A Model of Brain Circulation and Metabolism: NIRS Signal Changes during Physiological Challenges

We construct a model of brain circulation and energy metabolism. The model is designed to explain experimental data and predict the response of the circulation and metabolism to a variety of stimuli, in particular, changes in arterial blood pressure, CO2 levels, O2 levels, and functional activation. Significant model outputs are predictions about blood flow, metabolic rate, and quantities measurable noninvasively using near-infrared spectroscopy (NIRS), including cerebral blood volume and oxygenation and the redox state of the CuA centre in cytochrome c oxidase. These quantities are now frequently measured in clinical settings; however the relationship between the measurements and the underlying physiological events is in general complex. We anticipate that the model will play an important role in helping to understand the NIRS signals, in particular, the cytochrome signal, which has been hard to interpret. A range of model simulations are presented, and model outputs are compared to published data obtained from both in vivo and in vitro settings. The comparisons are encouraging, showing that the model is able to reproduce observed behaviour in response to various stimuli

Reflex activity of pelvic floor muscles during drop landings and mini-trampolining—exploratory study

Introduction Complex functional movements such as jumping typically provoke stress urinary incontinence (SUI) in women. The aim of this study was to investigate pelvic floor muscle (PFM) activity in young, healthy women during jumps to explore their activity characteristics. Methods Surface electromyography (EMG) from PFMs was measured in 16 healthy women with a tripolar vaginal probe during drop landings from heights of 15, 30 and 45 cm (DL 15, 30, 45) as well as during mini-trampolining with a pace of 90 and 75 jumps per minute (MT 90, 75). Time of foot strike and body weight force (BWF) in % (= ground reaction force, normalised to body weight) was determined by force plates. Root mean square values of the EMG signals were analyzed from 30 ms before to 150 ms after foot strike. Peak activity during maximum voluntary contraction (MVC) was set as 100% for EMG normalization. The PFM onset threshold was determined as the mean of rest activity plus 2 standard deviations. Data were analysed with non-parametric statistical methods. Results EMG activity during all jumps was above the PFM onset threshold. Mean pre- and reflex activity increased significantly with jumping height (p < 0.05) as well as with increasing BWF. The PFM activation pattern of DL was with peak activity of 115–182 %MVC between 34 and 44 ms after foot strike, which was different from MT with peak PFM activity of 85–115 %MVC reached at 133 ms. Conclusions Jumping and mini-trampolining provoked significant PFM activity in healthy volunteers. The next research step will be to examine the PFM activity of women suffering from SUI during jumps. Keywords Electromyography Ground reaction force High impact Jump Stress urinary incontinenc