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.

The difficulty of the postural control task affects multi-muscle control during quiet standing.

The aim of this study was to compare the electromyographic (EMG) coherence between the lower limb and the core muscles when carrying out two postural tasks at different difficulty levels. EMG was recorded in 20 healthy male subjects while performing two independent quiet standing tasks. The first one involved a bipedal stance with the eyes open, while the second consisted of a dominant unipedal stance also with the eyes open. The obtained EMG signals were analysed by computing estimations of EMG-EMG coherence between muscle pairs, both singly (single-pair estimations) and combined (pooled estimations). Pooled and single coherence of anterior, posterior, core, antagonist and mixed pairs of muscles were significant in the 0-5 Hz frequency band. The results indicate that core and antagonist muscle groups, such as the anterior and posterior muscles, share low-frequency neural inputs (0-5 Hz) which could be responsible of the M-modes assembly. The core muscles could therefore provide the necessary synergy to maintain spine stability during the balancing exercise. Finally, differences in EMG-EMG coherence suggest that the muscle synergies formed during unipedal stance tasks are different from those established during bipedal stance.

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.

The use of heart rate variability in assessing precompetitive stress in high-standard judo athletes.

The objective of this study is to examine the sensitivity to and changes in heart rate variability (HRV) in stressful situations before judo competitions and to observe the differences among judo athletes according to their competitive standards in both official and unofficial competitions. 24 (10 male and 14 female) national- and international-standard athletes were evaluated. Each participant answered the Revised Competitive State Anxiety Inventory (CSAI-2R) and their HRV was recorded both during an official and unofficial competition. The MANOVA showed significant main effects of the athlete's standard and the type of competition in CSAI-2R, in HRV time domain, in HRV frequency domain and in HRV nonlinear analysis (p<0.05). International-standard judo athletes have lower somatic anxiety, cognitive anxiety, heart rate and low-high frequency ratio than national-standard athletes (p<0.05). International-standard athletes have a higher confidence, mean RR interval, standard deviation of RR, square root of the mean squared difference of successive RR intervals, number of consecutive RR that differ by more than 5 ms, short-term variability, long-term variability, long-range scaling exponents and short-range scaling exponent than national-standard judo athletes. In conclusion, international-standard athletes show less pre-competitive anxiety than the national-standard athletes and HRV analysis is sensitive to changes in pre-competitive anxiety.

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.

Transdermal nitroglycerine treatment of shoulder tendinopathies in patients with spinal cord injuries.

STUDY DESIGN: A clinical blind study was conducted to determine the efficacy of transdermal nitroglycerine treatment on the awareness of shoulder pain. OBJECTIVE: This study aims to determine the effects of transdermal nitroglycerine on shoulder pain and on functional shoulder movement in patients with spinal cord injuries and shoulder tendinopathies. A second aim is to establish the side effects of the treatment. SETTING: Hospital "La Fe" in Valencia, Spain. METHODS: A total of 45 spinal cord injury patients, all of whom are wheelchair users with shoulder tendinopathy, were randomly divided into two groups: placebo (n=12) and experimental (n=33). The experimental group (EG) received transdermal treatment for 6 months in the form of a 1.25 mg nitroglycerine (NT) patch on the greater tubercle. A placebo patch was used with the placebo subjects. Functional shoulder movements were assessed by articular range of motion and pain, using a visual analogical scale. RESULTS: NT treatment reduced the awareness of shoulder pain and increased the functional movement and range of articular motion in the shoulders of the EG members (P<0.05). CONCLUSIONS: We conclude that transdermal NT is an efficient method for treating shoulder tendinopathies in wheelchair users with spinal cord injuries.

A comparison of elastic tubing and isotonic resistance exercises.

The aim of this study was to assess effects of a short-term resistance program on strength in fit young women using weight machines/free weights or elastic tubing. 42 physically fit women (21.79±0.7 years) were randomly assigned to the following groups: (i) the Thera-Band (®) Exercise Station Group (TBG); (ii) the weight machines/free weights group (MFWG); or (iii) the control group (CG). Each experimental group performed the same periodised training program that lasted for 8 weeks, with 2-4 sessions per week and 3-4 sets of 8-15 submaximal reps. A load cell (Isocontrol; ATEmicro, Madrid, Spain) was used to test the evolution of the Maximum Isometric Voluntary Contraction (MIVC) in 3 different exercises: Vertical Rowing (VR), Squat (S) and Back Extension (BE). A mixed model MANOVA [group (CG, TBG, MFWG) x testing time (pre-test, post-test)] was applied to determine the effect of the different resistance training devices on strength. The only groups to improve their MIVC (p<0.005) were TBG and MFWG, respectively: VR 19.87% and 19.76%; S 14.07 and 28.88; BE 14.41% and 14.00%. These results indicate that resistance training using elastic tubing or weight machines/free weights have equivalent improvements in isometric force in short-term programs applied in fit young women.

Two-leg squat jumps in water: an effective alternative to dry land jumps.

The current study was designed to quantify and compare the kinetic parameters of two-leg squat jumps carried out on dry land, in water and in water using area devices that increase drag force. Twelve junior female handball players who had been competing at national level for the previous two years volunteered to participate in the study. Intensity of the two-leg squat jump was examined using a force plate (9 253-B11, Kistler Instrument AG, Winterthur, Switzerland) in three different conditions: on dry land, in water and in water using devices. An ANOVA with repeated measurements (condition) was applied to establish differences between the three jumps. The results show that peak impact force and impact force rate for the water jumps was lower than for the dry land jumps (p<0.05), while peak concentric force was higher for the water jumps than the dry land jumps (p<0.05). In addition, no statistically significant differences were found between water jumps for these variables (p>0.05). These results indicate that water provides an ideal environment for carrying out jumps, as the variables associated with the exercise intensity are boosted, while those related to the impact force are reduced and this fact could be less harmful.

Time and frequency analysis of the static balance in young adults with Down syndrome.

The main objective of this study is to understand the differences in equilibrium control between normal subjects and those with Down syndrome. A total of 54 subjects participated voluntarily, divided into control group and Down syndrome group. The equilibrium of the subjects was tested under two conditions: bipedal support with eyes open and closed. The signals were analyzed in a time and frequency domain. The statistical parameters selected (i.e., RMS distance, mean velocity, mean frequency and sway area) to analyze the behavior of the center of pressures (CoP) are calculated employing the result of the combination of the time series data in both directions (i.e. resultant distance). In order to calculate the frequency bands produced by the displacements of the CoP, a Fast Fourier Transform of the data was performed. The group with Down syndrome showed poorer static equilibrium control than the control group in the time domain. In the frequency domain, we found differences between the groups in the distribution of energy in the frequency bands analyzed. In addition, we observed the existence of an interaction effect of the group and the condition tested (p<0.001). These findings show that in the absence of visual information, the control group increases the energy at low frequencies, while the group with Down syndrome decreases it. Additionally, the lower amount of energy observed in this band under the 'eyes closed' condition may serve to identify abnormalities in the functioning of the vestibular apparatus of individuals with Down syndrome and/or difficulties experienced by these individuals in extracting relevant information from this route.