A week later, I have had time to look back over the Robin Hood Half Marathon, and reflect on the recording from my watch and heart rate monitor. I had pressed the event marker button at 1, 4,7 and 10 miles so I had estimates of my pace and heart rate in each three mile segment after the initial mile. As expected from the effort I put into the final few Km, my fastest segment was from 10 miles to 13.1. However despite a substantial increase in effort, my pace of 4:46 min/Km in that final 3.1 miles was only marginally higher than the average of 4:51 for the entire event. I expended a lot of effort for a modest gain in speed. Despite the effort, my heart rate only rose moderately, to an average of 138 over the final 3.1 miles compared with 133 for the entire event. Thus, the cardiac cost was 659 beats/Km in the final 5 Km compared to an average of 646 for the whole event. This reflects a small loss of efficiency, but that is not too bad, as efficiency usually decreases when one is tired (and heart rate also rises as body temperature rises). However the noteworthy point is that despite trying to recruit every available leg muscle fibre, my heart rate was still substantially lower than I would expect for the final stages of a race. It appears that I just do not have the muscle power to maximise the use of my cardiac output at present.
My struggle to recruit my leg muscles is also clear in the photos. At halfway, my hams and calf muscles were quite tight but I was fairly confident that they would get me to the finish, so I decided it was time to increase the effort. By about 12 Km, the effort shows on my face but at that stage, my legs were unwilling to go any faster. With 3 Km to run, effort was now approaching maximal but the increase in pace was modest.
In the final sprint, the tense neck yet floppy wrist suggest that I was not recruiting muscles very efficiently. However, the facial expression might have been just right for Ewen’s fantasy Hollywood blockbuster in which an elderly professor with cronky legs pits his failing strength against the Vice Chancellor’s pretty PA in a sprint to the finish. The outcome will determine whether a legacy to the University will be spent on a new limo for the VC or on refurbishing equipment desperately needed for life-saving medical research in the prof’s lab. But in the more prosaic real world, I was in fact fairly pleased with the way I had run the race, and think I got about as much out of my legs as they were fit to give.
For two days after the event I had moderately severe generalised DOMS but fortunately only a scarcely perceptible localised discomfort in my left calf, so I had not done any significant local damage in my sprint finish. Towards the end of the week, I did a session of Peter Magill’s skipping drills and the only noticeable muscle issue was mild tightening of my hamstrings in the final few metres of the skip and kick drill. This resolved when I slackened the vigour of the kick.
So overall, the HR data and other evidence confirmed what I already knew from my experience on the day. I need to strengthen my legs, and will start on the free weight program in about two weeks, after I return from a conference in Switzerland, and a few days walking in the Bernese Oberland. I will assess gains in strength using the hopping test but the more meaningful measure will probably be my time for a 5K, by the end of the year.
At the beginning of the current half-marathon campaign, I was unsure that I could even achieve a time of 25 min for a 5K and was pleased when I did a 5K parkrun in 24:45, with an average HR of 143. So my time of 23:50 with a somewhat lower heart rate for the final 5Km in the half marathon at least demonstrates that my aerobic fitness and endurance did improve substantially during the campaign, even if the improvement in power was rather modest. I doubt that I will ever run a 5K in less than 20 minutes again, but I would at least like to get down to around 22 min. Then I should aim for another half marathon in the spring and perhaps a full marathon in the autumn.