1The steep pitch
From 32.1 km to 32.2 km
0.1 km · +12.1% average · 9.5 km/h · 148 bpm, peaking at 156
That steep pitch out of Lower Winchendon kicked your heart rate up to tempo even though you were grinding through it at 10 km/h, which suggests you were working harder than the gradient alone required—worth a look at whether you had the gearing right.