In this task, you are given a passage which has a question and the context. You have to generate an answer to the question based on the information present in the context.
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Question: Context: Recent work has identified deficits in dual-task gait balance control for up to 2 months after adolescent concussion; however, how resumption of preinjury physical activities affects recovery is unknown.', 'The objective of this study is to examine how return to activity (RTA) affects recovery from concussion on measures of symptom severity, cognition, and balance control during single-task and dual-task walking.', 'Nineteen adolescents with concussion who returned to preinjury activity within 2 months after injury and 19 uninjured, matched controls completed symptom inventories, computerized cognitive testing, and single-task and dual-task gait analyses. Concussion participants were assessed at five time points: within 72 h, 1 wk, 2 wk, 1 month, and 2 months postinjury. Control participants were assessed at the same time points as their matched concussion counterparts. RTA day was documented as the postinjury day in which physical activity participation was allowed. The effect of returning to physical activity was assessed by examining the percent change on each dependent variable across time before and directly after the RTA. Data were analyzed by two-way mixed effects ANOVAs.', 'After the RTA day, concussion participants significantly increased their total center-of-mass medial/lateral displacement (P = 0.009, ηp = .175) and peak velocity (P = 0.048, ηp = 0.104) during dual-task walking when compared with pre-RTA data, whereas no changes for the concussion group or between groups were detected on measures of single-task walking, forward movement, or cognition.\Question: Does return to activity after concussion affect dual-task gait balance control recovery?

Answer: Adolescents with concussion displayed increased center-of-mass medial/lateral displacement and velocity during dual-task walking after RTA, suggesting a regression of recovery in gait balance control. This study reinforces the need for a multifaceted approach to concussion management and continued monitoring beyond the point of clinical recovery.


Question: Context: The aim of this study was the analysis of total, early and late complications following venous access port implantation between 1998 and 2008 at the Department of Surgery of the University of Rostock, Germany. A comparison between different implantation techniques addressing success rate, complication rate and duration of operation was performed. These results were further analysed in regard to the level of training of the participating surgeons.', 'A retrospective analysis of 1423 venous access port implantations between 1998 and 2008 was performed.', "The rate of total complications was 13.8%. Among 4.7% early complications pneumothorax was the most common. The rate of late complications was 9.1%. Most common were infection (4.9%) followed by dysfunction of the catheter (3.5%). 1322 venous access port implantations were performed using puncture of the subclavian vein and Seldinger's technique. 101 operations were performed by direct access through dissection of the cephalic vein and open introduction of the catheter. Operation time in the open group was significantly longer than in the puncture group (46.5\u2009min vs. 38.7\u2009min, p\u2009=\u20090.005). There were significantly more late complications (9.6% vs. 2%, p\u2009=\u20090.01) and total complications (14.5% vs. 4%, p\u2009=\u20090.005) in the puncture group vs. the open access group. Primary success rates of open access vs. puncture were 100% and 96.8%, respectively. The rate of complications was independent of the experience status of the surgeon. However, the rate of total and late complications significantly decreases with number of performed operations.\Question: Is [ Venous Access Port Implantation an Ideal Teaching Operation - An Analysis of 1423 Cases ]?

Answer: Venous port implantation is a relatively simple procedure despite its possible complications. An open access technique is safer than puncture. The rate of complications significantly decreases with increasing number of performed operations. Therefore venous port implantation and especially the open access method is an ideal teaching operation in a structured surgical training programme.


Question: Context: Paired electrical stimulation and postextrasystolic potentiation (PESP) of contractility has been extensively studied in ventricular myocardium, but less is known about PESP of atrial contractility. Our aim was to determine whether PESP of atrial contractility could augment left ventricular (LV) preload and improve LV systolic performance.', 'A paired electrical stimulus closely following the pacing stimulus was applied to isolated atrial and ventricular myocardium from 4 dog hearts, and the interval dependent force potentiation was examined. In isolated atrial myocardium, paired pacing increased the active tension from a baseline of 1.36 +/- 0.23 to 2.60 +/- 0.57 g/mm(2); in ventricular myocardium active tension increased from 2.58 +/- 0.42 to 3.81 +/- 0.27 g/mm(2) (both P <.01). Then, LV pressure (micromanometer) and segment length (ultrasonic crystals) were measured in the intact hearts of 7 anesthetized dogs in which premature stimuli were applied to the atrium. In intact hearts, paired pacing of the atrium (coupling interval 200 ms) increased LV end-diastolic pressure from 3.8 +/- 1.0 to 6.4 +/- 1.0 mm Hg; systolic pressure increased from 105 +/- 6 to 112 +/- 7 mm Hg (both P <.05). LV pressure-length loop area (regional stroke work) increased 10.5 +/- 0.2%.\Question: Does potentiation of atrial contractility by paired pacing augment ventricular preload and systolic performance?

Answer:
Isolated atrial myocardium exhibits substantial PESP of contractility, which is similar to ventricular myocardium. In the intact heart, atrial PESP augments LV systolic performance by effecting an increase in LV preload. This technique may provide a means of improving cardiac performance in patients with heart failure.