I got thinking this past weekend while doing some conversions to relate a hike I did to bike and run volume. Typically for hikes, I have athletes assume 35 percent of it counts toward running, and 35 percent toward biking. Based on that, if you had a 2 hour ride and a 2 hour run planned on a particular day, a 6 hour hike would take care of both those workouts.
People ask me how I come up with these conversion factors……its actually quite a simple process that I use based on approximate cardiac output. Let’s say your training HR zone on the bike is 129 (middle of zone) and your run training HR zone is 139, your average HR for the 4 hour workout day described above would be 134 (2 hours at 129 and 2 hours at 139). Let’s also say your resting HR was 45 bpm. Based on that, your heart will beat 89 times each minute more than that required to stay alive at rest for a four hour workout. This is a total of 89 bpm x 240 minute’s equals 21,360 beats extra just because you went out for a short ride and long run. If we look at the hike now, for the same person, a solid paced hike would result in an average HR of about 105 bpm or 60 bpm more than that required to stay alive at rest. Over a 6 hour hike, this results in 360 x 60 bpm equals 21,600 beats. As you can see, from a total cardiac output standpoint, 2 hours of biking and 2 hours of running at an aerobic “zone 1” pace is approximately equal to a 6 hour hike. Armed with this information, you can quite easily figure out what a particular hike is worth in terms of bike/run volume that may have a lower HR like 92 bpm. Of course is quite subjective to figure out how much of the volume should go to bike versus run, but in my opinion, a 50/50 split is appropriate given the specificity of hiking to both biking and running. It should be noted that this approach only addresses the cardiac piece of the equation. There is a significant peripheral impact on soft tissue during the descents when hiking which is an additional stress (beyond most damage done when running) not accounted for in the total cardiac output method above.
After playing with this method a bit, some interesting numbers fall out. For most top level traithletes, a 25 hour training week is routine. How many times do you force your heart to beat though for that volume? Well, again assuming an aerobic HR of about 134 on average and a resting of 45 bpm we get:
In a week: 133,500 beats
In a year for a top level triathlete training 1,000 year-hours: 5,340,000 beats
What it takes to reach your potential at endurance sports is commonly thought to be about 10,000 hours: an astounding 53,400,000 beats!
It’s just amazing what we ask of the heart and how reliable it is.
All of this thought while looking for a can of beets to put over my salad after a 6 hour hike in NH yesterday……..