A couple of weeks ago Cardio Mark ran the Dublin marathon in a very creditable time of under four hours. I’m impressed. When I used to run regularly, I once or twice managed half marathon distance and I never finished wishing I’d done twice as much. Completing a marathon requires months of training and resolute determination.
A couple of days before Mark’s marathon I went for a bike ride. I had the day to myself so cycled over to Dunkery Beacon – the highest point in South West England and the region’s signature bike climb. It’s not the longest climb and not the absolute steepest but its combination of length and severity is nonetheless testing. The rest of my ride was not without interest, extending to 93 miles with 7.5k feet of ascent and taking me around 6:40 with a couple of stops. It was equivalent in difficulty to a reasonably stiff domestic sportive. Fit cyclists do not need to train for such sportives – they’re easy enough that you can just rock up and do them.
Out of curiosity, I compared Mark’s marathon with my bike ride using Crickles Activity Charts. Charting a histogram of our heart rates gives this, with Mark’s histogram in pink lying over mine in blue:
On the morning of my ride my resting heart rate was 46 bpm, which is marginally above Mark’s (44 bpm). Crickles shows our prevailing Lactate Threshold Heart Rates to be similar too (mine was 162 bpm and Mark’s was 157 bpm). The chart thus shows that not only did Mark record far fewer beats during his marathon than I did during my ride, he also managed his effort much more prudently with the entirety of his cardiac activity well under his LTHR in contrast to my ride in which I was well over my LTHR for a significant portion of the time. It is graphically evident that my ride placed a much greater load on my heart than Mark’s marathon placed on his. This is reflected in our respective Cardiac Stress Scores – 570 for me and 300 for Mark. (Reflecting on this, I realised that the Crickles CSS methodology does not fully capture the restorative effect of my two coffee stops. I calculated the effect of these and it decreases my CSS by 17 points – just under 3%, so not a significant amount.)
By contrast, the differences in our Suffer Scores on Strava was much narrower – Mark’s Suffer Score was 255 compared to my 299. This confirms my previous finding that the Strava Suffer Score is not a good measure of cardiac stress.
There is an important point here for cyclists. Mark’s marathon felt hard and was hard because of the intense amount of corporeal stress that running for four hours places on the body. Skeletal muscle and the bones, ligaments and tendons to which it is attached, can feel the pain. There is also that intangible of “the wall” as it is harder to refuel adequately when running. Cycling inflicts far less strain on skeletal muscle and doesn’t pound our body in the same way. Unlike our peripheral muscles, our exercising heart does not feel pain and we thus have no direct real-time index of the stress to which we subject it. So long as we ride within our strength limits and eat and drink well, the wall of bodily pain that marathon runners have to run through has no analogy in cycling and there is nothing to indicate how much cardiac stress we’re accruing. The only direct evidence that our sportive was equivalent in cardiac stress to two marathons might be a histogram or a CSS number. An appreciation of this might spur us to think more seriously about the amount of recovery we need to build into our exercise schedule.