The purpose of this study is to assess the fundamental characteristics that cause a football to spin in a curve ball kick due to impact conditions, and then to examine how the change in spin affects the flight of the ball. Two experimental trials were carried out to examine the aerodynamic properties of footballs during flight. In the first trial, a football was projected with no spin at varying launch velocities and the trajectory of each flight measured and analysed. A drag coefficient was calculated for each test, based on a trajectory model. The second trial involved a football being fired with the same launch velocity, but varying spin conditions (spin axis horizontal in all cases). Again, the trajectory of each flight was measured and drag and lift coefficients were calculated. This information was used to simulate three typical game situations and the effects of foot impact offset distance and weather conditions were examined.

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To assess the effect of technology on sport, the performance statistics for four disciplines were analysed: the 100-m sprint, pole vault, javelin, and cycling. The concept of a performance improvement index was developed to allow comparison between athletes and between sports with a higher index indicating a greater improvement in the sport. The following performance improvement indices were found: 100-m sprint, 24% over 108 years; pole vault, 86% over 94 years; javelin, 95% over 76 years; 4-km individual pursuit, 35% over 32 years; one-hour cycling record, 221% over 111 years. Around 4% of the index for the sprint was attributed to tighter, aerodynamic clothing, suggesting that general athletic improvement in sprint-type events has been around 20%. Technological developments in simple equipment such as the pole vault or javelin were seen to affect the index by around 30%, while the index associated with aerodynamic improvements in the one-hour record was around 100%. It is concluded that the performance improvement index could be extended to amateur as well as elite sport where distance or time is used as a measure of performance.

The purpose of this study is to assess the fundamental characteristics which cause a football to spin in a curve ball kick. The ball impact process was analysed initially with a high speed video camera running at 4500 frames per second to obtain the basic data for a computer simulation model. This simulation model showed suitable agreement although it slightly deteriorated during the latter half of impact. It was noted that rotation of the ball occurs, even if the kinetic coefficient of friction is nearly equal to 0 because of local deformation of the ball during impact around the foot allowing forces to be transmitted to the ball around its axis. The spin of the ball was found to increase with the offset distance between the foot and the axis of the ball and as the kinetic coefficient of friction was increased. The offset distance between the foot and the axis of the ball affects the spin more than the coefficient of friction. Varying the coefficient of friction from 0.0 to 1.0 produces an increase in spin of 13 rad s−1 at most. It was suggested that the most suitable offset distance, which makes the largest ball rotation was around 100 mm. A trade‐off was found between the ball speed and spin, for different offset distances.

Analysis of results from the four major tennis tournaments shows that the percentage of tie breaks in the men’s game has been increasing over the last 30 years. It is hypothesised that this is due to the increasing speed of the serve in the game. There was found to be a significant difference in tie breaks between slower clay surfaces and faster grass surfaces. The women’s game, on the other hand, showed no increase in tie‐breaks and no difference in the number of tie‐breaks between court surfaces. A larger tennis ball was assessed to see its effect in slowing the game down. Standard and 6% larger pressurised tennis balls were used in experiments to study impacts with a fixed and a freely suspended tennis racket. The coefficient of restitution of the larger ball was found to be larger in the fixed racket tests and analysis of a serve showed that the larger ball would be served marginally faster than a standard sized ball. Drag forces on tennis balls in flight were analysed by mounting tennis balls in a wind tunnel at wind speeds up to 66.6 ms−1 (150 mph). It was found that different brands of standard size tennis ball and a larger tennis ball had a drag coefficient of approximately 0.55. Raising or reducing the nap of the ball changed the drag coefficient by about 10%. Impact experiments of tennis balls on court surfaces showed that the larger and standard tennis balls rebounded at approximately the same speed at 70% of impact speed on acrylic and 64% of impact speed on clay. Both sizes of ball bounced steeper off clay than on acrylic. It appeared that the larger ball rebounded steeper than the standard ball, although evidence for this was clouded by considerable scatter in the data. A computer trajectory program was used to analyse simulated first and second serves at nominally 53.3 ms−1 (120 mph) and 40 ms−1 (90 mph). It was found that a larger ball would increase travel time to the baseline by approximately 10 ms for a first serve and up to 16 ms for a second serve. This increase was found to be just less than half that between acrylic and clay for the same ball. Travel time is increased further if the ball is increased in diameter. It was concluded therefore that the introduction of a larger ball could slow the game of tennis for all strokes and increase the time available for the receiver to return the ball.

Solutions to the global challenge of physical inactivity have tended to focus on interventions at an individual level, when evidence shows that wider factors, including the social and physical environment, play a major part in influencing health-related behaviour. A multidisciplinary perspective is needed to rewrite the research agenda on physical activity if population-level public health benefits are to be demonstrated. This article explores the questions that this raises regarding the particular role that the UK National Health Service (NHS) plays in the system. The National Centre for Sport and Exercise Medicine in Sheffield is put forward as a case study to discuss some of the ways in which health systems can work in collaboration with other partners to develop environments and systems that promote active lives for patients and staff.

Background People with long-term health conditions face barriers to physical activity and community health interventions despite potential life-changing benefits for self-management of their condition and wellbeing. A weekly mass participation running, walking and volunteering event called parkrun launched a project called PROVE in 2016 to engage people living with long-term health conditions in England. Over the 3 year project, parkrun appointed volunteer Outreach Ambassadors with a specialist interest in the health condition they represented whose role was to ensure parkrun was welcoming, supportive and inclusive. This qualitative study aimed to understand the experience of the PROVE project for people with long-term health conditions. Methods Semi-structured interviews were conducted with 15 PROVE Outreach Ambassadors representing 13 different long-term health conditions in England. Interviews were recorded, transcribed verbatim and analysed using thematic analysis. Rigour and transparency were sought in addition to utilising independent researchers to offer alternative interpretations of the data. Results Data analysis resulted in 4 overarching themes and 13 subthemes. Outreach Ambassadors believed that parkrun was already supportive of people with long-term health conditions, but that the PROVE project enabled the support to be delivered in a more structured way across health conditions and locations. Outreach Ambassadors believed that the PROVE project had the potential to create a welcoming, safe space for people with long-term health conditions to participate as walkers, runners or volunteers. Success of the PROVE project was believed to be dependent on being realistic about the potential to bring about change, challenging people’s perceptions of parkrun and engaging with key stakeholders and advocacy groups. Challenges for parkrun were believed to be around communication, demonstrating impact and the project’s dependence on volunteers for delivery. Conclusions This is the first study of its kind to explore the public health potential of parkrun for people with long-term health conditions. parkrun’s PROVE project was regarded to be important for ensuring that people with long-term health conditions can engage in physical activity and volunteering in a safe and supportive environment. The findings have important implications for parkrun, policy makers and physical activity providers looking to deliver inclusive community physical activity opportunities.

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