AM - from BHS - with Bill L, Chris M and Sheryl W - 2hrs+ walk/run...used 30R/30W pattern...heart rate stayed mostly in 105-125bpm range...a lot in mid-teens. Since yesterday was close to 3 hours, going over 2 hours today...even if it was a mix of walking and running...was something new and experimental. All I can say is that my legs were really tired and heavy...heavy like lead. Based on heart rate, the stress should be OK...but I'll have to see how I feel over the next few days. Not sure I would recommend this.