As far as intervals go, I never do much speed work til I get 25-30 hrs in the boat. Since my primary emphasis in the spring is preparing for the 70 miler, I spend time at a lower pace for much of the early spring.
When I do intervals, they are of 3 primary types.
On our creek, we have a dozen designated sprint sections on the upstream leg that start at 30 seconds early in the spring and evolve to 2 minutes each with roughly the same amount of rest in between. They are done in shallow water, upstream and often involve a corner.
The other type we do is later and usually on a canal or deep water and after a warmup is a set of eight 2-3 minute all out sprints followed by the balance of the 5 minutes at a recovery cruise for a total of 40 minutes of hard paddling and recovery.
The third type is 20 minute race pace time trial efforts in 1-3 ft water. We warm up for 20 minutes, do a 20 minute piece, rest 5 minutes, repeat and then cool down.
By Marc Gillespie, February 2009