Hello, I am an age grouper (45-50) and I participate regularly in Ironman 70.3 races. I can see that I am not doing any progress over the past 2 years despite high training volumes and a structured plan. As a matter of fact, I can see that my performance levels are decreasing. Any thoughts on what could be the reason(s)?
It depends what you mean by high volume and structured plan, and how regular you race 70.3´s. You are not at the age that I´d expect to see an age-related decline so you still have plenty of time to change it around!
If your performance is declining then it may well be that the high volume is fine but the intensity is not correct and the structure of the plan, and consistency, has not accounted for the volume / intensity.
As a key priority, you must take into account that triathlon is an aerobic sport, even a sprint triathlon, and so you must train accordingly; ie most of your training MUST be aerobic, or EASY. Go too hard and although you feel like you are working well, you´re not actually doing yourself very much good.
This blog we put out a while ago might help: https://mastersoftri.com/one-speed-syndrome/
The other part to consider is whether you are actually training correctly in terms of building the aerobic capacity (above) and the strength you need to perform well. Strength is a key component to being able to build muscular endurance - your ability to keep going at a given pace. This does not mean going to the gym to lift weights and core training (you can if you have the time) but doing strength specific swim, bike and run training (aerobically).
Here is another blog that might help with this: https://mastersoftri.com/strength-sessions-for-triathletes/
How you develop a strucutred plan and then how you mix the sessions if very important so that you get the benefit of each session without being able to recover and then do the next session.
Hope this help - there are also other blogs on our site you might find interesting / relevant to your question