Alison Williams

IntroductionThe pelvic floor muscles are active during motor tasks that increase intra-abdominal pressure, but little is known about how the PFM respond to dynamic activities, such as gait. The purpose of this study was to characterize and compare PFM activity during walking and jogging in continent adults across the entire gait cycle.Methods17 able-bodied individuals with no history of incontinence participated in this study. We recorded electromyography from the abdominal muscles, gluteus maximus, and PFM while participants performed attempted maximum voluntary contractions of all muscles and completed 60–70 strides in four gait conditions: slow walk ; regular walk ; transition walk ; jog. We quantified activity throughout the whole gait cycle and during periods of bursting for each participant, and analyzed the timing of PFM bursting periods to explore when the PFM were most active in the gait cycle. We also conducted a phase metric analysis on the PFM and GM burst timings. We performed a Spearman's rank-order correlation to examine the effect of speed on %aMVCGC, %aMVCBR, and phase metric score, and used the Wilcoxon Signed-Rank test to evaluate the effect of gait modality, matched for speed, on these variables.ResultsThe PFM were active throughout the gait cycle, with bursts typically occurring during single-leg support. The PFM and GM were in phase for 44–69% of the gait cycle, depending on condition. There was a positive correlation between gait speed and both %aMVCGC and %aMVCBR. Phase metric scores were significantly higher during jogging than transition walking, but there was no difference between gait modality on %aMVCGC or %aMVCBR. Where possible we disaggregated data by sex, although were unable to make statistical comparisons due to low sample sizes.ConclusionThe PFM are active during walking and jogging, with greater activity at faster speeds and with bursts in activity around single-leg support. The PFM and GM co-activate during gait, but are not completely in phase with each other.

Why does the air-target and its associated practices matter? This special section is about the politics, practices and ethics surrounding the target and efforts to subvert or circumvent them. Since Eyal Weizman’s groundbreaking essay on the ‘politics of verticality’ in 2002, there have been numerous attempts to critically open up the aerial gaze, but rarely have they come together for sustained analysis and critique, to explore the implications of the air-target’s techniques, processes, visual cultures and aesthetics for politics and life itself. This special section brings together leading international experts in order to open out a fuller and more complete analysis of the kinds of tensions of verticality that lie at the heart of today’s warfare, security and politics. This introduction outlines three dominant problematics of the air-target, which the articles in the section will go on to explore in more detail.