Squat test performance and execution in children with and without cerebral palsy

BACKGROUND

Knowledge on lower extremity strength is imperative to informed decision making for children with cerebral palsy (CP) with mobility problems. However, a functional and clinically feasible test is not available. We aimed to determine whether the squat test is suitable for this purpose by investigating test performance and execution in children with cerebral palsy and typically developing (TD) peers.

METHODS

Squat test performance, defined by the number of two-legged squats until fatigue (max 20), was assessed in twenty children with bilateral CP (6-19years; gross motor function classification system I-III) and sixteen TD children (7-16years). Muscle fatigue was assessed from changes in electromyography (EMG). Joint range-of-motion and net torque were calculated for each single squat, to investigate differences between groups and between the 2nd and last squat.

FINDINGS

Fifteen children with CP performed <20 squats (median=13, IQR=7-19), while all TD children performed the maximum of 20 squats. Median EMG frequency decreased and amplitude increased in mm. quadriceps of both groups. Ankle and knee range-of-motion were reduced in children with CP during a single squat by 10 to 15°. No differences between 2nd and last squat were observed, except for knee range-of-motion which increased in TD children and decreased in children with CP.

INTERPRETATION

Squat test performance was reduced in children with CP, especially in those with more severe CP. Muscle fatigue was present in both children with CP and TD peers, confirming that endurance of the lower extremity was tested. Minor execution differences between groups suggest that standardized execution is important to avoid compensation strategies. It is concluded that the squat test is feasible to test lower extremity strength in children with CP in a clinically meaningful way. Further clinimetric evaluation is needed before clinical implementation.

A randomized controlled trial studying efficacy and tolerance of a knee-ankle-foot orthosis used to prevent equinus in children with spastic cerebral palsy

Objective:

To examine whether using a knee-ankle-foot orthosis helps maintain ankle-foot dorsiflexion range of motion over time.

Design:

A multicentre randomized controlled trial.

Setting:

Two hospitals and one rehabilitation centre in the Netherlands and the USA.

Subjects:

Children (4-16 years old) with spastic cerebral palsy who were able to walk.

Intervention:

Use of a knee-ankle-foot orthosis, equipped with an Ultraflex® ankle power unit, for at least 6 hours every other night for one year.

Main measures:

Primary outcome measure: ankle-foot dorsiflexion range of motion. Secondary outcome measures: ankle-foot and knee angle in gait and gross motor function. Wearing time was also measured. Measurements were taken at baseline and at 3, 6, 9 and 12 months.

Results:

28 children (experimental group: n=15, control group: n=13) participated in the study. 11 participants (experimental: n=4, control: n=7) did not complete all five measurements, as they needed additional treatment. No significant difference was found in the decrease of ankle-foot dorsiflexion range of motion between the experimental and control groups (difference: −1.05°, 95% confidence interval: −4.71° – 2.61°). In addition, secondary outcome measures did not show differences between groups. Despite good motivation, knee-ankle-foot orthosis wearing time was limited to a mean±SD of 3.2±1.9 hours per prescribed night due to discomfort.

Conclusions:

Knee-ankle-foot orthosis with dynamic ankle and fixed knee are poorly tolerated and are not beneficial in preventing a reduction in ankle-foot dorsiflexion range of motion in children with spastic cerebral palsy, at least with limited use.

Energy cost of walking in children with spastic cerebral palsy: relationship with age, body composition and mobility capacity

The energy cost (EC) of walking is different for typically developing (TD) and children with cerebral palsy (CP). The associated factors of EC are not fully understood in children with CP. We assessed the relationship between EC and age, body surface area (BSA), and gross motor function measure (GMFM). We retrospectively examined data collected between 2003 and 2011 on 276 children aged 4-18 years who were classified as Gross Motor Function Classification System level I, n=79; II, n=123; and III, n=74. Energy cost was assessed while children walked 6-8 min at a comfortable, self-selected speed using their typical walking aids and/or orthoses as part of a clinical gait analysis. During the test, participants wore a breath-by-breath portable gas analysis system, measuring oxygen consumption. To calculate EC (J/kg/m), oxygen consumption was converted to J/kg/min and divided by walking speed. Data were analyzed using linear regression model. Energy cost correlated inversely with age (β=-0.16, R2=0.02, P=0.01), BSA (β=-3.35, R2=0.11, P<0.0001), and GMFM (β=-0.12, R2=0.42, P<0.0001). In the multiple linear regression model, GMFM was the most potent correlate of EC, BSA explained another 10% of the variance (R2=0.53), and age was a marginally significant correlate of EC (P=0.08). In summary, in children with CP in our study, EC decreased as GMFM and BSA increased, and GMFM was the most potent correlate of EC.

Cognitive precursors of arithmetic development in primary school children with cerebral palsy

The aim of this study was to examine the development of arithmetic performance and its cognitive precursors in children with CP from 7 till 9 years of age. Previous research has shown that children with CP are generally delayed in arithmetic performance compared to their typically developing peers. In children with CP, the developmental trajectory of the ability to solve addition- and subtraction tasks has, however, rarely been studied, as well as the cognitive factors affecting this trajectory. Sixty children (M=7.2 years, SD=.23 months at study entry) with CP participated in this study. Standardized tests were administered to assess arithmetic performance, word decoding skills, non-verbal intelligence, and working memory. The results showed that the ability to solve addition- and subtraction tasks increased over a two year period. Word decoding skills were positively related to the initial status of arithmetic performance. In addition, non-verbal intelligence and working memory were associated with the initial status and growth rate of arithmetic performance from 7 till 9 years of age. The current study highlights the importance of non-verbal intelligence and working memory to the development of arithmetic performance of children with CP.

Feasibility and test-retest reliability of measuring lower‑limb strength in young children with cerebral palsy

BACKGROUND

Quantifying leg muscle strength in young children with cerebral palsy (CP) is essential for identifying muscle groups for treatment and for monitoring progress.

AIM

To study the feasibility, intratester reliability and the optimal test design (number of test occasions and repetitions) of measuring lower-limb strength with handheld dynamometry (HHD) and dynamic ankle plantar flexor strength with the standing heel-rise (SH) test in 3-10 year aged children with CP.

DESIGN

Test-retest design.

SETTING

Rehabilitation centre, special needs school for children with disabilities, and university medical centre.

METHODS

Knee extensor, hip abductor and calf muscle strength was assessed in 20 ambulatory children with spastic CP (3-5 years [N.=10] and 6-10 years [N.=10]) on two test occasions. Intraclass correlation coefficients (ICC) and Smallest Detectable Differences (SDD) were calculated to determine the optimal test design for detecting changes in strength.

RESULTS

All isometric strength tests had acceptable SDDs (9-30%), when taking the mean values of 2-3 test occasions (separate days) and 2-3 repetitions. The one-leg SH test had large SDDs (40-128% for younger group, 23-48% for older group).

CONCLUSION

Isometric strength (improvements) can only be measured reliably with HHD in young children with CP when the average values over at least 2 test occasions are taken. Reliability of the SH test is not sufficient for measuring individual changes in dynamic muscle strength in the younger children.

CLINICAL REHABILITATION IMPACT

Results of this study can be used to determine the optimal number of test occasions and repetitions for reliable HHD measurements depending on expected changes, muscle group and age in 3-10 year old children with CP.

Association between isometric muscle strength and gait joint kinetics in adolescents and young adults with cerebral palsy

The purpose of this study was to determine the association between isometric muscle strength of the lower limbs and gait joint kinetics in adolescents and young adults with cerebral palsy (CP). Twenty-five participants (11 males) with bilateral spastic CP, aged 14-22 years (mean: 18.9, sd: 2.0 yr) and Gross Motor Function Classification System (GMFCS) level II (n=19) and III (n=6) were tested. Hand held dynamometry was used to measure isometric strength (expressed in Nm/kg) of the hip, knee, and ankle muscles using standardized testing positions and procedures. 3D gait analysis was performed with a VICON system to calculate joint kinetics in the hip, knee and ankle during gait. Ankle peak moments exceeded by far the levels of isometric strength of the plantar flexors, while the knee and hip peak moments were just at or below maximal isometric strength of knee and hip muscles. Isometric muscle strength showed weak to moderate correlations with peak ankle and hip extension moment and power during walking. Despite considerable muscle weakness, joint moment curves were similar to norm values. Results suggest that passive stretch of the muscle-tendon complex of the triceps surae contributes to the ankle moment during walking and that muscle strength assessment may provide additional information to gait kinetics.

Physical fitness, everyday physical activity, and fatigue in ambulatory adults with bilateral spastic cerebral palsy

This study assessed physical fitness and its relationships with everyday physical activity (PA) and fatigue in cerebral palsy (CP). Participants were 42 adults with ambulatory bilateral spastic CP (mean age 36.4 ± 5.8 years; 69% males; 81% with good gross motor functioning). Progressive maximal aerobic cycle tests determined VO(2peak) (L/min). Objective levels of everyday PA were measured with accelerometry and self-reported levels of everyday PA with the Physical Activity Scale for Individuals with Physical Disabilities. Fatigue was assessed with the Fatigue Severity Scale. The average aerobic capacity of adults with CP was 77% of Dutch reference values. Participants were physically active during 124 min/day (85% of Dutch reference values), and half experienced fatigue. In women, lower physical fitness was related to lower self-reported levels of PA (R(p)=0.61, P=0.03), and in men to higher levels of fatigue (R(p)=-0.37, P=0.05). Other relationships were not significant. Results suggest that ambulatory adults with CP have low levels of physical fitness, are less physically active than able-bodied age mates and often experience fatigue. We found little evidence for relationships between the level of physical fitness and everyday PA or fatigue.

Development and validation of prognostic models designed to predict wheelchair skills at discharge from spinal cord injury rehabilitation

Objective: To develop and validate a statistical model to predict wheelchair skills at discharge (t 2) from personal and lesion characteristics and wheelchair skills at the start of spinal cord injury inpatient rehabilitation (t1).

Design: Prospective cohort study

Setting: Eight Dutch rehabilitation centres.

Subjects: One hundred and forty-two patients with a spinal cord injury.

Main measures: Models were developed with the performance time and ability score at t2 as dependent variables and t1 scores of performance time and ability score, age, gender, body mass index, level and completeness of the lesion as independent variables. The statistical models were evaluated by comparing individual estimated scores with actual measured scores.

Results: The main independent variables to predict wheelchair skills at discharge were the t1 performance time and ability score, age, gender and lesion level. The intraclass correlation coefficient between the estimated and actual ability score was 0.79 and for the performance time 0.86. However, the 95% limits of agreement and their confidence intervals were relatively wide for both ability score (—2.3 to 3.4, range 0—8) and performance time (—12.5 to 8.2, range 11—40 seconds).

Conclusion: The prognostic models developed in this study to predict future wheelchair skills might help planning the course of rehabilitation. The models should be used with caution in daily clinical practice, but may add useful information to clinical expertise and knowledge of the individual patient.

The longitudinal relationship between lipid profile and physical capacity in persons with a recent spinal cord injury

STUDY DESIGN

A multicenter prospective cohort study.

OBJECTIVE

To determine the longitudinal relationship between physical capacity and lipid profile in persons with spinal cord injury (SCI) during and 1 year after rehabilitation.

SETTING

Eight Dutch rehabilitation centers with a specialized SCI unit.

METHODS

A total of 206 subjects with SCI (78 with tetraplegia) participated. The longitudinal relationship between lipid profiles (total cholesterol (TC), high- (HDL) and low-density lipoprotein (LDL) and triglycerides (TG) and physical capacity (peak power output (POpeak), peak oxygen uptake (VO2peak), and muscle strength) was investigated during inpatient SCI rehabilitation (start, 3 months later, discharge) and 1 year after discharge. A correction was made for the possible confounding variables age, body mass index, gender, time since injury, lesion level and completeness.

RESULTS

HDL and the ratios LDL/HDL and TC/HDL showed a significant and favorable relationship with VO2peak, POpeak and muscle strength. TG was positively related to POpeak and muscle strength.

CONCLUSIONS

More favorable lipid profiles were seen in people with a higher physical capacity after correction for personal and lesion characteristics. Therefore, improving the physical capacity by being active during daily life or in sport may further improve the lipid profile and thus reduce the risk for coronary heart disease.

Mechanical Efficiency and Wheelchair Performance during and after Spinal Cord Injury Rehabilitation

The purpose of the present study was to investigate whether mechanical efficiency (ME) relates to wheelchair propulsion capacity and wheelchair performance tasks during and after rehabilitation of people with a spinal cord injury (SCI). Eighty participants with a SCI were tested during rehabilitation (3 x) and 1 year after discharge. Two 3-minute submaximal exercise blocks, a maximal wheelchair exercise test, and four wheelchair performance tasks were performed. ME, peak power output (PO (peak)), the sum of the performance times of a 15-m sprint and figure-of-eight, and the heart rate reserve (%HRR) during 10 s of wheelchair propulsion on a 3 % and 6 % slope were calculated. The relationship between ME and PO (peak), %HRR and performance time was tested with a multilevel regression analysis. ME showed a significant relationship with PO (peak) (p </= 0.002). A 1 % higher ME related to a 1.6 - 2.2 W higher PO (peak). ME of exercise block 2 was related to the sum of the performance times of a 15-m sprint and figure-of-eight; the tests were performed faster by participants with a higher ME. No relationship was found between ME and %HRR during wheelchair propulsion on a slope. ME showed a significant effect on wheelchair propulsion capacity and wheelchair performance time during and 1 yr after SCI rehabilitation although the isolated effect of ME is small.

Motor outcome at the age of one after perinatal hypoxic-ischemic encephalopathy

OBJECTIVE

The aim of this report is to describe the motor outcome in one year-old children who were born at full-term with perinatal hypoxic-ischemic encephalopathy (HIE). Relationships between motor ability tests and neurological examination at one year, and between these tests and neonatal brain magnetic resonance imaging (MRI) were investigated.

PARTICIPANTS AND METHODS

32 surviving children, born full-term with perinatal HIE, are included in this report. All children had a neonatal MRI. At one year, motor ability was assessed with the Alberta Infant Motor Scale and the Bayley Scales of Infant Development (2nd version). Neurological examinations included the neurological optimality score (NOS).

RESULTS

At one year, 14 children (44%) had normal motor ability, nine (28%) had mildly delayed, and nine had significantly delayed motor ability. The NOS ranged from 14.6-27 points. All children with normal motor ability had (near) optimal NOS, however, not all children with high NOS had normal motor ability. Eleven children (34%) had normal neonatal MRI; at one year, six of them had normal, and five had mildly delayed motor ability. Eight children with normal motor ability showed abnormalities on neonatal MRI.

CONCLUSION

Neonatal brain MRI does not predict motor outcome at one year. Motor ability tests and neurological examinations should be used in a complementary manner to describe outcome after HIE.

The individual relationship between heart rate and oxygen uptake in people with a tetraplegia during exercise

STUDY DESIGN

Descriptive study.

OBJECTIVE

To examine the individual heart rate-oxygen uptake (HR-VO(2)) relationship during exercise in persons with tetraplegia (TP).

SETTING

Rehabilitation Centre Heliomare, Wijk aan Zee, The Netherlands.

METHODS

The HR-VO(2) relationship was determined in untrained subjects with motor complete TP (C5 or C6, n=10 and C7 or C8, n=10) during a discontinuous graded exercise hand cycle test. The mean HR and VO(2) of the final 60 s of 2-min exercise blocks were used for calculation of the individual correlation coefficient and the standard error of the estimate (SEE).

RESULTS

Two subjects of the C5-C6 group were not able to complete the test. Individual Pearson's correlation coefficients (r) ranged from 0.68 to 0.97 and SEE from 2.6 to 22.4% VO(2)-Reserve (VO(2)R). The mean Pearson's r and SEE were 0.81+/-0.12 and 10.6+/-5.6% VO(2)R in the C5-C6 group and 0.91+/-0.07 and 7.0+/-3.2% VO(2)R in the C7-C8 group, respectively. Two subjects of the C5-C6 group and six subjects of the C7-C8 group attained a linear HR-VO(2) relationship with an acceptable SEE (< or =6.0%) and r (>0.90).

CONCLUSIONS

The HR-VO(2) relationship appeared linear in only eight out of 18 subjects. An individual analysis of the HR-VO(2) relationship is necessary to determine whether HR can be used to quantify exercise intensity. The use of HR to prescribe training intensity should be reconsidered in persons with TP.

SPONSORSHIP

This study is supported from a grant by ZON-MW.

Demographics of the Dutch multicenter prospective cohort study 'Restoration of mobility in spinal cord injury rehabilitation'

STUDY DESIGN

A multicenter prospective cohort study.

OBJECTIVE

To compare the demographic data of the included population with other studied spinal cord injury (SCI) populations in the international literature.

SETTING

Eight Dutch rehabilitation centers with a specialized SCI unit.

METHODS

A total of 205 individuals with SCI participated in this study. Information about personal, lesion and rehabilitation characteristics were collected at the beginning of active rehabilitation by means of a questionnaire.

RESULTS

The research group mainly consisted of men (74%), of individuals with a paraplegia (59%), and had a complete lesion (68%). The SCI was mainly caused by a trauma (75%), principally due to a traffic accident (42%). The length of clinical rehabilitation varied between 2 months and more than a year, which seemed to be dependent on the lesion characteristics and related comorbidity.

CONCLUSIONS

The personal and lesion characteristics of the subjects of the multi-center study were comparable to data of other studies, although fewer older subjects and subjects with an incomplete lesion were included due to the inclusion criteria 'age' and 'wheelchair-dependent'. The length of stay in rehabilitation centers in The Netherlands was longer compared to Denmark but much longer than in eg Australia and the USA.

Upper extremity musculoskeletal pain during and after rehabilitation in wheelchair-using persons with a spinal cord injury

STUDY DESIGN

Prospective cohort study.

OBJECTIVES

To study upper extremity musculoskeletal pain during and after rehabilitation in wheelchair-using subjects with a spinal cord injury (SCI) and its relation with lesion characteristics, muscle strength and functional outcome.

SETTING

Eight rehabilitation centers with an SCI unit in the Netherlands.

METHODS

Using a questionnaire, number, frequency and seriousness of musculoskeletal pain complaints of the upper extremity were measured. A pain score for the wrist, elbow and shoulder joints was calculated by multiplying the seriousness by the frequency of pain complaints. An overall score was obtained by adding the scores of the three joints of both upper extremities. Muscle strength was determined by manual muscle testing. The motor score of the functional independence measure provided a functional outcome. All outcomes were obtained at four test occasions during and 1 year after rehabilitation.

RESULTS

Upper extremity pain and shoulder pain decreased over time (30%) during the latter part of in-patient rehabilitation (P<0.001). Subjects with tetraplegia (TP) showed more musculoskeletal pain than subjects with paraplegia (PP) (P<0.001). Upper extremity pain and shoulder pain were significantly inversely related to functional outcome (P<0.001). Muscle strength was significantly inversely related to shoulder pain (P<0.001). Musculoskeletal pain at the beginning of rehabilitation and BMI were strong predictors for pain 1 year after in-patient rehabilitation (P<0.001).

CONCLUSIONS

Subjects with TP are at a higher risk for upper extremity musculoskeletal pain and for shoulder pain than subjects with PP. Higher muscle strength and higher functional outcome are related to fewer upper extremity complaints.

A physiological comparison of synchronous and asynchronous hand cycling

The purpose of this study was to compare submaximal physiological responses (oxygen uptake, ventilation, heart rate) and gross mechanical efficiency between synchronous and asynchronous hand cycling at different cadences. Thirteen non-disabled men (22.4 +/- 1.6 yr) performed two submaximal exercise tests on a treadmill, using synchronous and asynchronous crank settings in counter balanced order. Tests were performed using a commercially available hand cycle unit that was attached to a hand rim wheelchair. Each test consisted of five 5-min exercise bouts at 36, 47, 55, 65, and 84 rpm. ANOVA for repeated measures showed a significant effect of crank mode (p < 0.001) and cadence (p < 0.001), as well as an interaction effect between both (p < 0.01). Physiological responses were lower, and efficiency higher, in synchronous versus asynchronous hand cycling at all cadences. Post-hoc analysis of the (overall) effect of cadence showed significantly higher physiological responses and lower efficiency at the higher (84 vs. 65 rpm and 65 vs. 55 rpm) and lower (36 vs. 47 rpm) cadences. The interaction effect indicates that the effect of crank mode was dependent on cadence, showing a larger difference between synchronous and asynchronous hand cycling at 84 vs. 65 rpm and at 36 vs. 47 rpm. It is concluded that, in contrast to previous results in arm crank ergometry, synchronous hand cycling is less strenuous and more efficient than asynchronous hand cycling.

Submaximal physical strain and peak performance in handcycling versus handrim wheelchair propulsion

STUDY DESIGN

Experimental study in subjects with paraplegia and nondisabled subjects.

OBJECTIVE

To compare submaximal physical strain and peak performance in handcycling and handrim wheelchair propulsion in wheelchair-dependent and nondisabled control subjects

SETTING

Amsterdam, The Netherlands.

METHODS

Nine male subjects with paraplegia and 10 nondisabled male subjects performed two exercise tests on a motor-driven treadmill using a handrim wheelchair and attach-unit handcycle system. The exercise protocol consisted of two 4-min submaximal exercise bouts at 25 and 35 W, followed by 1-min exercise bouts with increasing power output until exhaustion.

RESULTS

Analysis of variance for repeated measures showed a significantly lower oxygen uptake (VO2), ventilation (Ve), heart rate (HR), rate of perceived exertion and a higher gross efficiency for handcycling at 35 W in both subject groups, while no significant differences were found at 25 W. Peak power output and peak VO2, Ve and HR were significantly higher during handcycling in both groups. The differences between handcycling and wheelchair propulsion were the same in subjects with paraplegia and the nondisabled subjects.

CONCLUSIONS

Handcycling induces significantly less strain at a moderate submaximal level of 35 W, and shows noticeably higher maximal exercise responses than wheelchair propulsion, which is consistent in subjects with paraplegia and nondisabled controls. These results demonstrate that handcycling is beneficial for mobility in daily life of wheelchair users.

Biomechanics and physiology in active manual wheelchair propulsion

Manual wheelchair propulsion in daily life and sports is increasingly being studied. Initially, an engineering and physiological perspective was taken. More recently a concomitant biomechanics interest is seen. Themes of biomechanical and physiological studies today are performance enhancing aspects of wheelchair use and the ergonomics of wheelchair design. Apart from the propulsion technique the focus of biomechanics research of manual wheelchair propulsion is mainly towards injury mechanisms, especially phenomena of overuse to the upper extremity. Obviously, the vehicle mechanics of wheelchairs must be included within this biological framework. Scientific research is progressing, but is still hampered by methodological limitations, such as the heterogeneity and small numbers of the population at study as well as the inconsistency of employed technologies and methodologies. There is a need for consensus regarding methodology and research strategy, and a strong need for collaboration to improve the homogeneity and size of subject groups and thus the power of the experimental results. Thus a sufficiently strong knowledge database will emerge, leading to an evidence-base of performance enhancing factors and the understanding of the risks of wheelchair sports and long-term wheelchair use. In the light of the current biomechanical and physiological knowledge of manual wheelchair propulsion there seems to be a need for the stimulation of other than hand rim propelled manual wheelchairs.

Health related functional status in men with spinal cord injury: relationship with lesion level and endurance capacity

STUDY DESIGN

Cross-sectional study.

OBJECTIVES

To determine the relationship of health related functional status with lesion level and endurance capacity in persons with spinal cord injury (SCI).

METHODS

Thirty-seven men with SCI were divided in four lesion groups: high tetraplegia (motor complete; C5-C6, n=10), low tetraplegia (motor complete, C6/7-C8, n=9), motor incomplete tetraplegia (n=7), and paraplegia (n=11). Health related functional status was measured with the short version of the Sickness Impact Profile (SIP68), including a physical (SOM), psychological (PSY) and social subscore (SOC). Endurance capacity, defined as maximal power output (PO(max)) and peak oxygen uptake (VO(2peak)), was measured in a maximal exercise test on a wheelchair ergometer.

RESULTS

Total SIP68-score and SOM were significantly different between lesion groups, showing higher values in the high- and low-tetraplegia group. There were no differences between lesion groups for PSY and SOC subscores. VO(2peak) and PO(max) were significantly higher in the paraplegia group, compared to the high and low tetraplegia groups. VO(2peak) was also higher in the motor incomplete versus other tetraplegia groups. Significant Spearman correlation coefficients were found for VO(2peak) and PO(max) with SIP68 and SOM (ranging from -0.68 to -0.79) and SOC (ranging from -0.39 to -0.51). No significant relationship was found with PSY. Hierarchical regression analysis showed that after correction for lesion level, 22% of the variance of SIP68, 8% of the variance of SOM, and 30% of the variance of SOC was explained by PO(max) or VO(2peak).

CONCLUSIONS

Results indicate that there is an evident relationship between the physical dimensions of health related functional status and lesion level, but not for the psychological and social dimensions. After controlling for lesion level a significant amount of the variance of health related functional status can be explained by endurance capacity parameters. Although no causal relationships can be established in this cross-sectional study, these results suggest that functional status may be improved by increasing the endurance capacity.

Alternative modes of manual wheelchair ambulation: an overview

An estimated 90% of all wheelchairs are hand-rim propelled, a physically straining form of ambulation that can lead to repetitive strain injuries in the arms and, eventually, to secondary impairments and disability. Further disability in wheelchair-dependent individuals can lead to a sedentary lifestyle and thereby create a greater risk for cardiovascular problems. Studies on lever-propelled and crank-propelled wheelchairs have shown that these propulsion mechanisms are less straining and more efficient than hand-rim-propelled wheelchairs. This article reviews these studies and substantiates that the frequent use of these alternative propulsion mechanisms may help prevent some of the secondary impairments that are seen among today's wheelchair-user population.

Physical capacity and race performance of handcycle users

The purpose of this study was to determine physical capacity, gross efficiency (GE), and physical strain (PS) of 16 male handcycle users during a 10K race, and to relate these to race performance. All subjects used a handcycle system attached to their own wheelchair and were classified into a group with (A1/A2; N=10) and without (A3; N=6) upper-limb impairments. The PS was defined as the mean heart rate during the race, expressed relative to the heart rate reserve (%HRR). Race performance was defined as the mean race velocity (Vrace). Maximal power output (POmax), VO2peak, and GE (at 28 W) were determined in a graded treadmill exercise test. POmax (55+/-25 versus 129+/-26 W), VO2peak (1.11+/-0.4 versus 2.12+/-0.4 L x min(-1)) and Vrace (13.6+/-3 versus 19.9+/-3 km x hr(-1)) were different between A1/A2 and A3 (p<0.001), whereas PS (80+/-9 versus 88+/-9 %HRR; p=0.12) and GE (10.9+/-1.4 versus 9.7+/-0.9%; p=0.09) were not. POmax, VO2peak, and PS were associated (p<0.05) with Vrace (R=0.91, 0.90, and 0.66). Regression analysis showed that after VO2peak, GE added another 9 percent to the explanation of the variance of Vrace (R2=0.89). In conclusion, attainable handcycling POmax is markedly high and strongly related to race performance. The high PS during the race suggests that handcycling is well suited for aerobic training for most groups of wheelchair users.

Altered contractile properties of the quadriceps muscle in people with spinal cord injury following functional electrical stimulated cycle training

STUDY DESIGN

A longitudinal training study.

OBJECTIVES

To assess if contractile speed and fatigability of paralysed quadriceps muscles in individuals with spinal cord injury (SCI) can be altered by functional electrical stimulation leg cycle ergometry (FES-LCE) training.

SETTINGS

The Sint Maartenskliniek rehabilitation centre and the University of Nijmegen, Nijmegen, the Netherlands.

METHODS

Contractile properties of the quadriceps muscle were studied in seven people with motor-complete SCI who participated in a FES-LCE training program. Subjects trained for 30 min, three times per week for 6 weeks. Contractile speed and fatigue characteristics of electrically stimulated isometric contractions were compared before and after 6 weeks of FES-LCE.

RESULTS

Fatigue resistance improved following FES-LCE training as indicated by the higher forces maintained in response to repetitive electrical stimulation. In contrast with an improved fatigue resistance, the maximal rate of force rise was unaffected, the speed of relaxation increased and the fusion of a 10 Hz force signal decreased. Furthermore, the force-frequency relationship shifted to the right at low stimulation frequencies, indicated by a decline in the ratio of 1 and 100 Hz force responses as well as the ratio of 10 and 100 Hz force responses.

CONCLUSION

FES-LCE training can change the physiological properties of the quadriceps muscle in people with SCI. Even after a short period of training, the stimulated muscles become more resistant to fatigue. Furthermore, the increased speed of relaxation and associated decreased fusion and altered force-frequency relationship following training may be related to adaptations in the calcium handling processes, which reflect an early response of long-term disused muscles.

Physical performance during rehabilitation in persons with spinal cord injuries

PURPOSE

The objective of the present study was to evaluate the effect of rehabilitation on physical capacity, mechanical efficiency of manual wheelchair propulsion, and performance of standardized activities of daily living (ADL).

METHODS

Nineteen recently injured subjects with spinal cord injuries were tested on a wheelchair ergometer (maximal isometric strength, sprint and maximal power output, and peak oxygen uptake) and during standardized ADL (physical strain and performance time) at the beginning (t1) and at the end (t2) of the active rehabilitation period.

RESULTS

Paired Student t-tests showed significant increases for maximal isometric strength (24%, P < 0.01), sprint power output (l7%, P < 0.001) and maximal power output (38%, P < 0.001). Peak oxygen uptake showed no statistically significant improvement (11%, P = 0.06). Mechanical efficiency of submaximal wheelchair exercise was significantly higher at t2 (9.0%) compared to t1 (7.9%, P < 0.01). No significant differences were found for physical strain during ADL, except for passing a door (P < 0.05). Performance time showed a significant decrease for most tasks.

CONCLUSIONS

The results of this study show considerable improvements in physical capacity and mechanical efficiency of manual wheelchair propulsion during rehabilitation, and a concomitant lower performance time during standardized ADL. The higher mechanical efficiency and the decrease in performance time during standardized ADL suggest improvement in wheelchair propulsion technique.

Physical performance in persons with spinal cord injuries after discharge from rehabilitation

PURPOSE

The purpose of this study was to investigate changes in physical capacity and performance of activities of daily living (ADL) during the postrehabilitation period of persons with spinal cord injuries and to determine the factors explaining the changes in physical capacity.

METHODS

Nine subjects with tetraplegia and 11 subjects with paraplegia were measured at time of discharge from rehabilitation (t1) and on average 1.2 yr later (t2). Physical capacity was measured as maximal isometric strength (F(iso)), sprint power output (P30), maximal power output (POmax), and peak oxygen uptake (VO2peak). Physical strain and performance time were measured during standardized ADL (ascending ramp, passing door, making transfer, washing hands).

RESULTS

P30 and POmax showed a significant increase at t2, whereas F(iso) and VO2peak remained unchanged. Sport activity was the most important independent variable explaining relative changes in P30 and POmax, showing on average larger values in active subjects. Other independent variables that were significantly related to changes in physical capacity were the occurrence of illness and having a tetraplegia (negatively associated with changes in P30 and VO2peak), and incompleteness of the lesion and an increased body mass (positively associated with changes in F(iso)). Increase in physical capacity was found to coincide with decrease of the physical strain and performance time of ADL, reflected in significant negative correlation coefficients for some tasks.

CONCLUSIONS

It is concluded that physical capacity and performance of ADL improved or remained constant during the first year after rehabilitation and that sport participation is associated with improvements in physical capacity. Results of this study underline the importance of being physically active during the period after rehabilitation of persons with spinal cord injuries.

Changes in lipid, lipoprotein and apolipoprotein profiles in persons with spinal cord injuries during the first 2 years post-injury

OBJECTIVE

To investigate changes in lipid, lipoprotein and apolipoprotein profiles in persons with spinal cord injury (SCI) during the first 2 years post-injury, and to determine whether changes in risk profiles were associated with sport activity and/or changes in physical capacity parameters.

DESIGN

Risk profiles and physical capacity were investigated in 19 subjects with recent SCI during rehabilitation (t1) and +/- 1 year after discharge from rehabilitation (t2).

MAIN OUTCOME MEASURES

Changes in total plasma cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), apolipoprotein-A1 (ApoA1), apolipoprotein-B (ApoB) concentrations, the ratios TC/HDL-C, LDL-C/HDL-C, ApoA1/ApoB and HDL-C/ApoA1, and physical capacity (maximal isometric strength, sprint power output, maximal power output, aerobic power).

RESULTS

Risk profile parameters changed towards more favorable values at t2, except for HDL-C (P=0.06), TG and HDL-C/ApoA1. Sport activity and changes of the physical capacity were the most important determinants of changes in lipid and (apo)lipoprotein profiles, showing more favorable values with larger increases of the physical capacity and in persons who were physically active.

CONCLUSION

Results show that the lipid and (apo)lipoprotein profiles improve in persons with SCI during the first 2 years post-injury, and that improving the physical capacity or being physically active can improve the lipid and (apo)lipoprotein profiles.

Physical work capacity after 7 wk of wheelchair training: effect of intensity in able-bodied subjects

PURPOSE

The purpose of this study was to study the effects of a 7-wk wheelchair training program on physical work capacity in able-bodied subjects. Effects of training intensities of 50 and 70% heart rate (HR) reserve (HRR) were studied for different subject groups.

METHODS

Twenty-seven able-bodied male subjects participated in this study. They were randomly divided into a control group (N = 8), a 50%-intensity group (N = 9), and a 70%-intensity group (N = 10). The 50%- and the 70%-intensity groups received a 7-wk wheelchair training program: three times a week, one-half hour wheelchair exercise on a motor driven treadmill at an average intensity of 50 and 70% of the HRR, respectively. Before and after the training period, parameters for physical work capacity (maximal isometric strength (Fiso), sprint power (P30), maximal power output (POmax) and peak oxygen uptake (VO2peak)), and submaximal performance (mechanical efficiency, HR) at 20 and 40% of the estimated POmax (ME20, ME40; HR20, HR40) were obtained during tests on a stationary wheelchair ergometer.

RESULTS

A two-factor ANOVA for repeated measures on the within-subjects factor "pre-post tests," the between-subject factor training (50% and 70% training vs control) and the interaction term showed that the 50%-intensity group significantly increased on P30 and POmax compared with the control group. The 70% intensity group significantly increased on P30, POmax and VO2peak compared with the control group (P < 0.05). The 70% group did not show significantly higher increases in P30 and POmax over training than the 50% intensity. No significant effects were found for the Fiso and the parameters at submaximal PO.

CONCLUSIONS

The wheelchair training at both intensities can have favorable effects on maximal physical work capacity in able-bodied subjects, and possibly also on mechanical efficiency at submaximal power output. Effects are seen in parameters for both aerobic and anaerobic work capacities. Although training at 70% intensity was more effective than the 50% intensity, training at 50% HRR may initially be more appropriate in untrained individuals, such as novice wheelchair users at the start of their rehabilitation, to prevent fatigue and enhance motivation.

Effectiveness of force application in manual wheelchair propulsion in persons with spinal cord injuries

The objective of this study was to investigate effectiveness of force application, the ratio power output/energy expenditure, and timing parameters of wheelchair propulsion in persons with tetraplegia (TP, n=17) and paraplegia (PP, n=12), at two different intensity conditions. All subjects performed a maximal exercise test on a wheelchair ergometer. Exercise bouts with an intensity of 30 to 50% and 60 to 80% of the maximal power output were analyzed. Effectiveness of force application, defined as the ratio of the effective force and the total force, was considerably lower in TP, compared with PP. Effectiveness of force application in the plane of the wheel was comparable between TP and PP. TP showed a significantly lower effectiveness of force application in the frontal plane and applied the forces in a more lateromedial direction to the hand rim. The ratio power output/energy expenditure, calculated as an indication of gross mechanical efficiency, was considerably lower in TP and was associated with the effectiveness of force application (r=0.64; P < 0.01). Timing parameters showed that TP positioned their hands in a more backward position on the hand rim. Comparing the different intensity conditions revealed that force was applied more effectively, and the ratio power output/energy expenditure was higher at the higher intensity condition. Push time, relative to cycle time, increased, and beginning angle showed a forward shift with a higher load. TP tended to decrease, whereas PP showed a tendency for an increase in stroke angle with a higher load. The low effectiveness and different pattern of force application in TP should be taken into account when developing other wheelchair propelling mechanisms and training programs for this population.

Lipid, lipoprotein, and apolipoprotein profiles in active and sedentary men with tetraplegia

OBJECTIVE

To investigate whether the risk profile of coronary heart disease (CHD) is more favorable in physically active men with tetraplegia compared with sedentary men with tetraplegia.

DESIGN

Using a cross-sectional design, the lipid and (apo)lipoprotein concentrations of 11 active and 13 sedentary men with tetraplegia were compared. Regression analysis was applied to investigate the influence of subject characteristics and behavioral factors on the risk profile of CHD.

MAIN OUTCOME MEASURES

Total plasma cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), triglycerides, apolipoprotein-A1 (ApoA1), and apolipoprotein-B (ApoB) concentrations were determined. Low-density lipoprotein cholesterol (LDL-C) and the ratios TC/HDL-C, LDL-C/HDL-C, ApoA1/ApoB, and HDL-C/ApoA1 were calculated.

RESULTS

A significantly higher HDL-C and ApoA1/ApoB and lower TC/HDL-C were found in the active group. Age and body mass index were important determinants of the lipids and (apo)lipoproteins. Sport activity was the only significant determinant of HDL-C.

CONCLUSIONS

Results suggest a positive influence of sport activity on HDL-C in men with tetraplegia, which may reduce the risk of CHD.

Effect of training on physical capacity and physical strain in persons with tetraplegia

The effects of quad rugby training on physical capacity and physical strain during standardized activities of daily living were investigated in 9 trained (A) and 5 untrained quad rugby players (B), and 7 inactive persons with tetraplegia (C) at 0, 3 and 6 months after the start of a quad rugby training program (1.5h.wk[-1]). Physical capacity was measured as maximal isometric strength, peak power output (POpeak) and peak oxygen uptake (VO2peak) on a stationary wheelchair ergometer. Physical strain was expressed as a percentage of heart-rate reserve. No measurable training effects could be observed for POpeak, VO2peak and physical strain. A significant rise in maximal isometric strength was found in group B after 3 and 6 months of training, whereas no significant changes were found in groups A and C. The results suggest that a higher training frequency and/or intensity may be needed to gain significant training effects for POpeak and VO2peak.

Respiratory muscle strength and endurance in individuals with tetraplegia

The purpose of this study was to assess the strength and endurance capacity of the respiratory muscles in individuals with tetraplegia and to compare these properties to those in able-bodied subjects. In addition, the relationship between respiratory muscle properties and respiratory function, ie, ventilation and gas exchange, was examined. Fifteen individuals with tetraplegia (TP) and 15 able-bodied controls (AB) participated in this study. Respiratory muscle strength was assessed by measuring static inspiratory (Pi-max) and expiratory (Pe-max) mouth pressure, whereas inspiratory endurance capacity (Pendu) was determined using an incremental ventilatory threshold loading test. Results were significantly lower in TP compared to AB: Pi-max (5.9 vs 8.4 kPa), Pre-max (5.6 vs 12.3 kPa), Pendu (2.7 vs 6.9 kPa), vital capacity (3.1 vs 5.5 l) and rest oxygen uptake (0.21 vs 0.29 ml/min) and significant correlations were found between the respiratory muscle properties and the respiratory function. Of note is the fact that the ratio Pendu/Pi-max was significantly lower in TP (0.49) compared to AB (0.82). This implies that the capacity to generate pressure during the endurance test was not fully used in TP, probably due to an early onset of muscle fatigue and an altered force-length relationship of the diaphragm muscle. Results of this study demonstrate a limited ability in individuals with tetraplegia to ventilate.

Physical capacity and physical strain in persons with tetraplegia; the role of sport activity

To determine the relationship between sport activity and physical capacity (PC) and physical strain (PS) during standardized activities of daily living (ADL), 25 subjects with tetraplegia were studied. To quantify PC, maximal power output, peak oxygen uptake and maximal isometric force were determined on a stationary wheelchair ergometer. PS was described as the highest heart rate (expressed as a percentage of the heart rate reserve), observed during standardized ADL tasks. Multiple regression analyses showed that sport activity, lesion level and completeness of the lesion were the most important determinants of PC. An inverse relationship was found between PS during the ADL tasks and parameters of PC. Parameters of PC and sport activity were significant determinants of PS. It is concluded that a higher PC is associated with a lower PS in daily life, and that sport activity is an important determinant of PC. Although no causal relationships could be established, due to the cross-sectional character of this study, the results support the assumption that being physically active is highly important for individuals with tetraplegia.

The effect of training on cardiovascular responses to arm exercise in individuals with tetraplegia

The aim of this study was to investigate the physiological responses to maximal and submaximal arm-cranking exercise in 21 individuals with tetraplegia (TP) and to evaluate the effect of a 3 and 6-month training period (mean frequency of 1.5 h.week-1, mean intensity at 35% of the training time above 60% of the heart rate reserve) on these physiological responses. The TP were divided into 8 trained subjects (T), 7 untrained subjects (U) who started their training at the beginning of the study, and 6 sedentary subjects (S). All the subjects were tested at the beginning of training and after 6 months, whereas T and U were also tested in between, at 3 months. During maximal exercise, peak power output and peak oxygen uptake per kilogram bodymass were significantly higher in T (49.9 W and 14.2 ml.min-1.kg-1 respectively) compared to U (20.7 W and 8.8 ml.min-1.kg-1 respectively) and S (15.9 W and 7.4 ml.min-1.kg-1 respectively), whereas all other peak responses showed tendencies to be higher in T. This is most likely to have been the result of participation in sport and the effect of it on performance capacity in T, although differences in completeness of the lesion may have influenced the results. No significant differences were found for submaximal and maximal responses after 3 or 6 months of training in either T and U or in S. This may have been due on the one hand to the vulnerability of the subjects to diseases and injuries and on the other hand to the low frequency of training. On an individual basis, however, remarkable improvement was observed during the training period, especially for individuals in the U group. These results would suggest that a 3 or 6-month training period has no measurable positive effect on the fitness level of TP.