Been off the bike, and off running for a few months with a niggling knee injury.

Need something to focus my return to fitness so fancy a Duathlon in the New Year.

I need a plan to follow to get me started as otherwise I’ll just randomly run/ ride which will I’m sure build up my fitness but perhaps isn’t the most structured route.

Need to start slowly so as not to ruin my knee again.

Assuming the knee is 100% healed, the first thing you need to do is find an event you fancy and mark that as your target. Open ended training plans arent really a thing.

Once you’ve got the event and date, you can analyse the requirements and work backwards aiming to start adding intensity around 16-20 weeks before your event. Up until that point just stick to very light intensity (should be able to hold a conversation no problem), gradually building the duration. It might be a bit dull no start with, but avoiding injury and excess fatigue will allow you to train more regularly and consistently.

Assuming you are fairly time constrained, I’d suggest getting a triathlon training plan and omitting the swimming, and either using the gaps for recovery (probably most sensible) or more brick sessions.

If you have or can build some fitness, getting used to running off the bike is very handy. It feels pretty odd. I did circuits of running/riding repeating about 3-4 sets of 20 mins run/20 mins ride.

I also went for a shot run after nearly every ride.

I followed a combination of ‘Time Crunched Cyclist’ and ‘Run Less, Run Faster’ with some added brick session in there. It was really hard to actually train both disciplines, but I was happy with the results. Got me as fit as I’ve ever been.