Sub40 10k training (General inquiry)

[MitchelC]

Okay , will be incorporating the 3 x 1600m next sub40 cycle. However, as I'm already more than 3 months into the program (progressing from the sub55 program to the sub40 and all the programs in-between), that'd be later on. I'll take the off-period and build-up as soon as im done with this sub40 cycle as recommended. My calves are feeling heavy lately, i hope the off-period takes care of it. Are there specific paces for the sessions in those programs or should i focus more on monitoring my heart rate during these runs?

Thanks in advance