Response: Your reasoning is sound; neuromuscular development is a key component of running success. i.e. If you never run at race pace it becomes more challenging to run at this race pace regardless of your metabolic capacity.
However, you also hit the nail right on the head when you stated that you will be careful when downhill running because of the increased eccentric load. This brings us to the decisive point: Will the run that you compete in at sea level involve a much higher eccentric load? No, it will demand only a slightly higher eccentric load when going from a 6:55min/mile pace (the pace that might equal your ½ Marathon pace at altitude) to your 6:45min/mile goal ½ Marathon pace at sea level. …almost undetectable; making the ‘cost to benefit value’ very poor.
Now how do we build the capacity to handle the demands of faster running at Sea Level? From here we should look into the most important factors of running speed?
- The first and most important factor is power at foot strike (the ground reaction force ‘or work’ produced at foot strike / over time). More power results in an increased distance between foot strikes (some call it stride length but I don’t like to use the word ‘stride’ because sometimes runners think they need to reach with their legs and ‘stride out’ and this is simply not the case). I believe that you would agree that when running downhill you do not need to generate as much power in order to travel as far between foot strikes; therefore you are not training one of the fundamental components of faster running.
- The second and smaller factor of run speed is cadence. Our cadence might increase 2-4 revolutions per minute as we increase from our marathon to our 5K pace. Something we might be able to accomplish if running downhill but it really takes a concerted and it almost feels unnatural because the ground is essentially falling away from your foot strike.
- Run at speeds equal to that of your Sea Level race but for shorter periods than you might typically during Seal Level intervals. For instance if you are doing a workout designed for a 5K at elevation you would shorten the intervals by 20-30% and perform them at your Sea Level pace yet keep your rest the same as if you would for longer intervals (so the rest would end up being 20-30% longer than you might use if you were at Sea Level). This is a pretty easy pace to find for a ½ Marathon workout because you are using an intensity just slower than 10K pace.
- Run up hill. Yes, the exact opposite of the downhill running idea. Running up hill has proven to be one of the best ways to improve foot strike power. The basic idea is that you need to apply more power at foot strike to travel both horizontally and vertically. At the same time the ground meets your foot sooner so you can run naturally with a higher cadence, a cadence that may be equal to a faster run at sea level.
Final note: Training for a downhill event. A cautious progression of downhill running would be very helpful to develop the ability to handle the intense stress of a downhill race or a race with lots of downhill.
I would be in full support of having you do an uphill run that progresses from 2-miles up to 5-miles over a few weeks before your ½ Marathon. The ideal situation would be to have you get picked up on top by your support crew – or you could get fancy and drive up, coast down on your bike – lock your bike up and the run up.
Uphill running in addition to completing the strong aerobic runs where run at Seal Level ½ pace for around 20-minutes will make up a great training progression!
Great question! I will most likely turn this discourse into a blog post on my website.