Responses of male recreational runners during outdoor running in three shoes: Quantitative and qualitative studies

Abstract

The introduction of advanced footwear technologies (AFT) in running shoes has sparked debate due to their significant impact on performance. However, there is a lack of research on how runners perceive them, especially compared to their own shoes and minimal shoes, which are also used in racing. Most research surrounding shoes with AFT is conducted in a laboratory environment, despite being designed for outdoor running. Therefore, this study aimed to provide a quantitative (Chapter 2) and qualitative (Chapter 3) assessment of runners running outdoors wearing three different shoes: Nike Vaporfly 4% (VP4), the original shoe with AFT; Saucony Endorphin Racer 2, a minimalist lightweight racing flat (FLAT); and runners’ habitual running shoes (OWN). The thesis aimed to compare biomechanical and subjective measures between shoes and explore possible correlations between comfort measures and biomechanical and subjective measures. Additionally, the thesis aimed to provide qualitative insights into shoe comfort and preferences of recreational runners wearing novel footwear. Chapter One briefly reviews the evolution of running shoes and research investigating the design, performance, comfort, and injury of minimalist shoes and shoes with AFT. Minimalist shoes are designed to mimic barefoot running and have been shown to improve running economy due to being lightweight. These shoes are perceived as potentially preventing injuries for being “closer to nature”. Shoes with AFT typically contain a thick midsole of polyamide block elastomer foam and curved stiff plate. Shoes with AFT are reported to improve running economy; however, individual responses vary, especially in recreational runners. Comfort is a critical factor for runners when purchasing shoes and is proposed to enhance performance and minimise injury risk. However, comfort is multifaceted, and individuals value different factors during footwear selection. Chapter Two is a quantitative study. In a cross-sectional study, 18 male recreational runners (age: 31.2 ± 10.5 y) ran three 1.5 km trials outdoors in OWN first, followed by FLAT and VP4 in random order. The first 1.1 km was run at a comfortable self-selected pace, and the final 400 m at a perceived 5 km race pace with a 30-second rest between speeds and 12-minutes rest between shoe conditions. Biomechanical measures were collected approximately 700 m into the 1.1 km run and 300 m into the 400 m run. Foot-strike angles were smaller in FLAT at both speeds (small to large effect size, ES) compared to both other shoes. The propulsion phase was shorter in VP4 (moderate to large ES) than in the other shoes. FLAT was ranked as being the least comfortable at the slower speed and perceived as the most likely to cause injury. OWN was ranked as the most comfortable at the slower speed and perceived as the shoe with the lowest injury risk. Comfort measures were more strongly correlated with subjective than biomechanical measures, illustrating the subjective nature of comfort. Chapter Three is a qualitative study. The 18 male recreational runners were interviewed before and after running the 1.5 km trials in the three shoes (OWN, FLAT, and VP4). From the interviews, four main themes emerged with regards to comfort, performance, and injury risk: familiarity, cushioning, support, and ease of running. VP4 had the highest number of participants who most favoured it for performance as well as least favoured it for performance, exhibiting the divergent perceptions of runners with regards to the shoe (i.e., runners either liked or disliked them). The FLAT was described as light and quick, while the VP4 was described as bouncy and quick. Regarding cushioning, participants perceived OWN as balanced and reflecting a middle ground between the two extreme novel shoes. OWN provided a sense of familiarity and reassurance to runners regarding injury risk, while the lack of cushioning in the FLAT was perceived to increase injury risk. Overall, the interviews revealed the perceived link between comfort and performance in recreational runners and the variability in runners' footwear preferences. The results of this thesis provide a more holistic understanding of running footwear comfort and performance in recreational runners. Comfort is a critical factor for shoe selection in runners, however, there is little association between comfort and biomechanics. Additionally, runners appear more likely to purchase shoes with AFT than minimalist possibly due to these being more similar to traditional running shoes and having more cushioning. Combining qualitative and quantitative analysis enables the extraction of a meaningful and nuanced interpretation from data. Furthermore, the valuable insights attained can help inform future shoe design and enhance the overall running experience for recreational runners.