Physical Activity Patterns in Frail and Nonfrail Patients With End-Stage Liver Disease.

Background: Frailty commonly complicates cirrhosis and is associated with poorer outcomes. While patients with cirrhosis may be sedentary, there are few comprehensive descriptions of their physical activity (PA) patterns related to frailty. Our aim was to identify PA characteristics that may be used in interventions to improve PA and reduce frailty. Methods: In a cross-sectional cohort study, forty patients with cirrhosis (mean age 63; 30 nonfrail, 10 frail) wore an accelerometer/thermal sensing armband for 7 days. Postural status (e.g., upright movement, upright sedentary, lying down), Metabolic Equivalent of Tasks (METs) and active bouts were identified. Results: Patients were highly sedentary most of the time (89 ± 7% and 85 ± 10% of the day, in frail and nonfrail cirrhotics, respectively). Compared with nonfrail cirrhotics, frail patients spent significantly shorter amount of time moving in an upright position (7% ± 5 vs. 12% ± 5, P = 0.013 in frail and nonfrail cirrhotics, respectively), had significantly fewer and shorter durations of active bouts per day (number of active bouts: 9 ± 12 vs. 19 ± 14; duration: 13.2 ± 1.5 min and 15.9 ± 2.6 min in frail and nonfrail cirrhotics, respectively), and had a lower amount of steps per wear time hours (41.7 ± 37.1 vs. 116.8 ± 85.4, P = 0.003 in frail and nonfrail, respectively). Traditional measures such as METs or aerobic bouts did not differ between groups. Conclusions: Active bout measures, as opposed to more traditional measures such as METs, differentiate between frail and nonfrail cirrhotics suggesting they may be used to assess changes resulting from targeted interventions to improve physical activity.

Years of running experience influences stride-to-stride fluctuations and adaptive response during step frequency perturbations in healthy distance runners.

RESEARCH QUESTION: The current study investigated stride-to-stride fluctuations of step rate and contact time in response to enforced step frequency perturbations as well as adaptation and de-adaptation behavior. METHODS: Forty distance runners ran at a self-selected speed and were asked to match five different enforced step frequencies (150, 160, 170, 180, and 190 beats per min). The influence of experience was explored, because running is a skill that presumably gets better with practice, and increased years of running experience is protective against injury. Detrended fluctuation analysis was used to determine the strength of long-range correlations in gait fluctuations at baseline, during the perturbation, and post-perturbation. Adaptive response was measured by the ability to match, rate of matching, and aftereffect of step frequency perturbations. RESULTS: The structure of stride-to-stride fluctuations for step rate and contact time did not change during the perturbation or post-perturbation compared to baseline. However, fluctuations in step rate were affected by the level of perturbation. Runners with the most experience had a less persistent structural gait pattern for both step rate and contact time at baseline. Highly experienced runners also demonstrated the best adaptive response. They better matched the enforced step frequency, reached the enforced step frequency sooner, and returned to preferred step frequency more quickly following removal of the perturbation. SIGNIFICANCE: These findings indicate baseline locomotor flexibility may be beneficial to achieve task demands and return to a stable state once the task is complete. Increased locomotor flexibility may also be a contributing factor for reduced injury risk in experienced runners.

Segment Coordination Variability Differs by Years of Running Experience.

Running is a popular activity that results in high rates of overuse injury, with less-experienced runners becoming injured at higher rates than their more-experienced peers. Although measures of joint kinematics and kinetics and ground reaction forces have been associated with overuse running injuries, similar differences across levels of running experience have not been found. Because running is a motor skill that may develop with experience, an analysis of segment coordination and its variability could provide additional insight into why injury incidence decreases with increasing experience. PURPOSE: The purpose of this study was to determine if less-experienced runners have different segment coordination and lower segment coordination variability compared with their more-experienced peers. METHODS: This retrospective analysis included 20 more-experienced (≥10 yr running) and 21 less-experienced (≤2 yr running) runners. Sagittal thigh versus shank and shank versus foot segment coordination and coordination variability were calculated using a modified vector coding approach as individuals ran on a treadmill at preferred pace. Coordination and its variability were compared between groups during terminal swing and early, mid, and late stance for both segment couples. RESULTS: Segment coordination was similar between less- and more-experienced runners. Less-experienced runners had lower segment coordination variability compared with more-experienced runners for both the thigh versus shank and shank versus foot couples. This lower variability occurred during early and mid stance. CONCLUSIONS: Runners appeared to attain stable segment coordination patterns within 2 yr of consistent running, but had lower coordination variability compared with individuals who had been running for 10 or more years. These results suggest that assessment of movement patterns and their flexibility may help inform injury prevention or treatment strategies for less-experienced runners.

Experience does not influence injury-related joint kinematics and kinetics in distance runners.

PURPOSE: Increased running experience and more time spent running appears to be advantageous in reducing injury risk, although the reason behind this is unclear. It is plausible that more experience results in better running mechanics leading to less injuries. Running mechanics are often screened during clinical assessments and targeted for correction in gait retraining, particularly those thought to be global indicators of injury or those associated with elevated knee joint loading. Examining the biomechanics of runners who are less-injury prone can improve our understanding of the significance of faulty running mechanics in relation to injury. Our goal was to examine if running experience was correlated to differences in kinematics and kinetics associated with increased knee joint loading and running-related injury risk. METHODS: One hundred runners with varying experience ran on a pressure-sensing treadmill at a self-selected speed. Trunk and lower extremity kinematics, spatiotemporal measures, and ground reaction forces were collected. Multiple linear regression was used to assess the association between experience and three-dimensional hip kinematics, sagittal plane lower-extremity mechanics, and ground reaction forces while controlling for age and speed. RESULTS: Increased running experience was not significantly associated with running mechanics. Increased age was significantly associated with reduced peak knee flexion and increased contact time. Running speed influenced several spatiotemporal, kinematic, and kinetic variables. CONCLUSION: Increased years of running experience does not appear to significantly influence running mechanics. However, age and running speed do influence biomechanical variables associated with injury in distance runners. Thus, there may be factors, other than running mechanics, that contribute to less risk in more experienced runners.

Hair follicle neogenesis induced by cultured human scalp dermal papilla cells.

AIM: To develop a method by which human hair follicle dermal papilla (DP) cells can be expanded in vitro while preserving their hair-inductive potential for use in follicular cell implantation, a cellular therapy for the treatment of hair loss. MATERIALS & METHODS: DP cells were isolated from scalp hair follicles in biopsies from human donors. DP cell cultures were established under conditions that preserved their hair-inductive potential and allowed for significant expansion. The hair-inductive potential of cells cultured for approximately 36 doublings was tested in an in vivo flap-graft model. In some experiments, DiI was used to label cells prior to grafting. RESULTS: Under the culture conditions developed, cultures established from numerous donors reproducibly resulted in an expansion that averaged approximately five population doublings per passage. Furthermore, the cells consistently induced hair formation in an in vivo graft assay. Grafted DP cells appeared in DP structures of newly formed hairs, as well as in the dermal sheath and in the dermis surrounding follicles. Induced hair follicles persisted and regrew after being plucked 11 months after grafting. CONCLUSION: A process for the propagation of human DP cells has been developed that provides significant expansion of cells and maintenance of their hair-inductive capability, overcoming a major technical obstacle in the development of follicular cell implantation as a treatment for hair loss.