I’m going to make a wild guess that the changes in performance that interest/concern you are decreasing performance rather than increasing 🙂
Since you are a life long endurance athlete I can also assume you have a pretty good idea of what works for your training and have not made any big training mistakes, nor are you sick (although your injury may play a role but I can’t tell). That leaves a big elephant in the room that we need to talk about: AGE
Life long endurance athletes will notice a drop in performance much more starkly than those without that history. You know what it felt like to run fast or ski fast in your 20s and 30s. In contrast to that now you feel slow and it takes more effort than it used to to go slower.
How many World Cup Nordic skiers are competitive beyond their mid 30s? Only a tiny fraction. Why? All these athletes have good genes, good training practices, a long training history. Despite all this they start going slower and it is starkly evident because slowing 1-2% can mean the end of a career. There are always the next crop of 20 year olds nipping at their heels. There can be no better crucible for showing the effects of age on endurance performance than elite sports.
What causes this gross injustice?
MITOCHONDRIA are the cause. If you read our book you will recall that the mitochondria are tiny organelles within every cell except blood cells. They are the engines of life. In the muscle cells the mitochondria are where the aerobic metabolic process takes place. This process reassembles the ATP molecule so it can continue doing its job of fueling muscle contractions. The faster the ATP turn over the faster your speed. The faster the AEROBIC ATP turn over the faster your speed for longer. We call this endurance.
Here’s the rub (current theory of aging)
Mitochondria have rather short lives; on the order of a week. Mito also have their own unique DNA that come from your mom’s mitochondria. Each replication of Mito has a chance of including a genetic mutation that makes the Mito less functional. These mutations can then get passed on to the next generation. In 53 years you had over 2000 generations of mitochondria. That’s a lot of opportunity for these mutations to accumulate and make your Mito not the as functional as they were in your 20s. This degradation in aerobic power typically happens at about 10% per decade after 30. Endurance training can slow this a bit. But it can’t stop it.
A real life example:
Like you I have been a life long endurance athlete and I have really noticed this drop off. In my late 20s my maxVO2 was 80ml/kg/min, My aerobic threshold running pace was about 6min/mile. May anaerobic threshold running pace was about 5:15min/mile. At 65 my maxVO2 is 47 and my aerobic threshold running pace is about 10min/mile. All this despite a fairly high training load for much of these intervening years.
What to do?
Work on improving economy more than trying to improve aerobic power. Technical improvements can lead to even double digit gains in economy (cost to ski at a speed). You will never see double digit gains in aerobic power. Look for low hanging fruit like this.
Look for other sports you enjoy that do not demand such high aerobic power. Longer, slower running and cycling, mountaineering. Speed (even with endurance) is a young person’s game. That’s the reason for age groups in masters sports.