[Scott Johnston]

It might be that this newfound ability to push to new intensities is what is causing the cramping.  It could be muscle fatigue that is causing it.  I’d try introducing some higher-intensity running to build more specific endurance.  If you’ve not been doing any intensity, start with strides only 10-20 sec at a fun, fast pace, not a full sprint.  I’d add hill sprints if you are not already doing them. Lastly, I would add tempo runs in Z3. Start with something like 2×10-15minutes with a 2-3 min walking recovery between.  Work the tempo run volume up to 60min over a could of months.  This will build a very specific type of muscular endurance that might help the cramps.

Scott