Investigating the impact of London's ultra low emission zone on children's health: children's health in London and Luton (CHILL) protocol for a prospective parallel cohort study.

BACKGROUND: Air pollution harms health across the life course. Children are at particular risk of adverse effects during development, which may impact on health in later life. Interventions that improve air quality are urgently needed both to improve public health now, and prevent longer-term increased vulnerability to chronic disease. Low Emission Zones are a public health policy intervention aimed at reducing traffic-derived contributions to urban air pollution, but evidence that they deliver health benefits is lacking. We describe a natural experiment study (CHILL: Children's Health in London and Luton) to evaluate the impacts of the introduction of London's Ultra Low Emission Zone (ULEZ) on children's health. METHODS: CHILL is a prospective two-arm parallel longitudinal cohort study recruiting children at age 6-9 years from primary schools in Central London (the focus of the first phase of the ULEZ) and Luton (a comparator site), with the primary outcome being the impact of changes in annual air pollutant exposures (nitrogen oxides [NOx], nitrogen dioxide [NO2], particulate matter with a diameter of less than 2.5micrograms [PM2.5], and less than 10 micrograms [PM10]) across the two sites on lung function growth, measured as post-bronchodilator forced expiratory volume in one second (FEV1) over five years. Secondary outcomes include physical activity, cognitive development, mental health, quality of life, health inequalities, and a range of respiratory and health economic data. DISCUSSION: CHILL's prospective parallel cohort design will enable robust conclusions to be drawn on the effectiveness of the ULEZ at improving air quality and delivering improvements in children's respiratory health. With increasing proportions of the world's population now living in large urban areas exceeding World Health Organisation air pollution limit guidelines, our study findings will have important implications for the design and implementation of Low Emission and Clean Air Zones in the UK, and worldwide. CLINICALTRIALS: GOV: NCT04695093 (05/01/2021).

Device-Measured Change in Physical Activity in Primary School Children During the UK COVID-19 Pandemic Lockdown: A Longitudinal Study.

BACKGROUND: Lockdown measures, including school closures, due to the COVID-19 pandemic have caused widespread disruption to children's lives. The aim of this study was to explore the impact of a national lockdown on children's physical activity using seasonally matched accelerometry data. METHODS: Using a pre/post observational design, 179 children aged 8 to 11 years provided physical activity data measured using hip-worn triaxial accelerometers worn for 5 consecutive days prepandemic and during the January to March 2021 lockdown. Multilevel regression analyses adjusted for covariates were used to assess the impact of lockdown on time spent in sedentary and moderate to vigorous physical activity. RESULTS: A 10.8-minute reduction in daily time spent in moderate to vigorous physical activity (standard error: 2.3 min/d, P < .001) and a 33.2-minute increase in daily sedentary activity (standard error: 5.5 min/d, P < .001) were observed during lockdown. This reflected a reduction in daily moderate to vigorous physical activity for those unable to attend school (-13.1 [2.3] min/d, P < .001) during lockdown, with no significant change for those who continued to attend school (0.4 [4.0] min/d, P < .925). CONCLUSION: These findings suggest that the loss of in-person schooling was the single largest impact on physical activity in this cohort of primary school children in London, Luton, and Dunstable, United Kingdom.

Multiday load carriage decreases ability to mitigate ground reaction force through reduction of ankle torque production.

The aim of this study was to examine the impact of backpack load carriage on lower limb strength and loading rate change in a cohort that match military recruit profiles. Twenty-six participants walked on a treadmill either carrying a military load carriage system (32 kg) or unloaded for 2 h on two consecutive days. Participants ground reaction forces and strength measures were assessed using a force platform and dynamometry, respectively. Testing included assessments before and after treadmill walking on days one and two, and 24 h following day 2. When assessed by mixed methods ANOVA (alpha: 0.05) statistically significant interaction effects were observed for loading peak (p = 0.031), loading rate (p = 0.035) and plantarflexor torque dynamometry variables at 60°s-1 (p = 0.011) and 120°s-1 (p = 0.024). Repeated measures correlation highlighted associations between plantarflexor torque at 60°s-1 and loading rate (r = -0.901, p < 0.001). Load carriage reduced lower limb torque which did not recover between days. Plantarflexor torque reductions were associated with increases in loading rate. Practitioners should consider that load bearers are more likely to experience lower limb injury during multi-day load carriage. Future work should develop protocols to reduce plantarflexor torque loss in order to reduce ground reaction force change.

Convergent Validity of Ratings of Perceived Exertion During Resistance Exercise in Healthy Participants: A Systematic Review and Meta-Analysis.

BACKGROUND: The validity of ratings of perceived exertion (RPE) during aerobic training is well established; however, its validity during resistance exercise is less clear. This meta-analysis used the known relationships between RPE and exercise intensity (EI), heart rate (HR), blood lactate (BLa), blood pressure (BP) and electromyography (EMG) to determine the convergent validity of RPE as a measure of resistance exercise intensity and physiological exertion, during different forms of resistance exercise. Additionally, this study aims to assess the effect of several moderator variables on the strength of the validity coefficients, so that clearer guidance can be given on the use of RPE during resistance exercise. METHODS: An online search of 4 databases and websites (PubMed, Web of Science SPORTDiscus and ResearchGate) was conducted up to 28 February 2020. Additionally, the reference lists of the included articles were inspected manually for further unidentified studies. The inclusion criteria were healthy participants of any age, a rating scale used to measure RPE, resistance exercise of any type, one cohort receiving no other intervention, and must present data from one of the following outcome measures: EI, HR, BP, EMG or BLa. Weighted mean effect sizes (r) were calculated using a random-effects model. Heterogeneity was assessed using the τ2 and I2 statistics. Moderator analysis was conducted using random-effects meta-regression. RESULTS: One-hundred and eighteen studies were included in the qualitative synthesis, with 75 studies (99 unique cohorts) included in the meta-analysis. The overall weighted mean validity coefficient was large (0.88; 95% CI 0.84-0.91) and between studies heterogeneity was very large (τ2 = 0.526, I2 = 96.1%). Studies using greater workload ranges, isometric muscle actions, and those that manipulated workload or repetition time, showed the highest validity coefficients. Conversely, sex, age, training status, RPE scale used, and outcome measure no significant effect. CONCLUSIONS: RPE provides a valid measure of exercise intensity and physiological exertion during resistance exercise, with effect sizes comparable to or greater than those shown during aerobic exercise. Therefore, RPE may provide an easily accessible means of prescribing and monitoring resistance exercise training. Trial Registration The systematic review protocol was registered on the PROSPERO database (CRD42018102640).

Center of Pressure, Vertical Ground Reaction Forces, and Neuromuscular Responses of Special-Forces Soldiers to 43-km Load Carriage in the Field.

The primary purpose of this study was to examine lateral deviations in center of pressure as a result of an extreme-duration load carriage task, with particular focus on heel contact. A total of 20 (n = 17 males and n = 3 females) soldiers from a special operation forces unit (body mass 80.72 [21.49] kg, stature 178.25 [8.75] cm, age 26 [9] y) underwent gait plantar pressure assessment and vertical jump testing before and after a 43-km load carriage event (duration 817.02 [32.66] min) carrying a total external load of 29.80 (1.05) kg. Vertical jump height decreased by 18.62% (16.85%) from 0.30 (0.08) to 0.24 (0.07) m, P < .001. Loading peak and midstance force minimum were significantly increased after load carriage (2.59 [0.51] vs 2.81 [0.61] body weight, P = .035, Glass delta = 0.44 and 1.28 [0.40] vs 1.46 [0.41] body weight, P = .015, Glass delta = 0.45, respectively) and increases in lateral center of pressure displacement were observed as a result of the load carriage task 14.64 (3.62) to 16.97 (3.94) mm, P < .029. In conclusion, load carriage instigated a decrease in neuromuscular function alongside increases in ground reaction forces associated with injury risk and center of pressure changes associated with ankle sprain risk. Practitioners should consider that possible reductions in ankle stability remain once load carriage has been completed, suggesting soldiers are still at increased risk of injury even once the load has been removed.