Author(s): HUNTER, B., MUNIZ-PUMARES, D., Institution: UNIVERSITY OF HERTFORDSHIRE, Country: UNITED KINGDOM, Abstract-ID: 550

INTRODUCTION:
Marathon performance is underpinned by three physiological pillars: V̇O2max, running economy, and the fractional utilization of V̇O2max (1), usually measured in a “fresh” state with limited fatigue. However, these factors are subject to deterioration during prolonged exercise. The ability to resist this deterioration is termed durability (2). Further to exhibiting inter-individual variability, greater durability has been associated with faster marathon times (3). Biomechanical parameters also alter during prolonged running (4). However, it is unclear whether changes to biomechanical parameters during running are affected by, or affect, durability. Therefore, the aim of this study was to examine whether changes to biomechanical parameters are dependent on durability characteristics. It was hypothesised that runners with lower durability would exhibit larger changes to biomechanical parameters during the marathon.
METHODS:
Fifty-seven marathon runners (finish time: 232.4±49.7 mins) were recruited and submitted race data collected using their own footworn accelerometer (Stryd Inc) and heart rate (HR) recording device (e.g., smart watch or HR belt). Biomechanical parameters including stiffness, duty factor, cadence, and running speed, were extracted using a custom MATLAB script and separated into eight 5 km bins. Decoupling, a measure of durability (3), was defined as the ratio between HR and grade-adjusted running speed. The decoupling observed in the last 5 km segment of the race (35–40 km) was used to determine the overall magnitude of the decoupling, expressed relative to the 5–10 km segment, and were grouped into high, moderate, and low decoupling groups. A two-way repeated measures ANOVA was performed to detect differences in biomechanical parameters (segment x group), and a repeated measures ANOVA was used to test for group differences in finishing time and decoupling magnitude.
RESULTS:
Significant differences were evident between groups in decoupling magnitude (p<0.001), with moderate (1.14±0.04) and high (1.41±0.21) groups exhibiting greater decoupling than low (1.04± 0.05). No significant differences were observed in finishing time (low: 224.0±43.8 mins; moderate: 223.5±51.3 mins; high: 249.7±52.2 mins). Interaction effects were evident in cadence, duty factor, running speed, and stiffness (p<0.001). Greater decreases in stiffness, cadence and running speed, but greater increases in duty factor, were evident towards the end of the marathon in the high decoupling group when compared to other groups.
CONCLUSION:
Athletes with lower decoupling, i.e., greater durability, appear to preserve “fresh” biomechanical parameters during a marathon better than those with higher decoupling, i.e., lower durability. It is not clear whether lower durability is a cause or consequence of these changes.

1. 10.1113/jphysiol.2007.143834; 2. 10.1007/s40279-021-01459-0; 3. 10.1007/s40279-022-01680-5; 4. 10.1016/j.jbiomech.2016.08.032