You have to change your body if you want to get stronger, more flexible and have amazing endurance
Your body will only let you improve one thing at a time
Whilst you are doing this, you try to maintain previous improvements in other areas
For SUP Racing this means that you will be working mostly on improving Endurance or Speed but not both at the same time
Blocks, training patterns and priorities
It is a minefield of contradicting advice out there but there are a few things that most agree on:
Transform one thing at a time whilst maintaining prior gains in other areas
Know what type of race you are training towards and transform your body appropriately
SUP is mostly an aerobics sport BUT Aerobic fitness wont make you that fast.
You have to have a great aerobic base but add some speed work in at strategic points to get you faster.
Training in a group will improve your results BUT you need to find a group that will push you just enough to hit that improvement sweet-spot. They also have to be following similar training blocks as you.
Split your training into 3 or 4 week blocks, where you concentrate on improving either Aerobic Endurance or Speed.
Controversial opinion time
Most people suggest leaving speed work until the last block or two before races.
This makes sense for serious trained athletes
If you are just getting started then you are probably not stunningly fast.
Aerobic training will get you through races BUT you might finish them all in last place.
For new racers it is worth doing some early season speed work, so that your follow on aerobic work, is done at a faster pace.
Why do early season speed work
If you have never raced and paddle naturally at 5km/h then aerobic training might get you to being a great 5.5km/h paddler.
Efficiency will give you a small speed boost but nothing else
You are effectively training to become a great 5.5kmh endurance paddler
If you have a bit of Aerobic base and then do some early season speed-work, you might raise your top end pace to 6.5 or 7km/h
After this you might be able to aerobically train at 6km/h
You are now training to become a great 6km/h endurance paddler
Mix this in with some speed-work later in the cycle and you might become a 6.5km/h long distance racer.
Last thoughts
SUP Fitness and physical transformations take a lot of time to pay dividends. You should really be thinking of a Three year plan with Yearly Goals along the way