What has surprised me is just how quickly I have lost fitness over the past 5 weeks since Jedburgh, I have noticed that I am getting more muscle fatigue and even have had Delayed Onset Muscle Soreness (DOMS) in the days after even modest runs. My heart rate for a given pace is also higher, and the calories per mile reported by my HR monitor for each runs has risen steadily through this period.
The average effective efficiencies (normalized for hills and distance) of my runs tell the sorry tale of the de-training I've seen - I averaged 82 calorie/mile for October, 87 for November and 90 for the two runs I've done so far this December. That's a 10% reduction in efficiency in just five weeks and I didn't even stop running completely, just reduced by mileage from 45 miles/week to 13 miles/week.
I am quite perplexed by the extent of de-training I've seen, is this normal, is that what others see as well? My scientific inclination is also drawn to finding out in what ways my body has changed during this period of lighter mileage and de-training.
My own thoughts are really just a jumble of possibilities:
- Mitochondria populations in my muscles has decreased through lack of need for them all
- Muscles have atrophied through lack of stimulus
- Muscles have begun rebuilding after a big month of running and the newly configured muscles need to developed aerobically before I see the benefit
- My aerobic fast twitch muscle fibres due lack of aerobic exercise have reverted to being more like fast twitch fibres rather than aerobic fibres
- Weight changes - I might have put on roughly 1% in weight, pretty negligible but I guess it'll account for a tiny bit of the loss of efficiency
- Blood volume has reduced
- Loss of adaptations for heat loss
I suspect the last two might well be the most significant factors, but I've never read a paper or articles discussing de-training so it's all just speculation. One thing I have noticed is that calories reported in the first mile of running has only gone up around 3% but the average has gone up 10% showing that I have much more significant HR drift than I did prior to taking it easy. This makes me suspect that my ability to handle the accumulation of heat has been significantly impaired as I find it difficult to recoil my muscle fibres and populations of Mitochrondia have been slashed enough to explain a 10% loss in efficiency.
If you have insights please leave a comment as I'd love to know what others think might be happening when we de-train. As I get back into training it'll be interesting to see how quickly my efficiency returns, fingers crossed it won't be months before I get back to near where I was back in October.