Changes in gait characteristics are found when exertional heat stress is experienced during prolonged load carriage. As heat stress increased, step width decreased while percent crossover steps increased. Reduced stance time variability, step width variability, and percent crossover step were observed. These are frontal plane gait parameters for the most part.
Think about these things during your long summer run or as you go deeper into those last miles of your long run. Simple muscular fatigue in the frontal plane hip-pelvis stabilizers are going to render the same results. This is quite possibly why many problems and injuries crop up in the latter miles of your run.
2016 Jan;43:17-23. doi: 10.1016/j.gaitpost.2015.10.010. Epub 2015 Oct 23.Using gait parameters to detect fatigue and responses to ice slurry during prolonged load carriage. Tay CS, Lee JK, Teo YS, Q Z Foo PTan PM, Kong PW