How much do performances vary before it raises a red flag that something may be wrong?
Naturally, you cannot expect to match your personal record every time out especially if it is paced perfectly and you have close competition near the end. My standard “margin of error” is no more than 5% slower at every distance from the half marathon down given similar training, topography and weather conditions.
A runner with a 5K PR of 20:00 should average about 20:15 with an “off day” being in the 20:45 range. Given that the above 3 ingredients remain constant, a sub-21 should happen every time barring sickness, injury or starting out “stupid fast”.
A runner with a 1:40:00 half marathon PR should average between 1:41-1:42 and still be able to break 1:45 on an “off day.” The marathon is an entirely different animal so more variability is to be expected.
Now, let’s put that 5% variability into a world class perspective. Imagine if one of the favorites for a gold medal in the 10,000 meters gets lapped by the eventual winner. It would certainly be a surprise to the viewers but if the athlete is only 4% off their peak (1 lap out of 25), that’s exactly what will happen.
Usain Bolt came into the London Olympics in 2012 as the world record holder at 9.58 seconds. Suppose that he had an “off day” the morning of the semi-finals and was 5% off his game. He would have clocked a 10.06 and failed to qualify for the final. That would have been considered the choke of the century if the greatest of all time was eliminated in the semi-finals. A 5% decline represents the difference between a world record and the fringe of world class.
As for me, even with my diminished fitness level over the last 12 months, I have still managed to clock a time of 20:42 for 3 miles on 2 occasions. I ought to average about 21-flat and be no worse than 21:45 on a bad day. Instead, I average just under 24 minutes and have days in which I cannot break 9 minutes for 1 Mile running all out. It should be obvious that something is seriously wrong and if you read this blog with any regularity or see me training, you know it.
I know there are many others out there in their late 30s or early 40s that have experienced a sudden decline in performance. I cannot emphasize enough that your age is not the problem. Do not give up. From age 35-40, performance is expected to decline by about 0.5% per year. That’s roughly 2 seconds per mile over the course of 12 months. It is a headwind that can be overcome with an improved fitness level especially at the longer distances. I know several runners who remained strong competitors well into their 50s. Meb Keflezghi qualified for the U.S. Olympic team in the marathon just before turning 41. I also saw a highlight video of an old Comrades Marathon in which 7 of the top 10 finishers were over 35 and 4 were 40+.