Valerie M. Cox

Isometric and isotonic muscle properties as determinants of work loop power output

The power output of rabbit latissimus dorsi muscle was calculated under isotonic conditions and during oscillatory work. Isotonic shortening studies yielded a maximum power output of 120 W·kg−1 at a P/P0 of 0.4 compared to a maximum power output of 32 W·kg−1 obtained using the work loop technique. This difference can largely be explained by comparing actual work loops with those constructed using force velocity (P/V) and isometric data. At low cycle frequencies, work loop power output is quite close to that predicted from P/V and isometric data. However, at higher frequencies other dynamic muscle properties appear to exert a more marked effect.

The induction of c‐fos and c‐jun in the stretched latissimus dorsi muscle of the rabbit: responses to duration, degree and re‐application of the stretch stimulus

The mRNA levels of the proto‐oncogenes c‐fos and c‐jun were measured in the rabbit latissimus dorsi (LD) muscle in response to the application of various stretch regimes in vivo. It was shown that it was necessary for the stretch to be applied continuously over 1 h in order to achieve full induction of c‐fos and c‐jun mRNA at 1 h. In addition, a correlation was demonstrated between the degree of stretch imposed on the LD and the induced levels of c‐fos and c‐jun mRNA. Moreover, a second induction of these genes occurred when the LD was subjected to a second stretch stimulus. The magnitude and time course of the second response depended on the precise timing of the second stimulus in relation to the initial induction.

Growth Induced by Incremental Static Stretch in Adult Rabbit Latissimus Dorsi Muscle

Incrementally applied static stretch over 3 weeks resulted in a 72% increase in the weight of the in situ latissimus dorsi muscle in rabbits. True growth rather than tissue oedema was confirmed by increases in the protein content (130%), the cross‐sectional area of the type I fibres (30%) and the muscle length (i.e. number of sarcomeres in series increased 25%). Despite an increase in the proportion of fibres staining positive for the enzyme succinate dehydrogenase (SDH), the myosin ATPase stain showed no appreciable fibre type transformation. While total power output in the stretched muscle was unchanged, its maximum mass specific power output, as determined by oscillatory work loops, was decreased by 50%. The cross‐sectional area that was occupied by connective tissue increased from 15 to 19% in the stretched muscles, with a concomitant increase in passive energy dissipation. Some incrementally stretched muscles were then allowed an additional 3 weeks of maintained stretch to determine whether the adaptive changes would be preserved or reversed. Previous gains in muscle weight, length and area of type I fibres all remained. In contrast, the connective tissue content and the passive properties returned to control values during this period.

Low socio-economic environmental determinants of children's physical activity in Coventry, UK: a qualitative study in parents

Background Childrens physical activity (PA) is affected by socio-economic status (SES) and the environment. Children are not fully autonomous in their decision making; parental decisions thus affect how children utilise their surrounding environments for PA. The aim was to examine environmental influences on childrens PA from a qualitative perspective in parents from low SES wards in Coventry, UK. Method 59 parents of children in year 4 (aged 8–9years) completed the ALPHA environmental questionnaire. 16 of these parents took part in focus group discussions examining environmental facilitators and barriers to their childs PA (March–April, 2013). Results Emerging themes related to physical (i.e. poor access, safety and quality of the neighbourhood) and social environment (i.e. ‘rough’ neighbourhood due to crime and anti-social behaviour) influences on the PA behaviour of children. The parents believed these environmental factors resulted in the children engaging in greater sedentary activity (watching TV) indoors. The school environment was perceived as a supportive physical environment for childrens PA behaviour. Conclusion Parents perceptions of an unsupportive physical and social environment restrict childrens opportunities to play outside and be physically active and may lead to increased body fat (BF). Schools provide a supportive environment for children from low SES to be physically active in.

Physical activity patterns of ethnic children from low socio-economic environments within the UK

Abstract Many children fail to meet physical activity (PA) guidelines for health benefits. PA behaviours are complex and depend on numerous interrelated factors. The study aims to develop current understanding of how children from low Socio-economic environments within the UK use their surrounding built environments for PA by using advanced technology. The environment was assessed in 96 school children (7–9 years) using global positioning system (GPS) monitoring (Garmin Forerunner, 305). In a subsample of 46 children, the environment and PA were assessed using an integrated GPS and heart rate monitor. The percentage of time spent indoor, outdoor, in green and non-green environments along with time spent in moderate-to-vigorous PA (MVPA) in indoor and outdoor environments were assessed. A 2-by-2 repeated measures analysis of covariance, controlling for body mass index, BF%, assessed the environmental differences. The findings show that 42% of children from deprived wards of Coventry fail to meet PA guidelines, of which 43% was accumulated during school. Children engaged in more MVPA outdoor than indoor environments (P < 0.01) and a greater amount of time was spent in non-green environments (P < 0.01). Increased time outdoors was negatively associated with BF%. In conclusion, outdoor environments are important for health-enhancing PA and reducing fatness in deprived and ethnic children.

Human monocyte heat shock protein 72 responses to acute hypoxic exercise after 3 days of exercise heat acclimation

The aim of this study was to determine whether short-term heat acclimation (STHA) could confer increased cellular tolerance to acute hypoxic exercise in humans as determined via monocyte HSP72 (mHSP72) expression. Sixteen males were separated into two matched groups. The STHA group completed 3 days of exercise heat acclimation; 60 minutes cycling at 50% V˙O2peak in 40°C 20% relative humidity (RH). The control group (CON) completed 3 days of exercise training in 20°C, 40% RH. Each group completed a hypoxic stress test (HST) one week before and 48 hours following the final day of CON or STHA. Percentage changes in HSP72 concentrations were similar between STHA and CON following HST1 (P = 0.97). STHA induced an increase in basal HSP72 (P = 0.03) with no change observed in CON (P = 0.218). Basal mHSP72 remained elevated before HST2 for the STHA group (P < 0.05) and was unchanged from HST1 in CON (P > 0.05). Percent change in mHSP72 was lower after HST2 in STHA compared to CON (P = 0.02). The mHSP72 response to hypoxic exercise was attenuated following 3 days of heat acclimation. This is indicative of improved tolerance and ability to cope with the hypoxic insult, potentially mediated in part by increased basal reserves of HSP72.

An integrated curriculum approach to increasing habitual physical activity in deprived South Asian children.

Abstract Integrating physical activity (PA) within a school curriculum is a promising approach for increasing PA in children. To date, no research has examined its effectiveness in increasing the low levels of PA witnessed in deprived South Asian (SA) children. The study aims to ascertain whether an integrated school-based curriculum and pedometer intervention could increase PA in children from deprived SA backgrounds. Following ethical approval and informed consent, 134 deprived SA children (63 boys, 71 girls, control (n = 40, mean age = 11.12 years, SD = 0.32 years) and intervention (n = 94, mean age = 9.48 years, SD = 0.62 years)) from a primary school in England, UK, completed a 6-week integrated PA intervention based on virtually walking from their school (middle of the country) to the coast and back (March–July 2013). Habitual PA was determined at baseline and post 6 weeks intervention for both groups, and determined weekly during the intervention in the experimental group. The results indicated that average daily steps were significantly higher at post 6 weeks compared to baseline for the intervention group (intervention mean change = 8694 steps/day, SD = 7428 steps/day vs. control mean change = −1121 steps/day, SD = 5592 steps/day, 95% CI of difference, 6726–7428 steps/day, P = .001, d = 1.76). In addition, significant decreases in BF% and waist circumference were observed in the intervention group post 6 weeks (mean change for BF% = −4.5%, mean change for WC = −1.7 cm, P = .001). School-based integrated curriculum and pedometer interventions provide a feasible and effective mechanism for increasing habitual PA in primary school children from deprived SA backgrounds.