Exercise intervention on cardiorespiratory fitness in rheumatoid arthritis patients with high cardiovascular disease risk: a single-arm pilot study.

OBJECTIVE: In patients with rheumatoid arthritis (RA) with cardiovascular disease risk, it is unknown whether exercises are safe, improve cardiorespiratory fitness and reduce disease-related symptoms and cardiovascular-disease (CVD) risk factors. We aimed to investigate in RA patients with CVD risk: (1) safety of medium to high-intensity aerobic exercises, (2) potential changes of cardiorespiratory fitness and (3) disease activity and CVD risk factors in response to the exercises. METHODS: Single-arm pilot-exercise intervention study including 26 consecutive patients (21 women) with > 4% 10-year risk of CVD mortality according to the Dutch Systematic Coronary Risk Evaluation. Aerobic exercises consisted of two supervised-sessions and five home-sessions per week for 12 weeks. Patients were required to exercise at intensities between 65 and 85% of their maximum heart rate. To assess safety, we recorded exercise related adverse events. Before and after the exercises, cardiorespiratory fitness was assessed with a graded maximal oxygen-uptake exercise test, while disease activity was evaluated via the Disease Activity Score-28 (DAS28) using the erythrocyte segmentation rate (ESR). Resting blood pressure, ESR and total cholesterol were assessed as CVD risk factors. RESULTS: Twenty out of 26 patients performed the 12-week exercises without any adverse events. According to patients, withdrawals were unrelated to the exercises. Exercises increased cardiorespiratory fitness (pre: 15.91 vs. post: 18.15 ml.kg-1 min-1, p = 0.003) and decreased DAS28 (pre: 2.86 vs. post: 2.47, p = 0.04). No changes were detected in CVD risk factors. CONCLUSION: A 12-week exercise intervention seems to be safe and improves cardiorespiratory fitness and disease activity in patients with RA with a high risk for cardiovascular diseases. Key Points 1. Rheumatoid arthritis patients with high cardiovascular disease risk were able to perform a maximum exercise test and a 12-week aerobic-based medium-to-high intensity exercise intervention. 2. The exercise intervention improved cardiorespiratory fitness and disease activity in rheumatoid arthritis patients with high cardiovascular disease risk. 3. Cardiorespiratory fitness levels were still low post-exercise intervention (i.e. 18.15 ml.kg-1min-1 compared to the 20.9 ml.kg-1min-1 baseline mean of the RA patients without CVD risk).

Construct validity and reliability of the modified gait efficacy scale for older adults.

PURPOSE: To perform a cross-cultural adaptation of the mGES into Dutch and investigate its construct validity, internal consistency, test-retest reliability and floor and ceiling effects in a large cohort of community-dwelling older adults. MATERIALS AND METHODS: We translated the British version of the mGES into Dutch, back into English, and had a native English speaker review the final version. Next, we included 223 community-dwelling older adults from the 'Veilig in Beweging Blijven' (VIBE) cohort (69.8 [67.6-74.3] years old, 155 (69.5%) female), who filled out both the mGES and the Falls Efficacy Scale-International (FES-I) twice, with a month in between. Construct validity was assessed by Spearman's correlation between the scores on the mGES and the FES-I. Internal consistency was assessed with Cronbach's alpha and test-retest reliability was assessed with the intra class correlation coefficient (ICC(2,1)). RESULTS: Construct validity (rho = -0.81, p < 0.001), internal consistency (α = 0.95), and test-retest reliability (ICC(2,1)=0.90, 95%CI = [0.87-0.92]) were all excellent. Ceiling effect was observed in 44 (19.7%) participants which suggest caution when evaluating the mGES for fit and confident older adults. CONCLUSION: The Dutch mGES is a valid and reliable tool to assess confidence in walking and is suggested as a tool for evaluating self-efficacy after interventions aimed at improving gait.IMPLICATIONS FOR REHABILITATIONAssessment and rehabilitation of gait may be affected by self-efficacy of walking performance.We show that the Dutch translation of the modified gait efficacy scale is a valid and reliable tool for assessing self-efficacy of walking.A ceiling effect was observed that was associated with muscle strength and symptoms of depression.The results of the present study underline the use of the modified gait efficacy scale in the assessment and evaluation of self-efficacy of walking in rehabilitation.

Cardiorespiratory fitness and physical activity in people who have rheumatoid arthritis at an increased risk of cardiovascular disease: a cross-sectional study.

Lower cardiorespiratory fitness (CRF) and physical activity (PA) associate with higher cardiovascular disease (CVD) risk, but the relationship between CRF and PA in people who have rheumatoid arthritis (RA) at an increased CVD risk (CVD-RA) is not known. The objectives of this study were to determine the levels of CRF and PA in people who have CVD-RA and to investigate the association of CRF with PA in people who have CVD-RA. A total of 24 consecutive patients (19 women) with CVD-RA (> 4% for 10-year risk of fatal CVD development as calculated using the Systematic Coronary Risk Evaluation)-were included in the study. CRF was assessed with a graded maximal exercise test determining maximal oxygen uptake (VO2max). PA was assessed with an accelerometer to determine the amount of step count, sedentary, light and moderate-to-vigorous physical activity (MVPA) minutes per day. Mean age of patients was 65.3 ± 8.3 years. CRF mean values were 16.3 ± 1.2 ml·kg-1 min-1, mean step count per day was 6033 ± 2256, and the mean MVPA time was 16.7 min per day. Significant positive associations were found for CRF with step count (B = 0.001, P = 0.01) and MVPA time (B = 0.15, P = 0.02); a negative association was found for CRF with sedentary time (B = - 0.02, P = 0.03). CRF is low and is associated with step count, sedentary time and MVPA time in people who have RA at an increased CVD risk.

Transfer and retention effects of gait training with anterior-posterior perturbations to postural responses after medio-lateral gait perturbations in older adults.

BACKGROUND: Gait perturbations, occurring in any direction in daily life, may result in a fall. In fall prevention, gait perturbation training is a promising approach. Treadmill perturbations in anterior-posterior direction can easily be applied by accelerations or decelerations of the belt, but it is unknown whether training effects transfer to reactive recovery in medio-lateral direction. We aimed to evaluate the transfer and retention effects of gait training with treadmill perturbations in anterior-posterior direction to medio-lateral reactive recovery. METHODS: 30 community dwelling older adults (>65 years) participated in this study. They were randomly assigned to a treadmill training session either with 16 anterior-posterior perturbations or with treadmill walking. The assessments contained a walking trial with 4 anterior-posterior and 4 medio-lateral perturbations. Deviations in trunk velocity from unperturbed walking were summed over the first three strides after perturbation as a measure of recovery. FINDINGS: An exposure to gait perturbations during the baseline assessment led to significant improvement of recovery responses. For anterior-posterior perturbations, both groups showed better recovery immediately and 1-week post-intervention, and no group x time interaction was found.. For medio-lateral perturbations, both groups showed better recovery immediately and 1-week post-intervention, and again no group × time interaction. INTERPRETATION: Baseline assessment with perturbations in anterior-posterior and medio-lateral directions caused significant improvements that were retained. Short-term training can be effective in dynamic stabilization of one's trunk, but our findings do not exclude that multi-directional perturbations may be needed.

Does misjudgement in a stepping down paradigm predict falls in an older population?

Although measures of actual and perceived physical ability appear to predict falls in older adults, a disparity between these two, also known as misjudgement, may even better explain why some older adults fall, while their peers with similar abilities do not. Therefore, we investigated whether adding a misjudgement term improved prediction of future falls. Besides conventional measures of actual (physical measures) and perceived abilities (questionnaires), we used a stepping down paradigm to quantify behavioural misjudgement. In a sample of 55 older adults (mean age 74.5 (s.d. = 6.6) years, 33 females and 20 fallers over a 10-month follow-up period), we tested the added value of a misjudgement term and of a stepping-down task by comparing experimental Bayesian logistic-regression models to a default null model, which was composed of the conventional measures: Falls Efficacy Scale international and QuickScreen. Our results showed that the default null model fitted the data most accurately; however, the accuracy of all models was low (area under the receiver operating characteristic curve (ROC) ≤ 0.65). This indicates that neither a misjudgement term based on conventional measures, nor on behavioural measures improved the prediction of future falls in older adults (Bayes Factor10 ≤ 0.5).

Consistency and test-retest reliability of stepping tests designed to measure self-perceived and actual physical stepping ability in older adults.

BACKGROUND: Older adults with an incorrect perception of their physical abilities may fall more often, suggesting a need for tests to quantify self-perceived and actual abilities. AIMS: To determine between-test consistency and test-retest reliability of three tests that measure self-perceived and actual stepping ability in older adults. METHODS: Older adults performed three stepping tests, covering high (bar test) and far steps (river and step tests). We studied between-test consistency in the perceived ability and actual ability of 269 participants at each task and in the difference between these two (degree of misjudgment). We also studied test-retest reliability in 21 participants. RESULTS: Perceived ability showed moderate consistency (r = 0.46-0.55, p < 0.001) and moderate-to-strong reliability [ICC(2,1) = 0.42-0.63, p < 0.03] for all tests. Actual ability showed strong consistency (r = 0.77, p < 0.001) and strong-to-excellent reliability [ICC(2,1) = 0.68-0.93, p < 0.001]. Degree of misjudgment was weakly consistent between two stepping far tests (r = 0.32, p < 0.001), but not consistent between stepping far and high tests (r = 0.05 and 0.06, p > 0.3). Test-retest reliability of the degree of misjudgment was poor-to-moderate [ICC(2,1) = 0.38 and 0.50, p < 0.05 on the two stepping far tests and ICC(2,1) = - 0.08, p = 0.63 on the stepping high test]. CONCLUSIONS: Actual and perceived ability can be consistently and reliably measured across tests, whereas the degree of misjudgment is less reliable and consistent within individuals.

The effect of walking speed on quality of gait in older adults.

BACKGROUND: Gait quality characteristics can contribute to the identification of individuals at risk of falls. Since older adults with high fall risk tend to walk slower than older adults with a lower fall risk, walking speed may underlie differences in gait quality characteristics. RESEARCH QUESTION: How does walking speed affect gait quality characteristics in older people? METHODS: We investigated the effect of walking speed on gait characteristics in 11 older adults (aged 69.6 ±â€¯4.1 years). Trunk accelerations (Dynaport MoveMonitor) were recorded during 5 min of treadmill walking at four different speeds. From these trunk accelerations we calculated step frequency, root mean square, harmonic ratio, index of harmonicity, sample entropy and logarithmic divergence rate per stride. RESULTS: Our results showed that all gait characteristics were affected by walking speed, except for sample entropy in antero-posterior (AP) direction. An increase in walking speed resulted in a higher step frequency, higher standard deviation, more symmetric gait, more smooth vertical (VT) accelerations, less smooth accelerations in medio-lateral (ML) and AP directions, less regular dynamics in ML direction, more regular dynamics in VT direction, and a more stable gait pattern overall. SIGNIFICANCE: These findings suggest that, within a range of 0.5-1.4 m/s, a lower walking speed results in a lower gait quality, which may underlie differences in gait quality between older fallers and non-fallers.

Gait stability in response to platform, belt, and sensory perturbations in young and older adults.

Perturbation-based gait assessment has been used to quantify gait stability in older adults. However, knowledge on which perturbation type is most suitable to identify poor gait stability is lacking. We evaluated the effects of ipsi- and contra-lateral sway, belt acceleration and deceleration, and visual and auditory perturbations on medio-lateral (ML) and anterior-posterior (AP) margins of stability (MoS) in young and older adults. We aimed to evaluate (1) which perturbation type disturbed the gait pattern substantially, (2) how participants recovered, and (3) whether recovery responses could discriminate between young and older adults. Nine young (25.1 ± 3.4 years) and nine older (70.1 ± 7.6 years) adults walked on the CAREN Extended (Motek BV, The Netherlands). The perturbation effect was quantified by deviation in MoS over six post-perturbation steps compared to baseline walking. Contra-lateral sway and deceleration perturbations resulted in the largest ML (1.9-4 times larger than other types) and AP (1.6-5.6 times larger than other types) perturbation effects, respectively. After both perturbation types, participants increased MoS by taking wider, shorter, and faster steps. No differences between young and older adults were found. We suggest to evaluate the potential of using contra-lateral sway and deceleration perturbations for fall risk identification by including both healthy and frail older adults. Graphical abstract Margins of stability during steady state (left) and perturbed (right) gait to quantify reactive gait stability in response to various perturbation types in young and older adults.

Self-perceived gait stability modulates the effect of daily life gait quality on prospective falls in older adults.

BACKGROUND: Quality of gait during daily life activities and perceived gait stability are both independent risk factors for future falls in older adults. RESEARCH QUESTION: We investigated whether perceived gait stability modulates the association between gait quality and falling in older adults. METHODS: In this prospective cohort study, we used one-week daily-life trunk acceleration data of 272 adults over 65 years of age. Sample entropy (SE) of the 3D acceleration signals was calculated to quantify daily life gait quality. To quantify perceived gait stability, the level of concern about falling was assessed using the Falls Efficacy Scale international (FES-I) questionnaire and step length, estimated from the accelerometer data. A fall calendar was used to record fall incidence during a six-month follow up period. Logistic regression analyses were performed to study the association between falling and SE, step length or FES-I score, and their interactions. RESULTS: High (i.e., poor) SE in vertical direction was significantly associated with falling. FES-I scores significantly modulated this association, whereas step length did not. Subgroup analyses based on FES-I scores showed that high SE in the vertical direction was a risk factor for falls only in older adults who had a high (i.e. poor) FES-I score. In conclusion, perceived gait stability modulates the association between gait quality and falls in older adults such that an association between gait quality and falling is only present when perceived gait stability is poor. SIGNIFICANCE: The results of the present study indicate that the effectiveness of interventions for fall prevention, aimed at improving gait quality, may be affected by a modulating effect of perceived gait stability. Results indicate that interventions to reduce falls in older adults might sort most effectiveness in populations with both a poor physiological and psychological status.

Effect of triceps surae and quadriceps muscle fatigue on the mechanics of landing in stepping down in ongoing gait.

The aim of this study was to evaluate the effects of muscle fatigue of triceps surae and quadriceps muscles in stepping down in ongoing gait. We expected that the subjects would compensate for muscle fatigue to prevent potential loss of balance in stepping down. A total of 10 young participants walked over a walkway at a self-selected velocity to step down a height difference of 10-cm halfway. Five trials were performed before and after a muscle fatigue protocol. Participants performed two fatigue protocols: one for ankle muscle fatigue and another for knee muscle fatigue. Kinematics of and ground reaction forces on the leading leg were recorded. Fatigue did not cause a change in the frequency of heel or toe landing. Our results indicate that in stepping down fatigue effects are compensated by redistributing work to unfatigued muscle groups and by gait changes aimed at enhancing balance control, which was however only partially successful.

A benchmark test of accuracy and precision in estimating dynamical systems characteristics from a time series.

Characteristics of dynamical systems are often estimated to describe physiological processes. For instance, Lyapunov exponents have been determined to assess the stability of the cardio-vascular system, respiration, and, more recently, human gait and posture. However, the systematic evaluation of the accuracy and precision of these estimates is problematic because the proper values of the characteristics are typically unknown. We fill this void with a set of standardized time series with well-defined dynamical characteristics that serve as a benchmark. Estimates ought to match these characteristics, at least to good approximation. We outline a procedure to employ this generic benchmark test and illustrate its capacity by examining methods for estimating the maximum Lyapunov exponent. In particular, we discuss algorithms by Wolf and co-workers and by Rosenstein and co-workers and evaluate their performances as a function of signal length and signal-to-noise ratio. In all scenarios, the precision of Rosenstein's algorithm was found to be equal to or greater than Wolf's algorithm. The latter, however, appeared more accurate if reasonably large signal lengths are available and noise levels are sufficiently low. Due to its modularity, the presented benchmark test can be used to evaluate and tune any estimation method to perform optimally for arbitrary experimental data.

Estimating fall risk with inertial sensors using gait stability measures that do not require step detection.

Falls have major consequences both at societal (health-care and economy) and individual (physical and psychological) levels. Questionnaires to assess fall risk are commonly used in the clinic, but their predictive value is limited. Objective methods, suitable for clinical application, are hence needed to obtain a quantitative assessment of individual fall risk. Falls in older adults often occur during walking and trunk position is known to play a critical role in balance control. Therefore, analysis of trunk kinematics during gait could present a viable approach to the development of such methods. In this study, nonlinear measures such as harmonic ratio (HR), index of harmonicity (IH), multiscale entropy (MSE) and recurrence quantification analysis (RQA) of trunk accelerations were calculated. These measures are not dependent on step detection, a potentially critical source of error. The aim of the present study was to investigate the association between the aforementioned measures and fall history in a large sample of subjects (42 fallers and 89 non - fallers) aged 50 or older. Univariate associations with fall history were found for MSE and RQA parameters in the AP direction; the best classification results were obtained for MSE with scale factor τ = 2 and for maximum length of diagonals in RQA (72.5% and 71% correct classifications, respectively). MSE and RQA were found to be positively associated with fall history and could hence represent useful tools in the identification of subjects for fall prevention programs.

The influence of artificially increased trunk stiffness on the balance recovery after a trip.

Falls occur frequently in the growing population of elderly. Since trunk control is critical for maintaining balance, the higher trunk stiffness in elderly people compared to the general population has been associated with their increased fall-risk. Theoretically, trunk stiffness may be beneficial for balance recovery in walking, i.e. after a trip. A stiff joint may provide a torque that restricts the perturbation effects and thereby reduces the probability of a fall. The aim of this study was to test whether trunk stiffness impaired or assisted balance recovery after a trip during walking. An orthopedic corset was used to simulate trunk stiffness in 11 young male adults. Subjects walked over a platform, with or without the corset on, and were occasionally tripped over a hidden obstacle. Kinematics of the tripping reaction were measured. Initial trunk accelerations were significantly attenuated by the corset, which indicates a positive effect of the stiffening corset. However, no subsequent effects on peak trunk inclination and on the peak moment arm of gravity on the trunk were found. The pattern of trunk motion allowed ample time for triggered or voluntary muscle responses to be generated, before a substantial inclination occurred. It appears that such active responses were sufficient in the young subjects tested to obtain a similar net effect with or without the increased trunk stiffness induced by the corset.

Out-of-plane trunk movements and trunk muscle activity after a trip during walking.

Tripping during gait occurs frequently. A successful balance recovery implies that the forward body rotation is sufficiently reduced. In view of this, adequate control of the trunk momentum is important, as the trunk has a high inertia. The aim of this study was to establish out-of-plane trunk movements after a trip and to determine trunk muscle responses. Ten male volunteers repeatedly walked over a platform in which 21 obstacles were hidden. Each subject was tripped over one of these obstacles at mid-swing of the left foot in at least five trials. Kinematics, dynamics, and muscle activity of the main trunk muscles were measured. After a trip, an increase in trunk flexion was observed (peak flexion 37 degrees). In addition, considerable movements outside the sagittal plane (up to 20 degrees) occurred. Already before landing of the blocked foot, the trunk forward bending movement was reduced, while trunk torsion and lateral rotation were still increasing. Fast responses were seen in both abdominal and back muscles, indicating stiffening of the trunk. These muscle responses preceded the mechanical trunk disturbances, which implies that these responses were triggered by other mechanisms (such as afferent signals from the extremities) rather than a simple stretch reflex. A second burst of predominantly trunk muscle extensor activity was seen at landing, suggesting specific anticipation of the trunk muscles to minimize trunk movements due to landing. In conclusion, despite large movements outside the sagittal plane, it appears that trunk muscle responses to trips are aspecific and especially aimed at minimizing trunk forward bending.

Changes in walking pattern caused by the possibility of a tripping reaction.

This study investigated in 15 young adults whether their walking pattern was altered after forewarning for a possible trip. Such changes might affect tripping reactions and consequently the validity of experimental results. Kinematics and dynamics were measured during overground walking. No changes occurred in walking velocity, step frequency, duration of stride cycle, stance, swing and double support time, or step length. A small increase was found in step width and foot clearance due to ankle dorsiflexion, but these changes were not expected to alter the probability of tripping nor the recovery reactions after tripping in an experimental setup.

Stumbling reactions in man: influence of corticospinal input.

The aim of this study was to evaluate the degree of contribution of supraspinal input to the generation of the compensatory leg muscle activation following stance perturbation. Therefore, evoked motor response (EMR) input-output relations of two different motor tasks were compared at 3 distinct periods: (1) the basic period of muscular activity during standing, i.e. when no additional cortical or spinal activity due to the different tasks is to be expected, (2) the pre-movement period with low background activity, when different spinal and cortical inputs to the motoneuronal pool can be assumed and (3) the period of plateau EMG activity of compensatory and voluntary motor task. Transcranial magnetic stimulation (TMS) just below the motor threshold was applied randomly at 19 different time-intervals before and during the onset of stance perturbation and for comparison during an equivalent voluntary foot-dorsiflexion task. Recordings of electromyographic (EMG) activity from the tibialis anterior (TA) and corresponding ankle-joint movements were made from both legs. Forward-directed displacements were induced by randomly-timed ramp impulses of constant acceleration upon a moveable platform. For comparison, leg muscle EMG was recorded during isometric foot dorsiflexion during stance while leaning back against a support. The stance perturbations were followed by a compensatory response (CR) in the TA with a mean onset time of 81 ms. During the basic period of muscular activity and the period of plateau EMG activity there was no significant difference of the input-output relation between stance perturbation and the voluntary motor task. However, in the voluntary task compared with the CR, there was significantly greater input-output relation (facilitation) of the EMR in the TA following TMS, which may be related to an increased cortical influence. In contrast to this result of the CR following stance perturbation, a facilitation of the EMR was described for hand muscles under corresponding conditions of automatic compensation for muscle stretch, suggesting a transcortical reflex loop. This difference in the results from upper and lower extremity muscles favors the assumption of a predominantly spinal generation of the TA-CR following stance perturbation.

Cortical facilitation of cutaneous reflexes in leg muscles during human gait.

During human gait, cortical convergence on sural nerve reflex pathways was investigated by means of transcranial magnetic stimulation (TMS) of the cortex in five phases of the step cycle during human walking on a treadmill. Muscular responses to paired electrical and magnetic stimulation were compared with the linear summation of the individual stimuli. For both the tibialis anterior (TA) and biceps femoris (BF) muscles, the averaged data of four subjects showed a significant facilitation mainly in the swing phase of the step cycle. It is suggested that facilitation of corticospinal input onto cutaneous reflex pathways is enhanced specifically in these periods of the step cycle.

Evaluation of the cuticle bleeding time in canine haemophilia A.

In this paper we describe our clinical experience and results with the cuticle bleeding time test in a colony of cross-bred Labrador retrievers with severe haemophilia A. The dogs have a severe bleeding tendency with a high incidence of fatal haemorrhages in the central nervous system. Homozygous females appeared to be especially prone to this lethal complication. Factor VIII recovery and half-life determinations yielded results similar to the data from human studies. The cuticle bleeding time proved to be a good measure of the coagulation defect. The prolongation of the bleeding time could be completely abolished by administration of 10 to 15 units of canine factor VIII per kg body weight. We conclude that the cuticle bleeding time in canine haemophilia provides us with a suitable model for the in vivo study of new therapeutic materials.