Hi. I’ve been hiking for years (I’m 67) & currently go 4-8 mi on Med-Hard trails. In the last 6 months towards the latter part of the hike, typically going downhill, the lower part of my left quad (closer to the knee) starts burning/hurting. It also randomly hurts when I’m not hiking. Physiotherapist says it’s muscle fatigue b/c I’m not resting enough in between hikes, but it’s only recently started.