| Even Pace, Uneven Effort |
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 The Rochester Marathon for Example
It is well known that something close to an even pace results in the fastest time for distance races. It is possible that a slightly negative split (second half faster than first half) is the optimal approach to the marathon. Both of the current men's and women's marathon world records were set with negative splits. What doesn't get talked about as much is the simple fact that, while the pace throughout the race may be even, the effort required to maintain that pace increases dramatically over the race. As it happens, I managed to run a slightly negative split in finishing the Rochester Marathon in 4:14:40 this year. My average pace for the 26 miles 385 yards was 9:43 and the chart below shows my average pace for each two mile split. As you can see, I started slightly faster and then from miles 7 to 14 was slightly slower than 9:43. After 14 miles, I realized I could get a Boston Qualifying time (4:15:59 or better) if I picked it up slightly. So I went for it. After mile 22 I cut out the short walks I was taking every two miles, which helped make the miles from 23 to 26 faster and got me under 4:15. The big blip up to 11 minute pace over the last 385 yards was due to sharp pains in my left calf. Had those pains happened even half a mile sooner I would have lost the Boston Qualifying time. The chart also shows two indicators of the increasing stress that even pacing imposes. Notice how my average heart rate increased over the run... going above 150 beats per minute after the 8th mile, above 160 after the 14th mile, above 170 after the 22nd mile and continuing to climb to the finish.  And, while my heart rate had to climb steadily to maintain the even pace, my breathing rate also had to increase. It is well known that most (perhaps all) runners synchronize their breathing with their running stride (see my May 2006 Eclectic Runner posting on the GRTC website). The typical pattern is to exhale sharply on a foot plant and then inhale more slowly over the following several strides before again exhaling sharply on a plant of the same foot, typically one's dominant foot. After a mile or so into the marathon, I settled into a comfortable pace and was exhaling on every third left foot plant. During the early miles it was possible to have brief conversations with friends in the race. That breathing rate was adequate until the hills in Perinton pushed me into shifting to exhaling on every second left foot plant. This transition happened at about the time my heart rate went over 150 beats per minute. Exhaling on every second foot plant provided enough oxygen for economical running until my heart rate starts climbing above my anaerobic threshold. After the 18 mile mark, I could no longer delay the switch to exhaling on every left foot plant and started what had to be a final push to the finish. At the time I knew I was taking a risk as I usually hope to delay that switch and the final push in a marathon until I get to at least 20 miles. The effort to maintain pace was pretty grim over the last couple of miles until being punctuated by the dramatic calf pains in the final 385 yards. Generalizing from this one race by one runner... an optimal even pace takes a very uneven effort. Heart rate will creep up gradually to near maximum by the end of the race. Breathing rate will shift several times, going from a rate where brief conversations are possible to really huffing and puffing at the end. |