 1.2). Simple linear regression analysis demonstrated that mechanical power measurements, incorporating transfers of energy between and within adjacent body segments, accounted for 87.2% of the total variability noted in VO2 for the children with CP, compared with only 2.4% in the able-bodied subjects. CONCLUSIONS The results indicate that mechanical power differences explain the majority of the variability noted in VO2 in children with CP at a submaximal walking speed.

Experimental model of pain-free treadmill training in patients with claudication.

Mika P, Spodaryk K, Cencora A, Unnithan VB, Mika A: Experimental model of pain-free treadmill training in patients with claudication. Am J Phys Med Rehabil 2005;84:756–762. Objective:Treadmill training in claudication is often based on walking exercise to a pain threshold or longer to the maximum muscle pain of the lower limbs. This kind of exercise may cause an inflammatory response. The purpose of this study was to determine whether pain-free treadmill training using walking exercise to 85% of the distance to onset of claudication pain can significantly improve pain-free walking distance in patients with intermittent claudication and to evaluate whether this kind of program may induce an inflammatory response leading to the progression of atherosclerosis. Design:A total of 98 patients aged 50–70 yrs with stable intermittent claudication were randomized into a supervised treadmill training program or a comparison group. Patients in the treatment group participated in 12 wks of supervised treadmill training. We examined the effects of 12 wks of pain-free treadmill training on pain-free walking distance, total leukocyte count, neutrophil count, and microalbuminuria in patients with claudication. Results:A total of 80 participants completed the program. Exercise rehabilitation increased the time to onset of claudication pain by 119.2%, from 87.4 ± 38 m to 191.6 ± 94.8 m (P < 0.001). There was no increase in total leukocyte count, neutrophil count, or microalbuminuria after 12 wks of treadmill exercise (P > 0.05) Conclusion:A pain-free training program can be used in the treatment of claudication as a low-risk program, increasing walking ability without potential harmful effects of ischemia–reperfusion injury.

Effect of inspiratory muscle training intensities on pulmonary function and work capacity in people who are healthy: a randomized controlled trial

Background Inspiratory muscle training (IMT) has been shown to improve inspiratory muscle function, lung volumes (vital capacity [VC] and total lung capacity [TLC]), work capacity, and power output in people who are healthy; however, no data exist that demonstrate the effect of varying intensities of IMT to produce these outcomes. Objectives The purpose of this study was to evaluate the impact of IMT at varying intensities on inspiratory muscle function, VC, TLC, work capacity, and power output in people who are healthy. Design This was a randomized controlled trial. Setting The study was conducted in a clinical laboratory. Participants Forty people who were healthy (mean age=21.7 years) were randomly assigned to 4 groups of 10 individuals. Interventions Three of the groups completed an 8-week program of IMT set at 80%, 60%, and 40% of sustained maximum inspiratory effort. Training was performed 3 days per week, with 24 hours separating training sessions. A control group did not participate in any form of training. Measurements Baseline and posttraining measurements of body composition, VC, TLC, inspiratory muscle function (including maximum inspiratory pressure [MIP] and sustained maximum inspiratory pressure [SMIP]), work capacity (minutes of exercise), and power output were obtained. Results The participants in the 80%, 60%, and 40% training groups demonstrated significant increases in MIP and SMIP, whereas those in the 80% and 60% training groups had increased work capacity and power output. Only the 80% group improved their VC and TLC. The control group demonstrated no change in any outcome measures. Limitations This study may have been underpowered to demonstrate improved work capacity and power output in individuals who trained at 40% of sustained maximum inspiratory effort. Conclusion High-intensity IMT set at 80% of maximal effort resulted in increased MIP and SMIP, lung volumes, work capacity, and power output in individuals who were healthy, whereas IMT at 60% of maximal effort increased work capacity and power output only. Inspiratory muscle training intensities lower than 40% of maximal effort do not translate into quantitative functional outcomes.