Feedback control of heart rate during robotics-assisted tilt table exercise in patients after stroke: a clinical feasibility study.

BACKGROUND: Patients with neurological disorders including stroke use rehabilitation to improve cognitive abilities, to regain motor function and to reduce the risk of further complications. Robotics-assisted tilt table technology has been developed to provide early mobilisation and to automate therapy involving the lower limbs. The aim of this study was to evaluate the feasibility of employing a feedback control system for heart rate (HR) during robotics-assisted tilt table exercise in patients after a stroke. METHODS: This feasibility study was designed as a case series with 12 patients ( n = 12 ) with no restriction on the time post-stroke or on the degree of post-stroke impairment severity. A robotics-assisted tilt table was augmented with force sensors, a work rate estimation algorithm, and a biofeedback screen that facilitated volitional control of a target work rate. Dynamic models of HR response to changes in target work rate were estimated in system identification tests; nominal models were used to calculate the parameters of feedback controllers designed to give a specified closed-loop bandwidth; and the accuracy of HR control was assessed quantitatively in feedback control tests. RESULTS: Feedback control tests were successfully conducted in all 12 patients. Dynamic models of heart rate response to imposed work rate were estimated with a mean root-mean-square (RMS) model error of 2.16 beats per minute (bpm), while highly accurate feedback control of heart rate was achieved with a mean RMS tracking error (RMSE) of 2.00 bpm. Control accuracy, i.e. RMSE, was found to be strongly correlated with the magnitude of heart rate variability (HRV): patients with a low magnitude of HRV had low RMSE, i.e. more accurate HR control performance, and vice versa. CONCLUSIONS: Feedback control of heart rate during robotics-assisted tilt table exercise was found to be feasible. Future work should investigate robustness aspects of the feedback control system. Modifications to the exercise modality, or alternative modalities, should be explored that allow higher levels of work rate and heart rate intensity to be achieved.

The Antigravity Treadmill as a Postoperative and Injury Rehabilitation Tool: Reduction in Contact Forces and Muscle Activity With Reduced Weight Running.

OBJECTIVE: To investigate the effects of reduced weight running on the antigravity (AG) treadmill on maintenance of normal muscle activation and reduction of plantar forces in healthy subjects. DESIGN: Descriptive laboratory study. SETTING: Clinical sports medicine center. PARTICIPANTS: Twenty healthy subjects (10 male and 10 female) aged 18 to 29 years. INDEPENDENT VARIABLES: Subjects running at 6.5 miles per hour on a standard treadmill and on the AG treadmill at 100%, 90%, 80%, 70%, 60%, and 50% of bodyweight levels. MAIN OUTCOME MEASURES: Dynamic plantar loading data were recorded using pressure insoles. Surface electromyography electrodes with imbedded accelerometers were used to estimate timing and magnitude of muscle activity, stride length, and cadence. RESULTS: There was a significant, sequential reduction in peak pressure, maximum force, and force time integral (FTI) with decreasing bodyweight. A 50% bodyweight reduction resulted in a 51% reduction in maximum force and a 59% reduction in FTI in the heel, as compared with 19% to 28% at the metatarsal heads. There was reduced contact area in the heel and midfoot at and below 70% BW. Lower limb muscle activity decreases with reduced bodyweight while maintain normal muscle recruitment timing. CONCLUSIONS: The AG treadmill provides a reduction in loading forces while maintaining normal muscle recruitment patterns. Decreased BW running preferentially unloads the hindfoot. The AG treadmill can be an effective rehabilitation tool following foot or ankle injury and may prove superior to other limited weight-bearing methods.

First iteration of a User-Centered Design process to develop an in-bed leg press.

BACKGROUND: Physical inactivity is prevalent among hospitalized patients and the daytime spent lying should be utilised for exercise. However, implementing new interventions in hospitals' complex daily routines is difficult and requires a participatory approach. OBJECTIVE: Exploring clinical settings and clinicians' perspectives regarding exercise in hospitalized patients to gauge the potential of further development of an in-bed training device and to formulate development goals. METHODS: A User-Centered Design approach was employed, consisting of work shadowing and focus groups with physiotherapists and nurses. Content and network analyses of the focus group data were performed. Personas were then developed and used to create clinical scenarios. RESULTS: Some clinicians perceived in-bed exercise counterproductive, while others recognized potential for unsupervised training. The most important design characteristics appeared to be a small size, low weight and simplicity of use to facilitate storage, transportation, and administration, respectively. The scenarios revealed that the device's use could increase the physical activity time by 1.4%, although it would also increase the working time of clinicians. CONCLUSION: The study highlighted the difficulties in developing a usable training device but encouraged the authors to pursue their efforts under the strict condition of following the formulated development goals.

Hallux Rigidus: Anatomy and Pathology.

Hallux rigidus is a common degenerative condition of the hallux metatarsophalangeal joint (MTPJ) characterized by pain, swelling, stiffness, and limited range of motion with characteristic corresponding clinical, physical examination, and radiographic findings. Many historical risks factors including trauma and family history and patient factors including hallux valgus interphalangeus and inflammatory arthropathies have a well-substantiated etiologic role in the disease process. The purpose of this section is to review the normal and pathologic anatomy and biomechanics of the hallux MTPJ while providing an overview of the current understanding and remain debate regarding the disease process.

Diurnal variation of heart rate variability in individuals with spinal cord injury.

BACKGROUND: Heart rate variability (HRV) may provide objective information about cardiogenic autonomic balance in individuals with spinal cord injury (SCI). The aim of this study was to characterize the diurnal variation of HRV in individuals with SCI at lesion level T6 and above and lesion level below T6. METHODS: This was a retrospective analysis of a prior cross-sectional study. Individuals with chronic SCI underwent 24 h recording of the time between consecutive R waves (RR interval) to derive parameters of HRV as follows: standard deviation of all normal-to-normal R-R intervals (SDNN) and square root of the mean of the squared differences between successive R-R intervals (RMSSD) (time domain); and high frequency power (HF), low-frequency power (LF), very low frequency power (VLF), ultra-low frequency power (ULF) and total power (TP) (frequency domain). Changes in the magnitude of HRV outcomes over the 24 h period were investigated using a novel multi-component cosinor model constrained to the form of a three-harmonic Fourier series. RESULTS: Participants were grouped as lesion level T6 and above (n = 22) or below T6 (n = 36). Most of them were male (n = 40, 69%) and the median age (interquartile range) was 50.5 (28) years. Both groups exhibited similar diurnal patterns in most HRV metrics. The lowest values occurred in the late afternoon (4-6 pm) and gradually increased, peaking around midnight to early morning (1-6 am). Exceptions included RMSSD, which peaked before midnight, and ULF, which showed a double peak pattern that peaked from 11 am to 1 pm and 4-6 am in participants with lesion level at T6 and above. The HRV values in participants with lesion level T6 and above were generally lower than participants with lesion level below T6, except for peak values of RMSSD, HF and LF. CONCLUSION: This study demonstrated substantial diurnal variation of HRV in participants with SCI in both groups of participants. In clinical and research settings, diurnal variations in HRV must be taken into consideration.

Playing surface and sport contact status modulate time to lower extremity musculoskeletal injury at a greater level than concussion history among collegiate student-athletes.

OBJECTIVES: While previous investigations have demonstrated a positive correlation between previous concussion and risk of subsequent lower extremity musculoskeletal injury (LEMSKI), the effect of sport- and patient-specific factors on time to injury has not been thoroughly described. This study's main objective was to evaluate the relationship between prior concussion and time to LEMSKI among a population of collegiate student-athletes. Secondary objectives were to evaluate the relationship between playing surface, sport contact status, and biologic sex on time to LEMSKI. We hypothesized that those with previous concussions, those competing on synthetic surfaces, and those competing in collision sports would experience decreased latency to LEMSKI overall. METHODS: A retrospective observational analysis of National Collegiate Athletic Association (NCAA) Division I student-athletes was conducted utilizing a mixed linear model analysis with contrasts. Inclusion criteria included participation in the Pac-12 Health Analytics Program with a documented LEMSKI between 2017 and 2020. Exclusion criteria included concurrent concussion and LEMSKI, injury resulting in serious morbidity or mortality, and incomplete medical record. Participants were classified by whether they sustained a concussion prior to LEMSKI in each athletic season. RESULTS: Of 1179 athletes included, 1140 had no previous concussion and 37 had a previous concussion. There was no observed effect of previous concussion (F â€‹= â€‹0.038; p â€‹= â€‹0.846) on time to LEMSKI overall. Student-athletes competing on constructed surfaces sustained a subsequent LEMSKI 14.5 days sooner (SE â€‹= â€‹5.255; p â€‹= â€‹0.045), and those competing on organic surfaces sustained a subsequent LEMSKI 23.5 days sooner (SE â€‹= â€‹4.018; p â€‹< â€‹0.001) in the season than those competing on synthetic surfaces. Contact sport student-athletes sustained a subsequent LEMSKI 52.1 days sooner than collision sport student-athletes (SE â€‹= â€‹5.248; p â€‹< â€‹0.001), and limited contact sport student-athletes sustained a subsequent LEMSKI 42.29 days sooner than collision sport student-athletes (SE â€‹= â€‹4.463; p â€‹< â€‹0.001). There was no observed effect of biologic sex (F â€‹= â€‹0.602; p â€‹= â€‹0.438) on time to LEMSKI overall. CONCLUSION: There was no observed impact of concussion on time on LEMSKI overall in this collegiate athletic population. Contact sports were associated with decreased time to LEMSK, while synthetic surfaces were associated with increased time to LEMSKI in this population. There was no observed impact of biologic sex on time to LEMSKI. LEVEL OF EVIDENCE: Case-control, level of evidence III.

Clinical Outcomes and Registry Data in Total Ankle Arthroplasty.

Total ankle arthroplasty (TAA) is an effective treatment for end-stage ankle arthritis consistently demonstrating good to excellent outcomes, even when considering factors such as deformity, patient age, bilaterality, and arthritis etiology. There is little consensus in the literature with regard to preferred patient-reported outcome metrics (PROMs) for assessing outcomes, although all metrics generally improve following TAA. Several countries have successful registries to track longevity of TAA in populations; however, PROMs are generally not successfully tracked in registries. A trend toward consensus on outcome metrics and collaborative registries is warranted to optimize patient selection and outcomes in TAA.

Reliability of five-minute vs. one-hour heart rate variability metrics in individuals with spinal cord injury.

Background: A previous study showed low reliability of 1-h HRV outcomes in participants with spinal cord injury (SCI), but it was not certain whether the low reliability was due to the unrestricted activity of participants. We aimed to investigate test-retest reliability of HRV metrics in individuals with SCI using a 1-h measurement in a supine position. Methods: Individuals with SCI underwent two sessions of 1-h recording of the time between consecutive R waves (RR-intervals) in a supine position. HRV outcomes were obtained from a single 5-min data segment and for the full 1-h recording. HRV parameters of interest were: standard deviation of all normal-to-normal R-R intervals (SDNN) and square root of the mean of the squared differences between successive R-R intervals (RMSSD) (time domain); and high frequency power (HF), low frequency power (LF), very low frequency power (VLF), ultra-low frequency power (ULF) and total power (TP) (frequency domain). Relative reliability was assessed by intraclass correlation coefficient (ICC). Absolute reliability was assessed by coefficient of variation (CV) and Bland-Altman limits of agreement (LoA). Results: Data from 37 individuals (14 with tetraplegia and 23 with paraplegia) were included. Relative reliability was higher for the 1-h (ICCs ranged from 0.13-0.71) than for the 5-min duration (ICCs ranged from 0.06-0.50) in the overall SCI group for all HRV metrics. Participants with tetraplegia had lower relative reliability compared to participants with paraplegia in all HRV metrics for the 5-min duration (ICCs ranged from -0.01-0.34 vs. 0.21-0.57). For the 1-h duration, participants with paraplegia showed higher relative reliability than participants with tetraplegia in all HRV metrics (ICCs ranged from 0.18-0.79 vs. 0.07-0.54) except TP (ICC 0.69 vs. 0.82). In terms of absolute reliability, the CVs and LoAs for the 1-h duration were better than for the 5-min duration. In general, time domain metrics showed better reliability than frequency domain metrics for both durations in participants with tetraplegia and paraplegia. The lowest CV and narrowest 95% LoA were found for SDNN in 5-min and 1-h durations overall and in both lesion levels. Conclusions: The supine position did not provide better reliability compared to unrestricted activity in participants with SCI. HRV analysis using a 5-min duration is of limited value in SCI due to poor reliability. For the 1-h analysis duration, interpretation of the reliability of HRV varies according to lesion level: it is recommended to take lesion level into account when interpreting reliability measures.

Talus Idiopathic Versus Stress-Injury-Related Osteonecrosis and Its Resolution: A Case Report.

A 34-year-old healthy long-distance runner sustained a possible stress injury to the talus. This injury progressed into osteonecrosis (ON) or might have presented idiopathically. This patient had a complete normal metabolic workup. Non-surgical management, including resting, activity modification, and bone stimulators, led to resolution. Serial exams and magnetic resonance imaging demonstrated gradual resolution of the ON. At two years old, she was pain-free and had returned to running. Talus ON is uncommon and even more so in the absence of metabolic disorders or precipitating trauma. This case presents a debatable stress injury, an overuse injury, or even an idiopathic ON. It healed with non-surgical management. Serial, advanced imaging surveillance was implemented. There is a lack of impactful literature regarding the management of early ON and a paucity of strong recommendations to guide non-surgical treatment options in the early stages. This presentation is quite debatable as to whether there was a stress fracture leading to ON or if it was idiopathic ON. Yet, these entities could easily overlap, and physicians and orthopedists should be aware.