Comorbidity and physical activity in people with paraplegia: a descriptive cross-sectional study.

STUDY DESIGN: Descriptive cross-sectional study. SETTING: The study was conducted in the Spinal Cord Injury Unit of the University Vall d'Hebron Hospital and in the Physical Education and Sports Department of the University of Valencia. OBJECTIVES: The aim of this study was to quantify the presence of comorbidities in spinal cord injury (SCI) subjects who did or did not perform regular physical activity (PA) and to identify the relationship between PA and the level of comorbidity. METHODS: The sample consisted of patients with complete motor SCI (T2-T12), who were fitted with an accelerometer attached to the non-dominant wrist for a period of 1 week. The clinical and blood analytic variables were selected by an expert panel. RESULTS: In the exploratory analysis, we have found differences in the total number of pathologies between active and inactive patients, with fewer total pathologies in the active patient group. An association was found between the PA level and diabetes mellitus (; P=0.047; φ=0.25). We also observed an association between the cardioprotector level of high-density lipoprotein (HDL)-cholesterol and PA level (; P=0.057; Φ0.24). CONCLUSIONS: Our results suggest that patients considered active showed lower total comorbidity than inactive patients and higher protection levels against developing cardiovascular comorbidity.

Active paraplegics are protected against exercise-induced oxidative damage through the induction of antioxidant enzymes.

STUDY DESIGN: Experimental study. OBJECTIVES: Exercise improves functional capacity in spinal cord injury (SCI). However, exhaustive exercise, especially when sporadic, is linked to the production of reactive oxygen species that may have a detrimental effect on SCI. We aimed to study the effect of a single bout of exhaustive exercise on systemic oxidative stress parameters and on the expression of antioxidant enzymes in individuals with paraplegia. SETTING: The study was conducted in the Physical Therapy department and the Physical Education and Sports department of the University of Valencia. METHODS: Sixteen paraplegic subjects were submitted to a graded exercise test (GET) until volitional exhaustion. They were divided into active or non-active groups. Blood samples were drawn immediately, 1 and 2 h after the GET. We determined plasma malondialdehyde (MDA) and protein carbonylation as markers of oxidative damage. Antioxidant gene expression (catalase and glutathione peroxidase-GPx) was determined in peripheral blood mononuclear cells. RESULTS: We found a significant increase in plasma MDA and protein carbonyls immediately after the GET (P<0.05). This increment correlated significantly with the lactate levels. Active paraplegics showed lower levels of exercise-induced oxidative damage (P<0.05) and higher exercise-induced catalase (P<0.01) and GPx (P<0.05) gene expression after the GET. CONCLUSIONS: These results suggest that exercise training may be useful in SCI patients to develop systemic antioxidant defenses that may protect them against exercise-induced oxidative damage.

The influence of regular physical activity on lung function in paraplegic people.

STUDY DESIGN: Cross-sectional study. OBJECTIVES: The main goal of this study was to examine the influence of regular physical activity (PA) on lung volumes and flows. SETTING: The study was conducted in the Vall d'Hebrón Hospital, Barcelona (Spain), and La Fe Hospital, Valencia (Spain). METHODS: Spirometric tests were performed to 67 paraplegics, and differences were established between the active group (AG) (n=37) that performed >60 min per week of moderate-to-vigorous PA (MVPA) and 30 non-AG (NAG). Further, we established the relationship between the spirometric and PA variables and between being active and reaching the lower limit of normal (LLN) of the spirometric variables. RESULTS: AG had greater values than the NAG: FVC (P<0.01), FEV1 (P<0.01) and PEF (P<0.01). Moderate correlations between the MVPA and FVC (r=0.41, P<0.01) and the MVPA and FEV1 (r=0.39, P<0.01) were obtained. The relationship between being physically active and reaching the LLN was statistically significant for FEV1 (χ2=6.184, P<0.05) but not for FVC (P>0.05). CONCLUSIONS: The performance of MVPA for a minimum of 60 min per week can have a beneficial effect, both on lung volumes and on expiratory flow, and led to an achievement of the LLN in FEV1.

Identifying physical activity type in manual wheelchair users with spinal cord injury by means of accelerometers.

STUDY DESIGN: This was a cross-sectional study. OBJECTIVES: The main objective of this study was to develop and test classification algorithms based on machine learning using accelerometers to identify the activity type performed by manual wheelchair users with spinal cord injury (SCI). SETTING: The study was conducted in the Physical Therapy department and the Physical Education and Sports department of the University of Valencia. METHODS: A total of 20 volunteers were asked to perform 10 physical activities, lying down, body transfers, moving items, mopping, working on a computer, watching TV, arm-ergometer exercises, passive propulsion, slow propulsion and fast propulsion, while fitted with four accelerometers placed on both wrists, chest and waist. The activities were grouped into five categories: sedentary, locomotion, housework, body transfers and moderate physical activity. Different machine learning algorithms were used to develop individual and group activity classifiers from the acceleration data for different combinations of number and position of the accelerometers. RESULTS: We found that although the accuracy of the classifiers for individual activities was moderate (55-72%), with higher values for a greater number of accelerometers, grouped activities were correctly classified in a high percentage of cases (83.2-93.6%). CONCLUSIONS: With only two accelerometers and the quadratic discriminant analysis algorithm we achieved a reasonably accurate group activity recognition system (>90%). Such a system with the minimum of intervention would be a valuable tool for studying physical activity in individuals with SCI.

Heart rate variability in individuals with thoracic spinal cord injury.

STUDY DESIGN: Cross-sectional study. OBJECTIVES: The main goal of our study was to explore the differences in heart rate variability (HRV) while sitting between able-bodied (AB) participants and paraplegic (P) individuals. SETTING: The study was conducted in the Physical Therapy department and the Physical Education and Sports department of the University of Valencia and Vall d'Hebrón Hospital. METHODS: To record the HRV, a 1000-Hz Suunto Oy t6 heart rate monitor was used. The data were analyzed in the temporal and frequency domains, and nonlinear analysis was performed as well. RESULTS: We found significant differences between P and AB participants in SDNN: t(76)=2.81, P<0.01; root mean squared of the difference of successive RR intervals: t(76)=2.35, P<0.05; very low frequency: t(76)=2.97, P<0.01; low frequency: t(41.06)=2.33, P<0.05; total power of the spectrum: t(45.74)=2.57, P<0.05; SD1: t(76)=2.35, P<0.05; SD2: t(76)=2.82, P<0.01. Furthermore, there is a reduced variability in the P participants who adopted a sedentary lifestyle as could be observed in detrended fluctuation1 t(40)=-2.10; P<0.05. CONCLUSION: Although individuals in the P group were more active in sports than the AB group, they had an altered HRV when compared with AB individuals. It could be important to develop more intense sports programs to improve cardiac vagal tone, which in turn produces a decrease in work and oxygen consumption of the heart.

Neural network for estimating energy expenditure in paraplegics from heart rate.

The aim of the present study is to obtain models for estimating energy expenditure based on the heart rates of people with spinal cord injury without requiring individual calibration. A cohort of 20 persons with spinal cord injury performed a routine of 10 activities while their breath-by-breath oxygen consumption and heart rates were monitored. The minute-by-minute oxygen consumption collected from minute 4 to minute 7 was used as the dependent variable. A total of 7 features extracted from the heart rate signals were used as independent variables. 2 mathematical models were used to estimate the oxygen consumption using the heart rate: a multiple linear model and artificial neural networks. We determined that the artificial neural network model provided a better estimation (r=0.88, MSE=4.4 ml · kg(-1) · min(-1)) than the multiple linear model (r=0.78; MSE=7.63 ml · kg(-1) · min(-1)).The goodness of fit with the artificial neural network was similar to previous reported linear models involving individual calibration. In conclusion, we have validated the use of the heart rate to estimate oxygen consumption in paraplegic persons without individual calibration and, under this constraint, we have shown that the artificial neural network is the mathematical tool that provides the better estimation.

Sitting balance and limits of stability in persons with paraplegia.

STUDY DESIGN: Cross-sectional, observational study of paraplegic and able-bodied persons. OBJECTIVES: The aim of the study was to analyse the temporal and frequency domains of seated balance to better understand nervous system control in equilibrium in persons with spinal cord injury (SCI) and to explore their centre of pressure (CoP) limits before experiencing a fall. SETTING: University of Valencia, Spain. METHODS: Static and dynamic seated balance were assessed in 24 paraplegic persons divided into two groups: low paraplegia group (LP) and high paraplegia group (HP), and 24 healthy volunteers with an extensiometric force plate. Two types of tests were performed: a static test (ST), where data signal was analysed by temporal and frequency domains, and a stability limit test (SLT), where different stability limits were calculated. RESULTS: The paraplegic group revealed lower static postural control in both domains in most of the parameters analysed compared with the control group (CG). Similar results were obtained with regard to the SLT, showing differences in the three parameters analysed between the CG and SCI groups. CONCLUSION: Posturographic assessment in ST was useful to explore nervous system control in equilibrium in this population, presenting a decreased balance in paraplegic groups and an altered pattern in the sensorial and cerebellum bands compared with able-bodied individuals. Furthermore, SLT indicated less movement control of the CoP in paraplegic groups, which may influence the performance of their daily activities.

Validation of the use of Actigraph GT3X accelerometers to estimate energy expenditure in full time manual wheelchair users with spinal cord injury.

STUDY DESIGN: Cross-sectional validation study. OBJECTIVES: The goals of this study were to validate the use of accelerometers by means of multiple linear models (MLMs) to estimate the O2 consumption (VO2) in paraplegic persons and to determine the best placement for accelerometers on the human body. SETTING: Non-hospitalized paraplegics' community. METHODS: Twenty participants (age=40.03 years, weight=75.8 kg and height=1.76 m) completed sedentary, propulsion and housework activities for 10 min each. A portable gas analyzer was used to record VO2. Additionally, four accelerometers (placed on the non-dominant chest, non-dominant waist and both wrists) were used to collect second-by-second acceleration signals. Minute-by-minute VO2 (ml kg(-1) min(-1)) collected from minutes 4 to 7 was used as the dependent variable. Thirty-six features extracted from the acceleration signals were used as independent variables. These variables were, for each axis including the resultant vector, the percentiles 10th, 25th, 50th, 75th and 90th; the autocorrelation with lag of 1 s and three variables extracted from wavelet analysis. The independent variables that were determined to be statistically significant using the forward stepwise method were subsequently analyzed using MLMs. RESULTS: The model obtained for the non-dominant wrist was the most accurate (VO2=4.0558-0.0318Y25+0.0107Y90+0.0051YND2-0.0061ZND2+0.0357VR50) with an r-value of 0.86 and a root mean square error of 2.23 ml kg(-1) min(-1). CONCLUSIONS: The use of MLMs is appropriate to estimate VO2 by accelerometer data in paraplegic persons. The model obtained to the non-dominant wrist accelerometer (best placement) data improves the previous models for this population.

Effects of resistance training on strength, pain and shoulder functionality in paraplegics.

STUDY DESIGN: Time series design. OBJECTIVES: To determine the effects of a shoulder resistance training programme on isokinetic and isometric strength, body composition, pain and functionality in paraplegic subjects. SETTING: University of Valencia, Valencia, Spain. METHODS: A total of 15 subjects with thoracic spinal cord injury (SCI) performed three testing sessions with an 8-week period between the sessions. Subjects were not disturbed between the first and the second testing sessions. Subjects performed an 8-week resistance training programme after the second testing session. Variations in isometric and isokinetic shoulder muscle strength, body composition, reported pain and shoulder functionality were evaluated. RESULTS: The training programme produced a significant increase (P<0.05) in the isometric and isokinetic strength of several shoulder movements as well as an increase (P<0.05) in arm fat-free mass and a decrease in arm fat mass (FM). Furthermore, reported pain was decreased, (P<0.05) and upper-limb functionality was increased (P<0.05). CONCLUSION: Implementing resistance training programmes as physical therapy in SCI subjects effectively increases strength, muscle mass and upper-limb functionality, whereas decreasing FM and pain perception.

Force normalization in paraplegics.

The principal aim of our study was the determination of the effectiveness of a standardized ratio, allometric scaling model and a gamma function model in normalizing the isometric torque data of spinal cord patients and healthy subjects. For this purpose we studied a sample of 21 healthy males and 23 spinal cord injury males. The experiment consisted of the measurement of the force of the upper limb movement executed by all the subjects. We also determined anthropometric variables with dual-energy x-ray absorptiometry. The experimental data were analyzed with 3 force normalization methods. Our results indicate that the most important confounding variable was the fat free mass of the dominant upper limb (r>0.36, p<0.05). With the standardization by body mass and allometric scaling model, the normalized torque was influenced by body size variables. However, the normalized torque by the gamma function model was independent of body size measures. Paraplegics were weaker (p<0.05) in extension movements when the data were normalized by the gamma function model. In summary, this study shows that the gamma function model with fat free mass of the dominant upper limb was more effective than the standardized ratio in removing the influence of body size variables.